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PubMed1987

Laser Doppler flowmetry and cardiac output in critically ill surgical patients.

Laser Doppler flowmetry (LDF) accurately measures cutaneous microcirculatory blood flow. We compared change in LDF flow to change in thermodilution cardiac output in ten critically ill surgical patients. A subset analysis of three patients with low cardiac output (cardiac index less than 2 L/min X m2) showed no correlation. We conclude that, under these study conditions, LDF microcirculatory flow did not reflect macrocirculatory flow. We conjecture that overcoming cutaneous vasoregulation with thermal vasodilation may obviate these results.

Adult↗
PubMed2000

The effect of lung injury and excessive lung fluid, on impedance cardiac output measurements, in the critically ill.

OBJECTIVES: To investigate the relationship between the attenuation of impedance cardiac output (IC(co)) measurements and lung fluid content in critically ill patients. DESIGN: Observational study. SETTING: Intensive Care Unit of a major teaching hospital in Hong Kong. PATIENTS: Twenty-four critically ill patients who required a pulmonary artery catheter. MEASUREMENTS AND MAIN RESULTS: Triplicate thermodilution cardiac output (TD(co)) and BoMed NCCOM3 (IC(co)) measurements were made simultaneously on a single occasion in each patient. Lung fluid accumulation was assessed by: (a) thoracic impedance (Zo), (b) radiological assessment of chest X-rays using an alveolar consolidation score (0-4) and (c) scoring the degree of hypoxia and use of positive end-expiratory pressure (PEEP). Offsets (TD(co)-IC(co))/TD(co), expressed as percentage, were compared with these indices of excess lung fluid. Patients were divided into those with sepsis (n = 13), fluid balance problems (n = 5) and cardiothoracic problems (n = 6). Mean cardiac output values were: 6.7 l/min TD(co) (range 3.6-12.9) and 5.2 l/min IC(co) (range 2.7-9.0). Overall the TD(co) and IC(co) values showed great variance, with a bias and limits of agreement of 1.49 +/- 4.16 l/min, or +/- 69%. In septic patients, increasing offset was correlated with decreases in Zo (r = 0.73, P = 0.005) and increases in alveolar consolidation score (r = 0.72, P = 0.005). CONCLUSIONS: The BoMed under-estimates cardiac output in critically ill patients. In septic patients the degree of attenuation of IC(co) can be related to the extent of lung injury and fluid accumulation within the thorax.

Adult↗
PubMed1988

Cardiac output changes and continuous mixed venous oxygen saturation measurement in the critically ill.

For many years, the pulmonary artery catheter has been used to monitor cardiac filling pressures and to determine cardiac output in hemodynamically unstable patients. Recently, a new pulmonary artery catheter with fiberoptic capabilities, which provides continuous mixed venous O2 saturation (SvO2) measurements, has become available and has been found to be helpful in managing unstable patients. To determine the efficacy of this device in predicting early changes in cardiac output, we studied 46 patients catheterized with the opticath and 25 with the standard pulmonary artery catheter; we compared changes in the SvO2 with associated cardiac index changes. We found that small changes (5%) in SvO2 did not correlate well with changes in cardiac output, yet larger changes (10%) in SvO2 seemed to correlate better. More importantly, we found that only 50% of the SvO2 changes predicted anticipated changes in cardiac output. As can best be determined from the limitations of a nonrandomized study, the value of continuous SvO2 monitoring as an early predictor of cardiac output change remains questionable.

Cardiac Output↗
PubMed1990

Effects of dextran infusion on cardiac output, oxygen delivery, and oxygen utilization in piglets during the first month of life.

We determined the effects of volume infusion on cardiac output, oxygen delivery (Do2), oxygen consumption (Vo2), and oxygen extraction (O2 extr) in piglets at ages 5 to 14 days and 3 to 5 wk. Eighteen piglets were anesthetized, intubated, and mechanically ventilated. Six piglets (5 to 14 days old) and six piglets (3 to 5 wk old) received iv dextran (MW 70,000 daltons; 30 to 40 ml/kg) sufficient to raise mean left atrial pressure (LAP) from approximately 4 to 15 mm Hg over 30 min. Six piglets received 0.9% NaCl at 4 ml/kg.h to maintain LAP constant at 4 mm Hg over a 30-min period. All piglets receiving dextran had increased cardiac output (mean elevation 39 +/- 16 [SD]%; range +19% to +73%; p less than .005). This response was mediated entirely by an elevation in stroke volume, as heart rate did not change significantly. However, all piglets receiving dextran reduced Hgb concentration (10.1 +/- 1.5 to 7.5 +/- 1.4 g/dl, p less than .001), a decrease which completely offset the increase in cardiac output. Consequently, Do2 did not increase after dextran infusion (17.4 +/- 1.8 to 18.4 +/- 2.8 ml/min.kg). Neither Vo2 nor O2 extr changed significantly after dextran. No differences were noted in the response to dextran infusion comparing 5 to 14-day-old piglets with 3 to 5-wk-old piglets. Unlike fetal lambs, newborn piglets are able to elevate cardiac output significantly in response to volume loading. However, if these data can be extrapolated to human infants, volume infusion without concurrent blood transfusion is likely to increase systemic cardiac output but not improve Do2.

Animals↗
PubMed1976

On-line cardiac output by digital computer.

Many devices for fast cardiac output calculations employ special assumptions and departures from the Stewart-Hamilton method. These assumptions and departures can cause substantial errors. This publication describes an on-line computer system for evaluating dye-dilution curves according to the classical Stewart-Hamilton method. Dilution curves are smoothed, using a digital filter to eliminate heartbeat noise. Recirculation is removed using the constant ratio property of exponentials. The quality of the curves is evaluated by determining the length of the base line, the extent and the fit to an exponential downslope, and a figure of merit based on the five tanks-in-series model. Dilution curves, the logarithmic form, and the exponential ratios are displayed on a CRT for visual checks. Comparison of cardiac outputs obtained by this on-line system with results obtained by hand calculations showed a mean difference of 150 ml. Repeated evaluation of one electronically simulated dye curve resulted in SD = 10 ml for computer results and SD = 200 ml for hand calculations.

Animals↗
PubMed1984

The effects of tolazoline on the distribution of cardiac output in normoxemic and hypoxemic lambs.

We measured cardiac output and its distribution (microspheres), blood gases and pH, heart rate, and pulmonary and aortic pressures in three groups of 1- to 3-day-old lambs. Group I consisted of six animals who had these measurements made during both control (normoxemic) and hypoxemic (PaO2 25 +/- 3 mm Hg) periods. Hypoxemia increased the pulmonary artery pressure 70% (p less than 0.01). This elevation in pulmonary arterial pressure lasted as long as the animals were hypoxemic (90 min). Hypoxemia had no effect on cardiac output, mean systemic arterial pressure, heart rate, or the rate-pressure product of the left ventricle. Blood flow to the heart increased an average of 228% (p less than 0.05); flow to the brain increased 233% (p less than 0.05); flow to the skin decreased 35% (p less than 0.05) after 60 and 90 min of hypoxemia. Blood flow to the remaining organs was uneffected by hypoxemia. Group II consisted of four animals who were given 1, 5, and 10 mg/kg/h of tolazoline (Priscoline) intravenously while normoxemic. There was no effect on the pulmonary arterial pressures or blood gases and pH. Tolazoline (5 and 10 mg/kg/h) reduced systemic arterial pressures an average of 22% (p less than 0.05). Tolazoline (1 mg/kg/h) reduced blood flow to the spleen 48% and that to the brain by 20% and increased flow to the body 32% (p less than 0.05). Five mg/kg/h of tolazoline decreased renal and brain blood flow 35 and 20%, respectively (p less than 0.05) while that to the body and liver increased 26 and 48% (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1980

Regional distribution of cardiac output in conscious rats at rest and during exercise. Effects of diltiazem.

The effects of intravenous infusion of the calcium antagonist, diltiazem (6, 30, and 150 mg/kg/hr) on cardiac and circulatory hemodynamics and on regional blood flow and cardiac output distribution to the major peripheral circulations were studied in conscious, normal Sprague-Dawley rats in the resting state. Therapy with diltiazem consistently increased cardiac output levels, as well as stroke volume, and decreased mean arterial pressure and systemic vascular resistance in a dose-related fashion. Diltiazem had a substantial effect on increasing coronary blood flow and reducing coronary vascular resistance. Effects of similar direction and magnitude were observed in the cerebral and hepatic arterial circulations. In a second study, rats were subjected to a submaximal treadmill exercise protocol during continuous intravenous infusion of either saline solution or diltiazem (DZ) in order to determine the effects of this agent on cardiac output distribution during exercise. The results indicate that the positive effects of diltiazem on cardiac output are maintained during exercise. The increase in cardiac output with diltiazem appears to be distributed throughout the major regional circulations in proportion to regional demand.

Animals↗
PubMed1996

Influence of levosimendan, pimobendan, and milrinone on the regional distribution of cardiac output in anaesthetized dogs.

1. The distribution of cardiac output during administration of levosimendan, a new myofilament calcium sensitizer, is unknown. We examined and compared the effects of levosimendan, pimobendan, and milrinone on regional tissue perfusion by use of the radioactive microsphere technique in barbiturate-anaesthetized dogs. 2. Haemodynamics and regional blood flow were determined before and during infusions of levosimendan (0.75, 1.5, and 3.0 micrograms kg-1 min-1), pimobendan (10, 20, and 40 micrograms kg-1 min-1), or milrinone (1.0, 2.0, and 4.0 micrograms kg-1 min-1). 3. All three drugs caused similar increases in heart rate, cardiac output, and left ventricular +dP/dt and decreases in end-diastolic pressure and systemic vascular resistance. No changes in subendocardial, midmyocardial, and subepicardial blood flow occurred during administration of levosimendan. However, a redistribution of blood flow from subendocardium to subepicardium was observed. Pimobendan increased midmyocardial and subepicardial blood flow and reduced the endo/epi ratio to a greater degree than levosimendan. Milrinone did not affect myocardial perfusion. 4. Levosimendan increased blood flow to the renal medulla and decreased renal medullary and cortical vascular resistance. Levosimendan increased blood flow to the small intestine and liver and reduced vascular resistance in these organs. Pimobendan increased hepatic blood flow to a greater degree than levosimendan but did not alter small intestinal perfusion. All three drugs decreased splenic blood flow to similar degrees. Levosimendan and pimobendan reduced cerebral vascular resistance. Levosimendan and milrinone reduced skeletal muscle vascular resistance. 5. The results indicate that levosimendan, pimobendan, and milrinone cause subtlety different alterations in regional tissue perfusion while producing similar haemodynamic effects.

Anesthesia↗
PubMed2006

Noninvasive assessment of cardiac output using thoracic electrical bioimpedance in hemodynamically stable and unstable patients after cardiac surgery: a comparison with pulmonary artery thermodilution.

OBJECTIVE: To compare noninvasive cardiac output (CO)measurement obtained with a new thoracic electrical bioimpedance (TEB) device, using a proprietary modification of the impedance equation, with invasive measurement obtained via pulmonary artery thermodilution. DESIGN: Prospective, observational study. SETTING: Surgical intensive care unit (ICU) of a university-affiliated community hospital. PATIENTS AND PARTICIPANTS: Seventy-four adult patients undergoing elective cardiac surgery with routine pulmonary artery catheter placement. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Simultaneous paired CO and cardiac index (CI) measurements by TEB and thermodilution were obtained in mechanically ventilated patients upon admission to the ICU. For analysis of CI data the patients were subdivided into a hemodynamically stable group and a hemodynamically unstable group. The groups were analyzed using linear regression and tests of bias and precision. We found a significant correlation between thermodilution and TEB (r = 0.83; n < 0.001), accompanied by a bias of -0.01 l/min/m(2) and a precision of +/-0.57 l/min/m(2) for all CI data pairs. Correlation, bias, and precision were not influenced by stratification of the data. The correlation coefficient, bias, and precision for CI were 0.86 (n< 0.001), 0.03 l/min/m(2), and +/-0.47 l/min/m(2) in hemodynamically stable patients and 0.79 (n< 0.001), 0.06 l/min/m(2), and +/-0.68 l/min/m(2) in hemodynamically unstable patients. CONCLUSIONS: Our results demonstrate a close correlation and clinically acceptable agreement and precision between CO measurements obtained with impedance cardiography using a new algorithm to calculate CO from variations in TEB, and those obtained with the clinical standard of care, pulmonary artery thermodilution, in hemodynamically stable and unstable patients after cardiac surgery.

Aged↗
PubMed1987

Comparison of the effects of intravenous and intrasplenic infusions of glucagon on cardiac output and its distribution in the rat.

In order to determine whether or not glucagon released from the pancreas might have local vascular effects, the actions upon regional haemodynamics in the anaesthetised rat of two doses of glucagon (2 and 10 micrograms kg-1 min-1) infused intrasplenically (and thus into the portal vein) were compared with those of a single dose (2 micrograms kg-1 min-1) infused i.v. Infusion of glucagon i.v. produced a significantly increased heart rate (by 6%) and cardiac output (by 23%) in the experimental animals compared to those receiving saline by the same route. Total peripheral resistance fell by 24%. A greater proportion of the cardiac output passed to the coronary and renal vascular beds and blood flow was increased in the spleen, testes, pectoral skeletal muscle, stomach and small intestine as well as the heart and kidneys. The lower dose infused intrasplenically had no significant effect on cardiac output or total peripheral resistance but significantly increased the proportion of cardiac output passing both to the stomach and the small intestine such that the percentage of cardiac output flowing through the portal vein increased from 19.1 +/- 1.1% to 23.8 +/- 1.7%. Intrasplenic infusion of 10 micrograms kg-1 min-1 significantly increased cardiac output (by 29%) but reduced total peripheral resistance by 37%. Greater fractions of the cardiac output were received by the spleen, small intestine and epididymides. Blood flow was increased in these organs and the skin, kidneys, stomach, large intestine and the mesentery. It is concluded that pharmacologically effective amounts of glucagon only passed into the systemic circulation with the higher dose infused intrasplenically.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

Cardiac output during hemiarthroplasty of the hip. A prospective, controlled trial of cemented and uncemented prostheses.

In a prospective, controlled study, we measured the effect on cardiac output of the introduction of methylmethacrylate during hemiarthroplasty for displaced fractures of the femoral neck. We treated 20 elderly patients who were similar in age, height, weight and preoperative left ventricular function with either cemented or uncemented hemiarthroplasty. Using a transoesophageal Doppler probe, we measured cardiac output before incision and at six stages of the procedure: during the surgical approach, reaming and lavage of the femoral canal, the introduction of cement, the insertion of the prosthesis, and in reduction and closure. We found that before the cement was introduced, there was no difference in stroke volume or cardiac output (p > 0.25). Cementation produced a transient but significant reduction in cardiac output of 33% (p < 0.01) and a reduction in stroke volume of 44% (p < 0.02). The introduction of cement did not affect the heart rate or mean arterial pressure. There was no significant difference in cardiac function on insertion of the prosthesis. Standard non-invasive haemodynamic monitoring did not detect the cardiovascular changes which may account for the sudden deaths that sometimes occur during cemented hemiarthroplasty. The fall in stroke volume and cardiac output may be caused by embolism occurring during cementation, but there was no similar fall during reaming or insertion of the prosthesis.

Aged↗
PubMed2006

The cellular basis for enhanced volume-modulated cardiac output in fish hearts.

During vertebrate evolution there has been a shift in the way in which the heart varies cardiac output (the product of heart rate and stroke volume). While mammals, birds, and amphibians increase cardiac output through large increases in heart rate and only modest increases (approximately 30%) in stroke volume, fish and some reptiles use modest increases in heart rate and very large increases in stroke volume (up to 300%). The cellular mechanisms underlying these fundamentally different approaches to cardiac output modulation are unknown. We hypothesized that the divergence between volume modulation and frequency modulation lies in the response of different vertebrate myocardium to stretch. We tested this by progressively stretching individual cardiac myocytes from the fish heart while measuring sarcomere length (SL), developed tension, and intracellular Ca2+ ([Ca2+]i) transients. We show that in fish cardiac myocytes, active tension increases at SLs greater than those previously demonstrated for intact mammalian myocytes, representing a twofold increase in the functional ascending limb of the length-tension relationship. The mechanism of action is a length-dependent increase in myofilament Ca2+ sensitivity, rather than changes in the [Ca2+]i transient or actin filament length in the fish cell. The capacity for greater sarcomere extension in fish myocardium may be linked to the low resting tension that is developed during stretch. These adaptations allow the fish heart to volume modulate and thus underpin the fundamental difference between the way fish and higher vertebrates vary cardiac output.

Animals↗
PubMed1979

Measurements of cardiac output and organ blood flow in rats using 99Tcm labelled microspheres.

The cardiac output and regional blood flow have been simultaneously determined in the anesthetized rat by using the reference organ method. 99Tcm labelled dextran 15 micron microspheres were injected in the left ventricle while simultaneously an arterial reference sample was drawn at constant known rate. The values calculated regarding cardiac output agree well with previously recorded series. Regional organ blood flow in the rat is presented as ml . min-1 . g-1 tissue and values do agree with those reported by others. The results indicate that the reference organ method can be used in the rat for the study of cardiac output and regional blood flow.

Animals↗
PubMed1984

Validity of CO2-rebreathing cardiac output during rest and exercise in young adults.

To validate the CO2-rebreathing method ( Defare 's method) for estimating cardiac output in children and young adults, measurements were compared to thermodilution ( TDCO ) cardiac output in 16 subjects (age 7-19 yr) with congenital heart disease. Data were collected at rest (N = 11) and during 4-min stages of supine bicycle exercise (N = 13). Estimated arterial-venous (-v-a)CO2 content differences related linearly to the measured CO2 content difference (Y = 0. 29X + 2.47, r = 0.65, P less than 0.001). With this (v-a)CO2 difference correction for all patients (N = 16), the correlation between CO2-rebreathing cardiac output and the TDCO was r = 0.87 (SEE = +/- 1.8 l X min-1). The correlation was higher for exercise (r = 0.81) than for rest (r = 0.65). We conclude that the CO2-rebreathing method, with a (v-a)CO2 content difference adjustment, is a simple, noninvasive technique providing estimates of cardiac output in children and young adults with congenital heart disease. Individual estimates should be treated with caution, especially when used for clinical evaluations.

Adolescent↗
PubMed1999

The effects of chronic prostacyclin therapy on cardiac output and symptoms in primary pulmonary hypertension.

OBJECTIVES: This study evaluated the response to prostacyclin dose reduction in patients with primary pulmonary hypertension (PPH) who developed high cardiac outputs. BACKGROUND: Patients on prostacyclin require chronic upward dose titration to overcome tolerance to the medication. No upper limit of effective dose has been described. METHODS: We studied 12 patients with PPH treated with chronic prostacyclin therapy who presented in high cardiac output states. Each patient underwent prostacyclin dose reduction under hemodynamic guidance targeted to reduce the cardiac index to < or =4 liter/min/M2, unless rebound pulmonary hypertension occurred. Following dose reduction, patients were observed for changes in the effectiveness of the prostacyclin. RESULTS: Patients were treated for 39 +/- 20 months, resulting in a 71% reduction in pulmonary vascular resistance compared to baseline. At the time of their most recent evaluation their cardiac outputs were increased to 10.1 +/- 2.3 liter/min. The patients underwent a 39% dose reduction (range 12% to 78%) resulting in a change of mean PAP from 45 to 46 mm Hg (p = NS), cardiac index from 7.4 +/- 1.4 to 4 +/- 0.74 liter/min/M2 (p = 0.01), and pulmonary vascular resistance from 3.7 +/- 1.7 to 4.7 +/- 1.5 units (p < 0.001). In no instance did rebound pulmonary hypertension occur. However, the patients all retained their clinical benefit without a return of tolerance. CONCLUSIONS: Excessive prostacyclin in PPH can lead to a high cardiac output state, suggesting it has important positive inotropic effects. In this circumstance, reducing the dose can allow the cardiac output to return to normal without worsening the clinical state.

Adult↗
PubMed2004

Accurate, noninvasive continuous monitoring of cardiac output by whole-body electrical bioimpedance.

STUDY OBJECTIVES: Cardiac output (CO) is measured but sparingly due to limitations in its measurement technique (ie, right-heart catheterization). Yet, in recent years it has been suggested that CO may be of value in the diagnosis, risk stratification, and treatment titration of cardiac patients, especially those with congestive heart failure (CHF). We examine the use of a new noninvasive, continuous whole-body bioimpedance system (NICaS; NI Medical; Hod-Hasharon, Israel) for measuring CO. The aim of the present study was to test the validity of this noninvasive cardiac output system/monitor (NICO) in a cohort of cardiac patients. DESIGN: Prospective, double-blind comparison of the NICO and thermodilution CO determinations. PATIENTS: We enrolled 122 patients in three different groups: during cardiac catheterization (n = 40); before, during, and after coronary bypass surgery (n = 51); and while being treated for acute congestive heart failure (CHF) exacerbation (n = 31). MEASUREMENTS AND INTERVENTION: In all patients, CO measurements were obtained by two independent blinded operators. CO was measured by both techniques three times, and an average was determined for each time point. CO was measured at one time point in patients undergoing coronary catheterization; before, during, and after bypass surgery in patients undergoing coronary bypass surgery; and before and during vasodilator treatment in patients treated for acute heart failure. RESULTS: Overall, 418 paired CO measurements were obtained. The overall correlation between the NICO cardiac index (CI) and the thermodilution CI was r = 0.886, with a small bias (0.0009 +/- 0.684 L) [mean +/- 2 SD], and this finding was consistent within each group of patients. Thermodilution readings were 15% higher than NICO when CI was < 1.5 L/min/m(2), and 5% lower than NICO when CI was > 3 L/min/m(2). The NICO has also accurately detected CI changes during coronary bypass operation and vasodilator administration for acute CHF. CONCLUSION: The results of the present study indicate that whole-body bioimpedance CO measurements obtained by the NICO are accurate in rapid, noninvasive measurement and the follow-up of CO in a wide range of cardiac clinical situations.

Cardiac Catheterization↗
PubMedDate not supplied

Effects of age and isoproterenol on the cardiac output and regional blood flow in the rat.

Heart rate, stroke volume, cardiac output, its distribution and organ blood flows were measured, using the microsphere technique (15 micron in diameter microspheres), in 5, 12 and 24 months old conscious male rats. Each rat was then infused with isoproterenol (0.2 microgram/kg.min) and the measurements were repeated. It was found that resting cardiovascular values do not change within the age range studied, with the exception of the renal blood flow. After infusion of isoproterenol, the heart rate and cardiac output increased in the youngest group while only smaller increase in heart rate and no significant changes in cardiac output were found in the oldest group. Similarly, organ blood flow increased after isoproterenol in all organs studied in the 5 months group, with significance levels reached in the case of blood supply to the right and left ventricles, total heart, skin and carcass. In contrast, infusion of the same dose of isoproterenol in the 24 months old animals did not elicit any significant changes in the regional blood flow. Thus, the response to beta-adrenergic stimulation is depressed with advancing age. This finding of decreased in vivo response to beta-adrenergic stimulation may be a mechanism for the altered cardiovascular performance during stress seen in aged animals and man.

Aging↗
PubMed1990

[Comparison of cardiac output between in DDD and in VVI by pulsed Doppler echocardiographic method (correction with Swan-Ganz catheter method)].

Difference of cardiac output and stroke volume between that in DDD and that in VVI was studied by pulsed Doppler echocardiography at different pacing rates. Moreover, to evaluate the usefulness of the method by pulsed Doppler echocardiography, cardiac output by the Swan-Ganz catheter method was measured and compared. Fourteen patients age 37-83 years (mean 65 years) with sick sinus syndrome and implanted multiprogrammable dual chamber pacemakers were studied. Cardiac output was measured as the product of the echocardiographically determined cross sectional area of the aortic anulus and the Doppler-determined mean velocity of left ventricular outflow over systole. Cardiac output was greater in DDD with atrial kick than in VVI at each pacing rate, and increased with elevation of the rate, but it was smaller at 120 PPM than at 110 PPM in DDD. Stroke volume was greater in DDD than in VVI at each pacing rate, and maximum volume was at 60 PPM in both modes. The data by pulsed Doppler echocardiography and by Swan-Ganz catheter method have high correlation. Besides being related with pulse rate, these results may be related with such things as myocardial contractility, preload and afterload. For example, the tension of autonomic nervous system, the changing of venous return volume, the disease of arteriosclerosis and old myocardial infarction, temperature, blood viscosity and so on. We will continue the study considering these factors.

Adult↗