Cerebral Blood Flow and Oxygen Delivery in Aneurysmal Subarachnoid Hemorrhage: Relation to Neurointensive Care Targets

Abstract

Background The primary aim was to determine to what extent continuously monitored neurointensive care unit (neuro-ICU) targets predict cerebral blood flow (CBF) and delivery of oxygen (CDO2) after aneurysmal subarachnoid hemorrhage. The secondary aim was to determine whether CBF and CDO2 were associated with clinical outcome. Methods In this observational study, patients with aneurysmal subarachnoid hemorrhage treated at the neuro-ICU in Uppsala, Sweden, from 2012 to 2020 with at least one xenon-enhanced computed tomography (Xe-CT) obtained within the first 14 days post ictus were included. CBF was measured with the Xe-CT and CDO2 was calculated based on CBF and arterial oxygen content. Regional cerebral hypoperfusion was defined as CBF < 20 mL/100 g/min, and poor CDO2 was defined as CDO2 < 3.8 mL O2/100 g/min. Neuro-ICU variables including intracranial pressure (ICP), pressure reactivity index, cerebral perfusion pressure (CPP), optimal CPP, and body temperature were assessed in association with the Xe-CT. The acute phase was divided into early phase (day 1–3) and vasospasm phase (day 4–14). Results Of 148 patients, 27 had underwent a Xe-CT only in the early phase, 74 only in the vasospasm phase, and 47 patients in both phases. The patients exhibited cerebral hypoperfusion and poor CDO2 for medians of 15% and 30%, respectively, of the cortical brain areas in each patient. In multiple regressions, higher body temperature was associated with higher CBF and CDO2 in the early phase. In a similar regression for the vasospasm phase, younger age and longer pulse transit time (lower peripheral resistance) correlated with higher CBF and CDO2, whereas lower hematocrit only correlated with higher CBF but not with CDO2. ICP, CPP, and pressure reactivity index exhibited no independent association with CBF and CDO2. R2 of these regressions were below 0.3. Lower CBF and CDO2 in the early phase correlated with poor outcome, but this only held true for CDO2 in multiple regressions. Conclusions Systemic and cerebral physiological variables exhibited a modest association with CBF and CDO2. Still, cerebral hypoperfusion and low CDO2 were common and low CDO2 was associated with poor outcome. Xe-CT imaging could be useful to help detect secondary brain injury not evident by high ICP and low CPP.

Higher intracranial pressure variability is associated with lower cerebrovascular resistance in aneurysmal subarachnoid hemorrhage

“…ICPV-30m and ICPV-4h evaluates the deviation of absolute ICP in relation to the average ICP for a 30-min/4-h time window and these two could have been influenced by an open EVD to some extent. The associations between ICPV-4h and CBF and CVR were relatively weak, however this was to some extent expected considering the vast amount of variables involved in the regulation of the cerebral vessels and CBF [22].…”

“…The Xe-CT CBF imaging procedures were done in accordance with the principles described by Gur et al [16] and Yonas et al [17,18] and has been described in detail in previous studies by our group [19][20][21][22][23]. In brief, the procedure is based on the principle that inhaled xenon gas dissolves in blood and tissues.…”

Fine tuning of neurointensive care in aneurysmal subarachnoid hemorrhage: From one-size-fits-all towards individualized care

“…However, even in case of normal ICP and CPP, disturbances in CBF, btO 2 , and cerebral energy metabolism are frequent. 8 , 12 , 13 , 14 For that reason, there has been a development of MMM tools to enable monitoring of the different steps to achieve cerebral energy metabolism ( Table 1 , Table 2 ). Monitoring may then also include cerebral pressure autoregulation (pressure reactivity index, mean flow index), CBF (intraparenchymal probes, transcranial Doppler, and radiological imaging), brain tissue oxygenation (jugular bulb, btO 2 ), and cerebral energy metabolism (microdialysis and radiological imaging).…”

“…It is key to maintain a sufficiently high CBF to achieve adequate CDO 2 and CDGlc/CDLac. CBF disturbances are common in aSAH 8 and may be attributed to several pathomechanisms, as discussed below.…”

“…Third, current NIC targets such as ICP and CPP are only surrogates of the cerebral environment, but their validity to predict the actual intracranial state globally and focally may be questioned. 7 , 8 The development of new multimodality monitoring (MMM) tools to assess cerebral blood flow (CBF; imaging and invasive probes), CBF autoregulation (e.g. pressure reactivity index), brain tissue oxygenation (btO 2 and jugular bulb), and cerebral energy metabolism (microdialysis) have improved our understanding of disease pathophysiology and the cerebral effects of treatments, but their validity to guide management still remains unclear considering their inherent temporal, spatial, and logistical constraints.…”