Induction of anaesthesia - the transition from consciousness to the anaesthetised state - is the phase of highest risk in a patient with raised intracranial pressure. In a patient with hydrocephalus awaiting VP shunt surgery, intracranial pressure is already elevated and the brain's compensatory mechanisms may be close to their limit. Any sudden further rise in pressure during induction can cause acute neurological deterioration. The specific risk comes from laryngoscopy and intubation — passing the laryngoscope and placing a breathing tube. This procedure triggers a reflex rise in blood pressure and heart rate that translates directly into a spike in intracranial pressure. In a healthy patient, this transient response is of no consequence. In a patient with hydrocephalus, it can be dangerous.
Drug selection: Intravenous induction agents are chosen for their ability to reduce cerebral metabolic rate and intracranial pressure rather than raise it. Propofol-based total intravenous anaesthesia is often preferred over inhalational agents in patients with significantly elevated pressure Timing and speed: Induction is managed to minimise the time the patient is in the most vulnerable transitional state before the airway is secured Blunting the laryngoscopy response: Opioids and in some cases lignocaine or antihypertensive agents are used to blunt the haemodynamic response to intubation.
Ventilation from the outset: Controlled ventilation targeting appropriate carbon dioxide levels begins as soon as the airway is secured, avoiding both hypercarbia (which dilates cerebral vessels and raises pressure) and excessive hyperventilation (which can cause cerebral ischaemia) As a Neuroanaesthesiologist at Sparsh Hospital, Hennur, Bengaluru, with 19 years of experience, I plan the induction of anaesthesia for every VP shunt patient individually, taking into account the urgency of the procedure, the degree of intracranial hypertension, the patient's age and weight, and any co-existing medical conditions.
Written by Dr Deepa Chandran, MBBS (M S Ramaiah Medical College, Bengaluru), DA (Bangalore Medical College), DNB Anaesthesia (Bangalore Baptist Hospital), Fellowship in Ultrasound Guided Regional Anaesthesia (Jubilee Mission Hospital), Fellowship in Pain and Palliative Care, Consultant Neuroanaesthesiologist and Critical Care Specialist, Sparsh Hospital, HBR Layout, Hennur Road, Bengaluru 560043. Phone: 9686911560.
