Postoperative pulmonary complications

It was an absolute pleasure to attend the recent GAT Annual Scientific Meeting in Glasgow and our congratulations go to all who made it a success. At the ‘Research in Anaesthesia’ session, we discussed what makes a paper popular and the important role of social media in modern academic publishing. The attention a paper receives on social media is something we take very seriously, as it provides instant feedback on likely long-term impact and, more importantly, an opportunity to share and discuss. ‘Impact Factor’ is a more traditionally cited metric, and this month we are delighted to announce a healthy increase in ours to 5.431. Academic anaesthesia is alive and kicking!

Our first article this month is a prospective observational study in 177 patients comparing the diagnostic accuracy of postoperative CXR and lung ultrasound for the detection of pulmonary complications following cardiothoracic surgery. Touw et al. conclude lung ultrasound may detect more clinically-relevant postoperative pulmonary complications than CXR, and at an earlier time point, which may aid more effective clinical decision-making. Though some have called for all such patients to receive lung ultrasound prior to critical care discharge, others urge for caution. We look forward to receiving your lettersand seeing the debate continue.

In November of last year, Bagchi et al. published their retrospective study of 109,360 patients receiving either pressure- or volume-controlled ventilation during surgery. Their study, which reports in favour of VCV, has since attracted much attention. In their editorial, Charlesworth and Glossop argue why they believe the mode of mechanical ventilation is less important than other ventilatory and non‐ventilatory aspects of perioperative care. They also discuss the evidence around postoperative pulmonary complications and their management, and the merits or otherwise of retrospective database analyses (Table 1). Could a similar study in the UK yield the same number of patients and level of detail? Probably not, and so regardless of the inference, their data are of great value to us all.

Table 1.Advantages and disadvantages of retrospective database analyses

The act of delivering a general anaesthetic to patients introduces a number of detrimental physiological processes that predispose to the development of lung damage. Neuromuscular blocking agents (NMBAs) have been suggested as a contributing factor in this regard. Is it possible, therefore, to avoid their use prior to tracheal intubation when using a MAC videolaryngoscope? This study suggests a NMBA free anaesthetic is ‘no worse’ than when such agents are used as regards postoperative laryngeal morbidity and intubating conditions. If you are wondering what is meant by ‘no worse’, make sure you look out for next month’s Statistically Speaking!

It is difficult to study and make sense of the evidence for postoperative pulmonary and other systemic complications due to the variable way in which they, and factors contributing to their development, are defined. In their editorial, Armstrong and Mouton discuss the need for universally agreed definitions for anaesthetic techniques and standardised reporting criteria. For example, how ‘awake’ are patients when they are deeply sedated? This may cause problems for systematic reviewers when retrieving and analysing studies pertinent to ‘awake’ tracheal intubation, but more on that next month.

Sodium-glucose co-transporter type 2 (SGLT2) inhibitors are increasingly prescribed as second line therapy for diabetes mellitus. Recently, there have been a number of published case reports of euglycaemic ketoacidosis related to SGLT2 therapy, and this new review of the peri-operative implications of SGLT2s is, in our opinion, essential reading for all anaesthetists. Though SGLT2s seem to be safe overall, their cessation prior to major surgery, during acute illness, or in a state of volume depletion is recommended. An agent with which we are more familiar is dexamethasone, but is a single anti-emetic dose immunosuppressive or immune-activating? Probably both, concludes this new study in ten healthy male volunteers. Keeping with the peri-operative theme, is it possible to assess physical fitness prior to major surgery in those unable to pedal? This study from Durrand et al. is a significant step forward towards validating arm-crank cardiopulmonary exercise testing as an alternative to pedalling in patients with an abdominal aortic aneurysm.

Acute kidney injury following cardiac surgery is common and associated with significant morbidity and mortality. Many studies have tried to identify protective agents, but this new study is the first network meta-analysis of RCTs comparing these reno-protective drugs in the setting of cardiothoracic surgery. They conclude atrial natriuretic peptide (ANP) and levosimendan are the most protective but advise for cautious interpretation of these findings. Thankfully, Irwin and Choi provide context to this conclusion in their editorial while discussing the wider implications of Bayesian network meta‐analyses in anaesthesia. Though such studies should, in general, be interpreted cautiously, they should also be seen as a powerful tool to ‘flag’ the possibility that certain interventions are more effective than others, as is the case for ANP.

Figure 1 Indirect evidence for A vs. B can be collected if head to head trials exist for A vs. C and B vs. C.

Figure 2Network loops for different drugs. The solid lines show head to head trials, and the dotted lines show evidence which can be collected indirectly. The thickness of the solid lines indicates the number of trials in that comparison.

Elsewhere this month there is a meta-analysis of videolaryngoscopy versus Macintosh laryngoscopy for double-lumen tube intubation in thoracic surgery, a primer on the ethics of teaching and learning in airway management, a qualitative study of human factors enablers and barriers for successful airway management, an in-vitro study of the accuracy of near-patient versus inbuilt spirometry for monitoring tidal volumesand a discussion of NCEPOD at the age of 30.

Over in Anaesthesia Cases, recently published case reports include awake tracheal placement of the Tritube® under flexible bronchoscopic guidance, successful left-sided one-lung ventilation using two Arndt endobronchial blockers in a patient with right tracheal bronchusand sevoflurane for the treatment of refractory status epilepticus in the critical care unit. We want you to send us your interesting cases! Finally, this is the last issue in the current style. Next month, we will have new branding, a new logo and a completely new look journal. We look forward to receiving your feedback!