Effect of alpha-stat vs. pH-stat strategies on cerebral oximetry during moderate hypothermic cardiopulmonary bypass.

BACKGROUND AND OBJECTIVES: This study was undertaken to compare the effect of alpha-stat vs. pH-stat strategies for acid-base management on regional cerebral oxygen saturation (RsO2) in patients undergoing moderate hypothermic haemodilution cardiopulmonary bypass (CPB). METHODS: In 14 adult patients undergoing elective coronary artery bypass grafting, an awake RsO2 baseline value was monitored using a cerebral oximeter (INVOS 5100). Cerebral oximetry was then monitored continuously following anaesthesia and during the whole period of CPB. Mean +/- SD of RsO2, CO2, mean arterial pressure and haematocrit were determined before bypass and during the moderate hypothermic phase of the CPB using the alpha-stat followed by pH-stat strategies of acid-base management. Alpha-stat was then maintained throughout the whole period of CPB. RESULTS: The mean baseline RsO2 in the awake patient breathing room air was 59.6 +/- 5.3%. Following anaesthesia and ventilation with 100% oxygen, RsO2 increased up to 75.9 +/- 6.7%. Going on bypass, RsO2 significantly decreased from a pre-bypass value of 75.9 +/- 6.7% to 62.9 +/- 6.3% during the initial phase of alpha-stat strategy. Shifting to pH-stat strategy resulted in a significant increase of RsO2 from 62.9 +/- 6.3% to 72.1 +/- 6.6%. Resuming the alpha-stat strategy resulted in a significant decrease of RsO2 to 62.9 +/- 7.8% which was similar to the RsO2 value during the initial phase of alpha-stat. CONCLUSION: During moderate hypothermic haemodilutional CPB, the RsO2 was significantly higher during the pH-stat than during the alpha-stat strategy. However, the RsO2 during pH-stat management was significantly higher than the baseline RsO2 value in the awake patient breathing room air, denoting luxury cerebral perfusion. In contrast, the RsO2 during alpha-stat was only slightly higher than the baseline RsO2, suggesting that the alpha-stat strategy avoids luxury perfusion, but can maintain adequate cerebral oxygen supply-demand balance during moderate hypothermic haemodilutional CPB.

Does isoflurane optimize myocardial protection during cardiopulmonary bypass?

OBJECTIVE: To investigate the possible myocardial protective effect of isoflurane during aortic cross-clamp and cardioplegic cardiac arrest in patients undergoing conventional coronary artery bypass graft surgery. DESIGN: Prospective, randomized. SETTING: University medical center. PARTICIPANTS: Forty-nine patients undergoing elective coronary artery bypass graft surgery divided into 2 groups: control group (n = 21) and isoflurane group (n = 28). INTERVENTION: Isoflurane was administered in the pre-cardiopulmonary bypass (CPB) period to the isoflurane group. MEASUREMENTS AND MAIN RESULTS: Hemodynamics and ST- segment variations were monitored in the pre-CPB period and after weaning from CPB in both groups. Incidence of reperfusion arrhythmias after release of aortic cross-clamp was compared. In the isoflurane group, the mean cardiac index after CPB was significantly higher than the pre-CPB value, whereas no difference between the 2 values was found in the control group. The higher cardiac index in the isoflurane group was associated with a lesser degree of ST- segment changes than in the control group. There was no significant difference between the 2 groups in the incidence of reperfusion arrhythmias after release of aortic cross-clamp. CONCLUSION: The present report suggests that administration of isoflurane before aortic cross-clamping in patients undergoing coronary artery bypass graft surgery may optimize the myocardial protective effect of cardioplegia. Isoflurane may be particularly advantageous whenever prolonged periods of aortic cross-clamping or inadequate delivery of cardioplegia is expected.

Successful resuscitation after catastrophic carbon dioxide embolism during laparoscopic cholecystectomy.

A 92-year-old female was scheduled for laparoscopic cholecystectomy. Following intraperitoneal carbon dioxide insufflation and removal of her gallbladder, the patient developed serious haemodynamic deterioration associated with a decrease of both end-tidal carbon dioxide concentration (ETCO2) and chest compliance. Carbon dioxide embolism was suspected and the diagnosis was confirmed by aspiration of 20 mL of foamy blood from the central venous line. The patient was successfully resuscitated after discontinuation of carbon dioxide insufflation and ventilation of the lungs with 100% oxygen. Carbon dioxide embolization must always be suspected during laparoscopic surgery whenever sudden haemodynamic deterioration associated with a decrease in ETCO2 and chest compliance occur.

Single vital capacity breath for preoxygenation.

PURPOSE: The report investigates, in awake patients before induction of anesthesia, the effect of preoxygenation by the single vital capacity breath technique following forced exhalation on the mean arterial PO2 (PaO2). METHODS: In 10 adult patients undergoing elective surgery, the mean PaO2 values achieved 30 sec after preoxygenation by the single vital capacity breath technique was compared with the mean PaO2 values achieved by preoxygenation by the traditional tidal volume breathing for three minutes. Each patient served as her/his own control. RESULTS: The mean PaO2 following the single vital capacity breath technique was higher (295 +/- 67 mmHg) than that achieved by the traditional tidal volume breathing technique at 30 sec and 60 sec, and was not significantly different from that achieved by the traditional technique after three minutes (307 +/- 70 mmHg). CONCLUSION: The single vital capacity breath technique following forced exhalation can rapidly provide adequate preoxygenation within 30 sec.

Sevoflurane anesthesia in a myasthenic patient undergoing transsternal thymectomy.

Myasthenia gravis (MG) is an autoimmune disease resulting from the production of antibodies against the acetylcholine receptors of the neuromuscular synapse. The thymus gland is involved in the autosensitization process, and there is a consensus that all adults with generalized MG should have a thymectomy. Removal of a much thymic tissue as possible via the transsternal approach in the logic goal of thymectomy in the treatment of MG. Because of the unpredictable response to succinylcholine and the marked sensitivity to nondepolarizing muscle relaxants in the MG patients, some anesthesiologists avoid the use of muscle relaxants in the myasthenic patients, and depend on deep inhalation anesthesia, such as halothane, isoflurane or sevoflurane. In the present report, we used sevoflurane 4%, without supplementation by muscle relaxants, for the induction and maintenance of anesthesia in a MG patient undergoing transsternal thymectomy. The report reviews the anesthetic technique, and describes the electromyographic (EMG) changes following sevoflurane.