Absorption of irrigating fluid
Circulatory overload and hypoosmolality
Hyponatremia
Glycine and ammonia toxicity
Bladder perforation
Transient bacteremia and septicemia
Hypothermia
Bleeding and coagulopathy
TURP syndrome
The Surgical Procedure
The TURP procedure is performed through a resectoscope resting in the patient’s urethra by using an electrically powered cutting-coagulating metal loop to resect prostatic tissue in an orderly fashion. Care must be taken during prostatic tissue resection not to violate the prostatic capsule. If the capsule is perforated, large amounts of irrigation fluid may be absorbed into circulation and the periprostatic and retroperitoneal spaces [23, 24]. Capsular perforation occurs in approximately 2% of patients and might lead to symptoms in awake patients of restlessness, nausea, vomiting, and abdominal pain [9]. In cases where perforation is suspected, the procedure should be terminated as quickly as is safely possible along with the obtainment of hemostasis [9].
Bleeding is a common occurrence during TURP, but is usually easily controlled. Arterial bleeding is controlled by electrocoagulation; however, when large venous sinuses are opened, hemostasis might become difficult. If venous bleeding becomes uncontrollable, then the procedure should be quickly terminated, a Foley catheter should be inserted, and traction applied [23, 24]. Estimates of blood loss during TURP are usually inaccurate because of the mixing of shed blood with large amounts of irrigating fluid. Blood loss during TURP has been estimated to range from 2 to 4 mL/min of resection time or 20–50 mL/g of resected prostatic tissue [25]. Excessive bleeding necessitating intraoperative transfusion occurs in 2.5% of patients undergoing TURP [14].
Irrigation Solutions
The ideal irrigating solution for use during TURP should be isotonic, nonhemolytic, electrically inert, transparent, nonmetabolized, nontoxic, rapidly excreted, easily sterilized, and inexpensive [26, 27]. Such a solution does not exist and of the currently available solutions each has its own potential complications. Initially, the solution of choice was distilled water because it was nonconductive and transparent. However, when absorbed into the circulation, it caused massive hemolysis, hyponatremia, rare renal failure, and central nervous system (CNS) symptoms [23, 28].While solutions of normal saline or Ringer’s lactate are isosmotic and would be tolerated if absorbed into the circulation, they are highly ionized and would cause dispersion of the high-frequency current from the resecting loop. These issues eventually led to the introduction of nonconductive and nonhemolytic solutions, such as glycine, Cytal® (a combination of 2–7% sorbitol and 0.54% mannitol), sorbitol, mannitol, glucose, and urea (Table 3.2) [23, 24]. All these solutions allow for electrocautery resection and in order to maintain transparency are prepared moderately hypotonic [10, 24].
Table 3.2
Osmolality of commonly used irrigation solutions
Solution | Concentration (%) | Osmolality (mOsm/kg) |
|---|---|---|
Glycine | 1.5 | 220 |
Cytal | 178 | |
Mannitol | 5 | 275 |
Sorbitol | 3.5 | 165 |
Glucose | 2.5 | 139 |
Distilled water | 0 |
Though these irrigation solutions cause no significant hemolysis, excessive absorption can be associated with several perioperative complications, including circulatory overload, hyponatremia, and hypoosmolality. Solutes in the solutions may also cause adverse effects: glycine – cardiac, neurologic, and retinal effects [24, 28, 29]; mannitol – rapidly expands intravascular volume leading to possible development of pulmonary edema in cardiac compromised patients [23]; sorbitol – metabolized to fructose and lactate may cause hyperglycemia and/or lactic acidosis [30]; and glucose – severe hyperglycemia in the diabetic patient [31]. Of these solutions, glycine and Cytal® are the most commonly used irrigating solutions worldwide [16].
TURP Syndrome
Signs and Symptoms of TURP Syndrome
The clinical presentation of TURP syndrome is multifactorial, initiated by excessive absorption of irrigating solution that affects CNS, cardiovascular, respiratory, and metabolic homeostasis. Clinical manifestations will vary depending upon severity and are influenced not only by the type of irrigation solution used but also by patient and surgical factors. Signs and symptoms (Table 3.3) may be vague, variable, and nonspecific, therefore compounding the diagnosis. TURP syndrome has been observed as early as 15 min after the start of surgery [32] up to 24 h postoperatively [33].
Table 3.3
Signs and symptoms of transurethral resection of the prostate syndrome
Cardiovascular and respiratory | Central nervous system | Metabolic | Other |
|---|---|---|---|
Hypertension | Restlessness | Hyponatremia | Hypoosmolality |
Dysrhythmias | Agitation | Hyperglycemia | Hemolysis |
Pulmonary edema | Confusion | Hyperammonemia | Acute renal failure |
Congestive heart failure | Nausea and vomiting | ||
Hypotension | Seizures | ||
Respiratory arrest | Coma | ||
Cardiac arrest | Blindness |
Early signs of TURP syndrome include fleeting prickling and burning sensations in the face and neck along with lethargy and apprehension [16]. Other early CNS effects include complaints of headache and restlessness together with a general sense of being unwell. Later symptoms include visual disturbances, confusion, seizures, and eventually coma [16]. These CNS disturbances have been attributed to hyponatremia, which occurs with the absorption of any type of irrigating solution, and hyperglycinemia and/or hyperammonemia if glycine is used [26]. It is thought that these CNS effects are caused not by water intoxication leading to hyponatremia, in itself, but by the acute decrease in serum osmolality that results in the development of cerebral edema [34, 35].
Cardiovascular and respiratory effects will eventually occur from volume overload and hyponatremia. Initially, acute hypervolemia will cause hypertension and bradycardia with possible progression to congestive heart failure, pulmonary edema, and cardiac arrest [36].
Absorption of Irrigating Solution
In almost every TURP, small amounts of irrigating solution will be absorbed through opened prostatic venous sinuses [29]. It is the excessive absorption of fluid that is the primary cause of TURP syndrome. Several factors may determine the amount and rate of fluid absorption: (1) the height of the irrigating fluid above the patient which affects hydrostatic pressure, (2) the amount of distension of the bladder by the surgeon, (3) the extent of opened venous sinuses, and (4) the length of time of resection [37]. While as much as 8 L may be absorbed during the procedure, the average rate of fluid absorption is 10–30 mL/min of resection time [23]. By comparing serum sodium (Na+) levels before and after the procedure, an estimation of fluid absorbed can be made by using the following equation:
where extracellular fluid (ECF) volume comprises 20–30% of body weight [24, 38].
Other methods though not commonly used to estimate fluid absorption include (1) ethanol monitoring method in which 2% ethanol is added to the irrigating solution and its level is measured in exhaled breath, which correlates with the amount of irrigating solution absorbed [39, 40]; (2) central venous pressure (CVP) method, which as irrigating solution is absorbed into the circulation, CVP will rise; however, CVP is affected by other variables in the procedure such as blood loss and intravenous fluid administration [19]; (3) gravimetry method which requires that the procedure be performed on a bed scale and relies on the assumption that any fluid absorption, taking blood loss and intravenous fluids into consideration, will be reflected with an increase in body weight [41]; and (4) transesophageal Doppler method to allow early detection of hypervolemia and associated hemodynamic changes [42].
Circulatory Overload, Hyponatremia, and Hypoosmolality
Rapid volume expansion occurs with excessive irrigation fluid absorption, which leads to circulatory overload. At first, hypertension and bradycardia will be observed and in patients with compromised cardiac function might progress to pulmonary edema and eventually cardiac arrest [36].
A prolonged period of hypotension may follow the initial hypertensive stage. Suggested mechanisms are that hyponatremia combined with hypertension causes a net water flux along osmotic and hydrostatic pressure gradients out of the intravascular space and into the pulmonary interstitium, causing pulmonary edema and hypovolemic shock [43–45]. Hypotension may also be caused by the release of endotoxins into the circulation along with the associated metabolic acidosis [19, 46].
The signs and symptoms of hyponatremia (Table 3.4) correlate with the severity and rate by which serum sodium concentration falls. Acute changes in serum sodium levels are more injurious than chronic hyponatremia [47]. Also, it is often difficult to separate symptoms of cardiovascular compromise secondary to hyponatremia from those caused by circulatory overload. Acute decreases in serum sodium levels to less than 120 mEq/L are associated with CNS symptoms and cardiovascular effects [24, 30]. Initially, restlessness and confusion may appear, and with continued decreases in serum sodium levels, symptoms progress to loss of consciousness and seizures [48]. Further rapid decreases in serum sodium levels will lead to hypotension, pulmonary edema, congestive heart failure, and electrocardiogram changes (Table 3.4). Eventually at levels near 100 mEq/L, respiratory and cardiac arrest may occur [48].
Table 3.4
Signs and symptoms of acute hyponatremia
Serum Na+ (mEq/L) | Central nervous system changes | Cardiovascular effects | Electrocardiogram changes |
|---|---|---|---|
<120 | Restlessness | Hypotension | |
Confusion | Pulmonary edema | ||
Congestive heart failure | |||
<115 | Somnolence | Widened QRS complex | |
Nausea | Ventricular ectopy | ||
ST segment increase | |||
<110 | Seizures | ||
Coma | |||
<100 | Respiratory arrest | ||
Cardiac arrest |
The CNS signs of TURP syndrome are thought to be caused by acute serum hypoosmolality, with a shift of intravascular fluid into the brain, and consequent cerebral edema. With the advent of modern solute-based nearly isosmotic irrigating solutions, the incidence of severe CNS disturbances has been reduced; however, CNS symptoms can still occur secondary to severe hyponatremia [34, 35].
Management of TURP Syndrome
A high index of suspicion for the development of the signs and symptoms of TURP syndrome must be present among the operative team. Based on the patient’s symptomatology, supplemental oxygenation, ventilation, and cardiovascular support should be initially provided; while at the same time, other treatable conditions such as diabetic coma, hypercarbia, or drug interactions should be considered [26]. The procedure should be terminated as rapidly as possible. Blood samples should be sent for analysis of electrolytes, creatinine, glucose, and arterial blood gases. A 12-lead electrocardiogram should be obtained [24, 30].
Treatment of hyponatremia and fluid overload is guided by the severity of the patient’s symptoms. If the serum sodium level is greater than 120 mEq/L and the symptoms are mild, then fluid restriction along with the administration of a loop diuretic, usually furosemide will usually return the serum sodium to normal levels. The recommended treatment for severe cases of TURP syndrome, serum sodium less than 120 mEq/L, is the intravenous administration of hypertonic saline. The 3% sodium chloride solution should be infused at a rate no greater than 100 mL/h, and the patient’s hyponatremia should be corrected at a rate no greater than 0.5 mEq/L/h [24, 49]. Cerebral edema and central pontine myelinolysis have been associated with rapid correction of hyponatremia with hypotonic saline [35, 50].
Other Complications of TURP
Glycine and Ammonia Toxicity
Glycine is a nonessential amino acid that is metabolized in the liver into ammonia and glyoxylic acid [28]. Glycine has subacute effects on the myocardium with the appearance of T-wave depression or inversions on electrocardiograms, and CK-MB isoenzymes may be elevated in some patients (without meeting the criteria for myocardial infarction) for up to 24 h after surgery [51]. Glycine has also been implicated as the cause of transient blindness in TURP patients. Centrally acting mechanisms, such as cerebral edema, may cause visual impairment, but these patients have normal pupillary light reflexes. In TURP patients with transient blindness the pupils are sluggish or nonreactive, suggesting a retinal effect. Glycine is an inhibitory neurotransmitter in the retina; and after absorption of a few hundred mL of 1.5% glycine irrigation, Hahn et al. demonstrated prolongation of visual-evoked potentials and deterioration of vision [52].
Early signs of ammonia toxicity, nausea and vomiting, usually occur within 1 h after surgery. Serum concentrations of ammonia greater than 100 μmol/L are associated with CNS signs and symptoms [29]. As ammonia levels increase, the patient may lapse into a coma lasting from 10 to 12 h and awaken when levels decrease below 150 μmol/L [24].
Bladder Perforation
Inadvertent perforation of the bladder during TURP occurs with an incidence of approximately 1% with most perforations occurring retroperitoneally (see also section on TURBT). The usual cause is surgical instrumentation or overdistension of the bladder with irrigating fluid. A decrease in the return of irrigating fluid is an early, but often overlooked, sign of perforation. As a significant volume of fluid accumulates in the abdomen causing abdominal distension, patients with a regional anesthetic may start to complain of abdominal pain and/or experience nausea and vomiting. If the perforation occurs intraperitoneally, symptoms are similar, develop sooner, and patient might complain of severe shoulder pain secondary to diaphragmatic irritation [24]. Intraperitoneal perforations require either open surgical repair or percutaneous drainage of the abdomen [5].
Transient Bacteremia and Septicemia
Since the prostate harbors a variety of bacteria, which can be a source of perioperative bacteremia via open prostatic venous sinuses, the prophylactic administration of antibiotics is recommended in TURP patients. The bacteremia is usually transient and easily treated with common antibiotic combinations. However, 6–7% of these patients will develop septicemia [14].
Hypothermia
Shivering and hypothermia may occur in TURP patients if room temperature irrigating solutions are used. This may be especially pronounced in elderly patients who have a reduced thermoregulatory capacity [30]. Using warmed irrigating solutions will decrease heat loss and shivering, and the concern that these solutions may cause increased bleeding secondary to vasodilation has not been shown to be of clinical importance [53, 54].
Coagulopathy
Abnormal bleeding after TURP occurs in less than 1% of cases [25]. Possible causes include dilution of platelets (dilutional thrombocytopenia) and coagulation factors by absorption of large amounts of irrigating solution and systemic coagulopathy. In TURP patients, systemic coagulopathy is probably caused by either primary fibrinolysis or disseminated intravascular coagulopathy. In primary fibrinolysis, a plasminogen activator released from the prostate converts plasminogen into plasmin, which then increases bleeding via fibrinolysis. Primary fibrinolysis may be treated with epsilon aminocaproic acid intravenously with a dose of 4–5 g during the first hour, followed by an infusion of 1 g/h [25]. Some clinicians believe that systemic absorption of prostatic tissue, which is rich in thromboplastin, will trigger the onset of disseminated intravascular coagulopathy depleting coagulation factors and platelets [25, 55]. Treatment is supportive with administration of fluid and blood products as needed [30].
Anesthetic Considerations for TURP
Spinal anesthesia has been long considered the anesthetic technique of choice for TURP [14]. Though cardiac morbidity and mortality after TURP were similar for general or regional anesthesia [56], spinal anesthesia allows the patient to remain awake and enables the anesthesiologist to detect the early signs and symptoms, e.g., mental status changes, of TURP syndrome or the extravasation of irrigating fluid. Restlessness and confusion are early signs of hyponatremia and/or serum hypoosmolality and may not be signs of inadequate anesthesia. The administration of sedatives or the induction of general anesthesia in the presence of TURP syndrome might mask severe complications and even lead to death [57]. Perforation of the prostatic capsule or bladder will lead to extravasation of irrigating fluid and might cause the awake patient to complain of abdominal pain and/or experience nausea and vomiting [24].
Whether regional or general anesthetic techniques influence blood loss during TURP is controversial. Several studies have reported decreased bleeding under regional anesthesia [58–60], while others found no significant difference [61–64]. In those studies that observed decreased bleeding with regional anesthesia, the authors theorized that regional anesthesia reduces blood loss not only by decreasing systemic blood loss, but also by decreasing central and peripheral venous pressures [23, 58–60]. However, by reducing CVP, spinal anesthesia may potentially allow for greater absorption of irrigating fluid than occurs with general anesthesia [65].
Another concern, especially since many of these patients are elderly, in the choice of regional versus general anesthesia for TURP is the incidence of postoperative cognitive dysfunction. In one small prospective study comparing spinal anesthesia with intravenous sedation to general anesthesia in elderly TURP patients, a significant decrease in cognitive function was noted in both groups after 6 h, but there was no difference in the perioperative mental function between the groups at 6 h or even after 30 days [66].
If a regional technique is chosen, a T10 sensory level is required to block the pain of bladder distension. Higher sensory levels may prevent the patient from feeling abdominal pain caused by perforation of the prostatic capsule [23]. Additionally, in order to block the sacral nerves, which provide sensory innervation to the prostate, bladder neck, and penis, spinal anesthesia is preferred over epidural anesthesia [30]. However, if a regional technique cannot be performed secondary to technical difficulty, concerns of whether an epidural will provide adequate sacral coverage, and/or patient refusal, then general anesthesia will be required. It is this author’s practice to then carefully monitor Na+ serum levels and irrigating solution deficits during a general anesthetic.
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