Neutrophil adhesion molecule expression is comparable in perinatal rabbits and humans.

BACKGROUND: Human newborns, particularly those born before full term, are more susceptible to bacterial infections as a result of impaired host defense mechanisms. Compared with adults, circulating leukocytes from human newborns (preterm and full-term gestations) and newborn rabbits (full-term gestation) have low resting levels of CD62L (L-selectin) and do not significantly increase surface expression of CD18 after inflammatory stimulation. To determine the potential utility of preterm rabbits in investigations of perinatal human conditions, the authors compared the surface expression of the beta 2-integrin CD18 and CD62L (L-selectin) on polymorphonuclear leukocytes (PMNs) from perinatal rabbits and perinatal humans, both under resting conditions and after in vitro activation with inflammatory stimulants. METHODS: After erythrocyte lysis of whole-blood samples, leukocytes from 7-day-old, full-term (31-day gestation), and preterm (24-day gestation) rabbits, as well as full-term (37-42 week gestation) and preterm (27-36 week gestation) human newborns were prepared and stimulated in vitro at 37 degrees C with either C5a or phorbol myristate acetate. After fluorescence labeling of CD18 and CD62L with monoclonal antibodies, PMN adhesion molecule expression was assessed by flow cytometry. RESULTS: Constitutive CD18 expression was not significantly different between perinatal and adult humans but was reduced in all perinatal rabbits compared with adults. Inflammatory stimulation caused significant increases in CD18 expression in adult human PMNs but not in full-term and preterm newborns. Changes in CD18 expression in adult and preterm rabbits after stimulation, although in the same direction as humans, were more variable. In both species, constitutive CD62L expression on PMNs from all perinates was significantly lower than in adults. However, CD62L was shed to similar degrees after inflammatory stimulation in all groups. CONCLUSIONS: Preterm rabbits may provide a potentially useful experimental model to study PMN adhesion and host defense in the perinatal period, particularly preterm gestations. Specific advantages and limitations of rabbits in such studies are discussed.

Succinylcholine does not change intracranial pressure, cerebral blood flow velocity, or the electroencephalogram in patients with neurologic injury.

The effect of succinylcholine (SCh) on intracranial pressure (ICP) was studied in 10 mechanically ventilated patients (Glasgow coma scale score 3-10, median 6) being treated for increased ICP in an intensive care unit. Mean arterial blood pressure (MAP), ICP, processed electroencephalogram (EEG), and mean middle cerebral artery blood flow velocity (V mca) were monitored. Baseline measurements after saline injection were obtained for 5 min. SCh (1 mg/kg) was administered intravenously and the above variables were monitored for 15 min. Neither saline nor SCh cause any significant change in cerebral perfusion pressure, MAP, V mca, EEG, or ICP. We conclude that in brain-injured patients, SCh did not alter cerebral blood flow velocity, cortical electrical activity, or ICP.