The Effect of Paralysis on Oxygen Consumption in Normoxic Children after Cardiac Surgery

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Abstract
To determine whether paralysis reduces O2 consumption (.ovrhdot.VO2) after cardiac surgery in infants, .ovrhdot.VO2 was measured before and after paralysis in 17 sedated infants who were ventilated mechanically after cardiac surgery. O2 consumption was determined as being the difference between O2 content of inspired and expired gases. The absence or presence of movement (breathing or repeated movement of the extremities) before paralysis was noted. For 8 infants who did not move before paralysis, .ovrhdot.VO2 was similar before (9.1 .+-. 1.2 ml .cntdot. kg-1 .cntdot. min-1, mean .+-. SD) and after (9.0 .+-. 1.5 ml .cntdot. kg-1 .cntdot. min-1) paralysis (P = 0.81). For 9 infants who did "move" before paralysis, .ovrhdot.VO2 decreased from 9.2 .+-. 1.4 ml .cntdot. kg-1 .cntdot. min-1 before paralysis to 8.0 .+-. 1.4 ml .cntdot. kg-1 .cntdot. min-1 after paralysis (P < 0.05). One infant in each group had an increase in .ovrhdot.VO2 greater than 10% of the baseline value (i.e., 12% and 14%). If breathing or repeated movement is present before paralysis, paralysis decreases .ovrhdot.VO2 by 13% in sedated infants after cardiac surgery. If repeated or regular movement is not present before paralysis, paralysis does not decrease .ovrhdot.VO2. In normoxic patients, muscle paralysis does not significantly alter .ovrhdot.VO2 and therefore should not be used for this purpose.