Pharmacokinetic-based total intravenous anaesthesia using remifentanil and propofol for surgical myocardial revascularization.

BACKGROUND AND OBJECTIVE: We investigated the following aspects of pharmacokinetic-guided total intravenous anaesthesia with remifentanil and propofol in patients undergoing surgical myocardial revascularization: anaesthetic efficacy, haemodynamic effects, impact on extubation of the trachea and analgesia after operation. METHODS: Thirty-two patients undergoing on-pump coronary bypass surgery received intravenous anaesthesia with remifentanil and propofol. Both drugs were dosed and titrated based on computer-assisted pharmacokinetic models to maintain constant plasma concentrations. The propofol target plasma concentration was 1.2 microg mL(-1) throughout the procedure. A remifentanil target plasma concentration of 8 ng mL(-1) was achieved over 2 min for induction. After tracheal intubation, the opioid plasma concentration was reduced to 4 ng mL(-1), and then titrated up to 8 ng mL(-1) during surgery. Postoperative analgesia was managed with remifentanil infusion until 4 h after tracheal extubation, and a continuous infusion of tramadol was started 1 h before the remifentanil was stopped. RESULTS: After induction of anaesthesia, heart rate (-20%) and cardiac index (-6%) decreased significantly. No hypotensive episodes (mean arterial pressure < 60 mmHg) occurred. Intraoperative haemodynamics were stable. Three cases of myocardial ischaemia were detected: two by transoesophageal echocardiography and one with ST-segment monitoring. The duration of postoperative mechanical ventilation of the lungs was 95 +/- 13 min and the time to extubation was 150 +/- 18 min. Postoperative analgesia was satisfactory in all patients. CONCLUSIONS: Pharmacokinetic-based total intravenous anaesthesia with remifentanil and propofol provides adequate anaesthesia during coronary surgery with cardiopulmonary bypass and allows safe early extubation after operation.

Automated protamine dose assay in heparin reversal management after cardiopulmonary by pass.

BACKGROUND: To evaluate the impact of automated Protamine Dose Assay (PDA) performed with Hemochron 8000 (International Technodyne Company, Edison, NJ) on the management of heparin reversal after cardiopulmonary bypass (CPB). PDA was compared with empirical protamine to heparin ratio with regard to calculation of the protamine dose, and the sensitivity of PDA and ACT to residual circulating heparin after protamine administration was investigated too. DESIGN: prospective and randomized study. SETTING: cardiac surgical center of a General Hospital. PARTICIPANTS: 50 patients undergoing elective cardiac surgery with CPB. INTERVENTIONS: after CPB patients randomly received protamine according to our standard empirical ratio of 1 mg. protamine/100 U. heparin (group S, 24 patients), or to PDA result (group T, 26 patients) based on protamine titration method of determining circulating heparin. After protamine administration ACT and PDA were performed to assess heparin reversal and detect residual circulating heparin. Based on the PDA result, additional protamine was administered in both groups when required. MEASUREMENTS: in both groups basal and post-heparin ACT values, protamine doses, ACT and PDA after protamine administration were measured. RESULTS: The protamine dose was significantly lower (30%) in patients treated according to PDA. In 20% of patients showing normal ACT PDA revealed still circulating heparin, and additional protamine was required. In all other cases ACT and PDA both confirmed heparin reversal. CONCLUSIONS: PDA allowed us to administer a significantly lower amount of protamine. This can reduce incidence of adverse effects of over- and under-infusion of protamine. PDA also proved to be more sensitive than ACT in detecting residual circulating heparin after protamine administration.

Influence of transesophageal echocardiography on intraoperative decision making for toronto stentless prosthetic valve implantation.

BACKGROUND AND AIM OF THE STUDY: Intraoperative transesophageal echocardiography (TEE) is commonly used during aortic valve surgery. In aortic valve replacement (AVR), this permits measurement of the aortic annulus, study of the anatomy of aortic valve components, and prediction of prosthesis valve size. After cardiopulmonary bypass (CPB), echocardiography is valuable in checking prosthesis function. In this study, we evaluated the impact of intraoperative TEE on the decision-making process of aortic Toronto stentless prosthetic valve (TSPV) implantation. METHODS: Fifty-two consecutive patients undergoing elective AVR were collected prospectively. Multiplane TEE was performed before CPB to determine diameters of the aortic valve annulus and sinotubular junction. This was to evaluate the feasibility of TSPV implantation in the aortic position and to predict prosthesis size. Further TEE evaluation was carried out after CPB to assess prosthetic valve function. RESULTS: TEE allowed measurement of the aortic annulus and sinotubular junction, and enabled correct prediction of prosthesis size. Ultrasonic evaluation also revealed contraindications to TSPV implantation in five patients. In one case, color-Doppler examination led to immediate successful surgical correction of prosthetic incompetence. CONCLUSION: Intraoperative multiplane TEE examination is useful in the decision-making process in AVR with the TSPV by selecting patients suitable for the stentless valve, predicting prosthesis size, and checking prosthesis function.