Timing of injury in utero causing respiratory inhibition after crying

Neonatal respiratory inhibition

OBJECTIVE

To present information on neonatal respiratory inhibition (NRI) to the medical staff caring for infants.

METHODS

The author reviewed investigations of the above conditions. NRI is defined as severe hypoxemia accompanied by clinical manifestations of central cyanosis and a decrease in SpO₂ to less than 70%. Neonatal respiratory inhibition consists of respiratory inhibition after crying (RIAC), feeding hypoxemia, and respiratory inhibition after gastroesophageal reflux (RIGER). The infants were monitored continuously via pulse oximetry from birth until discharge. To identify the details of NRI, we analyzed detailed notes taken by both parents and medical staff during monitoring using specific software designed to interpret pulse oximetry measurements.

RESULTS

Among infants who weighed at least 2000 g and who were born at a gestational age of at least 36 weeks, NRI was observed in ∼50% of infants, including RIAC in ∼25%, feeding hypoxemia in 40%, and RIGER in 2 ∼ 4%, respectively. Among the infants with NRI, ∼40% experienced one or more episodes of prolonged cyanosis for at least 60 s. RIAC, feeding hypoxemia, and RIGER is significantly associated with each other. Among perinatal factors, NRI was related to maternal diabetes mellitus, twin pregnancy, asymmetric intrauterine growth restriction, threatened premature labor, cesarean section, shorter gestational periods, and abnormal ultrasound findings, including increased echogenicity in the ganglionic eminence (GE), a cyst in the GE, a subependymal cyst, and slight lateral ventricular enlargement. Almost all infants with RIAC and RIGER, even those with severe cases, recovered until discharge around day 5. Despite the provision of nursing guidance in feeding control, ∼60% of infants experienced feeding hypoxemia continuously. The more frequently the infants experienced feeding hypoxemia, the more severe the degree of feeding hypoxemia became. Breastfeeding reduced the frequency and degree of feeding hypoxemia compared to bottle feeding. Approximately 40% of infants with feeding hypoxemia required additional feeding control after being discharged.

CONCLUSIONS

NRI is very common and occurs in many infants worldwide. The infants with NRI experienced repeated severe hypoxemia due to RIAC, feeding hypoxemia, and RIGER after birth. Breastfeeding and careful feeding control should be recommended to mothers of infants with repeated feeding hypoxemia. Spreading knowledge about NRI worldwide is very important.

The prognosis of infants with neonatal respiratory inhibition syndrome

Objective: The goal of this study was to investigate the prognosis of infants with neonatal respiratory inhibition syndrome (NRIS).Methods: Infants with a gestational age of at least 36 weeks and a birth weight of at least 2000 g who were born at Nara Prefecture General Medical Center, in Nara, Japan, between March 2013 and June 2016 were screened for NRIS using our established method. NRIS was defined as severe hypoxemia caused by respiratory inhibition immediately after crying (RIAC) or gastroesophageal reflux (RIGER) or as a respiratory pause during feeding (feeding hypoxemia), accompanied clinically by central cyanosis and a decrease in SpO₂ to less than 70%. All infants were monitored using pulse oximetry immediately after birth. Diagnosis of RIAC, feeding hypoxemia, and RIGER are based on observation by both parents and medical staff as well as on on-screen computer analysis using specific software. All infants were examined at a one-month check-up. Parents of the infants who experienced one or more episodes of NRIS accompanied by a decrease in SpO₂ to less than 70% for more than approximately 60 s received a questionnaire by mail about their child's development. We conducted a logistic regression analysis with developmental problems as the dependent variable.Results: NRIS was observed in 362 (28.5%) infants; 216 (17.0%) infants showed RIAC, 254 (20.0%) infants showed feeding hypoxemia, and 54 (4.2%) infants showed RIGER. Although all infants were monitored in the maternity ward nursery, 184 (85.2%) infants with RIAC and 111 (43.7%) infants with feeding hypoxemia were overlooked. All infants with NRIS were found to have successfully recovered at one month after birth. Sixty-two cases were examined in the follow-up study by the mailed questionnaire. The median age of the subjects at time of study was 22 months. Fourteen cases (22.6%) exhibited developmental problems including delayed speech development, stereotyped interests and behaviors, sensory disturbance, hyperactivity, delayed motor development, and short stature. Developmental problems tended to relate to shorter gestational age (odds ratio, 0.622; p = .068; 95% CI, 0.373-1.036), smaller birth weight (odds ratio, 0.998; p = .069; 95% CI, 0.997-1.000), and maximum duration of SpO₂ to less than 70% by RIAC (odds ratio, 1.009; p = .086; 95% CI, 0.999-1.020). All cases had experienced severe hypoxemia accompanied by a decrease in SpO₂ to less than 60%. Seven cases had experienced prolonged hypoxemia accompanied by a decrease in SpO₂ to less than 70% for at least 2 min. Among the subjects, 19 infants were examined closely, and their natural course of NRIS was observed in the neonatal intensive care unit. No cases demonstrated abnormal findings with blood examinations, chest-abdominal X-ray, echocardiogram, laryngoendoscopy, hearing loss screening, or mass screening. Only one case had a small intracranial hemorrhage as evidenced in a magnetic resonance imaging of the head.Conclusions: The infants with severe NRIS tended to have developmental problems. Spreading knowledge about NRIS worldwide is thought to be very important.

Respiratory inhibition after crying or gastroesophageal reflux and feeding hypoxemia in infants

OBJECTIVE

The objective of this study is to present information on respiratory inhibition after crying (RIAC), feeding hypoxemia, and respiratory inhibition after gastroesophageal reflux (RIGER) to medical staff caring for infants.

METHODS

The author reviewed investigations of these conditions.

RESULTS

These conditions have been observed in full-term healthy infants, and they are accompanied clinically by central cyanosis and a decrease in SpO2 to less than 70%. These conditions are easily diagnosed using pulse oximetry. Among Japanese infants with a gestational age of 36 weeks or older, the incidence of RIAC and feeding hypoxemia is 24% and 32%, respectively. The incidence of RIGER is approximately 4%. Feeding hypoxemia occurs significantly more often during bottle-feeding than during breastfeeding. RIAC, feeding hypoxemia, and RIGER are significantly associated with each other. The risk factors are maternal smoking during pregnancy, threatened premature labor, twin gestation, asymmetric intrauterine growth restriction, and abnormal cranial ultrasound findings. Almost all infants recover from RIAC by day 7 after birth. Some infants with feeding hypoxemia require additional assistance and monitoring by nursing staff until the day of discharge.

CONCLUSIONS

Medical staff caring for infants should note the presence of RIAC, feeding hypoxemia, and RIGER.