To evaluate and compare the cutaneous temperature of the penis in normal men, those with erectile dysfunction (ED), those with semirigid penile prostheses (SRPPs), and those with inflatable penile prostheses (IPPs), and those before and after trimix injection to create a penile erection. A total of 68 patients were evaluated. Five patient groups were identified, including men with normal erectile function, with ED, with SRPPs, with IPPs, and following intracavernosal injection of trimix solution. Cutaneous glans temperature increased significantly by more than 2.2°C in the trimix-injected group compared with all other groups (P<0.001). Using cutaneous temperature measurements of the penis, patients with SRPPs had significantly lower cutaneous glans temperatures than normals (P<0.02), those in the ED group (P<0.04), and those in the IPP-deflated group (P<0.01). The mean temperature difference was 1.44±0.40°C. Using cutaneous temperature measurements of the penis, men with SRPPs have a colder glans as compared with men with normal erectile function, ED, IPPs, and those who have received an injection of trimix. Men with normal erectile function, ED, and IPPs did not have significant cutaneous temperature differences.
The penile prosthesis has maintained its importance as part of the urologist's armamentarium for the treatment of erectile dysfunction (ED). Since its introduction in the 1970s, the surgical technique of penile prosthesis implantation has evolved from placing a single silastic prosthesis in the pendulous part of the penis,1, 2 to the current intracorporeal placement.3
Although the design and function of the modern prosthesis has changed and improved, a persistent complaint that has been noted by both patients and their sexual partners is the subjective sensation of a cold glans penis in those men with a penile prosthesis.4, 5 Montsorsi et al5 reported the etiology of patient dissatisfaction with postoperative sexual activity following insertion of a semirigid penile prosthesis to be sensation of a cold glans penis in 24%. The purpose of this investigation was to evaluate whether an objective and observable difference in cutaneous temperature measurements of the penis exists between men with and without penile prosthetic implants.
Materials and methods
All procedures and methods of data collection were approved by the Institutional Review Board before commencement of the study. In all, 68 patients visiting an academic urology clinic were included in the study. The mean patient age was 51 y (median 52, range 30–81), including 18 (26%) with diabetes, 19 (28%) with hypertension, and 10 (15%) with both diabetes and hypertension. Five patient groups were identified, including 10 patients with normal erectile function (normal group), 35 with ED (ED group), 11 with semirigid penile prostheses (SRPP; AMS Dura-II Minnetonka, MN; SRPP group), 12 with inflatable penile prostheses (IPP; Mentor Corp., Santa Barbara, CA; IPP group), and eight patients, all with ED, who received an intracavernosal injection of trimix solution (10 mg papaverine, 0.4 mg phentolamine, 10 mcg PGE1), and who were monitored before and after the injection (trimix group), sustaining a penetration rigidity erection. All patients without a penile prosthesis completed the erectile function domain of the International Index of Erectile Function questionnaire (IIEF-6). Those patients with International Index of Erectile Function questionnaire scores of 26 or more (out of 30) were classified as normals. Those with International Index of Erectile Function questionnaire scores of less than 26 were classified as having ED. Data regarding the complaint of cold glans were not obtained in those subjects with penile prostheses to avoid confounding bias. All patients in the trimix group had ED.
Room temperature and oral temperatures were recorded. Cutaneous temperature measurements (Physitemp NTE-2A; Physitemp Instruments Inc., Clifton, NJ, USA) were obtained at eight locations on the penis, including the lateral aspects of the proximal, middle, and distal shaft and glans penis bilaterally, and on bilateral thighs. Proximal measurements were obtained 0.5 cm distal to the pubopenile junction, distal measurements were obtained 0.5 cm proximal to the glans, and middle measurements were obtained at the bisection between proximal and distal locations. The Physitemp NTE-2A records temperatures with accuracy to ±0.1°C within a range of 0–50°C. Three measurements were taken at each location, and the average of these three measurements was used for data analysis. Temperatures were recorded in the IPP group before and after inflation of the penile prosthesis to the erect state. Temperatures were recorded in the ED and normal groups in the flaccid state. Measurements were repeated in the trimix group after injection of 0.2 ml of Trimix and production of a penetration rigidity erection. In order to prevent alterations in cutaneous temperatures, physical stimulation in conjunction with Trimix injection was not used to optimize the erection. Temperature and age between groups were compared using a one-way analysis of variance for each location on the penis, and P-values were determined using Student's t-test. Subset analysis was performed between groups for those subjects with diabetes, with hypertension, and with both diabetes and hypertension.
The mean oral temperature±standard deviation of 36.6±0.5°C and room temperature of 24.1±1.4°C were not significantly different between groups. There was no correlation between severity of ED, as measured by the IIEF-6, and penile cutaneous temperatures. A significant difference in temperature between groups was identified for the glans penis location only. Glans penis cutaneous temperatures and results of comparisons of glans penis cutaneous temperatures between groups are shown in Table 1. The SRPP group had significantly lower cutaneous glans temperatures (mean difference, 1.44±0.40°C) compared with the normal, ED, and IPP-deflated groups. However, there was no significant difference in cutaneous glans temperatures between the SRPP group and the IPP-inflated groups, as shown in Table 1. Trimix-injected patients did have significantly higher cutaneous glans temperatures compared with all groups. The mean temperature difference between trimix-injected patients and the other groups was 2.92±0.49°C. A graphic representation of mean cutaneous temperatures by location for each group is shown in Figure 1. The mean ages in years for each group are as follows: normal, 39; ED, 47; SRPP, 63; IPP, 61; Trimix, 57. The age difference between the normal group and the SRPP, IPP, and Trimix groups was significant (P<0.05). There was no significant difference between repeated measurements at each location. There was no significant difference between left and right measurements for each group. There was no significant difference in cutaneous temperature measurements on subset analysis with regard to diabetes, hypertension, or both diabetes and hypertension.
Penile skin temperatures have been used in the evaluation of impotence and male erectile responsiveness to aging.6, 7 Intraurethral penile body temperature measurements have also been used for diagnostic purposes to suggest that a sublingual to intrapenile temperature difference of more than than 3°F points toward an arteriogenic cause,8 although there is no recent literature to support this claim. In men treated with prosthetic penile implants, both the patient and partner have reported noting a subjective temperature difference.4, 5 This study chose cutaneous temperatures as the end point in those men. Although a patient's sensation of temperature difference could result from cutaneous or penile body temperature differences, or both, the sensation of coldness as felt by the partner most likely results from appreciation of a cutaneous temperature difference.
The results show that the sensation of a cold penis by both patient and partner translates into a true cutaneous temperature difference of the glans penis in the patient with a SRPP. Although prior reports of a cold glans in patients with penile prostheses have been published,4, 9 this is the first study providing objective evidence to support that claim. However, this study did not show a significant temperature difference between patients with an IPP compared with normal men or with men with ED as measured in the flaccid state. Penile cutaneous temperatures have been used in prior reports to aid in the diagnosis of arteriogenic impotence.6, 7 There was no significant cutaneous temperature difference between the ED and normal groups, suggesting that cutaneous temperature measurements of the penis in the flaccid state are of limited value in the evaluation of ED. No significant difference was found comparing the right side with the left side in patients with ED, suggesting that cutaneous temperature measurements are of limited value in diagnosing laterality in men with unilateral arteriogenic impotence.
One of the most obvious differences between the SRPPs and IPPs is the amount and types of material used. The SRPP design, with a solid interior and silicone exterior, would be expected to have a larger heat capacity than that of the IPP. Heat capacity, defined as the amount of energy required to change the temperature of a substance by 1°C, is a physical property of a material, dependant in large part on the types and amount of material used to make the prosthesis. Although the incidence and prevalence of the cold glans are not known, considerations for future design may be able to exploit differences in the heat capacity of materials to produce an SRPP that does not cause or allow a reduction in glans temperature. The alterations in blood flow resulting from replacement of cavernosal tissue with a solid device is likely another important factor, in addition to the heat capacity of the SRPP, that contributes to the lower observed cutaneous temperatures. Of interest, although a significant temperature difference was demonstrated between the SRPP and IPP-deflated groups, this significance was lost when the IPP was inflated. Decreased blood flow by way of compression of cavernosal and surrounding tissue by the penile prosthesis after being inflated may contribute to the observed difference.
Among the groups in which a pharmacological erection was not produced (normal, ED, IPP-deflated, and IPP-inflated groups), cutaneous temperature measurements were not significantly different, with the exception of the SRPP group. The temperature curve shows a declining trend as measurements were obtained from a proximal to a distal location on the penis, with a temperature difference from the proximal penis to the glans of 1.9°C for the normal, ED, and IPP groups combined. Differences shown between the trimix group after injection and all other groups likely result from increased blood flow to the glans penis after the production of a pharmacological erection. As visible in Figure 1, the temperature curve approaches a flat line moving from the proximal to distal penis after the injection of trimix. This graph suggests that, in men without a penile prosthesis, the increased blood flow during an erection is responsible for the change in temperature observed. One report evaluating the effect of increased blood flow on cutaneous temperature measurements in a patient with hypervascularity of the penis after arterialization of the deep dorsal vein showed a cutaneous temperature increase of 4.2°C after revascularization, with subsequent decrease to pre-revascularization values after ligation.10 This confirms the expected effect of increased blood flow on penile cutaneous temperatures.
The lack of glans engorgement noted in many men with penile prostheses may lead to the perception of a cold glans by both patient and partner. Although one cannot assume that a pharmacological erection would produce the same temperature changes as a physiological erection, it is likely that the cutaneous glans temperature in a person with normal erectile function would also be significantly higher during erection compared with groups without glans engorgement.
As previously stated, Montsorsi et al5 reported the etiology of patient dissatisfaction with postoperative sexual activity following insertion of a semirigid penile prosthesis to be sensation of a cold glans penis in 24%. A recent study examining the effect of pharmacologically induced glans engorgement in men with penile prostheses showed improved satisfaction with glans engorgement, although temperature change, or perception of a temperature difference, was not evaluated in that study.11 Evaluation of cutaneous temperature measurements during glans engorgement in men with penile prostheses can provide insightful information on the effect of glans engorgement and increased blood flow on penile cutaneous temperatures.
This study verifies the observation through cutaneous temperature measurements of the penis that men with a semirigid penile prosthesis do in fact have a colder glans as compared with men with normal erectile function, erectile dysfunction, an inflatable penile prosthesis, and those who have received an injection of trimix. In the flaccid state, men without penile prostheses did not have significant temperature differences, compared with men with normal erectile function, ED, and IPPs in the deflated state. Production of a pharmacological erection with trimix results in a significant rise in cutaneous glans temperature of more than 2.2°C.
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