Abstract
Pulmonary aspiration of gastric contents during general anaesthesia can be fatal. A 1956 report identified pulmonary aspiration as the commonest cause of death during general anaesthesia and NAP4 reported similarly in 2011. Major efforts have been made to reduce its incidence. Cricoid pressure (force) was introduced in the 1960s but remains controversial. Recent studies and new techniques have shed further light on the debate. The role of second generation supraglottic airway devices and videolaryngoscopy is also discussed.
The Problem
Pulmonary aspiration of gastric contents during general anaesthesia can be fatal. If acidic liquid or bile is inhaled it can cause pneumonitis with bronchospasm and pulmonary oedema and, less often, if particulate matter is inhaled it can cause airway obstruction or massive atelectasis. Conversely, if no symptoms, signs or hypoxaemia occur within 2 hours of aspiration, respiratory complications are unlikely. In one report, of those patients who aspirated, 64% developed no respiratory sequelae, 20% required ventilation on an intensive care unit (ICU) for > 6 hours and 5% died.
Since a 1956 report identified pulmonary aspiration as the commonest cause of death during general anaesthesia, major efforts have been made to reduce its incidence. The UK Confidential Enquiries into Maternal Deaths (CEMD) was an important triennial national audit that correlated airway management with death from aspiration (Figure 11.1). In the 1950s, during emergency caesarean sections, most aspirations occurred during spontaneous breathing through a face mask. In 1963 CEMD recommended tracheal intubation to protect the lungs. However, in the following 6 years, deaths from aspiration increased 50%, despite intubation being planned in all but one case. Aspiration occurred after induction with thiopentone and suxamethonium during face mask ventilation, before tracheal intubation: cricoid force (cricoid pressure), although first described in 1961, was not used. During the 1970s and 1980s various methods were introduced almost simultaneously: pre-oxygenation, rapid sequence induction and intubation (RSI), cricoid force, antacid therapy, fasting policies and regional anaesthesia. Maternal mortality from aspiration fell with this package of care, but deaths from hypoxaemia with other airway problems increased.
Landmark studies of the 1980s and 1990s reported that the incidence of pulmonary aspiration was 1:4000 during elective general anaesthesia and 1:900 for emergency anaesthesia, with a mortality rate of 1:70,000 for general anaesthetics. In 2011 the 4th National Audit Project (NAP4) (see Chapter 3) reported that pulmonary aspiration remains the commonest cause of death or brain damage from anaesthetic airway complications. Aspiration was responsible for 50% of such deaths and 52% of cases of death or permanent brain damage.
The most frequent cause of aspiration during anaesthesia has changed over the last few decades. In the 1980s and early 1990s before the use of supraglottic airways (SGAs), the trachea was intubated routinely with the aid of neuromuscular blocking drugs. Pulmonary aspiration mainly occurred in emergency cases during induction of anaesthesia, before tracheal intubation or after extubation. Two more recent national audits (NAP4 included 23 cases and the Australian Anaesthesia Incident Monitoring Study (AIMS) in the 1990s included 133 cases of aspiration in the first 5000 incidents) have both shown that the combination of obesity and the use of a first generation SGA, in fasted elective patients, is now the most frequent cause of aspiration.
Avoiding Morbidity from Aspiration
Preoperative Assessment
The NAP4 report pointed out that ‘Poor judgement was the likely root cause in many cases which included elements of poor assessment of risk (patient and operation) and failure to use airway devices or techniques that would offer increased protection against aspiration.’ AIMS suggested universal use of a simple guideline would have prevented 60% of reported aspiration cases. Therefore, when planning airway management during anaesthesia, the anaesthetist should routinely assess both the risks of pulmonary aspiration and airway difficulty.
The risk of pulmonary aspiration should be predicted based on (at least) patient, operation, anaesthesia factors and airway device (Table 11.1). If the operation is an emergency, time from the last ingestion should be confirmed. Factors associated with aspiration in AIMS are shown in Table 11.2. Aspiration risk is in practice a continuous spectrum, which the anaesthetist should then match with an appropriate airway technique.
Patient factors
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Surgical factors
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Anaesthetic factors
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Device factors
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Table 11.2 Risk factors in 133 cases of aspiration
| Aspiration (n.133) | |
| 1 Emergency surgery | 21 |
| 2 Light anaesthesia | 18 |
| 3 Abdominal pathology, acute and chronic | 17 |
| 4 Obesity | 15 |
| 5 Opioid medication preoperatively | 13 |
| 6 Neurological deficit and sedation | 10 |
| 7 Lithotomy position | 8 |
| 8 Difficult intubation/airway | 8 |
| 9 Reflux symptoms | 7 |
| 10 Hiatus hernia | 6 |
From Kluger MT, Short TG. Aspiration during anaesthesia: a review of 133 cases from the Australian Anaesthetic Incident Monitoring Study (AIMS). Anaesthesia 2002; 54: 19–26.
Related posts:
Chapter 4 – Structured Planning of Airway Management
Chapter 6 – Pre-anaesthetic Airway Endoscopy, Real and Virtual
Chapter 15 – Tracheal Tube Introducers (Bougies), Stylets and Airway Exchange Catheters
Chapter 22 – The Airway in Obstetrics
Chapter 31 – Airway Management during CPR
Chapter 26 – Ear, Nose and Throat Surgery: Airway Management
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