June Zaccari

Noninvasive Cardiac Output: Simultaneous Comparison of Two Different Methods with Thermodilution

The authors attempted to simultaneously measure cardiac output by thermodilution (COtd), thoracic bioimpedance (CObi), and suprasternal Doppler ultrasound (COdopp) in 68 patients. Subgroups separately compared included patients whose lungs were mechanically ventilated, patients undergoing cardiac surgery, aortic surgery, patients with dysrhythmias, and patients with sepsis. The authors also studied the value of the ventricular ejection time (VET) in evaluating the agreement of CObi and COdopp with COtd. Simultaneous CObi and COtd were available in a total of 56 patients (416 data sets) with an overall correlation coefficient r = 0.61, regression slope (m) of 0.52, intercept (y) of 2.46, and mean (CObi-COtd) difference (bias) of -0.67 +/- 1.72 (SD) l/min. Simultaneous COdopp and COtd were available in 59 patients (446 data sets) with an overall r = 0.51, m of 0.53, y of 2.05, and bias of -0.79 +/- 1.95 l/min. CObi agreed most closely with COtd in patients whose lungs were mechanically ventilated, who had not undergone cardiac or aortic surgery, and with VET difference less than 40 ms (16 patients, 99 data sets; r = 0.74; m = 0.97; y = 0.15; bias = -0.02 +/- 1.53 l/min). COdopp agreed most closely with COtd in patients whose lungs were mechanically ventilated, who had not undergone cardiac or aortic surgery, and in sinus rhythm with VET difference less than 40 ms (10 patients, 45 data sets; r = 0.82; m = 0.98; y = -0.07; bias = -0.82 +/-1.03 l/min). VET by radial artery can help evaluate the reliability of CObi and COdopp.

Changes in cardiac output after acute blood loss and position change in man

Thoracic bioimpedance cardiac output (Qtbi) was measured at 1-min intervals in 27 volunteers before, during, and after withdrawing 500 ml (3.7 to 8.5 ml/kg; mean 5.8) of blood. The effects of passive leg raising (PLR) and standing on Qtbi were measured before and after blood withdrawal. Arterial oxygen saturation (SaO2), transcutaneous oxygen tension (PtcO2), mean arterial BP (MAP), and heart rate (HR) were also measured before and after blood withdrawal. Thoracic bioimpedance cardiac index (CI) decreased 18% (0.8 +/- 0.1 L/min.m2, p less than .0001) and stroke volume index (SI) decreased 22% (14.8 +/- 2.7 ml/beat.m2, p less than .0001) after blood withdrawal. HR, MAP, SaO2, and PtcO2 were not significantly different after blood withdrawal. Before blood withdrawal PLR increased CI 6.8% (0.3 +/- 0.1 L/min.m2, p less than .0001); after blood withdrawal PLR increased CI 11.1% (0.4 +/- 0.1 L/min.m2, p less than .0001). PLR can increase stroke volume and cardiac output in hypovolemic humans.

Acute cardiovascular response to passive leg raising

Cardiac output by thoracic bioimpedance, heart rate, BP, oxygen saturation, and transcutaneous oxygen tension were measured at 1-min intervals in 45 patients before and after passive leg raising (PLR). Mean cardiac index increased only 0.09 ± 0.02 (SEM) L/min ċ m2 (p < .001), mean transcutaneous oxy

Comparison of changes in transit time ultrasound, esophageal Doppler, and thermodilution cardiac output after changes in preload, afterload, and contractility in pigs

The purpose of this study was to compare how well changes in cardiac output (CO) measured by esophageal Doppler (Doppler) and thermodilution (TD) followed changes in CO measured by transit time ultrasound (TTU). Simultaneous Doppler, TD, and TTU measurements of CO were made before and after changes in preload, afterload, or contractility in seven piglets. Mean changes in each CO method for each type of change in CO were compared by analysis of variance. Changes in TTU CO, TD CO, and Doppler CO were compared by correlation, linear regression, and bias and precision statistics.Of 86 TTU changes in CO > 10%, Doppler changed the same direction as TTU 59 times, changed in an opposite direction 6 times, and changed > 10% 21 times. Thermodilution changed in the same direction as TTU 72 times, in the opposite direction 4 times, and changed < 10% 10 times.Changes (%Δ) in TTU and TD measurements of CO were not significantly different in any group. Changes in Doppler CO and TTU CO were different for two afterload and contractility groups. Percent changes in Doppler CO had a correlation coefficient (r) = 0.74, m = 0.72, and bias (mean % Δ Doppler CO - mean %Δ TTU CO) = 6.3 ± 29.7 with % Δ TTU CO. Percent changes in TD CO had an r = 0.90, m = 0.92, and bias = 5.7 ± 19.1 with %Δ TTU CO. Cardiac output measured by Doppler underestimated changes in CO due to changes in preload and contractility and exaggerated changes in CO due to changes in afterload.

Continuous fiberoptic arterial oxygen tension measurements in dogs

An experimental study using a new fiberoptic sensor for the continuous intraarterial measurement of oxygen tension is described. This “optode” sensor uses the phenomenon of fluorescence quenching to determine the oxygen tension of the surrounding medium. To assess the accuracy of this device, we anesthetized 4 dogs and monitored them continuously with arterial catheters and an intraarterial optode probe, and intermittently with arterial blood gas analysis. The inspired oxygen fraction was varied from 1.0 to 0.1, and arterial blood gases were measured for comparison with the optode reading. Two hundred ninety data sets yielded a correlation coefficient of 0.96, with a linear regression slope of 0.98 and intercept of 5.1 mm Hg. In the 72 data sets from the last dog, the bias and precision of the optode arterial oxygen tension values were −10.3 mm Hg and 20.0 mm Hg, respectively. The optode probe was easily inserted through a 20-gauge catheter and did not interfere with continuous arterial pressure measurement or blood sampling. This study suggests that the optode has great potential as a continuous, real-time monitor of arterial oxygen tension.

Continuous noninvasive estimation of cardiac output by electrical bioimpedance: an experimental study in dogs

A new device has been developed to estimate continuously and noninvasively cardiac output from the thoracic electrical bioimpedance (CObi). CObi was compared to cardiac output by thermodilution (COtd) in five anesthetized dogs. Blood pressure, blood volume, and blood flow were manipulated by hemorrhage and infusions of sodium nitroprusside and phenylephrine. These data were used to determine the correlation between CObi and COtd under conditions of hypotensive normal flow and normotensive low flow, as well as during hemorrhagic shock and resuscitation. The CObi device was calibrated in vivo to COtd for each dog at the beginning of each experiment. CObi had a significant positive correlation with COtd throughout the experiments (r = 0.84, slope = 0.91, intercept = 0.55, p < .001), and CObi predicted COtd with a standard error of the estimate of 0.81 L/min. Neither heart rate nor mean arterial pressure was significantly correlated with COtd or CObi. During severe hemorrhagic shock, CObi could not determine cardiac output in two of the dogs when COtd averaged 1.7 L/min. These data indicate that CObi is a blood-flow related variable that can be monitored continuously.

Liquid-gas partition coefficients of halothane and isoflurane in perfluorodecalin, fluosol-DA, and blood/fluosol-DA mixtures.

In 1966, Leland Clark and Frank Gollan dramatically demonstrated the oxygen-carrying capability of perfluorochemicals (PFC) with the survival of mice completely immersed in a fluorocarbon liquid (1). Since then, stable, inert, aqueous emulsions of perfluorochemicals that act as oxygen transport fluids during complete exchange transfusions in animals have been prepared (2-6). In 1979, adult volunteers were given the perfluorochemical emulsion Fluosol-DA, 20% (Green Cross, Osaka, Japan), and initial clinical studies were begun in Japan and in the United States (7-9). The perfluorochemicals in Fluosol are perfluorodecalin (14 g/100 ml) and perfluorotripropylamine (6 g/100 ml). The solubility of oxygen in these perfluorochemicals is very high. At one atmosphere of oxygen and 37T, perfluorodecalin and perfluorotripropylamine dissolve 45 and 48 rnl of oxygen per 100 ml of liquid, respectively (9). Because the solubility of oxygen in perfluorochemicals is approximately 20 times greater than the solubility of oxygen in water, it is likely that other gases and vapors have high solubility in PFCs. Although nothing has been reported regarding prolonged induction of, or emergence from, general anesthesia in volunteers given perfluorochemicals, the partition coefficient (A) of volatile anesthetics might be expected to be larger in PFCs than in blood (9). The purpose of this study was to measure the A of halothane and isoflurane in a pure PFC, in the clinical emulsion Fluosol (FDA), and in mixtures of blood and Fluosol.

Changes in renal vein, renal surface, and urine oxygen tension during hypoxia in pigs

AbstractTo determine whether ureteral urine oxygen tension could serve as a monitor of renal hypoxia and its relationship to other renal O2 tension parameters, we simultaneously measured femoral artery (PaO2), renal vein (Pr

ACCURACY OF A PULSE OXIMETER IN THE CRITICALLY ILL ADULT: EFFECT OF TEMPERATURE AND HEMODYNAMICS

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