CARDIAC-OUTPUT AND CEREBRAL BLOOD-FLOW VELOCITY IN SMALL-FOR-GESTATIONAL-AGE INFANTS DURING THE FIRST 5 DAYS AFTER BIRTH

Small for gestational age (SGA) infants are at an increased risk of neurologic handicap. Cardiac output and cerebral blood flow velocity (CBFV) were measured by pulsed Doppler sonography in 15 SGA infants and in 15 appropriate for gestational age (AGA) infants on days 1 and 5 after birth. The gestational age of both groups ranged from 32 to 40 weeks and averaged 37 weeks. Cardiac output was higher in the SGA infants than in the AGA infants on day 1 (314 +/- 62 vs. 275 +/- 36 ml/min/kg; P < 0.05), but similar in the SGA and AGA infants on day 5 (319 +/- 66 vs. 318 +/- 53 ml/min/kg). On day 1, both haematocrit (0.53 +/- 0.04 vs. 0.49 +/- 0.04 l/l; P < 0.05) and systemic red blood cell transport (169 +/- 35 vs. 136 +/- 24 ml/kg/min; P < 0.01) were higher in the SGA infants than in the AGA infants. Systemic red cell now increased in the AGA infants from day 1 to day 5 (157 +/- 27 ml/min/kg; P < 0.05), but not in the SGA infants (166 +/- 39 ml/kg/min). Mean cerebral blood flow velocity (CBFV) was higher in the AGA infants than in the SGA infants on both days (P < 0.05). However, cerebral red blood cell transport(CBFV x haematocrit) was similar in both groups. We conclude that on day 1, systemic red blood cell transport is higher in SGA infants than in AGA infants due to increased cardiac output and haematocrit. Decreased CBFV in SGA infants is compensated for by increased haematocrit, thereby keeping cerebral red cell transport in the normal range.