Dehydration: cause of acute renal failure.

TO THE EDITOR: I read with interest, the case report describing acute renal failure during spinal cord stimulation trial (1). The authors attributed the episode of acute renal failure to spinal cord stimulation. They speculated that decreased renal blood flow and peripheral vasodilation from sympathetic blockade by spinal cord stimulation contributed to acute renal failure. The effects of spinal cord stimulation on renal blood flow have not been studied. Epidural anesthesia can produce sympathetic nerve system blockade. However, high epidural anesthesia (T6) does not result in a significant change in renal blood flow (2). The degree of sympathetic blockade by epidural anesthesia is higher than by spinal cord stimulation. Sympathetic blockade can cause peripheral vasodilation, which may contribute to hypotension. However, one study showed that spinal cord stimulation did not result in significant changes in mean arterial pressure (3). These studies did not support the theory advanced by Larkin, Dragovich, and Cohen. I believe that the cause of acute renal failure in the Larkin et al case report was hypovolemia. This patient in their study demonstrated signs and symptoms of hypovolemia. He had postural dizziness, hypotension, increased heart beat, and tachypnea. The patient did not urinate for 2 days. After 3 liters of ringer’s lactate, he had normal blood pressure and heart rate. He began to produce urine. His lab result returned to normal. The most common cause of hypovolemia is dehydration. Preoperative dehydration is common in surgical patients due to preoperative fasting. The symptoms of dehydration may be most evident in minor surgical procedures, where intraoperative fluid requirements are low (4). Poor fluid intake postoperatively further intensified dehydration, and resulted in acute renal failure. Therefore, it is important to emphasize how to prevent perioperative dehydration after minor surgery.