CEREBRAL EFFECTS OF AORTIC CLAMPING DURING COARCTATION REPAIR IN CHILDREN - A TRANSCRANIAL DOPPLER STUDY

Objective: Haemodynamic changes as a consequence of application and re lease of aortic clamps for surgical repair of aortic coarctation are c ompensated by cerebrovascular autoregulation. Transcranial Doppler was used to study the effect of these haemodynamic changes upon brain cir culation in children during aortic coarctation repair. Method: A 2-MHz transcranial Doppler system continuously recorded mean cerebral blood how velocities from the left middle cerebral artery in 13 children ca ged from 5 days to 14 years) during repair of their coarctation. Measu rements were performed: prior to aortic clamping (baseline); during th e first 5 min after clamp application; 1 min before declamping; at 1, 2, 4 and 6 min after the release of both proximal and distal aortic cl amps; and at initial chest closure. A contralateral upper-limb non-inv asive blood pressure cuff measured systemic blood pressures. Haemodyna mic and anaesthetic parameters were monitored. Patients were stratifie d by age into two groups: age < 6 months (group A) and age > 6 months (group B). Results: With aortic clamping, systemic blood pressures (ra nge from: -16 to +54%) and cerebral blood flow velocities (range from -40 to +19%) changed slightly (P > 0.05) from initiation to end of aor tic clamping. In group A, release of aortic clamps resulted in moderat e fluctuations in systemic blood pressures !range from -34 to +15%) (P > 0.05) and a marked reduction in cerebral blood flow velocities (ran ge from -63 to -33%) (P < 0.01). At the time of surgical closure, how velocities had improved in all infants except one. Group B did not sho w major reductions in either cerebral blood flow velocity or systemic blood pressures throughout all measurements (P > 0.05). During aortic clamp release, young infants responded with lower brain blood flow vel ocities as compared to older children (r = 0.68; P < 0.05). Conclusion : Transient central nervous system hypotension results as a consequenc e of flow redistribution during aortic declamping in young infants. Ol der children usually show a faster autoregulatory compensation to thes e haemodynamic changes. The observed age-related physiologic differenc es, suggest that young infants may require higher systemic blood press ures during declamping to prevent the cerebral blood flow reduction. T ranscranial Doppler appears to be a valuable monitor of these cerebral haemodynamic changes. (C) 1998 Elsevier Science B.V. All rights reser ved.