Anesthesia and analgesia
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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.
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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)
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Anesthesia and analgesia · Jan 1993
Comparative StudyElectrocardiographic changes during cesarean section: a cause for concern?
A Holter monitor was used to record ST segment changes during cesarean section in 170 consecutive healthy parturients starting 2 h before and ending 3 h after surgery. Lumbar epidural anesthesia (LEA, n = 120) or subarachnoid anesthesia (SA, n = 50) was used. Transthoracic 2-D echocardiograms were obtained in 30 patients from the LEA group. ⋯ The operative events, alone or in combination, including hypertension, tachycardia, hypotension, bradycardia, air embolism (precordial Doppler) were neither specific nor sensitive as predictors of ST segment change (stepwise logistic regression). Tachycardia was associated with ST segment changes in 10% of time epochs (5 min) (P = 0.05, x2 analysis). Thus, ST segment changes during cesarean section are not caused by myocardial ischemia and are not of any clinical consequence.
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Anesthesia and analgesia · Jan 1993
Median nerve blockade during diagnostic intravenous regional anesthesia as measured by somatosensory evoked potentials.
Intravenous regional anesthesia (IVRA) may be used as a diagnostic method in patients suffering from chronic pain in the forearm or hand to differentiate the origin of pain within the anesthetic area from that above. For this purpose it needs to be proven that all nerve fibers are blocked and that conduction blockade induced by IVRA takes place within the nerve trunks. Therefore the transmission of impulses in a nerve trunk to the central nervous system has been studied. ⋯ The changes in latency and amplitude of SSEPs from the scalp as well as SNAPs and SSEPs from the neck were similar. Because SSEPs, SNAPs, and the pain sensation following median nerve stimulation disappeared during IVRA, it may be concluded that the thick and thin myelinated nerve fibers of the median nerve have been blocked. For diagnostic use, IVRA is superior to peripheral nerve blockade, which has been shown previously to not abolish SSEPs.