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Anaesthetic Emergencies

Laryngospasm

Complete/partial reflex adduction of the vocal cords occurs due to the involuntary contraction of the intrinsic muscle of the larynx. This can cause a variable degree of upper airway obstruction.


The risk factors for this are:

  • Anaesthetic-related factors - Insufficient depth of anaesthesia, Mucous/blood in the peri-glottic area, Airway manipulation (laryngoscopy, suction)

  • Patient-related factors - Young, Airway hyperactivity (asthma, smokers), Recent URTI, GORD

  • Surgical-related factors - Upper airway surgery (tonsillectomy), Thyroid surgery (superior laryngeal nerve injury)


It presents with:

  • Stridor

  • Abnormal see-saw movements of the abdomen and chest wall


Management:

  • Call for senior anaesthetic help Removal of stimulus e.g. suctioning blood clots, remove supraglottic airway device

  • 100% HF O2

  • Application of positive end-expiratory pressure (PEEP) - helps keep airways and alveoli open

  • Deepen anaesthesia w/propofol

    • If none of the above work, the patient will require suxamethonium to relax the vocal cords, and intubation.


Complications:

  • Hypoxia

  • Negative pressure pulmonary oedema

  • Bradycardia (in children)


Malignant Hyperthermia

This is an autosomal dominant disorder of the skeletal muscles, resulting in the uncontrolled release of calcium from skeletal muscle sarcoplasmic reticulum, leading to prolonged muscle contraction. This prolonged muscle contraction depletes ATP and dramatically increases O2 consumption, CO2 production, and heat → Hyperthermia. This can be triggered in the presence of suxamethonium and other volatile anaesthetic agents. The depletion of ATP leads to failure of the cell membrane's integrity, therefore causing its contents to leak out, such as potassium, creatinine kinase, and myoglobin. This can have very damaging effects on the kidneys.

It presents with:

  • Generalised, prolonged muscle rigidity

  • Rapid increase in body temperature

  • Rhabdomyolysis



Management:

  • Call for senior anaesthetic help

  • Remove stimulus e.g. disconnecting anaesthetic machine

  • 100% HF O2

  • IV Dantrolene - ryanodine receptor blocker to prevent calcium influx

  • Cooling of body temperature

  • Monitor urine output


Complications:

  • Acute renal failure

  • Hyperkalaemia

  • Arrhythmias


N.B. The muscle rigidity and rapid hyperthermia lead to the breakdown of skeletal muscle and subsequent myoglobinuria! This is directly toxic to the kidney, causing acute tubular necrosis.


Suxamethonium Apnoea (SA)

Suxamethonium is usually broken down within a few minutes. In SA, the enzymes for this are defective, leading to muscles staying paralysed for a prolonged period of time. This condition tends to run in families.


It presents with an inability to breath spontaneously when the drug is stopped.


It's managed with the use of a ventilator until the drug wears off.


N.B. Nowadays, anaesthetists avoid using suxamethonium, and only consider it if necessary.


Local Anaesthetic (LA) Toxicity

This is a life-threatening event in which the administration of LA leads to cardiorespiratory and central nervous system instability. It can occur with:

  • Accidental IV injection of LA (instead of IM)

  • Liver/renal disease can reduce LA clearance, leading to its accumulation

  • Injection of LA into a highly vascularised area, which increases the risk of rapid absorption into the systemic circulation


It presents with:

  • Sudden onset of altered mental status, tonic-clonic seizures, agitation or coma

  • Cardiac arrest

  • Tachy/bradyarrhythmias

  • Peri-oral tingling and numbness


Management:

  • Call for senior anaesthetic help

  • Remove stimulus e.g. stop injection

  • 100% HF O2

  • Lipid emulsion therapy e.g. Intralipid 20%



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