Anaesthesia for emergency surgery and mendelson syndrome

• In elective surgery


  • Making correct diagnosis
  • Identifying and treating medical disorders
  • Observing fasting guidelines
• One or more of these conditions are often not met in emergency surgery
• Further problems in emergency surgery

  • Dehydration
  • Electrolyte abnormalities
  • Hemorrhage
  • Pain
• The components of general anesthesia are the same in elective and emergency surgery
• Components of general anaesthesia

  • Preoperative assessment
  • Premedication
  • Induction
  • Maintenance
  • Reversal
  • Postoperative care
• The key to success in emergency anaesthesia

  • A thorough preoperative assessment
  • Particular attention must be given to the search for medical problem
  • The occurrence of hypovolemia
  • Airway assessment
• There are very few patients whose clinical state is so life – threatening that they need immediate surgery (true emergency)
• CLASSIFICATION OF OPERATIONS


  • Immediate operation within one hour of surgical consultation and considered life – saving, for example, ruptured aortic aneurysm repair (Emergency)
  • Operation as soon as possible after resuscitation, usually within 24 hour of surgical consultation, for example, intestinal obstruction (Urgent)
  • Early operation between 1 and 3 weeks, which is not immediately life – saving, for example, cancer surgery, cardiac surgery (Scheduled)
  • Operation at the time to suit both the patient and surgeon (Elective)
• The vast majority of patients benefit from

  • The correction of hypovolemia
  • The correction of electrolyte abnormality
  • Stabilization of medical problem
  • Waiting for the stomach to empty
• When to operate is the most important decision that has to be made in emergency situation
• CLASSIFICATION OF ANESTHETIC TECHNIQUES

  • General anesthesia: Intubation of unprotected airway, Spontaneous respiration or controlled ventilation, Use of muscle relaxants
  • Regional anesthesia
  • Combination of general and regional anesthesia
  • Sedation: Intravenous, Inhalational
  • Combination of sedation and regional anesthesia
• All emergency patients should be treated as having a full stomach and so at risk of vomiting, regurgitation, and aspiration
• Vomiting occurs at the induction and emergence from anaesthesia
• Aspiration of gastric acid into the lungs, creating a pneumonitis can be fatal
• MANAGEMENT OF ENDOTRACHEAL INTUBATION WHEN RISK OF ASPIRATION

  • Empty stomach: From above by nasogastric tube, From below by drugs, for example, metoclopramide
  • Neutralise remaining stomach contents: Antacids, Use of H₂ blocking drugs to prevent further secretion
  • Stop central nervous system induced vomiting: Avoid opiates
  • Correct anaesthetic technique: Rapid sequence induction, Pre-oxygenation, Cricoid pressure, Intubation
• Neither physical nor pharmacological methods should be relied on to empty the stomach completely
• In some specialties (obstetrics), an H₂ receptor blocking drug and 30 ml sodium citrate used orally 15 minutes before induction of anesthesia
• Opiates delay gastric emptying and increase the likelihood of vomiting
• The only reliable way to prevent regurgitation is by using the correct anesthetic technique (rapid sequence induction)
• Preoxygenation


  Breathing 100% oxygen for at least 3 minutes before induction
• Cricoid pressure


  Identifying the cricoid cartilage on the patient before induction of anesthesia, Pressing down on the cartilage continuously until the anesthetist tells the assistant to stop, Compressing the esophagus between the cricoid cartilage and vertebral column
• Short-acting neuromuscular blocking drug (suxa) is administered to facilitate intubation
• The lungs are not ventilated during a rapid sequence induction; this will prevent accidental inflation of the stomach, which will further predispose the patient to regurgitation and vomiting
• An agent with a short duration of action is valuable because in cases of failed intubation spontaneous respiration will return promptly
• The anaesthetic is maintained with


  • A volatile agent
  • Nitrous oxide
  • Oxygen
  • Competitive relaxant
  • Suitable analgesia
• The reversal of the relaxant at the end of the procedure is undertaken with the anticholinesterase (neostigmine)
• Atropine or glycopyrrolate is given concomitantly to stop bradycardia occurring from the neostigmine
• Major disadvantage of potential hemodynamic instability of rapid sequence induction: hypertension and tachycardia following laryngoscopy and intubation
• This is more severe in emergency situation than in elective surgery because short acting opioids are administered prior to intubation to obtund pressor response to laryngoscopy and intubation during elective surgery
• HIGH RISK FACTORS FOR REGURGITATION

  • Oesophageal disease: Pouch, Stricture
  • Gastro-oesophageal sphincter abnormalities: Hiatus hernia, Obesity, Drugs
  • Gastric emptying delay: Trauma, Pyloric stenosis, Gastric malignancy, Opiates, Patient predisposition, anxiety, Pregnancy, Recent food intake
  • Abnormal bowel peristalsis: Peritonitis, Ileus – metabolic or drugs, Bowel obstruction
• Aspiration pneumonitis - Mendelson's syndrome


  Vomiting or regurgitation of gastric contents, fluid and / or particulate matter into the trachea may cause hypoxia by both mechanical obstruction and an acute pulmonary inflammatory response (chemical pneumonitis). This may progress to atelectasis and infection.
• Vomiting


  An active process, with expulsion of stomach contents into the pharynx by contraction of the diaphragm
• Regurgitation


  A passive process, occurs at any time, often "silent" and usually at deeper planes of anaesthesia
• PATIENTS AT RISK OF ASPIRATION

  • Full stomach
  • Gastric outlet obstruction
  • History of gastric reflux
  • Abnormal oesophageal anatomy or function
  • Emergency procedures
  • Trauma
  • Difficult airway management
  • Pregnancy and labour
  • Paediatrics due to immature gastro-oesophageal sphincter
  • Morbid obesity (BMI > 35 kg m-2)
  • ASA III or IV
  • Decreased level of consciousness (LOC)
  • Pain
  • Muscle weakness
• PREVENTION OF ASPIRATION PNEUMONITIS

  • Empty the stomach: Delay surgery till nil per os (NPO) status acceptable, depending on urgency of surgery, Nasogastric tube to drain stomach, but this is no guarantee that the stomach is empty, Prokinetic drugs – Metoclopramide 10 mg IV 30 min pre-operatively
  • Neutralise stomach acid: Non-particulate antacid – Sodium citrate 30 ml within 30 min of induction, H2-receptor blockers – Ranitidine, Proton pump inhibitors – Omeprazole
  • Correct anaesthetic technique: Rapid sequence induction, Awake intubation
• SIGNS OF ASPIRATION


  • None (silent) especially with depressed level of consciousness on O2 supplementation
  • Decreased O2 saturation
  • Coughing
  • Tachypnoea
  • Tachycardia
  • Hypotension
  • Decreased lung compliance
  • Wheezes and crackles
  • Postoperative pulmonary disease
  • Chest X-ray may show diffuse infiltrates (usually right lower or upper lobe)
• MANAGEMENT OF ASPIRATION


  • Oxygen as required – Maintain Hb saturation > 95%
  • Minimise risk of further aspiration: (1)Left lateral position (left side down – this allows intubation in that position if required) (2) Head down (encourages passive flow of contents of the pharynx out of the mouth) (3) Oropharyngeal suction before ventilation
  • Endotracheal intubation (ETT) if ventilation or suctioning of trachea required
  • Treat as foreign body – Minimise positive pressure ventilation, consider bronchoscopy
  • Nasogastric tube to help empty stomach
  • Monitor respiratory function
  • Chest X-ray looking for oedema, collapse and / or consolidation
  • Consider intensive care unit (ICU) admission
  • Routine antibiotics or steroids are indicated
• Anaesthesia for emergency surgery needs careful preoperative assessment and adequate patient's resuscitation before surgery. This will ultimately lead to a successful outcome.