Hemodynamic effects of peripheral nerve blocks for amputations of the lower extremity

Objectives ; Patients with severe atherosclerosis frequently undergo lower limb amputations. A variety of anesthetic techniques have been used to minimize perioperative complications during these procedures including general anesthesia, neuroaxial anesthesia, and peripheral nerve blocks. The aim of our study was to evaluate if during lower extremity amputations, any differences could be detected between traditional anesthetic techniques (general, spinal or epidural anesthesia) and peripheral nerve blocks. We studied intraoperative blood pressure lability, intravenous fluid requirements and the need for vasoactive medications. Methods: An automated anesthesia information system (System 5, Archive Information Systems, Inc.) has collected data from over 120,000 anesthetics at Duke University Medical Center. The database was queried to identify all patients who had undergone lower extremity amputations or amputation stump revisions between January, 1995 and December, 1997. Data collected included patient demographic data, anesthetic technique, initial and lowest intraoperative mean arterial blood pressures (MAP), amount of intravenous fluid, amount and type of vasopressors used. Anesthetic techniques were divided into 1.General and central neuroaxial 2.Peripheral Nerve Blocks. Peripheral nerve blocks included a combination of Lumbar Plexus and Sciatic nerve blockade for surgery above the knee and Femoral and Sciatic nerve blockade for surgery below the knee. Patients undergoing procedures under local anesthesia, MAC or amputations limited to the foot were excluded from analysis. Chi square analysis was used to determine differences between groups. Results ; 374 patients were identified who underwent 428 procedures. There were 66 AKA's, and 15 AKA revisions, 224 BKA's and 118 BKA revisions. Peripheral nerve blocks were used as the primary anesthetic for 82 procedures, 211 procedures were performed with the use of central neuroaxial blockade (200 SAB, 11 epidural), and 135 patients received general anesthesia. Patients who received peripheral nerve blocks had smaller decreases in MAP (34 mmHg vs. 29 mmHg, p<0.05), required less intravenous fluids (750cc vs. 1087 cc, p=0.001), less phenylephrine (21\iq vs. 175fig, p=0.001) and less ephedrine (0.7mg vs. 3.4 mg, p=0.002) when compared with neuroaxial and general anesthesia. Patient demographics were the same in both groups and regression analysis confirmed that anesthetic technique was the only variable predictive of intraoperative hemodynamic changes (p<0.05). Discussion; Peripheral nerve blocks are an effective primary anesthetic technique for lower extremity amputations and are associated with smaller decreases in intraoperative blood pressure, volume of intravenous fluid, and amount of vasopressors needed, than either general anesthesia or neuroaxial blockade. These results suggest that in patients where tight control of intraoperative hemodynamics and fluid management is critical, peripheral nerve blocks may offer significant advantages.

Duke Scholars

Author Stephen Matthew Klein Anesthesiology, Ambulatory