Anesthesia and analgesia
-
Anesthesia and analgesia · Jan 1993
Comparative StudySupramaximal second gas effect: more rapid rise of alveolar halothane concentration during ipsilateral lung N2O administration compared to bilateral administration.
To elucidate the mechanism of the second gas effect, we enhanced halothane uptake by a method other than by increasing the inspiratory concentration of N2O. We determined the effect of N2O elimination via the right lung, which is not receiving N2O (halothane and oxygen), on the halothane uptake in the left lung with N2O added to an inspiratory gas mixture during a differential ventilation using a double-lumen tube. Under the setting, some N2O which was absorbed in the left lung, and eventually eliminated via the right lung, decreased end-tidal (ET) N2O and thereby increased the inspired to end-tidal gradient for N2O in the left lung which was receiving N2O. ⋯ On-line gas measurement was performed using Raman spectrometers. The second gas effect was observed between the control groups. N2O was detected in the exhaled gas from the right lung after 3 min of inhalation into the left lung.(ABSTRACT TRUNCATED AT 250 WORDS)
-
Anesthesia and analgesia · Jan 1993
Comparative StudyOn the mechanisms of potentiation of local anesthetics by bicarbonate buffer: drug structure-activity studies on isolated peripheral nerve.
Impulse inhibition by local anesthetics (LAs) is potentiated by extracellular solutions containing HCO3-. CO2 (BC), relative to the inhibition in BC-free solutions at the same pH. We studied the mechanistic basis of this potentiation by assaying compound action potential amplitudes in desheathed frog sciatic nerves with the sucrose-gap method. ⋯ However, slight differences in the molecular structure of 3 degrees-amine LAs with similar pKa values resulted in significantly different potentiations (e.g., procaine, PF = 3.9; 2-chloroprocaine, PF = 8.7), suggesting that the HCO3- or CO2 molecules interact specifically with the LA molecule or with LA binding sites in the nerve membrane. Spectrophotometric measurements of the free [Ca2+] in Ringer's showed it to be similar (+/- 0.03 mM) for both buffers, obviating changes in extracellular Ca2+ as a mechanism of BC potentiation. The resting potential of the nerve was slightly more negative (approximately -4 mV) in BC-R, so membrane depolarization cannot explain the potentiation.(ABSTRACT TRUNCATED AT 400 WORDS)
-
Anesthesia and analgesia · Jan 1993
Randomized Controlled Trial Comparative Study Clinical TrialPostoperative voiding interval and duration of analgesia following peripheral or caudal nerve blocks in children.
We studied the time to postoperative micturition and the duration of analgesia in 82 children aged 6 mo to 10 yr undergoing herniorrhaphy or orchiopexy under general anesthesia with N2O and halothane. All received D5 lactate Ringer's solution equivalent to 6 h maintenance intraoperatively, and oral fluids postoperatively ad libitum. At the end of surgery, patients were randomly assigned to receive one of three regional anesthetic injections using 0.25% bupivacaine: caudal, 0.75 mL/kg (group I); caudal with 1:200,000 epinephrine, 0.75 mL/kg (group II); or ilioinguinaliliohypogastric nerve block with epinephrine through the wound by the surgeon (group III). ⋯ Seven patients who took more than 8 h to void required no intervention. There was no difference in the numbers without pain for > or = 4 h (74%, 64%, and 69% of groups I, II, and III), or those requiring analgesics by 24 h (66% overall). The time to postoperative voiding in children is variable and not prolonged by caudal analgesia; caudal bupivacaine with or without epinephrine and ilioinguinaliliohypogastric nerve block are equally effective for postoperative analgesia.
-
Anesthesia and analgesia · Jan 1993
Randomized Controlled Trial Clinical TrialIntravenous isoproterenol as a marker for epidural test-dosing in children.
The purpose of this study was to determine if isoproterenol would be an effective marker of intravascular injection in anesthetized children. Forty-four ASA 1 children, aged 2 mo to 10 yr, were randomly assigned to two groups. Children in group 1 (n = 21) received 0.05 microgram/kg isoproterenol, and children in group 2 (n = 23) received 0.075 microgram/kg isoproterenol. ⋯ Isoproterenol, 0.075 microgram/kg, is more sensitive but still is an imperfect marker of an intravascular injection. It produces a heart rate increase in 96% of children anesthetized with halothane and nitrous oxide in 50% oxygen. The application of isoproterenol as an epidural test dose appears promising, but cannot be recommended until its full reliability and neurotoxicity are evaluated.
-
Anesthesia and analgesia · Jan 1993
Comparative StudyRecovery from pancuronium and vecuronium administered simultaneously in the isolated forearm and the effect on recovery following administration after cross-over of drugs.
If recovery of neuromuscular block in the isolated arm is determined by biophase binding, then a significant amount of drug will still be present in the biophase at 50% recovery of twitch response. To test this hypothesis we administered pancuronium at 50% recovery from vecuronium block and vecuronium at 50% recovery from pancuronium block in the isolated forearms of volunteers. ⋯ Prior administration of vecuronium significantly shortened the recovery from subsequent pancuronium when administered at 50% recovery, but not 100% recovery, and pancuronium significantly increased the recovery rate of vecuronium when given at 50% recovery but not 100% recovery. These findings support the concept of biophase binding of nondepolarizing neuromuscular blocking drugs.