Anesthesiology
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Letter Case Reports
Delayed onset of pneumothorax following internal jugular vein cannulation.
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Comparative Study
Pharmacokinetics, pharmacodynamics, and rational opioid selection.
Fentanyl, alfentanil, and sufentanil have important pharmacokinetic and pharmacodynamic differences. Selecting one of these opioid analgesics as an adjunct to general anesthesia requires appreciation of the relationship between the pharmacokinetic and pharmacodynamic characteristics of these drugs and the onset of and recovery from drug effect. Using a pharmacokinetic-pharmacodynamic model, the authors simulated the decrease in plasma fentanyl, alfentanil, and sufentanil concentration after intravenous administration by either bolus injection, brief infusion, or prolonged infusion. ⋯ Alfentanil may also be the most appropriate drug to provide a transient peak effect after a single bolus. Although sufentanil has longer distribution and elimination half-lives than alfentanil, recovery from sufentanil infusions may be more rapid than recovery from alfentanil infusions for operations shorter than 6-8 h. These computer simulations demonstrate that simply comparing pharmacokinetic parameters (e.g., half-lives) of different drugs will not predict the relative rates of decrease in effect site concentrations after either an intravenous bolus or a continuous infusion.
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Comparative Study
Electroencephalographic quantitation of opioid effect: comparative pharmacodynamics of fentanyl and sufentanil.
The authors compared the pharmacodynamics of sufentanil with those of fentanyl using the electroencephalogram (EEG) as a measure of opioid drug effect. Sixteen patients were given a rapid infusion of sufentanil (18.75 micrograms/min) during EEG recording. To quantitate the opioid-induced slowing of the EEG, the authors analyzed its power spectrum and calculated the spectral edge. ⋯ The time from injection to 50% maximal EEG slowing (T50) was calculated for each patient. The values for T50 for the two groups did not differ. The authors conclude that fentanyl and sufentanil have similar pharmacodynamic profiles, the former being 12 times more potent than the latter.
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To determine whether transesophageal echocardiography could be used to estimate intraoperative cardiac output, the authors studied 35 consecutive patients undergoing cardiovascular surgery (coronary artery disease [n = 22], aortic valve disease [n = 5], mitral valve stenosis [n = 5], peripheral vascular disease [n = 3]). Two-dimensional echocardiographic and pulsed-wave Doppler signals of the pulmonary artery and mitral valve flow velocity were obtained simultaneously with thermodilution measurements of cardiac output. ⋯ Although this technique identifies increases in cardiac output greater than 15%, it does not detect decreases as accurately as those detected by thermodilution measurements. At this time, therefore, transesophageal Doppler echocardiography has significant limitations as an off-line monitor of cardiac output.
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This investigation evaluated the hemodynamic effects of orally administered dexmedetomidine in chronically instrumented dogs in the conscious state, during enflurane anesthesia, and after emergence. Four experimental groups (n = 9 each) were completed. In groups 1 and 2, dexmedetomidine (10 or 20 micrograms/kg, respectively) was administered orally, and hemodynamics, arterial blood gas tensions, and plasma norepinephrine concentrations were monitored for 6 h. ⋯ Peak effects occurred within 30 min and lasted approximately 3 h. No reduction in coronary blood flow velocity, decrease in regional contractile function, or respiratory depression was observed. Administration of dexmedetomidine before enflurane anesthesia also was associated with a reduction in heart rate and rate-pressure product, and dexmedetomidine prevented the increase in heart rate (146 +/- 9 vs. 60 +/- 7 beats per min) and arterial pressure (117 +/- 7 vs. 98 +/- 7 mmHg) during emergence from anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)