Intra‐operative cardiac arrest – we need to do better

Intra-operative cardiac arrest is rare but is of considerable concern to anaesthetists, patients and families. A pre-operative survey of 894 patients scheduled to undergo surgery found that the fear of death was the patients' greatest concern, and this fear was greatest among young patients [1]. Many studies have documented the incidence of peri-operative and intra-operative cardiac arrest but the definitions and inclusion criteria vary, making comparisons difficult (Table 1). As well as cardiac arrests occurring intra-operatively, studies of peri-operative cardiac arrest can include cardiac arrests up until discharge from the post-anaesthesia care unit (up to 12–24 h postoperatively) or cardiac arrests occurring any time before leaving hospital. Interpretation is hampered further because some studies include patient cohorts with a high incidence of intra-operative cardiac arrest, such as neonates or those having cardiac surgery. The differing methodologies make it difficult to analyse trends in the incidence and outcome from intra-operative cardiac arrest but the few studies that have reported data from the same location and using similar inclusion criteria have shown a decrease in the incidence rate over time [3-6]. Morais et al. describe the rates of intra-operative cardiac arrest and associated 30-day mortality from 2005 to 2022 at São Paulo State University Teaching Hospital, Brazil [15]. They included all cases requiring the care of an anaesthetist, and therefore included cardiac arrests occurring in several locations outside of the operating theatre. Of the 154,178 cases requiring anaesthesia during the 18-year period there were 297 intra-operative cardiac arrests and 248 (83.5%) patients died by day 30. This represents an intra-operative cardiac arrest rate of 19.26 per 10,000 anaesthetics. Seven intra-operative cardiac arrests were entirely attributable to anaesthesia, equating to a rate of 0.45 per 10,000 anaesthetics. The authors have shown a reduction in the rate of intra-operative cardiac arrest over the 18-year period of study; however, the rate of 15.37 per 10,000 anaesthetics documented in the most recent 6-year period is still high in comparison with many other studies. The 3 in 10,000 incidence of peri-operative cardiac arrest documented in the 7th National Audit Project (NAP7) of the Royal College of Anaesthetists [14], which included patients having a cardiac arrest in the peri-operative period up to 24 h, is substantially lower than the figure from this study from Brazil, particularly given that the latter focused on intra-operative cardiac arrest. The precise definition of 'intra-operative' is unclear and Morais et al. included, for example, patients having a cardiac arrest in critical care while under the care of an anaesthetist. Although differences in inclusion criteria limit the reliability of direct comparisons, some common themes emerge such as a higher incidence in cardiac surgery, vascular surgery, emergency surgery and at the extremes of age. A previous systematic review and meta-analysis has shown that the rate of peri-operative cardiac arrest is strongly associated with a country's human development index (HDI), an index based on per capita income, literacy, life expectancy and enrolment in further education [17]. Human development indices range from 0 to 1 and a score of ≥ 0.8 represents very high development. The systematic review, which compared data from the pre-1990s with the 1990s–2010s, showed that anaesthesia-related and peri-operative cardiac arrest rates were decreasing in high-HDI countries but were increasing and unchanged respectively in low-HDI countries [17]. Another systematic review and meta-analysis similarly reported a decrease in peri-operative mortality using weighted meta-regression in high-HDI countries between pre-1970s to the 2000s [18]. The trend was not present for low-HDI countries. The 2022 HDI for Brazil is 0.760 (ranked 89th in the world), which is substantially lower than the UK figure of 0.940 (ranked 15th in the world) [19]. Another article provides an analysis of the incidence and trends in peri-operative cardiac arrest in Sweden [16], a country that has an HDI of 0.952 (5th highest in the world) [19]. This study included intra-operative cardiac arrests and those occurring in the post-anaesthesia care unit in adult patients from 2013 to 2022. The overall incidence of 2.4 per 10,000 procedures is consistent with that reported by NAP7 [14]. This study also documented a reduction in the incidence of peri-operative cardiac arrest (2.9 vs. 1.8 per 10,000 procedures in 2013 and 2022, respectively) although this was not statistically significant. The 30-day mortality rate following cardiac arrest in this study was 48%. The marked difference between high- and low-HDI countries in the incidence of intra-operative cardiac arrest presumably reflects more highly developed healthcare systems in high-HDI countries and the associated health of the patients undergoing surgery. The peri-operative period generates specific circumstances which result in causes of cardiac arrest that differ from the general in-hospital and out-of-hospital cardiac arrest population (the most common causes of which are hypoxaemia and cardiac, respectively) [20, 21]. The leading causes of peri-operative cardiac arrest reported by Morais et al. were cardiac surgery complications (27%), followed by sepsis (19.5%), ruptured aneurysm (17.4%) and exsanguinating haemorrhage (13.8%) [15]. The NAP7 study identified major haemorrhage (17%) followed by bradyarrhythmia (9%) as the leading causes of peri-operative cardiac arrest; septic shock was the 5th most common cause (7%) [14]. When ruptured aneurysm and exsanguinated haemorrhage are grouped together, the findings of Morais et al. are similar to those of NAP7 and suggest some form of bleeding as the leading cause of peri-operative cardiac arrest. The causes of peri-operative cardiac arrest can be classified according to the primary physiological derangement; for example, abnormalities of preload; contractility; afterload; or rate and rhythm (PCARR) [22]. This PCARR construct has been combined with the Hs and Ts mnemonic to provide a comprehensive framework for identifying the cause of peri-operative cardiac arrest [22]. Survival rates following peri-operative cardiac arrest are higher than those following in-hospital cardiac arrest in other locations [23, 24]. Physiological scores on admission to ICU are significantly better in patients having a peri-operative cardiac arrest compared with those admitted after cardiac arrest elsewhere in the hospital [23, 24]. The peri-operative cardiac arrest patient group is generally less comorbid than patients experiencing cardiac arrest elsewhere in hospital. Patients in the peri-operative period are also likely to benefit from superior monitoring and quicker response times. Unfortunately, survival rates for some patient cohorts are poor. Morais et al. did not report the incidence of frailty but found increased 30-day mortality in older patients and those with increased ASA physical status [15]. An analysis of the American College of Surgeons National Surgical Quality Improvement Program data found higher 30-day mortality rates among patients living with frailty compared with those without frailty (67.4% vs. 55.6%) [25]. In the Swedish registry, the highest rate of peri-operative cardiac arrest was observed in patients undergoing hip fracture surgery, who are more likely to be older and/or living with frailty (up to 53%) [16, 26]. These findings are consistent with those of NAP7 [14] and highlight the need for risk stratification and individualised peri-operative resuscitation planning, particularly in any patient having surgery with a Clinical Frailty Score ≥ 5 [27, 28]. Peri-operative cardiac arrest in association with specific surgical and anaesthetic complications may require treatment outside standard resuscitation guidelines; for example, head-down or left-lateral positioning for gas embolism, advanced airway interventions for airway complications and haemorrhage control alongside transfusion for bleeding [29]. Patients in the operating theatre are more likely to have an advanced airway in situ, continuous monitoring in place (often including invasive arterial blood pressure monitoring) and a clinician with advanced resuscitation skills is likely to be present when cardiac arrest occurs. Thus, cardiac arrest should be identified very rapidly and optimal resuscitation interventions may differ from those recommended in standard guidelines. For example, chest compressions should be started if the systolic blood pressure decreases and remains < 50 mmHg despite interventions, and 50–100 μg intravenous doses of adrenaline are likely to be more appropriate than the standard 1 mg dose for treating a witnessed and monitored intra-operative cardiac arrest [30]. The European Society of Anaesthesiology and Intensive Care and European Society for Trauma and Emergency Surgery have published a consensus guideline for cardiac arrest management in the peri-operative period [29]. The Association of Anaesthetists also includes cardiac arrest in its Quick Reference Handbook [31]. Although the European Resuscitation Council and the Resuscitation Council UK provide some guidance on the treatment of peri-operative cardiac arrest [32, 33], it is not currently a focus for their training courses. Access to the required equipment and personnel does not guarantee successful resuscitation. Human factors have been recognised increasingly as a key component to successful resuscitation. The use of team briefings may enable prospective planning for complications anticipated peri-operatively and promoting open communication enables operating theatre teams to raise concerns early [34]. Familiarity with the environment and equipment locations, as well as the immediate challenges that the environment presents, are important for successful resuscitation. The use of in situ multidisciplinary simulation addresses these issues. Teaching generic cardiac arrest team competencies can improve resuscitation skills performance, quality of cardiopulmonary resuscitation and competencies (leadership, communication, decision-making and task management) [35]. However, to our knowledge, peri-operative cardiac arrest simulation training is not practised routinely. Peri-operative cardiac arrest not only has significant impact on the patient but has a significant and lasting emotional effect on staff involved [36]. Preparing for this rare event with in situ simulation and training would therefore seem sensible and we endorse strongly the recent proposal for mandatory training for rare anaesthetic events including intra-operative cardiac arrest [37]. We recognise that anaesthetists already face a heavy burden of mandatory training, but participation in an annual multidisciplinary in situ intra-operative cardiac arrest simulation exercise surely deserves higher priority than many of the other topics on the current mandatory training list. Although we have some data on short-term outcomes after peri-operative cardiac arrest, we know little about long-term survival and functional outcome, and this warrants research. The Australian and New Zealand Intensive Care Society has recently documented a 60% 4-year survival rate among patients admitted to an intensive care unit after peri-operative cardiac arrest compared with 33% among those admitted after in-hospital cardiac arrest on a ward [24]. Although the decreasing rates of peri-operative cardiac arrest reported by Morais et al. are encouraging [15], the presence of considerable disparity globally is disappointing. Global collaborative education and expanded training programmes along with guideline development may aid that goal. The Ten Steps Toward Improving In-Hospital Cardiac Arrest Quality of Care and Outcomes programme, which is facilitated by the International Liaison Committee on Resuscitation, includes considerations for low resource settings and is a step in the right direction [38]. JN is Editor-in-Chief of Resuscitation and an Executive Committee Member of the Resuscitation Council UK. He was a member of the Royal College of Anaesthetists NAP7 steering committee. No other competing interests declared.