Best practice & research. Clinical anaesthesiology
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The gastric emptying rate is a carefully regulated process consisting of different mathematically defined phases. The gastric metabolic load, as well as neural regulatory mechanisms and hormonal influences, cooperate in order to achieve a well-balanced emptying of contents from the stomach into the duodenum for absorption in the small intestine. ⋯ We have found that the two peptide hormones ghrelin and glucagon-like peptide- I (GLP- I) have a great impact on the regulation of gastric emptying: ghrelin is a most potent stimulator of gastric contractions and emptying, and GLP- I profoundly inhibits this emptying process. These data suggest possibilities for governing the rate of gastric emptying as a natural step in achieving metabolic balance and control.
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Best Pract Res Clin Anaesthesiol · Sep 2006
ReviewThe evidence base behind modern fasting guidelines.
Fasting before general anaesthesia aims to reduce the volume and acidity of stomach contents, thus decreasing the risk of regurgitation/aspiration. The objectives of the Cochrane report which are summarised in this paper, were to systematically review the effect of different preoperative fasting regimes (duration, type and volume of intake) on perioperative complications and patient wellbeing. Few trials reported the incidence of aspiration/regurgitation or related morbidity but relied on indirect measures of patient safety ie. intraoperative gastric volume and pH. ⋯ Intake of fluids up to 90 min preoperatively had no impact on gastric contents but this was based on small numbers. In addition, permitting patients to drink water preoperatively resulted in significantly lower gastric volumes. Clinicians should evaluate this evidence for themselves and when necessary, adjust existing fasting policies.
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Best Pract Res Clin Anaesthesiol · Sep 2006
ReviewModern preoperative fasting guidelines: a summary of the present recommendations and remaining questions.
This chapter is complementary to the others in this volume focusing on preoperative fasting routines. In it we discuss some of the issues in need of more research to define best practice. One of these is the role of fasting in emergency patients. ⋯ Last but not least, new scientific evidence alone is not enough to change daily practice. Active implementation of new evidence is also needed. To improve perioperative care, anaesthesiologists, surgeons and the nursing staff must work together.
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Best Pract Res Clin Anaesthesiol · Sep 2006
Review Historical ArticleFasting from midnight--the history behind the dogma.
The purpose of this chapter is to review historical fasting guidelines and how the dogma of fasting from midnight arose and came to be challenged by randomized clinical trials of preoperative clear liquids versus overnight fast. Medical and anaesthesia textbooks and journals from the 19th and 20th centuries were consulted, and the results of clinical trials and the reaction to them are reviewed. The dogma appeared to result from extrapolation of pulmonary aspiration risk in 'full-stomach' emergency cases to healthy elective cases. ⋯ Subsequent large-scale studies showed the risk to be minimal. Meta-analysis of randomized clinical trials demonstrated the safety of clear oral liquids until 2 hr preoperatively in healthy patients undergoing elective surgery. Reaction was cautious but led to eventual acceptance of evidence-based fasting guidelines.
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Pulmonary aspiration of gastric contents in the perioperative phase is associated with increased postoperative morbidity and mortality. For the management of aspiration, differentiation between acid-associated aspiration pneumonitis and aspiration pneumonia as a consequence of a secondary bacterial contamination is of crucial importance. The incidence of aspiration in elective surgery is 1 per 2000-3000 anaesthesias in adults. ⋯ Cricoid pressure, as a non-evidence-based but clinically wide-spread method in the context of the prophylaxis of aspiration, is discussed critically. The main part deals with strategies to structure the management of aspiration by use of scientific concepts based on medical crisis management. For this, an algorithm based on current scientific investigations is presented.