ABSTRACT
We investigated the systemic and regional hemodynamic effects of early crystalloid infusion in an experimental model of septic shock induced by intravenous inoculation with live Escherichia coli. Anesthetized dogs received an intravenous infusion of 1.2 x 10(10) cfu/kg live E. coli in 30 min. After 30 min of observation, they were randomized to controls (no fluids; N = 7), or fluid resuscitation with lactated Ringer's solution, 16 ml/kg (N = 7) or 32 ml/kg (N = 7) over 30 min and followed for 120 min. Cardiac index, portal blood flow, mean arterial pressure, systemic and regional oxygen-derived variables, blood lactate, and gastric PCO2 were assessed. Rapid and progressive cardiovascular deterioration with reduction in cardiac output, mean arterial pressure and portal blood flow (about 50, about 25 and about 70 percent, respectively) was induced by the live bacteria challenge. Systemic and regional territories showed significant increases in oxygen extraction and in lactate levels. Significant increases in venous-arterial (about 9.6 mmHg), portal-arterial (about 12.1 mmHg) and gastric mucosal-arterial (about 18.4 mmHg) PCO2 gradients were also observed. Early fluid replacement, especially with 32 ml/kg volumes of crystalloids, promoted only partial and transient benefits such as increases of about 76 percent in cardiac index, of about 50 percent in portal vein blood flow and decreases in venous-arterial, portal-arterial, gastric mucosal-arterial PCO2 gradients (7.2 ± 1.0, 7.2 ± 1.3 and 9.7 ± 2.5 mmHg, respectively). The fluid infusion promoted only modest and transient benefits, unable to restore the systemic and regional perfusional and metabolic changes in this hypodynamic septic shock model.
Subject(s)
Animals , Dogs , Male , Escherichia coli Infections/drug therapy , Hemodynamics/drug effects , Isotonic Solutions/administration & dosage , Shock, Septic/drug therapy , Disease Models, Animal , Fluid Therapy/methods , Regional Blood Flow/drug effects , Shock, Septic/microbiology , Time FactorsABSTRACT
The effects of various hypertonic solutions on the intraventricular conduction, ventricular repolarization and the arrhythmias caused by the intravenous (iv) injection of bupivacaine (6.5 mg/kg) were studied in sodium pentobarbital-anesthetized mongrel dogs. Hypertonic solutions, given iv 5 min before bupivacaine, were 7.5 percent (w/v) NaCl, 5.4 percent (w/v) LiCl, 50 percent (w/v) glucose (2,400 mOsm/l, 5 ml/kg), or 20 percent (w/v) mannitol (1,200 mOsm/l, 10 ml/kg). Bupivacaine induced severe arrhythmias and ventricular conduction and repolarization disturbances, as reflected by significant increases in QRS complex duration, HV interval, IV interval and monophasic action potential duration, as well as severe hemodynamic impairment. Significant prevention against ventricular electrophysiologic and hemodynamic disturbances and ventricular arrhythmias was observed with 7.5 percent NaCl (percent increase in QRS complex duration: 164.4 ± 21.8 percent in the non-pretreated group vs 74.7 ± 14.1 percent in the pretreated group, P<0.05; percent increase in HV interval: 131.4 ± 16.1 percent in the non-pretreated group vs 58.2 ± 7.5 percent in the pretreated group, P<0.05; percent increase in monophasic action potential duration: 22.7 ± 6.8 percent in the non-pretreated group vs 9.8 ± 6.3 percent in the pretreated group, P<0.05; percent decrease in cardiac index: -46 ± 6 percent in the non-pretreated group vs -28 ± 5 percent in the pretreated group, P<0.05). The other three hypertonic solutions were ineffective. These findings suggest an involvement of sodium ions in the mechanism of hypertonic protection
Subject(s)
Animals , Male , Female , Dogs , Anesthetics, Local , Arrhythmias, Cardiac , Bupivacaine , Heart Conduction System , Saline Solution, Hypertonic , Analysis of Variance , Electrophysiology , Heart Rate , Hemodynamics , Injections, IntravenousABSTRACT
We describe a microprocessor-based programmable triggering instrument designed to control the distribution in time of electrical stimuli delivered to a heart muscle preparation. Sequences of stimuli may be selected among those stored in the non-volatile memory of the instrument and new sequences may be programmed using a repertory of 25 commands. The instrument was used to study the inotropic effects of three irregular sequences of stimuli applied to the isolated rat left atrium. The mean peak tension developed by the tissue was unaltered by stimulus sequences, provided the mean stimulatory frequency (2 or 5 Hz) was maintained. The instrument may be useful to study the effect of different stimulatory patterns on cardiac inotropism, as well as for controlling the electrical simulation of tother biological preparation