Silke Lee

Cooling for Newborns with Hypoxic Ischemic Encephalopathy

adverse effects of cooling and ‘early’ indicators of neurodevelopmental outcome. Data Collection and Analysis: Four review authors independently selected, assessed the quality of and extracted data from the included studies. Study authors were contacted for further information. Meta-analyses were performed using risk ratios (RR) and risk differences (RD) for dichotomous data, and weighted mean difference for continuous data with 95% confidence intervals (CI). Main Results: We included 11 randomized controlled trials in this updated review, comprising 1,505 term and late preterm infants with moderate/severe encephalopathy and evidence of intrapartum asphyxia. Therapeutic hypothermia resulted in a statistically significant and clinically important reduction in the combined outcome of mortality or major neurodevelopmental disability to 18 months of age (typical RR 0.75 (95% CI 0.68–0.83); typical RD –0.15, 95% CI –0.20 to –0.10); number needed to treat for an additional beneficial outcome (NNTB) 7 (95% CI 5–10) (8 studies, 1,344 infants). Cooling also resulted in statistically significant reductions in mortality (typical RR 0.75 (95% CI 0.64–0.88), typical RD –0.09 (95% CI –0.13 to –0.04); NNTB 11 (95% CI 8–25) (11 studies, 1,468 infants) and in neurodevelopmental disability in survivors (typical RR 0.77 (95% CI 0.63–0.94), typical RD –0.13 (95% CI –0.19 to –0.07); NNTB 8 (95% CI 5–14) (8 studies, 917 infants). Some adverse effects of hypothermia included an increase sinus bradycardia and a significant increase in thrombocytopenia. Cochrane Abstract

Work of breathing during SIMV with and without pressure support.

Objective: In a randomised trial, pressure support with synchronised intermittent mandatory ventilation (SIMV) compared to SIMV alone was associated with a significant reduction in supplementary oxygen duration. The hypothesis that the addition of pressure support to SIMV compared to SIMV alone would reduce the work of breathing was examined. Design: Prospective study. Setting: Perinatal service. Patients: 20 infants, with a mean gestational age of 31 weeks, being weaned from mechanical ventilation were studied. Interventions: 1 h periods of SIMV and SIMV with pressure support at 50% of the difference between the peak inflating pressure and positive end expiratory pressures. Main outcome measures: The work of breathing was assessed by measurement of the transdiaphragmatic pressure time product (PTPdi). Results: The mean PTPdi on SIMV plus pressure support was 112 cm H2O.s/min, approximately 20% lower than that on SIMV alone (141 cm H2O.s/min) (p<0.001). Conclusion: The addition of pressure support to SIMV reduces the work of breathing in infants being weaned from the ventilator.

Volume-targeted ventilation in infants born at or near term

Objectives To determine the impact of different volume-targeted (VT) levels during volume-targeted ventilation (VTV) on the work of breathing (WOB) of infants born at or near term and to investigate whether a level of VT reduced the WOB below that experienced on respiratory support without VT. Design Prospective crossover study. Patients Sixteen infants, median gestational age of 38 (range 34–41) weeks, birth weight of 3.1 (range 1.5–4.1) kg and postnatal age of 5 (range 2–17) days were studied. The infants were receiving time-cycled, pressure-limited ventilation in a continuous mandatory or in a triggered mode. Interventions The infants were studied first without VT (baseline) and then at VT levels of 4, 5 and 6 ml/kg delivered in a random order. After each VT level, the infants were returned to baseline. Main outcome measure The WOB was assessed by measuring the transdiaphragmatic pressure-time product (PTPdi). Results One infant became apnoeic at VT of 6 ml/kg. At a VT level of 4 ml/kg, four infants were making such vigorous respiratory efforts that no inflations were delivered. The median PTPdi was higher at a VT level of 4 ml/kg than at 5 ml/kg (p<0.01) or 6 ml/kg (p<0.001). Only at a VT level of 6 ml/kg was the median PTPdi lower than that at baseline (p<0.01). Conclusion Low VT levels (4 ml/kg) during VTV increase the WOB in ventilated infants born at term or near term. The results suggest that a VT level of 6 ml/kg could be used to reduce the WOB.

Randomised Trial of Volume-Targeted Ventilation versus Pressure-Limited Ventilation in Acute Respiratory Failure in Prematurely Born Infants

Background: During volume-targeted ventilation (VTV), a constant volume is delivered with each ventilator inflation. Objectives: To determine whether VTV compared to pressure-limited ventilation (PLV) reduced the time to reach weaning criteria in prematurely born infants with acute respiratory distress, and if any difference was explained by better respiratory muscle strength and/or a lower work of breathing (WOB). Methods: Infants of <34 weeks of gestational age ventilated for <24 h in the first week after birth were randomised to receive either VTV or PLV. The primary outcome was the time to achieve pre-specified weaning criteria. Respiratory muscle strength was assessed by the measurement of the maximum inflation and expiratory pressures, and the WOB assessed by the transdiaphragmatic pressure time product. Other outcomes reported are the duration of ventilation, occurrence of patent ductus arteriosus, pneumothorax, intraventricular haemorrhage, periventricular leukomalacia and episodes of hypocarbia. Results: Forty infants, median gestational age 27 (range 23-33) weeks, were recruited. The time taken to achieve weaning criteria was similar in the two groups [median 14 h (VTV) vs. 23 h (PLV)]. There were no significant differences between the groups with regard to respiratory muscle strength, WOB or other outcomes, except that fewer of the VTV compared to the PLV group had episodes of hypocarbia (8 vs. 19; p < 0.001). Conclusion: In prematurely born infants with acute respiratory failure, use of VTV did not reduce the time to reach weaning criteria, but was associated with a reduction in episodes of hypocarbia.

Randomised weaning trial comparing assist control to pressure support ventilation

Objectives To determine if the work of breathing was lower, respiratory muscle strength greater, but the degree of asynchrony higher during weaning by assist control ventilation (ACV) rather than pressure support ventilation (PSV) and if any differences were associated with a shorter duration of weaning. Design Randomised trial Setting Tertiary neonatal unit Patients Thirty-six infants, median gestational age 29 (range 24 to 39) weeks Intervention Weaning by either ACV or PSV. Main outcome measures At baseline, 24 hours after entering the study and immediately prior to extubation, the work of breathing (PTPdi), thoracoabdominal asynchrony (TAA) and respiratory muscle strength (Pimax) were assessed and weaning duration recorded. Results There were no significant differences in the median PTPdi, TAA and Pimax results at any time point. The inflation times during ACV and PSV were similar. The median duration of weaning was 34 (range 7–100) hours in the ACV group and 27 (range 10–169) hours in the PSV group (p=0.88). Conclusion No significant differences were found between weaning by PSV and ACV when similar inflation times were used.

231 A Randomised Trial of Volume-Targeted Versus Pressure-Limited Ventilation in Prematurely Born Infants

Background and aims Meta-analysis of randomised trials (RCTs) demonstrated that volume-targeted ventilation (VTV) in comparison to pressure-limited ventilation (IPPV) reduces BPD/death, pneumothorax, hypocarbia and PVL/grade 3–4 IVH in prematurely born infants. Certain RCTs, however, employed different ventilators in the two arms and, overall, a range of VT levels were used. Our aim was to undertake an RCT in prematurely born infants with acute respiratory distress comparing IPPV with VTV, using a VT level of 5ml/kg, which has been shown to reduce the work of breathing. Methods Infants < 34 weeks of gestational age and < 24 hours of age were recruited. The primary outcome was the time taken to achieve pre-specified weaning criteria. Secondary outcomes included the occurrence of PDA, pneumothorax, IVH, PVL and hypocarbia; hypocarbia was defined as a PaCO 2 of < 4.5 kPa on any blood gas in the first 72 hours after birth. Infants met failure criteria if they required HFO, peak pressures >26 cm H2O or had a pulmonary haemorrhage. Analysis was by intention-to-treat. Results The planned sample size of 40 infants was achieved, with no significant differences in the two groups’ demographics. The time taken to achieve weaning criteria was similar in the two groups [14 hours (VTV) versus 23 hours (IPPV); hazard ratio=0.82 (95% CI 0.42, 1.58)], p=0.55. Five “VTV” and three “IPPV” infants met failure criteria, p=0.69. Fewer “VTV” than “IPPV” infants had hypocarbia (8 versus 19), p<0.001. Conclusion VTV was associated with a significantly lower incidence of hypocarbia.