(1)
Vanderbilt University School of Medicine, Nashville, TN, USA
Keywords
Urological surgeryUrinary system anatomyRenal dysfunctionGenitourinary systemCystoscopyUreteroscopyTURBTTransuretheral resection of the prostate (TURP)Laser surgeryRadical prostatectomyRadical cystectomyNephrectomyRenal transplantationOrchiectomyOrchidopexyPenile surgeryExtracorporeal shock wave lithotripsyLithotomy positionFor maximum impact, it is recommended that the case study and questions found on page xxviii are reviewed before reading this chapter.
Key Learning Objectives
Learn the pertinent urinary system anatomy and physiology
Understand anesthetic management of common urologic procedures
Discuss common complications associated with urologic surgery
Anesthesia for urological surgery poses a special challenge for anesthesiologists since patients are often elderly and may have multiple co-morbidities, including renal dysfunction. The scope of the field is broad and ranges from outpatient cystoscopies to major oncological surgeries, so the type of anesthesia needed is variable.
Anatomy
It is critical for the anesthesiologist to be familiar with the anatomy of the genitourinary system in order to understand the technical aspects of the procedure. The kidneys are located retroperitoneally, between T12 and L4, surrounded by perirenal fat and contained within Gerota’s fascia. On gross examination, there is an outer cortex and an inner medulla, which contains calices that drain into the renal pelvis, and eventually taper into the ureter. The ureters run along the psoas muscles and cross the common iliac prior to entering the bladder. Innervation of the upper ureters is carried by sympathetic fibers that enter the cord at T10-L2 and innervation of the lower ureters is by parasympathetics at S2–S4. This innervation is important when one is administering anesthesia for stone extractions. The bladder holds 400–500 cc of fluid and receives its innervation from the hypogastric plexus (T11–12, S2–4) (Table 22.1).
Table 22.1
Spinal pain segments for the genitourinary system
Organ | Sympathetics | Pain pathways |
|---|---|---|
Kidney | T8-L1 | T10-L1 |
Ureter | T10-L2 | T10-L2 |
Bladder | T11-L2 | T11-L2 (bladder dome) S2–4 (bladder neck) |
Prostate | T11-L2 | T11-L2S2–4 |
Penis | L1 and L2 | S2–4 |
Scrotum | S2–4 | |
Testes | T10-L2 | T10-L1 |
The blood supply to the kidneys is via a single renal artery, which originates inferior to the SMA. There are, however, many normal anatomical variants in which multiple renal arteries are possible.
Patient Positioning
There are multiple patient positions utilized in urological surgery and the anesthesiologist must be aware that there are physiological changes that accompany these positions.
The lithotomy position (Fig. 22.1) is most commonly used for cystoscopies, transuretheral resection of prostate or bladder tumor (TURP or TURBT), or ureteroscopies. Placement in this position for greater than 2 h may be a risk factor for development of sensory neuropathies or rhabdomyolysis secondary to compartment syndrome. This position increases upward displacement of intra-abdominal contents, decreasing pulmonary compliance, forced residual capacity and vital capacity, and increasing atelectasis. Elevating the legs also increases venous return, cardiac output, and arterial blood pressure, but these changes may not have clinically significant manifestations.
Figure 22.1
Patient positioned supine in the lithotomy position (Used with permission. From Cataldo and Buess [7])
Placing the patient in the kidney rest position (also called the lateral flexed position) is preferred for better access during renal surgery. Often an axillary roll (usually a rolled towel) is placed between the table and upper chest to ensure that the brachial plexus is free from compression or injury. The lateral decubitus position has profound effects on creating ventilation–perfusion mismatch and causes dependent atelectasis. Hemodynamically, there is a decrease in systemic arterial pressure, cardiac output, and renal perfusion pressures.
Preoperative Assessment
A thorough preoperative assessment is critical in patients undergoing urological surgery and includes all standard preoperative questions including screen for smoking history, medications, cardiac history, and renal function. Lab abnormalities reflective of renal failure include presence of hematuria or proteinuria on urinalysis, elevation in blood urea nitrogen (BUN) and creatinine values, and impaired creatinine clearance. If the patient is found to be in renal failure, the anesthesiologist must discern whether the renal failure is acute or chronic, and determine the etiology: prerenal, intrinsic renal, or postrenal/obstructive.
During surgery, it is critical for the anesthesiologist to avoid nephrotoxic drugs, correct hypovolemia, dose drugs based on renal function, and monitor for causes of urinary outflow tract obstruction. The adult kidney demonstrates autoregulation, maintaining relatively constant rates of renal blood flow (RBF) and glomerular filtration rate (GFR) over a wide variety of mean arterial blood pressures. Anesthesia can result in decreases in RBF and GFR despite normal blood pressure, and decreases in blood pressure as a result of depression of myocardial activity and sympathetic tone.
Anesthetic Management
Cystoscopy/Ureteroscopy/TURBT
These procedures consist of inserting an endoscope to visualize and intervene upon the lower urinary tract. Indications are varied, and include evaluation of hematuria, need for biopsies, extraction of stones, treatment of strictures, excision of bladder tumors (TURBT), and placement of ureteral stents to relieve obstruction. The patient is usually placed in the lithotomy position and irrigating solution is necessary to optimize visualization and remove surgical debris from the field. Procedures tend to be brief, usually under 1 h, and there is minimal need for postoperative analgesia so short-acting opioids are adequate for pain control.
Anesthesia for these procedures can be highly variable and can range from local anesthesia with monitored anesthesia care/sedation to general anesthesia with an LMA. With the advent of the flexible endoscope, general anesthesia is no longer required for patient comfort for these surgeries except in the case of dilatation of the ureter, which is more stimulating. Occasionally, the surgeon will request muscle relaxation for surgery when working in close proximity to the obturator nerve. In these cases, an endotracheal tube is necessary to secure the airway. If a spinal or an epidural is used, surgery on the lower genitourinary tract mandates a T10 level or higher. These procedures are often outpatient surgical procedures, with discharge home a few hours following surgery. For this reason, general anesthesia is usually preferred to regional. However, a short-acting spinal anesthetic may be appropriate. Disadvantages of regional techniques include awaiting return of urination postoperatively and more dilation of venous sinuses causing a slightly increased risk of TURP syndrome (see section “Complications of Urologic Surgery” below).
TURP
Transuretheral resection of the prostate (TURP) is commonly done for benign prostatic hypertrophy, which can cause compression of the lower urethra and result in obstructive urinary symptoms. A cystoscope is inserted into the urethra and a resectoscope, which can coagulate and cut tissue, is inserted through the cystoscope to resect all tissue protruding from the prostatic urethra. This procedure requires continuous irrigation fluid as well, placing the patient at risk for TURP syndrome (see “Complications of Urologic Surgery”).
The patient is positioned in lithotomy and regional or general anesthesia can be used. If general anesthesia is used, muscle relaxation may be indicated or a deep level of anesthesia may be preferred. This will prevent coughing or movement, which may lead to prostatic capsule rupture. Advantages of general anesthesia include positive pressure ventilation, which can decrease the absorption of irrigant solution by increasing venous pressures. Regional anesthesia mandates a T10 level and offers the advantage of an atonic bladder along with the presence of awake patients, in whom TURP syndrome may be detected earlier.
Laser Surgery in Urology
Laser surgery in urology allows for treatment of condyloma acuminatum, interstitial cystitis, BPH, ureteral or bladder stricture, contracture or calculi, and superficial carcinoma of the urinary tract or external genitalia. Laser surgery allows for minimal blood loss and postoperative pain. The types of lasers include carbon dioxide, argon, and pulsed-dye lasers. Concern for ocular injury by lasers is paramount for the anesthesiologist during these procedures and eye protection must be worn by all OR personnel and the patient. Thermal injury by lasers may also be possible and can be avoided by limiting use to one operator and placing the device in standby to allow for cooling between uses. Inhalation of viral particles and smoke can also pose a safety threat; special laser masks that prevent small particles should be worn and the OR should be equipped with a smoke evacuation system.
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