Lessons from the Past – Place of old techniques in Neonatal Anesthesia?

Life is a full circle - it is a very common phrase, reflecting that we arrive where we started from. This also has a different connotation, the concept of Continuity - Never Ending - Eternity. The endpoint for one may be the starting point for another. During life’s journey, as we gain knowledge from constructive reading, teachings of Gurus, and from our experiences, we learn, improve, and move forward from the limited resource status to newer, safer drugs, modern equipment, and techniques, many of which we have forgotten, but do they still have a place in modern-day neonatal anesthesia practice?

Three techniques of the gone by days come to my mind

1. Avoidance of muscle relaxants

2. Maintenance of spontaneous respiration during surgery

3. Extubating under deep anesthesia.

1. Avoidance of muscle relaxants (neuromuscular blocking agents) in neonates - During my postgraduation days, nearly 45 years ago, even at the All India Institute of Medical Sciences, Delhi, anesthesia drugs and techniques available to us were very few. Boon in a way – not difficult to make choices. Bane, in another way, has very limited and narrow options even in critical situations. We had thiopentone, ketamine, atropine, pethidine, ether, halothane, trilene, and cyclopropane (orange cylinders), succinylcholine (scoline), d-tubocurarine and gallamine, oxygen (O₂), and nitrous oxide (N₂O). Except scoline, all drugs had a long duration of action – a disadvantage in critical patients and neonates, where early recovery is hoped for. Often in the emergency, we would have neonates, many of whom did not have an IV line in situ when they arrived at the operating theater (OT). Hence, IV induction was out, and we were scared to use thiopentone, knowing the adverse sequences in case of any extravasation. The only other option was inhalational induction (only halothane is most suitable) with 50–60% O₂ in N₂O, direct laryngoscopy and intubation under deep inhalational anesthesia, avoiding scoline (risk of phase 2 block in neonates). At times, if scoline was used for intubation, its action would be very prolonged, even allowing surgery to be completed. Use of a non-depolarizing muscle relaxant in a neonate for intubation was out of the question. After direct laryngoscopy and intubation with uncuffed red rubber, anesthesia was maintained with continuation of halothane and assisted ventilation (manually), using Ayre’s T-piece circuit. Non-depolarizing muscle relaxants were avoided even during surgery (long duration of action of d-tubocurarine and unpredictable duration of action of gallamine), due to the risk of incomplete or delayed recovery. Avoiding muscle relaxants in this scenario had other benefits – (a) Preserving the baby’s spontaneous respiration, (b) No risk of inadequate reversal, (c) No need for additional drugs for reversal, (d) No need for postoperative ventilatory support, and (e) Faster patient turnover and better OT time usage.

2. Maintenance of spontaneous respiration during surgery had two benefits: (a) Avoiding muscle relaxants and (b) Avoiding effects of positive pressure ventilation in patients who are undergoing transitional changes and adapting to the extrauterine environment.^[1] The neuromuscular junction is poorly developed, and muscle mass is small in neonates, so it is not difficult to overtake their respiratory efforts with assisted ventilation. Keeping in mind the concept of balanced anesthesia, except for a muscle relaxant, drugs to provide amnesia, analgesia, and reflex suppression will be needed. These will depress the medullary centers and abolish spontaneous respiration, especially during thoracic, major, and prolonged surgeries. Most anesthesiologists face this dilemma when providing anesthesia for thoracotomy^[2] and tracheoesophageal fistula repair,^[3,4] abdominal surgeries (congenital diaphragmatic hernia^[5] and gastroschisis^[6]). Hence, even if not using a muscle relaxant, the baby’s respiration would need assistance, which itself may abolish spontaneous efforts. The technique may have some merit, but it deserves constant continuous monitoring for adequacy of gas exchange and maintenance of hemodynamic (HD) parameters intraoperatively, and deep sedation at the end of surgery which may herald safe extubation.

3. Extubation under deep anesthesia – as described above, avoiding muscle relaxants and maintaining spontaneous respiration, will necessarily have a patient very deeply sedated toward the end of surgery, again heralding safe extubation. The extubation criteria include an awake and alert baby, adequate respiration, and O₂ saturation on spontaneous breathing with FiO₂ of 21–30%, stable hemodynamic parameters, with full reflex recovery, and no pain. None of these will be met. Extubation under deep anesthesia would require intense post-operative monitoring and care. Hence, extubating under deep anesthesia is performed, only in selected patients such as those with hyper-irritable respiratory tract, risk of laryngospasm, or any complication during endotracheal tube placement or patient positioning.

How I wish we then had the shorter-acting drugs of today.