Continuous cardiac output measurements do not agree with conventional bolus thermodilution cardiac output determination

PURPOSE

To evaluate the performance of two different continuous cardiac output monitoring systems based on the thermodilution principle in critically ill patients.

METHODS

Nineteen cardiac surgical patients were randomly assigned to continuous cardiac output monitoring using one of the two systems under study (group I, IntelliCath(TM) catheter, n=9; group II, Opti-Q(TM) catheter, n=10). Each patient was studied over a period of three hours. Conventional bolus thermodilution cardiac output measurements were carried out every 15 min leading to 13 measurements in each patient. The continuous cardiac output values were compared with the bolus thermodilution measurements. Bias (mean difference between continuous and bolus thermodilution) and precision (SD of differences) were calculated as a measure of agreement between the respective continuous method and conventional bolus thermodilution.

RESULTS

The range of measured cardiac outputs was 3.8-15.4 L*min(-1) (IntelliCath(TM)) and 3.5-8.3 L*min(-1) (OptiQ(TM)). Bias and precision was 0.06 +/- 0.76 L*min(-1) (IntelliCath(TM)) and -0.04 +/- 0.74 L*min(-1) (OptiQ(TM)), respectively. There was no difference in bias between the two systems (P=0.38). +/- 2 SD of the differences (i.e., 95% of the differences) did not fall within the predetermined limits of agreement of +/- 0.5 L*min(-1).

CONCLUSIONS

There was no difference between the two systems regarding the agreement with conventional bolus thermodilution as the standard. A discrepancy between bolus and continuous thermodilution cardiac output measurement techniques above the clinically acceptable limits suggest that they are not interchangeable.

Beat-to-beat measurement of cardiac output by intravascular pulse contour analysis: a prospective criterion standard study in patients after cardiac surgery

OBJECTIVE

To evaluate the accuracy of a new pulse contour method of measuring cardiac output in critically ill patients.

DESIGN

A prospective criterion standard study.

SETTING

Cardiac surgery intensive care unit in a university hospital.

PARTICIPANTS

Nineteen cardiac surgery patients requiring intensive care treatment with pulmonary artery catheters after surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The pulse contour cardiac output monitor uses transpulmonary bolus thermodilution measurements to calibrate the system. In each patient, the pulse contour cardiac output values were compared with conventional thermodilution. The method described by Bland and Altman and linear regression analysis were used for comparison. The mean difference (bias) +/- standard deviation of differences (precision) was 0.31 +/- 1.25 L/min for pulmonary bolus thermodilution cardiac output versus pulse contour cardiac output and 0.21 +/- 0.73 L/min for pulmonary bolus thermodilution cardiac output versus transpulmonary bolus thermodilution cardiac output. Linear regression (correlation) analyses were pulse contour cardiac output = 0.97 thermodilution + 0.53 (r = 0.88), and transpulmonary cardiac output = 0.87 thermodilution + 1.09 (r = 0.96). There was a small increase 60 minutes after recalibration but not a statistically significant difference between pulse contour cardiac output and pulmonary bolus thermodilution cardiac output (p = 0.52).

CONCLUSIONS

Bias and precision are acceptable, and the system provides results that agree with conventional thermodilution. This study demonstrates the clinical applicability of the pulse contour cardiac output monitoring system.

Procalcitonin as a marker of systemic inflammation after conventional or minimally invasive coronary artery bypass grafting

Cardiac surgery using cardiopulmonary bypass (CPB) often induces a systemic inflammatory response syndrome (SIRS). The concept of minimally invasive direct coronary artery bypass (MIDCAB) eliminates cardiopulmonary bypass. We evaluated the perioperative time course of procalcitonin (PCT) to compare the inflammatory response due to these two different surgical procedures. 57 patients were studied: CABG with CPB (n = 30), MIDCAB without CPB (n = 27). The following data were measured preoperatively, after induction of anesthesia, after separation from CPB in the CABG group or after left internal mammary artery (LIMA)-to-left anterior descending artery (LAD) anastomosis in MIDCAB group, and every 3 hours for the first 42 hours in the ICU: PCT, C-reactive protein (CRP), body temperature, hemodynamic parameters, and the need for catecholamines. Leucocyte counts were measured daily. For statistical analyses the Friedmann, Wilcoxon, or Mann-Whitney U tests were used. PCT in the CABG group rose to a maximum of 2.0 ng/ml (median) at 15 hrs postoperatively. In the MIDCAB group maximal PCT concentration was 0.7ng/ml (median) (p < 0.05). CRP was elevated to 17.1 mg/dl in the CABG and 18.5mg/dl in the MIDCAB group (n.s.). The leucocyte counts were increased on day 2 in the CABG group (p < 0.05). In the CABG group about 25% of the patients needed noradrenaline, but in the MIDCAB group none (p < 0.05). Body temperature did not differ between both groups. The increase in PCT concentration was more pronounced after CABG, indicating a reduced inflammatory response after MIDCAB. CRP was increased after both procedures. PCT reflects the inflammatory response after cardiac bypass surgery with or without CPB.

[A comparative study of intravenous opioid analgesia. Sufentanil and alfentanil for extracorporeal shock-wave lithotripsy in urologic patients]

Extracorporeal shock-wave lithotripsy (ESWL) is the method of choice for the treatment of solitary stones in the kidney or ureter. Early lithotripters required prolonged immobility of the patient and caused considerable pain, necessitating general or epidural anaesthesia during the procedure. Modern lithotripters are quicker, but still require analgesia. Intravenous opioids are currently the drugs in favour. The opioids most commonly used are fentanyl and its shorter-acting analogue, alfentanil. The latter has a more rapid onset and, because of its reduced lipid solubility, is less cumulative. Sufentanil is a new opioid that is also of the phenylpiperidone group and has been recently licensed and introduced in Germany. Its pharmacokinetic and pharmacodynamic properties suggest an intermediate duration of action, high analgesic potency, and cardiovascular stability with diminished respiratory depression. In this prospective double-blind study, the effects of alfentanil and sufentanil on cardiovascular and respiratory parameters, the quality of analgesia, degree of sedation and the number and type of side-effects were compared.

PATIENTS AND METHODS

After giving informed consent and with the approval of the hospital ethics committee, 62 patients (ASA I or II) were investigated. They were randomly allocated to two groups, either receiving sufentanil (n = 32) or alfentanil (n = 30) during ESWL. No premedication was given. Excluded were patients with pain prior to treatment, patients treated with a spasmolytic or analgesic drug and those who had undergone ESWL within the last 6 months. The loading dose was given as a 5-min infusion to each group. The heart rate, systolic and diastolic blood pressure, percutaneous oxygen saturation (SpO2), and the transcutaneous capillary carbon dioxide tension (PicCO2) were recorded prior to the procedure (i.e. before administration of opioid), after 1000 and after 2000 shock waves and then 1 and 2 h after the end of lithotripsy. After 1000 and 2000 shock waves, and 1 an 2 h after the treatment, the patients were asked to express their degree of tiredness and pain on a visual analogue scale (VAS). The occurrence of side-effects such as nausea, vomiting, pruritus or other unpleasant sensations were noted by an anaesthesia nurse. Simultaneously, the anaesthetist recorded his/her impression of the patient's tiredness and degree of pain, both by using the VAS. He was not allowed to question the patient, nor was he aware of the patient's own scores. At the end of the observation period both the patient and the anaesthetist related their overall satisfaction with the anaesthetic procedure, again by using the VAS. Data were analysed with the Mann-Whitney-U for comparisons between groups and with the Wilcoxon test within each group. The side-effects were analysed with the Chi-square test.

RESULTS

The systolic and diastolic blood pressure remained stable in both groups during and after treatment. The mean heart rate was different between the two groups at the beginning, and after the end of the treatment it dropped in both groups, but no significant difference was seen between groups. The PicCO2 rose from an initial mean of 36.8 mm Hg to a maximum of 44.6 mm Hg after 1000 shock waves in the sufentanil group, and from 37.8 mm Hg to 46.0 mm Hg after 2000 shock waves in the alfentanil group. The differences were significant within groups until 1 h after the end of the treatment, but there was no significant difference between groups. The oxygen saturation SpO2 dropped slightly in both groups. The differences were not significant between groups. In the alfentanil group, one patient had a maximum carbon dioxide tension of 83 mm Hg after 2000 shock waves, whereas in the sufentanil treated group the oxygen saturation fell to 72% in one case. (ABSTRACT TRUNCATED)