Deep hypothermia and total circulatory arrest: The effect of method of cooling on the catecholamine response to arrest

Abstract

Deep hypothermia and total circulatory arrest are used in the treatment of cardiac surgical patients in early infancy. These techniques produce a massive rise in serum norepinepherine and epinephrine levels. The effect of method of cooling on this response was investigated in 15 infant lambs during the first 2 weeks of life, mean age 4.8 days, mean weight 4.7 kg. Three groups were investigated—one in which continued cardiopulmonary bypass at 100 cc/kg and cooling and rewarming alone were employed; one in which core cooling, 1 hr of circulatory arrest, and warming were employed; and one in which surface cooling from 37 to 28°C then core cooling <18°C, arrest for 60 min, and rewarming to 37°C were employed. Temperature gradients between thermister sites in the brain, heart, nasopharyngeal, rectal, and peripheral muscle and blood samples for norepinephrine, epinephrine, and arterial pH measurements were obtained at 37°C control, <18°C preintervention, <18°C postintervention, 37°C postcontrol. Changes between pre- and post-intervention in each group and postcontrol values were elevated as well as gradients between thermistor sites. Results revealed no significant difference in arterial or venous pH in any group during the intervention period; elevation in muscle temperature and muscle-to-core temperature gradient in both the core-cooled groups; significant elevations in norepinepherine and epinepherine ( P < 0.001) in the arrested compared to the nonarrested groups; and significant elevations in the norepinephrine ( P < 0.05) in the surface/core from the core-arrested group. Postcontrol values for norepinephrine and epinephrine remained significantly elevated in both total circulatory arrest ( P < 0.001, P < 0.02) with norepinephrine in the surface/core group significantly elevated ( P < 0.05) over the core group. Results confirm that with deep hypothermia and total circulatory arrest a massive rise in norepinephrine and epinephrine occurs. Greater eveness of cooling results from a surface/core technique. In this group higher elevations in norepinephrine are demonstrated to be consistent with better cooling of the peripheral muscle bed, a biochemical marker of peripheral cooling and arrest. With rewarming significant elevations of both norepinephrine and epinephrine remain in both total circulatory arrest groups, while in the surface/core group norepinephrine levels remained significantly elevated over the core group. These findings are consistent with the gradients of cooling which exist in the surface/core group and reflect greater norepinephrine response from peripheral sources which persist in the postoperative period in these animals.