Intermittent Cardiac Output Research Articles

Derivation of Stroke Volume from Pulmonary Artery Pressures.

Intermittent cardiac output (CO) studies using thermodilution are considered the gold standard. We have developed a stroke volume (SV) calculator from pulmonary pulse pressure (PP) to allow continuous monitoring of SV and CO from PP. Hemodynamic data on 169 patients following orthotopic heart transplantation were used to compare our calculator-derived SV (and SV index, or SVi) against thermodilution-derived SV on admission into intensive care unit immediately following heart transplantation (T0) and 6h after admission (T6). The calculated SV correlated with thermodilution-derived SV T0 (r = 0.920, p < 0.001, coefficient of 0.539 and the constant of 2.06). The median calculator SV, adjusted for coefficient and constant, was 48.4ml (37.7, 60.7), comparable to the median thermodilution-derived SV 47.9ml (37.5, 61.0), p = 0.737 with acceptable agreement on Bland-Altman plots. The thermodilution-derived SVi was 28.1ml (19.7, 38.7) and adjusted calculator-derived SVi 28.9ml (19.7, 39.9), p = 0.781. At T6, median thermodilution-derived SVi was 27.7ml (19.5, 35.9) compared to the calculator-derived SVi median of 26.1ml (17.7, 37.7), p = 0.203. Changes in PP can be used to track changes in SV using this calculator. Changes in PP may be used to assess response to treatment in the early post-operative period.

Cardiac output monitoring in cirrhotic patients: EV1000 versus pulmonary artery catheter - preliminary data

The EV1000 platform, a new calibrated device for intermittent and continuous cardiac output monitoring, has recently been introduced into clinical practice [1]. This study aims to assess the level of agreement between intermittent and continuous cardiac output obtained from VolumeView (ICOvv and CCOvv) connected to the EV1000 platform (Edwards Lifesciences, Irvine, CA, USA) and intermittent (ICOvig) and continuous cardiac output (CCOvig) obtained using an advanced pulmonary artery catheter (PAC) connected to the Vigilance System (Edwards Lifesciences) in cirrhotic patients undergoing liver transplantation.

Pulse contour cardiac output monitoring is less reliable in critically ill children

Intermittent cardiac output measurement using the transpulmonary thermodilution (TPTD) method is considered to be the gold standard in young children but a validated continuous cardiac output technique is not available in these patients. We compared the continuous pulse contour cardiac output (PCCO) measurements with the TPTD method in critically ill children.

Alterações hemodinâmicas durante a revascularização do miocárdio sem utilização de circulação extracorpórea

JUSTIFICATIVA E OBJETIVOS: O posicionamento e a estabilização cardíaca durante a revascularização miocárdica sem circulação extracorpórea (CEC) podem causar alterações hemodinâmicas de acordo com o local abordado. O objetivo deste estudo foi avaliar essas alterações durante a realização das anastomoses coronarianas distais. MÉTODOS: Vinte pacientes adultos submetidos à revascularização do miocárdio sem CEC receberam monitoração com cateter de artéria pulmonar e ecodoppler transesofágico. Os dados hemodinâmicos foram coletados: (1) após ajustes volêmicos, (2) no início das anastomoses distais e (3) após 5 minutos, antes da remoção do estabilizador de parede. As coronárias tratadas foram agrupadas segundo sua localização: na parede lateral, anterior ou posterior. Realizaram-se ANOVA de duplo fator com repetição e pós-teste de Newman-Keuls. Considerou-se significativo p inferior a 0,05. RESULTADOS: Durante a revascularização do miocárdio sem CEC, a pressão de oclusão de artéria pulmonar elevou-se de 17,7 ± 6,1 para 19,2 ± 6,5 (p < 0,001) e 19,4 ± 5,9 mmHg (p < 0,001), enquanto a pressão venosa central de 13,9 ± 5,4 subiu para 14,9 ± 5,9 (p = 0,007) e 15,1 ± 6,0 mmHg (p = 0,006). O débito cardíaco intermitente sofreu redução de 4,70 ± 1,43 para 4,23 ± 1,22 (p < 0,001) e 4,26 ± 1,27 L.min-1 (p < 0,001). Houve interação grupo-tempo significativa no débito cardíaco obtido por Doppler transesofágico, que sofreu redução no grupo lateral de 4,08 ± 1,99 para 2,84 ± 1,81 (p = 0,02) e 2,86 ± 1,73 L.min-1 (p = 0,02), e no fluxo sanguíneo aórtico, de 2,85 ± 1,39 para 1,99 ± 1,26 (p = 0,02) e 2,00 ± 1,21 L.min-1 (p = 0,02). Não se observaram outras alterações hemodinâmicas durante as anastomoses. CONCLUSÕES: Houve deterioração hemodinâmica significativa durante a revascularização do miocárdio sem CEC. Com o Doppler transesofágico detectou-se redução do débito cardíaco apenas no grupo lateral.

Hemodynamic Changes during Myocardial Revascularization without Extracorporeal Circulation

Cardiac positioning and stabilization during myocardial revascularization without extracorporeal circulation (ECC) may cause hemodynamic changes dependent to the surgical site. The objective of this study was to evaluate these changes during distal coronary anastomosis. Twenty adult patients undergoing myocardial revascularization without ECC were monitored by pulmonary artery catheter and transesophageal Echo Doppler. Hemodynamic data were collected at the following times before removing the stabilizer wall: (1) after volume adjustments, (2) at the beginning of distal anastomosis, and (3) after 5 minutes. Treated coronary arteries were grouped according to their location in the lateral, anterior, or posterior wall. Two-way ANOVA with repetition and Newman-Keuls post-test were used in the analysis. A p value < 0.05 was considered statically significant. During myocardial revascularization without ECC, pulmonary artery wedge pressure showed elevation from 17.7 ± 6.1 to 19.2 ± 6.5 (p < 0.001) and 19.4 ± 5.9 mmHg (p < 0.001), while the central venous pressure went from 13.9 ± 5.4 to 14.9 ± 5.9 mmHg (p = 0.007) and 15.1 ± 6.0 mmHg (p = 0.006). Intermittent cardiac output was reduced from 4.70 ± 1.43 to 4.23 ± 1.22 (p < 0.001) and 4.26 ± 1.25 L.min(-1) (p < 0.001). According to transesophageal Doppler, a significant group-time interaction was observed in cardiac output, which was reduced in the lateral group from 4.08 ± 1.99 to 2.84 ± 1.82 (p = 0.02) and 2.86 ± 1.73 L.min(-1) (p = 0.02), and aortic blood flow, which went from 2.85 ± 1.39 to 1.99 ± 1.26 (p = 0.02) and 2.00 ± 1.21 L.min(-1) (p = 0.02). Other hemodynamic changes were not observed during anastomoses. A significant hemodynamic deterioration was observed during myocardial revascularization without ECC. Transesophageal Doppler detected a decrease in cardiac output only in the lateral group.

Uncalibrated Arterial Pulse Cardiac Output Measurements in Patients With Moderately Abnormal Left Ventricular Function

The aim of the study was to evaluate the accuracy and precision of the Vigileo/FloTrac system (Edwards Lifesciences, Irvine, CA) when compared with the intermittent cardiac output and continuous cardiac output measurements obtained from pulmonary arterial catheters in patients with moderately abnormal left ventricular function undergoing elective coronary artery bypass graft surgery. A prospective, observational study. Tertiary university hospital. Twenty patients with moderately abnormal left ventricular function undergoing coronary artery bypass graft surgery were enrolled. Data were collected before the induction of anesthesia (T1), after the induction of anesthesia (T2), before cardiopulmonary bypass with an open chest (T3), after cardiopulmonary bypass (T4), after sternal closure (T5), on intensive care unit admission (T6), and at 6 hours (T7) and 12 hours after surgery (T8). A total of 360 data measurements were collected; the mean bias between intermittent cardiac output (ICO) and arterial pressure cardiac output (APCO) was -0.50 ± 1.72 L/min, and the percentage error (PE) was 37.00%. The mean difference between CCO and APCO was -0.06 ± 1.84 L/min, and the PE was 37.80%. The correlation between ΔICO and ΔAPCO was r = 0.7; the correlation between ΔCCO and ΔAPCO was r = 0.73. In the intraoperative period, the mean bias between ICO and APCO was -0.41 ± 1.75 L/min, and the PE was 40.87%. The mean difference between CCO and APCO was -0.18 ± 1.90 L/min, and the PE was 41.48%. In the postoperative period, the mean bias between ICO and APCO was -0.56 ± 1.70 L/min, and the PE was 34.43%. The mean difference between CCO and APCO was -0.36 ± 1.76 L/min, and the PE was 34.87%. In cardiac surgical patients with moderately abnormal left ventricular function, the Vigileo/FloTrac 2nd generation software sensor device showed mild intraoperative and postoperative agreement when compared with a pulmonary arterial catheter.

Performance of Bedside Transpulmonary Thermodilution Monitoring for Goal-Directed Hemodynamic Management After Subarachnoid Hemorrhage

Early goal-directed hemodynamic therapy is of particular importance for adequate cerebral circulation of patients with vasospasm after subarachnoid hemorrhage but is often precluded by the invasiveness of established cardiac output determination using a pulmonary artery catheter. This study was undertaken to validate the usefulness of less invasive goal-directed hemodynamic monitoring by transpulmonary thermodilution technique in patients after subarachnoid hemorrhage. One hundred sixteen patients with subarachnoid hemorrhage who underwent surgical clipping within 24 hours of ictus were investigated. Validation of transpulmonary thermodilution-derived intermittent/continuous cardiac output and cardiac preload (global end diastolic volume) were compared with pulmonary artery catheter-derived reference cardiac output and pulmonary capillary wedge pressure or central venous pressure in 16 patients diagnosed with vasospasm. In a subsequent trial of 100 consecutive cases, clinical results between the new and standard management paradigms were compared. Transpulmonary thermodilution-derived intermittent cardiac output and transpulmonary thermodilution-derived continuous cardiac output showed close agreement to catheter-derived reference cardiac output with high correlation (r=0.85 and 0.77) and low percentage error (13.5% and 18.0%). Fluid responsiveness to defined volume loading was predicted better with global end diastolic volume than with pulmonary capillary wedge pressure and central venous pressure for larger receiver operating characteristic curve area. Patients receiving early goal-directed management by transpulmonary thermodilution experienced reduced frequencies of vasospasm and cardiopulmonary complications compared with those managed with standard therapy (P<0.05), whereas their functional outcomes at 3 months were not different (P=0.06). Goal-directed hemodynamic management guided by transpulmonary thermodilution appears to have a therapeutic advantage for optimizing the prognosis of patients with subarachnoid hemorrhage with vasospasm over conventional methods.

Comparison of pulmonary artery and aortic transpulmonary thermodilution for monitoring of cardiac output in patients with severe heart failure: Validation of a novel method*

Hemodynamic monitoring with the pulmonary artery catheter is frequently used in the management of severe heart failure. For measurement of cardiac output (CO), transpulmonary thermodilution (TPTD) has recently been adopted into clinical practice as an alternative to pulmonary artery thermodilution. However, no data have been published on the comparability of the two methods for patients with severely reduced left ventricular function. Our objective was to evaluate the correlation between these two methods of CO determination in patients with severe left ventricular dysfunction. Prospective observational clinical study. Cardiological intermediate care unit and medical intensive care unit of a university hospital. Twenty-nine patients with left ventricular ejection fraction <35% and symptoms of heart failure (New York Heart Association class III-IV). None. The two methods of intermittent CO measurement were compared by simultaneously recording the results of pulmonary artery thermodilution and TPTD after injection of a cold saline bolus. Measurements were performed when clinically necessary. A total of 325 data pairs were analyzed. Mean CO of both methods was 4.4 L/min with a bias of 0.45 L/min (2 SD 1.20 L/min), resulting in a percentage error of 27.3%. In patients with severely impaired left ventricular function, measurement of CO by TPTD provides valid results.

Continuous and intermittent cardiac output measurement in hyperdynamic conditions: pulmonary artery catheter vs. lithium dilution technique

Continuous and intermittent cardiac output measurement in hyperdynamic conditions: pulmonary artery catheter vs. lithium dilution technique

Arterial Pulse Cardiac Output Agreement With Thermodilution in Patients in Hyperdynamic Conditions

This study aimed to compare continuous cardiac output (CCO) obtained using the arterial pulse wave (APCO) measurement with a simultaneous measurement of the intermittent cardiac output (ICO) and CCO obtained with a pulmonary artery catheter (PAC) in liver transplant patients. A prospective, single-center evaluation. A university hospital intensive care unit. Eighteen patients after liver transplantation. Pulmonary artery catheters were placed in all patients, and ICO and CCO were determined using thermodilution. APCO measurements were made with the Vigileo System (Edwards Lifesciences, Irvine, CA). The authors obtained 126 data pairs of ICO and APCO and 864 pairs of CCO and APCO. ICO data were collected after intensive care unit admission and every 8 hours until the 48th postoperative hour. CCO and APCO data were collected every hour from admission until the 48th postoperative hour. Bias and precision were 0.95 +/- 1.41 L/min for ICO versus APCO and 1.29 +/- 1.28 L/min for CCO and APCO. Bias and precision for cardiac output (CO) data pairs less than 8 L/min were 0.32 +/- 1.14 L/min between ICO and APCO and 0.71 +/- 0.98 L/min between CCO and APCO. For CO data pairs higher than 8 L/min, bias and precision were 1.79 +/- 1.54 L/min between ICO and APCO and 2.25 +/- 1.14 L/min between CCO and APCO. APCO enables the assessment of CO with clinically acceptable bias and precision. At higher CO levels, APCO underestimates PAC measurements and it is not as reliable as thermodilution in hyperdynamic liver transplant patients.

Uncalibrated arterial pulse contour analysis in major vascular surgery

Assessment of continuous cardiac output using the arterial pulse wave (APCO) is currently available only with standard radial artery catheterization (Vigileo System, FloTrac™, Edwards Lifesciences, Irvine, CA, USA) [1,2]. Many of the studies available in the literature have compared APCO versus intermittent cardiac output (ICO) obtained with a pulmonary artery catheter (Intellicath, Edwards Lifesciences, Irvine, CA, USA) in patients undergoing cardiac surgery [3]. The aim of this study was to assess the bias and level of agreement between the APCO and ICO in patients undergoing major vascular surgery.

Continuous and intermittent cardiac output measurement in hyperdynamic conditions: pulmonary artery catheter vs. lithium dilution technique

This study aimed to assess the level of agreement of both intermittent cardiac output monitoring by the lithium dilution technique (CO(Li)) and continuous cardiac output monitoring (PulseCO(Li)) using the arterial pressure waveform with intermittent thermodilution using a pulmonary artery catheter (CO(PAC)). Prospective, single-center evaluation. University Hospital Intensive Care Unit. Patients (n=23) receiving liver transplantation. Pulmonary artery catheters were placed in all patients and CO(PAC) was determined using thermodilution. CO(Li) and PulseCO(Li) measurements were made using the LiDCO system. Data were collected after intensive care unit admission and every 8h until the 48th hour. A total of 151 CO(PAC), CO(Li) and PulseCO(Li) measurements were analysed. Bias and 95% limit of agreement were 0.11lmin(-1) and -1.84 to + 2.05 lmin(-1) for CO(PAC) vs. CO(Li) (r=0.88) resulting in an overall percentage error of 15.6%. Bias and 95% limit of agreement for CO(PAC) vs. PulseCO(Li) were 0.29 lmin(-1) and -1.87 to + 2.46 lmin(-1) (r=0.85) with a percentage error of 16.8%. Subgroup analysis revealed a percentage error of 15.7% for CO(PAC) vs. CO(Li) and 15.1% for CO(PAC) vs. PulseCO(Li) for data pairs less than 8 lmin(-1), and percentage errors of 15.5% and 18.5% respectively for data pairs higher than 8 lmin(-1). In patients with hyperdynamic circulation, intermittent and continuous CO values determined using the LiDCO system showed good agreement with those obtained by intermittent pulmonary artery thermodilution.

Validation of a continuous cardiac output measurement using arterial pressure waveforms

Intermittent bolus thermodilution cardiac output (ICO) and continuous cardiac output (CCO) measurements with pulmonary artery catheters (PAC) are the most commonly preferred methods of cardiac output (CO) measurement for guiding hemodynamic therapy in the clinical setting. A novel arterial pressure cardiac output (APCO) measurement method requires only access to a radial or femoral artery via a standard arterial catheter and does not require use of venous access or injection of a dilution medium for calibration.

Comparison of continuous, stat, and intermittent cardiac output measurements in patients undergoing minimally invasive direct coronary artery bypass surgery

Objective: To compare intermittent cardiac output (ICO) with continuous cardiac output (CCO) and stat cardiac output (SCO) measurements in patients undergoing minimally invasive direct coronary artery bypass (MIDCAB) surgery. Design: Prospective, clinical study. Setting: Single, tertiary referral center. Participants: Twenty adult patients undergoing off-pump MIDCAB surgery from January through June 2000. Interventions: Each patient had a 7.5F 5-lumen pulmonary artery thermodilution catheter (CCO catheter, Baxter Healthcare Corporation, Irvine, CA) inserted for measurement of cardiac output (CO). ICO, CCO, and SCO were compared at 10 predefined time points. Results: A total of 400 data pairs for CO were obtained. ICO values ranged from 1.8 to 8.4 L/min; CCO, 1.9 to 7.5 L/min; and SCO, 2.25 to 6.35 L/min. Correlation between ICO and CCO was significant (correlation coefficient, r = 0.78, p < 0.001), accompanied by a bias of −0.095 L/min and precision of 0.729 L/min. Similarly, the correlation between ICO and SCO was significant (r = 0.79, p < 0.001), accompanied by good accuracy (bias, 0.084 L/min) and precision (0.843 L/min). There were statistically significant decreases in mean arterial pressure, CO, cardiac index, stroke volume, stroke volume index, and left and right ventricular stroke work indices during anastomosis of the left internal mammary artery to left anterior descending artery. These parameters returned to baseline preinduction values 1 minute after completion of the anastomosis. Conclusion: Excellent correlation, accuracy, and precision were found among the 3 methods of measuring CO in patients undergoing MIDCAB surgery. Further studies are needed to assess their accuracy in multivessel off-pump coronary artery bypass graft surgery and in patients with poor left ventricular function.

Continuous and intermittent cardiac output measurement: pulmonary artery catheter versus aortic transpulmonary technique

Cardiac output (CO) can be measured intermittently by bolus thermodilution methods in the pulmonary artery (COpa) or in the aorta (COart). A continuous thermodilution method (CCO) and a method for continuous estimation using the arterial pulse wave (PCCO) are also available. We compared two methods of intermittent CO measurements in patients during liver transplantation: COpa, regarded as the current clinical standard, and an aortic transpulmonary thermodilution technique (COart) performed with the PiCCO system. We also compared CCO and PCCO. Measurements were made in 62 patients at three stages: after the induction of anaesthesia, after caval clamping phase, and at the end of surgery. We used Bland-Altman and correlation analysis. We found close agreement between the techniques. Mean bias between COart and COpa and PCCO and CCO was 0.15 (2SD of differences between methods=1.74) litre min(-1) and -0.03 (1.75) litre min(-1), respectively. Mean bias between CCO and COpa and PCCO and COpa was 0.02 (1.48) litre min(-1) and 0.04 (1.69) litre min(-1), respectively. Measurement with the aortic transpulmonary thermodilution technique gives continuous and intermittent values that agree with the pulmonary thermodilution method.

Continuous and intermittent cardiac output measurement: pulmonary artery catheter vs aortic transpulmonary technique

We compared two methods of intermittent cardiac output measurements: pulmonary artery catheter (COpa) (Vigilance system SvO2/CCO, Baxter Edwards Laboratories, Irvine, CA, USA), regarded as the current clinical standard, and an aortic transpulmonary thermodilution technique (COart) performed with the PiCCO System (Pulsion Medical System, Munich, Germany), and also compared the continuous thermodilution technique (CCO), the continuous pulse contour analysis cardiac output (PCCO) versus COpa in patients during lung transplantation.

Comparison of continuous with intermittent bolus thermodilution cardiac output measurements

Few complete studies have been published to validate the agreement between continuous cardiac output and intermittent thermodilution cardiac output. To analyze the agreement between cardiac output measurements by the continuous thermodilution method and the intermittent bolus thermodilution method, using a continuous cardiac output catheter in postoperative cardiothoracic surgery patients. A convenience sample of 14 adult cardiothoracic surgical patients with thermodilution pulmonary artery catheters placed preoperatively was used. A total of 214 comparison measurements of cardiac output by both the continuous and intermittent thermodilution methods were taken on patient admission to the critical care unit, every 4 hours, and with any change greater than 10% from baseline readings. The intraclass correlation between continuous cardiac output and intermittent cardiac output was .89. The limits of agreement were -1.34 to 1.18 L/min, indicating that in 95% of readings the difference between continuous cardiac output and intermittent cardiac output were within this range. The continuous cardiac output monitoring method shows clinically acceptable agreement with the intermittent cardiac output method.

Continuous versus intermittent cardiac output measurement in cardiac surgical patients undergoing hypothermic cardiopulmonary bypass

Continuous thermodilution cardiac output (CCO) measurement was clinically evaluated in patients who underwent coronary revascularization using hypothermic low-flow, low-pressure cardiopulmonary bypass (CPB). Prospective study. University hospital setting. 30 cardiac surgical patients. CCO was correlated to standard bolus thermodilution cardiac output (ICO) obtained at end-expiration. Measurements were taken at selected time points (n = 18) before anesthesia induction, before CPB, and 5 minutes to 12 hours after CPB. A total of 540 data pairs were thus obtained. ICO ranged from 1.9 to 9.9 L/min, CCO from 1.5 to 9.9 L/min. Correlation between ICO and CCO was highly significant (r = 0.872; p < 0.01), accompanied by an excellent accuracy (bias -0.0213 L) and precision (0.59 L) before CPB and more than 45 minutes after CPB. However, during the first 45 minutes after CPB, there was no correlation (r = 0.273) between ICO and CCO, and ICO tended to be relatively high, whereas CCO measurements showed relatively low values. During the first 45 minutes after hypothermic CPB, but not during the ensuing time period, central blood temperature decreased, which may be interpreted as a lack of thermal equilibration between central and peripheral compartments. It is hypothesized that thermal instability in combination with increased respiratory variations in pulmonary artery blood temperature caused inhomogenous rewarming of different body sites and might be the main reason for the lack of correlation between ICO and CCO. Despite an excellent correlation, accuracy, and precision between CCO and ICO before CPB and more than 45 minutes after hypothermic CPB, a lack of correlation in the early phase after CPB has been found. Further investigation is needed to elucidate the underlying cause of these findings and to clarify whether ICO or CCO or both fail to represent the real cardiac output up to 45 minutes after weaning from hypothermic CPB.

Severity of hypoxia predicts response to nitric oxide in a porcine pulmonary hypertension model

Although inhaled nitric oxide (NO) has been variably successful in resolving pulmonary hypertension in neonates, children, and adults, no parameters predictive of response to this therapy have been elucidated. We conducted an animal study to determine if severity of hypoxia can predict magnitude and sustenance of response to inhaled NO therapy. Seven Yorkshire swine weighing 11 to 20 kg underwent 16 experiments, each consisting of four phases: Phase 1: Control period of ventilation on F io 2 .3; phase 2: Hypoxic period on F io 2 .10 to .15, establishing pulmonary hypertension; phase 3: Treatment period with NO starting at five parts per million (ppm), doubling dose every 10 min to 80 ppm; phase 4: Posttreatment observation period after discontinuation of NO while maintaining hypoxia for 1 hour or until circulatory failure or pulmonary hypertension of pre-NO magnitude developed. Each animal underwent a maximum of three experiments in random order of hypoxia severity before sacrifice with pentobarbital overdose. Continuous hemodynamic parameters, intermittent cardiac output and pulmonary capillary wedge pressure, and intermittent arterial blood gas analyses were obtained through pulmonary and systemic artery catheters placed by femoral cutdown. Pulmonary and systemic vascular resistances (PVR and SVR) were calculated by standard formulas. Experiments were divided into two groups (n = 8 in each): group 1 with severe hypoxia (Pa o 2, 25 to 35) and group 2 with moderate hypoxia (Pa o 2, 36 to 65). Data for all hemodynamic parameters were expressed as mean percentage change from baseline (phase 1) ± SEM under each set of conditions, and the two groups were compared by two-way analysis of variance and covariance adjusted for order of experimentation. The severely hypoxic group showed significantly less improvement than the moderately hypoxic group in mean pulmonary artery pressure during treatment with NO (17 ± 3% versus −2 ± 3%, P = .005) and after discontinuing the drug (55 ± 11% versus 21 ± 7%, P = .03). The severely hypoxic group also experienced a significant elevation in cardiac output during NO therapy when compared with the moderately hypoxic group (26 ± 6% versus 3 ± 4%, P = .02). Furthermore, there were no incidents of circulatory failure after discontinuing NO during moderate hypoxia versus three incidents (38%) during severe hypoxia, all of which were immediately reversed by restarting NO. In a porcine hypoxic pulmonary hypertension model, severe hypoxia predicts weaker improvement in the pulmonary hypertension during NO therapy and stronger recurrence after discontinuing the drug. Nitric oxide may also have a hemodynamic supportive role during severe hypoxia by enhancing cardiac output and preventing acute cor pulmonale.

Is continuous cardiac output measurement using thermodilution reliable in the critically ill patient?

Objective: Evaluation of continuous cardiac output monitoring based on the thermodilution technique in the critically ill. Design: Prospective clinical investigation. Setting: A surgical intensive care unit of a university hospital. Patients: Thirty-five critically ill patients (trauma and/or sepsis patients), who needed pulmonary artery catheterization. The patients were prospectively studied according to the following groups: a) patients with a heart rate of >120 beats/min; b) those patients with a cardiac output of >10 L/min; c) patients with a cardiac output of <4.5 L/min; d) patients with a rectal temperature of >39.0°C; and e) patients with a pulmonary artery catheter inserted for >4 days. Interventions: Therapies were carried out according to modern intensive care medicine protocols by physicians who were not involved in the study. Measurements: Cardiac output was monitored continuously using a new, modified pulmonary artery catheter. This catheter has a heating filament by which energy is transmitted to the circulating blood (modified thermodilution technique). A bedside microprocessor calculated cardiac output using a new algorithm. Standard bolus thermodilution technique (10 mL of ice-cold saline solution) was used to compare the continuous cardiac output measurement with the intermittent bolus cardiac output measurement. Main Results: A total of 404 pairs of intermittent (bolus) cardiac output and continuous cardiac output measurements were obtained from the 35 patients. The bias (mean difference between bolus cardiac output measurement and continuous cardiac output measurement) of all measurements was 0.03 ± 0.52 L/min and the 95% confidence limit (mean difference ± 2 sd) was -1.01/1.06 L/min. Also, continuous cardiac output measurement agreed closely with bolus cardiac output measurement (bias was 0.16 ± 0.57 L/min in the cardiac output of >10 L/min group; bias was -0.17 ± 0.50 L/min for the cardiac output of <4.5 L/min group). Increased temperature and prolonged length of stay did not influence the agreement of continuous cardiac output measurement with bolus cardiac output measurement (bias was 0.09 ± 0.51 L/min in the >39°C rectal temperature group). Conclusions: Continuous monitoring of cardiac output using a modified pulmonary artery catheter with a heated filament has proven to be accurate and precise in the critically ill patient when compared with the “standard” intermittent bolus thermodilution technique. The continuous monitoring technique enhances our armamentarium for more intensive monitoring of these patients under a variety of circumstances. (Crit Care Med 1994; 22:1913–1918)