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    Cerebral Perfusion Pressure

    Calculates blood flow to the brain.
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    INSTRUCTIONS

    Use in patients with an intracranial pressure monitoring device.

    When to Use
    Pearls/Pitfalls
    Why Use

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

    • 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.
    • 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.
    mm Hg
    mm Hg

    Result:

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    Next Steps
    Evidence
    Creator Insights

    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.

    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:
    • 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.

    Formula

    CPP = MAP – ICP

    MAP, mean arterial pressure. ICP, intracranial pressure.

    Facts & Figures

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

    Evidence Appraisal

    The values of both CPP and ICP should be included in clinical decision-making. There is extensive data linking the use of both of these metrics to decreased mortality. The definition of normal ICP varies in the literature, but commonly-applied normal ranges are as follows:

    • Supine adults: 5–15 mmHg or 7–15 mmHg
    • Supine children: 3–7 mmHg
    • Supine infants: 1–5 mmHg or 1–6 mmHg

    Brain Trauma Foundation guidelines recommend treating an ICP >22 mmHg due to evidence showing increased mortality above this threshold.

    The definition of normal CPP also varies in the literature. However, the Brain Trauma Foundation guidelines define normal CPP at 60–70 mmHg.

    Although the details and definitions may vary, overall the data overwhelmingly support the use of ICP monitoring and CPP targets in patients with severe TBI (GCS ≤8). One large (n = 2,320) multicenter observational study by Gerber et al looked at a 9-year period in which increased adherence to the Brain Trauma Foundation management guidelines regarding use of ICP and CPP targets was correlated with significantly improved mortality, making the case for clinical application of these guidelines. Specifically, they found that as the rate of use of ICP monitoring increased (56% to 75%), and adherence to CPP target thresholds increased (15% to 48%), overall fatality decreased (22% to 13%).

    Increasing a patient’s CPP does come with potential risks. Multiple studies have shown an increased risk of hypoxemic respiratory failure and ARDS in those patients treated to a target CPP >70 mmHg. In a single-center RCT comparing ICP-directed management versus cerebral blood flow-directed (CBF-directed) management, the latter of which involved maintaining CPP >70 mmHg, Contant et al found a fivefold higher risk of ARDS in patients in the CBF-directed management group (15% versus 3.3%).

    In a retrospective cohort study by Cremer et al, the study investigators found that, among those TBI patients who survived 24 hours past the initial brain injury, CPP evaluation to guide clinical decision-making was associated with no difference in mortality, but doubled the number of ventilator-dependent days (5 vs. 12). However, the cohort of patients for whom CPP evaluation was used to guide care in this study were treated to a target CPP >70 mmHg, therefore it is not surprising that these patients required longer mechanical ventilation.

    Other studies have found no additional mortality benefit to maintaining CPP >70 mmHg. Thus, targeting a CPP >70 mmHg is not recommended, as it is associated with increased complications without increased benefit.

    Literature

    Other References

    Research PaperFarahvar A, Gerber LM, Chiu YL, Carney N, Hartl R, Ghajar J. Increased mortality in patients with severe traumatic brain injury treated without intracranial pressure monitoring. J Neurosurg. Oct 2012;117(4):729-734. Research PaperTalving P, Karamanos E, Teixeira PG, et al. Intracranial pressure monitoring in severe head injury: compliance with Brain Trauma Foundation guidelines and effect on outcomes: a prospective study. J Neurosurg. Nov 2013;119(5):1248-1254. Research PaperGerber LM, Chiu YL, Carney N, Hartl R, Ghajar J. Marked reduction in mortality in patients with severe traumatic brain injury. J Neurosurg. Dec 2013;119(6):1583-1590. Research PaperHuang SJ, Hong WC, Han YY, et al. Clinical outcome of severe head injury using three different ICP and CPP protocol-driven therapies. J Clin Neurosci. Oct 2006;13(8):818- 822. Research PaperContant CF, Valadka AB, Gopinath SP, Hannay HJ, Robertson CS. Adult respiratory distress syndrome: a complication of induced hypertension after severe head injury. J Neurosurg. Oct 2001;95(4):560-8.Research PaperCremer OL, van Dijk GW, van Wensen E, Brekelmans GJ, Moons KG, Leenen LP, Kalkman CJ. Effect of intracranial pressure monitoring and targeted intensive care on functional outcome after severe head injury. Crit Care Med. Oct 2005;33(10):2207-13.Research PaperJohnson U, Nilsson P, Ronne-Engstrom E, Howells T, Enblad P. Favorable outcome in traumatic brain injury patients with impaired cerebral pressure autoregulation when treated at low cerebral perfusion pressure levels. Neurosurg. 2011;68(3):714-721.Research PaperBalestreri M, Czosnyka M, Hutchinson P, Steiner LA, Hiler M, Smielewski P, Pickard JD. Impact of intracranial pressure and cerebral perfusion pressure on severe disability and mortality after head injury. Neurocrit Care. 2006;4(1):8-13.
    Dr. Luzius A. Steiner

    About the Creator

    Luzius A. Steiner, MD, PhD, is a professor and the head of anesthesiology at University Hospital Basel in Switzerland. He has authored or co-authored dozens of studies in neurocritical care on cerebral perfusion pressure. Dr. Steiner is a member of the European Society of Intensive Care Medicine and the European Society of Anesthesiology.

    To view Dr. Luzius A. Steiner's publications, visit PubMed

    Content Contributors
    • Lubabah Ben-Ghaly, MD
    Reviewed By
    • Jarone Lee, MD
    About the Creator
    Dr. Luzius A. Steiner
    Content Contributors
    • Lubabah Ben-Ghaly, MD
    Reviewed By
    • Jarone Lee, MD