Regional cerebral blood flow response to hypocapnia in the contralateral hemisphere of patients with acute cerebral infarction

To Tube or Not to Tube? The Role of Intubation during Stroke Thrombectomy

In the 10 years since the FDA first cleared the use of endovascular devices for the treatment of acute stroke, definitive evidence that such therapy improves outcomes remains lacking. The decision to intubate patients undergoing stroke thrombectomy impacts multiple variables that may influence outcomes after stroke. Three main areas where intubation may deleteriously affect acute stroke management include the introduction of delays in revascularization, fluctuations in peri-procedural blood pressure, and hypocapnia, resulting in cerebral vasoconstriction. In this mini-review, we discuss the evidence supporting these limitations of intubation during stroke thrombectomy and encourage neurohospitalists, neurocritical care specialists, and neurointerventionalists to carefully consider the decision to intubate during thrombectomy and provide strategies to avoid potential complications associated with its use in acute stroke.

Cerebral blood flow changes in the primary motor and premotor cortices during hyperventilation

The aim of this study was to clarify the regional differences in cerebral blood flow (CBF) change during hyperventilation by using H2(15)O and positron emission tomography (PET). Eight healthy volunteers (age: 63.0 +/- 8.9 yr.) were studied. Regional CBF was measured by the H2(15)O autoradiographic method and PET. Statistical parametric maps (SPM) and conventional regions of interest (ROI) analysis were used for estimating regional CBF differences in the normocapnic state with normal breathing and the hypocapnic state induced by hyperventilation. Total CBF decreased during the hypocapnic state. The SPM revealed that primary motor and premotor cortices were significantly activated by hyperventilation. In these areas absolute CBF values were significantly higher than those in the temporal, occipital and parietal lobes in the hypocapnic state, but there were no significant regional differences in the normocapnic state. In the hypocapnic state induced by hyperventilation, the primary motor and premotor CBF shows combined changes with vasoreaction to hypocapnia and increase in activation due to hyperventilation.

Local cerebral glucose utilization in chronic middle cerebral artery occlusion in the cat

This study examines the correlation between local CMRglc (LCMRglc) alterations and clinicopathological changes in a chronic middle cerebral artery (MCA) occlusion model in the cat. The left MCA was occluded for a period of 2 h. The animals were grouped into mild, moderate, and severe ischemia based on the depression of the EEG 30 min after the MCA occlusion. Following release of the clip, the animals were allowed to recover for a week during which time daily neurological examinations were performed. On the seventh day [14C]2-deoxyglucose was injected for the determination of LCMRglc. Alternative blocks were processed for histological evaluation in which both neuronal and phagocytic changes were graded into four categories (0 = normal to 3 = severe). LCMRglc (mumol/100 g/min) in the ischemic hemisphere (all histological grades) was significantly lower than the metabolic rate in comparable regions of the sham MCA occlusion group. Regions with significant phagocytosis (grade 2 and 3) invariably exhibited activated glucose metabolism (57.4 +/- 8.4 and 105.9 +/- 6.8 mumol/100 g/min, respectively), which was significantly higher than in regions without phagocytosis (30.4 +/- 0.8 mumol/100 g/min). There was a significant gradient of metabolism in the central, peripheral, and boundary zone and the non-MCA territory in the animals with severe ischemic lesions. LCMRglc in the central MCA territory was well correlated with the EEG amplitude changes (r = 0.82, p less than 0.05) and the morphological score (r = -0.89, p less than 0.05). The metabolic rate was significantly depressed in both the ipsilateral and the contralateral central MCA territories in comparison with the sham occlusion animals. The depression in LCMRglc in the contralateral hemisphere correlated well with the concomitant depression in the contralateral EEG amplitude. These studies demonstrate that local heterogeneous metabolic alterations and contralateral cortical diaschisis exist chronically following temporary MCA occlusion and that the increases in local cerebral glucose metabolism seen in chronic stroke may be due to phagocytotic activity.

Chronic brain ischemia in the monkey assessed by somatosensory evoked potentials and local blood flow measurements

Physiological changes occurring in experimentally induced chronic ischemic areas of the brain in monkeys have been investigated by measuring local cerebral blood flow (lCBF) and recording somatosensory evoked potentials (SEPs) to median nerve stimulation in the cortex and thalamus (VPL). Ischemia was produced by occlusion of the middle cerebral artery (MCA). Its development was followed for weeks in the unanesthetized monkey. SEPs in VPL and cortex were shown to be useful indicators of neuronal activity in the course of brain ischemia. The most reliable parameters were found to be the amplitude of components P10, P12 and P20 of the cortical SEP, generated around the central sulcus. The relationship between the changes in spontaneous recovery of the SEPs, lCBF and behavioral signs, in the course of time, revealed characteristic patterns. Different components of the cortical SEP provide useful information on the localization of the ischemic cortical area. In addition, the amplitude of the VPL SEP may also change significantly after the occlusion of the MCA. Clear evidence for the phenomenon of diaschisis in terms of SEPs, was found in only one animal. An analysis of the relationship between lCBF and the amplitude of the SEPs showed that cortical SEPs could be measured at local CBF levels as low as 15 ml/100 g X min. The relationship between lCBF and cortical SEP amplitude was approximately linear in the range from about 60 ml/100 g X min down to 15 ml/100 g X min.

Cerebellar blood flow and metabolism in cerebral hemisphere infarction

Positron emission tomography was used to study the effect of supratentorial infarction on cerebellar metabolic rate for oxygen and cerebellar blood flow. In a control group of patients, the mean cerebellar metabolic rate for oxygen was 2.97 +/- 0.11 (standard error of the mean [SEM] ) ml-1 . min-1 . hg-1 and mean cerebellar blood flow was 41.1 +/- 1.5 ml . min-1 . hg-1. No significant right-left asymmetry in either cerebellar metabolic rate for oxygen or cerebellar blood flow was noted. Patients with frontal lobe infarction showed 16.8 +/- 1.8% (cerebellar metabolic rate for oxygen) and 19.6 +/- 2.1% (cerebellar blood flow) differences between cerebellar hemispheres, with the hemisphere contralateral to the cerebral infarction having the lower values. These differences were highly significant (p less than 0.001). In addition, cerebellar blood flow and cerebellar metabolic rate for oxygen were significantly decreased in the ipsilateral cerebellar hemisphere (metabolism: 2.13 +/- 0.19 ml . min-1 . hg-1; p less than 0.002; blood flow: 35.2 +/- 2.4 ml . min-1 . hg-1; p less than 0.05). Patients with parietooccipital infarction also showed a significant bilateral decrease in cerebellar metabolic rate for oxygen (2.43 +/- 0.11 ml . min-1 . hg-1) and cerebellar blood flow (34.6 +/- 2.5 ml . min-1 . hg-1) relative to control subjects, but no significant cerebellar asymmetry. Our findings demonstrate a general depression of cerebellar blood flow and metabolism from cerebral hemisphere infarction unrelated to the site of infarction as well as a specific depression occurring contralateral to infarction involving the frontal lobe. These are among the first quantitative data concerning regional cerebellar metabolic rates for oxygen and cerebellar blood flow in humans.

Blood flow and oxygen consumption of the focally traumatized monkey brain

The exposed left superior frontal gyrus of the anesthetized macaque brain was focally traumatized by a jet of compressed air. Focal blood flow in tissue around the lesion and total cerebral blood flow was determined before and during the 4 hours after trauma by the hydrogen clearance technique. Blood flow fell in tissue adjacent to the injured brain but the reduction was not statistically significant. Total cerebral blood flow, blood flow in the right superior-frontal gyrus, and oxygen consumption of the brain was unaffected by the trauma. The authors conclude that neither spreading ischemia within uninjured tissue surrounding focally traumatized brain nor posttraumatic diaschisis is readily provoked in the anesthetized brain of the monkey.