Transurethral resection of the prostate (TURP) is commonly performed in males > 60 years of age and utilizes a cystoscope with a wire loop. Continuous irrigation is used to distend the bladder and to remove dissected tissue. Because of the large venous sinuses present in the prostate, irrigation fluid is absorbed into the systemic vasculature, potentially in high volumes. Slightly hypotonic nonelectrolyte solutions are generally used for irrigation and include glycine 1.5% or a mixture of sorbitol 2.7% and mannitol 0.54%. The degree of absorption tends to depend on the duration of the procedure (most last 45-60 min) and the hydrostatic pressure of the irrigation fluid (the height of the irrigating fluid above the patient). On average, 10-30 ml of irrigating fluid are absorbed per minute.
TURP Syndrome can develop during surgery or immediately after. The neurologic symptoms are often related to hypervolemic hyponatremia due to an excess of total body water in the setting of normal body sodium levels and include headache, restlessness, confusion or seizures. Symptoms do not typically develop until the serum Na concentration falls below 120 mEq/L. Treatment usually involves fluid restriction and loop diuretics. If seizures or coma develop, hypertonic saline can also be used along with anticonvulsants (midazolam, diazepam) and endotracheal intubation to prevent aspiration. The following formulas are useful in determining the rate of correction, the first for estimating total body water and the second for estimating the amount of sodium needed to normalize the low serum sodium levels.
- Total body water = weight in kg x 0.6
- Sodium deficit = (140 – observed plasma Na) x total body water
Care should be taken to avoid too rapid a correction of the hyponatremia to avoid central pontine myelinolysis.
Toxicity may also result from solute absorption. In the past, irrigating solutions used to include distilled water, Lactated Ringers and Normal Saline but these are no longer used in current practice. Glycine 1.5% is used because it is less costly, only slightly hypoosmolar and nonelectrolyte. Glycine is an inhibitory neurotransmitter and if large amounts are absorbed the patient can develop central nervous system toxicity, which includes transient blindness and encephalopathy. Ammonia toxicity can also result because ammonia is a byproduct of glycine metabolism. High ammonia levels can also result in encephalopathy. Sorbitol 2.7% and mannitol 0.54% is another solution commonly used and is also nonelectrolyte, iso-osmolar, rapidly cleared from plasma, but is more costly and can result in fluid overload.