Intrahospital Transfer of Patients with Traumatic Brain Injury: Increase in Intracranial Pressure

Brain metabolism response to intrahospital transfers in neurocritical ill patients and the impact of microdialysis probe location

Intrahospital transfer (IHT), a routine in the management of neurocritical patients requiring imaging or interventions, might affect brain metabolism. Studies about IHT effects using microdialysis (MD) have produced conflicting results. In these studies, only the most damaged hemisphere was monitored, and those may not reflect the impact of IHT on overall brain metabolism, nor do they address differences between the hemispheres. Herein we aimed to quantify the effect of IHT on brain metabolism by monitoring both hemispheres with bilateral MD. In this study, 27 patients with severe brain injury (10 traumatic brain injury and 17 subarachnoid hemorrhage patients) were included, with a total of 67 IHT. Glucose, glycerol, pyruvate and lactate were measured by MD in both hemispheres for 10 h pre- and post-IHT. Alterations in metabolite levels after IHT were observed on both hemispheres; although these changes were more marked in hemisphere A (most damaged) than B (less damaged). Our results suggest that brain metabolism is altered after an IHT of neurocritical ill patients particularly but not limited to the damaged hemisphere. Bilateral monitorization may be more sensitive than unilateral monitorization for detecting metabolic disturbances not directly related to the course of the disease.

Intrahospital Transport of Critically Ill Patients with Subarachnoid Hemorrhage-Frequency, Timing, Complications, and Clinical Consequences

BACKGROUND

Patients with subarachnoid hemorrhage (SAH) often necessitate intra-hospital transport (IHT) during intensive care treatment. These transfers to facilities outside of the neurointensive care unit (NICU) pose challenges due to the inherent instability of the hemodynamic, respiratory, and neurological parameters that are typical in these patients.

METHODS

In this retrospective, single-center cohort study, a total of 108 IHTs were analyzed for demographics, transport rationale, clinical outcomes, and pre/post-IHT monitoring parameters. After establishing clinical thresholds, the frequency of complications was calculated, and predictors of thresholds violations were determined.

RESULTS

The mean age was 55.7 (+/-15.3) years, with 68.0% showing severe SAH (World Federation of Neurosurgical Societies Scale 5). IHTs with an emergency indication made up 30.8% of all transports. Direct therapeutic consequences from IHT were observed in 38.5%. On average, the first IHT occurred 1.5 (+/-2.0) days post-admission and patients were transported 4.3 (+/-1.8) times during their stay in the NICU. Significant parameter changes from pre- to post-IHT included mean arterial pressure, systolic blood pressure, oxygen saturation, blood glucose levels, temperature, dosages of propofol and ketamine, tidal volume, inspired oxygen concentration, Horovitz index, glucose, pH, intracranial pressure, and cerebral perfusion pressure. Relevant hemodynamic thresholds were violated in 31.5% of cases, while respiratory complications occurred in 63.9%, and neurological complications in 20.4%. For hemodynamic complications, a low heart rate with a threshold of 61/min (OR 0.96, 95% CI 0.93-0.99, p = 0.0165) and low doses of midazolam with a threshold of 17.5 mg/h (OR 0.97, 95% CI 0.95-1.00, p = 0.0232) significantly predicted adverse events. However, the model did not identify significant predictors for respiratory and neurological outcomes.

CONCLUSIONS

Conclusively, IHTs in SAH patients are associated with relevant changes in hemodynamic, respiratory, and neurological monitoring parameters, with direct therapeutic consequences in 4/10 IHTs. These findings underscore the importance of further studies on the clinical impact of IHTs.

Co2 Rebreathing Observed While Using a Bag-Mask Resuscitator With Integrated Manometer: A Case Report

Bag-mask resuscitators with integrated manometry help reduce the risk of pulmonary injury during manual ventilation. All such devices must function as intended while preventing carbon dioxide rebreathing, as unintended hypercapnia can be harmful in critically ill patients. We describe a case of carbon dioxide rebreathing in a patient suspected of having a brain injury after blunt trauma who was manually ventilated with a widely available bag-mask resuscitator with integrated manometry after emergent intubation. This case highlights the importance of vigilant monitoring of end-tidal carbon dioxide and appropriate troubleshooting and investigation of unexplained findings to mitigate and prevent adverse patient outcomes.

A bioimpedance-based monitor for real-time detection and identification of secondary brain injury

Secondary brain injury impacts patient prognosis and can lead to long-term morbidity and mortality in cases of trauma. Continuous monitoring of secondary injury in acute clinical settings is primarily limited to intracranial pressure (ICP); however, ICP is unable to identify essential underlying etiologies of injury needed to guide treatment (e.g. immediate surgical intervention vs medical management). Here we show that a novel intracranial bioimpedance monitor (BIM) can detect onset of secondary injury, differentiate focal (e.g. hemorrhage) from global (e.g. edema) events, identify underlying etiology and provide localization of an intracranial mass effect. We found in an in vivo porcine model that the BIM detected changes in intracranial volume down to 0.38 mL, differentiated high impedance (e.g. ischemic) from low impedance (e.g. hemorrhagic) injuries (p < 0.001), separated focal from global events (p < 0.001) and provided coarse 'imaging' through localization of the mass effect. This work presents for the first time the full design, development, characterization and successful implementation of an intracranial bioimpedance monitor. This BIM technology could be further translated to clinical pathologies including but not limited to traumatic brain injury, intracerebral hemorrhage, stroke, hydrocephalus and post-surgical monitoring.

Intracranial pressure monitoring following traumatic brain injury: evaluation of indications, complications, and significance of follow-up imaging-an exploratory, retrospective study of consecutive patients at a level I trauma center

Background

Measurement of intracranial pressure (ICP) is an essential part of clinical management of severe traumatic brain injury (TBI). However, clinical utility and impact on clinical outcome of ICP monitoring remain controversial. Follow-up imaging using cranial computed tomography (CCT) is commonly performed in these patients. This retrospective cohort study reports on complication rates of ICP measurement in severe TBI patients, as well as on findings and clinical consequences of follow-up CCT.

Methods

We performed a retrospective clinical chart review of severe TBI patients with invasive ICP measurement treated at an urban level I trauma center between January 2007 and September 2017.

Results

Clinical records of 213 patients were analyzed. The mean Glasgow Coma Scale (GCS) on admission was 6 with an intra-hospital mortality of 20.7%. Overall, complications in 12 patients (5.6%) related to the invasive ICP-measurement were recorded of which 5 necessitated surgical intervention. Follow-up CCT scans were performed in 192 patients (89.7%). Indications for follow-up CCTs included routine imaging without clinical deterioration (n = 137, 64.3%), and increased ICP values and/or clinical deterioration (n = 55, 25.8%). Follow-up imaging based on clinical deterioration and increased ICP values were associated with significantly increased likelihoods of worsening of CCT findings compared to routinely performed CCT scans with an odds ratio of 5.524 (95% CI 1.625–18.773) and 6.977 (95% CI 3.262–14.926), respectively. Readings of follow-up CCT imaging resulted in subsequent surgical intervention in six patients (3.1%).

Conclusions

Invasive ICP-monitoring in severe TBI patients was safe in our study population with an acceptable complication rate. We found a high number of follow-up CCT. Our results indicate that CCT imaging in patients with invasive ICP monitoring should only be considered in patients with elevated ICP values and/or clinical deterioration.

The Impact of Intrahospital Transports on Brain Tissue Metabolism in Patients with Acute Brain Injury

BACKGROUND

Patients with severe acute brain injury (ABI) often require intrahospital transports (IHTs) for repeated computed tomography (CT) scans. IHTs are associated with serious adverse events (AE) that might pose a risk for secondary brain injury. The goal of this study was to assess IHT-related alterations of cerebral metabolism in ABI patients.

METHODS

We included mechanically ventilated patients with ABI who had continuous multimodality neuromonitoring during an 8-h period before and after routine IHT. Intracranial pressure (ICP), cerebral perfusion pressure (CPP), brain tissue oxygenation (PtiO₂) as well as cerebral and subcutaneous microdialysis parameters (lactate, pyruvate, glycerol, and glutamate) were recorded. Values were compared between an 8-h period before (pre-IHT) and after (post-IHT) the IHT.

RESULTS

A total of 23 IHT for head CT scans in 18 patients were analyzed. Traumatic brain injury (n = 7) was the leading cause of ABI, followed by subarachnoid hemorrhage (n = 6) and intracerebral hemorrhage (n = 5). The analyzed microdialysis parameters in the brain tissue as in the subcutaneous tissue did not show significant changes between the pre-IHT and post-IHT period. In addition, we observed no significant increase in ICP or decrease in CPP and PtiO₂ in the 8-h period after IHT.

CONCLUSIONS

While the occurrence of AE during IHT is a known risk factor for ABI patients, our results demonstrate that IHTs do not alter the brain tissue chemistry in a significant manner. This fact may help assess the risk for routine IHT more accurately.

A narrative review of the clinical application of pressure reactiviy indices in the neurocritical care unit

Pressure reactivity indices are used in clinical research as a surrogate marker of the ability of the cerebrovasculature to maintain cerebral autoregulation. The use of pressure reactivity indices in patients with neurological injury represents a potential to move away from population-based physiological targets used in guidelines to individualized physiological targets. The aim of this review is to describe the underlying principles and development of pressure reactivity indices, alongside a critique of how they have been used in clinical research, including their limitations. The primary source literature was identified from a database search of PUBMed and OVID online using the search terms "pressure reactivity index" and "pressure reactivity indices". The evidence base regarding pressure reactivity indices currently remains Level III. Pressure reactivity indices rely on the correlation (-1 to +1) between the arterial blood pressure and intracranial pressure, with negative values indicating intact cerebral autoregulation and positive values indicating dysfunctional cerebral autoregulation. Meaningful data is taken from summary measures and trends. The traumatic brain injury population feature most prominently in the literature. There is limited description of the potential confounding factors that may affect pressure reactivity indices, including physiological parameters and therapeutic interventions. Plotting a pressure reactivity index against a cerebral perfusion pressure can indicate an optimal cerebral perfusion pressure to individualise patient care. There is potential to over interpret optimal cerebral perfusion pressure targets when the values of pressure reactivity indices are close to zero. There is an association between pressure reactivity indices and neurological outcomes, however the use of pressure reactivity indices as a prognostication tool is to be challenged. Average values of cerebral perfusion pressure that are not close to averaged values of optimal cerebral perfusion pressure are also associated with poor outcome. Further research is required to ascertain whether targeting an optimal cerebral perfusion pressure may alter outcome.