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PubMed2005

Assumed oxygen consumption frequently results in large errors in the determination of cardiac output.

OBJECTIVE: We sought to investigate the differences in assumed and measured oxygen consumption values for the determination of cardiac output by using the Fick principle in a pediatric population with congenital heart disease. METHODS: The patient population consisted of 143 patients with a mean age of 11.3 years (age range, 2 days to 23.8 years) undergoing cardiac catheterization during general anesthesia and with mechanical ventilation. Oxygen consumption was measured with a standard commercial analyzing system (Deltatrac II; Datex, Engström, Helsinki, Finland). Assumed oxygen consumption values were calculated according to the formulas of Krovetz and Goldbloom and LaFarge and Miettinen. Comparisons between measurements and assumptions were performed by Bland-Altman plots. Two-sided paired t tests were used to assess a difference of the assumed and measured values. RESULTS: The range of measured oxygen consumption values was between 55.2 and 249 mL . min -1 . m -2 . The Krovetz-Goldbloom formula led to systematically larger values compared with the measured values (P = .0001; mean difference of -53.3 mL . min -1 . m -2 ; 95% confidence interval, -56.7 to -49.8 mL . min -1 . m -2 ). The use of the LaFarge-Miettinen formula tends to overestimate oxygen consumption (P = .0037; mean difference of -15.9 mL . min -1 . m -2 ; 95% confidence interval, -26.5 to -5.4 mL . min -1 . m -2 ). A similarly poor agreement was found when analyzing a subgroup of 25 patients with Fontan-type circulation. CONCLUSION: The use of assumed instead of measured oxygen consumption values introduces large errors in the determination of cardiac output.

Adolescent↗
PubMed1986

Cardiac output by impedance cardiography during head-out water immersion.

This study was undertaken to ascertain the suitability of impedance cardiography for qualifying cardiac output during water immersion where the electrodes were wet. The cardiac output was compared during wet and dry immersion with the head above water by breath holding briefly at 3 lung volumes. For dry immersion, the subjects were protected from contacting water during immersion by enveloping the whole body in a thin plastic bag. For wet immersion, the subject went into the water wearing only trunks. Eleven healthy males served as subjects. Both basal thoracic impedance and the minimum rate of impedance change decreased during wet immersion. These changes were specific, which insignificantly influenced the computation of stroke volume as compared to dry immersion. Our results showed no statistical differences between wet and dry immersions, and between measurements made at total lung capacity functional residual capacity, or residual volume. It is concluded that impedance cardiography is applicable directly in wet conditions without having to protect the subject from getting wet.

Adult↗
PubMed1993

Chronic angiotensin-converting-enzyme inhibition improves cardiac output and fluid balance during heart failure.

The purpose of this study was to examine the sequential changes in renal and cardiovascular function produced by chronic Benazepril administration at different stages of heart failure in dogs. Heart failure was produced by rapid ventricular pacing in five dogs with a normally functioning renin-angiotensin system (angiotensin normal, AN) and six dogs chronically administered the angiotensin-converting-enzyme inhibitor (ACEI) Benazepril. After 7 days of pacing, cardiac output was significantly higher and total peripheral resistance (TPR) lower in the ACEI compared with the AN dogs. Cumulative sodium and water balance increased significantly in both groups, but after 7 days of pacing there were no significant differences between groups. However, the rate of increase in sodium and water balance was significantly less in the ACEI group. Effective renal plasma flow decreased in the AN and ACEI groups during pacing, but there were no between-group differences, and no significant changes in glomerular filtration rate (GFR) occurred in either group. In the AN dogs, pacing was continued for 7-21 days until the onset of decompensated heart failure. Urinary sodium excretion increased on the first day of ACEI infusion during this stage but returned to pre-ACEI levels during the next 2-3 days. No significant improvement in cardiac output was measured during ACEI in decompensated heart failure. These data suggest that chronic ACEI administration can improve renal and cardiac function in early heart failure without impairing GFR but is less chronic ACEI administration can improve renal and cardiac function in early heart failure without impairing GFR but is less effective in later, decompensated stages.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2006

Arterial pressure-based technologies: a new trend in cardiac output monitoring.

New trends in cardiovascular monitoring use the arterial pulse as a less invasive means of assessing cardiac output. When adopting a new technology into practice, three questions need to be answered: (1) is the method technologically sound?, (2) is it based on physiologic principles?, and (3) are the applications clinically important? This article provides a clinical review on the technology, physiology, and applications of a new arterial pressure-based method of determining cardiac output and stroke volume variation as an additional parameter for fluid status assessment.

Algorithms↗
PubMed1993

Dependence of shunt on cardiac output in unilobar oleic acid edema. Distribution of ventilation and perfusion.

OBJECTIVE: In acute respiratory failure, increased cardiac output (Qt) increases shunt (Qs/Qt). We have tested if this is caused by: 1) a redistribution of blood flow towards edematous regions, or 2) a decrease of regional ventilation in the edematous region. DESIGN: Oleic acid edema was induced in the left lower lobe (LLL) of 11 pigs. Qt was varied with bleeding and infusion of blood and dextran. Blood flow to the LLL was measured at low and high Qt with electromagnetic low probes in 6 animals and with a gamma camera in 5. In the gamma camera pigs regional ventilation was also measured. MEASUREMENTS AND RESULTS: Qt was increased by 45% (electromagnetic flow probes) and 73% (gamma camera). Qs/Qt increased from 24.9-31.3% (p < 0.05) and from 17.6-28.8% (p < 0.001) respectively. No change in fractional perfusion of LLL could be seen, neither with flow probes nor with gamma camera. A decrease in ventilation of LLL, 2.6%, was observed when Qt was increased (p < 0.05). CONCLUSION: Theoretically a small decrease in ventilation can explain the increase in shunt, if regions with low ventilation/perfusion (VA/Q) ratio are transformed to shunt. This is, however, unlikely since earlier studies have shown that blood flow is distributed either to regions with normal VA/Q ratio or to shunt regions. We conclude that the cardiac output dependent shunt is not caused by redistribution of blood flow between lobes or by decreased ventilation in the edematous region. We cannot exclude that blood flow is redistributed within the edematous lobe.

Animals↗
PubMed2003

Report of a case series of ultra low-frequency oscillations in cardiac output in critically ill adults with sepsis, systemic inflammatory response syndrome, and multiple organ dysfunction syndrome.

Healthy physiological systems exhibit irregular variability whereas diseased systems display decreased signal variability or greater regularity. The objective of this article is to report a case series of critically ill adults who displayed ultra low-frequency periodic sinusoidal oscillations in cardiac output (ULF-CO) that were discovered during a clinical study testing software for continuous physiological monitoring. Data were collected from 13 critically ill surgical and trauma patients who required continuous cardiac output monitoring. Physiologic data were collected from clinical monitors. The computerized time series of cases displaying CO oscillations were manually reviewed. Ten patients with sepsis or the systemic inflammatory response syndrome exhibited 18 episodes of ultra low-frequency periodic oscillations (ULF-CO) with frequencies ranging from 0.0028 to 0.000053 Hz (periods, 6 to 316 min). Intensive care unit mortality rate was 50%. The amplitude and coefficient of variation of cardiac output during ULF-CO ranged from 0.1-4.6 L and 3.9-14.3%, respectively. Duration of ULF-CO ranged from 4-108.1 h. ULF-CO could not be explained as a result of patterned artifact from measurement error or therapeutic intervention. ULF-CO may be a pathophysiologic marker that might serve the diagnosis, prognosis, and treatment of critical illness.

Adolescent↗
PubMed1992

Reduced cardiac output and exercise capacity in patients after MI.

This article summarizes the literature and suggests directions for future research concerning rehabilitation potential, impairment, and reduced cardiac output after myocardial infarction (MI). Current evidence suggests that cardiac output and maximal exercise capacity are reduced in some post-MI patients. The conceptual model of rehabilitation potential presented emphasizes the need for careful assessment of the state of underlying pathology present after MI when evaluating the response to exercise or exercise training.

Cardiac Output↗
PubMed2001

Recirculatory pharmacokinetics and pharmacodynamics of rocuronium in patients: the influence of cardiac output.

BACKGROUND: Recirculatory models are capable of accurately describing first-pass pharmacokinetics and the influence of cardiac output (CO), which is important for drugs with a fast onset of effect. The influence of CO on pharmacokinetic and pharmacodynamic parameters of rocuronium in patients was evaluated using a recirculatory pharmacokinetic model. METHODS: Fifteen patients were included to study rocuronium pharmacokinetics and pharmacodynamics. Bolus doses of rocuronium (0.35 mg/kg) and indocyanine green (25 mg) were injected simultaneously via a peripheral intravenous catheter. Blood samples were taken for 240 min from the radial artery. The force of contraction of the adductor pollicis after a train-of-four at 2 Hz every 12 s was measured. Arterial concentration-time curves of rocuronium and indocyanine green were analyzed using a recirculatory model. Pharmacodynamics were described using a sigmoid maximum effect (Emax) model. RESULTS: The CO of the patients varied from 2.43 to 5.59 l/min. Total distribution volume of rocuronium was 17.3 +/- 4.8 l (mean +/- SD). The CO showed a correlation with the fast tissue clearance (Cl(T_f); r2 = 0.51), with the slow tissue clearance (Cl(T_s); r2 = 0.31) and with the mean transit times of rocuronium except for the mean transit time of the slow tissue compartment. The blood-effect site equilibration constant (k(e0)) was strongly correlated with CO (r2 = 0.70). CONCLUSIONS: Cardiac output influences the pharmacokinetics, including k(e0), for rocuronium in patients. For drugs with a fast onset of effect, a recirculatory model, which includes CO, can give a good description of the relation between concentration and effect, in contrast to a conventional compartmental pharmacokinetic model.

Adult↗
PubMed1998

Flap flow and cardiac output as functions of pulmonary artery wedge pressure: experimental study in the pig.

Cardiac output (CO) is redistributed during hypovolemia, but it has not been clearly documented how this influences flap perfusion. Simultaneous changes in perfusion of a muscle flap and CO as modulated by reductions in cardiac filling pressure were compared in a pig model. The hypothesis was that flap flow (FF) would remain relatively constant as CO was reduced, according to the Frank-Starling curve. Under general anesthesia, five domestic pigs were utilized. Following right carotid artery cannulation, measurement of systemic blood pressure and blood gas analysis were carried out. An oximetric Swan-Ganz catheter insertion via the right internal jugular vein was used to measure CO, temperature, and pulmonary artery wedge pressure (PAWP). In the lateral decubitus position, a right latissimus dorsi muscle flap was elevated in the animal, using standard technique. The insertion of the muscle was divided, and a 1-cm section of thoracodorsal artery was mobilized to measure flap perfusion with a transonic Doppler flowmeter. After baseline measurements of PAWP, CO, and FF were obtained, blood volume was reduced in 350-cc aliquots at 10-min intervals. After each aliquot was removed, the hemodynamic parameters were again recorded. This procedure was repeated until the CO was less than 1.0 liter/min; at this point the pig was sacrificed. The mean baseline PAWP was 15.6+/-4.0 mmHg, which was reduced to 2.2+/-1.1 mmHg (p<0.05) by the end of the experiment. The mean baseline FF was 5.6+/-1.9 cc/sec, and the mean baseline CO was 4.6+/-1.0 l/min; these were reduced to 0.4+/-0.4 cc/sec (p< 0.05) and 1.1+/-0.1 l/min (p<0.05), respectively, by the end of the experiment. FF and CO were plotted as a function of PAWP and the two regression curves were evaluated by analysis of covariance. The slope of these curves was not different, p=0.4. The hypothesis that FF would be preserved in the face of reductions in CO did not prove to be correct in this experiment. Changes in FF paralleled changes in CO as the PAWP was reduced. Inhalation anesthesia and local sympathectomy may influence flap perfusion during hypovolemia. These results underscore the importance of avoiding hypovolemia during flap surgery, in order to maintain flap perfusion.

Anesthetics, Inhalation↗
PubMed1976

Influence of alpha-adrenergic block and beta-adrenergic stimulation on distribution of cardiac output after cardiopulmonary bypass.

Organ and tissue damage restricts total cardiopulmonary bypass to a few hours in patients. The cause might be the disturbance of tissue flow in which the sympatho-adrenal hyper-activity plays a decisive role. In dogs, killed 30 min after cardiopulmonary bypass was stopped, we studied the tissue distribution of cardiac output with the method of Sapirstein. In one group the alpha-adrenergic blocker, in the other one the beta-adrenergic stimulator was continuously applied during the whole operation-period. Compared to a control group the per cent of cardiac output as well as the regional tissue flow after alpha-adrenergic block increased in the liver, ileum, adrenals, testes, kidney and in the skin and decreased in the spleen and thyroid gland. After beta-adrenergic stimulation the per cent of cardiac output increased in the heart muscle, lungs, liver, ileum, adrenals and m. soleus and decreased in the spleen and thyroid gland. The absolute values of organ tissue flow increased in ileum and decreased in the spleen, thyroid gland and in the kidney.

Adrenergic alpha-Antagonists↗
PubMed1995

Treatment of perioperative low cardiac output syndrome.

New approaches to the treatment of perioperative low cardiac output are considered. In particular, use of the phosphodiesterase III inhibitors and their cardiovascular actions are reviewed and contrasted with those of conventional inotropic agents. The increasing recognition of right-sided dysfunction is highlighted, and appropriate therapeutic strategies are considered. The increasing role of pulmonary-specific vasodilators such as inhaled nitric oxide is emphasized. Strategies to preserve right heart perfusion while producing pulmonary vasodilatation are discussed.

Cardiac Output, Low↗
PubMed1999

Metabolic regulation of cardiac output during inhalation anaesthesia in dogs.

BACKGROUND: The metabolic regulation of tissue blood flow manifests itself in a linear relation between blood flow and oxygen consumption, the latter being the independent variable. It is unknown, however, if this fundamental physiological principle operates also during inhalation anaesthesia known to be associated with decreases in both cardiac output (Q) and oxygen consumption (VO2). METHODS: Seven dogs (23-32 kg) with chronically implanted flow probes around the pulmonary artery were repeatedly anaesthetized with halothane, enflurane, isoflurane, sevoflurane, and desflurane at increasing minimum alveolar concentrations (1-3 MAC). Cardiac output (ultrasound transit-time flowmeter) and VO2 (indirect calorimetry) were measured continuously. We also imposed selective changes in Q, and thus of O2 supply, to see if and to what extent this would alter VO2 during anaesthesia (1.5 MAC). RESULTS: In awake dogs under basal metabolic conditions, VO2 was 4.6 +/- 0.1 ml.kg-1.min-1 and Q 105 +/- 3 ml.kg-1.min-1 (mean +/- SEM). During inhalation anaesthesia, VO2 and Q decreased by approximately 30% and 60%, respectively. The concentration-effect relations of both variables did not differ between anaesthetics, yielding a uniform Q/VO2 relation, which was nearly linear in the range (0-2 MAC) with an average slope of 39 +/- 1 (range 30-55). Above 2 MAC, Q decreased more for a given change in VO2, and O2 extraction increased by 50%, indicating compromised oxygen delivery (DO2). Imposed changes in Q, both in awake and anaesthetized dogs, yielded Q/VO2 relations which were notably steeper (slopes 114 to 187) than those observed during inhalation anaesthesia. More important, imposed increases in Q and thus DO2 during anaesthesia (1.5 MAC) to rates comparable to that in the awake state produced a much less than proportional increase in VO2 without restoring it to baseline. CONCLUSIONS: Inhalation anaesthesia is characterized by a uniform Q/VO2 relation with an almost linear course at an anaesthetic concentration up to 2 MAC, regardless of the anaesthetic. Metabolic regulation of blood flow apparently operates also during inhalation anaesthesia up to 2 MAC so that the decrease in VO2 determines Q. This implies that cardiac output alone provides little information on the function of the circulation during inhalation anaesthesia unless related to metabolic demands, i.e. to VO2.

Anesthesia, Inhalation↗
PubMed1990

Cardiac output responses of primigravid women during exercise determined by the direct Fick technique.

We compared metabolic and cardiovascular responses to aerobic exercise with the direct Fick technique in women during and after pregnancy. Seven subjects were studied at 37 weeks' gestation and again 12 weeks postpartum. All were tested at rest and during four sequential exercise bouts consisting of 5 minutes at each of two cycle (50 and 75 W) and two treadmill (67 m x min-1 at 2.5 and 12% grade) protocols. Oxygen consumption (VO2) and heart rate were measured during the fifth minute of exercise. Arterial and mixed venous oxygen contents, obtained from catheters placed in the radial and pulmonary arteries, respectively, were used to calculate arterial-venous oxygen difference. Cardiac output and stroke volume were calculated from the Fick equation. Responses of VO2, cardiac output, and stroke volume were greater when exercise was performed at 37 weeks' gestation as compared with postpartum. In contrast, heart rate response (during cycling) and arterial-venous oxygen difference (during treadmill walking) were less when exercise was performed during pregnancy. Our results indicate that there is no compromise in maternal cardiac output during either cycle or treadmill exercise performed late in pregnancy as compared with postpartum conditions.

Adult↗
PubMed1988

[Measurement of cardiac output in waking rats using a Doppler ultrasonic technic].

The ultrasound Doppler technique was used for the determination of cardiac output in conscious Wistar rats. The cuff probes were placed on the ascending aorta and calibrated with the radioactive microsphere technique. The results of experiments show that Doppler ultrasound technique determines the cardiac output with high linearity. The possibility of using both methods in one and the same animal was also confirmed.

Animals↗
PubMed1993

Amplitude of the ocular pneumoplethysmography waveform is correlated with cardiac output.

BACKGROUND AND PURPOSE: Ocular pulse amplitude, the amplitude of the ocular pneumoplethysmographic waveform, is altered in several ophthalmologic diseases that disturb ocular blood flow, implying that ocular pulse amplitude may provide an estimate of ocular blood flow. Because ocular blood flow currently cannot be quantified in humans, two experiments were undertaken to evaluate the association of ocular pulse amplitude with total body blood flow. METHODS: In experiment 1, cardiac output was determined by cardiac catheterization in 181 patients who underwent OPG-Gee testing during the same hospitalization. In experiment 2, 110 instances of atrial arrhythmia captured on ocular pneumoplethysmographic tracings were evaluated for transient changes in heart rate (R-R ratio) associated with transient changes in ocular pulse amplitude (ocular pulse amplitude ratio). RESULTS: In experiment 1, average ocular pulse amplitude in the two eyes (OPAAV) was significantly correlated with cardiac output/heart rate (r = 0.53; p < 0.0001) and cardiac index/heart rate (r = 0.43; p < 0.0001). In experiment 2, R-R ratio was significantly correlated with ocular pulse amplitude ratio (r = 0.85; p < 0.001). CONCLUSIONS: These results show that ocular pulse amplitude, a physiological measurement obtained from the globe, is correlated with cardiac output. They imply that ocular pulse amplitude may provide a clinically useful estimate of at least the pulsatile component of ocular blood flow.

Aged↗
PubMed2004

A new non-invasive continuous cardiac output trend solely utilizing routine cardiovascular monitors.

OBJECTIVE: Three of the us developed a new non-invasive continuous cardiac output (CCO) measurement method utilizing routine clinical monitors based on the pulse-contour analysis combined with pulse wave transit time (PWTT). Using pulmonary artery catheter (CCOpa), we compared this estimated CCO (esCO) with the thermodilution CCO early after cardiac surgery, and tested whether the esCO method has potential of being an alternative measure of CCO. METHODS: Thirty-six patients without continued arrhythmias were studied. esCO was computed using electrocardiogram (ECG) monitor, arterial pressure monitor and pulse-oximetry system. Both sets of data (esCO and CCOpa), by averaging the results of the preceding 10 min, were compared at 30-min intervals throughout the 15.8 +/- 3.3 h (S.D.) of study. Bland-Altman plots and correlation analysis were used for statistical comparison. RESULTS: A total of 981 paired sets of data (89.9%) among 1093 measurements were compared in the absence of displacement of either pulse-oximetry or ECG probes and/or inaccurate detection of R wave. The difference between esCO and CCOpa results was -0.06 +/- 0.82 L/min (S.D.), and there was a linear correlation between them (r = 0.80, p < 0.0001). The difference between them was 0.00 +/- 0.48 L/min at the first 1 h, which remained unchanged throughout 20 h after the start of measurement. CONCLUSIONS: The results demonstrate that esCO has a close correlation with the CCOpa, even though the two methods are not interchangeable. The results suggest that esCO method has potential of being an alternative non-invasive cardiac output trend, unless there are apparent arrhythmias.

Adult↗
PubMed1974

Effects of dobutamine on left ventricular performance, coronary dynamics, and distribution of cardiac output in conscious dogs.

The effects of dobutamine ([+/-]-4-[2-[[3-(p-hydroxyphenyl)-1-methyl propyl] amino] ethyl] pyrocatechol hydrochloride), a new synthetic cardioactive sympathomimetic amine, were examined on direct and continuous measurements of left ventricular (LV) diameter (D), pressures (P), velocity of shortening (V), dP/dt, dP/dt/P, arterial pressure, cardiac output, and regional blood flows in the left circumflex coronary, mesenteric, renal, and iliac beds in healthy, conscious dogs. At the highest dose of dobutamine examined, 40 mug/kg/min, the drug increased dP/dt/P from 65+/-3 to 128+/-4 s(-1) and isolength velocity from 72+/-4 to 120+/-7 mm/s without affecting LV end diastolic D significantly. Mean arterial P rose from 92+/-2 to 104+/-3 mm Hg and heart rate from 78+/-3 to 111+/-7 beats/min, while LV end systolic D fell from 24.1+/-1.4 to 19.9+/-1.8 mm, reflecting a rise in stroke volume from 30+/-4 to 42+/-3 ml. Cardiac output rose from 2.41+/-0.23 to 4.35+/-0.28 liter/min, while calculated total peripheral resistance declined from 0.042+/-0.005 to 0.028+/-0.003 mm Hg/ml/min. The greatest increases in flow and decreases in calculated resistance occurred in the iliac and coronary beds, and the least occurred in the renal bed. Propranolol blocked the inotropic and beta(2) dilator responses while vasoconstricting effects mediated by alpha adrenergic stimulation remained in each of the beds studied. When dobutamine was infused after a combination of practolol and phentolamine, dilatation occurred in each of the beds studied. These observations indicate that dobutamine is a potent positive inotropic agent with relatively slight effects on preload, afterload, or heart rate, and thus may be a potentially useful clinical agent. The one property of this drug which is not ideal is its tendency to cause a redistribution of cardiac output favoring the muscular beds at the expense of the kidney and visceral beds.

Animals↗
PubMed1980

Induced fetal hyperthyroidism: cardiac output and oxygen consumption.

In 13 chronically catheterized fetal lambs, we inserted a subcutaneous osmotic minipump that released triiodothyronine (T3) at a rate of 5.9 microgram x h-1. Five days postoperatively, fetal plasma T3 concentration had increased 10-fold from a control value of 18.4 ng x dl-1; reverse T3 and thyroxine had decreased 83 and 61% from control values of 524 ng x dl-1, and 9.5 microgram x dl-1, respectively. Fetal heart rate increased 29% to 210 from 163 beats x min-1, and blood pressure remained constant. Cardiac output measured with radioactive-labeled microspheres increased 22% to 678 +/- 33 from a control value obtained from another group of animals of 554 +/- 16 ml x min-1 x kg-1. Umbilical blood flow also increased 22%, while coronary flow increased 35%, and pulmonary flow increased 90%. In contrast, flow to the thyroid gland decreased 52%. Fetal oxygen consumption increased 28% to 10.5 +/- 0.5 from 8.2 +/- 1.1 ml x min-1 x kg-1. Placental carbon monoxide diffusing capacity and venous and arterial blood gas values remained unchanged. We conclude that 1) sustained fetal T3 infusion is one of the few factors that can increase fetal cardiac output, and may play a role in increasing cardiac output in the newborn infant, 2) T3 infusion results in an increased rate of metabolism with increased oxygen consumption, and 3) placental reserve for oxygen diffusion exceeds normal oxygen requirements.

Animals↗