This Invited Commentary accompanies the following article:
Harsten A, Hjartarson H, Toksvig-Larsen S. Total hip arthroplasty and perioperative oral carbohydrate treatment: a randomised, double-blind, controlled trial. Eur J Anaesthesiol 2012; 29:271–274.
In this issue of the journal, an interesting article by Harsten et al.1 is published. The authors compared a group of patients who had been given carbohydrate solution and a group of patients who had been given flavoured water (placebo group) 90 min before induction of anaesthesia and again 2 h after the end of surgery. They found no statistically significant difference between the two groups of patients regarding length of stay in hospital, anxiety, headache or thirst.
Overnight fasting before surgery has unfortunately been a part of the standard hospital protocol in many hospitals all over the world, and is almost a doctrine. However, preoperative overnight fasting, which is still a rule that is adhered to in many European countries, has no scientific foundation.2 The idea of avoiding preoperative overnight fasting comes from research which considered the importance of maintaining stability of metabolism during the perioperative period. These initial ideas were followed by animal studies in which rapid consumption of glycogen reserves during a short period of fasting has been documented.3 The loss of skeletal muscle caused by overnight fasting is partly due to gluconeogenesis.4 Awad et al.5 reported that mitochondrial dysfunction after a short period of fasting was a possible cause of insulin resistance in the postoperative period.
An intravenous infusion of carbohydrate solution during the night before surgery resulted in a decrease in insulin resistance in comparison with an untreated group.6 Shortly afterwards, clinical scientists started to give carbohydrate solutions orally to patients the night before surgery and the overall satisfaction of the patients was improved.7 Kaska et al.8 compared patients who had been given carbohydrate solutions by the intravenous or oral route, and there was a clear benefit in terms of satisfaction and well-being during the perioperative period among those who had received solutions orally. In August 2011, the European Journal of Anaesthesiology published guidelines for perioperative fasting in adults and children which made a strong recommendation in favour of preoperative feeding of patients with clear fluids up to 2 h before surgery.9 The intake of clear fluids 2 h before elective surgery has many benefits for the patient, such as satisfaction with preoperative treatment, less thirst and hunger and a reduction in insulin resistance during the postoperative period. These guidelines included obese patients, diabetics, patients with gastro-oesophageal reflux and pregnant women not in labour.
However, how can we be sure that patients have an empty stomach 2 h before surgery and that there is no risk of regurgitation during induction of anaesthesia? Yagci et al.10 analysed the pH and volume of gastric fluid at the beginning of surgery and found no statistically significant differences between patients who drank carbohydrate solution 2 h before surgery and those who had fasted overnight. This observation indicates that there is the same risk for the aspiration of gastric contents during induction in anaesthesia in both groups. By choosing spinal anaesthesia, it is often assumed that there is no risk of aspiration of gastric contents, but we have to be aware of the frequent need for sedation and rescue analgesia of such patients during surgery due to insufficient spinal anaesthesia or prolonged surgery.
Some anaesthetics and analgesics given to patients in the perioperative period can cause potential problems regarding gastric emptying. Opioids can inhibit gastric emptying, even in small doses.11 Lydon et al.12 showed that spinal anaesthesia with the local anaesthetic bupivacaine decreases gastric emptying during the early postoperative period. A decrease in the rate of gastric emptying can delay the resumption of feeding after surgery, and it can result in an increase in residual volumes of gastric fluid, thereby increasing the risk of vomiting and nausea.12 Lobo et al.13 measured the gastric emptying time after ingestion of carbohydrate solution using MRI and found no solution in the stomach after 120 min. This study is further evidence that carbohydrate solution could be an appropriate choice for preoperative feeding. Although spinal anaesthesia can decrease gastric emptying in the early postoperative period, carbohydrate solution given orally 2 h before surgery has no influence on the gastric emptying rate in the same patients.14
It has been shown in animal models that the integrity of the small intestine barrier is maintained and that reduced bacterial translocation occurs in animals fed with carbohydrate compared to animals which had been fasted.15 Therefore, we can assume that overnight fasting before surgery could lead to ischaemic-reperfusion injury of the small intestine. The return of bowel motility is one of the reasons for a shorter length of stay in hospital after surgery.16 Ren et al.17 used the Enhanced Recovery After Surgery protocol for patients who underwent radical bowel resection for colorectal carcinoma and reported a reduced stress response from surgery and better postoperative recovery with no risk for the patient. Thirst and hunger, weakness, tiredness and a reduced level of higher cerebral function are some of the characteristics of perioperative fasting. Preoperative feeding included in the appropriate protocols with the aim of optimising the condition of the patient before surgery could result in faster recovery from surgery, earlier discharge from hospital and an earlier start of the rehabilitation process which is the final stage of complete recovery for all surgical patients.
Nutritional support for elderly patients undergoing elective surgery is a very important issue because elderly patients usually have one or more comorbidity, less reserve of skeletal muscle, and a compromised immune response. Therefore, it is very important to maintain uninterrupted nutritional support for these patients. This could maintain or even improve their immune function, and therefore reduce the risk of infection.18
The findings of Harsten et al.1 have raised an interesting question as to whether carbohydrate solution is the ‘perfect’ preoperative liquid or whether water could be as good a choice for preoperative feeding, bearing in mind the cost benefit for hospitals. With regard to the type of clear fluid, Smith et al.9 did not find differences between water, pulp-free juice, tea or coffee without milk for preoperative feeding. Further studies should be performed in order to establish which clear liquid is preferable for preoperative feeding in respect of well-being of the patient and cost benefit for the hospital.
Is preoperative feeding something new? Unfortunately, it is not. In 1883, Lister19 made a recommendation that patients should drink liquid up to 2 h before surgery.
In conclusion, it seems that overnight fasting should be avoided as much as possible and preoperative fluid administration up to 2 h before induction of anaesthesia is recommended.
The authors are supported by a grant from the Croatian Ministry of Science, Education and Sports (project no. 0062078). The funding agencies had no role in the preparation, review or approval of the manuscript. The authors have no conflict of interest.
This article was checked and accepted by the editors, but was not sent for external peer review.
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