Anesthesiology
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Randomized Controlled Trial Clinical Trial
Lidocaine and bupivacaine mixtures for epidural blockade.
In a prospective double-blind clinical study, single-dose lumbar epidural blockade was instituted in 60 healthy patients undergoing lower abdominal surgery. Patients were randomly assigned to one of five groups. Each group received treatment with a different local anesthetic solution containing 1:200,000 epinephrine. ⋯ Using skin temperature as a criterion of sympathetic blockade, all three mixtures demonstrated a duration of action intermediate between the two single drugs, lidocaine (124 +/- 13 min) and bupivacaine (286 +/- 32 min). Onset of complete motor blockade was fastest and the degree of motor blockade was most profound with the mixture containing equal proportions of lidocaine and bupivacaine. Pharmacokinetics of individual drugs were unaltered in any of the mixtures.
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To determine the effects of tidal volume (VT) and positive end-expiratory pressure (PEEP) on pulmonary oxygen exchange during endobronchial (one-lung) anesthesia, the authors studied the effects of VT at 8 and 16 per cent total lung capacity (TLC), at zero end-expiratory pressure (ZEEP), and at 10 cmH2O PEEP in 16 patients in the lateral position. Anesthesia was maintained with halothane and oxygen. During two-lung ventilation (FIO2 0.99), mean PaO2 and physiologic shunt (Qs/Qt) were 421 +/- 12 mmHg and 0.22 +/- 0.02, respectively. ⋯ At both levels of VT, PEEP reduced mean Qt by approximatley 10 per cent (P less than 0.01) and increased compliance (P less than 0.01). However, PEEP did not significantly affect mean Qs/Qt or mean arterial or pulmonary arterial pressures at either level of VT. There was considerable variation in PaO2 and Qs/Qt among patients.