Adequacy of Preoperative Resuscitation in Laparoscopic Pyloromyotomy and Anesthetic Emergence.
This retrospective study has sought to explore the association between the preoperative serum bicarbonate level and anaesthetic emergence time in infants undergoing laparoscopic pyloromyotomy for pyloric stenosis.
Pyloric stenosis, when left untreated, is associated with dehydration and a hypochloremic, hypokalemic metabolic alkalosis which may be associated with reduced ventilatory drive and post- operative apnoeas.
In this study, serum bicarbonate values were measured at admission and then immediately prior to surgery. Preoperative fluid resuscitation was as per hospital protocol with 5% dextrose in 0.45% saline with normal Saline boluses to correct serum bicarbonate levels >30 mEq/L.
Anaesthetic regimen for the study was a propofol IV induction followed by sevoflurane maintenance and postoperative extubation in the operating room. With regards to neuromuscular blockade and neostigmine reversal, they were grouped into 3 categories: Succinylcholine only, Rocuronium +/- Succinylcholine with reversal before or at emergence, Rocuronium +/- Succinylcholine with reversal after start of emergence. This was to account for the effects of neuromuscular blockade on emergence, as some patients having received Rocuronium were not suitable for neostigmine reversal at the start of anaesthetic emergence. 6.8% of the patients also received opioids intraoperatively.
529 infants over a 4.5 year period were included in the analysis with a median weight of 3.9 kg and median chronological age of 4 weeks. 12.5% of the infants were preterm. Median admission and pre-operative bicarbonate levels were 26 and 25 mEq/L respectively. Only 7.2% of the patients had serum bicarbonate levels >30 mEq/L. Median emergence time and out of OR (OOR) time was 12 and 13 minutes respectively.
After adjusting for confounding variables, it was estimated that each 1 mEq/L increase in serum bicarbonate levels was associated with an increase in median emergence time of 49 seconds. If the preoperative serum bicarbonate was > 30 mEq/L, this correlated with a 5.4 minute increase in the median emergence time. There was a statistically significant positive correlation between a high serum bicarbonate level (≥24 mEq/L) and time to extubation in infants undergoing laparoscopic pyloromyotomy.
Take home message:
Metabolic alkalosis may significantly impair respiratory function during the perioperative period in infants with pyloric stenosis. Given this, correction of alkalosis to a serum bicarbonate level < 30 mEq/L decreases the likelihood of postoperative apnoeas. The altered ventilatory response secondary to metabolic alkalosis appears to be correctable with adequate fluid resuscitation preoperatively. These findings emphasize the need to recognise the potential for perioperative respiratory depression in these infants and modify practice accordingly. This was however a retrospective study. Due to the nature of data monitoring on the electronic record at 1 minute intervals, a precision measurement of emergence time was not possible. The subgroup of patients with serum bicarbonate levels >30 mEq/L was likely statistically underpowered.
Reviewed by Dr Priya Sreedharan