Anesthesia and analgesia
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Anesthesia and analgesia · May 1996
Perioperative distribution of pulmonary vascular resistance in patients undergoing coronary artery surgery.
This study was undertaken to measure distribution of pulmonary vascular resistance (PVR) perioperatively in patients undergoing coronary artery bypass grafting (CABG) and to examine the effects of cardiopulmonary bypass (CPB) on pulmonary capillary pressure (Pc) relative to wedge pressure (Pw). Pulmonary artery catheters were placed before anesthetic induction in 18 patients scheduled for elective CABG and systemic hemodynamic variables were measured. Pulmonary artery pressure was recorded during balloon inflation and stored for off-line determination of Pc. ⋯ Administration of large-dose opioid anesthesia had no significant effect (P > 0.05) on total PVR or on segmental distribution of vascular resistance. At all data points, Pc was significantly larger than Pw (P < 0.05). This study demonstrates that perioperative measurement of Pc is feasible, that during CABG under these conditions, relative contribution of arterial and venous resistances remain relatively unchanged, that Pc is always larger than Pw, and that the administration of large-dose opioid anesthesia has a minimal effect on pulmonary vascular hemodynamics.
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Anesthesia and analgesia · May 1996
Comparative StudyInteraction of heart rate and hypothermia on global myocardial contraction of the isolated rabbit heart.
We studied the effects of mild hypothermia on cardiac contractility in isolated rabbit hearts perfused with Krebs-Henseleit solution according to the technique of Langendorff. Isovolumetric left ventricular pressure (LVP) was measured with a fluid-filled balloon. Hearts were paced after induction of atrioventricular block. ⋯ At pacing rates > or = 90 bpm, lower systolic LVP, higher diastolic LVP, and lower positive and negative LV dP/dt were obtained in hypothermic (93 +/- 12 mm Hg, 55 +/- 18 mm Hg, 584 +/- 137 mm Hg/s, and 323 +/- 57 mm Hg/s at 210 bpm, respectively) compared to normothermic hearts (123 +/- 4 mm Hg, 10 +/- 4 mm Hg, 1705 +/- 145.5 mm Hg/s, and 1155 +/- 78 mm Hg/s at 210 bpm, respectively.) The duration of mechanical diastole was reduced or suppressed in these hearts. Exposure to the beta-adrenoreceptor agonist, isoproterenol, improved this diastolic dysfunction during hypothermia and pacing at high rates, suggesting that the sarcoplasmic reticulum Ca2+ uptake might be involved. Our data are also consistent with an increase in myofilament Ca2+ sensitivity that is opposed by isoproterenol during hypothermia.
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Anesthesia and analgesia · May 1996
Comparative StudyHemodynamic effects of intravenous isoproterenol versus epinephrine in the chronic maternal-fetal sheep preparation.
Isoproterenol 5 micrograms may be an effective marker of accidental intravascular injection in women in labor; however, before isoproterenol can be incorporated in routinely used epidural test doses, the safety and usefulness should be determined in an animal model. This study was designed to examine the hemodynamic effects of isoproterenol in comparison with epinephrine in the pregnant ewe. Five doses of isoproterenol were tested and compared with two doses of epinephrine in a randomized cross-over fashion. ⋯ A significant increase in the cardiac output was seen after isoproterenol. Neither isoproterenol nor epinephrine affected fetal heart rate (FHR), fetal mean arterial pressure (FMAP), amniotic fluid pressure (Amn-pr), blood gases, or acid base status in the mother and the fetus. Provided that neurotoxic effects are absent, isoproterenol might be a better alternative than epinephrine as a test dose for possible intravenous placement of an epidural catheter in pregnant women.
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Anesthesia and analgesia · May 1996
Auto-positive end-expiratory pressure during one-lung ventilation using a double-lumen endobronchial tube.
The present study was undertaken to investigate the possible relationships between the magnitude of autopositive end-expiratory pressure (auto-PEEP) and measured PaO2 during one-lung ventilation (OLV). Forty-one adults received OLV anesthesia using a tidal volume of 8 mL/kg and a respiratory rate of 12 breaths/min. Auto-PEEP was quantified using an end-expiratory port occlusion method. ⋯ Auto-PEEP during OLV correlated inversely with preoperative forced expiratory volume in 1 s/forced vital capacity (y = 12.5 - 0.13x, r = -.05, P < 0.005). During OLV, there was no significant correlation between auto-PEEP and measured PaO2. These findings confirm that many patients do not exhale completely to functional residual capacity during OLV.
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Anesthesia and analgesia · May 1996
The effect of a cyclodextrin vehicle on the cardiovascular profile of propofol in rats.
We studied the aqueous solution of propofol dissolved in hydroxypropyl-beta-cyclodextrin (HP beta CD) 20% to determine whether the cardiovascular profile differed from that measured for propofol prepared in Intralipid 10% (Diprivan). Conscious male rats were given an intravenous bolus of propofol, 5.0 mg/kg, the minimum dose that induces a loss of righting. Immediately severe bradycardia occurred which was the result of a combination of sinus arrest and atrioventricular block; a significant decrease of blood pressure resulted. ⋯ The severe bradycardia produced by propofol in HP beta CD was blocked by both atropine and bilateral cervical vagotomy. Therefore, the effects of propofol in HP beta CD are cholinergic and neurally mediated. These results are consistent with the hypothesis that propofol reduces sympathetic tone prior to reduction in vagal tone, and thereby produces a period of time during which vagal tone is dominant.