Physiologic and neuropathologic aspects of hypothermic circulatory arrest in newborn dogs

A model of hypothermic circulatory arrest has been developed in the newborn dog. Ten puppies were anesthetized with halothane, paralyzed, and artificially ventilated with 70% nitrous oxide 30% oxygen to arterial oxygen pressure greater than 8.0 kPa (60 mm Hg), arterial carbon dioxide pressure of 4.4-5.6 kPa (33-42 mm Hg), and arterial pH of 7.35-7.42. Animals were surface cooled to 20 degrees C, after which cardiac arrest was produced with i.v. KCl. Dogs remained asystolic without ventilation for 1.0 (n = 4), 1.5 (n = 3), or 2.0 (n = 3) h. Resuscitation was accomplished with closed-chest compression, mechanical ventilation, i.v. epinephrine and NaHCO3, and rewarming to 37 degrees C. Postarrest recovery was maintained for 3-4 h; thereafter, the puppies underwent perfusion-fixation of their brains for pathologic analysis. Plasma glucose (control = 8.3 mmol/L) increased slightly during hypothermic cardiac arrest (+36%) but was markedly elevated at 15 min postarrest (20 mmol/L). Blood lactate (control = 1.1 mmol/L) increased almost 200% during hypothermic circulatory arrest, with a further rise to 9.0 mmol/L at 15 min postarrest. Thereafter, lactate decreased in the 1-h arrested dogs but increased progressively in the other groups. Mean arterial blood pressure returned to baseline (73 mm Hg) by 15 min postarrest, remained stable in the 1-h dogs, but fell at 3 h to 62 and 34 mm Hg in the 1.5- and 2.0-h groups, respectively. No neuropathologic alterations were seen in puppies arrested for 1 h, whereas all puppies arrested for 1.5 or 2 h had varying degrees of cerebral cortical and hippocampal damage.(ABSTRACT TRUNCATED AT 250 WORDS)