Evaluation of the Paratrend 7 Intravascular Blood Gas Monitor During Cardiac Surgery: Comparison With the C4000 In-Line Blood Gas Monitor During Cardiopulmonary Bypass Balasubramanian Venkatesh, MB BS, MD, FFARCSI, FRCA, EDICM, Thomas H. Clutton-Brock, MB BCh, MRCP, FRCA, and Stuart P. Hendry, BSc, PhD Objective: To evaluate the performance of the Paratrend 7 intrbvascular blood gas monitor (Biomedical Sensors, High Wycombe, UK, Ltd) during cardiac surgery and compare it with that of an in-line blood gas monitor placed in the arterial limb of an extracorporeal circuit during cardiopulmonary bypass. Design: A prospective study. Consecutive patient enrol- ment. Setting: In the cardiac surgical intensive care units at a tertiary referral center. Intervention: Insertion of the Paratrend 7 intravascular sensor through the radial arterial catheter after induction of anesthesia. Measurements and Main Results: Simultaneous measure- ments of pH, PCO2, and POz were made from the sensor and the blood gas analyzer, and the bias and precision were calculated on all the measured parameters. The bias and precision of the intravascular sensor during bypass for pH, PCO2, and PO2 were 0.01 and 0.06 pH units, 0.5 and 2.5 mmHg (2% and 8%), and 3 and 45 torr (0.5% and 14%), respectively. The bias and precision for the prebypass and the postbypass phases were comparable. The bias and precision of the extracorporeal monitor for pH, PCO2, and PO2 were 0.04 and 0.1 pH units, -0.3 and 4 mmHg (-1% and 15%) and 8 and 48 mmHg (4 and 18%), respectively. There were no instances of any complications attributable to the intravascular sensor. Conclusions: The intravascular sensor used in this study functioned well during cardiopulmonary bypass and the postbypass phase. The performance of the intravascular sensor was better than the in-line blood gas monitor during cardiopulmonary bypass. Copyright © 1995 by W.B. Saunders Company KEY WORDS: anesthesia, bias, blood gas monitoring, clinical measurement, electrode B LOOD GAS momtorlng plays a vital role in the management of patients undergoing anesthesia for cardiac surgery and during cardiopulmonary bypass (CPB). At the present time, intermittent blood gas measurement is the standard method of monitoring ventilation, acid-base status, and gas exchange during cardiac anesthesia and cardiac surgery. Pulse oximetry is not rehable during CPB because of the lack of a pulsatile circulation and may continue to be unreliable in the postoperative period owing to poor peripheral circulation. 1,z The advantages of continuous blood gas monitoring during cardiac anesthesia and CPB include earlier detec- tion of deleterious changes in blood gas chemistry, more effective management of acid-base and oxygen status, and reduced exposure of personnel to potentially infected blood. There are few studies on continuous blood gas monitoring during CPB, 3,4 and these trials have used blood gas sensors placed in the extracorporeal circulation rather than intravascular placement. Intra-arterial blood gas sensors have been evaluated in clinical trials before, and varying degrees of agreement with blood gas analyzers have been reported by different investi- gators. 5-8 One such device is the Paratrend 7 (Biomedical From the Umversay Department of Anaesthesta and Intenstve Care, Queen Ehzabeth Hospital, Umversay of Bwmmgham, UK Funded m part by Btomedtcal Sensors, UK, Ltd The prehmmary part of thls work was presented at the Twenty-Third Annual and Sclenttfic Symposium of the Soctety of Crztlcal Care Medzcme m Orlando, FL, m January 1994 Address repnnt requests to B Venkatesh, MD, Semor Regzstrar m Anaesthesta, Wycombe General Hospaal, Queen Alexandra Rd, Htgh Wycombe, Bucks. HPl l 2TT, Umted Kingdom. Copyright © 1995 by W B Saunders Company 1053-0770/95/0904-001153 00/0 Sensors, High Wycombe, UK, Ltd). The Paratrend 7 is a mult~parameter lntravascular sensor for the continuous measurements of pH, PCO2, and PO2. This sensor has been investigated in animals, in patients in the general intensive care unit, TM and in patients who have undergone CPB. Preliminary evaluation during cardiac surgery has shown that the sensor functioned well during CPB. 12 Reported here are the results of its use in 20 consecutive patients undergoing CPB, and its performance is compared with an in-line continuous blood gas sensor placed In the arterial limb of the extracorporeal circuit. MATERIALS AND METHODS After obtaining Hospital Ethical Committee approval and informed consent, 20 patients scheduled to undergo elective CPB for various operations were recruited into the trial. The average patient age was 59 years (range 43 to 78). Patients with atherosclerotic peripheral arterial disease, intermittent claudieatlon, coagulopathy, and inability to give reformed consent were excluded from the trial. Before induction of anesthesia, all patients had a 20G arterial catheter (Arrow International, Inc, Reading, PA) inserted under local anesthesia into the radial artery. Anesthesia was induced in all patients with a combination of fentanyl and etomidate, and muscle relaxation was achieved with pancuronlum. Anesthesia was maintained during the prebypass phase with enflurane. After induction of anesthesia, an 18G arterial catheter (Leadercath, Vygon, Ecouen, France) was inserted into the femoral artery for uninterrupted monitoring of blood pressure throughout the penoperative period. After the insertion of the femoral arterial catheter, a previously calibrated intravascular sen- sor was advanced through the 20G catheter into the radial artery to a length of 15 cm. Both arterial catheters were 412 Journal of Cardlothoracm and VascularAnesthesla, Vol 9, No 4 (August), 1995' pp 412-419