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preoperative fasting & aspiration prevention

Definition:
  • Preoperative fasting: prescribed period of time before a procedure when patients are not allowed the oral intake of liquids or solids (2).
  • Perioperative pulmonary aspiration: aspiration of gastric contents occurring after induction of anesthesia, during a procedure, or in the immediate period after surgery (2,3).
Epidemiology:
  • Risk factors:
    • Emergency surgery (particularly, trauma and abdominal surgery with delayed gastric emptying) procedures performed at night (3,4).
    • Inadequate anesthesia, to light during repetitive laryngoscopy because of difficult intubation (3,4).
    • Age >60 (3,4).
  • Mortality: 3.5-4.5% after aspiration, in obstetric anesthesia up to 12% (3).
Treatement:
  • Kinder <1 Jahr: Muttermilch bis 4 h präoperativ, klare Flüssigkeit (Tee, schwarzer Kaffee, Wasser ohne Kohlensäure, Sirup, klarer Apfelsaft, Enlive(R)) bis 2 h präoperativ, festes Nahrung bis 6 h präoperativ (1,2).
  • Kinder >1 Jahr, Jugendliche und Erwachsene: klare Flüssigkeit (Tee, schwarzer Kaffee, Wasser ohne Kohlensäure, Sirup, klarer Apfelsaft, Enlive(R)) bis 2 h präoperativ, festes Nahrung bis 6 h präoperativ (1,2).
  • The Task Force notes that intake of fried or fatty foods or meat my prolong gastric emptying time. Additional fasting time (E.g., 8h or more) may be needed in these cases (2).
  • The routine preoperative use of a single or multiple agents to reduce gastric volume or acidity in patients, planned for elective procedures, who have no apparent increased risk of pulmonary aspiration is not recommended (2).
The volume of liquid ingested ist less important than the type of liquid ingested (2).
Zu beachten sind Umständie wie Schmerzen, Stress, abdominelle Erkrankung mit erhöhter Magensaftmenge und Peritonealreizung, die verlangsamte Magenentleerung bei Frühgeborenen. Bei der Abschätzung des Aspirationsrisikos bei Notfällen ist die Zeitspanne zwischen Nahrungsaufnahme und Trauma bedeuted. Da ein Trauma die Magenentleerung verzögert, ist ein Abwarten von Nüchternzeiten nach Unfällen wenig sinnvoll (1).

Complications: the most severe lung injury is observed in patients following aspiration with food particulate material. Clinical outcome is not improved by a routine use of antibiotics in the acute phase of aspiration. However, if bowel contents are aspirated following an obstructive or paralytic ileus, antibiotics should be given. Targeted antibiotic therapy may be initated after culture of bronchoalveolar lavage fluid (3).

Future risks:
  • Aspiration pneumonia is most often seen in elderly patients and is an unwitnessed event. Colonised oropharyngeal material, including Gram-negative, Gram-positive and anaerobic bacteria leads to an acute inflammatory process (3).
  • In aspiration pneumonitis, which is most often a witnessed event, acidic and particulate gastric material induces an acute lung injury (3).
References:
  1. B. Hartmann. Präoperative Nahrungskarenz. KSA. 2009. BN004/1.
  2. Practice Guidelines for Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration: Application to Healthy Patients Undergoing Elective Procedures. An Updated Report bythe American Society of Anesthesiologists Committee on Standards and Practice Parameters. Anesthesiology. 2011;114(3):495-511: full text | pdf.
  3. Beatrice Beck-Schimmer et al. Bronchoaspiration: incidence, consequences and management. European Journal of Anesthesiology. 2011;28:78-84: full text.
  4. Kluger MT et al. Aspiration during anaesthesia: a review of 133 cases from the Australian Anaesthetic Incident Monitoring Study (AIMS). Anaesthesia. 1999;54:19-26: full text | pdf.