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Transthoracic cardiac pacing is frequently associated with simultaneous stimulation of skeletal muscle and nerves. We describe a patient in cardiogenic shock and complete heart block in whom the associated vigorous abdominal and chest muscle contractions caused by transthoracic cardiac pacing resulted in a marked augmentation of cardiac output and systemic blood pressure via a "CPR" effect.
The distribution of cardiac output (CO) between compliant and noncompliant organs is an important determinant of the slope of the relationship predicted between CO and right atrial pressure (RAP). However, curves relating CO to RAP at rest are shifted rightward (higher CO) and upward (higher RAP) by exercise with no change in slope, despite a large rise in the fraction of CO directed to noncompliant muscle vasculature, which is predicted to decrease the slope. We sought to test whether reductions in CO imposed during rest and exercise are accompanied by changes in its distribution that would favor constant slopes. Six dogs had atrioventricular block produced surgically and had blood flow transducers implanted on the ascending aorta and the terminal aorta. Total muscle blood flow (MBF) was estimated from terminal aortic flow by assuming that all of the increase in CO in mild dynamic exercise is directed to muscle. CO was reduced by lowering ventricular pacing rate at rest and during graded treadmill exercise (2 and 4 miles/h at 0% grade). Exercise increased the fraction of CO directed to muscle (MBF/CO) (P < 0.001). The effect of changes in CO on MBF/CO depended on exercise intensity (P < 0.01). At rest, MBF/CO fell from 0.53 to 0.45 when CO was reduced; this is expected to reduce the slope of the measured relationship between CO and RAP. During exercise at 2 miles/h, MBF/CO changed little when CO was reduced.(ABSTRACT TRUNCATED AT 250 WORDS)
This case report describes the use of enoximone, a potent phosphodiesterase F-IV inhibitor with inotropic and vasodilator actions, to treat low output syndrome after cardiac surgery. The reduced cardiac output was unresponsive to a combination of inotropic drugs and intra-aortic balloon counterpulsation was contraindicated. Cardiac output was increased dramatically by enoximone, but systemic vascular resistance and perfusion pressure remained low until the addition of metaraminol.
Chronic administration of intravenous adriamycin (1 mg . kg-1 twice weekly for 8 weeks) to rabbits resulted in a cardiomyopathy which was similar to that occurring in patients with adriamycin cardiotoxicity. We studied systemic and renal haemodynamics and the activation of vasoconstrictor mechanisms reflected by changes in plasma renin activity (PRA), noradrenaline (NA) and vasopressin (AVP) levels during the development of heart failure in this animal model. By 8 weeks cardiac failure was clearly established. At postmortem all animals had dilated hearts, pleural and pericardial effusions, ascites and hepatic congestion. Heart weights were increased (8.1 +/- 0.7 g in treated animals n = 9 vs 6.0 +/- 0.2 g in controls n = 9 p less than 0.05). Cardiac output (measured by thermodilution) fell at 8 weeks from 799 +/- 61 ml . min-1 to 624 +/- 44 ml . min-1 (n = 6 p less than 0.05) with a parallel fall in mean blood pressure from 85 +/- 2 mmHg to 75 +/- 4 mmHg. Total peripheral resistance rose in four of the six rabbits. Renal blood flow fell from 108 +/- 4 ml . min-1 to 61 +/- 6 ml . min-1 (p less than 0.05) by 8 weeks. Renal vascular resistance increased in all animals. PRA increased from 5.1 +/- 0.5 ng AI . ml-1 . h-1 to 11.6 +/- 2.6 ng AI . ml-1 . h-1 by 4 weeks (p less than 0.05) and remained elevated thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)
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In low-output cardiac failure with hypertension developing early after aortocoronary surgery, the currently preferred vasodilators nitroglycerin and nitroprusside proved to be equally successful and safe for the closed-loop control of mean arterial pressure. With NP- and NTG-induced MAP reduction to the present level of 80 mm Hg cardiac index increased similarly from 2.0 +/- 0.35 to 2.4 +/- 0.3 l/min/m2 (p less than 0.05) and from 1.9 +/- 0.29 to 2.2 +/- 0.26 l/min/m2 (p less than 0.05), respectively. Once adequate blood pressure fall was obtained, the addition of dobutamine at 6 micrograms/kg/min resulted under maintenance doses of NP and NTG averaging 1.6 +/- 0.4 and 4.6 +/- 1.8 micrograms/kg/min, respectively. A further improvement of cardiac performance manifested itself by cardiac index rise to 3.4 +/- 0.4 l/min/m2 (p less than 0.005) and 3.3 +/- 0.3 l/min/m2 (p less than 0.001), respectively. The NP-Db and NTG-Db regimens induced comparable reductions of rate - pressure-products reflecting a decrease of myocardial oxygen demands and facilitation of myocardial work.
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Plasma renin activity and aldosterone concentration were measured by radioimmunoassay technique in seven patients with low cardiac output syndrome after open cardiac surgery. Plasma renin activity and aldosterone concentration markedly increased, and plasma renin activity was well correlated with plasma aldosterone concentration. Plasma renin activity and aldosterone concentration, however, had no direct correlation with plasma sodium and potassium concentration or administered doses of inotropic agent, potassium and diuretic. Sodium and potassium balance was closely correlated with plasma aldosterone concentration. In the present study, it was suggested that the secondary hyperaldosteronism following low cardiac output syndrome after open cardiac surgery was mainly induced by the increased release of renin and that it influenced on the balance of sodium and potassium metabolism under such disturbed circulatory circumstances.
BACKGROUND: Cardiac output is often monitored after cardiac operations with a pulmonary artery catheter. A new method has been introduced that measures cardiac output by lithium dilution (LiDCO) and uses these data to calibrate a system (PulseCO) that calculates cardiac output continuously from the energy of the arterial pressure waveform. It is unknown whether PulseCO measurements are valid early after cardiac surgery when changes in temperature and vascular tone or intermittent use of the arterial line for blood sampling may occur. This study assessed the reliability of cardiac output determinations by PulseCO in the first 8 hours after cardiac surgery. METHODS: After a one-time PulseCO calibration, cardiac output was measured in 20 patients who had undergone coronary artery bypass grafting at 0, 2, 4, 6, and 8 hours after arrival in the intensive care unit using (1) thermodilution through a pulmonary artery catheter (Thermo); (2) lithium dilution (LiDCO); and (3) PulseCO. Concordance correlations were calculated between methods, and differences were compared by Wilcoxon paired rank test and Bland-Altman analysis. RESULTS: Cardiac output ranged from 3.4 to 8.5 L/min. No significant differences were noted between measurements obtained by each technique at any time point. Concordance correlations and Bland-Altman analysis confirmed good agreement between PulseCO and Thermo determinations of cardiac output during the study interval. CONCLUSIONS: PulseCO measurements remain reliable without recalibration for at least 8 hours after cardiac surgery and may offer a less-invasive approach for early postoperative cardiac output monitoring.
BACKGROUND: Cardiac output (CO) is likely to influence the pharmacokinetics of anesthetic drugs and should be accounted for in pharmacokinetic models. The influence of CO on the pharmacokinetic parameters of alfentanil in pigs was evaluated using compartmental and recirculatory models. METHODS: Twenty-four premedicated pigs were evaluated during halothane (0.6-2%) anesthesia. They were assigned randomly to one of three groups. One group served as control. In the other groups, the baseline CO was decreased or increased by 40% by pharmacologic intervention (propranolol or dobutamine). Boluses of alfentanil (2 mg) and indocyanine green (25 mg) were injected into the right atrium. Blood samples were taken for 150 min from the right atrium and aortic root. Arterial concentration-time curves of indocyanine green and alfentanil were analyzed using compartmental models (two-stage and mixed-effects approach) and a recirculatory model, which can describe lung uptake and early distribution. RESULTS: The CO of individual pigs varied from 1.33 to 6.44 l/min. Three-compartmental modeling showed that CO is a determinant of the central compartment volume (V1, r2 = 0.54), fast peripheral compartment volume (V2, r2 = 0.29), steady state distribution volume (Vss, r2 = 0.29), fast distribution clearance (Cl12, r2 = 0.39), and elimination clearance (Cl10, r2 = 0.51). Recirculatory modeling showed that CO is a determinant of total distribution volume (r2 = 0.48), elimination clearance (r2 = 0.54), and some distribution clearances. The pulmonary distribution volume was independent of CO. CONCLUSIONS: Cardiac output markedly influences the pharmacokinetics of alfentanil in pigs. Therefore, accounting for CO enhances the predictive value of pharmacokinetic models of alfentanil.
There is a significant morbidity and mortality associated with elective infrarenal aortic reconstruction. To examine the value of continuous cardiac output monitoring for predicting those at risk, 40 consecutive patients were monitored using Doppler-derived cardiac output. The anaesthetist was blind to all information from the monitor and managed the patients using standard techniques. In 28 patients there were no observed changes, while in seven, cardiac output rose after aortic cross-clamping. In five patients a fall in cardiac output occurred after cross-clamping. No cardiac events or cardiac deaths occurred in the 35 patients who showed a rise or no change in cardiac output. However, there were three cardiac events, including one cardiac death in the group of five patients in whom a fall in cardiac output was observed. It would appear that intraoperative non-invasive Doppler-derived cardiac output monitoring successfully predicts high-risk patients who would perhaps benefit from more intensive pre-, peri- and postoperative care.
The purpose of the present study was to compare the impedance derivate waveforms using spot and band electrode array and to assess applicability of automated signal processing system for cardiac output kinetics. Five healthy male subjects were tested. Cardiac output (Q) were measured using spot electrode array. Each subject performed rest-exercise transitions in leg and arm exercise on an electrically braked ergometer. The intensities of leg exercise were 25, 50, and 100 W for 5 min and those of arm exercise were 25 and 50 W. Comparisons between spot and band electrodes were made for the absolute magnitude of Q and stroke volume (SV), as well as for impedance derivative waveforms. The waveforms for spot electrodes showed less fluctuation by breathing and movement artifacts than for band electrodes. Q for spot electrodes were larger than those for band electrodes. There was a significant correlationship between oxygen uptake (Vo2) and Q. There was a significant correlationship between Q using spot electrode and Q measured by CO2 rebreathing method. Nonlinear correlation coefficient to exponential curve of Q kinetics for leg exercise was more than 0.7 and for arm exercise more than 0.4 in spite of large movement of upper body. It is suggested that the present system using spot electrodes is superior in signal processing to those for band electrodes and able to evaluate Q kinetics without multiple repetition of exercise tests.
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Ninety-two mean thermodilution cardiac indices were determined in 25 patients following cardiac operations. Arterial and venous blood gases, hematocrit, body temperature, central venous pressure, left atrial pressures, urine output, heart rate, and mean arterial pressure were simultaneously recorded. Six variables, arterial and venous pH, arterial and venous PCO2, venous PO2, and temperature, showed significant simple correlations with cardiac index, but the degree of correlation was inadequate for use of these variables as reliable indices of cardiac function. When stepwise multiple regression analysis was performed, two variables, venous PO2 and left atrial pressure were associated with the best correlation with cardiac index, such that CI = 0.073 PO2V -- 0.060 LAP + 1.39 (r = 0.60, p less than 0.001). When measured values for venous PO2 and left atrial pressure were substituted into this equation, a "predicted" value for cardiac index could be obtained with only slightly improved reliability. The data indicate that indirect estimation of cardiac output by measurement of the various laboratory parameters described above is not sufficiently reliable for clinical use. The importance of obtaining direct measurements of cardiac output by thermodilution or other means in order to properly evaluate postoperative cardiac function is stressed.
This study examined the effect of impedance algorithm adjustment to reflect abnormalities found in cardiac output estimation in the intensive care unit. Impedance (Kubicek and Sramek equations) and thermodilution were measured concurrently in 61 patients. The mean difference between Kubicek and thermodilution (n=40) was 1.47 L/min (95% confidence interval [CI], 0.47-2.47) and between Sramek and thermodilution (n=54) was 2.68 L/min (95% CI, 1.93-3.44). Exclusion of patients with valve regurgitation improved agreement between Kubicek and thermodilution (n=32), with a mean difference of 2.02 L/min (95% CI, 1.10-2.94). Multiple regression determined the role of skinfold thickness, pH, hematocrit, sodium, chloride, albumin, protein, and urea within impedance. Kubicek was recalculated using the new algorithm and recompared with thermodilution. The mean difference was -0.38 L/min (95% CI, -1.92 to 1.16). This study found poor agreement between impedance and thermodilution in critically ill patients, but exclusion of those with valve regurgitation and adjustment for hematocrit and skinfold thickness improved agreement.
OBJECTIVE: To describe the accuracy and the reproducibility of the thermodilution flow measurements obtained using 3 commercially available cardiac output computers commonly used in intensive care units. DESIGN: An experimental "in vitro" study. Twelve different values of control flow (Qctr) were measured (Qmsr) using 3 different cardiac output computers (Abbott Critical Care System, Oximetrix 3 SvO2/CO Computer, Baxter Oximeter/Cardiac Output Computer SAT-1; American Edwards Laboratories, 9520 A Cardiac Output Computer). Standard equipment and techniques were employed, taking account of the specific weight and heat of warm water relative to blood. In addition, separate sets of measurements were performed in order to investigate the effect on Qmsr of some variables which may influence the "indicator" loss (time for injection, depth of immersion of the catheter, temperature of the injected fluid). SETTING: Our laboratory, inside the intensive care unit. MEASUREMENTS AND RESULTS: The analysis of the linear regression of Qmsr versus Qctr (r values between 0.992 and 0.984; residual standard deviation values comprised between 0.24 and 0.49 l/min; intercepts and slopes not significantly different from identity line), the values of the percentage errors (PE = [Qctr-Qmsr].100/Qctr; PE mean values 7.9, 5.0 and 13.1), and those of the coefficients of variability (CV = standard deviation mean value, %; CV mean values 5.4, 5.8 and 4.6), show a good level of accuracy and reproducibility of the measurements. Our data confirm previously reported results. Furthermore, the cumulative effect of variables capable of influencing the "indicator" loss, even if corrected according to the "calculation constant" the manufacturers provide, was found to result in statistically significant changes of Qmsr. CONCLUSION: The accuracy and reproducibility of the automatic cardiac computers tested is sufficient for practical clinical purpose. It may also depend on the modality of injection of the cooling bolus, which may significantly influence the effective "indicator" losses.
OBJECTIVE: To investigate in a direct comparison accuracy and precision of continuous cardiac output measurements assessed by continuous pulmonary artery thermodilution technique (TDCCO), continuous pulse contour analysis (PCCO), and noninvasive partial CO(2)-rebreathing technique (NICO) in patients after coronary artery bypass grafting (CABG) during the postoperative period. DESIGN: Prospective, controlled clinical study. SETTING: University hospital. PARTICIPANTS: Twenty-two patients undergoing elective CABG surgery. INTERVENTIONS: Hemodynamic measurements were performed after admission to the ICU and in sequence every 2 hours during the subsequent 6-hour period. Simultaneously, cardiac output (CO) was measured using a TDCCO, PCCO, and NICO. After the continuous cardiac output measurements were read, bolus thermodilution-derived cardiac output was obtained from thermodilution curves detected in the pulmonary artery (TDBCO(pa)). Four intermittent consecutive boli consisting of 10 mL of ice-cold saline were randomly injected over the ventilatory cycle. MEASUREMENTS AND MAIN RESULTS: The comparison between the continuous cardiac output measurement methods TDCCO versus PCCO showed a bias of -0.12 L/min, between TDCCO versus NICO -0.17 L/min, and between PCCO versus NICO -0.44 L/min. The comparison to the reference technique between TDBCO(pa) versus TDCCO revealed a bias of -0.28 L/min, between TDBCO(pa) versus PCCO -0.40 L/min, and between TDBCO(pa) versus NICO -0.64 L/min. CONCLUSIONS: The results of this clinical investigation show agreement between TDCCO and PCCO to satisfy clinical requirements in a setting of postoperative patients after cardiac surgery. In contrast, the NICO monitor is of very limited use in these patients.