Attribution of Delayed Poor Lung Function to Desflurane-Based Balanced Anaesthesia Might be Inappropriate: Our Reply to Sharma et al.'s Article.

Dear Editor,

We read the article by Sharma et al. (1) with great interest. The results are intriguing, and we believe that they have clinical implication in patient management; however, we feel that some aspects need to be clarified before we employ them in clinical practice.

First, all anaesthetic agents have some impact on the pulmonary system, and anaesthesia technique used per-se has minimal impact on the postoperative pulmonary morbidity (2), whereas the mechanical ventilation technique used, parameter settings and the addition of the amount of positive end-expiratory pressure, operative insult, and the patient’s ongoing pathophysiological insults have a significant impact on postoperative pulmonary functional adversities and ensuing increased morbidity (3). In addition to the amount and type of intravenous fluid used, overall fluid balance is a significant predictor (4). Elaboration and clarification of this information will help us better understand and interpret the results.

Second, the conduct of anaesthesia, perioperative analgesia used, perioperative haemodynamics, postanaesthesia recovery, and subsequent rehabilitation have also equally important impacts on the postoperative pulmonary function and morbidity (5). These details are missing in the article, which are critical in the final interpretation of the outcomes. It is now established that improper and inadequate postoperative analgesia contributes hugely to postoperative pulmonary morbidity and can even adversely impact the mortality, especially in elderly patients with pre-existing pulmonary conditions. Although the objective assessment of intraoperative analgesia is not clear and uniform yet, analgesic regimen used in this study was highly different.

Third, for accurate spirometry results, a well-cooperative patient is a prerequisite as most parameters are dependent on patient’s effort. It is well known that patient’s respiratory effort is significantly compromised in the postoperative period due to the ongoing pain and use of sedative and analgesic drugs, which have a significant impact on respiratory function along with ongoing operative insult (6). This possibly impacted the performance of spirometry in the patients. We believe that the authors should have assessed the amount of morphine used, efficacy of pain relief, and sedation score in the postoperative assessment to understand their impact on the performance of postoperative spirometry.

Fourth, it is hypothesised by the authors that the pharmacokinetics and pharmacodynamics of propofol and desflurane are the same. They had discontinued desflurane 3 min before the end of the surgery, whereas propofol was stopped 10 min before. Moreover, nitrous oxide was used in the desflurane group, but not in the total intravenous anaesthesia (TIVA) group. It is established that the use of nitrous oxide impacts postoperative lung collapse and atelectasis process (7).

Although we applaud the authors for their commendable work, and also assume that they indeed observed a significant change in the postoperative pulmonary function in the balanced anaesthesia group compared with TIVA, it is difficult to be convinced of the attribution of such difference to desflurane, which hardly stays for few minutes after discontinuation. This needs introspection and further discussion. Although the clinical significance of any minor reduction in the postoperative pulmonary function in a healthy individual is minimal, it can be significant in obese patients and those having pulmonary comorbidities. Thus, we propose that further study will be required to clarify whether there is any impact of desflurane-based balanced anaesthesia on postoperative pulmonary function, by addressing the issues that we have raised, before we can abandon the use of this novel agent having many clinical advantages, especially the excellent quality of rapid recovery even after prolonged surgery.