Phentolamine testing

Phentolamine testing

c. Phentolamine testing

(1) Premise: Inappropriate smooth muscle or striated muscle activity with bladder outlet obstruction has been associated with the neurologically impaired bladder. Smooth muscle components are under the control of the autonomic nervous system. The striated muscle is under peripheral nervous system control. When symptoms are caused by the smooth muscle component, the pharmacologic manipulation of the sympathetic nervous system has been shown to be of benefit.

(2) The phentolamine test is used to select patients most likely to benefit from the use of adrenergic blocking agents. See relaxation of the urethral smooth muscle component of bladder neck.

(3) This test compares the urethral closure pressure profile before and after injection of phentolamine.

(4) An IV bolus of phentolamine mesylate, 0.1 mg/kg, is given, after which blood pressure and pulse are recorded every minute until a tachycardia of at least 10 beats per minute occurs. The urethral pressure profile is then repeated and the patient is observed for 30 minutes for any untoward effects from the drug.

(5) A positive test: A decrease of 30% or more occurs in the maximum urethral closure pressure after injection of phentolamine.

(6) These patients can be offered a trial of alpha-1 blockers, d. Glycopyrrolate test: (formerly pro-banthine stimulation test)

(1) Glycopyrrolate is an anticholinergic test.

(2) IV glycopyrrolate, 0.4 mg, is given.

 

(3) A cystometrogram is done before and 10 to 25 minutes after injection.

(4) The disappearance or decrease in the amplitude or the frequency of uninhibited contractions indicates that the patient may respond to outpatient therapy.

(5) Note: This test is almost never performed in clinical practice. The efficacy of newer anticholinergic medications, their rapid absorption (sublingual forms), and their different concentrations makes it far easier to use them than to expose a patient to IV glycopyrrolate.

(6) Glaucoma and obstructive gastrointestinal disease are contraindicated.

e. Urethral denervation sensitivity testing1 (also listed as noradrenaline supersensitivity test of the urethra)

(1) The primary innervation of the urethra is through sympathetic alpha fibers.

(2) Baseline maximum urthral closure pressure is determined.

(3) Four mg IV ethylphenylephrine is given.

(4) Five minutes later, a repeat maximum closure pressure is obtained.

(5) Chronic urethral denervation is present when there is a rise of 15 cm or greater of water in the closure pressure from control.

f. Marshall-Marchetti-Bonney stress test16 (also called the cough-

stress test)

(1) The patient coughs with a full bladder while the examiner observes the urethra for urine loss.

(2) The examiner manipulates the urethrovesical angle either by placing Allis clamps on the anterior vaginatl wall, lateral to the urethrovesical angle, or more commonly by inserting two fingers into the lateral fornices of the vagina, pushing the bladder base up and anteriorly without compressing the urethra closed. The patient coughs and bears down again. The practitioner observes leak with cough but no leak with bladder base elevation: true stress urinary incontinence.

(3) Controversy: This test presumes to simulate the results of the planned surgical procedure by elevation and stabilization of the urethra and vesical neck. Evidence by Bergman has demonstrated that this test restores continence by occlusion of the urethra and vesical neck. Regardless, it remains a mainstay of tests in the evaluation of female incontinence.

g. Q-tip test

(1) Using an orthopedic goniometer

(a) Normal: with straining, 0-degree to 20-degree deflection

(b) Urethral hypermobility (associated with genuine stress incontinence); greater than 25-degree deflection

(2) Note: Recent evidence indicates that the Q-tip test is not specific for stress urinary incontinence because a positive result reflects anterior vaginal muscle relaxation rather than sphincteric incompetence. In addition, this test is thought to  have a false-negative rate for the diagnosis of stress urinary incontinence of 30%, especially in elderly females, h. Pessary test

(1) Premise: The vaginal pessary may increase urethral closure and urethral functional length in women with a mild to moderate cystocele. The pessary restores continence by stabilization of the bladder base, allowing proper pressure transmission to the urethra, and by active enhancement of urethral resistance, by increasing urethral functional length and closure pressure.

(a) Positive: surgical correction

(b) Negative: urodynamic evaluation

(2) Note: This test is thought to be unpredictable in the elderly.

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