The utility of intravenous ketamine for the management of intraoperative penile erection: a retrospective single-center analysis of endourological surgeries over a 4-year

Penile tumescence resulting in partial or total erection under anesthesia at the time of endoscopic urological surgery is a relatively infrequent but challenging condition with reported incidence of 0.1 to 2.4% [1‐4]. While the etiology is unclear, it generally follows the local stimulation of the penis during skin preparation or instrumentation [3, 5]. Intraoperative penile erection may lead to delay or cancellation of the surgery by impeding urological instrumentation or safely reaching the prostate or bladder together with the greater risk of complications such as bleeding, urethral trauma and stricture formation [2, 4, 6].

To date, many pharmacological treatments to produce detumescence have been proposed, such as intracavernous injection of ephedrine, phenylephrine, metaraminol, noradrenaline and adrenaline [4, 7‐10] or intravenous injection of ketamine [6, 11‐13], dexmedetomidine [5], terbutaline [14] and glycopyrrolate [15].

However, each of these has shown varying levels of efficacy and safety with no consensus a fully effective treatment protocol without side-effects [4‐6].

The aim of this paper was to present the prevalence of intraoperative penile erection in our endourological surgery practice and the utility of intravenous ketamine in the management of the condition.

The findings of this study revealed that of 402 endourology operations performed in our clinic over a 4-year period (2015–2019), 9 (2.2%) patients had a penile erection during endourological surgery with spinal anesthesia. Overall, 7 of 9 (77.8%) cases were successfully treated with intravenous ketamine (total dose ranged from 18.0 to 75.0 mg) administration, which resolved penile rigidity and the operation was completed within 91.7 min on average.

The overall prevalence of intraoperative penile erection under anesthesia has been reported to range from 0.1 to 2.4% [5], specifically at 0.34–3.5% for general anaesthesia, 0.11–0.3% for spinal anaesthesia and 1.72–3.8% for epidural anaesthesia [3‐5]. Hence, the prevalence of intraoperative penile erection in the current cohort of endourology patients seems to be consistent with previously reported rates for endourology procedures performed under spinal anesthesia.

Although the exact mechanism has not been clarified, penile erection under anesthesia is considered to be mediated by both psychogenic and refloxogenic stimulation [4, 14], while the latter is considered to be more common via the stimulatory effect of washing, touching and 6 7 instrumentation of the genital area on sacral root afferents [4]. Therefore, with the onset of penile erection post-urethroscope in 77.8% of the current study cases, these findings support the view that intraoperative penile erection generally follows local stimulation of the penis during skin preparation or instrumentation due to activation of sacral parasympathetic pathways eliciting an unopposed reflex response via an autonomic imbalance [3‐5]. In addition, all of the intraoperative penile erection cases in this cohort had received spinal anesthesia with T8-T10 blockage, in accordance with the higher prevalence of erections with blocks reaching higher than T8 and rarely with those lower than T12 [16].

Notably, while the condition has been considered to occur predominantly in younger males [3‐5], in the current cohort, the median age of patients with intraoperative penile erection was 69.0 years (range, 60.0–77.0 years), with the potential likelihood of treatment failure in older patients.

These findings demonstrated that the intravenous injection of ketamine was an effective and safe method for immediate relief of intraoperative penile erection with a high success rate. This supports the reported efficacy of ketamine, as a dissociative anesthetic, in the management of intraoperative penile erection in past studies [2, 6, 11‐13].

Moreover, in 7 of 9 cases, ketamine administration resolved penile rigidity enabling completion of the operation within an average of 91.7 min with no side-effects. This seems notable given the consideration of prolonged time to achieve flaccidity (range, 90 min^− 2 h) being the major disadvantage of intravenous ketamine treatment, together with the potential risk of hallucinations and unpleasant dreams in patients under concomitant spinal anesthesia [4, 11, 17].

Certain limitations to this study should be considered. First, due to the retrospective single 1 2 3 4 5 center design of the study, establishing the temporality between cause and effect seems difficult. Second, generalizing these findings to the whole endourology population is not 6 7 possible due to the relatively low sample size. Nevertheless, despite these certain limitations, given the paucity of solid information available in accordance with the rarity of the condition and the challenges regarding conduction of very large-scale studies to determine the benefits of any therapeutic intervention, these findings represent a valuable contribution to the literature.

In conclusion, the prevalence of intraoperative penile erection during spinal anesthesia for endourological surgery was 2.2% in our experience. These findings demonstrated that intravenous injection of ketamine is an effective and safe method for immediate resolution of intraoperative penile erection with a high success rate.