Cerebral Autoregulation and Severe Coronavirus Disease 19 [CA-COVID]: a Single-center Physiological Study

Background and Rationale:

Septic encephalopathy is a serious complication of sepsis / septic shock. In postmortem, human brain samples, two forms of neuraxonal injury have been described, namely, scattered ischemic lesions and diffuse injury. Prior evidence suggests that cerebral autoregulation is impaired in patients with septic shock, and this may render the central nervous system more vulnerable to direct ischemic damage, especially during episodes of hypotension. Recent observational data suggest that impaired cerebral autoregulation is associated with death within 3 months in patients with septic shock. Near-infrared spectroscopy (NIRS) constitutes an established method of noninvasive assessment of cerebral autoregulation and also provides the capability of semiquantitative assessment of regional cerebral blood flow. Severe coronavirus disease (COVID-19) is characterized by hypoxemia due to pneumonia, thromboembolic events that often affect the cerebral and pulmonary vascular network, vasodilatory shock and multiorgan failure. Pathophysiological mechanisms have features in common with those of septic shock and include "cytokine storm", diffuse vascular endothelial involvement, micro- and macro-vascular thrombosis and dysregulation of micro-circulation and vascular tone. In the present study, the following 3 hypotheses will be tested: 1. Cerebral autoregulation is likely to be severely impaired or even abolished in patients with COVID-19 who require admission to an Intensive Care Unit (ICU). In addition, the correlation between the NIRS Tissue Oxygenation Index and the mean arterial pressure may be stronger in COVID-19 compared to septic shock and comparable to that determined after cardiac arrest. 2. Cerebral autoregulation is likely to be associated with known COVID-19 severity markers such as lymphopenia and elevated C-reactive protein (CRP), ferritin, delta dimers (D-dimers) and lactate dehydrogenase (LDH) 3. The early (ie on ICU days 1 and 3) absence of cerebral autoregulation is likely to be associated with residual neurological deficits.

METHODS:

NIRS monitoring will be performed for approximately 90 minutes at 2 mean blood pressure levels (MAP, i.e. 65-70 mmHg and 95-100 mmHg) within 12-48 hours and 60-84 hours after admission to the ICU for severe COVID-19 infection. Autoregulation will be assessed using Tissue Oxygenation Index values and mean arterial pressure (MAP) values in a regression analysis and will be considered sufficient if the relative Pearson correlation coefficient is less than 0.3 Cerebral blood flow will be assessed by blood flow index (BFI) determination after intravenous infusion of 5 mg indocyanine.

ICU Protocol: All COVID-19 patients participating in this study will be treated in a standardized manner that includes: An intermediate dose of Enoxaparin, e.g. 4000 units x 2 subcutaneously 2. Treatment with remdesivir and dexamethasone 3. Up to 2 broad-spectrum antibiotics to treat possibly co-existing bacterial respiratory tract infection 4. A conservative fluid management strategy 5. A protective ventilation strategy in a semirecumbent position 5. Anesthesia with Midazolam, Propofol and Remifentanil 7. Enteral nutrition that will start within 24 hours after admission to the ICU, 8. Permissive hyperglycemia (blood glucose 150-200 mg / dL).