From the Guidelines
In stroke patients, PaCO2 should be maintained in the low-normal range (35-40 mmHg) for the first 24 hours after the stroke event, as recommended by the most recent and highest quality study 1. This approach should be individualized based on the patient's clinical status and neurological monitoring.
- The physiological basis for this recommendation is that lower PaCO2 levels cause cerebral vasoconstriction, which can reduce cerebral blood volume and intracranial pressure.
- However, excessive or prolonged hypocapnia may worsen cerebral ischemia by reducing blood flow to vulnerable brain tissue.
- Regular arterial blood gas monitoring is essential during this period to ensure PaCO2 remains within target range, and ventilator settings should be adjusted accordingly if the patient is mechanically ventilated.
- As the risk of cerebral edema decreases after the initial period, PaCO2 should be allowed to normalize to 40-45 mmHg. The study by Westermaier et al. 1 found that PaCO2 levels above 37.5 mmHg in the first 24 h of care have been associated with a decreased risk of unfavorable outcome, suggesting that permissive mild hypercapnia may be beneficial in aSAH patients.
- However, it is crucial to note that the safety and efficacy of permissive hypercapnia as a therapy still require further investigation, particularly in patients without an external ventricular drain (EVD).
- The study also highlighted the importance of individualized management, as the response to changes in PaCO2 can vary significantly between patients. Overall, the current evidence suggests that maintaining PaCO2 in the low-normal range (35-40 mmHg) for the first 24 hours after the stroke event is a reasonable approach, but it should be tailored to the individual patient's needs and closely monitored to avoid potential complications.
From the Research
PaCO2 Management in Stroke Patients
- The ideal duration for allowing PaCO2 in the low-normal range in stroke patients is not explicitly stated in the provided studies 2, 3, 4, 5, 6.
- However, it is known that large decreases in PaCO2 can cause cerebral vasoconstriction and compromise brain tissue perfusion, potentially leading to neurological complications 3.
- A study found that patients with a large relative decrease in PaCO2 (>50%) had an increased incidence of neurological complications compared to those with a smaller decrease 3.
- Maintaining normotension, normothermia, adequate ventilation, and oxygenation is crucial in managing cerebral edema in stroke patients 4.
- The optimal mechanical ventilator strategy for stroke patients remains unclear, but a protective ventilatory strategy may have a role in brain-damaged patients, including those with stroke 5.
Considerations for Mechanical Ventilation
- Mechanical ventilation is frequently performed in stroke patients due to swallowing dysfunction and airway or respiratory system compromise 5.
- Pulmonary complications are common in stroke patients and can be a major cause of death 5.
- Tracheostomy use has increased among stroke patients, with unique indications depending on the location and type of stroke 5.
- Management of acute ischemic stroke in the first hours is critical to patient outcomes, and treatment options include thrombolysis and endovascular therapy 6.