Anaes · Neuroanaesthesia
ICP, cerebral autoregulation and CPP
Also known as Cerebral perfusion pressure · Autoregulation · Monro-Kellie · Raised ICP · Lassen curve
Core neurophysiology for fellowship exams: Monro-Kellie doctrine, Lassen autoregulation, exact CPP equals MAP minus ICP, BTF targets, anaesthetic agent effects, and ICP crisis management.
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Red flags
- CPP = MAP − ICP is the core equation — say it exactly.
- BTF: treat ICP greater than 22 mmHg; CPP target 60–70 mmHg in severe TBI.
- Avoid prophylactic hyperventilation; use briefly only for herniation bridge.
- Mannitol 0.25–1 g/kg IV or hypertonic saline for osmotherapy.
- Support MAP when lowering ICP — both determine CPP.
Meet the patient
A young man with a severe head injury is in theatre for evacuation. The ICP monitor reads 30 mmHg and the MAP is 70. The surgeon asks you to calculate the CPP and lower the pressure. The fellowship answer opens with the equation, then defends both limbs of it.[1]
CPP is 40 mmHg — dangerously low — and the lesson of the stem is that you cannot lower the MAP to "rest the brain" without knowing the ICP, because in a pressure-passive injured brain you may crush the CPP. Every neuro case is built on intracranial elastance, autoregulation, and agent effects, and the equation is the gate they all pass through.[1]
References5ShowHide
- [1]Carney N et al. Guidelines for the Management of Severe Traumatic Brain Injury, Fourth Edition Neurosurgery, 2017.PMID 27654000
- [2]Chesnut RM et al. A trial of intracranial-pressure monitoring in traumatic brain injury N Engl J Med, 2012.PMID 23234472
- [3]Banik S et al. Effect of dexmedetomidine on dynamic cerebral autoregulation and carbon dioxide reactivity during sevoflurane anesthesia in healthy patients Korean J Anesthesiol, 2020.PMID 32209963
- [4]Cook AM et al. Guidelines for the Acute Treatment of Cerebral Edema in Neurocritical Care Patients. Neurocrit Care, 2020.PMID 32227294
- [5]Zhou Z et al. Efficacy and safety of sevoflurane vs propofol in combination with remifentanil for anesthesia maintenance during craniotomy: A meta-analysis. Medicine (Baltimore), 2021.PMID 34941178