Technique of Traction-free Nerve-sparing Robotic Prostatectomy

Delicate Tissue Handling by Real-Time Penile Oxygen Monitoring

A Tewari; A Srivastava; P Sooriakumaran; S Grover; P Dorsey; R Leung

Disclosures

Int J Impot Res. 2012;24(1):11-19. 

In This Article

Abstract and Introduction

Abstract

It is postulated that intraoperative injury to the cavernosal nerves results in hemodynamic and histologic changes within the penis, which manifest clinically as ED. We hypothesize that nonneuronal cause, such as vascular insults due to intraoperative tissue handling, may also have a minor but definite role in penile ischemia and consequent postoperative sexual dysfunction. Between May 2008 and July 2008, 64 patients were enrolled in the study (group 1). Following sterilization, the Odissey Tissue Oximeter probe was placed on the shaft of the penis, 2 cm from its base. The patient underwent continuous penile tissue saturation monitoring. Surgical dissection was altered whenever the oxygen saturation alarm went off until it was restored to ≥85%. In addition, 192 patients, matched for age, preoperative prostate-specific antigen, clinical stage, baseline sexual function, Charlson comorbidity index and nerve-sparing status operated between October 2007 and July 2008, formed the control group (group 2). These patients did not have any intraoperative tissue oxygenation monitoring. Opening of the endopelvic fascia and steps of nerve sparing were associated with significant drops in oxygen levels, especially if done using torque. Drop in oxygen levels were also noted whenever excessive traction was applied on the Foley catheter, seminal vesicles or prostate during apical dissection. We deliberately modified our surgical steps to make surgery more traction free. A significantly higher percentage of group 1 patients with bilateral nerve sparing had no ED compared with group 2 patients at 6 weeks (24.5% vs 10.4%; P = 0.014) and 52 weeks (83.7% vs 68%; P = 0.029). Overall, 93.9% of patients in study group had Sexual Health Inventory for Men (SHIM) score of ≥17 (mild to no ED) at 1 year compared with 78.4% of patients in the control group.We demonstrated that avoidance of ischemic stress, aided by intraoperative penile oxygenation monitoring, may help surgeons improve their technique and thus functional outcomes in patients.

Introduction

Radical prostatectomy (RP) is the most common treatment for localized prostate cancer, with 60 000– 80 000 American men undergoing this procedure annually.[1] Sexual dysfunction is the most common long-term adverse effect of RP.[2] Published literature has reported that anywhere between 30% and 83% of men are incapable of an erection sufficient for penetration following RP (http://www.icer-review.org/index.php/Download-document/78-Executive-Summary-Active-Surveillance-and-Radical-Prostatectomy-Final-Appraisal.html). The nerves responsible for erection are intimately associated with the prostate.[3] Numerous authors have demonstrated that preservation of the nerves surrounding the prostate can improve return of erectile function following RP;[4–6] however, rates of return of sexual function vary widely among individual surgeons and institutions.[5,7]

The pathophysiology of ED following RP is believed to be a result of thermal, mechanical and vascular insults to the nerves responsible for erectile function and the penis itself.[8,9] Delicacy of neurovascular tissue handling and avoidance of traction have been proposed as strategies for minimizing nerve damage.[10] Inadvertent traction on the delicate neurovascular tissue can cause stretch-induced axonotmesis in which axons over long segments of nerve are disrupted, whereas supporting structures (including endoneurium) are intact. Traction also disrupts and occludes the small-sized arteries that are traveling with the nerves (vasa nervorum) to supply distal structures such as pelvic muscles, cavernous tissue, external urethral sphincter and the nerves themselves.[11,12] Thus, traction can cause delay in functional recovery by either neural or ischemic mechanisms.

Traction-free nerve preservation can be difficult to achieve on a robotic platform because of the loss of haptic feedback. We hypothesized that if we could monitor tissue oxygenation in the neural tissue and penis, it may serve as a surrogate for significant traction on this important tissue. We also hypothesized that real-time intraoperative feedback regarding tissue oxygenation levels could aid surgeons in making slight alterations in surgical technique to limit traction and avoid ischemia.

Commercially available tissue oxygenation probes have been utilized during plastic surgical procedures as well as laboratory penile perfusion studies.[13,14] We have used such a device to evaluate intraoperative penile tissue oxygenation levels as a surrogate for identifying traction. This has allowed us to modify our technique to avoid such traction and the consequent fall in tissue oxygenation levels. Presented herein is our traction-free operative technique, as well as the effects of penile oxygenation monitoring on postoperative sexual and urinary continence outcomes in patients undergoing robotic prostatectomy by a single surgeon.

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