The influence of propofol and midazolam/halothane anesthesia on hepatic SvO2 and gastric mucosal pH during cardiopulmonary bypass.

OBJECTIVE: Because propofol is known to reduce vascular resistance, the objective of this study was to compare the indices of hepatosplanchnic circulation and oxygenation during cardiopulmonary bypass (CPB) in patients anesthetized with either propofol or midazolam/halothane. DESIGN: A prospective, randomized, nonblinded study. SETTING: A university hospital. PARTICIPANTS: Twenty patients undergoing cardiac surgery with CPB. INTERVENTIONS: Nine patients were anesthetized with propofol/fentanyl/pancuronium and 11 patients were anesthetized with midazolam/halothane/fentanyl/pancuronium. All patients had a nasogastric tonometer tube and two fiberoptic thermodilution catheters inserted; one in the pulmonary artery and one in the upper right hepatic vein. During bypass, SvO2s were measured from the venous line of the heart-lung machine. MEASUREMENTS AND MAIN RESULTS: Gastric mucosal pH (pHi) was measured prebypass, 30 minutes after the start of CPB, and just before weaning off CPB. Hepatic SvO2 (HSvO2) values were recorded every 5 minutes. The pH gap was less at 30 minutes of hypothermic CPB in the propofol group. In the midazolam/halothane group, the HSvO2 decreased after the start of rewarming, whereas in the propofol group the values remained almost at the prebypass levels. At the end of rewarming, the HSvO2 was almost identical in the two groups. CONCLUSION: Propofol preserved the HSvO2 during CPB and produced a more optimal relationship between the hepatosplanchnic blood flow and oxygen consumption.

Perioperative metoprolol reduces the frequency of atrial fibrillation after thoracotomy for lung resection.

OBJECTIVE: The association of atrial fibrillation with thoracic surgical procedures is well known, but nevertheless its cause is not well defined. Increased sympathetic activity may play a role in the development of atrial fibrillation, and reduced beta-receptor activity may be advantageous. The objective was to evaluate the effect of oral beta-blockade on the frequency of atrial fibrillation and to evaluate some possible causative factors. DESIGN AND SETTING: The study was prospective, randomized, and double-blind, and was conducted at Aarhus University Hospital. PARTICIPANTS: Thirty patients without previous or present cardiovascular history undergoing elective thoracotomy for lung resection. INTERVENTIONS: The patients received either 100 mg of metoprolol or placebo orally before surgery and once daily postoperatively. Anesthesia consisted of a thoracic epidural block combined with general intravenous anesthesia. Epidural morphine was continued postoperatively. MEASUREMENTS AND MAIN RESULTS: Patients were monitored with electrocardiograms (ECGs), capillary pulse oximetry, invasive hemodynamic monitoring, central venous oxygen saturation, arterial blood gases, serum electrolytes, and fluid balances. Atrial fibrillation developed in 23.3% of the patients, 6.7% after metoprolol compared with 40% in the placebo group. Atrial fibrillation developed a mean of 2.9 days postoperatively. The predominant hemodynamic findings were perioperative lower oxygen consumption and postoperative lower cardiac index after metoprolol. Patients developing atrial fibrillation had much higher oxygen consumption and postoperative cardiac index than other patients. CONCLUSION: Perioperative oral beta-blockade can reduce the frequency of atrial fibrillation without serious side effects. Increased sympathetic activity is one of the predominant factors in the cause of this complication.

[Continuous measurements of cardiac output in the perioperative period]. / Kontinuerlig måling af hjertets minutvolumen i den perioperative periode.

Management of critically ill patients is based on knowledge of fundamental physiological variables. Automatized and continuous measurement of these variables is preferable. A new system based upon the thermodilution method has been developed to measure cardiac output automatically and continuously. We evaluated the system in the potentially unstable perioperative period with possible great and rapid changes in cardiac output. Twenty patients, scheduled for open heart or abdominal aortic aneurysm surgery, were included into the study, which was approved by the local ethical committee. The patients were monitored for up to 30 hours. At random intervals five iced bolus thermodilution cardiac output (BCO) determinations were made and compared to the continuous measurements (CCO). Two hundred and thirty-one pairs of data were obtained. The cardiac outputs ranged from 2.5-14.9 l/min. The absolute bias was 0.31 l/min (95% limits of agreement -1.4 l/min to 2.0 l/min). The mean relative error was 4.7% with a standard deviation of the relative error of 15.4%. The linear regression was represented by: CCO = 11.352 x BCO - 0.36. The correlation coefficient R was 0.90 (p < 0.001). In conclusion, the CCO measurement technique is a promising clinical method. The method is straightforward, requires no calibration, is independent of vascular geometry and measures with its limitations volumetric flow. Finally automatic and continuous patient monitoring provides more information and has potential to reveal previously undetected haemodynamic events.

Continuous cardiac output measurements in the perioperative period.

Management of critically ill patients is based on knowledge of fundamental physiologic variables. Automatized and continuous measurement of these variables is preferable. A new system based upon the thermodilution method has been developed to measure cardiac output automatically and continuously. We evaluated the system in the potentially unstable perioperative period with possible great and rapid changes in cardiac output. Twenty patients, scheduled for open heart or abdominal aortic aneurysm surgery, were included in the study, which was approved by the local ethical committee. The patients were monitored up to 30 hours. At random intervals five, iced, bolus thermodilution cardiac output (BCO) determinations were made and compared to the continuous cardiac output measurements (CCO). Two hundred and thirty-one pairs of data were obtained. The cardiac outputs ranged from 2.5-14.9 l.min-1. The absolute bias was 0.31 l.min-1 (95% limits of agreement -14 l.min-1 to 2.0 l.min-1). The mean relative error was 4.7% with a standard deviation of the relative error of 15.4%. The linear regression was represented by: CCO = 1,1352.BCO-0.36. The correlation coefficient R was 0.90 (P < 0.001). In conclusion, the CCO measurement technique is a promising clinical method. The method is straightforward, requires no calibration, is independent of vascular geometry and measures with its limitations volumetric flow. Finally automatic and continuous patient monitoring provides more information and has potential to reveal previously undetected haemodynamic events.