睡眠醫學---手術前的叮嚀

正當我埋首處理文件時，外科部的黎醫生突然打電話給我，並告訴我振華(假名)在手術前想見我一面。當下我心裡涼了一大半，難道好友振華患上了大病，在手術前有什麼最後的叮嚀! 我立即火速奔跑到病房看過究竟，內心忐忑不安。經詳細了解後才發現他原來是患上嚴重膽囊發炎，但膽管鏡和抗生素卻不能控制他的病情，所以外科醫生決定為振華動手術。由於振華一向患有嚴重的睡眠窒息症 (Obstructive Sleep Apnea, OSA)，所以麻醉科醫生強烈要求呼吸科醫生為振華作手術前評估，黎醫生就順理成章急急聯絡我幫忙。

振華卻埋怨麻醉科醫生小題大做，直截了當動手術不就可以嗎? 我立即為麻醉科醫生解說，多個研究發現患有睡眠窒息症(OSA)的病人在手術前後容易有併發症(1,2,3)。舉例說他們有較多機會在手術後需要再次插喉治療(e.g. higher post-operative reintubation rates)(4)。這批病人亦可能會有較長時間缺氧、心臟缺血和心律不正(cardiac complications including ischemia and dysrhythmias)、需要入住深切治療部(unplanned admissions to the intensive care unit ,ICU) 及較長時間住院接受治療(prolonged hospitalization )(2)。一個包涵3942位病人的薈萃分析(meta-analysis)更加發現OSA病人有更高的急性呼吸衰歇率、手術後缺氧和心臟病併發症(higher incidence of acute respiratory failure, post-operative drops in oxygen saturation, cardiac events) 的機會(4)，而另一類似的薈萃分析(5)也得出相同的結論。另一組學者(6)更收集了一些OSA病人在手術後所得的嚴重併發症，如腦部缺氧受損甚或死亡個案等，情況不容忽視。

振華好奇地追問為何OSA病人在手術後可能有如斯多併發症。綜觀其可能性包括: 醫生替病人插喉或拔喉時遇上困難、麻醉及止痛藥引發病人上呼吸道肌肉鬆弛和呼吸動力下降、病人手術後需要長時間仰臥休息及REM睡眠比例突增(mechanisms: difficulty during tracheal intubation and extubation ; the effects of anesthetics, sedatives, and narcotics on upper airway muscle tone and ventilatory responsiveness; postoperative supine positioning; and increased rapid eye movement (REM) sleep on the nights following the first postoperative night)(7-13)。這些因素都可能加劇睡病人睡眠窒息症的病情，引致病人夜間缺氧和血中二氧化碳上升等惡果，因而造成手術後各種嚴重併發症(14-15)。

相對來說振華比較幸運，因為在手術前各方面已知曉他患有睡眠窒息症，因此能

安排專科醫生為振華作手術前評估及介入治療。更有一個研究指出高達八成病人在手術前並不知道自己原來患有睡眠窒息症(16)，因此這些病人在沒有足夠的準備下便進行了手術，繼而有可能產生各種不良後果；另一方面醫生亦可能太遲才察覺病人有可能患有睡眠窒息症，但已來不及在手術前再作進一步檢查吧!

那麼醫護人員面對已確診或可能患上睡眠窒息症的病人，而他們卻要進行手術，應該如何是好呢? 幸好醫學界在2014年(17)及2016年(18) 發佈了兩份重要指引，幫助前線醫護人員應對這難題: 首先醫護人員要認清睡眠窒息症病人的獨特手術風險、在手術前善用問卷(STOP-BANG-19; Berlin & ASA Check list-20)來找出那些病人潛藏著睡眠窒息症、詳細了解那些已明確患有OSA病人的病情、以及在手術前後持續正確使用連續正壓呼吸機(Continuous Positive Airway Pressure, CPAP machine)(21)。如發現病人有不尋常的缺氧、肺動脈高壓(Pulmonary Hypertension) 或通氣不足綜合症(Hypoventilation syndrome)，那麼醫生就要審視是否需要在手術前作進一步評估，甚或延遲動手術。麻醉科醫生應為病人選用合適麻醉方法，減少藥物對病人呼吸系統的不良影響(e.g respiratory suppression) 。在手術後尤其是拔喉後，對病人嚴密的監察甚或較長時間的監察至為重要。而那些極可能患上睡眠窒息症，但又趕著接受手術的病人，我們會一慨視之為如同確診睡眠窒息症一般處理，萬事以病人安全為上。

與麻醉科醫生一同匯診及制定治理方案後，振華順利進行了所需手術，一切安好。

參考文獻:

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