围术期脑保护的研究进展

For fasting plasma glucose concentrations >110 mg/dL, each 10 mg/dL increase in serum glucose concentration was associated with a 6% greater risk of fatal stroke events (P=0.05) and an 8% increase in nonfatal stroke events (P<0.05).
1． 1 选择性脑降温 1． 2 控制血糖 1． 3 控制血压和保证氧供
1. 4 血红蛋白浓度

选择性脑降温是指在离头部较近处加强热 量散发，使颅内温度低于躯体温度，可以 避免全身低温所带来的不利影响，同时又 能有效地改善缺血缺氧性脑损伤。
脑保护机制不仅与降低脑代谢率有关，还 涉及抑制缺血缺氧诱发的“瀑布式反应” 的进展，如抑制谷氨酸释放、减少自由基 生成、抑制凋亡、保护血脑屏障等，并且 可为其他治疗措施延长治疗时间窗。


Cell-free hemoglobin-based oxygen carriers, such as polynitroxylated pegylated hemoglobin, offer promise in this setting by increasing oxygen-carrying capacity without excessively increasing blood viscosity.
Nonfatal stroke rate was 10.3, 11.8, and 18.0 per 10,000 person-years in the 3 groups (P=0.002). Fatal stroke, with stroke rates of 2.1, 3.4, and 4.0 per 10,000 person-years (P=0.008).
Polynitroxylated pegylated hemoglobin: a novel neuroprotective hemoglobin for acute volumelimited fluid resuscitation after combined traumatic brain injury and hemorrhagic hypotension in mice. Crit Care Med. 2011; 39:494–505.

Lasarzik reported in a rat model, transfusion of autologous blood, even in the presence of cerebral ischemia, does not increase brain concentrations of inflammatory mediators.
维持基础的平均动脉血压和保证足够 的氧供是最基本的脑保护措施

Optimum serum hemoglobin concentration in patients with ischemic stroke is not well characterized, in part because 2 contradictory theories exist.

There has been concern recently of possible brain inflammation associated with an intraoperative autologous (ie, “cell saver”) transfusion, as a result of activation of the inflammatory cascade secondary to blood interactions with the extracorporeal circuit.
Very early hypothermia induction in patients with severe brain injury (the National Acute Brain Injury Study: Hypothermia II): a randomised trial. Lancet Neurol. 2011;10:131–139.


Keller reported that anemia on admission and at day 5 was more common in patients with a poor outcome at 3 months. Patients with anemia during the first 5 days of hospitalization were 2.61 (P=0.005) times more likely to have a poor outcome at 3 months.
不过有一点可以肯定:
围术期高热会使临床结局变得更差

大量研究证实，围术期控制血糖有助于改善患 者神经功能预后。
在一些危重和心脏手术患者中，严格控制围术 期的血糖水平可以降低脑缺血发病率和病死率。 围术期持续高血糖可增加缺血性脑损伤的范围， 使得临床结局更差。McGirt 的研究发现，血糖 ＞ 11． 11 mmol /L ( 无论患者是否患有糖尿病) 可使颈动脉内膜剥脱术围术期脑卒中发生率增 高。但是严格的血糖控制( 4． 44～ 6． 11 mmol /L) 可能会增加低血糖的风险。


BG concentrations were stratified into 3 groups: (1) normal (80 to 109 mg/dL); (2) impaired (110 to 125 mg/dL); and (3) diabetes mellitus (>=126 mg/dL).
依据目前临床证据
围术期仍应该避免高血糖的发生

首先，脑组织的代谢率较其他组织 器官高。
其次成人脑的重量仅占体质量的2%，但其 血液灌注量却占全身血流量的13%～ 20%， 脑组织对氧的需求量为42～ 45 mL /min， 耗氧量占全身耗氧量的15%～ 20%. 脑组织对缺氧极为敏感，而其本身的氧储 备又微乎其微。
The primary outcome measure was the rate of poor outcome (ie, GOS showing severe disability, vegetative state, or death).


This trial was terminated prematurely due to futility. There was no difference in the rate of poor outcome (60% vs. 45% for hypothermia and normothermia, respectively; P=0.67) or death (23% vs. 14%, P=0.52).
Data were stratified according to admission hemoglobin A1c into 4 categories: (1) <6.2% (2) 6.2% to 6.8% (3) 6.9% to 8.3% (4) >8.3%.


Increasing hemoglobin A1c was associated with a reduced risk of neurologic improvement after stroke (P<0.001 for trend) and an increased risk for poor functional outcome.

Hale Waihona Puke 有研究已证实降低平均动脉血压可导致脑 缺血患者临床结局的恶化，所以围术期神 经并发症高危患者中维持“较高”的平均 动脉压是安全、有效、可行的办法。
Cardipulmonary bypass management and neurologic outcome: an evidence-based appraisal of current practices［J］． Anesth Analg，2006， 103( 1) : 21-37．



Sui reported data from 43,933 men who underwent a comprehensive preventative medical between 1971 and 2002 （were free of myocardial infarction, stroke, cancer, or known diabetes mellitus） They were followed until either stroke, death, or the study end date (December 31, 2004) occurred.
A prospective study of fasting plasma glucose and risk of stroke in asymptomatic men. Mayo Clin Proc. 2011;86:1042–1049.

Kamouchi utilized data from 3627 patients with primary ischemic stroke with a hemoglobin A1c available from hospital admission.
Cerebral oxygen transport failure?: decreasing hemoglobin and hematocrit levels after ischemic stroke predict poor outcome and mortality: Stroke: RelevAnt Impact of hemoGlobin, Hematocrit and Transfusion (STRAIGHT)–an observational study. Stroke. 2011;42: 2832–2837.