Postnatal changes of extracellular volume, atrial natriuretic factor, and diuresis in a randomized controlled trial of high-frequency oscillatory ventilation versus intermittent positive-pressure ventilation in premature infants <30 weeks gestation

What Should We Do about Low Blood Pressure in Preterm Infants

The management of preterm infants with low blood pressure soon after birth remains unresolved. The definition of what constitutes low blood pressure is uncertain. At birth, mean blood pressure appears to be gestation specific and increases in the first few days of life. Antenatal steroids, delayed cord clamping, and the avoidance of mechanical ventilation are all associated with higher mean blood pressure and less hypotension after birth. Rates of hypotension of 15-50% have been reported in various studies of extremely preterm infants. However, only about 10% of all extremely preterm infants receive inotropes, suggesting that clinicians take into account other factors such as clinical, biochemical, and echocardiographic findings before deciding to intervene. The exact role of functional echocardiography in assessing the need for treatment of low blood pressure in extremely preterm infants remains to be determined. Near- infrared spectroscopy to assess cerebral perfusion may also have a role to play. Volume expansion (usually 10 mL/kg of saline) remains the most commonly used intervention for low blood pressure but evidence of benefit is lacking and there may be safety concerns. Whilst dopamine is the most commonly used inotropic drug, dobutamine, epinephrine, corticosteroids, milrinone, and vasopressin have also been utilised in preterm infants with low blood pressure. Clinical trials with long-term outcomes are needed to determine the most suitable inotrope and when to use it. Early hypotension differs from late hypotension with regard to cause, treatment, and outcome. A number of recent studies aimed at improving the evidence base for the treatment of early hypotension in extremely preterm infants have been terminated early because of poor recruitment. Currently, the answer to the question of what to do about low blood pressure in preterm infants remains unclear.

Basic principles and practical steps in the management of fluid balance in the newborn

The fluid management of newborn babies can pose many problems. This article discusses the factors that affect fluid balance in the newborn infant, both term and preterm, and the special circumstances of the surgical neonate. The main determinants of management are: (1) an estimation of transepidermal water losses; (2) an awareness of glomerular filtration rate and how this is influenced by age, respiratory distress and medical intervention; and (3) knowledge of tubular function and its maturation and the processes of postnatal adaptation. This knowledge and appropriate monitoring are the mainstay of management of neonatal fluid balance.

High frequency jet ventilation is associated with increased levels of plasma alpha-atrial natriuretic peptide -- a preliminary study

PURPOSE

To determine if high frequency jet ventilation (HFJV) influences the secretion of alpha-atrial natriuretic peptide (alpha- ANP).

METHODS

Sixteen patients undergoing otolaryngeal surgery were studied. Nine patients were subjected to intermittent positive pressure ventilation (IPPV), and seven patients underwent HFJV. Blood samples were drawn for the measurement of plasma alpha-ANP levels and blood gases before anesthesia, and at 30-min after starting either type of ventilation. The study was started at 2:00 p.m., and was completed before surgery. The plasma concentration of alpha-ANP was assayed by radioimmunoassay.

RESULTS

There were no significant differences in mean arterial pressure, heart rate, oxygenation index and PaCO(2) between the two groups. IPPV was not associated with any changes in plasma -ANP levels, whereas HFJV was associated with significantly increased plasma alpha-ANP levels (from 60.0 +/- 5.7 pg x mL(-1) before anesthesia to 112.0 +/- 11.6 pg x mL(-1) after ventilation, P < 0.01). The urine output of the HFJV patients was significantly greater than that of the IPPV patients (P < 0.05).

CONCLUSION

These preliminary results suggest that HFJV is associated with a significant increase in plasma ANP and in urine output in anesthetized patients.