肢体缺血后处理单用或联合亚低温对心肺复苏后机体炎症反应和肺损伤的影响

Effects of limb ischemic post-conditioning alone or its combination with therapeutic hypothermia on systemic inflammatory response and lung injury after cardiopulmonary resuscitation

目的探讨肢体缺血后处（LIpostC）单用或联合亚低温（TH）对心搏骤停-心肺复苏（CA-CPR）后机体炎症反应和肺损伤的影响。方法健康雄性白家猪21只，体重（37±2）kg，按随机数字表法将动物分为对照组、LIpostC组、LIpostC＋TH组3组，每组7只。采用CA-CPR法制备动物模型。CPR开始时，LIpostC组和LIpostC＋TH组通过4个循环的肢体加压与解压诱导LIpostC。复苏成功后，LIpostC＋TH组通过降温毯快速诱导TH，使体温维持在32-34℃至复苏后4h，随后以1℃／h的速度复温4h；对照组和LIpostC组维持正常体温。记录各组动物CPR期间复苏情况；于CA前15rain（基础值）及复苏后4h内，每2h测定1次血乳酸和氧合指数（PaO2／FiO2），用脉搏指示连续心排血量（PiCCO）监测血管外肺水指数（EVLwI）和肺血管通透性指数（PVPI），每小时记录1次数值。于CA前15min（基础值）及复苏成功后2、4、24h采用酶联免疫吸附试验（ELISA）检测血清肿瘤坏死因子-α（TNF-α）和白细胞介素-6（IL-6）水平。结果每组均成功复苏6只动物。3组CPR期间冠脉灌注压（CPP）、复苏时间、除颤次数、肾上腺素用量等比较差异均无统计学意义。CA前3组动物血乳酸、PaO2／FiO2、EVLWI、PVPI、细胞因子等基线水平比较差异也无统计学意义。3组复苏后血清TNF-α和IL-6水平均逐渐升高；但LIpostC组和LIpostC＋TH组TNF-α、IL-6水平均较对照组显著降低，且LIpostC＋TH组较LIpostC组进一步降低[TNF-α（ng／L）：4h为305±22比343±26，24h为350±29比389±18；IL-6（ng／L）：24h为239±14比263±19，均P〈0．05]。3组复苏后2h血乳酸水平达峰值，随后下降；复苏后4hLIpostC组和LIpostC＋TH组血乳酸已恢复至基础水平，均显著低于对照组（mmol／L：1．4±0．7、1．2±0．3比3．1±1．7，均P〈0．05）。复苏后4h内，LIpostC组和LIpostC＋TH组氧合指数（PaO2／FiO2）显著高于对照组，EVLWI、PVPI显著低于对照组，且LIpostC＋TH组PaO2／FiO2和EVLWI均较LIpostC组改善更为显著[4hPaO2／FiO2（mmHg，1mmHg=0．133kPa）：391±26比361±20；4hEVLWI（mL／kg）：10．1±1．5比12．1±1．2，均P〈0．05）。结论LIpostC有助于减轻猪CA-CPR后机体的炎症反应与肺损伤，LIpostC联合TH可进一步增强这种保护效应。

Objective To investigate the effects of limb ischemic post-conditioning （LIpostC） alone or its combination with therapeutic hypothermia （TH） on systemic inflammatory response and lung injury after cardiac arrest （CA） and resuscitation. Methods Twenty-one healthy male pigs weighing （37± 2） kg were randomly divided into 3 groups （n = 7 each）： control group, LIpostC group, and LlpostC＋TH group. The animal model was established by 10 minutes of untreated CA and then 5 minutes of cardiopulmonary resuscitation （CPR）.Coincident with the start of CPR, LIpostC was induced by four cycles of 5 minutes of limb ischemia followed by 5 minutes of reperfusion in the LIpostC and LIpostC＋TH groups. After successful resuscitation, TH was implemented by surface cooling to reach a temperature of 32-34% until 4 hours post-resuscitation, followed by a re-warming rate of ℃/h for 4 hours in the LIpostC＋TH group. Normal temperature was maintained in the control and LIpostC groups. The resuscitation outcomes in each group were recorded during CPR. At 15 minutes prior to CA （baseline） and during 4 hours post-resuscitation, the level of arterial lactate was measured and PaO2/FiO2 was calculated, and extra-vascular lung water index （EVLWI） and pulmonary vascular permeability index （PVPI） were measured meanwhile by a PiCCO monitor. At 15 minutes prior to CA （baseline） and during 24 hours post-resuscitation, the levels of serum tumor necrosis factor-α （TNF-α） and interleukin-6 （IL-6） were measured by enzyme linked immunosorbent assay （ELISA）. Results Six animals in each group were successfully resuscitated. Coronary perfusion pressure （CPP）, duration of resuscitation, number of shocks andepinephrine dosage during CPR were not statistically significant among the three groups. The baseline of arterial lactate, PaO2/FiO2, EVLWI, PVPI and cytokines prior to CA were also not statistically significant among the three groups. The levels of serum TNF- cL and 1L-6 after resuscitation were gradually increased in all the three groups; however, the values of TNF-α and IL-6 were significantly lower in the LIpostC and LIpostC＋TH groups than that in the control group, and they were further decreased in the LIpostC＋TH group when compared to the LIpostC group [TNF-α （ng/L）： 305 ± 22 vs. 343± 26 at 4 hours, 350± 29 vs. 389 ± 18 at 24 hours; IL-6 （ng/L）： 239 ± 14 vs. 263 ± 19 at 24 hours, all P 〈 0.05]. The levels of lactate reached the peak at 2 hours post-resuscitation and then gradually decreased in all the three groups; it finally returned to the baseline in the LIpostC and LIpostC＋TH groups, which was markedly lower than that in the control group （mmol/L： 1.4± 0.7, 1.2±0.3 vs. 3.1 ± 1.7, both P 〈 0.05）. During 4 hours post-resuscitation, PaO2/FiO2 was significantly higher and EVLWI and PVPI were markedly lower in the LIpostC and LIpostC＋TH groups than that in the control group; additionally, PaO2/FiO2 and EVLWI were further improved in the LIpostC＋TH group than the LlpostC group [4-hour PaO2/FiO2 （mmHg, 1 mmHg - 0.133 kPa）： 391 ±26 vs. 361 ±20; 4-hour EVLWI （mL/kg）： 10.1 ± 1.5 vs. 12.1 ± 1.2, both P 〈 0.05]. Conclusion LIpostC can be used to alleviate systemic inflammatory response and lung injury after porcine CA and CPR, and its combination with TH further enhanced its protective effects.