[Comparison between continuous and intermittent thermodilution measurement of cardiac output during coronary artery bypass operation]. / Vergleich zwischen kontinuierlicher und intermittierender Thermodilutionsmessung des Herzzeitvolumens während koronarer Bypass-Operation.

PURPOSE OF THE STUDY: Continuous recording of cardiovascular parameters ranks high in cardioanaesthesia. Various methods to measure the cardiac output have been developed within a period of a few years. We compared the bolus thermodilution method (COI), which has been internationally adopted as "gold standard" method, with the continuous thermodilution method (CCO) for measuring the cardiac output by means of the CCO Vigilance Monitor. Our aim was to find out whether cardiac output can be determined with valid results during coronary artery bypass surgery when using CCO. METHOD: A flow-directed catheter was used (8 Fr. Intelli-Cath CCO PA) in 98 patients during coronary artery bypass surgery after initiation of anaesthesia, introducing the catheter via the right V.jugularis interna, for continuous measurement of the cardiac output via the CCO Vigilance Monitor. The same equipment was also used to measure the cardiac output via the bolus thermodilution method (COI mode) at the following stages: after abandoning the CCO mode 10 minutes subsequent to beginning the operation before sternotomy; 10 minutes after sternotomy before connecting to the heart-lung machine; 15 minutes after disconnecting the heart-lung machine before closing the thorax; and 10 minutes after closing the thorax. As a corresponding comparative value of the CCO method, we used the average cardiac output value calculated for each of the four times of measurement for the last three minutes before applying the boli. RESULTS: In regression analysis we chose the linear model CCO = b x COI with gradient b = 1 and zero point ordinate a = 0. The identity measures, Spearman's rank correlation coefficients, and linear regression coefficients calculated for the four times of measurement, showed good agreement. Scatter of the paired differences between both methods (CCO-CCI) did not have any deterministic structure at all times of measurement. The average bias at the 4 times of measurement was 0.10 l/min, -0.12 l/min, -0.1 l/min, and -0.03 l/min, respectively, with a precision = 2 x s of 1.17 l/min, 1.36 l/min, 1.69 l/min and 1.50 l/min, respectively. The average relative error (100 x [CCO-COI]/COI) with standard deviation was calculated for the 4 times of measurement as 3.2% (s = 15.4%), -1.6% (s = 15.3%), -0.9% (s = 13.9%) and -0.3% (s = 12.0%), respectively. CONCLUSIONS: Literature references show that the continuous thermodilution method is not only valid for intensive-care long-term measurement of cardiac output with approximately stationary haemodynamics, but also-as our results prove-valid if haemodynamics are not usually stationary, such as during coronary artery bypass surgery. The pros of the continuous thermodilution method are that no additional equipment is required apart from the standard equipment used in intensive-care medicine and cardio-anaesthesiology: that there is no stress caused by volume; and that manipulation is safe because no calibration routine is needed and also because measurement and analysis techniques are fully automated. Hence, we are of the opinion that the intraoperative use of this cardiac output measurement technique during open heart surgery is clinically indicated.

Tussive effect of a fentanyl bolus administered through a central venous catheter.

One hundred and ten male patients scheduled for coronary artery bypass grafting were allocated randomly into one of three groups. Patients in group A received fentanyl 7 micrograms/kg via a central venous catheter, those in group B were given fentanyl 7 micrograms/kg through a peripheral venous cannula, and patients in group C received sterile water via a central venous catheter. In group A, 45.9% of patients coughed after injection of fentanyl; the mean onset time from the end of fentanyl administration to the beginning of coughing was 10.6 seconds. Only one patient in group B and no patient in the control group exhibited a cough response (p less than 0.0001). We hypothesise that fentanyl can evoke the pulmonary chemoreflex.

Clonidine as a sedative adjunct in intensive care.

A 63-year-old man underwent distal oesophagectomy and proximal gastrectomy. Postoperatively, controlled ventilation was necessary for 53 days because of anastomotic leakage. Multiple sedative regimens proved to be inadequate. By contrast, a fentanyl-midazolam combination with continuous supplementation of clonidine 0.014 micrograms kg-1 min-1 (1.44 mg 70 kg-1 24 h-1) was very effective in terms of sedation and pain relief. During combined fentanyl-midazolam and clonidine infusion, cardiovascular depression gradually developed over several days necessitating the institution of a dobutamine infusion (dose: 8-12 micrograms kg-1 min-1). Four attempts of abrupt clonidine withdrawal were followed by sympathetic overshoot reactions consisting of tachycardia, hypertension, agitation, and sweating. Discontinuation of clonidine was finally possible after a 12-day weaning period.