Intracranial pressure and cerebral perfusion pressure in patients developing brain death

The Role of Systemic Inflammation in the Pathogenesis of Spontaneous Intracranial Hemorrhage in the Presence or Absence of Effective Cerebral Blood Flow

Background: Spontaneous intracerebral hemorrhage (ICH) is one of the leading causes of mortality in intensive care units. The role of systemic hyperintense inflammation (SHI) in the pathogenesis of critical complications of ICH remains a poorly understood problem. There is a specific variant of severe ICH associated with increased intracranial pressure and occlusion of intracranial vessels, defined as ineffective cerebral blood flow (IECBF). Methods: To evaluate the role of SHI in the pathogenesis of severe (comatose) ICH in a dynamic comparison of patients with IECBF (n-26) and without IECBF (n-52). The SHI integral score criterion (SI scale) was used, including certain values of plasma concentrations of IL-6, IL-8, IL-10; TNF-α, PCT, cortisol, myoglobin, troponin I, D-dimer, and, additionally, SOFA scale values. Blood levels of ACTH and neuron-specific enolase (NSE) were also assessed. Results: Twenty-eight-day mortality in severe ICH reached 84.6% (without IECBF) and 96.2% (with IECBF). Clear signs of SHI were detected in 61.5%/87.8% (without IECBF) and 0.0%/8.7% (with IECBF) within 1-3/5-8 days from the onset of ICH manifestation. The lower probability of developing SHI in the IECBF group was associated with low blood NSE concentrations. Conclusions: The development of SHI in ICH is pathogenetically related to the permeability of the blood-brain barrier for tissue breakdown products and other neuroinflammatory factors.

A ten-year retrospective analysis of decompressive craniectomy or craniotomy after severe brain injury and its implications for donation after brain death

Craniotomy or decompressive craniectomy are among the therapeutic options to prevent or treat secondary damage after severe brain injury. The choice of procedure depends, among other things, on the type and severity of the initial injury. It remains controversial whether both procedures influence the neurological outcome differently. Thus, estimating the risk of brain herniation and death and consequently potential organ donation remains difficult. All patients at the University Hospital Münster for whom an isolated craniotomy or decompressive craniectomy was performed as a treatment after severe brain injury between 2013 and 2022 were retrospectively included. Proportion of survivors and deceased were evaluated. Deceased were further analyzed regarding anticoagulants, comorbidities, type of brain injury, potential and utilized donation after brain death. 595 patients were identified, 296 patients survived, and 299 deceased. Proportion of decompressive craniectomy was higher than craniotomy in survivors (89% vs. 11%, p < 0.001). Brain death was diagnosed in 12 deceased and 10 donations were utilized. Utilized donations were comparable after both procedures (5% vs. 2%, p = 0.194). Preserved brain stem reflexes as a reason against donation did not differ between decompressive craniectomy or craniotomy (32% vs. 29%, p = 0.470). Patients with severe brain injury were more likely to survive after decompressive craniectomy than craniotomy. Among the deceased, potential and utilized donations did not differ between both procedures. This suggests that brain death can occur independent of the previous neurosurgical procedure and that organ donation should always be considered in end-of-life decisions for patients with a fatal prognosis.

Confirmatory digital subtraction angiography after clinical brain death/death by neurological criteria: impact on number of donors and organ transplants

Background

Demand for organs exceeds the number of transplants available, underscoring the need to optimize organ donation procedures. However, protocols for determining brain death (BD)/death by neurological criteria (DNC) vary considerably worldwide. In Denmark, digital subtraction angiography (DSA) is the only legally approved confirmatory test for diagnosing BD/DNC. We investigated the effect of the time delay caused by (repeat) confirmatory DSA on the number of organs donated by patients meeting clinical criteria for BD/DNC. We hypothesized that, first, patients investigated with ≥2 DSAs donate fewer organs than those investigated with a single DSA; second, radiological interpretation of DSA is subject to interrater variability; and third, residual intracranial circulation is inversely correlated with inotropic blood pressure support.

Methods

All DSAs performed over a 7-year period as part of BD/DNC protocols at Rigshospitalet, Copenhagen University Hospital, Denmark, were included. Clinical data were extracted from electronic health records. DSAs were reinterpreted by an independent neurinterventionist blinded to the original radiological reports.

Results

We identified 130 DSAs in 100 eligible patients. Patients with ≥2 DSAs (n = 20) donated fewer organs (1.7 +/- 1.6 SD) than patients undergoing a single DSA (n = 80, 2.6 +/- 1.7 organs, p = 0.03), and they became less often donors (n = 12, 60%) than patients with just 1 DSA (n = 65, 81.3%; p = 0.04). Interrater agreement of radiological DSA interpretation was 88.5% (Cohen's kappa = 0.76). Patients with self-maintained blood pressure had more often residual intracranial circulation (n = 13/26, 50%) than patients requiring inotropic support (n = 14/74, 18.9%; OR = 0.23, 95% CI [0.09-0.61]; p = 0.002).

Discussion

In potential donors who fulfill clinical BD/DNC criteria, delays caused by repetition of confirmatory DSA result in lost donors and organ transplants. Self-maintained blood pressure at the time of clinical BD/DNC increases the odds for residual intracranial circulation, creating diagnostic uncertainty because radiological DSA interpretation is not uniform. We suggest that avoiding unnecessary repetition of confirmatory investigations like DSA may result in more organs donated.

“A Comparative Analysis of the Number of Organ Retrievals in Relation to Potential Donation Qualifications in Populations of Patients From a Single Anesthesiology and Intensive Care Unit in 2017-2018”

The population of patients declared as brain dead and qualified for organ donation is relatively low in Poland. The main causes of brain death include cerebral vascular diseases and brain trauma (54 and 34%, respectively, according to Poltransplant registry data). The number of organ procurements in Poland is constantly recorded on average at 14 donations per 1 million citizens (14/mln) in 2017 and 12 donations per one million in 2018. It is difficult to precisely define the number of patients who meet the criteria for brain death certification. The authors have retrospectively analyzed the medical data of 229 patients from 2017 and 2018 records with the aim of identifying potential organ donors among patients of the Intensive Care Unit (ICU) in the University Hospital in Western Poland. Brain death was suspected in 53 patients (23.14%). Brain imaging to confirm no cerebral flow (which is consistent with brain death) was performed in 17 patients (7.45%) and this, as a result, led to organ donation in 9 cases (3.93%). The factors identified as having a positive influence on organ donation included: daily thorough physical examination, (Glasgow Coma Scale) GCS assessment, depth and duration of sedation, ICU length of stay and early performance of a CT-angiogram.

Loss of cerebral blood flow and cerebral perfusion pressure in brain death: A transcranial Duplex ultrasonography study

PURPOSE

We investigated cerebral perfusion pressure (CPP) at the time loss of cerebral blood flow (CBF) occurred during brain death (BD). We hypothesized that a critical closing pressure (CrCP) may be reached before CPP drops to 0 mmHg.

MATERIALS AND METHODS

14 patients with increasing intracranial pressure (ICP) leading to BD were included. Transcranial Duplex (TCD) ultrasonography was used to investigate CBF. Starting at a CPP of 30 mmHg, TCD was repeated until waveforms indicated loss of CBF. We then analyzed CPP by the time TCD indicated absent CBF and clinical BD was established.

RESULTS

In 12 patients, CPP was positive when clinical BD was manifest and TCD illustrated absent CBF. Across all patients, mean CPP at clinical BD manifestation was 10.0 mmHg (range 0-20 mmHg); mean CPP by the time CBF stopped was 7.5 mmHg (0-20 mmHg). In four patients, clinical BD preceded loss of CBF. Here, the mean CPP difference from clinical BD to loss of CBF was 8.8 mmHg (5-15 mmHg).

CONCLUSIONS

CrCP may be reached although CPP is still positive, resulting in complete loss of CBF and BD. By including bedside TCD, neuromonitoring may contribute to early identification of patients at risk to experience loss of CBF and subsequent BD.

Autonomic Nervous System Activity during Refractory Rise in Intracranial Pressure

Refractory intracranial hypertension (RIH) is a dramatic increase in intracranial pressure (ICP) that cannot be controlled by treatment. Recent reports suggest that the autonomic nervous system (ANS) activity may be altered during changes in ICP. Our study aimed to assess ANS activity during RIH and the causal relationship between rising in ICP and autonomic activity. We reviewed retrospectively 24 multicenter (Cambridge, Tromso, Berlin) patients in whom RIH developed as a pre-terminal event after acute brain injury (ABI). They were monitored with ICP, arterial blood pressure (ABP), and electrocardiography (ECG) using ICM+ software. Parameters reflecting autonomic activity were computed in time and frequency domain through the measurement of heart rate variability (HRV) and baroreflex sensitivity (BRS). Our results demonstrated that a rise in ICP was associated to a significant rise in HRV and BRS with a higher significance level in the high-frequency HRV (p < 0.001). This increase was followed by a significant decrease in HRV and BRS above the upper-breakpoint of ICP where ICP pulse-amplitude starts to decrease whereas the mean ICP continues to rise. Temporality measured with a Granger test suggests a causal relationship from ICP to ANS. The above results suggest that a rise in ICP interacts with ANS activity, mainly interfacing with the parasympathetic-system. The ANS seems to react to the rise in ICP with a response possibly focused on maintaining the cerebrovascular homeostasis. This happens until the critical threshold of ICP is reached above which the ANS variables collapse, probably because of low perfusion of the brain and the central autonomic network.

Methodological Consideration on Monitoring Refractory Intracranial Hypertension and Autonomic Nervous System Activity

Refractory intracranial hypertension (RIH) refers to a dramatic increase in intracranial pressure (ICP) that cannot be controlled by treatment and leads to patient death. Detrimental sequelae of raised ICP in acute brain injury (ABI) are unclear because the underlying physiopathological mechanisms of raised ICP have not been sufficiently investigated. Recent reports have shown that autonomic activity is altered during changes in ICP. The aim of our study was to evaluate the feasibility of assessing autonomic activity during RIH with our adopted methodology. We selected 24 ABI patients for retrospective review who developed RIH. They were monitored based on ICP, arterial blood pressure, and electrocardiogram using ICM+ software. Secondary parameters reflecting autonomic activity were computed in time and frequency domains through the continuous measurement of heart rate variability and baroreflex sensitivity. The results of the analysis will be presented later in a full paper. This preliminary analysis shows the feasibility of the adopted methodology.

Loss of Potential Donors Due to Hemodynamic Maintenance

BACKGROUND

Statistics indicate low utilization of potential donors, where only about one-third are converted into actual donors. In this context, it is plausible to argue that many potential donors are not hemodynamically stable for harvesting multiple organs since the procedures for maintaining parameters of stability may not be a priority in all critical care units in the country. Thus, it is necessary to identify losses of potential donors due to hemodynamic maintenance since reversing this situation enable minimizing mortality on waiting lists.

METHODS

This was a retrospective quantitative study, based on information sent to Notification, Organ Procurement, and Distribution Centers by reporting hospitals in the state of São Paulo, using the Death Information Form regarding the specifics of each death registered in their intensive care units and emergency rooms.

RESULTS

Hemodynamic instability contributed to a loss of 537 potential donors, corresponding to 61.9% of failures to obtain potentially transplantable organs.

CONCLUSION

Of the 33,175 cases of death reported, 867 fulfilled the criteria to be possible and potential donors (ie, patients diagnosed with brain death). Among these cases, 38.1% fulfilled Criterion 3 (ie, they were hemodynamically stable and in ideal organ donation condition). Therefore, this study concludes that losses due to maintenance occurred in 537 brain dead patients. This finding highlights the importance of investing in the development of competencies of professionals who work in critical care units to increase the number of multiple organ and tissue donors and reduce waiting lists.

Physiological Signatures of Brain Death Uncovered by Intracranial Multimodal Neuromonitoring

BACKGROUND

The physiological and neurochemical changes that accompany brain death are not well described.

MATERIALS AND METHODS

A retrospective observational study of patients with acute brain injury who underwent intracranial multimodality neuromonitoring between October 2015 and June 2018. Patients were included for analysis either if brain death was diagnosed or refractory intracranial hypertension with persistent equalization of intracranial pressure (ICP) and mean arterial pressure (MAP) developed.

RESULTS

Of 114 patients who underwent invasive neuromonitoring, 11 cases with MAP/ICP equalization were identified. Of those, 9 were declared brain dead based on accepted national and institutional criteria. An additional 2 cases with MAP/ICP equalization who died after withdrawal of life-sustaining therapies were identified. Of the 11 identified patients, 10 had continuous monitoring data available for analysis. Cerebral microdialysis data were available for 4 patients.In the 10 cases with available continuous data, ICP/MAP equalization was associated with marked reduction of cerebral blood flow and brain tissue oxygen tension to near zero levels as well as a significant decrease in brain temperature compared with body temperature. In the 4 patients with microdialysis monitoring, ICP/MAP equalization resulted in a near complete depletion of cerebral glucose and pyruvate, as well as a marked rise in cerebral glycerol. Finally, ICP/MAP equalization was accompanied by complete loss of cerebrovascular pressure reactivity, decrease in intracranial pulse pressure, and a paradoxical improvement of ICP waveform morphology.

CONCLUSIONS

A characteristic set of changes in cerebrovascular physiology and neurochemistry occurs during brain death. These changes can be identified by intracranial neuromonitoring.

Impact of decompressive craniectomy on brain perfusion scintigraphy as an ancillary test for brain death diagnosis

OBJECTIVES

Decompressive craniectomy is occasionally performed for patients with impending brain death, which is intended to relieve critically elevated intracranial pressure to keep effective intracranial perfusion. It has been in debate if this surgery later affects the result of brain perfusion scintigraphy performed as an ancillary test in the course of brain death diagnosis because rigid closed skull is deemed essential to elevate intracranial pressure to the point of total absence of intracranial radiotracer uptake on scintigraphy. The purpose of this study is to elucidate the impact of decompressive craniectomy on the result of brain perfusion scintigraphy in patients with suspected brain death.

METHODS

This retrospective cross-sectional study included consecutive 151 brain perfusion scintigraphy performed in 138 patients with suspected brain death from various causes (male 82 patients, female 56 patients; range 0-74 years; mean age 36.6 years). All exams were indicated due to inconclusive clinical diagnosis of brain death. The scintigraphy protocol consists of immediate flow phase and delayed parenchymal phase planar imaging. Additional SPECT imaging was performed in 15 studies in 14 patients. The results, positive or negative brain flow, were compared between patients with and without decompressive craniectomy using Chi-squared test. As there were patients with repeat studies, analysis was performed for both initial and final exam results. Same dataset was used for initial and final exams in patients with only one exam.

RESULTS

Out of 138 patients, 15 patients underwent decompressive craniectomy (11%) and 123 patients were managed medically (89%). On the initial exam, negative brain flow was demonstrated in 11 of 15 patients with craniectomy (73.3%) and 106 of 123 patients without craniectomy (86.2%). On the final exam, negative brain flow was demonstrated 12 of 15 patients with craniectomy (80%) and 111 of 123 patients without craniectomy (90.2%). There were no statistically significant differences between the two groups on both initial and final exams (p = 0.19 and 0.23, respectively).

CONCLUSION

In patients with suspected brain death, history of decompressive craniectomy does not affect the result of brain perfusion scintigraphy.

Progress of intracranial pressure and cerebral perfusion pressure in patients during the development of brain death

BACKGROUND

Clinical investigations of brain death are supposed to prove absence of cerebral perfusion. However, only limited data are available documenting intracranial pressure (ICP) and cerebral perfusion pressure (CPP) during the development of brain death. Our study presents additional data to understand the course of ICP and CPP in patients developing brain death.

MATERIAL AND METHODS

We analyzed retrospective data of 18 patients with ICP monitoring during the development of brain death due to primary brain lesions. ICP and CPP values were continuously measured between two clinically defined time points: 1. non-reactive and widened pupils, 2. brain death determination. We analyzed ICP and CPP at the above-mentioned end points. Additionally, we investigated maximum ICP and minimal CPP values between these time points.

RESULTS

Patients developed fixed and dilated pupils with a median of 38 h before brain death determination. During brain death determination median ICP and median CPP were 103.5 and -2.5 mmHg, respectively. Maximum ICP before brain death determination was significantly higher and minimal CPP values were significantly lower compared to the time point of brain death. During the investigation period all patients experienced ICP values >95 mmHg and CPP < 10 mmHg. All but one patient had documented CPP values of ≤0 mmHg. This single patient had a minimum CPP of 8 mmHg with a maximum ICP of 145 mmHg.

CONCLUSION

Cerebral perfusion pressure during brain death determination may be positive in some patients. Our results showed variable values of ICP and CPP. However, extremely elevated ICP values before or during brain death in combination with low CPP values suggest absence of cerebral perfusion. The occurrence of positive CPP values during brain death determination therefore depends on the time point at which brain death determination is performed.

Neuroscience and Brain Death Controversies: The Elephant in the Room

The conception and the determination of brain death continue to raise scientific, legal, philosophical, and religious controversies. While both the President's Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research in 1981 and the President's Council on Bioethics in 2008 committed to a biological definition of death as the basis for the whole-brain death criteria, contemporary neuroscientific findings augment the concerns about the validity of this biological definition. Neuroscientific evidentiary findings, however, have not yet permeated discussions about brain death. These findings have critical relevance (scientifically, medically, legally, morally, and religiously) because they indicate that some core assumptions about brain death are demonstrably incorrect, while others lack sufficient evidential support. If behavioral unresponsiveness does not equate to unconsciousness, then the philosophical underpinning of the definition based on loss of capacity for consciousness as well as the criteria, and tests in brain death determination are incongruent with empirical evidence. Thus, the primary claim that brain death equates to biological death has then been de facto falsified. This conclusion has profound philosophical, religious, and legal implications that should compel respective authorities to (1) reassess the philosophical rationale for the definition of death, (2) initiate a critical reappraisal of the presumed alignment of brain death with the theological definition of death in Abrahamic faith traditions, and (3) enact new legislation ratifying religious exemption to death determination by neurologic criteria.

Brain death after decompressive craniectomy: Incidence and pathophysiological mechanisms

PURPOSE

Patients who received decompressive craniectomy (DC) are usually not regarded to qualify for brain death (BD) as intracranial pressure (ICP) is not assumed to reach levels critical enough to cause cerebral perfusion failure. Here we investigated the incidence of BD after DC and analyzed the pathophysiological mechanisms.

MATERIALS AND METHODS

We searched our chart records of patients with DC for individuals who developed BD (2010-2016). We then analyzed the course of ICP and cerebral perfusion pressure (CPP) prior to BD and results from radiological tests that aim at demonstrating loss of cerebral perfusion in BD.

RESULTS

BD was diagnosed in 12 of 164 (incidence 7.3%) patients (age=16-70years; male=7; mean longitudinal diameter: 136.2mm). Mean latency between DC and BD was 69.4h. Immediately after DC, mean ICP was 30.0mmHg (standard deviation±24.7mmHg), CPP was 56.8mmHg (±28.1). In the course to BD, ICP increased to 95.8mmHg (±16.1), CPP decreased to -9.9mmHg (±11.2). In patients in whom radiological methods were performed (n=5) loss of cerebral perfusion was demonstrated.

CONCLUSIONS

Our study evidences that DC does not exclude BD. Even after DC, BD is preceded by a severely reduced CPP, supporting loss of cerebral perfusion as a critical step in BD pathophysiology.