Chapter 16: Perioperative care
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Source: Adapted from King ([90]).
Pre‐operative fasting
Definition
Pre‐operative fasting is defined as a prescribed period of time before a procedure when patients are not allowed oral intake of liquids or solids.
Related theory
General anaesthesia carries the risk of the patient inhaling gastric contents during induction, due to airway reflexes (such as coughing or laryngospasm) or gastrointestinal motor responses (such as gagging or recurrent swallowing) (AAGBI [1]). Aspiration of gastric contents can result in respiratory problems (including aspiration pneumonitis and aspiration pneumonia) or at worst acute respiratory failure and death (Van de Putte et al. [207]). Risk factors for aspiration are outlined in Table 16.4, and Box 16.7 outlines current best practice pre‐operative fasting guidelines for healthy adults undergoing elective surgery.
Table 16.4 Predisposing factors for aspiration under general anaesthesia
| Patient factors | Increased gastric content |
Intestinal obstruction
Non‐fasted
Drugs
Delayed gastric emptying |
| Lower oesophageal sphincter incompetence |
Hiatus hernia
Gastro‐oesophageal reflux
Pregnancy
Morbid obesity
Neuromuscular disease | |
| Decreased laryngeal reflexes |
Head injury
Bulbar palsy | |
| Sex | Male | |
| Age | Elderly | |
| Operation factors | Procedure |
Emergency
Laparoscopic |
| Position | Lithotomy | |
| Anaesthetic factors | Airway |
Difficult intubation
Gas insufflation |
| Maintenance | Inadequate depth |
It is important to be aware that several factors can delay gastric emptying (Van de Putte et al. [207]). These include:
- reduced consciousness level
- systemic opiate therapy
- recent history of difficulty in eating, swallowing or digesting food
- recent history of dyspepsia (heartburn), particularly on lying down or bending over
- upper gastrointestinal surgery
- anxiety
- pregnancy or labour
- abdominal pain
- renal failure
- diabetes.
There are various techniques that can be used to prevent gastric aspiration during the induction period. These include a rapid‐sequence induction/endotracheal intubation technique, or awake endotracheal intubation technique, which may be useful to prevent this problem during the induction of anaesthetic.
Box 16.7
Pre‐operative fasting guidelines
- 6 hours fasting from solid food, provided the last meal is light (refer to local trust guidelines for examples of suitable light meal).
- Sweets, including lollipops, are solid food. A minimum pre‐operative fasting time of 6 hours is recommended.
- Tea and coffee with milk are acceptable up to 6 hours before surgery.
- Clear fluids (those through which newsprint can be read) are acceptable up to 2 hours before (see Box 16.8).
- Patients being fed by nasogastric or gastrostomy tube should have their feed stopped 6 hours prior to surgery and water 2 hours prior to surgery.
- Chewing gum should be avoided on the day of surgery.
- Regular medication taken orally should be continued pre‐operatively unless there is advice to the contrary. Patients can have up to 30 mL of water orally to help them take medication.
The American Society of Anesthesiologists ([14]) has recognized that fasting times may be prolonged due to alterations in the operating list. Some alterations are unavoidable, but patients should be kept informed of changes to the theatre list and those without disorders of gastric emptying allowed to continue drinking clear fluids up to 2 hours prior to rescheduled surgery (Box 16.8) (Powell‐Tuck et al. [165]). Where patients have disorders of gastric emptying or where the theatre time is difficult to ascertain, patients should be offered mouthwashes to keep their mouths moist and intravenous fluids considered if not contraindicated for the surgery being performed (e.g. liver surgery).
Box 16.8
Examples of clear fluids
- Water
- Tea or coffee without milk
- Fruit or herbal tea
- Fruit squash
- Polycal diluted half and half with water
- Fortijuice
- Enlive (clear liquids only)
