Induced mild hypothermia: the spearhead strategy for effective neonatal neuroprotection?

Cerebral injury during paediatric heart surgery: perfusion issues

Suboptimal neurodevelopmental outcome is common in children who have congenital heart disease. Its aetiology is often multifactorial. This review focuses on the role of cardiopulmonary bypass. Hypothermia is the mainstay of cerebral protection. Low flow and regional low flow are preferred to deep hypothermic circulatory arrest in many situations. Cooling and rewarming, aortopulmonary collaterals, pH, air emboli, the systemic inflammatory response, haematocrit, oxygenation, glucose and ultrafiltration can influence neurodevelopmental outcome. Although no pharmacological agents have been shown to have a beneficial effect on neurodevelopmental outcome in clinical practice in children, animal work on the use of steroids several hours before surgery is encouraging.

Postoperative hypothermia and blood loss after the neonatal arterial switch procedure

BACKGROUND

Numerous studies have demonstrated that mild hypothermia helps reduce hypoxic/ischemic brain injury that may occur during neonatal cardiac procedures. However, traditional intensive care practices emphasize aggressive rewarming, and the risk of excessive bleeding that may be related to hypothermia.

METHODS

An analysis was conducted of prospectively collected temperature and blood loss data on 47 neonates (30 boys, 17 girls) with transposition of the great arteries who underwent an arterial switch operation at median age 6 days (range, 2 to 23 days) and a mean weight of 3.6 +/- 0.6 kg. Blood loss was compared between 26 patients with mean temperatures below 35.5 degrees C for first 6 hours after operation (mild hypothermia group) and 21 patients at 35.5 degrees C or higher (normothermia group). Repeated-measures analysis of variance and regression modeling were used to evaluate the association between temperature and blood loss and to detect outliers.

RESULTS

Total postoperative blood loss was 31 +/- 28 mL in the first 6 hours and 61 +/- 37 mL at 24 hours (range, 15 to 238 mL). Postoperative blood loss between two groups at 6 or 24 hours did not differ significantly. After two outliers were removed, no significant relationship remained between body temperature at 6 hours and cumulative blood loss at 24 hours.

CONCLUSIONS

Mild postoperative hypothermia does not increase blood loss in neonates after the arterial switch operation. Lack of a difference between the two groups is not likely due to the study being underpowered. We recommend avoidance of aggressive rewarming, which might exacerbate potential neurologic injury.

Brain injury in children with congenital heart disease

The incidence of neurodevelopmental impairment in children with congenital heart disease is high. Its aetiology is multiple and complex. Prevention and treatment must start during the preoperative period and continue through the intra- and postoperative periods. Research has resulted in a clearer understanding of the relationship between congenital heart disease and the brain, and of the effects of cardiopulmonary bypass, hypothermia and circulatory arrest. This has led to modifications in management which may improve neurological outcome in the future.