What is NAP4 and Its Use in Anesthesia
NAP4 (the Fourth National Audit Project of the Royal College of Anaesthetists and Difficult Airway Society) is a landmark prospective audit that identified the incidence, causes, and preventable factors in major airway complications across the UK, fundamentally reshaping airway management practice by revealing that serious complications occur at a rate of approximately 1 in 5,500 general anesthetics, with particularly high mortality in ICU and emergency department settings. 1, 2
Primary Purpose and Scope
NAP4 was designed to capture all major airway complications occurring over a 12-month period (beginning September 2008) that resulted in:
- Death
- Brain damage
- Emergency surgical airway (front of neck access)
- Unanticipated ICU admission
- Prolonged ICU stay 1, 3
The audit collected 184 cases meeting inclusion criteria, including 38 deaths, making it the largest audit of serious airway complications in world literature. 3, 1
Key Findings That Drive Current Practice
Location-Specific Risk Stratification
- Operating theatres, ICUs, and emergency departments were all studied, revealing that at least one in four major airway events occur outside the operating room. 1
- ICU and ED events were significantly more likely to occur out-of-hours, be managed by less experienced clinicians, and result in permanent harm—with 61% of ICU events and 31% of ED events leading to death or persistent neurological injury. 1
- The outcome of airway events in ICU was roughly 60-fold higher for death and brain damage compared to operative anesthesia. 3
Critical Timing of Complications
- Approximately one-third of major complications occurred during emergence, extubation, or recovery—not at induction. 3
- This finding directly led to the development of dedicated extubation guidelines, as this phase had been largely ignored in previous guidance. 3
Aspiration as Leading Cause of Death
- Aspiration was responsible for 26% of life-threatening complications and 50% of all deaths. 2
- Eight deaths resulted specifically from aspiration of gastric contents, making it the single most common cause of death in anesthesia-related events. 3
- The majority of aspiration events occurred during maintenance (often with inappropriate supraglottic airway use) or extubation, rather than at induction. 3
Obesity as Major Risk Factor
- Airway problems were twice as common in obese patients (BMI 30-35) and four times as common in morbidly obese patients (BMI >35). 2
Identified Gaps in Care (Repeated Themes)
NAP4 revealed systematic failures across multiple domains:
Assessment and Planning Failures
- Airway assessment was not recorded before surgery in 74% of patients who developed life-threatening complications. 2
- Poor identification of at-risk patients was a recurring theme. 1
- Inadequate or incomplete planning when difficulty was anticipated. 3, 1
Equipment and Monitoring Deficiencies
- Failure to use capnography contributed to 74% of cases resulting in death or persistent neurological injury. 1
- Inadequate provision of skilled staff and equipment to manage emergencies successfully. 1
- Delayed recognition of deteriorating events. 1
Clinical Judgment Issues
- Issues with judgment or education/training were considered relevant in 62% and 47% of cases, respectively. 3
- Airway management quality was assessed as good in only 16% of cases, mixed in 43%, and poor in 35%. 3
- Awake fiberoptic intubation was indicated but not performed in a significant number of reported incidents. 2
Direct Impact on Guidelines and Practice
NAP4 generated 167 specific recommendations divided into three levels: 3
- Institutional recommendations
- Departmental recommendations
- Individual practitioner recommendations
Guidelines Developed in Response to NAP4
Critical care intubation guidelines were created as a direct response to NAP4 findings, recognizing that critically ill patients have the highest complication rates yet had minimal specific guidance. 3
Extubation guidelines were developed because NAP4 revealed that 30% of serious complications were associated with extubation or laryngeal mask removal. 3, 2
Tracheostomy emergency guidelines were formalized following NAP4's spotlight on airway management complications, incorporating the multi-disciplinary approach NAP4 emphasized. 3
Practical Applications for Clinicians
Mandatory Documentation
- Record airway assessment before every case, as failure to do so was present in nearly three-quarters of major complications. 2
Equipment Standards
- Ensure capnography is available and used universally—its absence contributed to the majority of deaths and brain injuries. 1
- Maintain standardized difficult airway equipment readily accessible in all locations where airway management occurs. 3
High-Risk Patient Identification
- Apply heightened vigilance for obese patients (2-4× increased risk). 2
- Recognize that patients with head and neck pathology featured disproportionately in complications. 3
Extubation Planning
- Develop a specific extubation strategy before starting anesthesia, not as an afterthought. 3
- Recognize that extubation carries equal or greater risk than intubation in many scenarios. 3
Aspiration Prevention
- Maintain rapid sequence induction with cricoid force as the standard for at-risk patients, despite NAP4 showing it doesn't provide 100% protection. 3
- Recognize that most aspiration occurs during maintenance or emergence, requiring vigilance throughout the case. 3
Common Pitfalls Revealed by NAP4
- Assuming operating room standards apply elsewhere: ICU and ED have fundamentally different risk profiles requiring adapted approaches. 1, 3
- Focusing solely on intubation: One-third of major events occur at extubation/emergence. 3
- Relying on experience alone: Senior, experienced clinicians were involved in most events, indicating that experience doesn't eliminate risk. 2
- Inadequate out-of-hours preparation: Complications were more likely during off-hours when resources and expertise may be limited. 1