Intracranial pressure dynamics and cerebral vasomotor reactivity in community-acquired bacterial meningitis during neurointensive care

OBJECTIVE Community-acquired bacterial meningitis (CABM) is a severe condition associated with high mortality. In this study the first aim was to evaluate the incidence of intracranial pressure (ICP) insults and disturbances in cerebral vasomotor reactivity and the second aim was to evaluate the management and clinical outcome of CABM patients treated in the neurointensive care unit (NICU). METHODS CABM patients who were treated in the NICU of Uppsala University Hospital, Sweden, during 2008–2020 were included in the study. Data on demographics, admission variables, treatment, ICP dynamics, vasomotor reactivity, and short-term clinical outcome were evaluated in these patients. RESULTS Of 97 CABM patients, 81 (84%) received ICP monitoring, of whom 22% had ICP > 20 mm Hg during 5% or more of the monitoring time on day 1, which decreased to 9% on day 3. For those patients with ICP monitoring, 46% required CSF drainage, but last-tier ICP treatment, including thiopental (4%) and decompressive craniectomy (1%), was rare. Cerebral vasomotor reactivity was disturbed, with a mean pressure reactivity index (PRx) above 0.2 in 45% of the patients on day 1, and remained high for the first 3 days. In total, 81 (84%) patients had a favorable outcome (Glasgow Coma Scale motor score [GCS M] 6) at discharge, 9 (9%) patients had an unfavorable outcome (GCS M < 6) at discharge, and 7 (7%) patients died in the NICU. Those with favorable outcome had significantly better cerebral vasomotor reactivity (lower PRx) than the two other outcome groups (p < 0.01). CONCLUSIONS Intracranial hypertension was frequent following severe CABM and CSF drainage was often sufficient to control ICP. Cerebral vasomotor reactivity was commonly disturbed and associated with poor outcome. Clinical outcome was slightly better than in earlier studies.

One-year Aerobic Exercise Altered Cerebral Vasomotor Reactivity in Mild Cognitive Impairment

The purpose of this study was to test the hypothesis that changes in cerebral vasomotor reactivity (CVMR) after one-year aerobic exercise training (AET) are associated with cognitive performances in individuals with amnestic mild cognitive impairment (MCI). Seventy sedentary patients with amnestic MCI were randomized to one-year moderate to vigorous intensity AET or stretching and toning (SAT) interventions. Cerebral blood flow velocity (CBFV) with transcranial Doppler, mean arterial pressure (MAP) with finapres plethysmograph, and EtCO2 with capnography were measured during hyperventilation (hypocapnia) and a modified rebreathing protocol (hypercapnia) to assess CVMR. Cerebrovascular conductance index (CVCi) was calculated by CBFV/MAP, and CVMR by ΔCBFV/ΔEtCO2 and ΔCVCi/ΔEtCO2. Episodic memory and executive function were assessed using standard neuropsychological tests (CVLT-II and D-KEFS). Cardiorespiratory fitness was assessed by peak oxygen uptake (VO2peak). A total of 37 patients (19 in SAT and 18 in AET) completed one-year interventions and CVMR assessments. AET improved VO2peak, increased hypocapnic CVMR, but decreased hypercapnic CVMR. AET effects on cognitive performance were minimal when compared with SAT. Across both groups, there was a negative correlation between changes in hypo- and hypercapnic CVMRs in CBFV% and CVCi% (r = -0.741, r = -0.725, p < 0.001). Attenuated hypercapnic CVMR, but not increased hypocapnic CVRM, was associated with improved cognitive test scores in the AET group. In conclusion, one-year AET increased hypocapnic CVMR and attenuated hypercapnic CVMR which is associated cognitive performance in patients with amnestic MCI.

Comparisons of the Nonlinear Relationship of Cerebral Blood Flow Response and Cerebral Vasomotor Reactivity to Carbon Dioxide under Hyperventilation between Postural Orthostatic Tachycardia Syndrome Patients and Healthy Subjects

Postural orthostatic tachycardia syndrome (POTS) typically occurs in youths, and early accurate POTS diagnosis is challenging. A recent hypothesis suggests that upright cognitive impairment in POTS occurs because reduced cerebral blood flow velocity (CBFV) and cerebrovascular response to carbon dioxide (CO2) are nonlinear during transient changes in end-tidal CO2 (PETCO2). This novel study aimed to reveal the interaction between cerebral autoregulation and ventilatory control in POTS patients by using tilt table and hyperventilation to alter the CO2 tension between 10 and 30 mmHg. The cerebral blood flow velocity (CBFV), partial pressure of end-tidal carbon dioxide (PETCO2), and other cardiopulmonary signals were recorded for POTS patients and two healthy groups including those aged >45 years (Healthy-Elder) and aged <45 years (Healthy-Youth) throughout the experiment. Two nonlinear regression functions, Models I and II, were applied to evaluate their CBFV-PETCO2 relationship and cerebral vasomotor reactivity (CVMR). Among the estimated parameters, the curve-fitting Model I for CBFV and CVMR responses to CO2 for POTS patients demonstrated an observable dissimilarity in CBFVmax (p = 0.011), mid-PETCO2 (p = 0.013), and PETCO2 range (p = 0.023) compared with those of Healthy-Youth and in CBFVmax (p = 0.015) and CVMRmax compared with those of Healthy-Elder. With curve-fitting Model II for POTS patients, the fit parameters of curvilinear (p = 0.036) and PETCO2 level (p = 0.033) displayed significant difference in comparison with Healthy-Youth parameters; range of change (p = 0.042), PETCO2 level, and CBFVmax also displayed a significant difference in comparison with Healthy-Elder parameters. The results of this study contribute toward developing an early accurate diagnosis of impaired CBFV responses to CO2 for POTS patients.

Cerebral Vasomotor Reactivity in Amnestic Mild Cognitive Impairment

Background: Cerebral blood flow (CBF) is sensitive to changes in arterial CO2, referred to as cerebral vasomotor reactivity (CVMR). Whether CVMR is altered in patients with amnestic mild cognitive impairment (aMCI), a prodromal stage of Alzheimer disease (AD), is unclear. Objective: To determine whether CVMR is altered in aMCI and is associated with cognitive performance. Methods: Fifty-three aMCI patients aged 55 to 80 and 22 cognitively normal subjects (CN) of similar age, sex, and education underwent measurements of CBF velocity (CBFV) with transcranial Doppler and end-tidal CO2 (EtCO2) with capnography during hypocapnia (hyperventilation) and hypercapnia (rebreathing). Arterial pressure (BP) was measured to calculate cerebrovascular conductance (CVCi) to normalize the effect of changes in BP on CVMR assessment. Cognitive function was assessed with Mini-Mental State Examination (MMSE) and neuropsychological tests focused on memory (Logical Memory, California Verbal Learning Test) and executive function (Delis-Kaplan Executive Function Scale; DKEFS). Results: At rest, CBFV and MMSE did not differ between groups. CVMR was reduced by 13% in CBFV% and 21% in CVCi% during hypocapnia and increased by 22% in CBFV% and 20% in CVCi% during hypercapnia in aMCI when compared to CN (all p < 0.05). Logical Memory recall scores were positively correlated with hypocapnia (r = 0.283, r = 0.322, p < 0.05) and negatively correlated with hypercapnic CVMR measured in CVCi% (r = –0.347, r = –0.446, p < 0.01). Similar correlations were observed in D-KEFS Trail Making scores. Conclusion: Altered CVMR in aMCI and its associations with cognitive performance suggests the presence of cerebrovascular dysfunction in older adults who have high risks for AD.