The metabolic responses t o a c o n s t a n t glucose i n f u s i o n (4.3% .2 mglkglrnin) were measured i n 30 prematures, 700-15598. The s t u d y included 1 8 s t r e s s e d i n f a n t s who needed a s s i s t e d v e n t i l at i o n (Grp A) and 12 c o n t r o l s (Grp B). Plasma samples f o r gluc o s e , i n s u l i n , c o r t i s o l , and g l y c e r o l were obtained from cord blood, j u s t p r i o r t o glucose i n f u s i o n a t 2.1+.2 h r (mean + S.E.)

Peripheral blood flow and systolic blood pressure (strain-gauge plethysmograph), blood volume (Evans blue) and whole blood viscosity (cone-plate viscometer) have been measured in 66 premature and full-term infants 6 to 144h of age. Blood flow and blood volume were moderately decreased in the infants with respiratory distress. Highly significant (P less than 0.001) correlations were found between blood flow and blood volume (r = 0.77), blood pressure and blood volume (r = 0.50), peripheral resistance and blood volume (r = -0.44), blood flow and blood pressure (r = 0.50), blood flow and peripheral resistance (r = -0.67), peripheral resistance and blood viscosity (r = 0.45), and blood viscosity and haematocrit (r = 0.86). There was no correlation between peripheral blood flow and blood viscosity. However, at given blood volume, peripheral blood flow decreased with increasing blood viscosity. These results indicate that in newborn infants peripheral blood flow, blood pressure and peripheral resistance are influenced by blood volume, but also depend on blood viscosity.

Venous and capillary hematocrit, acid base values, and circulatory parameters were measured simultaneously in 92 newborn infants within six hours of birth. Gestational age ranged from 26 to 41 weeks. The capillary/venous hematocrit ratio (Hctc/Hctv) was greater than 1.00 in 89 infants. We found significant inverse correlations between Hctc/Hctv and several parameters, such as pH (r = -0.82), standard bicarbonate (r = -0.73), systolic blood pressure (r = -0.51), and peripheral blood flow (r = -0.70). Most of the infants with a Hctc/Hctv of 1.20 and above had red cell mass values of less than 35 ml/kg. However, blood volume apparently did not influence the Hctc/Hctv. Gestational age appeared to affect Hctc/Hctv only before 30 weeks, when compared with the Hctc/Hctv of term infants. Our results indicate that disturbed circulation, and in particular, disturbed microcirculation is involved in the development of high Hctc/Hctv ratios. We strongly advise that hematocrits obtained by skin prick from a sick newborn infant should not be relied on as they may give misleading information on oxygen carrying capacity to vital organs.

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