Near-term Lambs Research Articles

Intracranial hemorrhage following intravenous administration of sodium bicarbonate or saline solution in the newborn lamb asphyxiated in utero.

The effects of intravenously administered sodium bicarbonate were studied in near-term neonatal lambs asphyxiated in utero by maternal hypotension. Following tracheal intubation and manual ventilation with 100 per cent oxygen, the extracellular base deficits of ten neonates were corrected with sodium bicarbonate, 4.2 per cent, in 5 per cent dextrose (964 mOsm/1). Nine neonates alternatively received an isovolumic infusion of physiologic saline solution, 0.5 percent, in 2.5 per cent dextrose (314 mOsm/1). Following sodium bicarbonate infusion (mean dose 6.7 mEq/kg), serum sodium and osmolality immediately increased to 160 mEq/1 and 335 mOsm/1, respectively. However, sodium values were similar in the two groups by 15 min after infusion. Although significant differences in PAO2 values were not found between groups after infusion, sodium bicarbonate therapy was associated with a significantly higher PAO2 value (175 ± 60 torr) than was treatment with saline solution (51 ± 8 torr) in neonates with pHa

PAH clearance, sodium excretion, and PAH extraction ratio in acidotic near-term lambs treated with hypertonic sodium bicarbonate.

The electrolyte changes and renal hemodynamic adjustment to hypertonic sodium bicarbonate (NaHCO3) correction of a metabolic acidosis were studied in 4 neonatal lambs and in 2 controls. PAH clearance increased from 0.92 to 1.65 ml/min/kg (p less than 0.05), urine flow from 0.37 to 0.61 ml/min/kg (p less than 0.05), and Na excretion from 8.4 to 23.7 muEq/min/kg (p less than 0.05) during the NaHCO3 infusion. These increases were transient and returned to pre-infusion levels following NaHCO3 infusion. Calculation of Na intake and output revealed a net retention of 5.1 mEq/kg in the study lambs which was reflected in a rise of serum Na and osmolarity (Osm) during the post-NaHCO3 -infusion period. The extraction ratio of sodium p-aminohippurate (EPAH) and its relationship to arterial pH were studied in 4 additional lambs. The EPAH did not change with metabolic acidosis but for unknown reasons, the infusion of NaHCO3 resulted in a temporary depression of EPAH (p less than 0.001).

Distribution of pulmonary blood flow in fetal and newborn lambs

The distribution of pulmonary blood flow was studied in near-term lambs, using isotope labeled macroaggregated albumin (M.A.A.), before the onset of respiration, during the onset of respiration, and after full inflation. Before the onset of respiration, in 5 animals the comparison of the distribution of M.A.A. particles in the right and left sides (counts/gram of lung tissue) was not statistically different. The median relative activity (% total μc/% total wt) was near 1.0 in each lung for all subjects, and 89.4% and 88.1 % of the right and left lung had a relative activity within ±50% of the mean. Thus, the distribution of blood flow in the fetal lung was nearly symmetrical and uniform. During the onset of respiration, in 2 out of 3 cases, a statistically significant difference between the relative blood flow to the aerated and uninflated regions was found, the distribution of M.A.A. particles being in favor of the aerated regions. Thus, during the onset of respiration the increased blood perfusion and lung inflation were topographically correlated. Following full inflation, the distribution of pulmonary blood flow was again nearly symmetrical and uniform.

Hypersensitivity to pituitary snuff with miliary shadowing in the lungs.

<h3>Objective</h3> Intraosseous access is recommended as a reasonable alternative for vascular access during newborn resuscitation if umbilical access is unavailable, but there are minimal reported data in newborns. We compared intraosseous with intravenous epinephrine administration during resuscitation of severely asphyxiated lambs at birth. <h3>Methods</h3> Near-term lambs (139 days’ gestation) were instrumented antenatally for measurement of carotid and pulmonary blood flow and systemic blood pressure. Intrapartum asphyxia was induced by umbilical cord clamping until asystole. Resuscitation commenced with positive pressure ventilation followed by chest compressions and the lambs received either intraosseous or central intravenous epinephrine (10 μg/kg); epinephrine administration was repeated every 3 min until return of spontaneous circulation (ROSC). The lambs were maintained for 30 min after ROSC. Plasma epinephrine levels were measured before cord clamping, at end asphyxia, and at 3 and 15 min post-ROSC. <h3>Results</h3> ROSC was successful in 7 of 9 intraosseous epinephrine lambs and in 10 of 12 intravenous epinephrine lambs. The time and number of epinephrine doses required to achieve ROSC were similar between the groups, as were the achieved plasma epinephrine levels. Lambs in both groups displayed a similar marked overshoot in systemic blood pressure and carotid blood flow after ROSC. Blood gas parameters improved more quickly in the intraosseous lambs in the first 3 min, but were otherwise similar over the 30 min after ROSC. <h3>Conclusions</h3> Intraosseous epinephrine administration results in similar outcomes to intravenous epinephrine during resuscitation of asphyxiated newborn lambs. These findings support the inclusion of intraosseous access as a route for epinephrine administration in current guidelines.