Horn A R, Woods D L, Thompson C, Eis I, Kroon M
Neonatal Medicine, School of Child and Adolescent Health, University of Cape Town, South Africa.
S Afr Med J. 2006 Sep;96(9 Pt 2):976-81.
The main objective of this study was to study the safety and efficacy of a simple, cost-effective method of selective head cooling with mild systemic hypothermia in newborn infants with hypoxic ischaemic encephalopathy.
Ethical approval was obtained for a randomized controlled study in which 20 asphyxiated neonates with clinical signs of hypoxic ischaemic encephalopathy would be randomised into cooled and non-cooled groups. However, after cooling the first 4 babies, it was clear that repeated revisions to the cooling technique had to be made which was inappropriate in the context of a randomised controlled trial. The study was therefore stopped and the data for the 4 cooled infants are presented here in the form of a technical report. Hypothermia was achieved by applying an insulated ice cap to the heads of the infants and replacing it at 2-3-hourly intervals, aiming to achieve a target rectal temperature of 35-35.5 degrees C and a target scalp temperature of 10-28 degrees C.
This study was carried out between July 2000 and September 2001 in the neonatal units of Groote Schuur Hospital and Mowbray Maternity Hospital, Cape Town.
Term infants with signs of encephalopathy were recruited within the first 8 hours of life if they had required resuscitation at birth and had significant acidosis within the first hour of life.
Target rectal temperature was achieved in all infants, but large variations in incubator and scalp temperatures occurred in 3 of the 4 infants. Reducing the target core temperature in a stepwise manner did not prevent excessive temperature variation and resulted in a longer time to reach target temperature. There was least variation in scalp temperature when the ice pack was covered in two layers of mutton cloth before application, but the resulting scalp temperatures were above the target temperature. The maximum scalp temperature variation was reduced from 22 degrees C to 12 degrees C using this method. Nasopharyngeal temperatures varied excessively within less than a minute, suggesting that air cooling via mouth breathing was occurring. The surface site that correlated best with deep rectal temperature was the back, with the infant supine. During cooling, the respiratory rate and heart rate dropped while the mean arterial blood pressure was elevated. There were no irreversible adverse events due to cooling, but infants did become agitated and exhibited shivering which required sedation and analgesia.
Nasopharyngeal temperature monitoring was not reliable as an acute clinical indicator of brain temperature in these spontaneously breathing infants, and the back temperature in supine infants correlated better with deep rectal temperature than did exposed skin temperature. This method of cooling achieved systemic cooling but there were large variations in regional temperatures in 3 of the 4 infants. The variations in temperature were probably due to the excessive cooling effect of the ice cap, coupled with the use of external heating to maintain systemic temperature at 35-35.5 degrees C. Variation in temperature was reduced when additional insulation was provided. However, the additional insulation resulted in the loss of the selective cerebral cooling effect. This cooling technique was therefore not an appropriate method of selective head cooling, but did successfully induce systemic hypothermia. This method of insulating an ice cap could therefore be used to induce whole-body cooling but the use of lower core temperatures of 33-34 degrees C is recommended as this will probably result in fewer regional temperature fluctuations. Ideally a more uniform method of cooling should be used.
本研究的主要目的是探讨一种简单且经济有效的选择性头部降温并伴有轻度全身低温的方法对新生儿缺氧缺血性脑病的安全性和有效性。
本研究获得伦理批准，为一项随机对照研究，将20例有缺氧缺血性脑病临床体征的窒息新生儿随机分为降温组和非降温组。然而，在对最初4例婴儿进行降温后，很明显必须对降温技术进行反复修订，而这在随机对照试验的背景下是不合适的。因此该研究停止，这里以技术报告的形式呈现4例降温婴儿的数据。通过给婴儿头部戴上隔热冰帽并每隔2 - 3小时更换一次来实现低温，目标是使直肠温度达到35 - 35.5摄氏度，头皮温度达到10 - 28摄氏度。
本研究于2000年7月至2001年9月在开普敦的格罗特·舒尔医院和莫布雷妇产医院的新生儿病房进行。
有脑病体征的足月儿若在出生时需要复苏且在出生后第一小时内有明显酸中毒，则在出生后8小时内被纳入研究。
所有婴儿均达到目标直肠温度，但4例婴儿中有3例的暖箱温度和头皮温度出现较大波动。逐步降低目标核心温度并不能防止温度过度波动，且达到目标温度的时间更长。在使用前用两层羊肉布包裹冰袋时，头皮温度波动最小，但由此产生的头皮温度高于目标温度。使用该方法，最大头皮温度波动从22摄氏度降至12摄氏度。鼻咽温度在不到一分钟内变化过大，提示通过口呼吸进行空气冷却。与直肠深部温度相关性最好的体表部位是婴儿仰卧时的背部。降温过程中，呼吸频率和心率下降，而平均动脉血压升高。未出现因降温导致的不可逆不良事件，但婴儿确实变得烦躁并出现颤抖，这需要镇静和镇痛。
在这些自主呼吸的婴儿中，鼻咽温度监测作为脑温的急性临床指标不可靠，仰卧婴儿的背部温度比暴露的皮肤温度与直肠深部温度的相关性更好。这种降温方法实现了全身降温，但4例婴儿中有3例区域温度波动较大。温度波动可能是由于冰帽的过度冷却作用，再加上使用外部加热以将全身温度维持在35 - 35.5摄氏度。提供额外的隔热措施后温度波动减小。然而，额外的隔热措施导致选择性脑冷却效果丧失。因此，这种冷却技术不是一种合适的选择性头部降温方法，但确实成功诱导了全身低温。因此，这种给冰帽加隔热的方法可用于诱导全身冷却，但建议使用33 - 34摄氏度的较低核心温度，因为这可能会减少区域温度波动。理想情况下，应使用更均匀的冷却方法。
