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 (O2) was delivered by nasal cannula, and peripheral O2 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 T12 level without added untoward effects when compared with lower-dose spinal anesthetics.

Lupus anticoagulant. Implications for obstetric anaesthetists.

Circulating lupus anticoagulant occurs in 5-37% of all patients with systemic lupus erythematosus. Its occurrence is not restricted to collagen vascular disease states. Lupus anticoagulant causes a prolongation of certain laboratory coagulation studies yet it is associated in vivo with a history of systemic intravascular thromboses. Placental vessels are also affected. Less than one in six pregnancies complicated by the presence of this auto-antibody is successful. Treatment of afflicted parturients with anti-platelet therapy has increased perinatal survival rates. Derangements in the coagulation profile and concomitant anti-platelet therapy confound the rational use of regional anaesthesia in the management of labour and delivery in these high-risk pregnancies.

Epidural analgesia in labour and maternal posture.

The effect of maternal position in the period immediately following epidural administration on analgesia and side effects was examined during labour. Patients were randomly allocated to two groups and were either turned from left to right lateral position within 5 minutes of bupivacaine administration (n = 35), or kept in the supine position, modified as appropriate, until pain relief or side effects indicated a change (n = 35). There was no significant difference between the two groups in onset or duration of analgesia, the need for supplements or in absorption of bupivacaine. Circulatory disturbances, all mild and transient, were seen in 14 patients (eight lateral, six supine). There was no significant difference between the two groups either in the frequency of hypotension (four lateral, five supine) or of fetal heart deterioration (four lateral, three supine). However motor block occurred in 15 of the lateral group and five supine (p less than 0.02). Such differences are not thought sufficient to counterbalance the potential circulatory disadvantage of the supine position.