Anaesthesia for Emergency Surgery-Challenges and Preparation. Mendelson’s Syndrome

Higher Risk of Perioperative Complications and Adverse Events

There is a higher risk of perioperative complications and adverse events.

The objective is to permit the correction of surgical pathology with the minimum risk possible.

Risks may be reduced by considering:

• History
• Clinical examination
• Basic and special investigations

It is essential to ascertain the likely surgical diagnosis and the magnitude of proposed surgery and its urgency.

Plan preoperative preparation, workup, resuscitation, method of anesthesia, and postoperative requirements.

Anticipate and prepare for complications, such as:

• Hypovolemia
• Hypotension
• Vomiting
• Dysrhythmias
• Adverse drug reactions in the presence of electrolyte abnormalities or renal dysfunction, etc.

The National Confidential Enquiry into Patient Outcome and Death (NCEPOD)

IMMEDIATE

Immediate life, limb, or organ-saving intervention (within minutes of the decision to operate, e.g., GI bleeding, traumatic spleen).

URGENT

Intervention for acute onset or clinical deterioration of potentially life-threatening conditions that may threaten the survival of limb or organ (within hours of the decision to operate, e.g., Perforated large bowel).

EXPEDITED

Requiring early treatment where the condition is not life-threatening (within days of the decision to operate, e.g., developing large bowel obstruction).

ELECTIVE

Intervention planned in advance of routine, timing to suit the patient, hospital, and staff (e.g., Resection of non-obstructing carcinoma).

• Limited Time for Assessment and Preparation: Limited time to assess and prepare the patient for surgery and anesthesia.
• Uncertain Diagnoses: Uncertain diagnoses, e.g., laparotomy for acute abdomen.
• Aspiration Risk: Risk of aspiration due to a full stomach.
• Body Fluid Compartment Derangements: Clinical acumen and a high index of suspicion are needed to assess intravascular volume and extravascular fluid status.
• Electrolyte and Acid-Base Derangements.
• Haematological and Coagulation Abnormalities: e.g., sepsis, liver disease, heart failure, renal failure.
• Coexisting Diseases and Poorly Controlled Chronic Medical Problems: Commonly diabetes, arrhythmias, hypertension, ischemic heart disease, cardiac failure, chronic obstructive pulmonary disease.
• Pain and Its Pathophysiological Effects.
• After-Hours Surgery with Junior Staff: Ask for help early during the assessment and planning phase to anticipate problems.

1. History, Aspiration Risks, and Review of Notes
2. Examination and Airway Assessment
3. Basic Investigations
• Hb, Na+, K+, creatinine, urea, glucose, lactate, blood gas analysis
• Chest X-ray / ECG for CVS / Respiratory disease
4. Special Investigations

Special investigations are only indicated if the management of immediate problems is affected.

• Clear Fluids: Clear fluids are cleared from the stomach within 2 hours of ingestion. Gastric emptying of solids is slower.
• ASA Fasting Guidelines 1999:
• Clear Fluids - 2 hours
• Breast Milk - 4 hours
• Non-human Milk - 6 hours
• Light Meal - 6 hours

There are very few patients whose clinical state is so life-threatening that they need immediate surgery, i.e., a true emergency. The majority of patients benefit greatly from:

• Correcting hypovolemia and electrolyte abnormalities
• Stabilizing medical problems
• Waiting for stomach emptying.

General anesthesia is the most common type of anesthetic for emergency surgery, but regional or sedation techniques may also be used.

Must consider the patient's clinical condition and the pharmacokinetic/dynamic implications, e.g., hypovolemia, hypokalemia, uremia, sepsis, etc.

• Preparation
• Induction and Airway Control
• Maintenance
• Reversal and Emergence
• Recovery and Postoperative Care

• Balance of risk of losing control of the airway against the risk of aspiration.
• Must prepare a contingency plan for the management of the patient should intubation fail.
• Main disadvantage of RSI is CVS instability if excessive (hypotension) or insufficient (hypertension, tachycardia, dysrhythmia) induction agent is given.

Preparation for RSI

• Routine machine and equipment check.
• 2 laryngoscopes and various blades, range of ETT sizes, introducers/bougies/stylets.
• Skilled assistant for cricoid pressure - on INDUCTION of anesthesia.
• Tilting bed/table/trolley.
• Patient supine in sniffing position.
• Suction at arm's length and on.
• Patient monitoring attached with baseline readings.
• Plan for failed intubation, e.g., wake up the patient?

Rapid Sequence Induction

• Preoxygenation: Preoxygenate with 100% oxygen for 3 - 5 minutes using a tight-fitting mask on the anesthetic breathing circuit. Maintain an O2 flow rate of > 4 L/min to prevent rebreathing and efficiently wash out N2.
• IV Drip: Ensure the intravenous (IV) drip is functioning.
• IV Induction: Administer the IV induction agent at a predetermined dose, followed by succinylcholine at 1 - 2 mg/kg. An assistant applies cricoid pressure as the patient loses consciousness.
• Direct Laryngoscopy and ETT Insertion: Perform direct laryngoscopy and insert the endotracheal tube (ETT) after observing fasciculations, approximately 45-60 seconds after giving succinylcholine. If fasciculations are absent, attempt intubation at 60 seconds.
• Inflate ETT Cuff.
• IPPV and ETT Position Confirmation: Administer intermittent positive pressure ventilation (IPPV) and perform tests to confirm the ETT position.
• Assistant Releases Cricoid Pressure: The assistant releases cricoid pressure only after the confirmation of the ETT in the correct position.
• ETT Strapping/Tying: Secure the ETT by strapping or tying it in position.

Extubation after RSI

• Risk of aspiration is as great during emergence as on induction.
• Extubation should only be performed once protective airway reflexes have returned.
• Ideally, the patient should be awake in a left lateral position.
• Before extubation, the patient must be:
1. Reversed Adequately.
2. Breathing Spontaneously on 40% O2 with Saturation Readings > 94%.
3. Suctioned Oro/Nasopharynx.
4. Awake and Responding to Verbal Commands (e.g., open eyes, nod, or lift the head).
5. ETT Cuff Deflated and Removed During Manual Positive Pressure Breath.

Patients to consider for postoperative ventilation or ICU are those with:

• Prolonged Shock of Any Cause
• Massive Sepsis
• Ischaemic Heart Disease
• Extreme Obesity
• Overt Gastric Acid Aspiration
• Pulmonary Disease
• Requiring Inotropes
• Hypothermia (Temp < 34°C)
• Intra-abdominal Packs
• Respiratory Failure
• Renal Failure

Vomiting or regurgitation of gastric contents, including fluid and particulate matter, into the trachea may cause hypoxia due to airway obstruction and an acute pulmonary inflammatory response, known as chemical pneumonitis. This condition may progress to atelectasis and infection. The outcome of pulmonary aspiration depends on the type, pH, and volume of the aspirated fluid.

• Aspiration Occurs When Airway Reflexes Are Depressed: Aspiration occurs during general anesthesia, sedation, or when the patient's level of consciousness is decreased.
• Vomiting as an Active Process: Vomiting is an active process that may occur at lighter planes of anesthesia, such as during induction and emergence. Vomitus may stimulate spasm of the vocal cords, leading to apnea and hypoxia.
• Regurgitation as a Passive Process: Regurgitation is a passive process that may occur at any time, is often "silent," and usually occurs at deeper planes of anesthesia when laryngeal reflexes are reduced or paralyzed.

Patients at Risk of Aspiration

• Full Stomach
• History of Gastric Reflux
• Abnormal Esophageal Anatomy or Function
• Emergency Procedures
• Trauma
• Difficult Airway Management
• Pregnancy and Labor
• Pediatrics
• Obesity (BMI > 30 kg/m²)
• ASA III – IV
• Decreased Level of Consciousness
• Pain
• Muscle Weakness

Full Stomach for Anesthetic Purposes

For anesthetic purposes, a full stomach is assumed when:

1. Recent Fluid/Solid Intake: Recent fluid or solid intake is within 6 hours (GSH rule).
2. Absent or Abnormal Peristalsis: Absent or abnormal peristalsis, which can occur in various conditions including:
• Peritonitis from any cause
• Ileus (postoperative, metabolic - e.g., hypokalemia, uremia, diabetic ketoacidosis, drug-induced - e.g., anticholinergics, opioids)
3. Obstructed Peristalsis: Obstructed peristalsis in conditions such as bowel obstruction, gastric carcinoma, and pyloric stenosis.
4. Delayed Gastric Emptying: Delayed gastric emptying occurs in various conditions, including:
• Shock of any cause
• Diabetes
• Trauma
• Pregnancy and labor
• Fear, pain, anxiety
• Opioids

Diagnosis - Signs of Aspiration

• None (Silent): Aspiration can be silent, especially in patients with a depressed level of consciousness who are on O2 supplementation.
• Decreased Oxygen Saturation
• Coughing
• Tachypnea
• Tachycardia
• Hypotension
• Decreased Lung Compliance
• Wheezes and Crackles
• Postoperative Pulmonary Disease
• Chest X-ray (CXR): CXR may show diffuse infiltrates, especially in the right lower lobe (RLL).

Management of Aspiration

• Prevention is Most Important: Identifying those at risk is crucial for prevention.
• Administer 80% O2: Provide high-flow oxygen (80%) to support oxygenation.
• Minimize Risk of Further Aspiration:
• Place the patient in a left lateral position (left side down).
• Position the head down.
• Perform oropharyngeal suctioning before ventilation.
• Consider Endotracheal Tube (ETT) if Ventilation or Tracheal Suctioning is Required.
• Treat as a Foreign Body: Minimize positive pressure ventilation and consider bronchoscopy if necessary.
• Further Management:
• Consider placing an N/G tube to help empty the stomach.
• Monitor respiratory function.
• Perform a chest X-ray (CXR) to look for signs of edema, collapse, or consolidation in the lungs.
• Consider ICU Admission.
• No Routine Antibiotics or Steroids.