Cerebral perfusion pressure thresholds for brain tissue hypoxia and metabolic crisis after poor-grade subarachnoid hemorrhage

Multimodality monitoring in the neurointensive care unit: a special perspective for patients with stroke

Multimodality monitoring (MMM) is a recently developed method that aids in understanding real-time brain physiology. Early detection of physiological disturbances is possible with the help of MMM, which allows identification of underlying causes of deterioration and minimization of secondary brain injury (SBI). MMM is especially helpful in comatose patients with severe brain injury because neurological examinations are not sensitive enough to detect SBI. The variables frequently examined in MMM are hemodynamic parameters such as intracranial pressure, cerebral perfusion pressure, and mean arterial pressure; brainspecific oxygen tension; markers for brain metabolism including glucose, lactate, and pyruvate levels in brain tissue; and cerebral blood flow. Continuous electroencephalography can be performed, if needed. The majority of SBIs stem from brain tissue hypoxia, brain ischemia, and seizures, which lead to a disturbance in brain oxygen levels, cerebral blood flow, and electrical discharges, all of which are easily detected by MMM. In this review, we discuss the clinical importance of physiological variables as well as the practical applicability of MMM in patients with stroke.

Time course of recovery following poor-grade SAH: the incidence of delayed improvement and implications for SAH outcome study design

OBJECT

Data regarding the time course of recovery after poor-grade subarachnoid hemorrhage (SAH) is lacking. Most SAH studies assess outcome at a single time point, often as early as 3 or 6 months following SAH. The authors hypothesized that recovery following poor-grade SAH is a dynamic process and that early outcomes may not always approximate long-term outcomes. To test this hypothesis, they analyzed long-term outcome data from a cohort of patients with poor-grade aneurysmal SAH to determine the incidence and predictors of early and delayed neurological improvement.

METHODS

The authors reviewed outcome data from 88 poor-grade SAH patients enrolled in a prospective SAH treatment trial (the Barrow Ruptured Aneurysm Trial). They assessed modified Rankin Scale (mRS) scores at discharge, 6 months, 12 months, and 36 months after treatment to determine the incidence and predictors of neurological improvement during each interval.

RESULTS

The mean aggregate mRS scores at 6 months (3.31 ± 2.1), 12 months (3.28 ± 2.2), and 36 months (3.17 ± 2.3) improved significantly compared with the mean score at hospital discharge (4.33 ± 1.3, p < 0.001), but they did not differ significantly among themselves. Between discharge and 6 months, 61% of patients improved on the mRS. The incidence of improvement between 6-12 months and 12-36 months was 18% and 19%, respectively. Hunt and Hess Grade IV versus V (OR 6.20, 95% CI 2.11-18.25, p < 0.001) and the absence of large (> 4 cm) (OR 2.76, 95% CI 1.02-7.55, p = 0.05) or eloquent (OR 5.17, 95% CI 1.89-14.10, p < 0.01) stroke were associated with improvement up to 6 months. Age ≤ 65 years (OR 5.56, 95% CI 1.17-26.42, p = 0.02), Hunt and Hess Grade IV versus V (OR 4.17, 95% CI 1.10-15.85, p = 0.03), and absence of a large (OR 8.97, 95% CI 2.65-30.40, p < 0.001) or eloquent (OR 4.54, 95% CI 1.46-14.08, p = 0.01) stroke were associated with improvement beyond 6 months. Improvement beyond 1 year was most strongly predicted by the absence of a large stroke (OR 7.62, 95% CI 1.55-37.30, p < 0.01).

CONCLUSIONS

A substantial minority of poor-grade SAH patients will experience delayed recovery beyond the point at which most studies assess outcome. Younger patients, those presenting in better clinical condition, and those without CT evidence of large or eloquent stroke demonstrated the highest capacity for delayed recovery.

Parenteral diclofenac infusion significantly decreases brain-tissue oxygen tension in patients with poor-grade aneurysmal subarachnoid hemorrhage

Introduction

Diclofenac, a nonsteroidal antiinflammatory drug, is commonly used as antipyretic therapy in intensive care. The purpose of this study was to investigate the effects of parenteral diclofenac infusion on brain homeostasis, including brain-tissue oxygen tension (P_btO₂) and brain metabolism after aneurysmal subarachnoid hemorrhage (aSAH).

Methods

We conducted a prospective, observational study with retrospective analysis of 21 consecutive aSAH patients with multimodal neuromonitoring. Cerebral perfusion pressure (CPP), mean arterial pressure (MAP), intracranial pressure (ICP), body temperature, and P_btO₂ were analyzed after parenteral diclofenac infusion administered over a 34-minute period (20 to 45 IQR). Data are given as mean ± standard error of mean and median with interquartile range (IQR), as appropriate. Time-series data were analyzed by using a general linear model extended by generalized estimation equations (GEEs).

Results

One-hundred twenty-three interventions were analyzed. Body temperature decreased from 38.3°C ± 0.05°C by 0.8°C ± 0.06°C (P < 0.001). A 10% decrease in MAP and CPP (P < 0.001) necessitated an increase of vasopressors in 26% (n = 32), colloids in 33% (n = 41), and crystalloids in 5% (n = 7) of interventions. P_btO₂ decreased by 13% from a baseline value of 28.1 ± 2.2 mm Hg, resulting in brain-tissue hypoxia (P_btO₂ <20 mm Hg) in 38% (n = 8) of patients and 35% (n = 43) of interventions. P_btO₂ <30 mm Hg before intervention was associated with brain-tissue hypoxia after parenteral diclofenac infusion (likelihood ratio, 40; AUC, 93%; 95% confidence interval (CI), 87% to 99%; P < 0.001). Cerebral metabolism showed no significant changes after parenteral diclofenac infusion.

Conclusions

Parenteral diclofenac infusion after aSAH effectively reduces body temperature, but may lead to CPP decrease and brain-tissue hypoxia, which were both associated with poor outcome after aSAH.

Patterns in neurosurgical adverse events: open cerebrovascular neurosurgery

OBJECT

As part of a project to devise evidence-based safety interventions for specialty surgery, we sought to review current evidence concerning the frequency of adverse events in open cerebrovascular neurosurgery and the state of knowledge regarding methods for their reduction. This review represents part of a series of papers written to consolidate information about these events and preventive measures as part of an ongoing effort to ascertain the utility of devising system-wide policies and safety tools to improve neurosurgical practice.

METHODS

The authors performed a PubMed search using search terms "cerebral aneurysm", "cerebral arteriovenous malformation", "intracerebral hemorrhage", "intracranial hemorrhage", "subarachnoid hemorrhage", and "complications" or "adverse events." Only papers that specifically discussed the relevant complication rates were included. Papers were chosen to be included to maximize the range of rates of occurrence for the reported adverse events.

RESULTS

The review revealed hemorrhage-related hyperglycemia (incidence rates ranging from 27% to 71%) and cerebral salt-wasting syndromes (34%-57%) to be the most common perioperative adverse events related to subarachnoid hemorrhage (SAH). Next in terms of frequency was new cerebral infarction associated with SAH, with a rate estimated at 40%. Many techniques are advocated for use during surgery to minimize risk of this development, including intraoperative neurophysiological monitoring, but are not universally used due to surgeon preference and variable availability of appropriate staffing and equipment. The comparative effectiveness of using or omitting monitoring technologies has not been evaluated. The incidence of perioperative seizure related to vascular neurosurgery is unknown, but reported seizure rates from observational studies range from 4% to 42%. There are no standard guidelines for the use of seizure prophylaxis in these patients, and there remains a need for prospective studies to support such guidelines. Intraoperative rupture occurs at a rate of 7% to 35% and depends on aneurysm location and morphology, history of rupture, surgical technique, and surgeon experience. Preventive strategies include temporary vascular clipping. Technical adverse events directly involving application of the aneurysm clip include incomplete aneurysm obliteration and parent vessel occlusion. The rates of these events range from 5% to 18% for incomplete obliteration and 3% to 12% for major vessel occlusion. Intraoperative angiography is widely used to confirm clip placement; adjuncts include indocyanine green video angiography and microvascular Doppler ultrasonography. Use of these technologies varies by institution.

DISCUSSION

A significant proportion of these complications may be avoidable through development and testing of standardized protocols to incorporate monitoring technologies and specific technical practices, teamwork and communication, and concentrated volume and specialization. Collaborative monitoring and evaluation of such protocols are likely necessary for the advancement of open cerebrovascular neurosurgical quality.

Potential blood biomarkers for stroke

Stroke is one of the most common causes of death worldwide and a major cause of acquired disability in adults. Despite advances in research during the last decade, prevention and treatment strategies still suffer from significant limitations, and therefore new theoretical and technical approaches are required. Technological advances in the proteomic and metabolomic areas, during recent years, have permitted a more effective search for novel biomarkers and therapeutic targets that may allow for effective risk stratification and early diagnosis with subsequent rapid treatment. This review provides a comprehensive overview of the latest candidate proteins and metabolites proposed as new potential biomarkers in stroke.

Clinical review: neuromonitoring - an update

Critically ill patients are frequently at risk of neurological dysfunction as a result of primary neurological conditions or secondary insults. Determining which aspects of brain function are affected and how best to manage the neurological dysfunction can often be difficult and is complicated by the limited information that can be gained from clinical examination in such patients and the effects of therapies, notably sedation, on neurological function. Methods to measure and monitor brain function have evolved considerably in recent years and now play an important role in the evaluation and management of patients with brain injury. Importantly, no single technique is ideal for all patients and different variables will need to be monitored in different patients; in many patients, a combination of monitoring techniques will be needed. Although clinical studies support the physiologic feasibility and biologic plausibility of management based on information from various monitors, data supporting this concept from randomized trials are still required.

Acute effects of nimodipine on cerebral vasculature and brain metabolism in high grade subarachnoid hemorrhage patients

BACKGROUND

Nimodipine is the only medication shown to improve outcomes after aneurysmal subarachnoid hemorrhage (SAH). Preliminary theories regarding the mechanism by which it prevents vasospasm have been challenged. The acute physiologic and metabolic effects of oral Nimodipine have not been examined in patients with poor-grade SAH.

METHODS

This is an observational study performed in 16 poor-grade SAH patients undergoing multimodality monitoring who received oral Nimodipine as part of routine clinical care. A total of 663 doses of Nimodipine were observed. Changes in physiologic measurements including MAP, CPP, ICP, P(bt)O(2), and CBF were examined.

RESULTS

Administration of oral Nimodipine was associated with a 1.33 mmHg decrease in MAP (P < 0.001) and a 1.22 mmHg decrease in CPP (P < 0.001). When administration of Nimodipine was associated with MAP decreases, P(bt)O(2) (1.03 mmHg; P < 0.001) and CBF (0.39 ml/100 g/min; P = 0.002) also decreased.

CONCLUSIONS

Despite CPP targeted therapy with vasopressor medication, oral Nimodipine was associated with a decrease in MAP and CPP. When Nimodipine administration was associated with a decrease in MAP, there were concomitant drops in P(bt)O(2) and CBF. These findings suggest that MAP support after oral Nimodipine may be important to maintain adequate CBF in patients with poor-grade subarachnoid hemorrhage.