[Mild hypothermia and cerebral protection]

Induced hypothermia as salvage treatment for refractory cardiac failure following paediatric cardiac surgery

OBJECTIVE

Following corrective cardiac surgery in infants and children for congenital heart disease, a persistent low cardiac output refractory to conventional modes of treatment is associated with a mortality approaching 100%. We advocate the use of whole body hypothermia to reduce tissue oxygen demand and provide a degree of cellular protection against ischaemia allowing time for recovery. We describe our experience.

METHODS

Between July 1986 and December 1995, 1885 infants and children underwent surgery (operative mortality, 6%), 1302 requiring cardiopulmonary bypass. Fifty-seven patients had a persistent low cardiac output, impaired respiratory function, decreased urine output and acidosis despite maximal intensive care treatment. Cooling to 32-33 degrees C was therefore started using a thermostatically controlled water filled cooling blanket.

RESULTS

Following cooling, there was a fall in heart rate (P<0.001), a rise in mean arterial pressure (P<0.001) and a fall in mean atrial pressure (P<0.001). Significant (P<0.001) increases in pH and urine output were also recorded. Thirty-one (54%) of the 57 patients treated with cooling survived to leave hospital. No long-term sequelae have been noted in these patients.

CONCLUSION

Induced hypothermia is a useful salvage treatment, in children following corrective cardiac surgery when all conventional treatment has been tried and failed.

[Hypothermia in traumatology]

Basing on the experience of the Chamonix hospital team which managed in six years 89 cases of hypothermia in trauma patients, this article reviewed the literature concerning the association hypothermia-trauma. Shock is a major triggering factor. The deleterious effects of hypothermia on the outcome is due to inadequate cardiorespiratory adaptation to shock and to increased bleeding. Although a few articles reported a beneficial effect of hypothermia in head trauma, further studies are required to assess the value of deliberate hypothermia in such patients. Restoration of a satisfactory haemodynamic activity is a priority and most often requires surgery. The rewarming manoeuvres should be initiated early and always be preventive. They are active, internal and rapid in case of haemodynamic instability and when the central temperature is below 32 degrees C. It can be more progressive and less invasive in other cases. During recovery from anaesthesia the patient must be closely monitored. In spite of a possible protecting effect, hypothermia remains an aggravating factor in traumatology and must therefore be either prevented or amended.

Induced hypothermia in the postoperative management of refractory cardiac failure following paediatric cardiac surgery

Postoperative low cardiac output states are a major cause of postoperative mortality in infants and children following corrective cardiac surgery for congenital heart defects. In this unit, whole body hypothermia has been used since 1979 in the management of these low output states when they are refractory to conventional modes of therapy. Twenty cases treated in this way between July 1986 and June 1990 were reviewed in 1992. The current report reviews the 50 further cases treated with moderate hypothermia between July 1990 and December 1995. The median (range) age of patients was 8 months (0 days-16 years) with a median weight of 4.1 kg (2.5-33 kg). Following cooling, there was a decrease in heart rate (p < 0.001), an increase in mean arterial pressure (p < 0.001) and a decrease in mean atrial pressure (p < 0.001). Significant increases in pH and urine output were also noticed, the increase in urine output being greater in the surviving group (p = 0.02). A decrease in platelet count occurred (p < 0.001) but white blood cell count remained unchanged (p = 0.18). Twenty-five of the 50 patients survived to leave hospital. Induced hypothermia does not appear to be associated with any complications and after the failure of all conventional treatment, it seems likely that the technique may have been beneficial to outcome in some patients.

[Emergency EEG and brain injuries]

The aim of this study is to review indications for emergency EEG in case of brain trauma. The authors emphasize the indication of emergency EEG for the diagnosis of either cerebral death or early post traumatic seizures, and for the monitoring of intensive neurological treatments. Emergency EEG and diagnosis of cerebral death has been reviewed in another issue of this journal. Diagnosis of early post-traumatic seizures may be difficult in case of cranial trauma in either the presence or the absence of coma. Emergency EEG help guide the diagnosis of electrical signs of seizures, thus indicating that treatment with antiepileptic drugs is advisable. Severe post-traumatic coma requires barbiturate impregnation and moderate hypothermia. In this last case, emergency EEG is essential for the monitoring of pharmacological treatments. The authors conclude that continuous EEG monitoring could in the future substitute for standard EEG recorded in emergency.