Correcting Hypocapnia in Aneurysmal Subarachnoid Hemorrhage.

The Chinese University of Hong Kong, Shenzhen

Status: Not yet enrolling

Conditions: Aneurysmal Subarachnoid Hemorrhage (aSAH)

Treatments: Behavioral: Normobaric Facemask Oxygen; Behavioral: control group

Study type: Observational

Funder types: Other

Identifiers

NCT07343232

CUHKShenzhen

Details and patient eligibility

About

Based on the clinical observation that over half of the patients in the management of aneurysmal subarachnoid hemorrhage(aSAH) present with spontaneous hyperventilation, which is significantly associated with delayed cerebral ischemia and poor neurological outcomes, this prospective pilot study is designed to investigate the safety and efficacy of normobaric facemask oxygen for hypocapnia in aSAH.

Full description

Spontaneous hyperventilation (SH) is highly prevalent following aneurysmal subarachnoid hemorrhage (aSAH) and is significantly associated with poor neurological outcomes.The core pathophysiological mechanism involves hypocapnia induced by hyperventilation, which triggers cerebral vasoconstriction and consequently leads to a decrease in cerebral blood flow (CBF).Although this response may transiently reduce intracranial pressure, persistent cerebral vasoconstriction markedly increases the risk of delayed cerebral ischemia (DCI) and secondary brain injury. Therefore, maintaining the arterial partial pressure of carbon dioxide (PaCO2) within the physiological range of mmHg is recommended to minimize the detrimental effects of hypocapnia.

Currently, there is a lack of standardized management strategies for hypocapnia resulting from SH after aSAH. Based on physiological principles, low-flow (<5 L/min) oxygen delivery via a facemask may effectively correct hypocapnia by promoting the rebreathing of carbon dioxide within the dead space of the facemask.10 A randomized controlled trial investigating psychogenic hyperventilation syndrome provides preliminary evidence for this approach, demonstrating that low-flow (3 L/min) facemask oxygen therapy can relieve symptoms more rapidly and improve patient comfort compared to traditional breathing training.11

However, high-level evidence regarding the safety, efficacy, and impact on neurological outcomes of using low-flow facemask oxygen therapy (functioning as a rebreathing mask) as a targeted intervention for correcting hypocapnia in aSAH patients remains scarce. Consequently, this proof-of-concept prospective study aims to systematically evaluate the operational safety and clinical effectiveness of rebreathing facemask oxygen therapy for correcting hypocapnia in patients with aSAH.

Enrollment: 80 estimated patients

Sex: All

Ages: 18+ years old

Volunteers: No Healthy Volunteers

Inclusion criteria

1. Age > 18 years.
2. Confirmed diagnosis of aneurysmal subarachnoid hemorrhage (aSAH), with the presence of an aneurysm verified by computed tomography (CT), CT angiography (CTA), or digital subtraction angiography (DSA).
3. Hunt-Hess grade II-IV.
4. Presence of hypocapnia on arterial blood gas analysis, defined as PaCO2 < 35 mmH;
5. PaO2 > 90 mmHg.

Exclusion criteria

1. Presence of brain herniation or refractory intracranial hypertension, defined as a baseline intracranial pressure (ICP) > 25 mmHg that responds poorly to conventional ICP-lowering therapy;
2. Primary respiratory diseases (e.g., chronic obstructive pulmonary disease, severe asthma) known to cause chronically elevated baseline PaCO2;
3. Severe acid-base disturbances other than respiratory alkalosis.
4. Severe cardiac insufficiency, severe hepatic or renal dysfunction, malignant tumors, or other severe comorbidities that significantly impact prognosis;
5. Before the onset of the disease, the mRS score was greater than 2, and there were other factors causing disability.
6. Life expectancy < 3 months;
7. Any other condition deemed by the investigator to pose a high risk warranting exclusion.

Trial design

80 participants in 2 patient groups

Normobaric Facemask Oxygen

Description:

Patients who received oxygen via a rebreathing facemask (ensuring no one-way valve is present), with a fractional inspired oxygen (FiO2) of 25-40% and an oxygen flow rate of ≤ 5 L/min.

Treatment:

Behavioral: Normobaric Facemask Oxygen

Control group

Description:

Patients who received oxygen via nasal cannula or did not receive oxygen therapy.

Treatment:

Behavioral: control group