Cerebral blood flow in traumatic contusions is predominantly reduced after an induced acute elevation of cerebral perfusion pressure

The Impact of Inotropes and Vasopressors on Cerebral Oxygenation in Patients with Traumatic Brain Injury and Subarachnoid Hemorrhage: A Narrative Review

Traumatic brain injury (TBI) and subarachnoid hemorrhage (SAH) are critical neurological conditions that necessitate specialized care in the Intensive Care Unit (ICU). Managing cerebral perfusion pressure (CPP) and mean arterial pressure (MAP) is of primary importance in these patients. To maintain targeted MAP and CPP, vasopressors and/or inotropes are commonly used. However, their effects on cerebral oxygenation are not fully understood. The aim of this review is to provide an up-to date review regarding the current uses and pathophysiological issues related to the use of vasopressors and inotropes in TBI and SAH patients. According to our findings, despite achieving similar hemodynamic parameters and CPP, the effects of various vasopressors and inotropes on cerebral oxygenation, local CBF and metabolism are heterogeneous. Therefore, a more accurate understanding of the cerebral activity of these medications is crucial for optimizing patient management in the ICU setting.

Feasibility of Doppler Ultrasound for Cortical Cerebral Blood Flow Velocity Monitoring During Major Non-cardiac Surgery of Newborns

Background and Aim: Newborns needing major surgical intervention are at risk of brain injury and impaired neurodevelopment later in life. Disturbance of cerebral perfusion might be an underlying factor. This study investigates the feasibility of serial transfontanellar ultrasound measurements of the pial arteries during neonatal surgery, and whether perioperative changes in cerebral perfusion can be observed and related to changes in the perioperative management. Methods: In this prospective, observational feasibility study, neonates with congenital diaphragmatic hernia and esophageal atresia scheduled for surgical treatment within the first 28 days of life were eligible for inclusion. We performed transfontanellar directional power Doppler and pulsed wave Doppler ultrasound during major high-risk non-cardiac neonatal surgery. Pial arteries were of interest for the measurements. Extracted Doppler ultrasound parameters were: peak systolic velocity, end diastolic velocity, the resistivity index and pulsatility index. Results: In 10 out of 14 patients it was possible to perform perioperative measurements; the others failed for logistic and technical reasons. In 6 out of 10 patients, it was feasible to perform serial intraoperative transfontanellar ultrasound measurements with directional power Doppler and pulsed wave Doppler of the same pial artery during neonatal surgery. Median peak systolic velocity was ranging between 5.7 and 7.0 cm s^-1 and end diastolic velocity between 1.9 and 3.2 cm s^-1. In patients with a vasoactive-inotropic score below 12 the trend of peak systolic velocity and end diastolic velocity corresponded with the mean arterial blood pressure trend. Conclusion: Perioperative transfontanellar ultrasound Doppler measurements of the pial arteries are feasible and provide new longitudinal data about perioperative cortical cerebral blood flow velocity. Trial Registration: https://www.trialregister.nl/trial/6972, identifier: NL6972.

The cerebrovascular response to norepinephrine: A scoping systematic review of the animal and human literature

Intravenous norepinephrine (NE) is utilized commonly in critical care for cardiovascular support. NE's impact on cerebrovasculature is unclear and may carry important implications during states of critical neurological illness. The aim of the study was to perform a scoping review of the literature on the cerebrovascular/cerebral blood flow (CBF) effects of NE. A search of MEDLINE, BIOSIS, EMBASE, Global Health, SCOPUS, and Cochrane Library from inception to December 2019 was performed. All manuscripts pertaining to the administration of NE, in which the impact on CBF/cerebral vasculature was recorded, were included. We identified 62 animal studies and 26 human studies. Overall, there was a trend to a direct vasoconstriction effect of NE on the cerebral vasculature, with conflicting studies having demonstrated both increases and decreases in regional CBF (rCBF) or global CBF. Healthy animals and those undergoing cardiopulmonary resuscitation demonstrated a dose-dependent increase in CBF with NE administration. However, animal models and human patients with acquired brain injury had varied responses in CBF to NE administration. The animal models indicate an increase in cerebral vasoconstriction with NE administration through the alpha receptors in vessels. Global and rCBF during the injection of NE displays a wide variation depending on treatment and model/patient.

In adult patients with severe traumatic brain injury, does the use of norepinephrine for augmenting cerebral perfusion pressure improve neurological outcome? A systematic review

BACKGROUND AND OBJECTIVE

Despite multiple interventions, mortality due to severe traumatic brain injury (sTBI) within mature Trauma Systems has remained unchanged over the last decade. During this time, the use of vasoactive infusions (commonly norepinephrine) to achieve a target blood pressure and cerebral perfusion pressure (CPP) has been a mainstay of sTBI management. However, evidence suggests that norepinephrine, whilst raising blood pressure, may reduce cerebral oxygenation. This study aimed to review the available evidence that links norepinephrine augmented CPP to clinical outcomes for these patients.

METHODS

A systematic review examining the evidence for norepinephrine augmented CPP in TBI patients was undertaken. Strict inclusion and exclusion criteria were developed for a dedicated literature search of multiple scientific databases. Two dedicated reviewers screened articles, whilst a third dedicated reviewer resolved conflicts.

RESULTS

The systematic review yielded 4,809 articles, of which 1,197 duplicate articles were removed. After abstract/title screening, 45 articles underwent full text review, resulting in the identification of two articles that investigated the effect of norepinephrine administration on clinical outcomes in patients following TBI when compared to other vasopressors. Neither study found a difference in neurological outcome between the vasopressor groups. No articles measured the effect of norepinephrine compared to no vasopressor use on the clinical outcome of patients with sTBI.

CONCLUSIONS

Despite being a mainstay of pharmacological management for hypotension in patients following sTBI, there is minimal clinical evidence supporting the use of norepinephrine in targeting a CPP for either improving neurological outcomes or reducing mortality. Outcomes-based clinical trials exploring the role of brain tissue perfusion and oxygenation monitoring are required to validate any benefit.

Transient Laterality of Cerebral Oxygenation Changes in Response to Head-of-Bed Manipulation in Acute Ischemic Stroke

Background: Cerebral oxygenation monitoring provides important information for optimizing individualized management in patients with acute ischemic stroke (AIS). Although changes in cerebral oxygenation are known to occur in response to head-of-bed (HOB) elevation within 72 h after onset, changes in cerebral oxygenation during stroke recovery are unclear. We compared changes in total- (tHb), oxygenated- (HbO2), and deoxygenated-hemoglobin (deoxyHb) concentrations in response to HOB manipulation between the timeframes within 72 h and 7–10 days after AIS onset. Methods: We measured forehead ΔtHb, ΔHbO2, and ΔdeoxyHb in response to HOB elevation (30°) within 72 h (first measurement) and 7–10 days (second measurement) after AIS onset using time-resolved near-infrared spectroscopy. Results: We enrolled 30 participants (mean age 72.8 ± 11.3 years; 13 women) with a first AIS. There were no significant differences in ΔtHb, ΔHbO2, or ΔdeoxyHb measurements on the infarct or contra-infarct side. At the first measurement, ΔtHb, ΔHbO2, and ΔdeoxyHb measured on the contra-infarct side did not correlate with those measured on the infarct side: ΔtHb (r = 0.114, p = 0.539); ΔHbO2 (r = 0.143, p = 0.440); ΔdeoxyHb (r = 0.227, p = 0.221). Notably, at the second measurement, correlation coefficients of ΔtHb and ΔHbO2 between the contra-infarct and infarct sides were statistically significant: ΔtHb (r = 0.491, p = 0.008); ΔHbO2 (r = 0.479, p = 0.010); ΔdeoxyHb (r = 0.358, p = 0.054). Conclusion: Although changes in cerebral oxygenation in response to HOB elevation had a laterality difference between hemispheres within 72 h of AIS onset, the difference had decreased, at least partially, 7–10 days after AIS onset.

Severely Elevated Blood Pressure and Early Mortality in Children with Traumatic Brain Injuries: The Neglected End of the Spectrum

Introduction

In adults with traumatic brain injuries (TBI), hypotension and hypertension at presentation are associated with mortality. The effect of age-adjusted blood pressure in children with TBI has been insufficiently studied. We sought to determine if age-adjusted hypertension in children with severe TBI is associated with mortality.

Methods

This was a retrospective analysis of the Department of Defense Trauma Registry (DoDTR) between 2001 and 2013. We included for analysis patients <18 years with severe TBI defined as Abbreviated Injury Severity (AIS) scores of the head ≥3. We defined hypertension as moderate for systolic blood pressures (SBP) between the 95^th and 99^th percentile for age and gender and severe if greater than the 99th percentile. Hypotension was defined as SBP <90 mmHg for children >10 years or < 70mmHg + (2 × age) for children ≤10 years. We performed multivariable logistic regression and Cox regression to determine if BP categories were associated with mortality.

Results

Of 4,990 children included in the DoDTR, 740 met criteria for analysis. Fifty patients (6.8%) were hypotensive upon arrival to the ED, 385 (52.0%) were normotensive, 115 (15.5%) had moderate hypertension, and 190 (25.7%) had severe hypertension. When compared to normotensive patients, moderate and severe hypertension patients had similar Injury Severity Scores, similar AIS head scores, and similar frequencies of neurosurgical procedures. Multivariable logistic regression demonstrated that hypotension (odd ratio [OR] 2.85, 95 confidence interval [CI] 1.26–6.47) and severe hypertension (OR 2.58, 95 CI 1.32–5.03) were associated with increased 24-hour mortality. Neither hypotension (Hazard ratio (HR) 1.52, 95 CI 0.74–3.11) nor severe hypertension (HR 1.65, 95 CI 0.65–2.30) was associated with time to mortality.

Conclusion

Pediatric age-adjusted hypertension is frequent after severe TBI. Severe hypertension is strongly associated with 24-hour mortality. Pediatric age-adjusted blood pressure needs to be further evaluated as a critical marker of early mortality.

Effect of melatonin on intracranial pressure and brain edema following traumatic brain injury: role of oxidative stresses

BACKGROUND AND AIMS

Traumatic brain injury (TBI) is one of the main causes of brain edema and increased intracranial pressure (ICP). In the clinic it is essential to limit the development of ICP after TBI. In the present study, the effects of melatonin on these parameters at different time points and alterations of oxidant factors as one of the probable involved mechanisms have been evaluated.

METHODS

Albino N-Mary rats were divided into five groups of sham, TBI, TBI + vehicle, TBI + Mel5 and TBI + Mel20. Brain injury was induced by Marmarou method. Melatonin was injected i.p. at 1, 24, 48 and 72 h after brain trauma. Brain water and Evans blue dye contents as well as oxidant/antioxidant factors were measured 72 h after TBI. ICP and neurological scores were determined at -1, 1, 24, 48 and 72 h post-TBI.

RESULTS

Brain water and Evans blue dye contents in melatonin-treated groups decreased as compared to the TBI + vehicle group (p <0.001). Veterinary coma scale (VCS) at 24, 48 and 72 h after TBI showed a significant increase in melatonin groups (TBI + Mel5: p <0.01 and TBI + Mel20: p <0.001) in comparison to the TBI + vehicle group. ICP at 24, 48 and 72 h after TBI decreased in melatonin groups as compared to the TBI + vehicle group (p <0.001). Superoxide dismutase and glutathione peroxidase activities showed a significant increase, whereas malondialdehyde level in these groups was significantly lower in melatonin groups in comparison to the TBI + vehicle group (p <0.001).

CONCLUSION

Melatonin decreases brain edema, BBB permeability and ICP, but increases VCS after TBI. These effects are probably due to inhibition of oxidative stress.

Favorable Outcome in Traumatic Brain Injury Patients With Impaired Cerebral Pressure Autoregulation When Treated at Low Cerebral Perfusion Pressure Levels

BACKGROUND:

Cerebral pressure autoregulation (CPA) is defined as the ability of the brain vasculature to maintain a constant blood flow over a range of different systemic blood pressures by means of contraction and dilatation.

OBJECTIVE:

To study CPA in relation to physiological parameters, treatment, and outcome in a series of traumatic brain injury patients.

METHODS:

In this prospective observational study, 44 male and 14 female patients (age, 15–72 years; mean, 38.7 years; Glasgow Coma Scale score, 4-13; median, 7) were analyzed. Patients were divided into groups on the basis of status of CPA (more pressure active vs more pressure passive) and level of cerebral perfusion pressure (CPP; low vs high CPP). The proportions of favorable outcome in the groups were assessed. Differences in physiological variables in the different groups were analyzed.

RESULTS:

Patients with more impaired CPA treated at CPP levels below median had a significantly higher proportion of favorable outcome compared with patients with more impaired CPA treated at CPP levels above median. No significant difference in outcome was seen between patients with more intact CPA when divided by level of CPP. In patients with more impaired CPA, CPP &lt; 50 mm Hg and CPP &lt; 60 mm Hg were associated with favorable outcome, whereas CPP &gt; 70 mm Hg and CPP &gt; 80 mm Hg were associated with unfavorable outcome. In patients with more intact CPA, no difference in physiological variables was seen between patients with favorable and unfavorable outcomes.

CONCLUSION:

Our results support that in traumatic brain injury patients with impaired CPA, CPP should not be elevated.

Hyperemia beneath evacuated acute subdural hematoma is frequent and prolonged in patients with an unfavorable outcome: a xe-computed tomographic study

OBJECTIVE

To verify the values and the time course of regional cerebral blood flow (rCBF) in the cortex located beneath an evacuated acute subdural hematoma (SDH) and their relationship with neurological outcome.

METHODS

rCBF levels were measured in multiple regions of interest, by means of a Xe-computed tomographic technique, in the cortex underlying an evacuated SDH and contralaterally in 20 patients with moderate or severe traumatic brain injury and an evacuated acute SDH. Twenty-three patients with moderate or severe traumatic brain injury and an evacuated extradural hematoma or diffuse injury served as the control group. Outcome was evaluated by means of the Glasgow Outcome Scale at 12 months.

RESULTS

Values for the maximum (rCBFmax) and the mean of all rCBF levels in the cortex beneath the evacuated SDH were more frequently consistent with hyperemia. The side-to-side differences in the mean of all rCBF and rCBFmax levels between lesioned and nonlesioned hemispheres were greater in patients with evacuated SDH than in controls (P = 0.0013 and P = 0.0018, respectively). The side-to-side difference in the maximum rCBF value was higher in SDH patients with unfavorable outcomes than in controls at 24 to 96 hours and at 4 to 7 days and higher than in patients with favorable outcomes at 4 to 7 days. The widest side-to-side difference in rCBFmax value was more elevated in patients with an evacuated SDH with unfavorable outcome than in patients with a favorable outcome (P = 0.047), whereas no differences were found in controls. The SDH thickness and the associated midline shift were greater in patients with unfavorable outcomes than in those with favorable outcomes.

CONCLUSION

On average, hyperemic long-lasting rCBF values frequently occur in the cortex located beneath an evacuated SDH and seem to be associated with unfavorable outcome.

Brain oxygen balance under various experimental pathophysiologycal conditions

Normally, brain tissue copes with negative oxygen balance by increasing cerebral blood flow (CBF). We examined the effects of increasing oxygen demand, by inducing spreading depression (SD) under various oxygen balance states, on brain O2 balance. The Tissue Vitality Monitoring System was used, which enables real time simultaneous in vivo monitoring of CBF, mitochondrial NADH and tissue HbO2 from the same region of the cerebral cortex. SD was induced during normoxia, hypoxia, hyperoxia, ischemia, and in normal and ischemic brain after systemic epinephrine administration. Under normoxia, hyperoxia and ischemia & epinephrine, the compensation of energy demand induced by SD, was carried out by increasing CBF. The higher oxygen delivery under hyperoxia and epinephrine did not change the pattern of recovery from SD as compared to normoxia, whereas in the ischemic and hypoxic brain, the recovery from SD was prolonged, indicating a lake in oxygen delivery. Epinephrine infusion in the ischemic rat, decreased oxyhemoglobin utilization during SD, indicating that tissue oxygen balance improves even under higher oxygen demand induced by SD.

Transcranial optical monitoring of cerebrovascular hemodynamics in acute stroke patients

"Diffuse correlation spectroscopy" (DCS) is a technology for non-invasive transcranial measurement of cerebral blood flow (CBF) that can be hybridized with "near-infrared spectroscopy" (NIRS). Taken together these methods hold potential for monitoring hemodynamics in stroke patients. We explore the utility of DCS and NIRS to measure effects of head-of-bed (HOB) positioning at 30 degrees , 15 degrees , 0 degrees , -5 degrees and 0 degrees angles in patients with acute ischemic stroke affecting frontal cortex and in controls. HOB positioning significantly altered CBF, oxy-hemoglobin (HbO(2)) and total-hemoglobin (THC) concentrations. Moreover, the presence of an ipsilateral infarct was a significant effect for all parameters. Results are consistent with the notion of impaired CBF autoregulation in the infarcted hemisphere.

Decompressive craniectomy as the primary surgical intervention for hemorrhagic contusion

The standard surgical treatment of hemorrhagic cerebral contusion is craniotomy with evacuation of the focal lesion. We assessed the safety and feasibility of performing decompressive craniectomy and duraplasty as the primary surgical intervention in this group of patients. Fifty-four consecutive patients with Glasgow Coma Scale (GCS) scores of less than or equal to 8, a frontal or temporal hemorrhagic contusion greater than 20 cm(3) in volume, and a midline shift of at least 5 mm or cisternal compression on computer tomography (CT) scan were studied. Sixteen (29.7%) underwent traditional craniotomy with hematoma evacuation, and 38 (70.4%) underwent craniectomy as the primary surgical treatment. Mortality, reoperation rate, Glasgow Outcome Scale-Extended (GOSE) scores, and length of stay in both the acute care and rehabilitation phase were compared between these two groups. Mortality (13.2% vs. 25.0%) and reoperation rate (7.9% vs. 37.5%) were lower in the craniectomy group, whereas the length of stay in both the acute care setting and the rehabilitation phase were similar between these two groups. The craniectomy group also had better GOSE score (5.55 vs. 3.56) at 6 months. Decompressive craniectomy is safe and effective as the primary surgical intervention for treatment of hemorrhagic contusion. This study also suggests that patient with hemorrhagic contusion can possibly have better outcome after craniectomy than other subgroup of patients with severe traumatic brain injury.