New NANN Practice Guideline: the management of hypotension in the very-low-birth-weight infant

Association between dopamine and cerebral autoregulation in preterm neonates

BACKGROUND

To test the hypothesis that dopamine is associated with impaired cerebral autoregulation (ICA) in a dose-dependent fashion.

METHODS

Non a priori designed secondary analysis of a prospectively enrolled cohort study subjects <12 h of life between 24⁰ and 29⁶ weeks gestation. Cerebral saturations (rScO2) and mean arterial blood pressure (MAP) were continuously monitored every 30 s for 96 h. ICA was defined by a 10 min epoch rScO2-MAP correlation coefficient of >0.5.

RESULTS

Twenty-three of 61 subjects (38%) required dopamine. Time spent with ICA was 23% in dopamine-exposed subjects vs. 14% in those not exposed (p = 0.0001). On the epoch level, time spent with ICA was 15%, 29%, 34%, 37%, and 23% in epochs with dopamine titration of 0, 1-5, 6-10, 11-15, and 16-20 μg/kg/min, respectively. Using mixed-effect modeling, ICA for each dopamine titration was significantly higher than unexposed times when controlling for gestation, presence of a patent ductus arteriosus, day of life, MAP less than gestational age, and illness severity score (p < 0.02).

CONCLUSIONS

Dopamine exposure during the first 96 h was associated with ICA. Time periods with ICA increased with dopamine exposure in a dose-dependent fashion peaking at a concentration of 11-15 μg/kg/min.

A polymorphism in the glucocorticoid receptor gene is associated with refractory hypotension in premature infants

BACKGROUND

Glucocorticoids play an important role in endocrine control. The association of glucocorticoid receptor (GR) gene polymorphisms with altered sensitivity to glucocorticoid therapy has been reported in adults. However, there are few such reports in infants. The present study analyzed the prevalence of four GR polymorphisms in preterm infants born before 30 weeks of gestation and determined the associations between these polymorphisms and clinical outcomes in the infants.

METHODS

Totally, 41 preterm infants born at two hospitals in Fukushima were retrospectively screened for the presence of four GR gene polymorphisms, using a TaqMan single-nucleotide polymorphism genotyping assay. The effect of GR gene polymorphisms on clinical outcomes during hospitalization was evaluated. The following primary clinical outcomes were assessed: refractory hypotension in the acute phase and/or severe bronchopulmonary dysplasia, maximum dopamine and dobutamine doses administered, and total hydrocortisone dose administered in the first 48 h of life. Multivariate analysis with logistic regression was used to assess the association between clinical factors and refractory hypotension.

RESULTS

Of the four GR polymorphisms, only the BclI polymorphism was detected. The genotype distribution was as follows: C/C, 33; C/G, 8; and G/G, 0 infants. Significant differences were observed between the C/C and C/G genotypes with respect to the following variables: refractory hypotension (6% vs. 50%), dopamine dose [3.0 (2.0-4.0) vs. 4.8 (4.0-7.5) μg/kg/min], dobutamine dose [2.4 (0.0-3.6) vs. 4.0 (0-10.0) μg/kg/min], and total hydrocortisone dose administered in the first 48 h of life [2.0 (0-10.0) vs. 6.0 (0-12.0) mg/kg]. Multivariate analysis showed that the BclI genotype (C/C) was significantly less associated with refractory hypotension in the acute phase (odds ratio, 0.008; 95% confidence interval, 0.000-0.371; p = 0.013).

CONCLUSION

The incidence of refractory hypotension in infants with the C/C genotype was initially expected to be higher than that in infants with the C/G genotype. However, the results of this study were rather different from what we originally expected. The suppressive effect of antenatal steroid use on the HPA axis of the preterm infants with the BclI variant may be associated with refractory hypotension in the acute phase.

Dopamine therapy is associated with impaired cerebral autoregulation in preterm infants

AIM

Hypotension is a common problem in newborn infants and is associated with increased mortality and morbidity. Dopamine is the most commonly used antihypotensive drug therapy, but has never been shown to improve neurological outcomes. This study tested our hypothesis that dopamine affects cerebral autoregulation (CA).

METHODS

Near-infrared spectroscopy was used to measure the cerebral oxygenation index in 60 very preterm infants, and mean arterial blood pressure was monitored towards the end of their first day of life. Measurements were performed continuously for two to three hour periods. CA was quantified as the cerebral oximetry index (COx).

RESULTS

We treated 13 of the 60 infants (22%) with dopamine during the measurements. COx was higher in the dopamine group than the untreated group (0.41 ± 0.25 vs. 0.08 ± 0.25, p < 0.001). Blood pressure tended to be lower in the dopamine group, but the anticipated difference in cerebral oxygenation was not detected. The need for mechanical ventilation in the first day of life and incidences of mortality was higher in the dopamine group.

CONCLUSION

Dopamine therapy was associated with decreased CA in preterm infants. We were unable to determine whether dopamine directly impaired CA or was merely an indicator of illness.