最大长度序列脑干听觉诱发电位在头部低温治疗新生猪缺氧缺血性脑损伤中的动态变化

目的：探讨头部低温对缺氧缺血性脑损伤（hypoxic-ischemic brain damage, HIBD）新生猪最大长度序列脑干听觉诱发电位（MLS-BAEP）的影响。方法：16头5～7 d的新生猪随机分为3组：常温正常组（n=4）、缺氧缺血（HI）组（n=6）、HI低温组（n=6）。采用双侧颈总动脉阻断和机械通气吸入6％的氧气制备HIBD模型。缺氧缺血后2 h低温组采用选择性头部低温治疗24 h。各组分别在HI前、HI后12 h、24 h、36 h、48 h、60 h、72 h、4 d、7 d、10 d、13 d、15 d进行MLS BAEP测试。结果：HI组与正常组相比，从HI后72 h开始，各波潜伏期和峰间期明显延长，第7天达到高峰，第10天开始逐渐恢复，但除Ⅰ波潜伏期外，其他指标仍明显长于正常组，直至HI后15 d仍然没有恢复正常。HI低温组Ⅲ波潜伏期及Ⅰ~Ⅲ、Ⅰ~Ⅴ峰间期在HI后 60 h 至7 d，Ⅴ波潜伏期和Ⅲ~Ⅴ峰间期在HI后72 h至7 d 均明显短于HI组（P<0.05）。结论：新生猪HI后脑干听觉通路的外周部分和中枢部分均受累，表现为MLS-BAEP的各潜伏期和峰间期的明显延长，中枢损害在HI后第7天达到高峰，第15天仍然没恢复正常。HI低温治疗可明显减轻HIBD的脑干损伤。

Changes in MLS-BAEP in newborn piglets with hypoxic-ischemic brain damage during selective moderate head cooling therapy

Objective To study the effect of selective moderate head cooling therapy on maximum length sequences brainstem auditory evoked potential(MLS-BAEP) in newborn piglets with hypoxic-ischemic brain damage.Methods Sixteen newborn piglets aged 5-7 day old were randomly divided into three groups: normothermic control(n=4),HI(n=6) and mild hypothermia-treated(n=6).HI was induced through temporary occlusion of both carotid arteries,followed by mechanical ventilation with low concentration of oxygen(FiO2=0.06) for 30 minutes.Mild hypothermia was induced by equipment via circulating water.MLS-BAER was recorded before HI and at 12 hours,24 hours,36 hours,48 hours,60 hours,72 hours,4 days,7 days,10 days,13 days and 15 days after HI.Results Compared with the normothermic control group,all latencies and intervals tended to increase significantly at 72 hours in the HI group and reached peak values on day 7.From day 10,all latencies and intervals tended to decrease,but apart from wave I latency,still differed significantly from those of the normothermic control group.MLS-BAER variables did not reach normal values until day 15.Ⅲ latency,Ⅰ-Ⅲ interval and Ⅰ-Ⅴ interval were significantly reduced in the hypothermia-treated group between 60 and 7 days after HI compared with the HI group(P<0.05).V latency and Ⅲ-Ⅴ interval in the hypothermia-treated group were also reduced compared with the HI group between 72 hours and 7 days after HI(P<0.05).Conclusions Both peripheral and central auditory systems are disturbed by HI,which shows as a significant increase in MLS-BAER variables(all latencies and intervals) in newborn piglets.Involement in central brainstem auditory system reaches a peak on day 7 after injury.MLS-BAER variables still cannot reach to normal values until day 15.Selective moderate head cooling therapy can significantly reduce brainstem damage induced by HI.