Which electrolyte abnormality occurs during TURP-
Ans- B Hyponatremia Ref Introduction Trans Urethral Resection of Prostate (TURP) is the second most common surgical procedure (after cataract extraction) done in men over the age of 65 years. Advancement in technology has enabled the urologists to reach all corners of the urinary system using endoscopes, causing minimum trauma to the patient. Endoscopic procedures in the urinary system require the use of irrigating fluids to gently dilate the mucosal spaces, remove blood, cut tissue and debris from the operating field and enable better vision. In spite of the best of efforts to understand and prevent the various complications of endoscopic procedures, incidence of some of the inherent complications have remained the same and still daunt the urologists. Aberrations in the Central Nervous System (CNS), Cardio Vascular System (CVS) and other systems which manifest due to the absorption of irrigating fluids during TURP are together known as TURP Syndrome. Though it is called TURP Syndrome, this complication can occur during other endoscopic procedures also namely Uretero-Renoscopy (URS), Percutaneous Nephrolithotomy (PCNL), Trans Cervical Resection of Endometrium (TCRE), etc. Despite improvements in the current surgical and anesthetic management, 2.5 - 20% of patients undergoing TURP show one or more manifestations of TURP syndrome and 0.5% - 5% die perioperatively. Signs and Symptoms TURP syndrome may occur at any time perioperatively and has been observed as early as few minutes after surgery has started and as late as several hours after surgery has been completed. When under regional anesthesia, the patient characteristically complains of Dizziness Headache Nausea Tight feeling in the chest and throat Shortness of breath Restlessness Confusion Retching Abdominal pain Both systolic and diastolic blood pressures rise and the heart rate decreases. If not treated promptly, the patient may become cyanotic and hypotensive and go in for cardiac arrest. Some patients present with neurological symptoms. Initially they become lethargic and then unconscious. Their pupils dilate and react sluggishly to light. This may be followed by short episodes of tonic-clonic seizures leading to a state of coma. Under General Anesthesia (GA), the diagnosis of TURP Syndrome is difficult and often delayed. The usual signs are unexplained rise and then a fall in BP and refractory bradycardia. ECG changes such as nodal rhythm, ST changes, U waves and widening of QRS complexes may be observed. Recovery from GA and muscle relaxants may be delayed. Irrigation Solutions Irrigating fluids are used during endourological procedures for better vision. Ideally the irrigation solution should be isotonic, non hemolytic, electrically inert (so that diathermy can be used), non toxic, transparent, easy to sterilize and inexpensive. Unfortunately, a solution having all these qualities is not yet available. Electrolyte solutions such as normal saline or Ringer Lactate do least harm when absorbed into the circulation. However they cause dispersion of high frequency current from the resectoscope and hence abandoned. A variety of other irrigating fluids have been in use, each having its own merits and demerits. Sterile water: Though sterile water has many qualities of an ideal irrigating fluid, the disadvantage is its extreme hypotonicity, causing hemolysis, dilutional hyponatremia, shock and renal failure. Glycine 1.2%, 1.5%. 2.2%: Glycine, an endogenous amino acid has been suggested as a suitable irrigating fluid considering its many advantages, including the low cost, though not as cheap as sterile water. Glycine is isotonic with plasma only at a concentration of 2.2%, but the side effects of glycine at this concentration are more. The osmolality of 1.5% glycine is 230 mosm/1 compared to serum osmolality of 290 mosm/l and hence cardiovascular and renal toxicities can occur at this concentration also. Further lowering of the concentration of glycine can lead to more complications due to hypotonicity and hence cannot be used for irrigation purposes. The distinct advantage of 1.5% glycine over sterile water is its tendency to cause less hemolysis and renal failure. Mannitol 3%: Mannitol, though does not have the toxicities of glycine, drives water out of cells and may enhance circulatory overloading. The cost of mannitol is also higher compared to glycine. The elimination of mannitol through kidney will be decreased in patients with impaired renal function. Glucose 2.5% - 4%: This is not a widely used irrigating fluid since glucose produces tissue charring at the site of resection and associated hyperglycemia produced when glucose is absorbed into the circulation. It also causes stickiness of surgeons' gloves and instruments. Cytal: Cytal, a mixture of sorbitol 2.7% and mannitol 0.54% widely used in USA as an irrigating fluid, has not gained popularity in India due to its high cost and nonavailability. In the body, sorbitol is metabolised to fructose, which may present problems in a patient with hypersensitivity to fructose. Urea 1%: This produces urea crystallisation on the instruments during resection and hence not preferred. 1.5% glycine and sterile water are the most widely used irrigating fluids in urological endoscopic surgeries. Pathophysiology 1. Circulatory Overload The uptake of small amounts of irrigating fluids has been shown to occur during almost every TURP and TCRE , through the venous network of prostatic bed and endometrium respectively. Spontaneous leakage through Fallopian tube More Detailss increases fluid absorption during TCRE. The fluid absorption has been studied by the expired breath ethanol tests after the addition of ethanol up to a concentration of 1 % to the irrigating fluid. The uptake of I litre of fluid within one hour, which corresponds to an acute decrease in the serum sodium concentration of 5-8 mmols/l, is the volume above which the risk of absorption related symptoms is statistically increased. , The average rate of fluid absorption during TURP is 20 ml/min. Due to circulatory overload, the blood volume increases, systolic and diastolic pressures increase and the heart may fail. The absorbed fluid dilutes the serum proteins and decreases the oncotic pressure of blood. This, concurrent with the elevated blood pressure, drives fluid from the vascular to interstitial compartment causing pulmonary and cerebral edema. In addition to direct absorption into the circulation, a significant volume (upto 70%) of the irrigation solution has been found to accumulate interstitially, in the periprostatic and retroperitoneal spaces. For every 100 ml of fluid entering the interstitial compartment, 10-15 meq of sodium also moves with it. Though the duration of surgery has not been conclusively proved to be the determinant for the volume of fluid absorbed, morbidity and mortality were found to be definitely higher when surgery was prolonged over 90 minutes. Intravascular absorption correlates well with the size of the prostate, while interstitial absorption depends primarily on the integrity of prostatic capsule. Circulatory overload occurs when the weight of the gland is more than 45 grams. Another important factor that determines the rate of absorption of fluid is the hydrostatic pressure at the prostatic bed. This pressure depends on the height of irrigating fluid column and the pressure inside the bladder during surgery. The ideal height of irrigating fluid is 60 cm so that approximately 300 ml. of fluid is obtained per minute during resection for good vision. 2. Water Intoxication Some patients with TURP syndrome present symptoms of water intoxication, a neurological disorder caused by increased water content of the brain. The patient becomes first somnolent and then incoherent and restless. Seizures may also develop leading on to coma in decerebrate position. There will be clonus and positive Babinski responses. Papilloedema, with dilated, sluggishly reacting pupils can occur. The EEG will show low voltage, bilaterally. The symptoms of water intoxication appear when serum sodium level falls 15 - 20 meq/l below normal level. 3. Hyponatremia Sodium is essential for proper function of excitatory cells, particularly those of heart and brain. Several mechanisms lead to hyponatremia in TURP patients. ,,, Dilution of serum sodium through excessive absorption of irrigation solution. Loss of sodium into the stream of the irrigation fluid from the prostatic resection site. Loss of sodium into pockets of irrigation solution accumulated in the periprostatic and retroperitoneal spaces. Larger amounts of glycine stimulate the release of atrial natriuretic peptide in excess of that expected by the volume load, which further promote natriuresis. The symptoms of hyponatremia are restlessness, confusion, incoherence, coma and seizures. When serum sodium falls below 120 meq/1, hypotension and reduced inyocardial contractility occur. Below 115 meq/1, bradycardia and widening of QRS complexes, ventricular ectopics and T wave inversion occur. Below 100 meq/1 generalised seizures, coma, respiratory arrest, Ventricular Tachycardia (VT), Ventricular Fibrillation (VF) and cardiac arrest occur. Sodium requirement is calculated by the following formula: Sodium Deficit = Normal serum Na - Estimated serum Na x Volume of body water (Body water is usually 60% of body water) 4. Glycine Toxicity Excess of glycine absorbed into circulation is toxic to heart and retina and may lead to hyperammonemia. Experimentally glycine has been found to reduce the vitality and survival of isolated cardiomyocytes. In patients, glycine 1.5 % has been associated with subacute effects on the myocardium, manifested as depression or inversion of the T wave on the electrocardiogram 24 hr after surgery. Absorption exceeding 500 ml has been shown to double the long-term risk of acute myocardial infarction. This may be one of the reasons for the higher long-term mortality after transurethral versus open prostatectomy, which has been a debate among urologists for some years. TURP seems to depress myocardial function, particularly when the operative duration exceeds 1 hr and when glycine is used at room temperature. About 0.5% of patients develop acute myocardial infarction during TURP, though transient myocardial ischemia has been detected during 20% of TURPs. Dilutional hypocalcemia has also been implicated as a source of acute cardiovascular disturbances when glycine is absorbed.,However calcium is restored more rapidly, probably due to mobilisation of calcium from bone tissues. Glycine is known to be a major inhibitory neurotransmitter in the spinal cord and in the brain stem, probably acting in the same manner as gamma amino butyric acid on the chloride ion channel. Too high a concentration may therefore cause severe depressant effect on the CNS and visual disturbances. Glycolic acid, formate and formaldehyde are other metabolites of glycine and these too can cause visual disturbances. The signs of glycine toxicity are nausea, vomiting, slow respiration, seizures, spells of apnoea and cyanosis, hypotension, oliguria, anuria and then death. When arginine, another nonessential amino acid is added to the glycine infusion, the toxic effect of glycine on the heart is blunted. The mechanism by which arginine protects the heart is unknown. The normal value of serum glycine in man is 13-17 mg/l. Glycine toxicity is very uncommon in TURP patients probably because most of the absorbed glycine is retained in the periprostatic and retroperitoneal spaces, where it has no systemic effect. 5. Ammonia Toxicity Ammonia is a major by-product of glycine metabolism." High ammonia concentration suppresses norepinephrine and dopamine release in the brain. This causes the encephalopathy of TURP syndrome. Fortunately ammonia toxicity is rare in man. Characteristically the toxicity occurs within one hour after surgey. The patient develops nausea and vomiting and then lapses into coma. Blood ammonia rises above 500 micromols/1 (normal value is 11-35 micromols/1). Hyperammonemia lasts for over ten hours postoperatively, probably because glycine continues to be absorbed from the periprostatic space. It is not clear why hyperammonemia does not develop in all TURP patients. Hyperammonemia implies that the body cannot fully metabolize glycine through the glycine cleavage system, citric acid cycle and conversion to glycolic acid and glyoxylic acid. Another possible explanation is arginine deficiency. Ammonia is normally converted to urea in the liver via the ornithine cycle. Arginine is one of the intermediary products necessary for this cycle. When a patient has arginine deficiency, ornithine cycle is not fuelled and thus ammonia accumulates. 6. Hypovolemia, Hypotension The classical hemodynamic signs of the TURP syndrome, when glycine is used as irrigating fluid, consist of a transient arterial hypertension, that may be absent if the bleeding is profuse, followed by more prolonged hypotension. , Release of prostatic tissue substances and endotoxins into the circulation and associated metabolic acidosis might contribute to this hypotension. ,, Blood loss during TURP leads to hypovolemia, causing significant loss in oxygen carrying capacity leading to myocardial ischemia and infarction. Blood loss correlates with the size of prostatic gland resected, duration of surgery and skill of the surgeon. The average blood loss during TURP is 10 m1/gram of prostate resected. 7. Visual Disturbances One of the most alarming complications of TURP syndrome is transient blindness, foggy vision and seeing halos around objects. ,,The pupils may be dilated and unresponsive. The optic disc appears normal. The symptom can coexist with other features of TURP syndrome or can be an isolated symptom. The vision returns to normal in 8-48 hours after surgery. TURP blindness is caused by retinal dysfunction probably due to glycine toxicity. Hence perception of light and blink reflexes are preserved and pupillary responses to light and accommodation are lost in TURP blindness, unlike in blindness due to cerebral cortical dysfunction. 8. Perforations Perforation of urinary bladder can occur during TURP due to surgical instrumentation, in difficult resections, overdistension of bladder and rarely explosion inside the bladder. Instrumental perforation of the prostatic capsule has been estimated to occur in 1% of patients undergoing TURP., An early sign of perforation, which often goes unnoticed, is a decreased return of irrigating fluid from the bladder. Abdominal pain, distension, nausea and distress follow. Bradycardia and arterial hypotension are profound. There is also a high risk of failure to diurese spontaneously. In intraperitoneal perforation, symptoms develop faster. Referred shoulder pain due to irritation of diaphragm and hiccoughs are characteristic symptoms. , Pallor, diaphoresis, abdominal rigidity, nausea, vomiting and hypotension can occur. In extraperitoneal perforation, reflex movements of lower limbs may occur. Explosions inside the bladder are fortunately rare. Cauterisation of prostatic tissue is believed to liberate flammable gases. Normally not enough oxygen will be available inside the bladder to permit an explosion. But when air enters with the irrigant, explosions can occur. 9. Coagulopathies Disseminated Intravascular Coagulation (DIC) or consumption coagulopathy can occur due to release of prostatic particles rich in tissue thromboplastins into the circulation causing secondary fibrinolysis. Dilutional thrombocytopenia can aggravate the situation. DIC can be detected in the blood by a decrease in platelet count, high levels of fibrin degradation products (FDP, >150 mg/dl) and low plasma fibrinogen levels (400 mg/dl). 10. Bacteremia, Septicemia and Toxemia About 30% of all TURP patients have infected urine preoperatively. When prostatic venous sinuses are opened preoperatively and high pressure irrigation is used, bacteria enter the circulation. In about 6% of patients, the bacteremia is complicated by septicemia. Absorption of bacterial endotoxins and toxic byproducts of tissue coagulation may lead to a toxic state in some patients postoperatively. Severe chills, fever, capillary dilatation and hypotension can occur temporarily in these patients. 11. Hypothermia Hypothermia is a frequent observation in patients undergoing TURP. A drop in the body temperature alters the hemodynamic situation, results in shivering and markedly increases oxygen consumption. Bladder irrigation is an important source of heat loss and the use of irrigating fluids at room temperature results in a decrease in body temperature of 1-2deg C. This is aggravated by the cold atmospheric temperature of operation theatre. Elderly patients are particularly susceptible to hypothermia because of possible autonomic dysfunction. The associated vasoconstriction and acidosis can adversely affect the heart and can contribute to CNS manifestations. Shivering can also enhance bleeding from the resection site. Prophylaxis Against TURP Syndrome Identification of early symptoms of TURP syndrome and prevention is essential to retard the onset of severe and fatal manifestations in patients undergoing endoscopic surgeries. Pre-existing hyponatremia should be identified and corrected, especially in patients on diuretics and low salt diet. Prophylactic antibiotics may have a role in the prevention of bacteremia and septicemia. Central Venous Pressure (CVP) monitoring or pulmonary artery catheterisation is necessary in patients with cardiac illness. The ideal height of irrigating fluid is 60 cm. The duration of TURP should be restricted to 1 hour , and in cases requiring more duration of resection, staged TURP should be performed. Prostatic capsule should be preserved as far as possible and distension of bladder avoided. Continuous flow methods have been claimed to decrease fluid absorption, whereas some authors have found no such reduction. Serum sodium should be estimated every 30 minutes and necessary corrections should be made. The fluid therapy should be restricted to maintain optimum hemodynamics. Prophylactic frusemide should be given to avoid fluid overload. Whenever possible, packed cells should be preferred to whole blood for transfusion to avoid circulatory overload. Increasing the atmospheric temperature of operation theatre, use of warm blankets, mattresses and intravenous fluids and using irrigating fluids prewarmed to 37deg C help to avoid hypothermia. General Anesthesia vs Regional Anesthesia in TURP TURP performed under regional anesthesia without sedation (Awake TURP) is preferable to general anesthesia due to the following reasons: Early manifestations of TURP syndrome are better detected in awake patients. Peripheral vasodilatation helps to minimize circulatory overloading. Provides some degree of postoperative analgesia. Blood loss will be less. However the possible sudden hemodynamic fluctuations of spinal or epidural anesthesia should be taken into consideration before administering regional anesthesia. Treatment The treatment of TURP syndrome involves correction of various pathophysiological mechanisms operating in body homeostasis. ,,,, Ideally the treatment has to be instituted before serious CNS or cardiac complications occur. When TURP syndrome is diagnosed, surgical procedure should be terminated as early as possible. Frusemide should be administered in a dose of 1 mg/kg intravenously. However, the use of frusemide to treat TURP syndrome has been questioned because it increases sodium excretion. Hence 15% mannitol has been suggested as a better choice, due to its action independent of sodium excretion and its tendency to increase extracellular osmolality. Oxygen should be administered by nasal cannula. Pulmonary edema should be managed by tracheal intubation and positive pressure ventilation with 100% oxygen. Arterial blood gases, hemoglobin and serum sodium are to be estimated. Correction of hyponatremia should be done by diuresis and slow administration of 3-5% hypertonic saline at the rate of not more than 0.5 meq/1 per hour or not faster than 100 ml/hr. Approximately 200 ml of hypertonic saline is needed for correction of hyponatremia. Rapid administration of saline leads to pulmonary edema and central pontine myelinolysis. Two-thirds of the hypertonic saline restores serum sodium and osmolality, while one-third redistributes water from cells to the extracellular space, where it becomes available to diuretic treatment with frusemide. Intravenous calcium may be used to treat acute cardiac disturbances during surgery. Seizures should be managed by diazepam/midazolam/barbiturate/dilantin or a muscle relaxant depending on the severity. Significant blood loss should be managed by administering packed red cells. In cases of DIC, fibrinogen 3-4 gms should be given intravenously followed by heparin infusion 2000 units bolus (and then 500 units per hour). Fresh Frozen Plasma (FFP) and platelets may also be used depending on the coagulation profile. Surgical drainage of retroperitoneal fluid in cases of perforation can reduce the morbidity and mortality significantly.
Hypokalemia
Hyponatremia
Hyperkalemia
Hypernatremia