Hypertension and Cerebrovascular Hemodynamics in General Anaesthesia

Conditions studied

Anesthesia, Cerebral Blood Flow, Regional Cerebral Oxygen Saturation, Blood Pressure

About this study

During anesthesia, blood pressure-raising medications are often required to achieve an adequate blood pressure level. However, there is limited knowledge about what constitutes an adequate blood pressure to ensure sufficient blood flow to the brain. This project aims to map the relationship between blood pressure and brain blood flow using an MRI scanner. The results will contribute to a better understanding of this relationship and lead to improved management of brain blood flow during surgery on anesthetized patients. How does the project work? Day 1 Before planned surgery, participants will meet with an anesthesiologist for information and assessment. An MRI scan of the brain will be conducted while participants are awake. The MRI examination has no side effects or risks. The space inside the MRI scanner is tight, especially around the head. If discomfort is experienced, the examination will be stopped immediately. The machine is noisy, so hearing protection will be provided, and communication with staff will be possible throughout the examination. The scan takes approximately 30 minutes, during which participants only need to lie still and relax. Day 2 After planned surgery, an anesthesiologist and an anesthesia nurse will transfer participants to the MRI scanner while still under anesthesia. Participants will not be woken up between surgery and the MRI scan; instead, transportation will occur while still anesthetized, following standard hospital procedures. Participants will remain under the same anesthetic drugs as during the surgery. The same blood pressure-raising medication, norepinephrine, will be continuously used. No additional drugs, beyond those necessary for normal anesthesia, will be administered before the MRI examination. The entire project will take about 1.5 hours in addition to the surgery. If an arterial catheter (a blood pressure monitor via an artery in the wrist) is not already in place, one will be inserted while participants are asleep. Before the MRI examination: Baseline examination - If any abnormalities are detected, the scan will be stopped, and follow-up by a doctor will occur. Blood pressure increase - Blood pressure will be raised by approximately 30% (equivalent to mild physical activity, such as jogging). Follow-up scan at the higher blood pressure level. Blood pressure returns to normal. All blood pressure levels will remain within clinically acceptable ranges for anesthetized patients and will be regulated…

Interventions

• Other: Blood pressure elevation — Increasing systemic blood pressure for measurement of cerebral blood flow changes

Primary outcomes

• Cerebral blood flow (1 hour)
• rSO2 (1 hour)

Eligibility information

Study locations

• Umeå University Hospital, Umeå, Sweden