What part of the brain does permissive hypertension protect when managing Cardiovascular Disease (CVD) infarct?

From the Guidelines

Permissive hypertension protects the penumbra region surrounding a cerebrovascular infarct, which is the potentially salvageable brain tissue surrounding the core infarct. When managing a cerebrovascular infarct, allowing blood pressure to remain elevated (permissive hypertension) helps maintain adequate perfusion to the ischemic penumbra. This area has compromised blood flow but hasn't yet undergone irreversible damage.

Key Considerations

• Current guidelines typically recommend avoiding aggressive blood pressure lowering in acute ischemic stroke unless the systolic blood pressure exceeds 220 mmHg or diastolic exceeds 120 mmHg, as stated in the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults 1.
• For patients receiving thrombolytic therapy with tPA, blood pressure should be maintained below 180/105 mmHg.
• The physiological basis for this approach is that autoregulation of cerebral blood flow is impaired in the penumbra, making this tissue dependent on systemic blood pressure for adequate perfusion, as discussed in the guidelines 1.
• Premature lowering of blood pressure can reduce cerebral perfusion pressure, potentially expanding the infarct size and worsening neurological outcomes.

Management Approach

• This approach is typically maintained for the first 24-72 hours after stroke onset, after which blood pressure management can gradually transition to more standard targets.
• It is essential to consider the individual patient's condition, including the presence of comorbidities and the specific characteristics of the stroke, when making decisions about blood pressure management, as highlighted in the guidelines 1.
• The goal is to balance the need to maintain adequate cerebral perfusion with the risk of exacerbating brain edema and hemorrhagic transformation, as discussed in the guidelines 1.

From the Research

Permissive Hypertension in Cardiovascular Disease

Permissive hypertension is a management approach used in the setting of acute ischemic stroke, where blood pressure is allowed to remain elevated to ensure adequate cerebral blood flow to the penumbral area surrounding the infarct. The following points highlight the key aspects of permissive hypertension:

• The optimal management of blood pressure in the first 24 hours of ischemic stroke remains a controversial topic 2.
• Permissive hypertension is recommended, where antihypertensive treatment is warranted in patients with systolic blood pressure greater than 220 mm Hg, receiving thrombolytic therapy, or with concomitant medical issues 2, 3.
• The use of predictable and titratable medications that judiciously reduce (approximately 10% to 15%) the initial presenting mean arterial pressure is recommended in these situations 2.
• The brain is an elective and early target of hypertensive crisis, and the strong relationship between arterial hypertension and cerebrovascular diseases is supported by extensive evidence 4.

Protection of Brain Areas

The specific part of the brain protected by permissive hypertension is not explicitly stated in the provided studies. However, it can be inferred that permissive hypertension aims to protect the penumbral area surrounding the infarct, which is the area of brain tissue that is at risk of further damage due to inadequate blood flow:

• The penumbral area is the region surrounding the infarct that is still viable but at risk of further damage due to inadequate blood flow 2, 3.
• Permissive hypertension may help to maintain cerebral blood flow to this area, reducing the risk of further damage and improving outcomes 2, 3.
• The optimal blood pressure goals for permissive hypertension are not clearly defined and may vary depending on individual patient factors, such as the presence of comorbid conditions or the use of thrombolytic therapy 2, 3, 5.