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May.02.2022

Diabetic Autonomic Neuropathy

Synopsis

Key Points

  • Diabetic autonomic neuropathy is dysfunction of the autonomic nervous system (parasympathetic, sympathetic, or both) in a patient with diabetes (type 1 or type 2) in whom other causes of neuropathy have been excluded r1
  • Both sympathetic and parasympathetic pathways may be affected (though not necessarily proportionately), resulting in inadequate and/or imbalanced autonomic control of heart rate, cardiac contractility, vasomotor function, gastrointestinal and genitourinary smooth muscle contractility, sweat gland secretion, and pupillary constriction r2
  • Symptoms vary depending on systems affected, but they may include lightheadedness on standing up or after eating; nausea; early satiety; abdominal pain or bloating; constipation and/or diarrhea; urinary hesitancy, frequency, urgency, incontinence, or retention; erectile dysfunction; and hyper- or hypohidrosis
  • Diagnostic testing depends on system involved
    • Cardiovascular autonomic reflex tests are the gold standard for diagnosing cardiovascular autonomic neuropathy; they consist of recording heart rate variability in response to maneuvers designed to elicit a sympathetic or parasympathetic response (eg, paced breathing, Valsalva maneuver) and measuring orthostatic changes in heart rate and blood pressure r3
    • Gastroparesis may be diagnosed by scintigraphic studies showing delayed gastric emptying r4
    • Bladder dysfunction may be evaluated by measurement of postvoid residual and urodynamic testing to determine whether bladder is hypotonic or overactive r5
    • Initial workup for erectile dysfunction involves distinction of psychogenic from organic causes
  • Treatment involves optimizing glycemic control and weight loss if indicated; otherwise management is symptom focused r4r6
    • Symptoms of orthostatic hypotension may be minimized by physiologic maneuvers; fludrocortisone, midodrine, and droxidopa can be used if conservative measures do not relieve symptoms adequately r1r7
    • Gastroparesis can be treated with metoclopramide or erythromycin, although tachyphylaxis limits efficacy; electrical stimulation is an alternative r8r9
    • Neurogenic (hypotonic) bladder may be treated with scheduled or assisted urination or intermittent catheterization r7
    • Symptoms due to hyperactive bladder (ie, frequency, urgency, incontinence) may respond to bladder training and Kegel exercises; if not, antimuscarinic agents and/or mirabegron may be effective r10r11r12
    • Erectile dysfunction that is organic in origin may respond to phosphodiesterase-5 inhibitors or prostaglandin E₁; these should be prescribed only after cardiovascular status has been evaluated and risk is deemed low r6r13
  • Prevention of diabetic autonomic neuropathy is primarily through optimizing glycemic control; people with type 2 diabetes benefit from additional behavioral and pharmacologic interventions aimed at other cardiovascular risk factors r1

Terminology

Clinical Clarification

  • Diabetic autonomic neuropathy is dysfunction of the autonomic nervous system (parasympathetic, sympathetic, or both) in a patient with diabetes (type 1 or type 2) in whom other causes of neuropathy have been excluded r1
  • May affect cardiovascular, gastrointestinal, urogenital, and sudomotor systems; pupillary reflexes; and awareness of hypoglycemia r1
  • May or may not be associated with other forms of diabetic neuropathy (eg, distal symmetrical polyneuropathy, mononeuropathy, radiculoplexopathy) r1
  • May occur as part of syndrome of treatment-induced neuropathy along with acute or subacute painful peripheral sensory neuropathy r14
    • Complication of aggressive glycemic control, particularly with hemoglobin A1C reduction of 1% or more per month

Classification

  • Diabetic autonomic neuropathy falls within the following larger classification of diabetic neuropathies: r1r15
    • Diffuse neuropathy
      • Diffuse symmetrical polyneuropathy
        • Small fiber predominant
        • Large fiber predominant
        • Mixed small and large fiber
      • Autonomic r16
        • Cardiovascular
          • Reduced heart rate variability
          • Resting tachycardia
          • Orthostatic hypotension
          • Sudden death
        • Gastrointestinal
          • Gastroparesis
          • Enteropathy
          • Colonic hypomotility
        • Urogenital
          • Cystopathy
          • Erectile dysfunction
          • Female sexual dysfunction
        • Sudomotor dysfunction
          • Distal or generalized hypohidrosis/anhidrosis
          • Gustatory hidrosis
        • Abnormal pupillary function
        • Hypoglycemia unawareness
      • Mononeuropathy
        • Isolated cranial or peripheral nerve
        • Mononeuropathy multiplex
      • Radiculopathy or polyradiculopathy
        • Radiculoplexus neuropathy
        • Thoracoabdominal neuropathy

Diagnosis

Clinical Presentation

History

  • Symptoms may be present when diabetes is diagnosed or may occur during the course r6
    • Likelihood of autonomic neuropathy increases with disease duration
  • Patients may have symptoms related to 1 system or several
    • Cardiovascular
      • Orthostatic symptoms: lightheadedness, weakness, head and neck discomfort, blurred vision, tunnel vision or syncope after arising from a sitting or supine position, or after prolonged standing; a history of falls may be elicited c1c2c3c4c5c6c7
        • Symptomatic episodes may occur more frequently in the morning, after large meals, or with fever r3
      • Poor exercise tolerance c8
    • Gastrointestinal r17
      • Gastroparesis: early satiety, abdominal pain, nausea, postprandial vomiting, bloating c9c10c11c12c13c14
      • Enteropathy/colon hypomotility: profuse watery diarrhea and/or constipation; fecal incontinence c15c16c17
    • Urogenital
      • Bladder dysfunction (hypotonic or overactive): urinary frequency, urgency, nocturia, hesitancy, slow stream or dribbling, incontinence c18c19c20c21c22c23c24c25c26c27
        • Urgency with or without incontinence, frequency, and nocturia suggests overactive rather than hypotonic bladder
      • Male sexual dysfunction: decreased libido, erectile dysfunction, abnormal ejaculation c28c29c30
        • Erectile dysfunction is defined as the inability to achieve or maintain an erection sufficient for satisfactory sexual performance
        • Key elements of history that suggest organic (eg, neuropathic, endocrine, vascular) rather than psychogenic cause are gradual onset over time and the absence of either nocturnal tumescence or morning erection
      • Female sexual dysfunction: decreased libido, inadequate lubrication, dyspareunia c31c32c33
    • Sudomotor
      • Hypo- or anhidrosis, initially in stocking-glove distribution; may progress proximally c34c35
        • Occasionally hyperhidrosis occurs; distribution may be proximal and central to offset distal hypo- or anhidrosis c36
      • Gustatory (postprandial) perspiration over head and upper torso, even after consuming nonspicy foods c37
    • Pupillary
      • Generally asymptomatic; may experience difficulty in accommodating to rapidly changing light c38
  • Other aspects of medical history suggestive of autonomic dysfunction
    • Asymptomatic hypoglycemia c39
      • May not experience or perceive physiologic responses to hypoglycemia (ie, palpitations, tremor, lightheadedness, diaphoresis) c40c41c42c43
    • Silent myocardial ischemia c44
      • Absence of anginal pain during documented ischemia or infarction
    • Abnormal cardiovascular and thermoregulatory effects of general anesthesia
      • Hypotension, hypothermia c45c46
    • Frequent urinary tract infections c47
      • May signal the presence of neurogenic bladder
  • Medication review may identify confounding or exacerbating factors
    • ACE inhibitors, β-blockers, or diuretics may exacerbate orthostatic symptoms
    • Metformin commonly causes diarrhea
    • Anticholinergics, tricyclic antidepressants, opioids, and some hypoglycemic agents can cause constipation
    • Anticholinergics may precipitate bladder symptoms (eg, weak stream, retention)
    • Antihypertensives, antidepressants, and sedatives may contribute to erectile dysfunction

Physical examination

  • Cardiovascular
    • Resting tachycardia may be present c48
    • Test all patients for orthostatic changes in heart rate and blood pressure by measuring in seated or supine position and repeating immediately and at intervals after standing up
      • Orthostatic hypotension c49
        • Drop in systolic blood pressure of more than 20 mm Hg or drop in diastolic blood pressure of more than 10 mm Hg, measured 3 minutes after standing up from a 5-minute period in seated or supine position r3
        • Compensatory rise in heart rate may be absent r1
      • Rarely, postural orthostatic tachycardia may be observed in the absence of a drop in blood pressure r18c50
        • Increase in heart rate of 30 beats per minute or more (40 beats per minute or more for age younger than 19 years) within 10 minutes or more after standing up from seated or supine position
    • Hypertension, especially in supine position, is seen in some patients c51
  • Gastrointestinal
    • Abdominal examination findings are usually unremarkable
    • A gastric splash may sometimes be elicited c52
    • Hardened stool may be palpable in colon or on rectal examination c53
    • Poor anal sphincter tone and absent or diminished anal reflexes may be noted c54c55
  • Urogenital
    • Distended bladder may be noted on palpation and/or percussion c56
  • Sudomotor
    • Dry skin in stocking glove, lower body, or generalized distribution c57
    • Fissures may be seen in plantar surfaces c58
  • Pupillary
    • Sluggish or absent pupillary light reflex c59

Causes and Risk Factors

Causes

  • Causes of diabetic autonomic neuropathy are poorly understood. Hyperglycemia, alterations in insulin signaling, and (when present) dyslipidemia result in direct cellular damage as well as induction of inflammatory cytokines and other secondary agents of cell damage r19c60c61c62c63
    • May occur in type 1 and type 2 diabetes
  • Both sympathetic and parasympathetic pathways may be affected (though not necessarily proportionately), resulting in inadequate and/or imbalanced autonomic control of heart rate, cardiac contractility, vasomotor function, gastrointestinal and genitourinary smooth muscle contractility, sweat gland secretion, and pupillary constriction r2

Risk factors and/or associations

Age
Sex
  • Data are conflicting; may be more common in females r20r21c66c67
Genetics
  • Various genes have been associated with predisposition to development or progression of diabetic neuropathy; most of these relate to peripheral neuropathy, but preliminary evidence suggests that sequence variation of TCF7L2 and GSTM1/GSTT1 is associated with cardiac autonomic neuropathy r22c68c69
Other risk factors/associations
  • General
    • Risk increases with duration of diabetes r2c70
    • May be associated with initiation of insulin or oral hypoglycemic agents with abrupt improvement in glycemic control r23c71
      • Particularly with hemoglobin A1C reduction of 1% or more per month r14
      • Typically occurs within 2 to 8 weeks after medication initiation or dietary change r14
    • Tight glycemic control and resulting hypoglycemia may trigger autonomic dysfunction that paradoxically results in hypoglycemia unawareness; if hypoglycemia is unrecognized and repeated, glucose threshold at which symptoms are perceived may lower progressively r23c72c73
  • Cardiovascular autonomic neuropathy
    • Risk increased with older age, longer duration of diabetes, poor or unstable glycemic control, comorbid diabetic polyneuropathy, retinopathy or nephropathy, hypertension, and other cardiovascular risk factors r24
    • Poor glycemic control is the primary risk factor in patients with type 1 diabetes r24c74
    • Poor glycemic control, hypertension, dyslipidemia, obesity are risk factors in type 2 diabetes r24c75c76c77c78

Diagnostic Procedures

Primary diagnostic tools

  • In a patient with diabetes, the diagnosis may be suggested by history and physical examination findings r6c79
  • There are no laboratory studies for the diagnosis of diabetic autonomic neuropathy per se, but baseline and serial measures of glycemic control (ie, serum glucose level, hemoglobin A1C) are important in optimizing glucose management to prevent development or slow progression of neuropathy r6c80c81
    • Other studies may be recommended to evaluate for complications of neuropathies, for common comorbid factors, and for other causes and types of neuropathy (eg, distal sensory neuropathy of diabetes, nutritional deficiencies)
  • Further testing is available and may be indicated to assess suspected cardiac, gastrointestinal, and genitourinary neuropathies
    • Cardiac autonomic neuropathy r3
      • Cardiovascular autonomic reflex tests are the gold standard for diagnosing cardiovascular autonomic neuropathy; they consist of recording heart rate variability in response to maneuvers designed to elicit a sympathetic or parasympathetic response c82
        • Heart rate variation during deep breathing, Valsalva maneuver, and orthostatic maneuvers is a reflection of parasympathetic activity
          • At least one of these is recommended, in addition to orthostatic blood pressure testing on physical examination, for diagnosis and monitoring of cardiac autonomic neuropathy
          • Reduced heart rate variation may be the earliest manifestation of cardiac autonomic neuropathy r4
        • Blood pressure response to Valsalva maneuver and to standing or tilt testing is a measure of sympathetic function
      • Ambulatory blood pressure monitoring over a 24-hour period is not routinely recommended but may be helpful in identifying the following other situational manifestations of cardiovascular autonomic dysfunction: r3c83
        • Absence of normal (10% or more) nocturnal drop in blood pressure r21
        • Supine hypertension r25
        • Postprandial hypotension r25
      • Obtain an ECG to assess QTc interval and signs of cardiac ischemia r3c84
    • Gastrointestinal neuropathy
      • Gastroparesis r26
        • Studies are appropriate in symptomatic patients (ie, those with bloating, nausea, prolonged postprandial sense of fullness) or in patients with unexplained poor or erratic glycemic control
          • Gastroparesis alters timing and extent of carbohydrate and medication absorption
        • Excluding mechanical gastric outlet obstruction and peptic ulcer disease (generally with upper endoscopy and sometimes with imaging studies) is necessary before specific testing for and diagnosis of gastroparesis r27r28
        • Gastric emptying is most commonly measured by scintigraphy, which is considered the gold standard test for gastroparesis r1r27r29c85
        • Gastric emptying (¹³C octanoic acid) breath test assessment is a generally accepted alternative to scintigraphy r27r28r29c86c87
        • Wireless motility capsule and gastric ultrasonography have been used, but most recent guidelines do not endorse these modalities for assessing gastric emptying r27r29
      • Intestinal motility r26
        • Measurement of transit time may be indicated in patients with diabetes who have chronic constipation
        • A wireless motility capsule provides ongoing information about transit time through the stomach and intestines as well as luminal pressures and pH
    • Genitourinary neuropathy
      • Bladder dysfunction
        • Measure postvoid residual urine volume by either ultrasonography or catheterization r7c88c89
        • Uroflowmetry can be combined with postvoid residual estimation to provide a noninvasive assessment of urine flow rate, voided volume, intermittent flow, hesitancy, and residual urine r5
        • In patients with high postvoid residual volume, invasive urodynamic testing may be indicated to differentiate from bladder outlet obstruction r30
        • Urodynamic testing can also be helpful in evaluating incontinence when clinical information does not clearly distinguish overactive bladder (involuntary micturition due to overactive detrusor muscle) from hypotonic (neurogenic) bladder (overflow incontinence), or when treatment of presumed overactive bladder has failed r7
          • American Urological Association discourages routine urodynamic testing, cystoscopy, and imaging in patients with typical symptoms of overactive bladder (ie, urgency, urgency incontinence, frequency, nocturia) r31
        • Measure creatinine and BUN levels to assess for diabetic nephropathy or effects of chronic retention r7
      • Erectile dysfunction d1
        • For patients with suspected organic (versus psychogenic) condition
          • Because erectile dysfunction is a marker for cardiovascular disease, cardiovascular status must be assessed to determine whether vascular disease may be a contributing factor and to evaluate sexual activity risk and use of phosphodiesterase-5 inhibitors r13
          • Measure morning testosterone levels to identify or rule out hypogonadism as a contributing factor r13c90
    • Sudomotor neuropathy
      • Usually does not require testing in clinical (nonresearch) setting r1
    • Pupillary neuropathy
      • No testing required beyond demonstration of reduced light reflex on physical examination r4

Laboratory

  • Creatinine and BUN levels r7c91c92
    • In patients with neurogenic bladder, elevated levels may reflect complications of urinary retention, with or without associated diabetic nephropathy
  • Serum total testosterone levels r13c93
    • Draw fasting blood sample before 11 AM
    • Normative ranges for testosterone levels vary among laboratories and assays; clinicians should use the lower reference limit for healthy young men established in the laboratory used
    • Low levels may indicate hypogonadism as a contributing factor in erectile dysfunction
  • Hemoglobin A1C level c94
    • Key parameter for monitoring overall pattern of glycemic control
    • Optimization may retard or prevent development of autonomic neuropathy r1

Imaging

  • Gastric scintigraphy r4c95
    • Gold standard for diagnosis of gastroparesis is measurement of gastric emptying with scintigraphy after food intake r28c96
    • Scintigraphic images are taken at 15-minute intervals after consumption of digestible solids labeled with a radioisotope
      • Normal rates of stomach emptying are as follows: r23
        • 37% to 90% of meal remains at 1 hour
        • 30% to 60% remains at 2 hours
        • 0% to 10% remains at 4 hours
    • Fasting glucose level should be less than 275 mg/dL on day of test, because hyperglycemia slows gastric emptying r26
    • Patients should avoid taking promotility agents, anticholinergics, and opioids for several days before the procedure and should not smoke or consume alcohol on day of test, because these factors will alter results r26

Functional testing

  • ¹³C breath test r26r32c97
    • Nonradiographic measure of gastric emptying
    • Patient consumes ¹³C radio-labeled meal that is absorbed in the duodenum, converted into ¹³CO₂ in the liver, and released during respiration; end-tidal breath samples are collected and analyzed by mass spectrometry to plot course of gastric emptying
  • Wireless motility capsule r26c98
    • A small device swallowed by the patient that detects and transmits information on pH, temperature, and luminal pressure
    • A drop in temperature to environmental levels and/or recovery of the device in stool marks total transit time
    • Changes in pH provide adjunctive information on gastric emptying time
    • Number of contractions and other motility indices are reduced in patients with gastrointestinal neuropathy
  • Postvoid residual c99
    • After the patient voids as completely as possible, the remaining urine volume is estimated by ultrasonography, or a bladder catheter is placed and the collected urine is measured
      • A volume of 50 to 100 mL or more is considered abnormal and suggests neurogenic bladder or outlet obstruction r30
    • Can be combined with uroflowmetry to provide a noninvasive assessment of urine flow rate, voided volume, intermittent flow, hesitancy, and residual urine r5

Procedures

Cardiovascular autonomic reflex testing r15c100
General explanation r2
  • Patient is asked to perform various maneuvers designed to elicit a sympathetic or parasympathetic response while being monitored by continuous ECG
    • Deep breathing (6 breaths per minute)
    • Valsalva maneuver by exhalation into a manometer at force to achieve a pressure of 40 mm Hg for 15 seconds
    • Standing from a seated or supine position
  • Variation in heart rate response can be assessed from tracings
  • Patients should refrain from tobacco and caffeine for 2 hours and strenuous physical activity for 24 hours before the test; ideally, drugs that might alter results should also be withheld (eg, vasodilators, diuretics, antihistamines, antidepressants) r25
Indication
  • Patients with diabetes who have unexplained tachycardia, orthostatic hypotension, or prolonged QTc interval
  • After myocardial infarction in a patient with diabetes r33
Contraindications
  • Valsalva maneuver is contraindicated in patients with proliferative retinopathy
Interpretation of results r2
  • Deep breathing
    • A heart rate difference of more than 15 beats per minute between inspiration and expiration is normal; a difference of less than 10 beats per minute is abnormal
      • Specificity of about 80% r33
    • Distance between QRS complexes (R-R interval) is measured during inspiration and expiration and a ratio calculated; normal values are those exceeding a threshold defined by age (in years):
      • 20 to 24: 1.17
      • 25 to 29: 1.15
      • 30 to 34: 1.13
      • 35 to 39: 1.12
      • 40 to 44: 1.10
      • 45 to 49: 1.08
      • 50 to 54: 1.07
      • 55 to 59: 1.06
      • 60 to 64: 1.04
      • 65 to 69: 1.03
      • 70 to 75: 1.02
  • Valsalva maneuver c101
    • Ratio of longest to shortest R-R interval is calculated; a value exceeding 1.2 is normal
  • Standing
    • Normal ratio of R-R intervals measured 30 beats (or the longest observed R-R intervalr4) and 15 beats (or the shortest observed R-R intervalr4) after standing exceeds 1.03
Urodynamic studies c102
General explanation
  • Videourodynamics is the gold standard procedure for urodynamic investigation in neurourologic dysfunction r5
    • Combines filling cystometry and pressure flow studies to quantify bladder filling function, bladder capacity and compliance, bladder sensation, urine flow rates, and bladder, urethral, and abdominal pressures during micturition r5
    • Bladder is filled naturally or by instillation of saline through a bladder catheter
    • Detrusor muscle activity may be monitored through electromyography c103
Indication
  • Symptoms that are bothersome to patient (eg, frequency, incontinence) and unresponsive to conservative measures
  • High postvoid residual
  • Assessment of risk for complications (eg, frequent urinary tract infection, obstructive uropathy)
Interpretation of results
  • Large bladder capacity, poor detrusor function, and slow flow rates suggest hypotonic (neurogenic) bladder
  • Involuntary detrusor muscle contractions with urgency suggest hyperactive bladder
  • Obstructive patterns can also be detected (eg, prostatic hypertrophy, pelvic organ prolapse) and often coexist with diabetic neuropathy

Other diagnostic tools

  • ECG c104
    • 12-lead ECG may show previously unrecognized ischemia, which can be multifactorial in origin; contributing factors may include impaired vasomotor activity due to cardiac autonomic neuropathy as well as atherosclerotic coronary artery disease r34
    • Prolongation of QTc interval may be an indicator of cardiac autonomic neuropathy
      • 460 milliseconds or more in women and 450 milliseconds or more in men r3

Differential Diagnosis

Most common

  • By definition, diabetic autonomic neuropathy occurs in patients with diabetes (or less commonly, prediabetes); differential diagnoses below therefore assume a context of diabetes and the possibility of a second disease that must be differentiated from a neuropathic complication of diabetes
  • For cardiac autonomic neuropathy
    • Hyperthyroidism c105d2
      • Clinical state induced by excessive production and secretion of thyroid hormones by an overactive thyroid gland
      • Like autonomic neuropathy, may result in resting tachycardia and subjective palpitations
      • Patients with hyperthyroidism may experience tremulousness, unusual heat intolerance, and diaphoresis; there may be associated neck pain, sore throat, and, in Graves disease, eye irritation
      • Differentiation can be made based on thyroid examination findings (may be enlarged and/or nodular, and may be tender); in Graves disease, eyelid retraction and proptosis are common findings. Definitive diagnosis is based on results of thyroid function test
    • Anemia c106
      • Low circulating RBC mass or hemoglobin level
      • Significant pallor of skin, mucous membranes, and nail beds may suggest anemia rather than (or in addition to) cardiac autonomic neuropathy
      • Anemia is diagnosed by measurement of hemoglobin and hematocrit
    • Tachyarrhythmias
      • Rapid atrial fibrillation or atrial flutter c107c108c109
      • As with cardiac autonomic neuropathy, resting tachycardia is characteristic; orthostatic abnormalities may be present
      • Tachyarrhythmias may be short-lived and episodic
      • Distinction is made by ECG
    • Intravascular volume depletion
      • May be caused by dehydration or acute blood loss c110
      • Like cardiac autonomic neuropathy, may be characterized by resting tachycardia and orthostatic hypotension
      • Distinction is usually apparent from history and context
    • Heart failure c111d3
      • Inadequate cardiac pump function
      • Like cardiac autonomic neuropathy, may be characterized by resting tachycardia
      • Physical examination findings of jugular vein distention, auscultatory rales, and a third heart sound suggest heart failure and are not characteristic of diabetic cardiac autonomic neuropathy alone
      • Distinction can be confirmed by imaging (ie, chest radiograph, echocardiogram)
    • Parkinson disease c112d4
      • A progressive neurodegenerative disease caused by inadequate dopamine activity in the basal ganglia
      • As with advanced diabetic autonomic neuropathy, orthostatic hypotension is a common feature
      • Usually evident by distinctive physical findings including bradykinesia, rigidity, resting tremor, and gait impairment
  • For gastrointestinal autonomic neuropathy
    • Gastroparesis
      • Gastric outlet obstruction c113
        • May be due to malignant or inflammatory mass
        • Like gastroparesis, may cause early satiety, nausea, bloating, a sense of fullness
        • Unlike gastroparesis, there may be focal tenderness or a palpable mass on examination
        • Differentiation is made by findings on upper endoscopy or imaging
    • Irritable bowel disease c114d5
      • A functional syndrome of abdominal pain, constipation, and/or diarrhea
      • Nocturnal diarrhea may occur in diabetic gastrointestinal neuropathy; it is unusual in irritable bowel disease
      • There is no definitive diagnostic test for irritable bowel disease, which is defined clinically (Rome criteria). In a patient with diabetes, it may be difficult to distinguish irritable bowel from diabetic autonomic neuropathy
      • Abnormal results of intestinal motility studies (eg, wireless motility capsule) may differentiate diabetic gastrointestinal neuropathy from irritable bowel syndrome
    • Inflammatory bowel disease c115c116c117
      • Idiopathic, chronic inflammatory disease
      • As with diabetic autonomic neuropathy, may present with abdominal pain, diarrhea, and fecal incontinence
        • May be limited to the colon (ulcerative colitis), ord6
        • May involve any part of the gastrointestinal tract (Crohn disease) d7
      • Tends to be more episodic than diabetic autonomic neuropathy and is commonly characterized by bloody stool and systemic manifestations (eg, fever, weight loss)
      • Differentiation is based on clinical presentation and characteristic findings on endoscopy and biopsy
  • For genitourinary autonomic neuropathy
    • For bladder dysfunction
      • Bladder outlet obstruction c118
        • Can result from a variety of causes including bladder or prostate tumors, bladder stones, benign prostatic hypertrophy, sphincter dysfunction, and urethral stricture d8
        • Like neurogenic bladder, these may cause symptoms of frequency, urgency, decreased flow, and small volume void
        • In patients with diabetes, may be clinically indistinguishable from neurogenic bladder
        • Differentiation can be made through cystoscopy and urodynamic testing
      • Urinary tract infection c119d9
        • Common symptoms of both urinary tract infection and neurogenic bladder can include urinary frequency, urgency, altered flow, and incontinence
        • Unlike uncomplicated neurogenic bladder, urinary tract infection symptoms may include fever, hematuria, and dysuria
        • Urinary tract infection is diagnosed based on urine dipstick finding indicating leukocyte esterase and nitrite positivity, microscopic urinalysis indicating WBC and bacteria, and urine culture showing bacterial growth
        • Urinary tract infection may complicate neurogenic bladder
      • Medication effect c120
        • Anticholinergic medications can cause urinary retention that may be mistaken for neurogenic bladder
        • Sympathomimetic medications can cause urinary frequency and retention that may be mistaken for neurogenic bladder
        • Diagnosis can be differentiated by a period of drug abstinence
    • For erectile dysfunction c121d1
      • Erectile dysfunction is defined as the inability to maintain an erection sufficient for intercourse; there is no true differential diagnosis, although there are many possible causes
      • Evaluation focuses on defining the underlying cause of patient's erectile dysfunction, primarily determining whether it is due to organic or psychogenic causes
        • Psychogenic erectile dysfunction is suspected based on historical features and the absence of an organic cause; supported by the presence of nocturnal and spontaneous morning erection
        • Organic erectile dysfunction is suspected based on risk factors, history, and results of physical examination; it may be due to vascular disease, hormonal imbalance, and/or neuropathy, or to other physical abnormalities (eg, Peyronie disease, penile malignancy)
  • For sudomotor dysfunction
    • Defined as abnormality in sweating, resulting in hyper- or hypohidrosis; either or both can be seen in patients with diabetic autonomic neuropathy, albeit in different distributions
    • Does not, therefore, have a differential diagnosis, but may present as a manifestation of a number of syndromes associated with autonomic dysfunction
    • Usually not the predominant presenting symptom, and usually noted secondarily in association with a constellation of dominant findings that define the syndrome

Treatment

Goals

  • Maintain optimal glycemic control to slow further progression r4
  • Management of focal symptoms through lifestyle changes, mechanical or physiologic measures, and pharmacologic intervention r6

Disposition

Admission criteria

  • Diagnosis and management of diabetic autonomic neuropathy occur primarily in an outpatient setting
  • Occasionally, severe complications stemming from autonomic neuropathy (eg, syncope, falls, labile glucose levels due to erratic gastrointestinal function, urosepsis) may warrant admission

Recommendations for specialist referral

  • Referral to a neurologist for aid in diagnostic testing and optimal management is appropriate for all patients with suspected diabetic autonomic neuropathy
  • Although routine cardiac autonomic reflex tests can be done by a primary care practitioner, patients are commonly referred to a cardiologist or neurologist for testing
    • If testing is done in the primary care setting, refer patients with abnormal results to a cardiologist for assessment of cardiovascular disease and exercise tolerance and for optimal management of cardiovascular risk factors
      • After approval by cardiology consultant, refer to a physiatrist for appropriate exercise program
    • Refer patients with erectile dysfunction to a cardiologist for cardiovascular status evaluation, assessment of fitness for sexual activity, and safety of phosphodiesterase-5 inhibitors
  • Refer patients with gastroparesis or severe constipation to a gastroenterologist for upper or lower endoscopy as indicated, to coordinate gastric emptying studies, and aid in management
  • Refer patients with significant bladder symptoms to a urologist to consider cystoscopy and urodynamic studies
  • Patients with erectile dysfunction may require referral to a urologist if further testing is needed to determine cause or if first line treatment efforts are unsuccessful or contraindicated
  • All patients with autonomic diabetic neuropathy should be managed in conjunction with an endocrinologist to optimize glycemic control

Treatment Options

Maintain optimal glycemic control; minimize cardiovascular risk factors

  • Dietary and pharmacologic management to attain individualized hemoglobin A1C goal based on life expectancy, disease duration, presence or absence of micro- and macrovascular complications, cardiovascular risk factors, comorbid conditions, and risk of hypoglycemia r35
    • Diabetes Control and Complications Trial followed 1441 insulin-dependent people with diabetes managed on either a conventional regimen or an intensive glycemic control program; over the 9 years of the trial, fewer cardiac reflex abnormalities developed in patients in the intensive glycemic control arm. Incomplete bladder emptying was also less common in the intensive control group r36
    • During follow-up for an additional 13 to 14 years, the frequency of cardiac reflex abnormalities grew in each group but differences between the groups persisted, with lower rates in the intensive treatment group r37
    • Intensive glycemic control may be more effective in type 1 than type 2 diabetes with respect to development and/or progression of neuropathy r2
    • Among patients with type 2 diabetes participating in the Action to Control Cardiovascular Risk in Diabetes trial, those who received intensive glycemic therapy had substantially reduced risk of cardiovascular autonomic neuropathy; this was especially true among those without a history of cardiovascular disease at baseline r38r39

System-specific management

  • In most cases, there are no guideline-driven, stepwise treatment regimens; rather, approach should be individualized, generally beginning with most conservative measures and adding or modifying therapy as needed
  • Cardiac
    • General
      • Weight loss if indicated
        • Several studies have shown improvement in cardiac autonomic function in obese people both with and without diabetes after significant weight loss r40r41
      • Manage cardiovascular risk factors r38
        • Intensive blood pressure control substantially reduced risk of cardiovascular autonomic neuropathy in patients with type 2 diabetes r39
      • Moderate-intensity aerobic exercise training
        • Several systematic reviews have shown beneficial effects on functional capacity, metabolic control, circulating inflammatory markers, and cardiac autonomic activity r42r43r44
      • Pharmacologic agents
        • ACE inhibitors,r46angiotensin receptor blockers,r47 and cardioselective β-blockersr48 have all been shown to improve cardiac reflex parameters in patients with diabetic autonomic neuropathy and have been used alone or in various combinations r33r45
        • There is evidence that sodium-glucose transporter 2 inhibitors exert a modulatory effect on cardiovascular autonomic function; however, these do not have an established role in management r24
    • Orthostatic hypotension r28r49
      • Mechanical and physiologic measures to prevent or counteract drop in blood pressure r3
        • For patients whose orthostatic symptoms occur in association with a meal, advise smaller, more frequent meals
      • Maintenance of intravascular volume through increased intake of fluid and salt (if not contraindicated) r1
      • Physical conditioning
      • Avoid elevation in body temperature
      • Head-up position while sleeping
      • Compression garments
      • Pharmaceutical support (eg, mineralocorticoids, oral vasopressors) may be necessary for symptomatic patients who do not respond to conservative measures. Care must be taken to avoid supine hypertension; educate patients to take these medications only when upright position is intended (eg, daytime) r1
        • Fludrocortisone may aid in maintaining intravascular volume though efficacy data is lacking; according to a recent Cochrane review, evidence of the effects of fludrocortisone on blood pressure, orthostatic symptoms, or unfavorable occurrences in people with orthostatic hypotension and diabetes is of very low certainty r50
        • Midodrine increases peripheral vascular tone through adrenergic stimulation; concomitant fludrocortisone increases the effect r51
        • Droxidopa is metabolized to norepinephrine with resulting increase in vascular tone r52
        • Pyridostigmine has been used off-label r49
        • Octreotide may be helpful in patients with postprandial orthostatic hypotension r53
  • Gastrointestinal
    • Gastroparesis r9r28
      • Frequent, small meals rather than conventional meal schedule may prevent sensation of fullness and bloating
      • Promotility drugs may improve transit time and symptoms; these include dopamine antagonists (eg, metoclopramide) and erythromycin
        • Metoclopramide (oral and nasal spray) are the only agents approved by FDA for treatment of gastroparesis r54
          • Should be used only for severe cases and not for more than 12 weeks owing to potential for serious adverse effects r28
          • Available as oral
        • Erythromycin: can be used off-label but is effective only for short-term use owing to tachyphylaxis r28
      • Avoidance and/or discontinuation of drugs with antimotility effects, such as opioids, anticholinergic agents, and tricyclic antidepressants, may also enhance intestinal motility r28
      • Patients with severe, refractory symptoms may require placement of gastrostomy or jejunostomy, or procedures such as partial gastrectomy, pyloroplasty, gastrojejunostomy, or gastric peroral endoscopic myotomy r54
      • Gastric electrical stimulation has been effective in improving symptoms, gastric emptying time, and nutritional statusr55 in patients with severe refractory diabetic gastroparesis r8
        • More effective for nausea and vomiting than for other symptoms r55
    • Diarrhea
      • Trial of dietary restriction, avoiding soluble fiber, lactose, and glutenr6
      • Loperamide; avoid opiates or other constipating agents r9
      • Because stasis-induced bacterial overgrowth has been postulated as a cause, some authorities recommend antibiotics (eg, metronidazole)r2
      • Clonidine may slow colonic transit time by opposing adrenergic stimulation r53
      • Cholestyramine or octreotide may be effective in patients who do not respond to other measures r53
    • Constipation
      • High-fiber diet with addition of bulking agents (eg, psyllium) r6
      • Osmotic laxatives (eg, milk of magnesia) r6
  • Genitourinary
    • Treatment of urinary symptoms depends on suspected mechanism
      • If possible, discontinue any medications that contribute to genitourinary dysfunction such as anticholinergic agents and tricyclic antidepressants r56
      • Neurogenic (hypotonic) bladder r7
        • Techniques such as scheduled voiding, assisted bladder emptying using Valsalva maneuver or manual pressure over bladder (Credé maneuver), and triggered voiding have been recommended by some authorities r5
          • Guidelines from the European Association of Urology recommend against Valsalva and Credé maneuvers because of concerns that increased intravesical pressure may lead to reflex sphincter tightening and also inflict further damage on lower urinary tract r5
        • Intermittent catheterization may be necessary if other measures are ineffective; consider the preferred management by the European Association of Urology r5
        • Bethanechol may be considered in some cases of overflow incontinence r56
      • Overactive bladder r31
        • Lifestyle modifications include attention to timing of fluid intake and avoidance of bladder irritants
        • Weight reduction, if indicated, can reduce stress and urgency incontinence
        • Bladder training to increase time between voids
        • Pelvic floor (Kegel) exercises
          • With or without additional bladder training, shown to improve symptoms in women with incontinence r10
        • Pharmacologic agents may be added if conservative measures are not sufficient
          • Antimuscarinic agents such as oxybutynin, tolterodine, trospium chloride, fesoterodine, solifenacin, darifenacin are first line pharmacologic agents; they do not appear to differ in efficacy
          • Mirabegron, a β-agonist, is also effective in reducing incontinence and frequency of voiding, and is recommended as another first line option; evidence suggests efficacy similar to the antimuscarinic agents r11
        • Botulinum toxin, electrical stimulation of posterior tibial nerve, and various surgical procedures may be options for patients who do not respond to other measures r31
          • Although the mechanism is unclear, electrical stimulation of posterior tibial nerve appears to achieve durable success in most patients who meet criteria (ie, failure of noninvasive measures, ability to comply with treatment and with follow-up schedule) r31
          • Injection of bladder with botulinum toxin improves incontinence symptoms due to overactive bladder in more than 50% of patients with diabetes treated, and improvement typically lasts for more than 6 months r31
            • Patients require regular postvoid residual evaluation and must be able to perform self-catheterization if needed
    • Erectile dysfunction r6r28
      • If psychogenic factors and hypogonadism have been excluded and if cardiovascular risk is deemed acceptable, pharmacotherapy with oral phosphodiesterase-5 inhibitors or intraurethral or intracorporeal prostaglandin E₁ is recommended
      • When medication is ineffective, vacuum devices and penile prostheses are alternative options
  • Sudomotor dysfunction does not usually require treatment, although associated skin dryness should be treated with emollients to avoid fissuring

Drug therapy

  • For cardiac autonomic neuropathy
    • General
      • ACE inhibitor
        • Quinapril c122
          • Quinapril Hydrochloride Oral tablet; Adults: 20 mg PO once daily. r46
      • Angiotensin receptor blocker
        • Losartan c123
          • Losartan Potassium Oral tablet; Adults: 100 mg PO once daily. r47
      • Cardioselective β-blockers
        • Metoprolol r48c124
          • Metoprolol Succinate Oral tablet, extended-release; Adults: 100 mg PO once daily.
        • Bisoprolol c125
          • Bisoprolol Fumarate Oral tablet; Adults: 5 mg PO once daily. r57
    • For orthostatic hypotension
      • Mineralocorticoid
        • Fludrocortisone r1c126
          • Fludrocortisone Acetate Oral tablet; Adults: initially 0.1 mg PO once daily in the morning, increasing weekly as needed to maximum 0.3 mg daily.
      • Sympathomimetic
        • Midodrine c127
          • Midodrine Hydrochloride Oral tablet; Adults: 10 mg PO tid. A suggested 4-hour dosing interval schedule is as follows: shortly before or upon rising qAM, midday, and late afternoon (not later than 6 PM).
      • Vasopressor
        • Droxidopa c128
          • Droxidopa Oral capsule; Adults: 100 mg PO 3 times daily, upon arising in AM, midday, and late afternoon at least 3 hours prior to bedtime. Titrate to symptomatic response, in increments of 100 mg 3 times daily every 24 to 48 hours up to a dose of 600 mg PO 3 times daily (Max: 1,800 mg/day PO). Monitor supine blood pressure prior to initiating droxidopa and at every dosage increase. Assess efficacy periodically.
      • Somatostatin analogue
        • Octreotide c129
          • Octreotide Acetate Solution for injection; Adults: Optimal dose not established. A usual starting dose is 12.5 mcg to 25 mcg subcutaneously 3 times per day, then titrated to effect. Usually reserved for patients not responsive to standard therapies due to limited data. One study has used 100 mcg subcutaneously as a single dose acutely. Low doses (0.2 to 0.4 mcg/kg subcutaneously) and high doses (up to 1.6 mcg/kg subcutaneously) have also been studied.
  • For gastrointestinal neuropathy
    • Gastroparesis
      • Dopamine antagonists
        • Metoclopramide c130
          • Metoclopramide Hydrochloride Oral tablet; Adults: 10 mg PO, IV, or IM 4 times daily, 30 minutes before meals and at bedtime. Max: 40 mg/day PO. If a CYP2D6 poor metabolizer: 5 mg PO, IV or IM 4 times daily (Max: 20 mg). Consider a similar lower initial dosage for geriatric patients. Avoid treatment with metoclopramide (all dosage forms and routes of administration) for more than 12 weeks because of the increased risk of tardive dyskinesia (TD) with longer-term use. Coadministration of certain drugs may need to be avoided or dosage adjustments may be necessary; review drug interactions.
        • Domperidone c131
          • Available in the United States as an investigational new drug per FDA; commercially available in Canada, Europe, Australia, and other countries
          • Recommended for patients with gastroparesis unresponsive to or with adverse effects from metoclopramide r29
          • Domperidone Oral tablets; Adults: initially, 10 mg PO 3 times daily, before meals, increasing to 20 mg 4 times daily, before meals and at bedtime. (Note that this exceeds maximum dose recommended in package insert.r59) r29r58
          • Domperidone carries the risk of QT prolongation and torsades de pointes. A baseline ECG is recommended; withhold treatment if the corrected QT interval is more than 470 milliseconds in male patients and 450 milliseconds in female patients. A follow-up ECG during therapy is advised. r29
      • Motilin receptor agonist
        • Erythromycin c132
          • Erythromycin Oral tablet; Infants, Children, and Adolescents: 3 mg/kg/dose PO 4 times daily; up to 10 mg/kg/dose (Max: 250 mg/dose) PO 4 times daily has been used; however, data are limited. Long-term use limited by tachyphylaxis.
          • Erythromycin Oral tablet; Adults: 250 to 500 mg PO 3 times daily, 30 minutes before meals, is recommend in guidelines for patients with persistent symptoms following trials of standard prokinetic therapy (e.g., metoclopramide). The oral suspension is often utilized due to rapid absorption and to facilitate dose modifications. Clinical responsiveness to oral erythromycin declines after 4 weeks.
    • Diarrhea
      • Antidiarrheal agent
        • Loperamide c133
          • Loperamide Hydrochloride Oral tablet; Adults: 4 mg PO initially, then 2 mg after each subsequent unformed stool until diarrhea is controlled. Then, reduce to meet individual requirements. Average daily maintenance dosage: 4 to 8 mg/day. Max: 16 mg/day PO.
      • Polymeric resin
        • Cholestyramine c134
          • Cholestyramine Powder for Oral suspension; Adults: 2 to 4 g PO 2 to 4 times daily.
      • Centrally acting α-1 agonist
        • Clonidine c135
          • Clonidine Hydrochloride Oral tablet; Adults: Initially, 0.1 mg PO q12h and increased over a period of 3 days up to 0.5—0.6 mg PO q12h.
      • Somatostatin analogue
        • Octreotide c136
          • Octreotide Acetate Solution for injection; Adults: Varying doses reported. 50 to 100 mcg subcutaneously every 8 to 12 hours.
      • Antibiotics
        • Metronidazole c137
          • Metronidazole Oral tablet; Adults: 250 mg PO 3 times daily for 3 weeks or longer. r53
  • Urogenital neuropathy
    • Hypotonic bladder
      • Parasympathomimetic
        • Bethanechol c138
          • Bethanechol Chloride Oral tablet; Adults: Determine minimal effective dose initially by giving 5—10 mg, repeating at hourly intervals until therapeutic goals attained or up to max 50 mg PO total dose. Usual dosage: 10—50 mg PO, given 3—4 times per day.
    • Overactive bladder
      • Antimuscarinic agents
        • Note that these drugs may cause or exacerbate constipation and gastroparesis
        • Antimuscarinic agents are contraindicated in patients with narrow-angle glaucoma
        • Oxybutynin c139
          • Oxybutynin Chloride Oral tablet; Adults: 5 mg PO 2 to 3 times daily. Max: 5 mg PO 4 times daily.
          • Oxybutynin Chloride Oral tablet; Geriatric: 2.5 mg PO 2 to 3 times daily, initially. Usual dose: 5 mg PO 2 to 3 times daily. Max: 5 mg PO 4 times daily.
        • Tolterodine c140
          • Tolterodine Tartrate Oral tablet; Adults: 2 mg PO twice daily; some patients may respond to 1 mg PO twice daily. If concurrently taking CYP3A4-inhibiting drugs, reduce to 1 mg PO twice daily.
        • Trospium chloride c141
          • Trospium Chloride Oral tablet; Adults: 20 mg PO twice daily.
          • Trospium Chloride Oral tablet; Geriatric Adults: Initially, 20 mg PO twice daily. May adjust downward to 20 mg PO once daily at bedtime if anticholinergic side effects are intolerable.
        • Fesoterodine c142
          • Fesoterodine fumarate Oral tablet, extended-release; Adults: 4 mg PO once daily initially; may increase to 8 mg PO once daily based upon response and tolerability. Max: 8 mg/day PO. Coadministration of certain drugs may need to be avoided or dosage adjustments may be necessary; review drug interactions.
        • Solifenacin c143
          • Solifenacin Succinate Oral tablet; Adults: 5 mg PO once daily. May increase to 10 mg PO once daily if needed/tolerated. Max: 10 mg/day; in patients taking potent inhibitors of CYP3A4, do not exceed 5 mg/day. USE WITH MIRABEGRON: The FDA-approved dose for solifenacin is 5 mg PO once daily when given with mirabegron.
        • Darifenacin c144
          • Darifenacin Oral tablet, extended-release; Adults: 7.5 mg PO once daily. May increase to 15 mg PO once daily after 2 weeks based on response. Max: 15 mg/day PO; do not exceed 7.5 mg/day PO in patients taking potent CYP3A4 inhibitors.
      • β-agonist
        • Mirabegron c145c146
          • Mirabegron Oral tablet, extended-release; Adults: 25 mg PO once daily. Based on efficacy and tolerability, may increase to 50 mg PO once daily after 4 to 8 weeks. USE WITH SOLIFENACIN: 25 mg PO once daily with solifenacin (5 mg/day PO). Based on efficacy and tolerability, may increase mirabegron to 50 mg PO once daily if needed after 4 to 8 weeks.
    • Erectile dysfunction
      • Phosphodiesterase-5 inhibitors
        • Note that these medications have interactions with a wide range of other drugs; check specific drug-drug interactions before prescribing
        • Sildenafil c147
          • Sildenafil Citrate Oral tablet; Adult Males: 50 mg PO, approximately 1 hour prior to sexual activity, up to once daily. Increase to 100 mg or decrease to 25 mg based on response. Max: 1 dose/day.
          • Sildenafil Citrate Oral tablet; Geriatric Males: 25 mg PO, approximately 1 hour prior to sexual activity, up to once daily.
        • Tadalafil c148
          • Tadalafil Oral tablet; Adult males: 10 mg PO before anticipated sexual activity; increase to 20 mg or decrease to 5 mg based on efficacy and tolerability; max dosing frequency is once daily in most patients.Coadministration of certain drugs may need to be avoided or dosage adjustments may be necessary; review drug interactions.
        • Vardenafil c149
          • Vardenafil Hydrochloride Oral tablet; Adult males: Initially, 10 mg PO approximately 60 minutes before sexual activity. For males 65 years of age or older, consider a lower starting dose of 5 mg PO. The maximum dosing frequency is once per day. May titrate based on efficacy and side effects. Max: 20 mg/day PO. ADJUSTMENTS: Review drug interactions. Vardenafil dosage reductions are required in patients taking moderate or potent CYP3A4 inhibitors. If coadministering with an alpha-blocker, patients should be stable on alpha blocker therapy before starting vardenafil, and the initial vardenafil dose should be reduced to 5 mg (or 2.5 mg if given with certain CYP3A4 inhibitors).
        • Avanafil c150
          • Avanafil Oral tablet; Adults: 100 mg PO once daily, approximately 15 minutes before sexual activity. Increase up to 200 mg PO, approximately 15 minutes before sexual activity or decrease to 50 mg PO, approximately 30 minutes before sexual activity, based on clinical response. Maximum dosing frequency is once daily.
      • Prostaglandin E
        • Alprostadil c151
          • Alprostadil Urethral suppository; Adult males: 125 mcg or 250 mcg into the urethra as directed. Max: 2 doses per 24-hour period.

Nondrug and supportive care

For obese patients, weight loss is beneficial for overall diabetes management and has been shown to reverse progression of cardiac autonomic neuropathyr60r61 as well as incontinence associated with overactive bladderr31

  • May be achieved through conventional means (ie, calorie restriction, increased physical activity) or bariatric surgery r62c152c153c154c155

Exercise training r6c156c157

  • Graded exercise program designed and supervised by a physiatrist

Physiologic maneuvers to mitigate effects of orthostatic hypotension

  • Use of support garments (ie, legs, abdomen), dorsiflexion leg exercises to enhance muscle pump activity, avoidance of sudden postural changes or prolonged standing, and raising head of bed r3c158c159c160c161c162
  • Maintain fluid intake of 2 to 3 L/day if not contraindicated r25c163

Dietary modification including frequent small meals, low in fat (less than 40 g/day)r53 and fiber, may relieve symptoms of gastroparesis r9c164c165c166

Behavioral modifications may be helpful for patients with bladder dysfunction, including the following: r7

  • Minimize fluid intake late in the day and before bedtime c167c168
  • Avoid alcohol (a diuretic) and caffeine (an irritant) c169c170
  • Scheduled voiding (eg, every few hours) c171

Other bladder management techniques r7

  • Pelvic muscle (Kegel) exercises c172
    • Instruction and supervision should be provided by a practitioner trained to teach the method
  • Bladder training r12c173
    • Establish schedule of initial intervals based on bladder diary
    • Increase interval by 15 to 30 minutes per week until desired/convenient schedule is achieved
    • Relaxation and distraction techniques are used to relieve urgency
  • Intermittent straight catheterization c174

Vacuum devices for erectile dysfunction r63

  • Consist of a closed-end cylinder, vacuum pump, and constriction ring c175
  • Vacuum chamber generates negative pressure within the penis, increasing blood flow and resulting in sinusoidal distention
  • Constriction rings are then applied to maintain the erection

Patients with extensive anhidrosis should be educated about risks of hyperthermia and heat stroke r53c176

Procedures
Gastric electrical stimulation c177
General explanation
  • Battery-driven pulse generator is implanted in abdominal wall to deliver electrical stimulation to smooth muscle of stomach via electrodes implanted in gastric wall
Indication
  • Nausea and vomiting associated with diabetic gastroparesis that is refractory to other measures
Intravesical injection of botulinum toxin r31c178
General explanation
  • Botulinum toxin (usually onabotulinumtoxinA) is injected at various points in the bladder, most commonly the detrusor muscle
Indication
  • Persistent incontinence due to overactive bladder despite behavioral and pharmacologic treatment
Complications
  • Urinary retention requiring intermittent straight catheterization
  • Systemic effects of the toxin (ie, dysphagia, eyelid weakness, visual impairment, limb and/or trunk weakness)
Electrical stimulation of posterior tibial nerve c179
General explanation
  • Application of low-level electrical current applied to posterior tibial nerve via needle electrode r12
  • Treatment consists of 30 minutes weekly for 12 weeks or more; some protocols involve periodic follow-up maintenance treatments r31
Indication
  • Persistent incontinence due to overactive bladder despite behavioral and pharmacologic treatment
Implantation of penile prosthesis c180
General explanation
  • Surgical implantation of a semirigid or hydraulic (inflatable) device
Indication
  • Organic erectile dysfunction refractory to medical therapy
Contraindications
  • Cardiac function inadequate for safe sexual activity

Special populations

  • Pregnant patients should avoid or discontinue ACE inhibitors and angiotensin receptor blockers

Monitoring

  • No specific guidelines exist for frequency of monitoring established diabetic autonomic neuropathy; in view of its negative effect on prognosis, it is prudent to inquire about existing and potential symptoms at each follow-up visit c181

Complications and Prognosis

Complications

  • Autonomic neuropathy is a complication of diabetes; further complications are sometimes difficult to attribute solely to the neuropathy, but there are some characteristic associations for which the presence of autonomic neuropathy appears to be an independent risk factor
    • Cardiovascular complications r64
      • Labile blood pressure c182
        • Normal diurnal variation in blood pressure may be disrupted in cardiac autonomic neuropathy, resulting in the absence of a normal dip in nocturnal blood pressure
          • Associated with left ventricular hypertrophy r3
        • Some patients experience blood pressure elevations in the supine position at any time of day (supine hypertension)
          • Management of supine hypertension and orthostatic hypotension can be challenging; scheduled use of short-acting antihypertensives (eg, captopril) at night coupled with daytime use of short-acting sympathomimetics or vasopressors may be reasonable r25
        • Lack of normal hemodynamic response increases risk of profound and refractory hypotension during anesthesia r25
      • Cardiomyopathy c183
        • Systolic and diastolic dysfunction have been associated with cardiac autonomic neuropathy even in the absence of atherosclerotic coronary disease r2
      • Silent myocardial infarction r3c184
        • Absence of pain with myocardial ischemia may be multifactorial but is associated with the presence of cardiac autonomic neuropathy
        • May delay recognition and treatment, contributing to worse prognosis of myocardial infarction in patients with diabetes
      • Increased mortality after myocardial infarction c185
        • Decreased heart rate variability is a marker of mortality risk r2
      • Sudden death r2c186
        • Cardiac autonomic neuropathy is associated with prolonged QTc interval and malignant arrhythmias
      • Stroke c187
        • Presence of cardiac autonomic neuropathy has been correlated with increased risk of ischemic stroke r4r25
    • Gastrointestinal complications r18
      • Bezoars may form as a result of poor gastrointestinal motility c188
      • Gastritis and/or gastric ulcers may result from gastroparesis c189c190
      • Poor gastrointestinal motility alters the dynamics of food absorption, complicating glycemic control; absorption of oral medication may also be affected
    • Urogenital complications
      • Urinary retention owing to neurogenic bladder predisposes to urinary tract infection, including pyelonephritis r4c191c192c193c194
      • Frequent infection as well as urodynamic abnormalities may contribute to renal dysfunction
      • Presence of autonomic neuropathy—specifically cardiac and pupillary—appears to be an independent predictor of progressive diabetic nephropathy r3
    • Sudomotor complications
      • Anhidrosis involving extensive body surface may predispose to heat stroke r53c195

Prognosis

  • Symptomatic autonomic dysfunction is an indicator of poor prognosis r2
    • 25% to 50% mortality within 5 to 10 years of diagnosis
    • 5-year mortality is approximately 3 times higher than in people with diabetes who do not have autonomic dysfunction r65

Screening and Prevention

Screening

At-risk populations

  • Yearly screening for diabetic autonomic neuropathy is recommended as follows: r3r6
    • Asymptomatic patients with type 2 diabetes at time of diagnosis
    • Patients with type 1 diabetes 5 years after diagnosis
  • Also recommended under the following circumstances: r25
    • Asymptomatic patients with diabetes during preoperative evaluation
    • Before starting a new physical fitness program
  • Regular screening for neurogenic orthostatic hypotension is recommended for patients known to have diabetic peripheral neuropathy r49

Screening tests r6r33

  • Clinical history
  • Cardiac reflex tests
    • Heart rate variability with deep breathing c196
    • Heart rate response to Valsalva maneuver c197
    • Orthostatic blood pressure and heart rate measurements c198

Prevention

  • To prevent autonomic neuropathy, the American Diabetes Association recommends optimizing glycemic control as early as possible for patients with type 1 diabetes and adopting a multifactorial approach that includes aggressive management of cardiovascular risks as well as good glycemic control in patients with type 2 diabetes r1
    • Intensive glucose control resulted in a 45% reduction in the development of cardiac autonomic neuropathy in type 1 diabetes in the Diabetes Control and Complications Trial r36
    • Intensive glycemic control alone is less effective in preventing neuropathy in type 2 diabetes; the Steno-2 Study showed a near 60% reduction in risk for cardiac autonomic neuropathy through a multipronged program of good glycemic control and specific measures aimed at reducing other cardiac risk factors over a period of almost 8 years. These measures include the following: r38c199
      • Low-fat diet (less than 30% daily calorie intake from fat, less than 10% of daily calorie intake from fatty acids) c200
      • Light to moderate exercise (30 minutes 3 to 5 times per week) c201c202
      • ACE inhibitor or angiotensin receptor blocker (regardless of blood pressure) c203c204
      • Daily aspirin (150 mg) c205
      • Treatment of dyslipidemia c206
      • Smoking cessation if applicable c207
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