Anesthesiology
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Recent evidence suggests that edrophonium is not the agent of choice to reverse profound neuromuscular blockade but remains an efficacious drug when the level of neuromuscular blockade to be antagonized is modest. We studied 90 healthy adults in an attempt to address the questions: 1) How much variability in such neuromuscular parameters as single twitch height and the train-of-four (TOF) fade ratio (T4/T1) exist when the TOF count first returns to four palpable responses? 2) Is edrophonium a reliable antagonist at this measured point of recovery? 3) What is the optimal dose of edrophonium needed to produce prompt (less than 10 min) and satisfactory (T4/T1 greater than 0.7) reversal when the fourth response of the thumb to indirect TOF stimulation just becomes palpable? Patients were given a bolus atracurium or vecuronium (n = 45 in each group) followed by an iv infusion sufficient to maintain single twitch as measured by electromyography at 10-15% of control values. At the end of surgery, the infusion was terminated and spontaneous recovery was allowed to begin. ⋯ After atracurium neuromuscular blockade, edrophonium 0.3 mg/kg produced adequate antagonism in 10 min. At this time the mean T4/T1 ratio was 0.79 +/- 0.07 and the lowest observed value was 0.67. Increasing the edrophonium dose to 0.75 mg/kg accelerated recovery by 4-5 min.(ABSTRACT TRUNCATED AT 250 WORDS)
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It has been hypothesized recently that succinylcholine-associated increases in intracranial pressure (ICP) are caused by the paraben preservatives contained in multidose vials. We tested that hypothesis in a standard feline model to determine the effects on ICP of equal-volume injections of preservative-free succinylcholine, succinylcholine with preservatives from multi-dose vials that contain both propylparaben and methylparaben, these preservatives alone at five times the dose contained in the succinylcholine, and normal saline. The preservatives alone increased ICP by 0.08 +/- 0.08 mmHg (+/- standard error; not significant). ⋯ Preservative-free succinylcholine and succinylcholine with preservatives increased ICP by 4.2 +/- 0.10 and 3.8 +/- 0.07 mmHg respectively (P less than 0.01 compared to the preservatives alone and normal saline). The 99% upper confidence limit for the increase in ICP induced by the preservatives alone was 0.42 mmHg. This result suggests that parabens do not cause or substantially augment the ICP increase associated with succinylcholine administration.
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To demonstrate that sympathetic responses transmitted by the splanchnic nerve help maintain intravascular stability, 12 mongrel dogs (35-45 kg each), anesthetized with pentobarbital, were given two separate but identical hypotensive stimuli (mean arterial blood pressure of 60 mm Hg for 15 min) by the withdrawal of appropriate amounts of blood. The first stimulus was performed in the absence of drug or surgical manipulation. The second stimulus was performed after animals were subjected to no intervention (n = 4), bilateral splanchnic nerve section (n = 4), or spinal anesthesia (n = 4). ⋯ The volume of blood withdrawn to produce hypotension was similar (approximately 21 ml.kg-1). Bilateral splanchnic nerve section attenuated the adrenal medullary blood flow, arterial epinephrine concentration, and abdominal organ blood flow responses to hypotension by 86, 64, and 66%, respectively (P less than 0.008), and the blood volume withdrawn was reduced by 42% (P less than 0.02). Spinal anesthesia eliminated the adrenal medullary blood flow response to hypotension, attenuated the arterial epinephrine concentration and abdominal organ blood flow responses by 78 and 57%, respectively (P less than 0.01), and decreased the blood volume extracted by 55% (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)