Anesthesia for Noncancer Surgery of the Upper Ureter & Kidney

NONCANCER SURGERY OF THE UPPER URETER & KIDNEY

Laparoscopic urological procedures, including par-tial and total nephrectomy, live donor nephrectomy, nephrolithectomy, and pyeloplasty are increasingly utilized because of advantages that include relatively rapid recovery, shorter hospital stay, and less pain. Both transperitoneal and retroperitoneal approaches have been developed. A hand-assisted technique employs an additional larger incision that allows the surgeon to insert one hand for tactile sensation and facilitation of dissection. Anesthetic management is similar to that for any laparoscopic procedure.

Open procedures for kidney stones in the upper ureter and renal pelvis, and nephrectomies fornonmalignant disease, are often carried out in the “kidney rest position,” more accurately described as the lateral flexed position. With the patient in a full lateral position, the dependent leg is flexed and the other leg is extended. An axillary roll is placed beneath the dependent upper chest to minimize the risk of brachial plexus injury. The operating table is then extended to achieve maximal separa-tion between the iliac crest and the costal margin on the operative side, and the kidney rest (a bar in the groove where the table bends) is elevated to raise the nondependent iliac crest higher and increase surgi-cal exposure.

The lateral flexed position is associated with adverse respiratory and circulatory effects. Functional residual capacity is reduced in the dependent lung but may increase in the nondependent lung. In the anesthetized patient receiving controlled ventilation, ventilation/perfusion mismatching occurs because the dependent lung receives greater blood flow than the nondependent lung, whereas the nondependent lung receives greater ventilation, predisposing the patient to atelectasis in the dependent lung and to shunt-induced hypoxemia. The arterial to end-tidal gradient for carbon dioxide progressively increases during general anesthesia in this position, indicating that dead space ventilation also increases in the non-dependent lung. Moreover, elevation of the kidney rest can significantly decrease venous return to the heart in some patients by compressing the inferior vena cava. Venous pooling in the legs potentiates anesthesia-induced vasodilation.

Because of the potential for large blood loss and limited access to major vascular structures in the lateral flexed position, initial placement of at least one large-bore intravenous catheter is advis-able. Arterial catheters are often utilized because of the need to closely monitor blood pressure and to frequently withdraw blood for laboratory analy-sis. Endotracheal tube placement may be altered during postinduction positioning of the patient for operation, and thus proper endotracheal tube place-ment must again be verified following final patient positioning prior to skin preparation and surgical draping. Intraoperative pneumothorax may occur as a result of surgical entry into the pleural space. Diagnosis requires a high index of suspicion. The pneumothorax may be subclinical intraoperatively but can be diagnosed postoperatively with a chest radiograph.