We appreciate the letter submitted by Barik et al. on our case series entitled “Inhaled anaesthetic gas for severe bronchospasm at the emergency department”. We would like to thank the editor for the opportunity to provide our commentary.
This paragraph is to address the first two issues raised by the writer. The anaesthesia conserving device (ACD) has been used in the Intensive Care Unit (ICU) for sedation [ ]. It can deliver inhaled anaesthetic gas without the logistical nightmare of a traditional anaesthetic machine. ACD use in the emergency department (ED) is not entirely novel; there have been many reports on its use for other indications such as refractory status epilepticus [ ], and acute agitation [ ]. We have demonstrated in this case series its use is also feasible for refractory bronchospasm in the ED. In our ED, we have set up the Resuscitation & Critical Care Unit (RECCU) within ED, staffed by emergency physicians and nurses trained in emergency critical care, providing ICU standards of monitoring and care. Delaying critical care therapies while waiting for available ICU or post-anaesthesia care unit (PACU) beds might not have been in the patients’ best interest. A systematic review and meta-analysis by Wilcox and colleagues found that ICU access block was associated with increased in-hospital mortality and longer hospital stay [ ]. There is a great discrepancy in ICU bed availability worldwide; United States reported 35 beds per 100,000 population while most Asian countries have 3 beds per 100,000 population [ ]. Similar to ICU beds, PACU beds are also in high demand. Diverting this resource from high risk surgical patients to unstable medical patients may not be the best strategy in a resource-limited setting.
The next issue is with regards to monitoring for dynamic hyperinflation and consideration of dynamic hyperinflation as the cause of hypotension. For all three patients, the initial clinical findings, bedside lung ultrasound and chest x-rays ruled out pneumothorax. The lung mechanics showed improvement with ACD and there was no other clinical findings that warrant repeat chest x-ray or CT to diagnose pneumothorax while the patient was in ED. We believed the hypotension that developed in case 2 was multifactorial. Inhaled sevoflurane, like intravenous (IV) sedative, can potentiate hypotension in patients with concurrent hypovolaemia and sepsis-induced vasoplegia. His haemodynamics stabilized with IV fluid bolus and IV noradrenaline infusion.
We agree with the writers that the rebound bronchospasm after withdrawal of inhaled anaesthetics is a serious concern. In a case report by Keenan, their patient was weaned safely over 48 h period by decreasing the inhaled sevoflurane concentration by 25% every 12 h [ ]. Exploring the best weaning method for inhaled sevoflurane in bronchospasm is outside the scope of our case series. We believe that this is a good clinical question for future research consideration.
Usage of volatile anaesthetic agents outside of the operating room (OR) has always faced resistance and opposition, and rightly so, due to its environmental and staff safety concerns. In 2005, Sackey et al. reported that personnel exposure to isoflurane with ACD ranges between 0.03 and 0.16 ppm [ ]. This was the first study investigating environmental pollution with ACD. Subsequent studies on isoflurane and sevoflurane have consistently showed a level below 2 ppm in the health workers’ breathing area [ ]. A study reported that similar low level is observed even without a scavenging system [ ]. Any leakage from the flow system is unlikely to be found at a height or breathing level because inhaled anaesthetics is heavier than air. As a perspective, 2 ppm is the environmental level value (ELV) proposed by the American National Institute for Occupational Safety and Health (NIOSH), and it is the lowest set value compared to other developed countries. A review concluded that trace concentration of inhaled anaesthetics is unlikely to be associated with any negative health effects [ ].
The safety profile of ACD stems from several factors. ACD acts as a circulating system, with 90% of the exhaled anaesthetic vapor become condensed on the carbon surface and delivered back to the patient in the next inspiratory cycle. This allows for low concentration of sevoflurane and limit the amount of inhaled anaesthetics flowing into the exhalation port. The addition of a portable scavenging filter called “Fursorb” to the expiratory port of the ventilator prevents the environmental release of remaining exhaled inhaled anaesthetics [ ]. We also took measures not to allow tube disconnection at any time and used closed suction system. To address the possibility of accidental spillage or improper handling of inhaled anaesthetics during ACD set up, we assigned these tasks to few core personnel within our team who have underwent proper training.
We thank Barik et al. again for the interest shown in our case series, and hope that this commentary provides some clarification to the issues raised.
Authors’ contribution
AO, FNA, CPF,NLR, AHA, SF and FAK was involved in the initial conception and drafting of the manuscript. All authors contributed to the image interpretation, writing and revision of the manuscript.
Ethics approval and consent to participate
Ethical approval and consent were taken for this study.
Funding
Authors received no funding for this clinical trial from any institution/ individual.
CRediT authorship contribution statement
Osman Adi: Conceptualization, Data curation, Formal analysis, Writing – review & editing, Writing – original draft. Farah Nuradhwa Apoo: Conceptualization, Data curation, Formal analysis, Writing – original draft, Writing – review & editing. Chan Pei Fong: Conceptualization, Writing – original draft, Writing – review & editing. Azma Haryaty Ahmad: Conceptualization, Data curation, Writing – original draft, Writing – review & editing. Nurul Liana Roslan: Conceptualization, Data curation, Writing – original draft, Writing – review & editing. Faheem Ahmed Khan: Data curation, Conceptualization, Writing – original draft, Writing – review & editing. Shahridan Fathil: Conceptualization, Data curation, Writing – original draft, Writing – review & editing.
Declaration of Competing Interest
The authors declare that they have no competing interests.
Acknowledgements
We would like to thank Ipoh Emergency Critical Care Society (IECCS) and Director of Health, Ministry of Health, Malaysia.
References
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