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Laser prostatectomy has found renewed interest among urologists and is being conducted in several centers. Based on initial experience, it promises to replace conventional TURP in the very near future. The neodymium: yttrium-aluminum-garnet (Nd-YAG) laser, holmium laser, and potassium-titanyl-phosphate (KTP) laser are commonly used. These lasers produce varying degrees of coagulation and vaporization of prostate tissue. The main advantages over conventional TURP include minimal blood loss (as little as 50 to 70 mL) and minimal fluid absorption, which should nearly eliminate these two major complications of TURP; however, other potential complications are introduced, including coagulation through the prostatic fossa and sloughing of prostatic debris in the postoperative period, with subsequent urinary obstruction and urinary retention.[148] [149] [150] [151] [152] Protective eyewear should be used, as well as a means to evacuate the smoke plume. [153] In critically ill patients, caudal anesthesia has been successfully used for laser prostatectomy because the use of continuous irrigation combined with minimal bleeding obviates the need for copious irrigation and minimizes bladder distention.[154]
In a systematic review of randomized, controlled trials evaluating the efficacy and safety of laser prostatectomy techniques versus TURP for symptomatic benign prostatic obstruction, the authors observed that TURP provided slightly greater improvement in urinary symptoms and flow. Laser procedures resulted in fewer transfusions and strictures and shorter hospitalizations. Reoperation was required more often after laser procedures.[155]
Cryosurgery has proved to be technically complex and has not attained much popularity. Microwave ablation of the prostate is another promising technique that can be performed on an outpatient basis under local or sacral blockade. Classic TURP, however, still remains the gold standard.[156]
Laser lithotripsy is used for ureteral stones that are low in the ureter and not amenable to extracorporeal shock wave lithotripsy (ESWL). A pulsed dye laser is generated with a laser beam of 504-nm wavelength passing through an organic green dye.[157] This laser beam is easily absorbed by the stones, and pulsatile energy is released that causes disintegration of the stones. The beam is carried over a bare wire passed through a rigid ureteroscope, which is longer and more pointed than a cystoscope, so the risk of ureteral perforation exists. General anesthesia should be maintained to avoid patient movement. For regional anesthesia, a spinal level of T8 to T10 is required. The bare laser wire is sharp and can cause mucosal injury to the ureter. However, these lasers are not well absorbed by red blood cells or other tissues, which provides safety against tissue coagulation or thermal injury. Because the laser beam is reflective, the user, other personnel, and the patient should wear protective eyeglasses. Some hematuria always occurs; hence, good intravenous hydration is recommended.[157]
Pelvic lymph node dissection used to be the most commonly performed laparoscopic urologic procedure in adults. However, in recent years, the use of laparoscopy has been extended to other urologic procedures such as varicocelectomy, hernia repair, adrenalectomy, percutaneous stone retrieval from the renal pelvis or ureter, nephrectomy, and radical prostatectomy.
For radical prostatectomy, the objectives of laparoscopic surgery are to reduce perioperative morbidity in comparison to conventional surgery and allow a more precise operative procedure. Indeed, the quality of surgery can be improved by better visualization of the operative site as a result of optical magnification and the maneuverability of the laparoscope, which provides a hitherto unobtainable anatomic view. The laparoscopic approach not only improves the postoperative course but also allows better preservation of periprostatic vascular, muscular, and neurovascular structures.[158]
Although all the conventional complications and concerns associated with laparoscopy are applicable to urologic procedures (see Chapter 57 ), two unique problems are also identified. First, because the urogenital system is mainly retroperitoneal, the large retroperitoneal space and its communications with the thorax and subcutaneous tissue are exposed to the insufflated carbon dioxide. Subcutaneous emphysema is frequent in these patients and may extend all the way up to the head and neck.[159] The upper airway is at risk for compromise in the most severe cases because of pharyngeal swelling secondary to submucous carbon dioxide. This complication should be kept in mind before extubation of these patients. Second, the procedures tend to be lengthy, thus allowing
ESWL was first conducted in Munich, Germany, in 1980, and in 1984 the lithotripter was introduced into the United States. Since then, ESWL has become the treatment of choice for disintegration of urinary stones in the kidney and upper part of the ureter. The first clinical model of the lithotripter introduced into common practice (Dornier HM-3) used a water bath in a steel tub and a metal gantry chair to support the patient suspended in a sitting position. This first-generation lithotripter is still used in many institutions and presents complex challenges of immersion physiology and monitoring difficulties. Second- and third-generation lithotripters (Siemens, Lithostar, Wolf Piezolith, Dornier HM-4, MFL 5000, etc.) have since been developed and have become the mainstay of clinical practice. They have evolved mainly in the direction of eliminating the water bath and producing a pain-free lithotripter. However, all lithotripters share similar technologic principles in having three main components: (1) an energy source, most commonly a spark plug (alternatively, an electromagnetic membrane or piezoelectric elements may be used in some machines); (2) a system to focus the shock wave, such as ellipsoid or reflecting mirrors; and (3) a system to visualize and localize the stone in focus, namely, fluoroscopy or ultrasound.[160]
The Dornier HM-3 lithotripter, the gold standard, uses a water bath for treatment and x-ray equipment to localize the stone. These components are contained in the all too familiar steel tub. The patient is strapped in a gantry chain in a semisitting position with support under the shoulders and hips and the flank exposed. The chair is hoisted to the ceiling, travels on ceiling rails, and is then slowly lowered into the tub. The patient is immersed in water up to the clavicles. An electrode (or spark plug) is placed in the water at the base of the tub in an ellipse and is connected to a generator that supplies 16 to 24 kV of electricity. The electrical energy creates a spark across the gap in the electrode with the generation of a loud noise, intense heat, and explosive vaporization of water. The sudden expansion of air bubbles thus created sets up a pressure wave (shock wave) with distinct mechanical and acoustic properties. The shock wave is focused by the ellipse to a focal point called the Fz focus (the tip of the electrode is the first focus). The shock wave travels through water and body tissues without significant localized dissipation of energy because the acoustic impedance of the two media is similar. However, when the shock wave arrives at the entry surface of the stone, it encounters a sudden change in impedance that causes it to release compressive energy on the magnitude of several atmospheres. Similarly, when the wave exits on the opposite surface of the stone, an interface is again encountered, and shock wave energy is released in a blast. Repeat applications cause the stone to disintegrate. Shock wave energy is most concentrated in the Fz focal zone and rapidly decreases beyond it.[161] [162] [163] These physical properties of the shock wave must be understood to prevent injury to tissue or to any prostheses and to ensure that the shock wave passes unimpeded to its focal point for the most effective lithotripsy results. The following discussion elucidates this principle further.
For shock waves to be most effective, the stone should remain in the Fz focus during treatment.[154] Pressure energy measurements show an exponential decrease beyond this small focal zone. The kidneys and hence the kidney stone follow the up-and-down movements of the diaphragm during respiration. It is therefore likely that the stone will move in and out of focus during respiration. This issue has been studied, and innovative ventilatory techniques have been tried to minimize stone movement during ventilation.[164] [165] [166] [167] [168] [169] High-frequency jet ventilation has been shown to decrease stone movement and has been claimed to increase the efficacy of the treatment.[170] High-frequency conventional ventilation using fast respiratory rates and small tidal volumes has also been effective in decreasing stone excursion during respiration.[169] However, other data[171] and wide clinical experience with success rates of lithotripsy do not support or justify the routine use of these techniques, which add their own complexity and complications to the procedure.[169] Furthermore, regional anesthesia and analgesia-sedation are frequently used for lithotripsy, in which case spontaneous ventilation is the only option. Studies in sedated patients with intercostal blocks and local infiltration anesthesia have documented that stone movement with spontaneous respiration is mainly restricted to the Fz focal zone during ESWL.[172] Therefore, conventional ventilation during general anesthesia or spontaneous respiration during regional anesthesia is acceptable for lithotripsy. Occasionally in an awake patient, one may have to carefully titrate sedation or, if the patient is under general anesthesia, may need to manipulate respiratory parameters to decrease abnormally large stone movement.
For effective stone disintegration, shock waves should reach the stone with very little loss of energy. Therefore, the flank area should be kept free of any medium that would provide an interface for the dissipation of shock wave energy. For example, nephrostomy dressings should be removed and the nephrostomy catheter should be taped clear of the blast path. If epidural anesthesia is used, great care should be taken to tape the catheter and the gauze well clear of the blast path in the flank on the side being treated. Pandit and associates[173] noted an unusually high rate of failure of lithotripsy in their patients receiving epidural fentanyl analgesia. They discovered that the foam tape placed to secure the epidural
Except when piezoelectric lithotripters or lithotripters with very low shock wave energy are used, the procedure is painful and requires some form of anesthesia. Shock waves produce sharp stinging pain at the entry site in the flank along with a sensation of deep visceral pressure discomfort.
Although shock waves pass through most tissues relatively unimpeded, they do cause tissue injury, the extent of which depends on the tissue exposed and the shock wave energy at the tissue level. For example, skin bruising and flank ecchymoses are not uncommon at the entry site. Painful hematoma in the flank muscles may occur. Hematuria is almost always present at the end of the procedure and results from shock wave-induced endothelial injury to the kidney and ureter. Adequate hydration is necessary to prevent clot retention. A decrease in postoperative hematocrit should arouse suspicion of a large perinephric hematoma. Punctate hemorrhages have been observed in the stomach and bowel, and this injury might be responsible for abdominal distention, nausea, and vomiting in some patients.
Lung tissue is especially susceptible to injury by shock waves. Air trapped in alveoli presents the classic water (tissue)-air interface to the shock wave and causes dissipation of energy with alveolar rupture and hemoptysis. Massive hemoptysis and death from pulmonary damage have been reported in laboratory animals after a single exposure of the thorax to a shock wave.[174] Shock wave-induced hemoptysis in a child and a pulmonary contusion with life-threatening hypoxemia in an adult have been reported.[175] [176] Children are more likely to suffer pulmonary damage from shock waves because of the shorter distance of the lung bases from the kidneys than in adults. It is recommended that a Styrofoam sheet or Styrofoam board be placed under the back in children to shield the lung bases from shock waves during ESWL.[175] [176] [177]
Shock wave-induced cardiac arrhythmias occur in 10% to 14% of patients undergoing lithotripsy despite the fact that shock waves are synchronized with the patient's ECG and are delivered in the refractory period of the cardiac cycle.[178] [179] [180] These arrhythmias are believed to be due to mechanical stress on the conduction system exerted by the shock waves. Even though the shock waves are produced by electrical energy, the intricate grounding system of the lithotripter is such that the current density reaching the myocardium is minuscule in comparison to other sources (e.g., cardiac pacemakers). Hence, current-induced arrhythmias are unlikely. As mentioned previously, arrhythmias do occur frequently and are due to the mechanical effects of shock waves. Atrial and ventricular premature complexes, atrial fibrillation, and supraventricular and ventricular tachycardia have been reported.[178] [179] [180] ECG artifacts are also common. Artifacts and arrhythmias usually disappear once the lithotripsy is stopped. Occasionally, however, arrhythmias may persist and require treatment.
Water immersion with the Dornier HM-3 lithotripter produces significant changes in the cardiovascular and respiratory systems ( Table 54-13 ). Cardiovascular changes include an increase in central blood volume with an increase in central venous and pulmonary artery pressure.[181] [182] [183] [184] [185] [186] Weber and colleagues[181] observed that increases in central venous pressure and pulmonary artery pressure were directly correlated with the depth of immersion. On the other hand, the sitting position, together with general or epidural anesthesia, would tend to cause peripheral pooling and decreased venous return. A 1987 study noted a decrease in cardiac output and an increase in systemic vascular resistance during ESWL under general anesthesia.[186] Respiratory changes with immersion up to the clavicles are significant: functional residual capacity and vital capacity are reduced by 20% to 30%, pulmonary blood flow has been shown to increase,[187] [188] and tight abdominal straps and the hydrostatic pressure of water on the thorax impart a characteristic shallow, rapid breathing pattern.[188] Ventilation-perfusion mismatch and hypoxemia are thus more likely. The renal effects of immersion include diuresis, natriuresis, and kaliuresis. A decrease in antidiuretic hormone and renal prostaglandins occurs. The temperature of the bath water can cause profound changes in the patient's temperature. This heat transfer is further augmented by the vasodilation produced by general or epidural anesthesia. Both hypothermia and hyperthermia have been reported.[189] [190]
Anesthetic regimens successfully used for lithotripsy include general anesthesia, epidural anesthesia, spinal anesthesia, flank infiltration with or without intercostal blocks, and analgesia-sedation, including patient-controlled analgesia.[191] [192] [193] [194] [195] [196] [197] [198] [199] [200] [201] [202] General anesthesia offers the advantages of rapid onset and control of patient movement. Ventilatory parameters can be controlled to decrease stone movement with respiration. Extra long circuit tubing and monitoring cables are required. Disadvantages include a likelihood of positional injury and the possible need to transport an anesthetized patient to other locations if adjunctive procedures become necessary.
Epidural anesthesia offers the advantage that the patient is awake
and can help with transfer in and out of the gantry chair, thus reducing the likelihood
of injury. With epidural anesthesia and use of the loss of resistance to air to
identify the epidural space, only the smallest amount of air necessary should be
injected. Air in the epidural space will provide an interface and cause dissipation
of shock wave energy and local tissue injury.
| Cardiovascular | Increased | Central blood volume |
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Central venous pressure |
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Pulmonary artery pressure |
| Respiratory | Increased | Pulmonary blood flow |
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Decreased | Vital capacity |
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Decreased | Functional residual capacity |
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|
Decreased | Tidal volume |
|
|
Increased | Respiratory rate |
The main disadvantage of epidural anesthesia is its slow onset. Spinal anesthesia offers a reasonable alternative with its rapid onset. However, the incidence of hypotension (the patient is in a sitting position for treatment) is higher. In one series, the incidence of hypotension with general, epidural, and spinal anesthesia was 13%, 18%, and 27%, respectively.[205] Local anesthetic infiltration of the flank with or without intercostal blocks provides adequate anesthesia when combined with intravenous sedation and avoids hypotension. [192] Intravenous analgesiasedation in various combinations has been successfully used by many anesthetists.[194] [195] [196]
Second- and third-generation lithotripters offer many advantages. First, there is no water bath; hence all the problems of immersion are avoided. Second, they tend to use multifunctional tables that allow other procedures such as cystoscopy and stent placement to be accomplished without moving the patient off the table. Third, the shock waves are focused, so they cause less pain at the entry site. With the exception of the piezoelectric lithotripters (Wolf, EDAP, Diasonic) and use of the lowest energy levels with the other lithotripters, ESWL is not pain free, and intravenous analgesia-sedation is the mainstay of anesthesia with these newer lithotripters. Other incidental interventions such as cystoscopy, stone manipulation, or stent placement will alter anesthetic requirements. Many of these newer lithotripters have a much smaller focal zone for the shock waves. Hence, it is even more imperative with these lithotripters that adequate analgesia and sedation be provided so that stone excursion with respiration is limited to the focal zone. Most analgesia-sedation combinations are adequate. Even patient-controlled analgesia with alfentanil and a combination of propofol and alfentanil has been used.[206] [207] [208]
Pregnancy, untreated bleeding disorders, and abdominally placed pacemakers are the only absolute contraindications to lithotripsy. Women of childbearing age must have a pregnancy test that is documented to be negative before lithotripsy. Standard tests of coagulation such as the platelet count, prothrombin time, and partial thromboplastin time should be obtained. Other conditions that were previously labeled as absolute contraindications are no longer believed to be so, provided that appropriate precautions are taken. These conditions include pacemakers, automatic implanted cardioverter-defibrillators (AICDs), abdominal aortic aneurysm, orthopedic protheses, and obesity.
Patients with pacemakers can be treated safely if the pacemaker is pectorally placed and the following precautions are observed.[209] [210] [211] [212] Pacemaker programmability should be established before the treatment, and a programmer should be available to switch the pacemaker to a nondemand mode should the shock waves interfere with pacemaker function. Alternative means of pacing should be available. Although most pacemakers located pectorally are at a safe distance from the blast path, some may be damaged. Weber and coworkers[209] examined 43 different pacemakers and found that 3 were affected. Dual-chamber pacemakers tend to be more sensitive to interference. Treatment must be started at the lowest energy level and gradually increased while observing pacemaker function.
Manufacturers of AICDs and lithotripters generally consider an AICD a contraindication for lithotripsy. Patients with AICDs have been treated successfully with lithotripsy, however.[211] Transvenous AICDs are less of a concern than the older abdominally implanted defibrillators. AICD devices should be shut off immediately before lithotripsy and then reactivated immediately after treatment.
Patients with small aortic aneurysms have been treated safely provided that the stone is not close to the aneurysm. Orthopedic prostheses such as hip prostheses and even Harrington rods are not a problem if they are not in the blast path, which is usually the case. Positioning of obese patients may sometimes be problematic. Not only do extremely obese patients present anesthetic challenges related to obesity, but also focusing of the stone may be extremely difficult in the very obese, and it is not uncommon for the procedure to be abandoned in these patients because of an inability to bring the kidney stone into the Fz focal zone. It is therefore prudent for focusing of the stone to be attempted before administering any anesthetic in this high-risk population. With the newer lithotripters, some of these patients may have to be placed prone, a position that they may not be able to tolerate safely.
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