Spinal anesthesia using a 1:1 mixture of bupivacaine and tetracaine for peripheral vascular surgery

Study Objective: To present our preliminary experience using three doses of an equimilligram mixture of 1% tetracaine and 0.75% bupivacaine in 8.25% dextrose for spinal anesthesia in patients undergoing peripheral vascular surgery. Setting: Operating and recovery rooms at a university medical center. Patients: 60 patients who received femoral popliteal or femoral distal bypass with spinal anesthesia. Interventions: All patients had intravenous cannulae inserted and received lactated Ringer's solution. There were no bolus infusions of fluid preanesthesia. Fluid administration occurred at a rate of 8 to 15 ml/kg/hr, with additional fluid and inotropic drugs administered to treat hypotension. Oxygen (O 2) was delivered by nasal cannula, and peripheral O 2 saturation was monitored. Blood pressure (BP) was monitored every 1 to 5 minutes using an automatic BP device, and ECG was displayed continually. Measurements and Main Results: Initially, 8 patients received a dose of 15 mg of each drug combined with 0.2 mg of epinephrine injected in a 20-degree head-up tilt. Because the duration of anesthesia was prolonged, subsequent patients received 12 mg of each drug mixed with 0.2 mg of epinephrine for cases in which an extended duration was predicted and 10 mg of each drug plus epinephrine for proximal first-time bypasses. With mixtures of 15 mg, 12 mg, and 10 mg of each drug plus epinephrine, a mean duration of approximately 300 minutes of surgically acceptable anesthesia was obtained. As the dose was decreased, the SD increased. There was a 0% failure rate for the spinal anesthetics at doses of 15 mg and 12 mg of each drug and a 19.5% failure rate at a dose of 10 mg of each drug. In each case, the rapid onset of a sensory blockade regressed in a standard and predictable fashion. The decline in BP and the use of inotropic and vasoconstrictive drugs were comparable to those in previously published reports of spinal anesthetics using single drug techniques with smaller doses. In none of the patients were there any untoward cerebrovascular or neurologic events, nor were there any clinically evident episodes of coronary insufficiency. Conclusion: Spinal anesthesia using bupivacaine and tetracaine mixed in a single-injection technique can last 5 hours at the T 12 level without added untoward effects when compared with lower-dose spinal anesthetics.