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PubMed2001

Estimation of changes in cardiac output from the arterial blood pressure waveform in the upper limb.

We have developed a new pulse contour cardiac output (PulseCO) algorithm based on frequency analysis studies of the arterial system. PulseCO was compared with thermodilution cardiac output (TDCO) in 10 patients undergoing cardiac surgery. Results from one patient were unsuitable for analysis. In the remaining nine patients, 142 TDCO determinations were compared with PulseCO after logarithmic transformation and after being normalized by the initial cardiac output in each patient. Each determination was usually the average of three measurements. Least squares regression gave y = 0.77 x (r2 = 0.81) and the limits of agreement were from -26% to +21%. The accuracy of PulseCO in determining short-term changes in cardiac output was assessed by comparing the ratios of consecutive PulseCO determinations with the ratios of the corresponding, consecutive TDCO determinations. Least squares regression gave y = 0.71 x (r2 = 0.70) and the limits of agreement were from -21% to +25%. After phenylephrine had been given to five patients, PulseCO showed an increase in systemic vascular resistance consistent with the known pharmacological actions of the drug. The PulseCO algorithm was incorporated into a computer program that acquires arterial pressure data from an analogue-to-digital converter and displays beat-to-beat trend values.

Aged↗
PubMed2000

Use of transesophageal Doppler ultrasonography in ventilated pediatric patients: derivation of cardiac output.

OBJECTIVE: To ascertain if cardiac output (CO) could be derived from blood flow velocity measured in the descending aorta of ventilated children by transesophageal Doppler ultrasonography (TED) without the need for direct aortic cross sectional area measurement, and to evaluate the ability of TED to follow changes in CO when compared with femoral artery thermodilution. DESIGN: Prospective, comparison study. SETTING: A 16-bed pediatric intensive care unit of a university hospital. PATIENTS: A total of 100 ventilated infants and children aged 4 days to 18 yrs (median age, 27 months). Diagnoses included postcardiac surgery (n = 58), sepsis/multiple organ failure (n = 32), respiratory disease (n = 5), and other (n = 5). A total of 55 patients were receiving inotropes or vasodilators. INTERVENTIONS: When patients were hemodynamically stable, a TED probe was placed into the distal esophagus to obtain optimal signal, and minute distance (MD) was recorded. Five consecutive MD measurements were made concurrently with five femoral artery thermodilution measurements, and the concurrent measurements were averaged. CO was then manipulated by fluid administration or inotrope adjustment, and the readings were repeated. MEASUREMENTS AND MAIN RESULTS: Femoral artery thermodilution CO ranged from 0.32 to 9.19 L/min, (median, 2.46 L/min), and encompassed a wide range of high and low flow states. Theoretical consideration revealed the optimal TED estimate for CO to be (MD x patient height2 x 10(-7)). Linear regression analysis yielded a power function model such that: estimated CO = 1.158 x (MD x height2 x 10(-7))(0.785), r2 = 0.879, standard error of the estimate = 0.266. Inclusion of a correction factor for potential changes in aortic cross-sectional area with hypo- and hypertension did not appreciably improve the predictive value of the model. MD was able to follow percentage changes in CO, giving a mean bias of 0.87% (95% confidence interval -0.85% to 2.59%), and limits of agreement of +/- 16.82%. The median coefficient of variation for MD was 3.3%. CONCLUSIONS: TED provides a clinically accurate estimate of CO across the entire pediatric age range and is able to follow changes in CO.

Adolescent↗
PubMed1997

Estimation of mixed venous PCO2 for determination of cardiac output in children.

STUDY OBJECTIVES: Cardiac output (Q) can be estimated noninvasively during exercise by employing CO2-rebreathing techniques (equilibrium and exponential) to estimate the oxygenated mixed venous PCO2 (PvCO2). It has been found in adults and children that the equilibrium method underestimates Q as a result of overestimation of PvCO2, unless PvCO2 is "downstream corrected." In adults, it has been found that the exponential method does not require downstream correction and yields values similar to those obtained by the equilibrium method with downstream correction. The objectives of this study were as follows: to test whether the exponential method gives similar results to the equilibrium method with downstream correction in children; to verify that downstream correction is required in children; and to test whether a single equation could be used in adults and children to predict Q from oxygen consumption (VO2). DESIGN: Descriptive. SETTING: Exercise laboratory of a university hospital. PARTICIPANTS: 23 children (16 boys, 7 girls) with a mean age of 11.0 +/- 1.9 years (7.1 to 13.9 years), and 12 adults (7 men, 5 women) with a mean age of 33.6 +/- 7.2 years (24 to 48 years). INTERVENTIONS: While performing steady-state exercise on an ergometer, PvCO2 was determined in 14 children using both the equilibrium and exponential methods, and in all other subjects using the equilibrium method alone. MEASUREMENTS AND RESULTS: For the 14 children who underwent testing by both the equilibrium and exponential methods, the uncorrected equilibrium PvCO2 was significantly different from both the corrected PvCO2 and the exponential PvCO2. We found a strong relationship between Q (L/min), calculated using the downstream corrected values of PvCO2, and VO2 (L/min) (r2 = 0.95), and this relationship was similar to that obtained by dye dilution in other studies. When weight was included, it was determined that one equation could be used for children and adults: Q (L/min) = 1.42 + 5.80.VO2 (L/min) + 0.06.wt (kg), r2 = 0.97, SEY = 0.67. CONCLUSIONS: CO2-rebreathing techniques can be used to determine Q in children; the exponential method gives values that are similar to the equilibrium method with the downstream correction; and one prediction can be used for Q in adults and children.

Adolescent↗
PubMed1999

Continuous cardiac output in septic shock by simulating a model of the aortic input impedance: a comparison with bolus injection thermodilution.

BACKGROUND: To compare continuous cardiac output obtained by simulation of an aortic input impedance model to bolus injection thermodilution (TDCO) in critically ill patients with septic shock. METHODS: In an open study, mechanically ventilated patients with septic shock were monitored for 1 (32 patients), 2 (15 patients), or 3 (5 patients) days. The hemodynamic state was altered by varying the dosages of dopamine, norepinephrine, or dobutamine. TDCO was estimated 189 times as the series average of four automated phase-controlled injections of iced 5% glucose, spread equally over the ventilatory cycle. Continuous model-simulated cardiac output (MCO) was computed from radial or femoral artery pressure. On each day, the first TDCO value was used to calibrate the model. RESULTS: TDCO ranged from 4.1 to 18.2 l/min. The bias (mean difference between MCO and TDCO) on the first day before calibration was -1.92 +/- 2.3 l/min (mean +/- SD; n = 32; 95% limits of agreement, -6.5 to 2.6 l/min). The bias increased at higher levels of cardiac output (P < 0.05). In 15 patients studied on two consecutive days, the precalibration ratio TDCO:MCO on day 1 was 1.39 +/- 0.28 (mean +/- SD) and did not change on day 2 (1.39 +/- 0.34). After calibration, the bias was -0.1 +/- 0.8 l/min with 82% of the comparisons (n = 112) < 1 l/min and 58% (n = 79) < 0.5 l/min, and independent of the level of cardiac output. CONCLUSIONS: In mechanically ventilated patients with septic shock, changes in bolus TDCO are reflected by calibrated MCO over a range of cardiac output values. A single calibration of the model appears sufficient to monitor continuous cardiac output over a 2-day period with a bias of -0.1 +/- 0.8 l/min.

Adult↗
PubMed1976

Hepatic blood flow and cardiac output during Fluoromar anaesthesia. An animal study.

Related values of cardiac output and hepatic blood flow were measured in eight premedicated (pethidine 10 mg/kg b.w.) dogs under varying depths of fluoromar anaesthesia. The measurements were first taken under basis anaesthesia with barbiturate (mebumal natrium 25 mg/kg b.w.) gallamine (80 mg)-N2O-O-O2 (ratio 2 to 1) with controlled normoventilation, and then under increasing depths of fluoromar anaesthesia: increasing stepwise to 1 1/2-3 and 6% inspiratory concentrations. Finally the measurements were repeated after the fluoromar had been discontinued. Using the basis anaesthesia as a reference, it was found that 6% fluoromar gave a reduction in cardiac output (34%), heart rate (11%) and mean pressure in the aorta (18%). The peripheral resistance was simultaneously increased by 22%. The effect on the splanchnic blood flow was far less and without significant changes from one step in the anaesthesia to the next. Using 6% fluoromar it was found that there was a maximum reduction in blood flow of 20% of the initial value. There was unchanged splanchnic resistance during the whole of the investigation. After discontinuation of the fluoromar for 15 min and continued controlled ventilation (O2-N2O), rising heart rate and blood pressure were observed; however, cardiac output and splanchnic blood flow were unchanged. Corresponding to this, an additional increase in peripheral resistance of 10% and an insignificant increase of 5% in the splanchnic resistance were observed.

Anesthesia, Inhalation↗
PubMed2004

Arteriovenous fistula-associated high-output cardiac failure: a review of mechanisms.

High-output cardiac failure can be a rare complication of high-output arteriovenous fistula. The authors present a case in which a hemodialysis patient with a high-flow arteriovenous fistula has cardiac failure that improves with fistula closure. The hemodynamic effects of a fistula are reviewed, and the hemodialysis literature regarding high-output cardiac failure is summarized. To gain insight into the problem of high-output cardiac failure, research efforts should focus on the prospective monitoring of high-access flows.

Aged↗
PubMed1977

Effect of cardiac output on circulatory blood volume.

In anesthetized dogs venous return was drained into a blood reservoir from which blood was pumped to the right atrium at a variable perfusion rate, which was equal to cardiac output in the steady state. When cardiac output was decreased or increased by 25 or 50 percent of the control, the blood volume in the dog's body was changed in the same direction in the intact reflexic state as well as in the areflexic state prepared by hexamethonium and norepinephrine infusion. The volume change in the reflexic state was twice that in the areflexic state when compared 5 min after stepwise changes in cardiac output. When only the flow through the right heart and lungs was changed by-50 percent, with systemic flow unchanged, the decrease in blood volume was about one-fifth of that observed on a 50 percent decrease of cardiac output and not affected by ablation of the reflexes. It is concluded that, on a change in cardiac output, the passive change in blood volume is as large as the active or reflexic change, that the majority of the change in blood volume takes place in the systemic circulation rather than in the pulmonary circulation, and that the receptors for the reflexic change are located in the systemic circulation.

Animals↗
PubMed1991

Single- versus dual-chamber sensor-driven pacing: comparison of cardiac outputs.

Previous studies have shown that single-chamber sensor-driven pacing improves exercise tolerance for patients with chronotropic incompetence. However, long-term single-chamber pacing has a number of inherent problems that limit its usefulness. Although sensor-driven dual-chamber pacing largely obviates the problems inherent with single-chamber sensor-driven pacing, the physiologic benefit of dual-chamber sensor-driven pacing has not yet been demonstrated. Accordingly, the purpose of this study was to compare exercise-induced cardiac output for patients with chronotropic incompetence, after programming their pacemakers to either a simulated sensor-driven single or simulated dual-chamber mode. Cardiac output was measured noninvasively at rest and peak exercise using standard Doppler-derived measurements, obtained in a blinded fashion. At rest the Doppler-derived resting VVI and DDD cardiac outputs were 4.49 +/- 0.3 L/min and 4.68 +/- 0.3 L/min, respectively. At peak exercise, the DDD cardiac output was 5.07 +/- 0.5 L/min, whereas the simulated activity VVI and DDD cardiac outputs were 6.33 +/- 0.6 L/min and 7.41 +/- 0.70 L/min, respectively. Analysis of variance showed that there was an overall significant difference in cardiac output from rest to peak exercise (p less than 0.001). However, only the simulated activity DDD cardiac output was significantly different from its respective control value (p less than 0.05). Thus this study shows for the first time that the addition of rate responsiveness to dual-chamber pacing results in a significant improvement in cardiac output for patients with chronotropic incompetence.

Aged↗
PubMed1994

[Comparison of cardiac output measured continuously by thermodilution and calculated according to Fick's principle].

Recently, a thermodilution technique for continuous measurement of cardiac output was introduced. The aim of this study was to evaluate the accuracy of continuous cardiac output measurement using the thermodilution technique (CCO) and to assess the correspondence between CCO and cardiac output obtained with the Fick's principle (Fick-CO). Nine patients were studied in the postoperative period after cardiac surgery. A new pulmonary artery catheter modified by attachment of a thermal filament (Intellicath, Model PA3-H-8Fr) was inserted and connected to a continuous cardiac output computer (Vigilance Monitor). Oxygen consumption was continuously measured using the gas exchange method (Deltatrac Metabolic Monitor). Fick-CO was calculated according to the Fick's principle. The study in each patient consisted of 6 serial determinations of both CCO and Fick-CO at 10 min intervals. For 54 pairs of measurements, the mean difference (Fick-CO-CCO) was 0,6 L.min-1. The limits of agreement were--0,6 to 1,8 L.min-1 respectively. The relative error was 6% for CCO and 10% for Fick-CO. It is concluded that CCO and Fick-CO cannot be considered as being interchangeable. However, the accuracy of CCO is acceptable. The technique does not require any user calibration and eliminates the need of bolus injections. Further studies are necessary to determine the benefits of this new technique in the various clinical situations.

Aged↗
PubMed1994

[Primary plasma cell leukemia complicated with high-output cardiac failure and hyperammonemia].

A 23-year-old male patient with plasma cell leukemia showed characteristic clinical features: accelerating heart failure and consciousness disturbance accompanied with an increase of plasma cells in peripheral blood. Evaluation of cardiac function revealed a hyperdynamic cardiac state with low somatic vascular resistance, indicating high-output cardiac failure. However no disorders causing high-output cardiac failure were found. Consciousness disturbance and hyperammonemia with serum amino acid abnormality of unknown origin were also demonstrated. After intensive combined chemotherapy (MVD + VAD), high-output cardiac failure and hyperammonemia improved with disappearance of plasma cells, suggesting that these symptoms were closely related with progression of plasma cell leukemia.

Adult↗
PubMed1993

End-tidal CO2 changes under constant cardiac output during cardiopulmonary resuscitation.

OBJECTIVES: To evaluate a) whether end-tidal CO2 values change under constant cardiac output during cardiopulmonary resuscitation (CPR), and b) what factors are responsible for the change. DESIGN: A cohort study. SETTING: University research laboratory. SUBJECTS: Nine mongrel dogs. INTERVENTIONS: Ventricular fibrillation was electrically induced. After 2 mins, open-chest cardiac massage was initiated to maintain cardiac output at 0.2 L/min (23% of baseline cardiac output) by the measurement of blood flow with an electromagnetic flow probe on the ascending aorta. The cardiac massage was kept constant until 50 mins after the induction of ventricular fibrillation. MEASUREMENTS AND MAIN RESULTS: Before and during ventricular fibrillation, end-tidal CO2, minute volume of alveolar ventilation, and CO2 excretion were continuously monitored. Blood gases and oxygen saturation values were also measured in arterial and the mixed venous blood samples. CO2 content was calculated. After induction of ventricular fibrillation, end-tidal CO2 decreased and thereafter continued to increase until the end of the experiment. Two mechanisms may have contributed to the early reduction in end-tidal CO2. One mechanism is a further decrease in CO2 excretion compared with the reduction in alveolar ventilation and the other is an increase in alveolar deadspace (estimated from the increase in the difference between PaCO2 and end-tidal CO2). The subsequent increase in end-tidal CO2 was mainly due to a change in CO2 excretion. There are two hypotheses concerning the subsequent increase in CO2 excretion: the increase in pulmonary capillary blood flow (estimated from the change in the arteriovenous CO2 content gradient) and the increase in CO2 production itself. CONCLUSIONS: End-tidal CO2 changes under constant cardiac output during CPR. When end-tidal CO2 is used to estimate the effectiveness of the cardiac massage, this type of change must be recognized.

Animals↗
PubMed1988

Regional distribution of cardiac output at rest and during exercise in patients with exertional angina pectoris before and after nifedipine therapy.

The short-term effects of sublingual nifedipine (20 mg) on cardiac output and its distribution at rest and during exercise were evaluated by measurement of iliofemoral blood flow and cardiac output in 10 men with stable angina pectoris controlled by metoprolol. At rest, nifedipine significantly decreased iliofemoral vascular resistance from 294 +/- 36 to 165 +/- 29 dynes.s.cm-5.10(2) (p less than 0.01) and significantly increased iliofemoral blood flow from 0.34 +/- 0.04 to 0.57 +/- 0.11 liters/min (p less than 0.05). Systemic vascular resistance was reduced from 19 +/- 1 to 13 +/- 1 dynes.s.cm-5.10(2) (p less than 0.001) and cardiac output increased significantly from 4.7 +/- 0.3 to 5.8 +/- 0.5 liters/min (p less than 0.05). Mean arterial pressure decreased significantly and heart rate increased significantly. During maximal upright bicycle exercise during nifedipine therapy, iliofemoral vascular resistance and leg blood flow were unchanged compared with control (23 +/- 2 versus 21 +/- 3 dynes.s.cm-5.10(2) and 4.7 +/- 0.5 versus 4.4 +/- 0.6 liters/min), cardiac output remained significantly increased (12.8 +/- 0.8 to 15.2 +/- 1.2 liters/min, p less than 0.05) and systemic vascular resistance remained significantly reduced (8 +/- 1 to 5 +/- 1 dynes.s.cm-5.10(2); p less than 0.001). The proportion of cardiac output distributed to the working lower limbs was significantly reduced at all exercise levels. In summary, nifedipine caused a redistribution of cardiac output by vasodilating nonexercising vascular beds without altering the locally mediated vasodilation in exercising muscle. In patients with coronary artery disease given nifedipine therapy, an increase in exercise tolerance is due to relief of myocardial ischemia rather than to increased peripheral oxygen delivery.

Adult↗
PubMed1991

Effect of ventilation and cardiac output on the uptake of anaesthetic agents from different breathing systems: a theoretical study.

We have investigated the influences of ventilation and cardiac output on uptake of anaesthetic with different breathing systems, by analysis of simple equations and by computer simulation. Increases in cardiac output and ventilation increased uptake from those systems which provided a constant inspired concentration, but not from completely closed systems with the vaporizer out of the circle (VOC), or when using the technique described by Lowe and Ernst. When the vaporizer was inside the circle, uptake increased with ventilation but not with cardiac output. With servo control of endtidal concentration, uptake increased with cardiac output but not with ventilation. When the fresh gas flow to VOC systems was increased from basal, independence of uptake from ventilation was well maintained until fresh gas flow approached alveolar ventilation, but the independence of uptake from cardiac output was lost much sooner.

Anesthesia, Closed-Circuit↗
PubMed2004

Pulse dye densitometry using indigo carmine is useful for cardiac output measurement, but not for circulating blood volume measurement.

BACKGROUND AND OBJECTIVE: We evaluated the validity of a newly developed pulse dye densitometer for indigo carmine for measuring cardiac output and circulating blood volume. METHODS: Measurements of cardiac output and circulating blood volume were performed with the indigo carmine densitometer during normovolaemia, hypovolaemia and hypervolaemia in nine mongrel dogs under general anaesthesia. The validity was evaluated by comparison of the values of cardiac output and circulating blood volume obtained by the thermodilution technique and the 51Cr-labelled red blood cell method, respectively. We also examined indigo carmine removal by continuous veno-venous haemofiltration after indigo carmine injection. RESULTS: There was good agreement between dye densitometer- and thermodilution-derived cardiac output (r = 0.885, P < 0.001). The bias and limits of agreement of these values were 0.09 and+/-1.07 L min(-1) (2 SD, n 22), respectively. The dye-densitometer-derived circulating blood volume was greater than that of the 51Cr-labelled red blood cell method, and both values showed weak agreement (r = 0.587, P < 0.027). The sieving coefficient of indigo carmine through continuous veno-venous haemofiltration was 0.34+/-0.06. CONCLUSIONS: These data indicate that indigo carmine densitometry is a reliable method for cardiac output determination, but it overestimates circulating blood volume, probably due to the transition of indigo carmine into the extravascular space in the systemic circulation.

Algorithms↗
PubMed1993

Validity of cardiac output measurement by the thermodilution method in the presence of acute tricuspid regurgitation.

Evaluation of patients with acute tricuspid insufficiency may include assessment of cardiac output by the thermodilution method. The accuracy of estimates of thermodilution-derived cardiac output in the presence of tricuspid insufficiency has been questioned. This study was designed to determine the validity of the thermodilution technique in a canine model of acute reversible tricuspid insufficiency. Cardiac output as measured by thermodilution and electromagnetic flowmeter was compared at two grades of regurgitation. The relationship between these two methods (thermodilution/electromagnetic) changed significantly from a regression slope of 1.01 +/- 0.18 (mean +/- standard deviation) during control conditions to a slope of 0.86 +/- 0.23 (p < 0.02) during severe regurgitation. No significant change was observed between control and mild regurgitation or between the initial control value and a control measurement repeated after tricuspid insufficiency was reversed at the termination of the study. This study shows that in a canine model of severe acute tricuspid regurgitation the thermodilution method underestimates cardiac output by an amount that is proportional to the level of cardiac output and to the grade of regurgitation.

Acute Disease↗
PubMed1997

The peri-operative use of the oesophageal Doppler monitor in patients undergoing coronary artery revascularisation. A comparison with the continuous cardiac output monitor.

This study was carried out to evaluate the ease of use and reliability of cardiac output estimations performed by an oesophageal Doppler monitor and to compare its use with that of a continuous cardiac output pulmonary flotation catheter. Measurements were made during and after surgery in 16 patients scheduled to undergo coronary revascularisation. Both devices suffered significant intra-operative problems which led us to question their suitability as operating theatre monitors. After surgery the continuous cardiac output monitor provided stable results while the oesophageal Doppler monitor required the continuous presence of an experienced anaesthetist to ensure comparable cardiac output estimations.

Aged↗
PubMed1997

Hepatic and gastrointestinal oxygen and lactate metabolism during low cardiac output in lambs.

We previously observed young lambs to be more tolerant of hypoxia; compared with older lambs, they accumulate lactate at a slower rate during comparable reduction in cardiac output, and have a greater percent decrease in cardiac output before onset of systemic lactate accumulation. To determine the mechanism of lactic acidosis and the cause for this "tolerance," we reduced cardiac output progressively in seven chronically catheterized conscious lambs (16.4 + 5.1 d) and measured hepatic and gastrointestinal (GI) blood flow (radioactive microspheres) and delivery, uptake, and extraction of lactate and O2. Hepatic O2 consumption declined proportionately below a critical hepatic O2 delivery (approximately 2 mL O2/min/kg), corresponding to the systemic O2 delivery associated with the onset of systemic lactate accumulation. As hepatic O2 delivery decreased below the critical value, there was initially net hepatic lactate uptake and then a change to net production when the O2 delivery decreased below approximately 1 mL O2/min kg. The GI tract had net lactate production at rest, but surprisingly switched to lactate uptake as cardiac output decreased. The mechanism of lactic acidosis was failure of hepatic lactate uptake to increase despite increased hepatic lactate delivery, as reported in adults subjects. However, in contrast, there was "true" hepatic dysfunction and lactate production only at the lowest levels of cardiac output, after onset of systemic lactate accumulation. Moreover, we speculate that tolerance of young lambs to hypoxia is at least due to two factors: 1) hepatic lactate uptake is maintained beyond the "critical" O2 delivery and fall in hepatic O2 consumption, and 2) there is a switch to lactate uptake by the GI tract serving to buffer the lactate.

Acidosis, Lactic↗
PubMed1980

Changes in cardiac output and its distribution after non-haemorrhagic injury in the rat.

In the unanaesthetized rat cardiac output, measured by a thermodilution technique, fell rapidly following a 4h period of bilateral hind-limb ischaemia. There was a significant positive correlation between body temperature and total cardiac output after injury. There were also striking changes in the distribution of cardiac output; for example, hepatic artery flow was markedly increased, whereas splanchnic flow fell passively with the reduction in cardiac output. There were suggestions of regional differences in the reduction of blood flow within the brain.

Animals↗