Cerebral Perfusion Pressure

Why Use

CPP decreases as ICP rises, leading to cerebral ischemia and further neurological injury. Calculating CPP helps clinicians identify patients who may be experiencing ongoing neurological injury from inadequate cerebral perfusion. Helps prevent further cerebral ischemia by treating elevated ICP and hypotension as appropriate.

When to Use

Use in supine patients with elevated intracranial pressure (e.g. from hemorrhage, edema, mass).

Formula

Pearls / Pitfalls

Requires invasive intracranial pressure (ICP) monitoring. Although there is still some debate in the literature, it is generally accepted that the normal range of CPP in a supine patient is 60–70 mmHg. Clinicians must address both the patient’s CPP and ICP. For example, a patient could have a normal calculated CPP, but if the ICP is significantly elevated, it must be treated. The definition of normal ICP changes with posture and age. It also varies slightly depending on which data are applied. Therefore, it is important to be aware of local practice guidelines when applying this calculator.

Management

Low CPP (<60 mmHg): Patient is at risk for further neurological injury from cerebral hypoperfusion. Consider interventions to increase MAP (e.g. vasopressors, fluid bolus) or decrease ICP (e.g. elevate head of bed, mannitol, CSF drainage). Normal CPP (60–70 mmHg) Patient likely has adequate cerebral perfusion. High CPP (>70 mmHg) Patient is unlikely to benefit from CPP this high and may be at increased risk for hypoxemic respiratory failure and ARDS, which can contribute to cerebral ischemia and prolonged mechanical ventilation. If the patient has blood pressure room, consider backing down on interventions raising the patient’s MAP (e.g. pressors).

Critical Actions

Even if the patient has a normal calculated CPP, clinicians must also: Treat elevated ICP (current Brain Trauma Foundation guidelines recommend intervention for ICP >22 mmHg). Correct hypotension. Regional differences in ICP may exist (e.g. local mass effect can mean increased ICP in one particular area of the brain), leading to gradients in CPP across different areas of the brain. Interpret these results with caution.

Advice

To achieve adequate CPP, clinicians must balance (1) treating the underlying cause of elevated ICP and (2) appropriately supporting the patient’s blood pressure.

More Information

Target CPP in TBI patients is 60–70 mmHg, per 2017 Brain Trauma Foundation evidence-based guidelines .