Hypertension and Cerebrovascular Hemodynamics in General Anaesthesia

Plain-language summary

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 with the same medication as used during the surgery. After the MRI: Participants will be woken up in the anesthesia preparation room next to the MRI scanner. The arterial catheter will be removed before awakening. Participants will be transported to the postoperative unit for monitoring. The surgeon responsible for care will determine the discharge time. Possible Risks and Side Effects of Participation Transporting an anesthetized patient for an MRI scan outside the operating room carries some risks. However, the hospital has established procedures for daily transportation of anesthetized patients and a structured division of responsibilities to manage unexpected situations. Monitoring will be conducted by an experienced anesthesiologist and anesthesia nurse throughout the procedure. Routine monitoring includes blood pressure, heart rate, depth of anesthesia, and oxygen levels. No long-term effects have been observed from MRI scans or short-term anesthesia for these examinations. Most complications related to general anesthesia occur during induction or awakening, and these risks exist regardless of study participation. Study participation may slightly increase the risk of IV lines or breathing tubes becoming dislodged due to movement while anesthetized. A prolonged period under anesthesia may cause slight additional fatigue upon waking. To ensure understanding of the information about this study, participants will take a simple cognitive test (5 minutes) before surgery. If any unexpected complications arise during surgery, study participation will be discontinued. If the MRI scan reveals any abnormalities, referral to a neurologist or neurosurgeon for further evaluation will be provided. What Happens to Collected Data? The project will collect health information from medical records and MRI scans. All data will be pseudonymized (coded) so that it cannot be linked to individual participants. The key to decoding this information will be stored securely by the research nurse at the Neuro-Head-Neck Center (NHHC). Only authorized research personnel will have access to the pseudonymized data. Information will be protected in accordance with the General Data Protection Regulation (GDPR).

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