Sildenafil citrate induced penile doppler
Erectile dysfunction is the occassional or consistent inability of a male to attain and maintain a penile erection sufficient enough and for a suffcient duration so as to allow vaginal penetration.
Erectile dysfunction is multifactorial in etiology. In general erectile dysfunction increases with age, type 2 diabetes mellitus, hypertension, history of smoking, stressful lifestyle and also as complication following intrapelvic surgeries.
Penile duplex doppler using intracorporeal pharmacoactive agents like papaverine is the investigation of choice as well as the usual first step.
For complete discussion on etiologies and details of papaverine induced color duplex doppler please see Penile Doppler: role in erectile dysfunction.
The notable negative side effects to the routinely performed papaverine induced color duplex doppler are discomfort related to intracorporeal injection, anxiety and prisapism, a state of persistent and painful erection which require treatment with blood aspiration, irrigation and injection of alpha-agonist medications.
Recently sildenafil citrate induced penile Doppler has emerged as a safer and more acceptable alternative. Sildenafil citrate is a popular vasodilator drug used in treatment of erectile dysfunction and can achieve an erection in as many as 85% of cases irrespective of the cause.
The sildenafil protocol involves a baseline study without administration of pharmacological agent and includes:
- measurement of cavernosal artery diameter on either sides (0.3 to 0.5 mm is considered normal)
- evaluate calcification in cavernosal artery wall (atherosclerotic or diabetic) and tunica albuginea (Peyronie's disease)
- peak systolic velocity, acceleration time, resistive index of cavernosal artery
- end diastolic flow and presence or absence of diastolic reversal of flow
50mg of sildenafil citrate is administered orally to the patient. The parameters are measured without manual or audiovisual stimulation at 60 minutes post administration as the blood levels reach peak value by this time. Since sildenafil citrate requires a direct sexual stimulus for maximum effectiveness, an audiovisual stimulus (15 minutes of private continuous visualization of an erotic video) was given. After that, clinical and doppler evaluations were again performed at 5-minute intervals for another 20 minutes with the patient still receiving the audiovisual stimulus.
The only adverse effects documented are mild headaches and occasional blurring of vision which could be explained to the patient prior to the procedure.
Semiquantitative clinical grading of an erection:
- score of 0: flaccid
- score of 1: mild engorgement of the penis without adequate rigidity
- score of 2: partial erection allowing minimal compression
- score of 3: full visible erection with turgidity and complete stiffness of the penis
Duplex Doppler evaluation of erection:
Cut-off values to define sufficient arterial response are:
- peak systolic velocity (PSV) >25cm/s
- 60% increase in cavernosal artery diameter
- acceleration time (AT) <72 ms.
Cut-off value to define sufficient venoocclusion are:
- end diastolic forward flow velocity < 5cm/s
- resistance index >1.00.
Sildenafil citrate induced penile Doppler offers a safer alternative to papaverine induced study with 90% sensitivity and 100% selectivity. It is more acceptable to patients as compared to intracorporeal injections.
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