Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CARDIAC OUTPUT”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMedDate not supplied

The effect of patient position on the reproducibility of cardiac output measurements.

OBJECTIVE: To determine the effect of patient position on the reproducibility of cardiac output measurements. DESIGN: Prospective, two-group quasi-experimental design. Convenience sample. SETTING: The study involved two intensive care units in two adult acute care hospitals. PATIENTS: Thirty patients admitted to the intensive care unit who had a thermodilution pulmonary artery catheter in place. Ages ranged from 39 to 80 years (mean of 66.4 +/- 11.3 years). OUTCOME MEASURES: Thermodilution cardiac output measurements. INTERVENTION: The subjects were placed in one of two groups, initially by flipping a coin then into alternate groups. Group A subjects were placed supine, and after 5 minutes had cardiac output measurements performed. They were then placed in the 45-degree upright position, and after an additional 5 minutes had cardiac output measurements performed. Group B subjects were first placed in the 45-degree upright position, and after 5 minutes had cardiac output measurements performed. They were then placed in the supine flat position, and after an additional 5 minutes had cardiac output measurements performed. RESULTS: Seventy percent (n = 30) of the sample population displayed a lower cardiac output in the 45-degree upright position than that obtained in the supine position, with the decrease ranging from 1% to 32% (mean decrease 11%). Forty percent (n = 30) of cardiac output measurements obtained in the 45-degree upright were greater than or equal to 10% less than those obtained in the supine flat position. The differences in cardiac output were analyzed with the paired t test. which produced a 95% confidence interval from -0.539 to -0.083. The two-group Wilcoxon test was used to analyze the mean cardiac output with the patient in the supine, flat position and in the 45-degree upright position. The mean cardiac output at 0 degrees was found to be statistically significant higher (p = 0.0083) than the mean cardiac output at 45 degrees. The effect of coexisting variables was analyzed with the Kruskal-Wallis. The use of vasoconstrictors was the only variable that had a statistically significant change in cardiac output associated with a change in position. CONCLUSIONS: These results indicate that cardiac output measurements are affected by alterations in patient position. To ensure accurate comparisons between consecutive cardiac output measurements, the researchers recommend that the position in which the cardiac output measurements are performed be documented and the cardiac output measurements be conducted in a uniform position.

Adult↗
PubMed2000

Partial CO2 rebreathing indirect Fick technique for non-invasive measurement of cardiac output.

OBJECTIVE: Evaluation in animals of a non-invasive and continuous cardiac output monitoring system based on partial carbon-dioxide (CO2) rebreathing indirect Fick technique. METHODS: We have developed a non-invasive cardiac output (NICO) monitoring system, based on the partial rebreathing method. The partial rebreathing technique employs a differential form of the Fick equation for calculating cardiac output (QT) using non-invasive measurements. Changes in CO2 elimination (deltaVCO2) and partial pressure of end-tidal CO2 (deltaPETCO2) in response to a brief period of partial rebreathing are used to measure pulmonary capillary blood flow (Q(PCBF)). A non-invasive estimate of anatomic and intrapulmonary shunt fraction (Q(S)/Q(T)), based on oxygen saturation from pulse oximetry (SpO2) and inspired oxygen concentration (FIO2), is added to compute total cardiac output [Q(T) = Q(PCBF)/(1 - Q(S)/Q(T))]. The performance of the NICO was compared with iced 5% dextrose bolus thermodilution cardiac output (TDco) measurements in 6 dogs. Cardiac output was varied using dobutamine, and halothane, and by clamping of the inferior vena cava. Two hundred and forty-six (n = 246) paired measurements of TDco and NICO over a range of cardiac outputs (TDco range = 0.60-8.87 l/min) were compared using Bland-Altman analysis and weighted correlation coefficient. RESULTS: The Bland-Altman technique yielded a NICO precision of +/- 0.70 l/min (13.8%) with a mean bias of -0.07 l/min (-1.4%) compared to TDco. The weighted correlation coefficient between TDco and NICO values was: r = 0.93 (n = 246). CONCLUSION: The partial CO2 rebreathing technique for measurement of cardiac output is non-invasive, automated, and based on the well accepted Fick principle. The limits of agreement between NICO and TDco is within the recommended value for NICO to be a clinically acceptable method for cardiac output measurement. The results of this canine study show that NICO performed as well, and in some cases better, than other currently available non-invasive cardiac output techniques over a wide range of cardiac outputs.

Administration, Inhalation↗
PubMed2001

Mathematical coupling does not explain the relationship between right ventricular end-diastolic volume and cardiac output.

OBJECTIVE: To evaluate the clinical significance of mathematical coupling on the correlation between cardiac output and right ventricular end-diastolic volume (RVEDV) through measurement of cardiac output by two independent techniques. DESIGN: Prospective, observational study. SETTING: Surgical intensive care unit in a level 1 trauma center. PATIENTS: Twenty-eight critically ill surgical patients who received mechanical ventilation and hemodynamic monitoring with a pulmonary artery catheter. INTERVENTIONS: A pulmonary artery catheter designed to measure right ventricular ejection fraction (RVEF) and cardiac output by the intermittent bolus thermodilution (TDCO) method and continuous cardiac output by the pulsed thermal energy technique was placed. A computerized data logger was used to collect data simultaneously from the RVEF/TDCO system and the continuous cardiac output system. MEASUREMENTS AND MAIN RESULTS: Two hundred forty-nine data sets from 28 patients were compared. There is statistical correlation between TDCO and continuous cardiac output measurements (r = 0.95, p < 0.0001) with an acceptable bias (-0.11 L/min) and precision (+/-0.74 L/min). The correlation was maintained over a wide range of cardiac outputs (2.3-17.8 L/min). There is a high degree of correlation between RVEDV and both TDCO (r = 0.72, p < 0.0001) and independently measured continuous cardiac output (r = 0.68, p < 0.0001). These correlation coefficients are not statistically different (p = 0.15). CONCLUSIONS: The continuous cardiac output technique accurately approximates cardiac output measured by the TDCO method. RVEDV calculated from TDCO correlates well with both TDCO and independently measured continuous cardiac output. Because random measurement errors of the two techniques differ, mathematical coupling alone does not explain the correlation between RVEDV estimates of preload and cardiac output.

Adult↗
PubMed2000

Cerebral perfusion, cardiac output, and arterial pressure in patients with fulminant hepatic failure.

OBJECTIVE: To evaluate whether changes in cardiac output influence cerebral perfusion directly. In fulminant hepatic failure, the circulation is characterized by wide variations in cardiac output and cerebral blood flow (CBF). DESIGN: A retrospective, interindividual analysis of CBF and cardiac output (part 1) and a prospective evaluation of cerebral perfusion, cardiac output, and arterial pressure during norepinephrine infusion (part 2). SETTING: A four-bed specialist liver failure unit. PATIENTS AND INTERVENTIONS: Twenty patients with fulminant hepatic failure (median age, 43 yrs; range, 17-54; 13 women) maintained on mechanical ventilation (Paco2, 33 torr [4.40 kPa]; range, 26-36 torr [3.47-4.80 kPa) after development of hepatic encephalopathy, stages 3 to 4, had mean arterial pressure (MAP) and cardiac output determined by radial and pulmonary artery catheters. Cerebral perfusion was measured by the 133Xenon clearance technique (n = 8) and by transcranial Doppler sonography, which was used to measure mean flow velocity (Vmean). CBF and Vmean in patients with high cardiac output (>9 L/min) were compared with those with normal or low cardiac output. In the second part of the study, cerebral autoregulation was evaluated by concomitant measurement of Vmean, cardiac output, and MAP during norepinephrine infusion in nine patients. MEASUREMENTS AND MAIN RESULTS: Median cardiac output was 8.5 L/min (range, 3.2-17.3), CBF was 33 mL/100 g/min (12-77 g/min), and Vmean was 45 cm/sec (22-65 cm/sec). In patients with elevated cardiac output, MAP, Vmean, and CBF were similar compared with patients with normal cardiac output. Neither CBF nor Vmean correlated to cardiac output. During norepinephrine infusion, Vmean increased from 49 cm/sec (34-69 cm/sec) to 63 cm/sec (58-90 cm/sec; p < .05), as MAP increased from 75 mm Hg (54-105 mm Hg) to 97 mm Hg (90-128 mm Hg). On average, cardiac output remained unchanged at 5.7 L/min (range, 3.2-17.3), as it increased in five patients and decreased in four patients. The change in Vmean was related to MAP (r2 = .76; p < .01) but not to cardiac output (r2 = .01). CONCLUSION: This study shows that CBF correlates to arterial pressure rather than to cardiac output in patients with fulminant hepatic failure. The presence of pressure-passive cerebral circulation stresses the importance of strict cardiovascular control in securing continuous and sufficient cerebral oxygenation and in avoiding the development of cerebral hyperemia and cerebral edema.

Adolescent↗
PubMed1992

Continuous measurement of cardiac output by the Fick principle: clinical validation in intensive care.

OBJECTIVE: To compare continuous measurement of cardiac output by the Fick principle with the thermodilution cardiac output technique in hemodynamically unstable patients. DESIGN: An open comparison of two methods. SETTING: Multidisciplinary ICU in a university hospital. PATIENTS: Eight patients after coronary bypass surgery and 13 patients with hyperdynamic septic shock. All patients were mechanically ventilated. MEASUREMENTS AND MAIN RESULTS: The continuous Fick cardiac output technique was compared with the thermodilution cardiac output using both warm and cold injection in the coronary artery bypass surgery patients and using warm injection only in the patients with hyperdynamic septic shock. The mean difference between the continuous cardiac output technique and all thermodilution measurements (n = 201) was 0.6 +/- 19%. There was a good correlation between the continuous cardiac output and the warm thermodilution technique (n = 125, r2 = .79; p less than .001). When consecutive measurements with warm and cold thermodilution were compared with the respective Fick-derived values (n = 76), the mean differences between the Fick-derived and the warm and cold thermodilution cardiac output values were 0.2 +/- 1.0 L/min and 0.3 +/- 1.0 L/min, respectively. The relationship between Fick-derived and both methods of thermodilution-derived cardiac output was relatively constant during different modes of ventilatory support. The correlation between the thermodilution measurements with cold and room temperature injectate was weak (r2 = .36; p less than .001), whereas a good correlation was observed between the respective Fick-derived values (r2 = .73; p less than .001). The mean difference between the warm and cold thermodilution cardiac output measurements was 0.1 +/- 1.1 L/min and between the corresponding Fick-derived measurements was 0.01 +/- 0.7 L/min. CONCLUSIONS: Continuous measurement of cardiac output by the Fick principle offers a convenient, reproducible method for hemodynamic monitoring of unstable patients. The variation between the two tested thermodilution techniques is likely to reflect relatively rapid dynamic variation of cardiac output, which is filtered in the 1-min average of cardiac output obtained by the continuous Fick technique.

Adult↗
PubMed1998

Cardiac output responses during exercise in volume-expanded heart transplant recipients.

The mechanisms responsible for immediate adjustments in cardiac output at onset of exercise, in the absence of neural drive, are not well defined in heart transplant (HT) recipients. Seven male HT recipients (mean +/- SD 57 +/- 6 years) and 7 age-matched sedentary normal control subjects (mean age 57 +/- 5 years) performed constant load cycle exercise at 40% of peak power output (Watts). Cardiac output and plasma norepinephrine were determined at rest and every 30 seconds during the first 5 minutes of exercise and at minutes 6, 8, and 10. All subjects were admitted to the General Clinical Research Center for determination of plasma volume. After 3 days of equilibration to a controlled and standardized diet, plasma volume was measured using a modified Evans Blue Dye (T-1824) dilution technique. Heart rate at rest was higher in the HT group (105 +/- 12 vs 74 +/- 6 beats/min), but during submaximum exercise, heart rates in the control group increased more rapidly (p < or = 0.05) and to a greater magnitude (54 +/- 7% vs 17 +/- 4% above rest). Stroke volume at rest was lower in HT recipients (45 +/- 4 vs 68 +/- 9 ml) but was significantly augmented immediately after onset of exercise (30 seconds) and the relative increase was greater than controls at peak exercise (61% vs 38% greater than baseline). Cardiac output at rest was within the normal range in both groups (4.58 +/- 0.27 vs 4.94 +/- 0.40 L/min). Relative increases in cardiac output were similar (p > or = 0.05) for the HT (106 +/- 12%) and control groups (97 +/- 10%). Plasma norepinephrine did not become significantly greater than resting values until approximately 4 minutes after onset of exercise in both groups. Blood volume, normalized for body weight, was 12% greater in the HT group. Thus, HT recipients with expanded blood volume (12%) augment stroke volume immediately after the onset of exercise. Plasma norepinephrine levels contribute negligibly to the rapid adjustment in cardiac output. Rather, we speculate that abrupt on-transit increases in stroke volume are due to augmented venous return, secondary to expanded blood volume.

Blood Volume↗
PubMed2005

Comparison of cardiac output determined by bioimpedance, thermodilution, and the Fick method.

BACKGROUND: Cardiac output can be determined by using a variety of methods. OBJECTIVES: To determine the precision and bias between 3 methods for determining cardiac output: bioimpedance, thermodilution, and the Fick method. METHODS: Cardiac output was determined by using bioimpedance via neck and thorax patches and thermodilution via pulmonary artery catheter in 46 patients in the intensive care unit. A subset of 15 patients also had cardiac output determined by using the Fick method. RESULTS: Mean (SD) cardiac output in all patients was 6.3 (2.2) L/min by thermodilution and 5.6 (2.0) L/min by bioimpedance. In the 15 patients in whom all 3 methods were used, mean cardiac output was 6.0 (1.7) L/min by thermodilution, 5.3 (1.7) L/min by bioimpedance, and 8.6 (4.5) L/min by the Fick method. Bias and precision (mean difference +/- 2 SDs) were 0.7 +/- 2.9 L/min between thermodilution and bioimpedance, 1.7 +/- 3.8 L/min between the Fick method and thermodilution, and 2.4 +/- 4.7 L/min between the Fick method and bioimpedance. CONCLUSION: Bioimpedance, thermodilution, and Fick determinations of cardiac outputs are not interchangeable in a heterogeneous population of critically ill patients.

Aged↗
PubMed1979

Measurement of postoperative cardiac output by thermodilution in pediatric and adult patients.

Serial cardiac output determinations were made by the thermodilution technique in 51 patients by means of a No. 2 Fr. thermistor catheter placed directly into the pulmonary artery at cardiac operation. Correlations were determined prospectively between thermodilution measurements of cardiac output and other commonly used indirect clinical parameters. Serial indicator dye-dilution curves were performed in 24 of these patients and compared with simultaneous thermodilution measurements. A high correlation (r = 0.97) was noted between dye curve measurements of cardiac output and thermal measurements. Statistically significant correlations were also seen between cardiac output and both the quality of the peripheral pulses and the duration of cardiopulmonary bypass, but no significant correlations were found between the measured cardiac outputs and other variables. This study confirms the necessity for direct measurement of cardiac output for its accurate assessment.

Adolescent↗
PubMed2004

Automated cardiac output measurement by transesophageal color Doppler echocardiography.

UNLABELLED: Automated cardiac output measurement (ACOM), which integrates digital color Doppler velocities in space and in time, has been validated using transthoracic echocardiography but has not been tested using transesophageal echocardiography (TEE). Therefore, we determined the feasibility of the ACOM method by TEE in 36 patients undergoing cardiovascular surgery. Regions of interest for ACOM were placed within a color sector across the main pulmonary artery (PA), the mitral annulus, and the left ventricular outflow tract. Cardiac output was determined from the PA flow, the mitral flow, and the left ventricular ejection flow at each view using the ACOM method. We compared measurements of cardiac output derived from the ACOM method with measurements simultaneously obtained by thermodilution (TD). In the mitral flow analysis, the values derived from ACOM correlated well with those from TD (R(2) = 0.85; mean difference = 0.01 +/- 0.58 L/min in the 2-chamber view; R(2) = 0.78; mean difference = -0.10 +/- 0.68 L/min in the 4-chamber view). In the PA flow analysis, the values derived from ACOM did not correlate with those from TD (R(2) = 0.30). In the left ventricular outflow tract analysis, it was very difficult to obtain the optimal view (44%) in which color Doppler flow signals adequately appeared. Using the ACOM method, we obtained good correlation and agreement for cardiac output measurements in the mitral flow analysis compared with TD. The ACOM method is a practical and rapid method to measure cardiac output by TEE analysis of mitral flow. IMPLICATIONS: Automated cardiac output measurement by transesophageal color Doppler echocardiography is a practical and rapid method to measure cardiac output. This technique is a promising new approach to echocardiographic quantification in the intraoperative setting.

Aged↗
PubMed1996

[Cardiac output in patients in their 90's].

Cardiac output was measured by the thermodilution method in nine patients aged 90 to 97 years. The patients were capable of walking in their daily lives before the injury or admission to the hospital, after which they were scheduled for operations. The causes for operations were localized and did not markedly influence general conditions of the patients. After heart rate, arterial blood pressure and mental condition of the patients had been stabilized, their cardiac outputs were determined before the induction of anesthesia. The results are as follows: Cardiac output: 3.58 +/- 0.90 l.min-1, cardiac index: 2.72 +/- 0.57 l.min-1.m-2. Previously published reports in Japan and the results of this study about the relationship between cardiac index and age suggest that as a whole there is a tendency for the cardiac index to decrease with aging.

Aged↗
PubMed1990

Non-invasive determination of cardiac output by Doppler echocardiography and electrical bioimpedance.

Cardiac output measured by thermodilution in 25 patients within 24 hours of acute myocardial infarction was compared with cardiac output measured by Doppler echocardiography (24 patients) and electrical bioimpedance (25 patients). The mean (range) cardiac outputs measured by Doppler (4.03 (2.2-6.0) 1/min) and electrical bioimpedance (3.79 (1.1-6.2) 1/min) were similar to the mean thermodilution value (3.95 (2.1-6.2) 1/min). Both non-invasive techniques agreed closely with thermodilution in most patients. None the less, three results with each method disagreed with thermodilution by more than 1 1/min. Both non-invasive techniques were reproducible and accurate in most patients with acute myocardial infarction. Doppler echocardiography was time consuming and technically demanding. Electrical bioimpedance was simple to use and had the additional advantage of allowing continuous monitoring of the cardiac output.

Aged↗
PubMed1990

The effect of a meal on cardiac output in man at rest and during moderate exercise.

Cardiac output at rest increased by 11-63% in a group of healthy individuals after the consumption of a medium-sized, mixed meal. The maximum post-prandial levels of cardiac output were reached from 10 to 30 min after termination of the meal. Cardiac output values at rest fluctuate around a mean level, and this fluctuation was considerably more marked after a meal, when changes in cardiac output from one 15-s period to another could be of the order of 1-1.5 l min-1. Recording of flow in the superior mesenteric artery before and also after a meal was successful in two subjects in whom anatomical conditions were favourable. Flow in the artery was approximately doubled from the fasting to the post-prandial situation, an augmentation that accounted for about 50% of the concomitant increase in cardiac output. The increases in cardiac output caused by 2-min bouts of standardized, moderate and rhythmic exercise were consistently larger in the post-prandial than in the fasting situation. It thus appears that any tendency for redistribution of blood flow, for example from the gastrointestinal tract to the working muscles, during moderately intense exercise is less marked after a meal than before.

Adult↗
PubMed2001

The effect of cardiac output changes on end-expired volatile anaesthetic concentrations--a theoretical study.

Cardiac output is one of the major determinants of the rate of uptake, and therefore the end-expired concentration (F(E')) of volatile anaesthetic agents. The purpose of this theoretical study was to explore the effect of cardiac output changes on F(E') for a range of volatile anaesthetics. A multicompartment model of anaesthetic uptake and distribution which produces constant values of F(E') was used. The minimum detectable change in cardiac output was determined for a variety of anaesthetic agents for four patterns of cardiac output change. The effect of a step change in cardiac output from 5 to 10 l.min(-1) was also recorded. The smallest cardiac output changes (average 33%) were detected with isoflurane. As blood solubility increased or decreased, larger cardiac output changes were needed before they could be detected. With a large step change in cardiac output and with increasing solubility, the final change in F(E') increased but the initial rate of change of F(E') is decreased. A significant cardiac output change will produce a change in volatile anaesthetic uptake. An unexpected change in F(E') should be considered as a possible signal of a sudden cardiac output change. The difference between agents may represent a balance between the amount of agent taken up and the size of the tissue 'sink' for that agent.

Anesthetics, Inhalation↗
PubMed1998

Aortic and hepatic contrast medium enhancement at CT. Part II. Effect of reduced cardiac output in a porcine model.

PURPOSE: To investigate how reduction in cardiac output affects the magnitude and timing of aortic and hepatic contrast medium enhancement during abdominal computed tomography (CT). MATERIALS AND METHODS: Eight 20-30-kg pigs underwent CT before and after pharmacologic reduction of cardiac output (measured by means of thermodilution). Each CT study consisted of 53 dynamic images acquired every 5 seconds at a fixed level through the midliver after intravenous injection of contrast medium (concentration, 282 mg of iodine per milliliter; dose, 2 mL per kilogram of body weight; injection rate, 2 mL/sec). Curves of contrast medium enhancement versus time were measured. Changes in the magnitude and timing of aortic and hepatic enhancement were compared with the reduction in cardiac output. RESULTS: With reduction in cardiac output, the time from the injection start to the arrival of the contrast medium bolus in the aorta (P < .01) and the times from injection completion to peak aortic (P < .01) and peak hepatic (P < .01) enhancement increased. As cardiac output decreased, peak aortic enhancement increased proportionally (P < .01). Peak hepatic enhancement increased only slightly and correlated weakly with the decrease in cardiac output (P = .07). CONCLUSION: As cardiac output decreases, the times to the arrival of the contrast medium bolus in the aorta and to peak aortic and hepatic enhancement increase. Reduction in cardiac output results in a substantial increase in peak aortic enhancement but not in peak hepatic enhancement.

Animals↗
PubMed1997

Noninvasive monitoring of cardiac output in critically ill patients with thoracocardiography.

Thoracocardiography noninvasively estimates changes in cardiac output by recording ventricular volume curves from an inductive plethysmographic transducer placed around the chest near the xiphoid process. We evaluated performance of thoracocardiography for estimation of cardiac output in 21 critically ill patients in comparison to thermodilution. A total of 201 paired cardiac output measurements were obtained over periods of 35 to 254 min. Since thoracocardiography tracks relative changes in cardiac output but does not provide absolute values, the first cardiac output by thermodilution in each patient was used to calibrate thoracocardiography for comparisons of subsequent cardiac output estimates to thermodilution. The mean difference (bias) of cardiac output (thoracocardiography - thermodilution) was 0.0 L/min, the limits of agreement (bias +/- 2 SD) included a range from -1.5 to +1.6 L/min. For estimations of relative changes in cardiac output by thoracocardiography and thermodilution the bias was 0%, and the limits of agreement -21 and +22%. We conclude that thoracocardiography is a promising noninvasive technique for monitoring cardiac output in critically ill patients.

Adult↗
PubMed1987

Postnatal changes in critical cardiac output and oxygen transport in conscious lambs.

We lowered cardiac output progressively in a controlled, stepwise fashion in conscious, unsedated lambs to determine the critical cardiac output or systemic oxygen delivery (the level at which oxygen consumption decreased abruptly). With the use of incremental inflation of a balloon-tipped catheter placed in the right atrium to lower cardiac output, we examined the response of oxygen consumption, systemic oxygen transport, fractional oxygen extraction, arterial lactate, and blood pressure. We studied lambs at 2 (n = 5), 4 (n = 5), and 8 wk (n = 6) of age and found that the 4-wk-old lambs reached critical values of cardiac output and systemic oxygen transport with the smallest proportional decreases from base-line values. Therefore, the 4-wk-old lambs were the least tolerant of acute decreases in cardiac output. We also found that fractional oxygen extraction was able to increase even after critical systemic oxygen transport was achieved. Furthermore, we found at every age that lactic acid accumulation began when the critical level of cardiac output was reached.

Aging↗
PubMed1981

Ventilatory responses to cardiac output changes in patients with pacemakers.

Cardiac output changes were induced by step changes of heart rate (HR) in six patients with cardiac pacemakers during monitoring of ventilation and gas exchange, breath-by-breath. Mean low HR was 48 beats/min; mean high HR was 82 beats/min. The change of oxygen uptake immediately after the HR change was used as an index of altered cardiac output. After HR increase, oxygen uptake (V02) rose by 34 +/- 20% (SD), and after HR decrease, Vo2 fell by 24 +/- 11%. There was no change in arterial blood pressure. After HR increase, ventilation increased, after a mean delay of 19 +/- 4 s; after HR reduction, ventilation fell, after a mean delay of 29 +/- 7 s. In the period between HR increase and the resulting increase in ventilation, end-tidal PCO2 (PETCO2) rose by 2.6 +/- 2.0 Torr, and in the period between HR decreases and the fall in ventilation, PETCO2 dropped by 2.9 +/- 2.2 Torr. The response time and end-tidal gas tension changes implicate the chemoreceptors in the reflex correction of blood gas disturbances that may result from imbalances between cardiac output and ventilation.

Adult↗
PubMed1977

Monitoring of cardiac output by thermodilution after open-heart surgery.

One hundred twenty-five separate cardiac output determinations were obtained after open-heart surgery in 10 patients by simultaneous use of thermodilution and dye-dilution techniques. Mean thermodilution cardiac output was 1.6 per cent greater than mean dye-dilution cardiac output (5.24 versus 5.16 L. per minute). Reproducibility of thermodilution cardiac output (coefficient of variation, 8.6 per cent) was superior to that of dye-dilution cardiac output (coefficient of variation, 12.3 per cent) for outputs ranging from 2.5 to 8.7 L. per minute (p less than 0.001). Linear regression analysis revealed a correlation showing that COtd = 0.86 COdye + 0.80 (r = 0.9, p less than 0.001) and indicating a similarity between thermodilution and dye-dilution output figures except in extremely low output states. In such cases, thermodilution cardiac output becomes progressively larger than dye-dilution cardiac output. The results indicate that thermodilution cardiac output is a valid method for determining cardiac output in the rapidly changing clinical setting following cardiopulmonary bypass. Clinical applications of this technique include evaluation of the efficacy of inotropic agents, effectiveness of intra-aortic balloon counterpulsation, and status of the low output syndrome postoperatively. Routine use in patients with Class III or IV cardiac disease appears justified.

Cardiac Output↗