Clinical Analysis Of Neonatal Respiratory Alkalosis During Mechanical Ventilation

Objective To understand the occurrence of respiratory alkalosis in newborn infants during ventilation and to investigate the underlying causes, adverse effects on newborn infant and preventive measures as well.Methods A retrospective analysis was performed on 90 newborn infants who were once under the ventilation in neonatal intensive care unit (NICU) from January 2005 to June 2010. All infants were divided into respiratory alkalosis group (68 cases) (including pure respiratory alkalosis and double disorder: respiratory alkalosis combined metabolic acidosis, respiratory alkalosis combined metabolic alkalosis) and non-respiratory alkalosis group(22 cases) according to the results of blood gas analysis. The incidence of respiratory alkalosis was compared between different gender, gestational age, birth weight, primary disease, duration of ventilation, infants with or without Pulmonary Surfactant replacement due to neonatal respiratory distress syndrome. And the difference of ventilating parameter setting between two groups was compared also. The underlying causes of respiratory alkalosis were analyzed and logistic regression was applied to identify the high risk factors.Results 1. 68 of 90 infants developed respiratory alkalosis and the incidence was 75.6%. Among 68 cases, 19 (21.1%) infants developed simple respiratory alkalosis , 49 infants developed mixed disorder (22 were of respiratory alkalosis combined metabolic acidosis and 27 were of respiratory alkalosis combined metabolic alkalosis). 25 (36.8%) of all respiratory alkalosis cases had only one blood gas with alkalosis ; Total 469 blood gas results were analyzed and 179 (38.2%) showed respiratory alkalosis. 2. The incidence of respiratory alkalosis was higher in infants with non-respiratory disease than that with respiratory disease (χ2 = 5.775, P <0.05). 3. Higher incidence could be found in NRDS infants who received pulmonary surfactant replacement therapy compared with those without pulmonary surfactant replacement therapy. 4. Average tidal volume (Vt) was significant higher in the group of respiratory alkalosis than non-respiratory alkalosis group (t = 6.868, P <0.05). Logistic regression analysis indicated that Vt is a risk factor for respiratory alkalosis.Conclusion 1. High incidence of respiratory alkalosis occurs in newborn infants during mechanical ventilation, mixed disorders accounted for most of cases. More than one third of respiratory alkalosis are transient. 2. Incidence differs in different primary diseases. 3. NRDS infants are easy to develop alkalosis after receiving pulmonary surfactant replacement therapy because of the improvement of lung compliance. 4. Higher tidal volume contributes to respiratory alkalosis and is regarded as the risk factor.