Abstract
Deep hypothermic circulatory arrest(DHCA), in which systemic temperatures of 2$0^{\circ}C$ or less are used to allow temporary cessation of the circulation, is an useful adjunct in cardiac surgery. Because man in natural circumstances is never exposed to the extreme hypothermic condition, however, one of the controversial aspects is appropriate blood gas management($\alpha$STAT versus PH-STAT) during DHCA. This study aims to compare $\alpha$STAT with PH-STAT management for control of blood gases in experimental cardiopulmonary bypass(CPB) circuits with a membrane oxygenator. Fourteen young pigs were assigned to one of two strategies of gas manipulation. After a median sternotomy, CPB was established. Core cooling was initiated and continued until nasopharyngeal temperature fell below 2$0^{\circ}C$. The flow rate was set at 2,500 ml/min. Once their temperatures were below 2$0^{\circ}C$, the animals were subjected to circulatory arrest for 40mins. During cooling, blood gas was maintained according to either $\alpha$$\alpha$STAT or pH-STAT strategies. After DHCA, the body was rewarmed to normal body temperature. Arterial blood gases were measured before the onset of CPB, before cooling, before DHCA, at the point of 27$^{\circ}C$ during re-warming, on completion of re-warming. Cooling time was significantly shorter in $\alpha$-STAT than PH-STAT strategy, while there was no significant differences in rewarming time between two groups. Carbon dioxide was added between 5.5 and 3.0% in PH-STAT, while no carbon dioxide was added in $\alpha$STAT management. Amounts of oxygen administration were gradually lowered as temperature decreased. In this way, criteria of PH, PaCO, and PaO adjustments were satisfied in both $\alpha$STAT and PH-STAT management groups.
체온을 섭씨 20도 이하로 인위적으로 감소시켜 혈액 순환을 일시적으로 중단시키는 초저체온 순환정지법은 심장수술의 한 보조방법으로 유용하게 이용되고 있다. 이러한 초저체온 상태는 정상적인 생리 상황이 아니기 때문에 이때 두가지 저체온 혈액가스 조절법인 STAT와 pH-STAT 조절법 중 어느 쪽을 택하는 것이 좋으냐에는 이론이 많다. 본실험은 막형 산화기를 사용한 심폐바이패스 생체 실험회로에서 두 저체온 혈액가스 조절법의 기술적인 측면을 비교하는데 목적이 있다. 실험동물로는 모두 14마리의 어린 돼지를 사용하였는데 두 실험군에 7마리씩 배정하였다. 정중흉골절개술후 동정맥 캐뉼라를 삽관하고 심폐바이패스를 시행하였다. 2500 ml/min의 관류 속도하에서 비인두 체온으로 2$0^{\circ}C$까지 관류냉각을 시행하고 40분 동안 초저체온 순환정지를 시행하였다. 냉각기간 동안 실험군에 따라 STAT 또는 pH-STAT군의 22.83$\pm$2.14분 보다 유의하게 짧았으나, 재가온시간에서는 STAT군(40.0$\pm$5.07분)과 pH-STAT군(46.5$\pm$6.32) 사이에 유의한 차이는 없었다. PH-STAT에서는 3.0-5.5 % 사이의 이산화탄소가 주입되었고 STAT에서는 이산화탄소의 추가 투여가 없었다. 산소 투여는 체온 감소와 함께 점진적으로 감소시켰다. 두 실험군 모두에서 PH, 이산화탄소분압 및 산소분압이 만족스럽게 조절되었다.