Effect of positive end-expiratory pressure during anaesthesia induction on non-hypoxic apnoea time in infants: A randomised controlled trial.
Aim
Evaluate the effect of positive end-expiratory pressure (PEEP) during anaesthetic induction on non-hypoxic apnoea time in infants
Study Design
Single centre RCT in a tertiary paediatric hospital.
Methods
“Normal” infants <1yr age (no neonates, difficult airways etc).
Standardised GA (IV induction, SV with sevoflurane in 100% O2 followed by NMB over 2 minutes.)
100% oxygen was provided via face mask with volume-controlled ventilation (6ml/kg) via facemask with zero PEEP in the control group vs. +7cmH2O PEEP in the intervention group. After 3 minutes the patient was intubated but left disconnected from the breathing circuit and ventilation resumed when pulse oximetry reached 95%.
Primary outcome: non-hypoxic apnoea time (time for SpO2 to fall to 95%).
Secondary outcome: incidence of significant atelectasis as assessed by lung ultrasound (consolidation score ≥2). Lung US was performed by an experienced operator in a standardised manner over 12 lung regions (right/left, upper/lower, anterior/lateral/posterior), looking for evidence of consolidation and B-line scores (see article).
Results
Data from 60 patients was analysed.
Non-hypoxic apnoea time was significantly longer in the +7cmH2O PEEP group: 105s vs. 92s, p=0.011, mean difference 13s (3.1-22).
Overall Lung US Score (LUS) significantly better (lower LUS) in +7cmH2O PEEP group: 20 v 31.6, p<0.001.
Consolidation scores lower (better) in the +7cmH2O PEEP group: 20 v 30, p=0.001; with greatest areas of consolidation noted in the posterior areas in both groups.
Regression analysis was stated to show that age and total LUS correlated with apnoea time in all patients.
Comments/Discussion
It would be reasonable to conclude that the prolonged non-hypoxic apnoea time demonstrated in the intervention group occurred as a consequence of decreased atelectasis secondary to the use of PEEP.
We know that small infants are more prone to hypoxia during anaesthesia and that difficult inductions and/or intubations are associated with an increased incidence of hypoxaemic complications. It would therefore seem appropriate to recommend the routine use of PEEP during induction and intubation although the best level of PEEP for each age group cannot be answered by this study.
Interestingly the study design may have contributed in several ways to the production of atelectasis and potentially reduced the difference in atelectasis measurement and subsequent apnoea time between groups. Firstly, induction was performed using 100% O2 which is known to contribute to atelectasis. Secondly, it appears that no PEEP was added during the induction and onset time (2 minutes) allowed for the relaxant to take effect. This may have allowed significant atelectasis to have already occurred in both groups before the 7cmH2O PEEP was applied to the treatment group. This is supported by the finding of significant atelectasis, particularly in posterior lung areas, in both groups following the subsequent 3-minute time period. It is common practice amongst many anaesthetists to choose an inhalational induction in infants and achieve IV access once consciousness has been lost. The results of this study would support the early and routine use of PEEP during this process, not only to improve the child’s airway but to help prevent atelectasis and subsequent hypoxaemia.
Reviewed by H. Hack
