Critical care medicine
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Critical care medicine · Jun 1990
Trending of impedance-monitored cardiac variables: method and statistical power analysis of 100 control studies in a pediatric intensive care unit.
The NCCOM3-R6 monitor continuously monitors cardiac output and five other cardiovascular variables from the thoracic electrical bioimpedance signal. We averaged data over 5-min intervals for 130 min in 100 control studies in 40 pediatric ICU patients, age 0.04 to 20.39 yr (median 1.39) and weighing 2.0 to 59.5 kg (median 8.8). For individual studies, 99% of the 5-min averages of cardiac output fell within +/- 44% of the baseline cardiac output for that study. ⋯ When we averaged data for 100 studies, 5-min interval observations for each variable did not deviate from baseline over a 2-h period (p greater than .70). With a sample size of 100 studies, we could detect a change in cardiac output of +/- 5% at the p less than .005 level with a power of 0.95. We conclude that with a sufficiently large sample size, studies employing the NCCOM3 can detect clinically significant cardiovascular changes due to pharmacologic or procedural stressors.
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Critical care medicine · Jun 1990
Predictive equation for assessing energy expenditure in mechanically ventilated critically ill patients.
Traditional formulas, such as the Harris and Benedict equation (HBE), do not accurately predict energy expenditure (EE) in mechanically ventilated, critically ill patients (MVCIP). The purpose of this study was to develop a predictive EE equation to assess EE requirements in MVCIP. A portable metabolic cart was used to measure indirectly EE in 112 MVCIP. ⋯ The HBE underestimated measured EE by 34 +/- 19% and in 79 patients deviated greater than 15%. Using the new equation, only 15 patients' EE deviated greater than 15% from measured EE. The new predictive EE equation can accurately assess EE in MVCIP.
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Critical care medicine · May 1990
Comparative StudyDetermination of cardiac output during positive end-expiratory pressure--noninvasive electrical bioimpedance compared with standard thermodilution.
Many investigators have demonstrated the accuracy and reliability of thoracic electrical bioimpedance (TEB) in spontaneously breathing patients and under mechanical intermittent positive-pressure ventilation. Most of these studies showed a good correlation between TEB and invasive methods, such as thermodilution (TD) or the Fick method. But during PEEP, contrary results occur when comparing TEB and TD. ⋯ The data revealed a good correlation during ZEEP (r = .93) and during PEEP (r = .91). There was no significant statistical difference when measuring cardiac output by TEB during ventilation with PEEP. During normal or decreased cardiac output, TEB overestimated cardiac output compared with TD, whereas TEB underestimated cardiac output compared with TD during increased cardiac output, especially during PEEP.
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Critical care medicine · May 1990
Age, chronic disease, sepsis, organ system failure, and mortality in a medical intensive care unit.
We retrospectively studied relations between age, pre-existing chronic disease, sepsis, organ system failure, and mortality in 487 patients from a medical ICU. Single organ system failure (SOSF) occurred in 136 (28%) and multiple (greater than or equal to 2) organ system failure (MOSF) in 187 (38%) patients. Cardiovascular and pulmonary failure predominated. ⋯ Advancing age and prior chronic disease may diminish physiologic reserve and predispose to sepsis and MOSF. Although sepsis is a major risk factor for MOSF, a nonspecific host response to critical illness may contribute to the syndrome in 35% of patients. Advancing age, chronic disease, and the number of failing organs, particularly failure of cardiovascular, pulmonary, renal, and neurologic systems, are major determinants of overall mortality, but sepsis is not an independent contributor.
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Critical care medicine · May 1990
Whole blood activated clotting time in infants during extracorporeal membrane oxygenation.
Bleeding complications are the principal cause of morbidity and mortality in infants treated with extracorporeal membrane oxygenation (ECMO). The whole blood activated clotting time (ACT) test is used universally to monitor heparin therapy during this procedure. To enhance our understanding of this test and improve our management of anticoagulation, we studied the relationship between the ACT and blood heparin concentration in nine infants during ECMO. ⋯ The ACT is a low cost, bedside test whose accuracy and precision allow the achievement of target heparin concentrations required in infants during ECMO. Multiple determinations, either in duplicate or serially, are needed to achieve satisfactory precision. These data will be useful in designing future studies to determine the optimal serum heparin concentration to provide adequate anticoagulation, but avoid bleeding complications.