Critical care medicine
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Critical care medicine · Oct 1985
Arterial to end-tidal CO2 gradients during spontaneous breathing, intermittent positive-pressure ventilation and jet ventilation.
Arterial to end-tidal CO2 tension gradients were measured in 18 dogs during spontaneous breathing (SB), intermittent positive-pressure ventilation (IPPV), and both low-frequency and high-frequency jet ventilation (LFJV and HFJV). The dogs were anesthetized with nembutal and permitted to breathe spontaneously through an 8-mm internal diameter endotracheal tube; blood gas tensions, cardiac output, and end-tidal CO2 partial pressure (PetCO2) were measured. IPPV, LFJV, and HFJV were then instituted in a random sequence and measurements repeated. ⋯ The mean PaCO2-PetCO2 gradient was 3.7 +/- 1 (SD), 12.6 +/- 5.0, and 24.3 +/- 8 torr during IPPV, LFJV and HFJV, respectively. The large gradients during LFJV and HFJV were not produced by dilution of tracheal CO2 by entrained air or by oxygen delivered by the jet. These results suggest that both LFJV and HFJV may be associated with a large PaCO2-PetCO2 gradient.
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A patient with an apparent dilantin and phenobarbital overdose displayed hypotension and oliguria resistant to usual cardiotonic drugs and volume loading. In addition, she required an unusually high dose of epinephrine for resuscitation. Metoprolol, a beta-blocker not included on the drug screen, was subsequently implicated. An overdose of this drug should be suspected in patients whose hypotension is resistant to usually effective doses of inotropic and chronotropic agents.
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Critical care medicine · Sep 1985
Endocardial and transcutaneous cardiac pacing, calcium chloride, and epinephrine in postcountershock asystole and bradycardias.
Clinically, asystole or a bradyarrhythmia may follow countershock of ventricular fibrillation (VF) in up to 40% of attempts. This study evaluated the effects of artificial cardiac pacing, calcium chloride (CaCl2), and epinephrine in postcountershock asystole/bradycardia. Micromanometer catheters were positioned in the aorta (Ao) and right atrium (RA) of ten dogs and VF induced by right ventricular (RV) stimulation. ⋯ Epinephrine was then given and CPR reinstituted. Epinephrine produced a significant increase in CPR Ao systolic pressure (58 +/- 13 to 84 +/- 24 mm Hg, p less than .001) and end-diastolic coronary perfusion pressure (Ao-RA) (9 +/- 4 to 34 +/- 8 mm Hg, p less than .001). Within 94 +/- 53 sec after epinephrine, spontaneous circulation was restored in eight animals.(ABSTRACT TRUNCATED AT 250 WORDS)
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Critical care medicine · Sep 1985
Hydrochloric acid infusion for treatment of metabolic alkalosis: effects on acid-base balance and oxygenation.
The effects of hydrochloric acid (HCl) administration were studied in 15 critically ill patients whose metabolic alkalosis caused a significant alkalemia (pH 7.50 to 7.58) unresponsive to sodium and potassium chloride administration. Arterial pH and bicarbonate and chloride concentrations normalized after a 6- to 12-h mean infusion of 200 +/- 54 mmol of .25 N HCl. There were no deleterious vascular, hematologic, or metabolic side-effects. ⋯ This increase was comparable in patients breathing spontaneously and those treated with controlled mechanical ventilation, and was attributed at least in part to a decrease in pulmonary shunt. These results indicate that .25 N HCl, infused at the rate of 100 ml/h into the superior vena cava, can correct metabolic alkalosis safely and rapidly. The persistence of the beneficial effects of this treatment on arterial oxygenation remains to be confirmed.
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Critical care medicine · Sep 1985
Hemodynamic effects of positive end-expiratory pressure during high-frequency ventilation.
We studied the intrapleural and hemodynamic effects of positive end-expiratory pressure (PEEP) during high-frequency ventilation (HFV) with a Venturi high-frequency ventilator (Bird). Ten healthy mongrel dogs were anesthetized with sodium pentobarbital, catheterized with intrapleural and thermodilution pulmonary artery lines, and subjected to oleic acid-induced pulmonary edema. A mean PEEP of 16 +/- 6 (SD) cm H2O restored venous admixture to baseline in nine animals. ⋯ Cardiac index (CI) decreased with increments of PEEP in spite of constant transmural central venous and pulmonary capillary wedge pressures, so that oxygen delivery decreased despite increased PaO2. Possible mechanisms of PEEP-induced depression of CI during HFV are discussed. We conclude that both hemodynamic and intrapleural effects of PEEP during HFV are similar to those during conventional mechanical ventilation.