Fasting patients before surgery is a well-established practice that prevents the aspiration of gastric contents and reduces the risk of regurgitation and vomiting (Jester and Williams, 1999)
Fasting patients before surgery is a well-established practice that prevents the aspiration of gastric contents and reduces the risk of regurgitation and vomiting (Jester and Williams, 1999) A period of fasting is a legal requirement (Hung,1992) However, the actual length of fasting is determined by the health professionals, which is appropriate given their knowledge of the patient. It is widely acknowledged that patients are being excessively fasted before surgery. (Jester and Williams, 1999) but it is still hospital tradition and custom which dictates the decision. (Seymour,2000) Patients are typically fasted from midnight for morning surgery, and from 6am for afternoon surgery, but a blanket "nil by mouth" fast from midnight on the day of surgery is not only an accepted policy in the UK, but is also a worldwide reality. (Methery, 1996, Pandit and Pandit, 1997) In the past, anaesthetists recommended fasting for at least 8 hours (Shevde and Trivedi, 1991)
If the length of fast is inadequate, a patient may potentially aspirate their stomach contents into their lungs, leading to aspiration pneumonitis, which ovccurs in 1-6 per 10,000 anaesthetics. (Olsson, 1986) According to Mendelsson, (1946) the risk factors associated with aspiration pneumonitis increases when the patient has a gastric volume above 25ml and a gastric pH lower than 2.5. The ideal fasting time would avoid these conditions. Other studies (Hung, 1992, Green, 1996) indicate that extending the fasting time does not achieve this, and indeed may lead to other problems, such as dehydration, electrolytic imbalance, malnutrition and at worse may contribute to post-anaesthetic mortality and morbidity. Psychologically, the excessively fasted patient may become non-compliant and resentful.
Shevde and Trivedi, 1991, concluded that in healthy adults it was safe to induce general anaesthesia two hours from the ingestion of moderate amounts of clear fluids. This was despite the fact that these patients had a pH below 2.5, which Mendelsson said may cause patients aspirate and risk lung damage. They quoted a study by Coombs (1979) which found that patients still had a pH below 2.5 up to 13 hours after starting a fast. A study by Agarwal (1989) also suggested that prolonged fasting might increase a patient's gastric volume, while Maltby (1986) found that administering ...
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Shevde and Trivedi, 1991, concluded that in healthy adults it was safe to induce general anaesthesia two hours from the ingestion of moderate amounts of clear fluids. This was despite the fact that these patients had a pH below 2.5, which Mendelsson said may cause patients aspirate and risk lung damage. They quoted a study by Coombs (1979) which found that patients still had a pH below 2.5 up to 13 hours after starting a fast. A study by Agarwal (1989) also suggested that prolonged fasting might increase a patient's gastric volume, while Maltby (1986) found that administering of 150ml of water two hours before surgery was effective in lowering gastric volume and raising pH in most patients.
Smith (1997) suggests that allowing patients to drink up to 2 hours before surgery reduces the risk of post-operative vomiting, and Palazzo and Strunin (1984) found that a substantial number of patients felt sick after fasting for 8 hours, and many found it difficult to resume normal eating habits after surgery due nausea and vomiting and so became undernourished and dehydrated. This implies that an extended fast can lead to an increase in post-operative emesis.
Even before surgery, a fasting patient can become dehydrated quickly, since an average adult requires 2.5 litres of fluid daily just to replace the volume lost through urination (1.5 litre), the skin, (600ml) and the lungs (400ml) Lee et al, 1996) The dehydrated patient may be subject to electrolyte imbalances, tachycardia, hypotension, oliguria, decreased levels of consciousness, and confusion. (Goode, 1985)
Jester and Williams (1999) concluded that patients were being fasted according to tradition rather than research. Chapman (1996) found that fasting times were often used to accommodate a wide range of theatre list times, to compensate for delays or changes, the number of which were often over-estimated by nurses and anaesthetists.
For elective patients, Maltby (1986) and Sutherland (1987) advocate a fasting time for clear liquids of 2 - 3 hours. Nygen et al, (2001) recommend giving a 50ml carbohydrate drink 90 minutes before elective surgery. Their studies show complete gastric emptying of this drink within 90 minutes. This liquid will also reduce post-operative insulin resistance as well as improving a patient's pre- and post-operative well-being.
The Nursing and Midwifery' Council's "Code of Professional Conduct" (2002)directs nurses to "promote the interests of patients" (2.4) and states that a registered nurse "must protect and support the health of individual patients" (1.2). Further, the Code says a nurse has a duty to "deliver care based on current evidence, best practice and, where applicable, validated research when available" (6.5) Currently practice in fasting appears to be based on custom and tradition, and an attempt to accommodate theatre list changes, rather than the what is best for the patient.
References -
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