心率變異於心臟停止及低溫治療的變化及其與復甦後預後的關係

Abstract

背景 低溫治療可用於治療復甦後的心肌功能不良。但是，其與心率變異的關係，以及心率變異所可能扮演的關於預後的預測角色，尚未有嚴謹的基礎實驗來探討。 材料與方法 研究分為兩大部分。其一，先將實驗用大鼠隨機分配為四組並給予四種處置，分別為sham組，只做低溫組，只引發心臟停止組，以及引發心臟停止後再給予復甦後的低溫治療。連續記錄這四組的心電圖四個小時，並每個小時取五分鐘心電圖計算心率變異，探討不同狀況下心率變異的時序變化。其二，把實驗用大鼠引發心臟停止，心肺復甦使其循環恢復後隨機分配為兩組，分別為常溫以及低溫治療四小時。接著，待麻醉結束後統計其三天存活率。並且分別分析其復甦後的心率變異是否可用來預測預後。 結果 在第一個實驗，四組各分配到10隻大鼠。在僅接受低溫治療以及僅引發心臟停止的動物身上，可以見到各心率變異的指標有顯著的上升。在循環恢復後進行低溫治療的第四組動物身上，可以見到心率變異有更明顯的上升。其中，RMSSD以及HF power兩指標的上升最為明顯。在第二個實驗，循環恢復後有16隻被分配入常溫組，14隻被分配入低溫組。常溫組的三天存活率是44%（7/16），低溫組的三天存活率是57%（8/14）。在常溫組，存活三天的動物比起無法存活的有顯著較高的SDNN、RMSSD、total power、LF power、HF power。在低溫組，則未見這種差異。 結論 低溫治療及心肺復甦循環恢復後可見實驗動物的心率變異上升。而循環恢復後施予低溫治療，可以讓此上升更明顯。此現象尤可見於RMSSD以及HF power。在不進行低溫治療的動物，循環恢復時的心率變異跟三天存活率有關，而進行低溫治療的動物則沒有此現象。

Background: Little is known regarding heart rate variability (HRV) during therapeutic hypothermia (TH) in the post-resuscitation setting, as well as the role of HRV in predicting post-resuscitation outcome. Objective: This study was aimed at testing the association between HRV and TH, and investigating the ability of HRV in predicting outcome in the post-resuscitation setting. Materials and methods: Adult male Wistar rats were subjected to asphyxial cardiac arrest (CA) and subsequent cardiopulmonary resuscitation (CPR). Once return of spontaneous circulation (ROSC) was achieved, TH was implemented using external cooling method and lasted at target temperature (32 to 32.5℃) for 4 hours. Electrocardiographic (ECG) signals were recorded throughout the experiment, and HRV was calculated using 5-min epochs hourly. Survival was assessed after 3 days. Thereafter, the association between HRV and 3-day survival was evaluated. Results: HRV, in terms of various time-domain and power spectral measures, was elevated during TH when CA was not induced. When compared with sham group, rats that were subjected to CA had higher HRV in the post-resuscitation period. HRV was even higher when TH was induced in the post-resuscitation period. When evaluating the association between HRV and 3-day survival, HRV during normothermia demonstrated higher associations with outcome, compared with HRV during TH. Conclusion: HRV reflected the autonomic modulation in response to TH and induced CA and elevated during these stresses. The predictive value of HRV on 3-day survival was better during normothermia than during TH.