Anesthesia and analgesia
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Anesthesia and analgesia · Sep 1989
Myocardial and cerebral drug concentrations and the mechanisms of death after fatal intravenous doses of lidocaine, bupivacaine, and ropivacaine in the sheep.
This paper reports the cardiovascular effects of intentionally toxic intravenous doses of lidocaine, bupivacaine, and ropivacaine and the mechanisms of death. Fatal doses of lidocaine, bupivacaine, and ropivacaine were established in sheep treated with successive daily dose increments of each drug. The mean fatal dose of lidocaine (+/- SD) was 1450 +/- 191 mg (30.8 +/- 5.8 mg/kg), that of bupivacaine was 156 +/- 31 mg (3.7 +/- 1.1 mg/kg), and that of ropivacaine was 325 +/- 108 mg (7.3 +/- 1.0 mg/kg); thus the ratio of fatal doses was approximately 9:1:2. ⋯ Three out of five animals given ropivacaine died in a manner resembling the fatal effects of lidocaine-treated animals, but unlike the lidocaine-treated animals, in all three sheep there were also periods of ventricular arrhythmias. The remaining two ropivacaine-treated sheep died as a result of the sudden onset of ventricular tachycardia/fibrillation. The mean percentages of the fatal dose found in the myocardium was 2.8 +/- 0.7 for lidocaine-treated animals, 3.3 +/- 0.9 for bupivacaine-treated animals, and 2.2 +/- 1.4 for ropivacaine-treated animals; the corresponding percentages in whole brain were, respectively, 0.71 +/- 0.01, 0.71 +/- 0.21, and 0.89 +/- 0.27.
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Anesthesia and analgesia · Sep 1989
Hemodynamic and central nervous system effects of intravenous bolus doses of lidocaine, bupivacaine, and ropivacaine in sheep.
Lidocaine hydrochloride (HCl) (80-320 mg), bupivacaine HCl (20-80 mg), and ropivacaine HCl (30-120 mg) were administered as intravenous bolus doses to conscious sheep (n = 18; average body weight 45 kg) that had previously placed intravascular cannulae for hemodynamic monitoring and for obtaining blood samples. The mean convulsive doses and arterial blood concentrations were approximately 110 mg and 40 mg/L, respectively, for lidocaine HCl, 45 mg and 14 mg/L for bupivacaine HCl, and 60 mg and 20 mg/L for ropivacaine HCl. ⋯ Ventricular fibrillation caused death in two sheep after bupivacaine (80 mg) and in two sheep after ropivacaine (90 and 120 mg) administration. With sublethal doses, the hemodynamic responses to these agents were qualitatively and quantitatively similar when compared with their local anesthetic potencies.
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Anesthesia and analgesia · Sep 1989
Randomized Controlled Trial Clinical TrialA cost/benefit analysis of randomized invasive monitoring for patients undergoing cardiac surgery.
The aim of this study was to determine the effect of choice of invasive monitoring on cost, morbidity, and mortality in cardiac surgery. Two hundred and twenty-six adults undergoing elective cardiac surgery were initially assigned at random to receive either a central venous pressure monitoring catheter (group I), a conventional pulmonary artery (PA) catheter (group II), or a mixed venous oxygen saturation (SvO2) measuring PA catheter (group III). If the attending anesthesiologist believed that the patient initially randomized to group I should have a PA catheter, that patient was then reassigned to receive either a conventional PA catheter (group IV) or SvO2 measuring PA catheter (group V). ⋯ Further, mean monitoring and laboratory costs in Group II were statistically significantly (P less than 0.05) less than those in Group III ($1128 +/- 759). Patients in group IV incurred mean total costs of $986 +/- 578, while those in group V had mean total costs of $1126 +/- 382 (NS). There were no significant differences between any of the groups with respect to length of stay in the intensive care unit, morbidity, or mortality.(ABSTRACT TRUNCATED AT 250 WORDS)
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Anesthesia and analgesia · Sep 1989
Randomized Controlled Trial Comparative Study Clinical TrialEffects of thoracic epidural anesthesia on systemic hemodynamic function and systemic oxygen supply-demand relationship.
The effects of thoracic epidural anesthesia (TEA) on total body oxygen supply-demand ratio are complex due to potential influences on both O2 delivery (QO2) and consumption (VO2). One hundred and five patients undergoing abdominal aortic surgery were randomly assigned to one of three groups to compare the cardiovascular and metabolic responses associated with (1) thoracic epidural anesthesia plus light general anesthesia (group TEA); (2) general anesthesia with halothane (group H); and (3) neuroleptanalgesia (group NLA). Values of cardiac index (CI) and QO2 were less intraoperatively in the TEA group than in the H or NLA groups, while VO2 values were similar. ⋯ Heart rate was slowest intraoperatively during TEA, and stroke work was less with TEA than with NLA. As cardiac filling pressure and systemic vascular resistance did not differ among the three groups, reduced adaptation of CI to tissue O2 needs during TEA was attributed to negative inotropic and chronotropic effects of the sympathetic blockade. We conclude that in patients undergoing abdominal aortic surgery, TEA has no apparent advantage over general anesthesia.
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Anesthesia and analgesia · Sep 1989
The effects of airway impedance on work of breathing during halothane anesthesia.
Humidifiers and small diameter endotracheal tubes placed in the airway circuit increase the impedance to breathing. The effect of such impedances on the work of breathing and respiratory patterns was studied in eight healthy adult patients (60-80 kg) anesthetized with 1 and 2 MAC halothane in oxygen. A Cascade Humidifier and Portex Humid-Vent (dry and water saturated) were evaluated while patients breathed through an 8.0-mm endotracheal tube. ⋯ At 1 MAC the Cascade Humidifier and the wet Humid-Vent when used with the 8.0-mm tube increased the work of breathing to 86.8 ml and 76.8 ml, 77% and 70% above baseline levels of 48.1 ml, whereas the 6.0-mm tube without the humidifiers increased work 89% to 78.9 ml. Tidal volume and respiratory frequency were unchanged throughout the study, although inspiratory time was prolonged. Lightly to moderately anesthetized healthy adult patients are able to maintain minute ventilation despite the impedance associated with commonly used humidifiers by significantly increasing work of breathing.