Anesthesia and analgesia
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Anesthesia and analgesia · Feb 1991
Randomized Controlled Trial Clinical TrialCerebral blood flow decreases with time whereas cerebral oxygen consumption remains stable during hypothermic cardiopulmonary bypass in humans.
Recent investigations demonstrate that cerebral blood flow (CBF) progressively declines during hypothermic, nonpulsatile cardiopulmonary bypass (CPB). If CBF declines because of brain cooling, the cerebral metabolic rate for oxygen (CMRO2) should decline in parallel with the reduction in CBF. Therefore we studied the response of CBF, the cerebral arteriovenous oxygen content difference (A-VDcereO2) and CMRO2 as a function of the duration of CPB in humans. ⋯ Patients were randomly assigned to management within either a lower (32-48 mm Hg) or higher (50-71 mm Hg) range of PaCO2 uncorrected for temperature. Each patient underwent two randomly ordered sets of measurements, one at a lower PaCO2 and the other at a higher PaCO2 within the respective ranges. Cerebrovascular responsiveness to changes in PaCO2 was calculated as specific reactivity (SR), the change in CBF divided by the change in PaCO2, expressed in mL.100 g-1.min-1.mm Hg-1.(ABSTRACT TRUNCATED AT 250 WORDS)
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Anesthesia and analgesia · Feb 1991
Comparative StudySaline-filled cuffs help prevent laser-induced polyvinylchloride endotracheal tube fires.
To determine whether the filling of tracheal tube cuffs with saline would decrease their combustibility during laser surgery, 20 polyvinylchloride tracheal tubes were studied. The cuffed end of each tracheal tube was inserted into the neck of an empty flask, and the tube and flask were flushed with oxygen for 5 min before cuff inflation. Ten tracheal tubes had their cuffs inflated with air, and 10 were inflated with saline. ⋯ The time to deflation of the saline-filled cuff (104.6 +/- 67.5 s) was, however, significantly longer than that of the air-filled cuff (2.59 +/- 1.97 s). When the tracheal tube cuffs were exposed to 40-W laser radiation, the cuff and adjacent tube shaft ignited in all cases when the cuffs were inflated with air, but only in one of five cases when the cuffs were filled with saline (P less than 0.05). The filling of tracheal tube cuffs with saline provides simple, moderately effective partial protection of the cuff of endotracheal tubes during CO2 laser airway surgery.
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Anesthesia and analgesia · Feb 1991
Pharmacokinetics and pharmacodynamics of doxacurium in normal patients and in those with hepatic or renal failure.
We determined the pharmacokinetics and duration of action of a bolus dose of doxacurium (15 micrograms/kg) in 27 patients anesthetized with isoflurane and nitrous oxide. Nine patients had normal renal and liver functions and were undergoing a variety of surgical procedures, nine were undergoing cadaveric kidney transplantation because of end-stage renal disease, and nine were undergoing cadaveric liver transplantation because of end-stage hepatocellular disease. Plasma concentrations of doxacurium were measured for 6 h after administration using a sensitive and specific capillary gas chromatographic assay. ⋯ The degree of neuromuscular blockade after doxacurium administration was described as the percent of control of the first train-of-four response. The pharmacokinetic variables were (normal vs hepatic failure vs renal failure, respectively): volume of distribution at steady state (220 +/- 110 vs 290 +/- 60 vs 270 +/- 130 mL/kg [mean +/- SD]), plasma clearance (2.7 +/- 1.6 vs 2.3 +/- 0.4 vs 1.2 +/- 0.7 mL.kg-1.min-1), mean residence time (95.2 +/- 57 vs 129.4 +/- 30 vs 270 +/- 210 min), and elimination half-life (99 +/- 54 vs 115 +/- 31 vs 221 +/- 156 min). Plasma clearance and mean residence time differed significantly between patients with renal failure and control patients.(ABSTRACT TRUNCATED AT 250 WORDS)
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Anesthesia and analgesia · Feb 1991
Myocardial and systemic hemodynamics during isovolemic hemodilution alone and combined with nitroprusside-induced controlled hypotension.
Myocardial and systemic effects of isovolemic hemodilution alone and combined with controlled hypotension induced with sodium nitroprusside (SNP) were studied in halothane-anesthetized, open-chest dogs. Regional blood flow was measured with radioactive microspheres and used to compute regional oxygen (O2) supply. Values for regional blood flow in myocardium were used to compute myocardial O2 (MVO2) and lactate uptake (MVLAC) using the Fick equation. ⋯ In conclusion, although myocardial O2 supply versus demand balance was well maintained during SNP-induced hypotension under hemodiluted conditions, diminished coronary vasodilator reserve suggests increased vulnerability to ischemia if stresses of augmented cardiac work demand or impaired arterial oxygenation were superimposed. The decrease in O2 supply in the kidney during combined hemodilution and SNP-induced hypotension also warrants concern. These latter findings suggest the need for extensive clinical monitoring when SNP is used for controlled hypotension under hemodiluted conditions.