Anaesthesia for Pyloromyotomy
Highlights
- Aldosterone causes sodium and water retention by the kidneys in an attempt to restore blood volume. It has effects on the Na+/K+ exchange mechanism causing further potassium loss in the urine, in addition to that lost in gastric secretions, worsening the hypokalaemia. (View Highlight)
- Initially, bicarbonate is excreted in the urine to compensate for the alkalosis caused by hydrogen ion loss from the stomach; this produces alkaline urine. Eventually maintenance of plasma volume becomes the priority and the kidneys excrete hydrogen ions in exchange for sodium and water, resulting in the paradoxical production of acidic urine despite the metabolic alkalosis. (View Highlight)
- metabolic alkalosis can cause respiratory depression and apnoea. This will be aggravated by the CNS depressant effect of general anaesthesia (View Highlight)
- Preterm infants of <60 weeks postmenstrual age are known to be at risk of postoperative apnoea (View Highlight)
- equilibration of CSF pH with plasma pH takes several hours.1 It is possible that plasma pH may have returned to normal whilst the CSF pH remains increased, thereby exerting a respiratory depressant effect; hence all infants should be monitored for apnoea after pyloromyotomy. (View Highlight)
- Pyloric stenosis is a medical, not a surgical, emergency. Patients can safely wait for surgery while they are rehydrated and their electrolyte abnormalities and alkalosis are corrected. (View Highlight)
- Emptying the stomach may be performed by rotating the infant from the supine, to left lateral decubitus, to prone, to right lateral decubitus—aspirating the NG tube in each position. (View Highlight)
- The infant airway is compressible and easily deformed by external pressure. The application of cricoid pressure may make intubation difficult; if not impossible.13 Identification of the cricoid ring is also more difficult than in adults. Cricoid pressure is, therefore, best avoided (View Highlight)
- The onset time [injection to 95% depression of the first twitch of the train-of-four represented as the mean and standard error of the mean (sem)] of atracurium 0.5 mg kg−1 in neonates and infants is 0.9 (0.1) min (View Highlight)