Anesthesia and analgesia
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To investigate how epidural anesthesia changes intrathoracic gas volume, high epidural anesthesia was administered to five pentobarbital-anesthetized dogs lying supine, and the total intrathoracic volume at end-expiration was measured with a high-speed three-dimensional x-ray scanner. The amount of gas in the lungs at end-expiration [the functional residual capacity (FRC)] was measured with a nitrogen washout technique, and the intrathoracic tissue volume, including the intrathoracic blood volume, was calculated as the difference between intrathoracic volume at end-expiration and FRC. ⋯ We conclude that increases in FRC caused by epidural anesthesia in anesthetized dogs lying supine may be minimized by a concurrent increase in intrathoracic blood volume. These results suggest that measurements of thoracic gas volume alone may be insufficient to describe chest wall responses to epidural anesthesia.
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Anesthesia and analgesia · Jul 1993
Randomized Controlled Trial Comparative Study Clinical TrialComparison of intrathecal fentanyl infusion with intrathecal morphine infusion or bolus for postoperative pain relief after hip arthroplasty.
The purpose of this study was to compare an intrathecal fentanyl infusion with intrathecal morphine infusion or bolus for postoperative pain relief after hip arthroplasty. Sixty patients scheduled to undergo hip joint replacement were studied. A 28-gauge (n = 12) or a 22-gauge (n = 48) spinal catheter was introduced through the L3-4 interspace, 3-4 cm into the subarachnoid space. ⋯ In Group I, supplementary intramuscular (IM) opioid was required more often (46 doses) than in Group II (18 doses) in 24 h (P < 0.01). The number of patients given IM administered opioid was larger in Group I (18 patients) than in Group II (8 patients) (P < 0.01). The IM opioid was requested sooner in Group I (18 patients, mean 480 min) after the intrathecal injection than in Group III (13 patients, mean 786 min) (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
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Anesthesia and analgesia · Jul 1993
Randomized Controlled Trial Clinical TrialNerve stimulator polarity and brachial plexus block.
To determine whether needle polarity significantly affects nerve stimulation during peripheral nerve block, we performed a randomized double-blinded study of 10 patients undergoing axillary block for upper extremity surgery. Using an insulated needle, we determined the minimum current necessary to elicit muscle contraction with positive and negative needle polarity at two needle placements: (A) where stimulation was first observed and (B) where stimulation was maximal. At Position A, stimulation required significantly more current when the needle was positive (2.32 +/- 0.45 mA, mean +/- SEM) than when it was negative (1.05 +/- 0.23 mA, P < 0.001). ⋯ The mean ratio of positive to negative threshold stimulation current at Position B (3.11 +/- 0.20) was significantly greater than that at Position A (2.37 +/- 0.19, P < 0.05). Our results emphasize the importance of attaching the negative terminal of the nerve stimulator to the stimulating electrode. Use of the positive terminal could lead to abandoning a block if stimulation were not obtained at a low enough current; alternatively, motor contraction might not be observed before neural contact or vascular puncture.