Management of total intravenous anaesthesia in preterm neonates with bronchopulmonary dysplasia.

Sir,

The authors of the article “Anaesthetic concerns in preterm and term neonates” have done an excellent job and deserve appraisal for their work;[1] we would, however, like to highlight the significance of understanding a possible alternative anaesthetic technique in this population. These patients may suffer from bronchopulmonary dysplasia (BPD), which can lead to a challenge when it comes to meeting respiratory goals. It is of vital importance to understand the use of total intravenous anaesthesia (TIVA) as an alternative to inhalational anaesthesia in patients with pulmonary disease in whom inhaled anaesthesia can be erratic and unpredictable. Management of these neonates is challenging even for the most experienced physicians due to their small size and vulnerability to cardiovascular and respiratory events.[1] Adequate management of these patients is primarily based on avoiding nitrous oxide, providing good levels of oxygenation, consideration of perioperative bronchodilators and strict fluid control.[2] TIVA is a safe alternative in paediatric patients, reducing the risk that is seen with inhaled anaesthesia, thus optimising surgical conditions and reducing postoperative complications.[3] The use of this alternative is not frequent in patients younger than 3 years of age due to the absence of an approved pharmacokinetic model; however, there are recommendations based on the behaviour of intravenous medications in these patients.[3] TIVA can be useful in cases of BPD due to the occasional requirement for high-frequency oscillatory ventilation (HFOV), which is used frequently in this patient population to meet their respiratory needs, but some obstacles exist such as the non-availability of this mode in conventional anaesthesia machines, which prevents the use of inhaled anaesthetics.[4] In these patients, TIVA management becomes essential not only due to the possible requirement of the HFOV but also due to the bronchodilator properties of propofol, making it the induction agent of choice in stable patients with airway hyperreactivity and a viable alternative when the intravenous route is selected.[5] Certain pharmacokinetic considerations must be taken into account when administering propofol to patients younger than 3 years of age, such as the increase in the central compartment and volume of distribution due to a greater percentage of total body water. Therefore, an initial bolus and infusion rate is required in these patients and it is necessary to rapidly decrease the infusion doses until reaching lower maintenance rates than in older patients. This is due to the fact that younger patients have a decreased propofol clearance due to liver immaturity.[3] One must also be aware that there is a lack of monitoring of anaesthetic depth in these patients due to the absence of an approved algorithm for this patient population, which can lead to a delayed awakening from anaesthesia. Thus, there is a discrepancy between the infusion rates used in adult and neonatal patients, which is important to be kept in mind when carrying out this technique depending on the type of patient. Based on this, we can review the infusion scheme proposed by Steur and colleagues[6] [Table 1], which differs from adult schemes due to the factors previously discussed within this article. Steur's model is valuable due to the fact that its use registered few side effects, such as bradycardia, drop in blood pressure and desaturation, which were easily counteracted by routine measures. Steur and colleagues concluded that this dosing scheme provides safe anaesthesia in children under 3 years of age and is therefore a useful tool for TIVA in this population.[6] Remifentanil may also be used as a synergistic agent to provide optimal surgical conditions in usual doses based on the weight of the patient, since its pharmacokinetic properties do not differ greatly with respect to the adult patient, because the activity of plasma cholinesterase remains similar from birth to adulthood.[3] For these various reasons, we believe that it is of vital importance to understand the TIVA alternative and its management in patients with BPD.

Table 1

Steur propofol infusion scheme[6] for children under 3 years of age after a loading dose of 3-5 mg/kg

Time	0-10 min	10-20 min	20-30 min	30-40 min	40-100 min	Remaining time
Propofol dose (mg/kg/h)	25	20	15	10	5	2.5

The authors acknowledge John Wiley and sons for permission to reproduce the infusion scheme

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Nil.

Conflicts of interest

There are no conflicts of interest.