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Anaesthetists Highlight Potential Risks During Procedures

Updated: Nov 14, 2023


Potentially serious complications occurred in one in 18 procedures under the care of an anaesthetist in UK hospitals, according to a national audit by the Royal College of Anaesthetists (RCA).


Risks were found to be highest in babies, males, patients with frailty, people with comorbidities, and patients with obesity. Risks were also associated with the urgency and extent of surgery and procedures taking place at night and/or at weekends.


The survey, published in Anaesthesia, was the RCA's seventh national audit project (NAP7) and included more than 20,000 procedures at over 350 hospital sites. NAPs study rare but potentially serious complications related to anaesthesia, and are intended to drive improvements in practice. Each focuses on a different topic and NAP7 examined perioperative cardiac arrest.


Higher Complication Rate During Emergency Surgery

First author Dr Andrew Kane, consultant in anaesthesia at James Cook University Hospital in Middlesbrough and a fellow at the RCA's Health Services Research Centre in London, said the new data presented "the first estimates for the rates of potentially serious complications and critical incidents observed during modern anaesthetic practice". The data confirmed that individual complications are uncommon during elective practice, but highlight the relatively higher rate of complications in emergency settings.


As part of NAP7, the survey team asked anaesthetists to participate in an online prospective study recording anonymous details of all cases requiring general, regional, or local anaesthesia, sedation, or monitored anaesthesia care undertaken at their site over 4 days.

Of 416 hospital sites invited to participate, 352 (85%) completed the survey, with a total of 24,172 cases, among which 1922 "discrete potentially serious complications" were reported during 1337 (6%) cases. As obstetric cases had a high reported major haemorrhage rate, they were excluded from further analysis.


In the remaining cohort of 20,996 nonobstetric cases, 1705 potentially serious complications were reported during 1150 (5.5%) procedures. These were single complications in 851 (4%) cases, two complications in 166 (1%), and three or more in 133 (1%). Complications were categorised as:

  • Circulatory, eg, severe hypotension or arrhythmias – 616 (36%)

  • Airway, eg, low oxygen levels – 418 (25%)

  • Metabolic – 264 (15%)

  • Breathing-related, eg, ventilation difficulties – 259 (15%)

  • Other – 107 (6%)

  • Neurological – 41 (2%)

Elective Surgery Complications "Uncommon"

Complications of nonobstetric elective surgery were "uncommon", the team said, with a rate of 10 to 100 per 10,000 cases. In contrast, emergency surgery (urgent and immediate) accounted for 3454 (16%) cases but 714 (42%) complications, with severe hypotension, major haemorrhage, severe arrhythmias, septic shock, significant acidosis, and electrolyte disturbances all "common", with a rate of 100 to 1000 per 10,000 cases.


Univariate analysis showed that risk factors for complications included:

  • Neonates (aged less than 28 days) – 18%, 3.8 times higher risk than young adults (19-25 years, 4.7%)

  • Older ages:

    • Adults aged 66-75 – 6.0%, 28% higher risk than young adults

    • Adults aged 76-85 – 6.1%, 30% higher risk

    • Adults aged over 85 – 5.7%, 21% higher risk


  • Higher comorbidity by American Society of Anesthesiology (ASA) physical status, ASA 4 (major comorbidities) – 19%, 5.5 times higher than ASA1 (fit and healthy, 3.5%)

  • Males – 6.4%, 40% higher than females (4.7%)

  • Frailty – 8.5%, double the risk for nonfrail patients (4.5%)

  • Immediate emergency surgery (life, limb, or organ-saving intervention simultaneous with resuscitation) – 39%, 10 times higher than elective surgery (4%) and four times the risk of urgent emergency operations (intervention for acute onset or clinical deterioration of potentially life-threatening conditions, 8.8%)

  • Complex major surgery (eg, bowel resection for cancer) – 9%, 2.5 times the risk for minor surgery (eg, skin lump removal, 3.4%)

  • Night-time surgery – 20%, four times the risk of daytime operations (5%)

  • Weekend surgery: Sunday – 10% – or Saturday – 6.5%, double and 30% higher, respectively, than operations on weekdays (5%)


Risk Factors Often Occur Together

The authors pointed out that these comparisons were univariate, whereas, generally, factors interact – for example, at night and over weekends, only the most urgent cases receive surgery, and these will often involve older, frail, and comorbid patients. Similarly, almost all neonatal surgery is urgent and major, which in part, accounts for the higher rate of complications.


Co-author Dr Jasmeet Soar, consultant in anaesthesia and intensive care medicine at Bristol's Southmead Hospital, said that patients generally were older, had more comorbidities, and were more likely to be obese compared with a decade ago. All these factors "make undergoing anaesthesia and surgery intrinsically more hazardous".


The authors concluded: "These data represent the rates of potentially serious complications during routine anaesthesia care and may be valuable for risk assessment and patient consent."


Commenting on the report, Dr Fiona Donald, president of the Royal College of Anaesthetists, said: "The more we understand about which patients are at greater risk of complications and the reasons for that, the better equipped we are to make further improvements in perioperative care, and this study takes us a long way along that road of understanding."


Full results from NAP7 are due to be published next week, and analysis of the obstetric cases will be the focus of a separate paper.

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