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PubMed1984

The effects of variations in PaCO2 on brain blood flow and cardiac output in the newborn piglet.

The acute effects of normoxemic hypocarbia and hypercarbia were examined in six newborn piglets. Brain blood flow was maintained during hypocarbia until extremely low PaCO2 (less than 15 mm Hg) levels were achieved at which time total brain and cerebral blood flow decreased significantly from baseline values. Blood flow to the thalamus, cerebellum and brain stem was unchanged from baseline conditions during hypocarbia. This suggests that the newborn brain is relatively insensitive to moderate degrees of hypocarbia. Extreme hypocarbia (PaCO2 less than 15 mm Hg) was associated with a significant increase in heart rate, accompanied by a significant decrease in mean arterial blood pressure; however, cardiac output was not significantly different from baseline determinations. Hypercarbia with normoxemia was associated with significant increases in total brain blood flow, with greater blood flow to the brain stem, cerebellum, and thalamus than to the cerebrum. The percentage of cardiac output received by the brain was also significantly increased, although total cardiac output was unchanged. This demonstrates that the newborn cerebral vasculature is sensitive to hypercarbia and that regional differences in sensitivity may account for the greater increments in blood flow to the caudal portions of the brain than that to the cerebrum.

Animals↗
PubMed1975

Clinical applications of thermodilution cardiac output determinations.

The pulmonary arterial catheter was shown to be safe and easily positioned in a group of 200 patients. Thermodilution cardiac output measurement was shown to be simple, rapid, and safe. The technic was as accurate as the simultaneously measured indocyanine green cardiac output, and more reproducible, particularly at high and low flows. The construction of myocardial performance curves during a fluid challenge is described. The value of these curves is guiding fluid, drug, and respirator therapy is illustrated by case presentations.

Aged↗
PubMed1992

Prostaglandin I2 versus prostaglandin E2 in dogs with and without low cardiac output. Differential effects on renal function.

Exogenous prostaglandin (PG) administration has been proposed as a vasodilator therapy for heart failure patients. The effects of this therapy on renal function have not been well studied in this disorder. Therefore, we investigated the renal effects of the PGI2 analog iloprost in comparison to PGE2 in 12 conscious dogs before and after induction of a low cardiac output state by rapid right ventricular pacing (250 beats/min for 10 days). In healthy dogs, 5 to 150 ng/kg/min iloprost increased renal plasma flow without affecting glomerular filtration rate and decreased urine flow without affecting natriuresis. PGE2 at the same dosages increased renal plasma flow and urinary sodium excretion without changing the glomerular filtration rate or amount of diuresis. In dogs with low cardiac output and lower basal renal plasma flow, iloprost did not change renal plasma flow, but decreased glomerular filtration rate and filtration fraction. In these animals, PGE2 insignificantly increased renal plasma flow, but significantly augmented urine flow and sodium excretion. We therefore conclude that in an experimental low cardiac output state, PGI2 may cause a deterioration of renal function. In contrast, PGE2 induces natriuresis and diuresis despite an attenuated increase in renal plasma flow. Thus, PGE2 promises to exert a more favorable profile of renal effects in heart failure therapy.

Animals↗
PubMed1992

Influence of body position and pre-exercise activity on cardiac output and oxygen uptake following step changes in exercise intensity.

Parallel measurements of breath-by-breath oxygen uptake, cardiac output (Doppler technique), blood pressure (Finapres technique) and heart rate were performed in nine subjects during cycle ergometer exercise in the upright and supine positions. Transients were monitored during power steps starting from and leading to either rest or lower levels of exercise intensity. Oxygen uptake (VO2) and cardiac output kinetics were markedly faster than in all other conditions when exercise was started from rest. In contrast to exercise-exercise on steps, the computed arteriovenous difference in O2 content increased almost immediately in this situation, indicating that not only the additional energy expenditure due to the acceleration of the flywheel but also an increased venous admixture from non-exercising parts of the body contributed to the early kinetics. The off kinetics generally showed a more uniform pattern and did not simply mirror the on transients. The present findings indicate that transitions from rest should be avoided when muscle VO2 kinetics are to be assessed on the basis of VO2 measurements at the mouth.

Adult↗
PubMed1987

Do oxygen consumption and carbon dioxide production affect cardiac output after cardiopulmonary bypass?

This study examines the oxygen consumption (VO2) and carbon dioxide production (VCO2) occurring before, during, and after cardiopulmonary bypass (CPB) and whether they correlate with changes in cardiac output. Twenty-three patients undergoing open heart surgery were studied. Group 1 (N = 11) received fentanyl citrate, 50 micrograms/kg, intravenously during the induction of anesthesia. Group 2 (N = 12) received 100 micrograms/kg of fentanyl citrate intravenously. We measured VO2, VCO2, as well as hemodynamic and biochemical factors. Initial statistical analyses failed to show any differences in the VO2, VCO2, hemodynamic, or biochemical factors between groups 1 and 2. Therefore, the data from both groups were combined. In comparing the average (for all data) of the post-CPB with the pre-CPB periods in both groups for the metabolic factors, there were 9.0%, 11.5%, and 2.4% increases in the VO2, VCO2, and respiratory quotient, respectively. There was an 80% increase in total serum lactate levels seen in the post-CPB periods when compared with the pre-CPB periods. Serum triglyceride and free fatty acid levels measured in the post-CPB period decreased 39% and 25%, respectively, when compared with the pre-CPB periods. Although there were no changes in the cardiac outputs following CPB, the post-CPB periods showed a 37% increase in central venous pressure when compared with the pre-CPB periods. These data suggest that although there are significant metabolic and biochemical sequelae to CPB, the modest increases in post-CPB VO2, and VCO2 did not affect cardiac output following cardiovascular surgery. Increasing doses of narcotic do not have an effect on those relationships.

Blood Gas Analysis↗
PubMed1984

A new indirect method for measuring arteriovenous O2 content difference and cardiac output from O2 and CO2 concentrations by rebreathing air.

A new indirect method for measuring the arteriovenous O2 content difference (avDO2) was developed. The avDO2 was calculated by dividing the gradient of the CO2 dissociation curve by that of a gas exchange ratio against PCO2. The latter slope was obtained from O2 and CO2 concentrations in rebreathing air. The validity of the method was tested preliminarily in human subjects by comparing the cardiac output calculated from avDO2 and O2 uptake (VO2) with that measured hitherto by other authors, and then in dogs by comparing the calculated avDO2 with the measured value. In the dog experiments, the rebreathing was performed 7 times in each of 7 dogs. Immediately after the rebreathing arterial and mixed venous blood were sampled and analyzed for avDO2. For each rebreathing period the avDO2 was calculated by using the CO2 dissociation curve obtained in the individual dogs. The correlation coefficient between the measured and calculated avDO2 was 0.87, demonstrating reasonable validity of the method. The VO2 was further measured from the time interval during which a known amount of pure O2 was consumed. Then, the cardiac output was calculated by dividing the VO2 by the measured and calculated avDO2. The correlation coefficient between the respective cardiac output values was 0.88, indicating the reliability of using the calculated avDO2.

Animals↗
PubMed1981

Artificial ventilation with PEEP; the influence on cardiac output in the simulated normo-, hypo- and hypervolemic state.

Observations of the influence of artificial ventilation with PEEP on cardiac output are unequivocal. Not only the measure of the end-expiratory pressure and lung compliance play a role, but also the circulating blood volume. In healthy laboratory animals a state of normo-, hypo- and hypervolemia was simulated by changes in position in neurolept-anesthesia. In all cases artificial ventilation with PEEP induced a decrease of cardiac output as a consequence of a decrease of stroke volume. These results are discussed. The conclusion is drawn that a change in stroke volume during artificial ventilation with PEEP is not only dependent on the level of end-expiratory pressure and pulmonary compliance but also on that portion of the Starling curve where the heart at that instant is functioning.

Animals↗
PubMed1999

Successful transcutaneous arterial embolization of a giant hemangioma associated with high-output cardiac failure and Kasabach-Merritt syndrome in a neonate: a case report.

We describe the case of a patient with a neonatal giant cutaneous hemangioma with high-output cardiac failure and Kasabach-Merritt syndrome and successfully treated with transcutaneous arterial embolization aimed at controlling severe congestive heart failure and consumption coagulopathy. A patient was admitted to the neonatal care unit on the first day of age because of a large hemangioma on his right lateral chest wall and respiratory distress, associated with cardiac failure resulting from arteriovenous shunting. On the second day of age the platelet count decreased to 5.7 x 10(4)/microliter and fibrinogen level was 85 mg/dl. The values of prothrombin time and activated partial thromboplastin time were prolonged. Intravenous predonisone therapy was started immediately, but bleeding tendency was getting worse and the evidence of congestive heart failure persisted. On the third day the patient then underwent embolization of feeding arteries with microcoils. The cardiac failure and thrombocytopenic coagulopathy had improved significantly without complications. We conclude that transcutaneous arterial embolization is an effective and safe treatment in this neonate and should be considered for the treatment of control high-output cardiac failure and coagulopathy in infants with hemangioma and Kasabach-Merritt syndrome.

Cardiac Output, High↗
PubMed1987

Cardiac output in a fetus with erythroblastosis fetalis: assessment using pulsed Doppler.

Pulsed Doppler studies of left and right ventricular outputs were obtained over time in a hydropic fetus with erythroblastosis fetalis. Despite severe anemia, cardiac outputs were within the normal range and remained normal after in utero percutaneous intravascular transfusions, which reversed the hydrops. The measurement of cardiac output in utero provides direct evidence that high-output failure due to anemia is not the mechanism for hydrops in erythroblastosis fetalis.

Adult↗
PubMed1976

Estimation of cardiac output in the horse by thermodilution techniques.

An evaluation and comparison of thermodilution technique with dye dilution technique was made in the computation of cardiac output in 39 conscious adult horses (av body wt, 450 kg). Estimation of cardiac output by thermodilution was found to compare favorably with values obtained from dye dilution when a volume of 30 to 40 ml at a temperature of 0 C was used. Difficulties in obtaining accurate thermodilution curves in the horse seem predominantly associated with errors in mixing and observation.

Animals↗
PubMed1994

Chemically modified heparin improves hepatocellular function, cardiac output, and microcirculation after trauma-hemorrhage and resuscitation.

BACKGROUND: Although heparinization before hemorrhagic shock improves tissue perfusion and organ function, the anticoagulant properties of conventional heparin preclude its clinical use. The purpose of this study was to determine whether chemically modified heparin (CMH), which does not have any significant anticoagulant activity, produces any beneficial effects on hepatocellular and cardiovascular function and microcirculation after trauma-hemorrhage and resuscitation. METHODS: After induction of tissue trauma (that is, laparotomy), rats were bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of maximum bleedout volume was returned in the form of Ringer's lactate (RL). The animals were then resuscitated with three times the volume of shed blood with RL over 45 minutes, followed by two times RL and CMH (7 mg/kg body wt; approximately 10% of the anticoagulant activity of conventional heparin), conventional heparin (7 mg/kg), or normal saline solution over 60 minutes. Hepatocellular function, cardiac output, and microvascular blood flow were determined thereafter. RESULTS: The results indicate that hepatocellular function, cardiac output, and microvascular blood flow in the liver, kidney, spleen, and small intestine decreased markedly after trauma-hemorrhage and resuscitation. Infusion of CMH or conventional heparin during resuscitation, however, restored or significantly improved the mentioned parameters. CONCLUSIONS: Because CMH does not have any significant anticoagulant properties and because it restores or significantly improves hepatocellular function, cardiac output, and tissue perfusion, this agent appears to be a useful adjunct in the treatment of trauma and hemorrhagic shock, even in the absence of blood resuscitation.

Animals↗
PubMed2004

[A comparison of two methods for continuous cardiac output measurement: PulseCO VS CCO].

BACKGROUND: PulseCO (PulseCO) (PulseCO Hemodynamic Monitor, LiDCO Co., London, England) is a low invasive apparatus to measure cardiac output continuously from arterial pulse waveform. CCO (774 HF 75, Edwards Lifescience Co., California, USA) is a continuous cardiac monitor commonly used clinically. The purpose of this study is to compare the accuracy of these two methods for cardiac output measurement with the thermodilution technique (TDCO) as control. METHODS: To compare the accuracy of PulseCO with that of CCO, six patients with pulmonary-artery catheter inserted were recruited. PulseCO and CCO were measured continuously, and these CO values were compared with TDCO measurements every hour. RESULTS: Correlation with TDCO was examined in PulseCO (r=0.82) and CCO (r=0.80). CONCLUSIONS: PulseCO was low invasive, and showed a significantly better correlation with TDCO, compared with CCO.

Calibration↗
PubMed1995

Oxygen tension in the bladder epithelium rises in both high and low cardiac output endotoxemic sepsis.

The effect of endotoxin on tissue oxygen tension measured at the bladder epithelium was assessed in spontaneously breathing Sprague-Dawley rats anesthetized with halothane. Hyperdynamic (high cardiac output, group A, n = 6) and hypodynamic (low cardiac output, group B, n = 6) circulatory responses were achieved by intravenous administration of Escherichia coli lipopolysaccharide, 10 mg/kg over 30 min or 20 mg/kg over 1 min, respectively. Comparison was made against sham-operated control rats (group C, n = 6). Aortic and renal blood flows increased in group A and fell in group B (P < 0.001). However, in both groups, bladder epithelial oxygen tension rose significantly compared with control (P < 0.01), despite an increasing metabolic acidosis. This is in contradistinction to previous studies of nonseptic insults where bladder epithelial oxygen tension fell in line with an increasing arterial base deficit. If a raised tissue oxygen tension could be demonstrated in other organ beds, this would suggest that decreased utilization of oxygen rather than reduced tissue oxygen availability is responsible for the apparent anaerobic respiration seen in sepsis.

Animals↗
PubMed1996

Effects of continuous positive airway pressure on cardiac output and plasma norepinephrine in sedated pigs.

Continuous positive airway pressure (CPAP) increases cardiac output (CO) in congestive heart failure (CHF). In six sedated pigs that were normovolemic (NV) and hypervolemic (HV), and seven previously instrumented pigs with pacing-induced CHF, we tested the hypothesis that this is associated with decreased total body sympathetic nerve activity (SNA). Hemodynamic variables and plasma norepinephrine level measurements were measured at baseline, CPAP 5 and 10 cm H2O, and recovery. Arterial O2 saturation was maintained at greater than or equal to 90% and PCO2 did not change. For NV baseline plasma norepinephrine level (PNE) was 97 +/- 61 pg/mL, CO 2.4 +/- .5 L/min, and pulmonary wedge pressure (Pw) 10.1 +/- 2.4 mmHg and did not change with CPAP. HV and CHF were associated with increased baseline Pw (18-21 mmHg). Baseline CO was increased with HV and unchanged with CHF. Baseline PNE was increased 4 to 5-fold with both HV and CHF. CO increased at CPAP 5 compared with baseline with both HV and CHF. However, PNE decreased with CPAP in HV, and increased with CPAP in CHF. Increased CO was always associated with decreased systemic vascular resistance. We conclude the following: (1) increased CO with CPAP can be associated with either increasing or decreasing SNA; (2) CPAP can produce increases in CO when the heart is distended whether baseline LV function is relatively normal (HV) or depressed (CHF); and (3) there are probably a number of different mechanism increasing CO with CPAP and these may vary from condition to condition.

Animals↗
PubMed1970

Mixed venous oxygen saturation in relation to cardiac output in myocardial infarction.

Mixed venous oxygen saturations derived from measurement of mixed venous oxygen tension were compared with dye dilution cardiac output determinations in 26 patients with acute myocardial infarction. Mixed venous oxygen saturation was greatly reduced in patients with shock or failure complicating myocardial infarction. The level of oxygen saturation correlated with cardiac output determinations. The measurement of mixed venous oxygen saturation, which is relatively simple and does not require elaborate equipment, should be an important aid to the rational treatment of patients with low output states complicating acute myocardial infarction.

Acute Disease↗
PubMed1979

Organ blood flow, cardiac output, arterial blood pressure, and vascular resistance in rats exposed to various oxygen pressures.

Blood flow in different organs, cardiac output, and arterial blood pressure were measured in unanesthetized rats under 1, 2, 3.5, 5, and 7 ATA O2, during first electrical discharge developed at 7 ATA O2 and following decompression. Brain, spinal cord, and hypophysis blood flow were reduced after 10 min of exposure to 2, 3.5, and 5 ATA O2 and were normal before and during first electrical discharge. Liver and muscle blood flow were significantly reduced under all investigated pressures, while myocardium, lung, kidney, and adrenal blood flow remained unchanged except for a significant increase in myocardium and lung blood flow under 1 ATA O2. Cardiac output was significantly decreased while arterial blood pressure was significantly decreased under all investigated pressures. The total peripheral resistance increased 36 to 81% at various oxygen pressures. These results are discussed in relation to the possible involvement of hemodynamic changes in awake animals, in the development of the adverse effects of HOP.

Adrenal Glands↗
PubMed1987

Atrial natriuretic peptide decreases cardiac output independent of coronary vasoconstriction.

Studies were performed in isolated, Langendorff-perfused rat hearts and anesthetized dogs to determine the effects of synthetic atrial natriuretic peptide (ANP 8-33) on the coronary circulation. In vitro studies in the rat examined coronary flow dynamics to ANP 8-33 over a defined range from physiologic to pharmacologic concentrations. No changes in coronary flow or chronotropic and inotropic function of the isolated Langendorff-perfused heart were observed in response to increasing concentrations of ANP 8-33 (10(2) to 10(6) pg/ml). In the dog, a low, nonhypotensive dose of ANP 8-33 (0.05 microgram/kg/min) decreased cardiac output with no change in coronary blood flow or coronary vascular resistance. At a high, hypotensive dose (0.3 microgram/kg/min) ANP 8-33 decreased cardiac output in association with transient coronary vasodilation. Continued infusion resulted in a decrease in coronary blood flow and arterial pressure with no change in coronary vascular resistance. Thus, in vitro physiologic and pharmacologic concentrations of ANP, or in vivo low concentrations of ANP, do not result in an alteration in coronary flow. In vivo ANP 8-33, at both nonhypotensive and hypotensive concentrations, decreased cardiac output in the absence of coronary vasoconstriction.

Animals↗
PubMed1990

Effective pulmonary flow, aortic flow and cardiac output: in vitro and in vivo comparisons in the dog.

This paper presents data on the measurement of aortic flow (Qa) using an electromagnetic flowmeter and the measurement of pulmonary blood flow (Qep) using a single-breath technique employing freon-22 as the soluble marker gas. The purpose was to assess the potential of a single-breath technique (using freon) as an effective way to estimate cardiac output (Q) non-invasively. The electromagnetic flowmeter was calibrated in vitro in an isolated heart-aorta preparation by collection of the ejected blood volume, thereby giving an absolute calibration of the Qa measurement. Using anaesthetized beagles Qa was measured immediately preceding (Qa,mean) and during (Qa,inst) measurement of Qep. These measurements were made before and after I.V. bolus doses of nifedipine used to increase cardiac output so as to measure a range of flows. The Qa was disturbed by the respiratory manoeuvre imposed as part of the single-breath technique, rising, falling and rising again as the lung volume was reduced, increasing with the test gas and reducing again, typically giving Qep = 1.39 +/- 0.13 l min-1, Qa,mean = 1.35 +/- 0.15 l min-1 and Qa,inst = 1.33 +/- 0.17 l min-1 (+/- S.D., n = 7 in each case). The standard deviations include interanimal variation as well as technique errors. Regression analysis of Qep on Qa,mean gave the highest correlation (r = 0.75) and the lowest coefficient of variation (11.7%), the values being 0.69 and 14.0% respectively for Qep on Qa,inst. These compare favourably with equivalent values for alternative methods reported in the literature, the strict calibration giving confidence that the single-breath technique provides data closely related to the aortic flow found prior to the respiratory manoeuvre, i.e. the undisturbed cardiac output.

Animals↗