A new study ‒ that has examined all cardiac arrests occurring during or soon after surgery in more than 300 UK hospitals over a one-year period ‒ has identified that this extremely dangerous and often fatal event occurs in 3 per 10,000 surgeries requiring anaesthesia.
The study – the 7th National Audit Project of the Royal College of Anaesthetists (NAP7) published in Anaesthesia (the journal of the Association of Anaesthetists) – included data from all NHS hospitals and some in the independent sector and received the support of more than 11,000 anaesthetists throughout the UK. It is likely the largest and certainly the most in-depth study of the nature, causes and consequence of perioperative cardiac arrest, perhaps the complication of surgery feared most by patients, anaesthetists and surgeons. The study included detailed review of more than 900 cases of perioperative cardiac arrest, of which 881 were included in the study.
The two research papers are by an extensive collaboration of anaesthetists across the UK, including Dr Richard Armstrong, Severn School of Anaesthesia and University of Bristol, Bristol, UK, Dr Jasmeet Soar, Consultant in Anaesthesia and Intensive Care, North Bristol NHS Trust, Bristol, UK and Professor Tim Cook, Consultant in Anaesthesia and Intensive Care Medicine, Royal United Hospitals Bath NHS Trust, Bath, UK and Honorary Professor, School of Medicine, University of Bristol, UK. The full report is a collaboration led by the Royal College of Anaesthetists (RCoA) and a full report is also published on the RCoA website.
The authors report the results of the 12-month registry, from June 2021 to June 2022, focusing on epidemiology and clinical features. They reviewed 881 cases of cardiac arrest among an annual caseload of 2.71 million anaesthetics, giving an incidence of 3 per 10,000 anaesthetics – lower than other studies from the USA (5.7 per 10,000) and Brazil (13 per 10,000) had estimated.
Incidence varied with patient and surgical factors. Compared with all surgeries, patients who had cardiac arrest were more frequently male (56%) while only 42% of all surgeries were in men. Increased risk was also shown for the very old and very young: 25% of cardiac arrests occurred in people over 75 years, while only 13% of patients were in this age group; and 8% of cardiac arrests occurred in children aged under 1 year, while only 1% of total patients were in this age group.
Compared with the overall population undergoing anaesthesia, those experiencing cardiac arrest were more often ill or had other significant medical conditions and less often healthy. Patients who were ill or had significant medical conditions (ASA physical status 4–5) accounted for 37% of cardiac arrests but only 4% of the surgical population, whereas healthy patients (ASA physical status 1-2) accounted for 26% of those who had a cardiac arrest and 73% of the surgical population.
Compared with the overall population undergoing anaesthesia, patients who had cardiac arrest were more likely to be undergoing emergency surgery (65% of cardiac arrests occurred during emergency surgery but only 30% of all cases were emergency). Similarly, 60% of the cardiac arrests happened during complex surgery while only 28% of cases were classed as complex. Timing of surgery also mattered: 14% of cardiac arrests occurred during the weekend (Saturday/Sunday), while only 11% of all surgeries were during the weekend; and 19% of cardiac arrests occurred out-of-hours (1801H-0759H), while only 10% of all surgeries were out of hours.
The highest number of cardiac arrests occurred during orthopaedic trauma surgery (12% of all cardiac arrests), major abdominal surgery (10%), cardiac surgery (9%) and vascular surgery (8%). When adjusted for the annual caseload in each specialty, those with the highest risk of cardiac arrest were cardiac surgery (9-fold excess risk), cardiology procedures requiring anaesthetic care (8-fold) and vascular surgery (4-fold).
The most common causes of cardiac arrest were major bleeding (causing 17% of cardiac arrests), very slow heart rate (9%), and cardiac ischaemia (lack of oxygen delivered to the heart) (7%). The authors explored whether the cardiac arrest was due to underlying patient chronic and current ill health or due to anaesthesia or surgery, finding that key factors were the patient’s condition in 82% of cases, anaesthesia in 40% and surgery in 35%. Examples of patient factors include frailty, severe underlying disease and bleeding; examples of surgical factors include complex surgery complicated by bleeding; and anaesthesia examples include a severe allergic reaction to administered drugs.
The authors explain that the study data “highlight a complex interaction of patient, surgical and anaesthetic factors in many perioperative cardiac arrests” also noting that “the cause of cardiac arrest varied widely in different surgical specialties.” The study also showed high rates of senior staff involvement in cases of cardiac arrest.
Reassuringly in healthy (ASA physical status 1) patients undergoing routine surgery, the study showed the rarity of cardiac arrest with this event occurring in fewer than 1 in 10,000 cases and death in 1 in 132,000.
Professor Cook says: “The finding that in more than 80% of all cases, and three-quarters of those occurring at night, a consultant was present during induction of anaesthesia in those cases that had a cardiac arrest suggests efforts to match clinical staffing to patient and case complexity and risk. When a consultant was not present, another senior anaesthetist able to work autonomously was commonly involved.”
Read the paper in Anaesthesia
Source: Association of Anaesthetists
Image: Canva
