Cerebral autoregulation analysis in ELBW infants. A and B represent the analysis for infants not receiving dopamine therapy, ie, infants who were clinically normotensive and untreated (control, n = 5) and infants who were clinically hypotensive and studied just before treatment with dopamine (predopamine, n = 12). C and D represent the analysis for the clinically hypotensive group after commencing dopamine therapy (dopamine). In untreated infants, a breakpoint in the autoregulation curve relating CBF to MAP was identified at MAP = 29 mm Hg (A), signified as the point where the residual sum of squares of bilinear regression analysis (see text) was at a minimum (B). No breakpoint was evident in the CBF versus MAP curve of infants undergoing dopamine therapy (C), because in these infants no minimum was identified by the bilinear regression analysis (D).
A, Serial measurements of CBF and MAP in a hypotensive ELBW infant between 13 and 40 hours after birth. Note the close variation of CBF with MAP, particularly after beginning dopamine infusion (10 μg · kg−1 per min). B, Plot of CBF versus MAP using the data of A reveals a positive linear correlation (R = 0.88; P < .001).