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PubMed1984

Effects of verapamil on thermal trauma depressed cardiac output in the anaesthetized dog.

Thermal trauma to the anaesthetized dog results in an immediate, significant decrease in cardiac output, an increase in peripheral resistance and no significant change in mean arterial blood pressure. The administration of verapamil 1.0 mg/kg by slow intravenous injection produced a rapid increase in cardiac output and a decrease in peripheral resistance. Mean arterial pressure fell and returned to or nearly to pre-injection values within 30 min. The duration of the increase in cardiac output after a single dose of verapamil was approximately 1.5-2.0 h. Administration of a second 0.5 mg/kg dose of verapamil, 1.5 h after the first dose, increased cardiac output and decreased peripheral resistance. After the second dose of verapamil, cardiac output was significantly greater and peripheral resistance was significantly less than in untreated animals for at least 2 h.

Animals↗

PubMed1985

Laser Doppler velocimetry as a monitor of cardiac output changes in dogs.

Cutaneous blood flow may be measured utilizing a continuous, noninvasive technique, laser Doppler velocimetry (LDV). Monitoring of cutaneous blood flow by LDV might be a useful method to monitor cardiac output. To test this hypothesis, sequential measurements of cardiac output, LDV, and transcutaneous oxygen (PtcO2) were made on 10 anesthetized dogs during experimental shock. There was significant correlation between LDV and cardiac output, while PtcO2 reflected cardiac output only at low flow states. These results show that, in the animal model, cutaneous LDV is a sensitive and specific method for monitoring cardiac output changes.

Animals↗

PubMed1997

Heart rate and stroke volume contribution to cardiac output in swimming yellowfin tuna: response to exercise and temperature.

Cardiac performance in the yellowfin tuna (Thunnus albacares, 673-2470 g, 33-53 cm fork length, FL) was examined in unanesthetized fish swimming in a large water tunnel. Yellowfin tuna were fitted with either electrocardiogram electrodes or a transcutaneous Doppler blood-flow probe over the ventral aorta and exposed to changes in swimming velocity (range 0.8-2.9 FLs-1) or to an acute change in temperature (18-28 degrees C). Heart rates (fH) at +/-1 degree C (30-130 beats min-1) were lower on average than previous measurements with non-swimming (restrained) tunas and comparable with those for other active teleosts at similar relative swimming velocities. Although highly variable among individuals, fH increased with velocity (U, in FLs-1) in all fish (fH = 17.93U + 49.93, r2 = 0.14, P < 0.0001). Heart rate was rapidly and strongly affected by temperature (Q10 = 2.37). Blood flow measurements revealed a mean increase in relative cardiac output of 13.6 +/- 3.0% with exercise (mean velocities 1.23-2.10 FLs-1) caused by an 18.8 +/- 5.4% increase in fH and a 3.9 +/- 2.3% decrease in stroke volume. These results indicate that, unlike most other fishes, cardiac output in yellowfin tuna is regulated primarily through increases in fH. Acute reductions in ambient temperature at slow swimming velocities resulted in decreases in cardiac output (Q10 = 1.52) and fH (Q10 = 2.16), but increases in stroke volume (Q10 = 0.78). This observation suggests that the lack of an increase in stroke volume during exercise is not due to the tuna heart operating at maximal anatomical limits.

Animals↗

PubMed1988

Regulation of cardiac output with controlled heart rate in newborn lambs.

To determine the factors regulating cardiac output in newborn lambs and to examine the effects of age after birth, we altered heart rate, afterload, preload, and myocardial contractility in eight younger lambs, 5 to 13 days old, and seven older lambs, 15 to 36 days old. To control heart rate, we ablated the atrioventricular node by injecting formalin into the region of the node, and paced the right ventricle at a baseline heart rate of 200 beats/min. After the lambs recovered from surgery, we performed two protocols. In the first protocol we assessed the effects of changing heart rate by pacing the ventricle at various rates. We also examined the effect of altering afterload and preload at a fixed heart rate: afterload was increased by infusing phenylephrine and decreased by infusing nitroprusside. Preload was increased by infusing blood or 0.9% NaCl solution over 2 min. In the second protocol, we increased myocardial contractility by infusing isoproterenol at a fixed heart rate. Increasing heart rate above baseline levels caused no significant increase in cardiac output in the younger lambs (3.9 +/- 4.0%, mean +/- SD), and only small increases in the older lambs (11.4 +/- 6.7%). Decreasing heart rate, however, resulted in a progressive decrease in cardiac output in both groups of lambs. Decreasing afterload caused no significant increase in cardiac output in the younger lambs (1.4 +/- 14.0%) and only a small increase in the older lambs (11.1 +/- 1.9%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

The effect of cardiac output on intraoperative blood loss during total hip arthroplasty.

BACKGROUND AND OBJECTIVES: It is not clear whether cardiac output affects intraoperative blood loss under epidural hypotensive anesthesia. METHODS: Thirty patients undergoing primary total hip arthroplasty were randomly assigned to receive intravenous infusions of either low-dose epinephrine or phenylephrine to maintain mean arterial pressure at 50 to 60 mm Hg throughout surgery under lumbar epidural anesthesia. Patients were monitored with radial artery and thermodilution pulmonary artery catheters. Hemodynamic parameters were measured every 10 minutes during surgery, and blood loss was estimated by a blinded observer weighing sponges. RESULTS: Mean arterial pressure was similar between groups. Cardiac output remained unchanged in patients receiving low-dose epinephrine but declined significantly in patients receiving phenylephrine (p = 0.0001). Blood loss was 228 and 236 mL in patients receiving low-dose epinephrine and phenylephrine, respectively (p = 0.86). No correlation was observed between cardiac output and blood loss at any point during surgery. CONCLUSIONS: Cardiac output is not a factor influencing blood loss during hypotensive epidural anesthesia in elderly patients undergoing primary total hip arthroplasty.

Aged↗

PubMed1998

The principles of augmenting the cardiac output in adults.

Augmentation of the patient's cardiac output to optimize tissue oxygenation is a primary role of intensive and cardiac care nurses. This involves three approaches: the use of intravenous colloids and occasionally crystalloids, creating a passive stretching of the myocardium to increase cardiac output, the use of inotropic agents which directly stimulate the heart and finally and less commonly the use of cardiac assist devices, notably the intra aortic balloon pump. The choice of method will be dictated by the presenting clinical data and the perceived benefits to the patient of each approach. The role of nurses as part of the health care team is to practice safe, informed care, through an understanding of both the advantages and disadvantages of each approach to the clinical scenario encountered. This paper contains exploration of each of the three principles with a case study approach, allowing the reader to consider a variety of presenting clinical data and appropriate haemodynamic manipulation.

Adult↗

PubMed1983

Cardiac output and the recumbent position in late pregnancy.

Changes in cardiac output were measured by transcutaneous aortovelography in 30 pregnant patients and in 30 control subjects with change of position from the supine. When compared to the supine position, the left and right lateral and left 15 degrees tilt positions caused statistically significant increases in cardiac output, whereas the right 15 degrees tilt position did not. Neither fetal head engagement nor the time spent in each position had significant effects on the changes in cardiac output. It was not possible to identify a subgroup of pregnant patients who were particularly sensitive to changes in posture.

Adolescent↗

PubMed1993

A new method of measuring cardiac output in man using lithium dilution.

We describe a new indicator dilution method of measuring cardiac output in man. A bolus injection of lithium chloride 0.6 mmol was given via a central venous catheter and arterial plasma [Li+] recorded using a specially developed sensor incorporating an Li(+)-selective electrode. Cardiac output was derived from the lithium dilution curve, with a correction for packed cell volume. Lithium dilution cardiac output (LiDCO) was compared with thermodilution cardiac output (TD) using 22 lithium sensors in nine patients. For each sensor, one LiDCO was measured immediately before and one immediately after three TD estimations and mean values of LiDCO and TD derived. The correlation coefficient, r, was 0.89; slope of the regression 0.84; y intercept 0.72; bias 0.3 (0.5) litre min-1 (mean (TD-LiDCO) (1 SD). LiDCO appeared to be a safe, simple and accurate technique which does not require insertion of a pulmonary artery catheter.

Adult↗

PubMed2003

Three-dimensional echocardiographic determination of cardiac output at rest and under dobutamine stress: comparison with thermodilution measurements in the ischemic pig model.

Determination of cardiac output is a potentially important clinical application of three-dimensional (3-D) echocardiography since it could replace invasive measurements with the Swan-Ganz-catheter. To date, there are no studies available to determine whether cardiac output measured by thermodilution can be predicted reliably under changing hemodynamic conditions. Fifteen pigs with ischemic myocardium were examined under four hemodynamic conditions at rest and under pharmacological stress with 5, 10, and 20 microg/kg/min dobutamine. The 3-D datasets were recorded by means of transesophageal echocardiography. The endocardial definition was enhanced by administering the contrast agent FS069 (Optison). Cardiac output was calculated as the product of stroke volume (end-diastolic - end-systolic volume) and heart rate. The invasive measurements were performed with a continuous thermodilution system. In general, there was moderate correlation between 3-D echocardiography and thermodilution(r = 0.72, P < 0.001). At rest, the 3-D echocardiographic measurements were slightly but significantly lower than the invasive measurements (mean difference 0.6 +/- 0.5L/min,P < 0.001). Under stress with 5, 10, and 20 microg/kg/min dobutamine, there was a marked increase in the deviation (1.3 +/- 0.5L/min,P < 0.001; 1.6 +/- 0.7 L/min,P < 0.001; and 2.1 +/- 1.1L/min,P < 0.001, respectively). The deviation was based on two factors: (1). Under stress, the decreasing number of frames per cardiac cycle acquired with 3-D echocardiography led to imprecise recording of end-diastolic and end-systolic volumes, and thus to an underestimation of cardiac output. At least 30 frames per cardiac cycle are needed to eliminate this effect. (2). There is a systematic difference between 3-D echocardiographic and invasive measurements, which is independent of the imaging rate. This is based on an overestimation of the true values by thermodilution. In conclusion, cardiac output can be determined correctly by 3-D echocardiography for normal heart rates at rest. At elevated heart rates, the temporal resolution of 3-D systems currently available is not adequate for reliable determination. In performing and evaluating future clinical comparative studies, the systematic difference between 3-D echocardiography and thermodilution, based on overestimation by thermodilution, must be taken into account.

Animals↗

PubMed1980

[Measurement of cardiac output by electrical impedance plethysmography during respiration and in apnea].

The measurement of cardiac output by electrical impedance plethysmography (non-invasive technique) may be disturbed by a certain number of factors, including respiration. The authors sought to demonstrate that this factor could be eliminated during measurement calculations. By this method, in 18 adult subjects with coronary artery disease, 50 measurements during respiration and 50 measurements in apnoea (paired measurements) of stroke volume and of cardiac output were performed. Stroke volume was calculated using Kubicek's formula: SV = P(L2/Zo2) (dz/dt min)t Results were as follows: highly significant correlation between values for stroke volume obtained during respiration and in apnoea (r ;.9767; n=50; P < 0.001); highly significant correlation between values for cardiac output obtained under the same conditions (r = 0.9744; n=50; P < 0.001). The authors conclude that with the limits of certain technical conditions of measurement, respiration does not disturb measurements of stroke volume and of cardiac output by electrical impedance plethysmography.

Adult↗

PubMed1980

Depression of cardiac output is a mechanism of shunt reduction in the therapy of acute respiratory failure.

The relationship between changes in cardiac output and intrapulmonary shunt associated with mechanical ventilation was evaluated in 20 patients with the adult respiratory distress syndrome (ARDS). The distribution of ventilation-perfusion (VA/Q) ratios and the level of intrapulmonary shunt was determined by the multiple inert gas technique. Pulmonary blood flow was distributed predominantly to either effective gas-exchanging units or shunt units. Positive end-expiratory pressure (PEEP) or high tidal volume ventilation led to decreases in shunt and cardiac output without altering the overall pattern of VA/Q distributions. Changes in shunt and cardiac output were quantitatively and qualitatively silimar and a strong correlation was found between changes in shunt and cardiac output with both PEEP and high tidal volumes (r = 0.76). Cardiac output depression associated with tese modes of ventilation appears to be a mechanism of shunt reduction in ARDS. Interpretation of improvements in gas exchange in ARDS must take into account concomitant hemodynamic changes.

Blood Pressure↗

PubMed1990

[Comparison of the hemodynamic effects of dobutamine and enoximone in the treatment of low cardiac output after valvular surgery].

Forty patients developed low cardiac output states after surgery for mitral valve disease or with associated cardiac disease and were randomly allocated to two treatment groups, one group to receive Dobutamine (D) and the other Enoximone (E), a phosphodiesterase inhibitor. Haemodynamic assessment covered a 24 hour period but treatment was continued for as long as was necessary. An improvement was observed from the 15th minute of treatment. At the second hour, the cardiac index had increased by 55% in Group E and by 59% in Group D whilst the heart rate increased by only 12% in Group E compared to 30% in Group D. The right and left heart filling pressures decreased by 25 to 27% in the 2 groups. The systemic arterial resistances fell by 36 to 37% without any significant changes in systemic or pulmonary arterial pressures. No significant difference was demonstrated in the haemodynamic responses to Dobutamine and Enoximone in this study. The duration of treatment was significantly shorter in Group E than in Group D (59 +/- 22 hrs vs 86 +/- 49 hrs) as was the patient's stay in the intensive care unit (92 +/- 37 hrs vs 155 +/- 129 hrs). The duration of assisted ventilation was the same in the two groups. These results suggest that Enoximone is as effective as Dobutamine in the treatment of low cardiac output after mitral valve surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1998

Continuous cardiac output and mixed venous oxygen saturation monitoring.

Continuous assessment of cardiac output and SVO2 in the critically ill may be helpful in both the monitoring variations in the patient's cardiovascular state and in determining the efficacy of therapy. Commercially available continuous cardiac output (CCO) monitoring systems are based on the pulsed warm thermodilution technique. In vitro validation studies have demonstrated that this method provides higher accuracy and greater resistance to thermal noise than standard bolus thermodilution techniques. Numerous clinical studies comparing bolus with continuous thermodilution techniques have shown this technique similarly accurate to track each other and to have negligible bias between them. The comparison between continuous thermal and other cardiac output methods also demonstrates good precision of the continuous thermal technique. Accuracy of continuous oximetry monitoring using reflectance oximetry via fiberoptics has been assessed both in vitro and in vivo. Most of the studies testing agreement between continuous SVO2 measurements and pulmonary arterial blood samples measured by standard oximetry have shown good correlation. Continuous SVO2 monitoring is often used in the management of critically ill patients. The most recently designed pulmonary artery catheters are now able to simultaneously measure either SVO2 and CCO or SVO2 and right ventricular ejection fraction. This ability to view simultaneous trends of SVO2 and right ventricular performance parameters will probably allow the clinician to graphically see the impact of volume loading or inotropic therapy over time, as well as the influence of multiple factors, including right ventricular dysfunction, on SVO2. However, the cost-effectiveness of new pulmonary artery catheters application remains still questionable because no established utility or therapeutic guidelines are available.

Animals↗

PubMed1996

The relationship between anaesthetic uptake and cardiac output.

The hypothesis that anaesthetic uptake during maintenance of anaesthesia is related to cardiac output was tested on 21 patients undergoing cardiac surgery. Using a computer-controlled closed breathing system, enflurane was administered to maintain an end-expired concentration of 1%. Cardiac output was measured by thermodilution using a pulmonary artery catheter. A clear qualitative but not quantitative relationship was demonstrated. Changes in anaesthetic requirements at a constant end-expired concentration are a better guide to changes in cardiac output than changes in end-expired carbon dioxide with constant ventilation in patients undergoing cardiac surgery.

Anesthetics, Inhalation↗

PubMed1992

Relative effects of fat-, carbohydrate- and protein-containing liquid diets on cardiac output in healthy adult subjects.

1. Nine healthy adult subjects consumed four types of proprietary liquid diet of similar volume and calorific value but of different nutritional composition. The effects on resting cardiac output, mean blood pressure and pulse rate were measured. 2. A significant rise in cardiac output occurred with the balanced, protein and carbohydrate diets but not with the fat diet. The greatest rise was seen with the balanced diet. Water alone had no effect on cardiac output. 3. The average time taken to reach peak cardiac output was shortest with the carbohydrate diet and longest with the fat diet. 4. The increases in cardiac output resulted from a rise in both pulse rate and stroke volume. The carbohydrate diet produced the most sustained rise in pulse rate but the least sustained elevation in stroke volume. 5. No significant changes were seen in mean blood pressure when each liquid meal was compared with water. 6. Our data show that the increase in cardiac output with liquid ingestion is related to the dietary components. These effects are additive.

Adult↗

PubMed1998

Can measurement of mixed venous oxygen saturation replace measurement of cardiac output in patients with advanced heart failure?

BACKGROUND: Nursing care of patients with advanced heart failure with low ejection fraction requires strict management of IV fluids. Measurement of mixed venous oxygen saturation offers advantages over measurement of cardiac output because no administration of fluid is required and data are obtained continuously. OBJECTIVES: To determine the relationship between mixed venous oxygen saturation and cardiac output in patients with advanced heart failure who have low ejection fraction and to determine if use of vasoactive medications alters the relationship between mixed venous oxygen saturation and cardiac output. METHODS: Simultaneously obtained measurements of mixed venous oxygen saturation and cardiac output were compared in 42 patients with advanced heart failure with ejection fractions of 30% or less (mean, 19.5%). RESULTS: Correlation between mixed venous oxygen saturation and cardiac output was r = 0.54 (P < .001). For subjects not receiving vasoactive medications (n = 28), r = 0.52 (P = .004); for those receiving vasoactive medications (n = 14), r = 0.57 (P = .03). CONCLUSIONS: Similar correlations in the groups receiving and not receiving vasoactive medications suggest that even with pharmacological support, changes in mixed venous oxygen saturation may not be reflected by concomitant changes in cardiac output. Measurement of mixed venous oxygen saturation should not replace measurement of cardiac output for clinical decision making in patients with advanced heart failure with low ejection fraction.

Adolescent↗

PubMed1985

[Effects of injectable flunitrazepam on hepatic and cardiac output in man].

The effects of intravenous flunitrazepam (0.03 mg X kg-1) on the estimated hepatic plasma output (DPHE), compared with the cardiac output (Q), were studied before its injection and 1 min afterwards. The question asked was whether the decrease in venous return led to a fall in hepatic perfusion. This study was made on patients in neurological coma without any organic lesion. The DPHE was measured by applying Fick's principle, using a continuous infusion of indocyanine green (ICG). The DPHE was given by the amount of ICG perfused in mg X min-1 divided by the arterial concentration of ICG less the concentration of ICG in the hepatic vein (in mg X 1(-1)). Cardiac output was measured by thermodilution. Flunitrazepam did not significantly modify either DPHE or Q; they fell by 5.6% and 3.4% respectively. None of the seven cardiovascular parameters changed during the time of the study. Thus, in unconscious patients with satisfactory haemodynamic conditions prior to the intravenous injection, flunitrazepam did not significantly modify hepatic perfusion.

Adolescent↗

PubMed1988

Effect of respiratory cycle on measurements of cardiac output by thermodilution.

Current recommendations for obtaining reproducible measurements of cardiac output by thermodilution are contradictory. Several investigators have shown that reproducibility of measurements can be improved by initiating injections at specific moments in the respiratory cycle. We prospectively studied 31 patients, comparing three thermodilution measurements of cardiac output at peak-inspiration, end-exhalation and random in mechanically ventilated patients. Patients were separated into two groups: group 1 was composed of intubated patients on intermittent mandatory ventilation (IMV) without spontaneous overbreathing, and group 2 included patients on IMV with spontaneous overbreathing. The results from this study demonstrated no statistical difference in the ranges or standard deviations of the measurements of cardiac output among injections initiated at random, peak-inspiration or end-exhalation in either group. We conclude that the reproducibility of measurements cannot be enhanced by initiating injections at specific moments in the respiratory cycle.

Analysis of Variance↗