Cerebral response to norepinephrine compared with fluid resuscitation in ovine traumatic brain injury and systemic inflammation

Improving Understanding and Outcomes of Traumatic Brain Injury Using Bidirectional Translational Research

Recent clinical trials in traumatic brain injury (TBI) have failed to demonstrate therapeutic effects even when there appears to be good evidence for efficacy in one or more appropriate pre-clinical models. While existing animal models mimic the injury, difficulties in translating promising therapeutics are exacerbated by the lack of alignment of discrete measures of the underlying injury pathology between the animal models and human subjects. To address this mismatch, we have incorporated reverse translation of bedside experience to inform pre-clinical studies in a large animal (pig) model of TBI that mirror practical clinical assessments. Cerebral autoregulation is impaired after TBI, contributing to poor outcome. Cerebral perfusion pressure (CPP) is often normalized by use of vasoactive agents to increase mean arterial pressure (MAP) and thereby limit impairment of cerebral autoregulation and neurological deficits. Vasoactive agents clinically used to elevate MAP to increase CPP after TBI, such as phenylephrine (Phe), dopamine (DA), norepinephrine (NE), and epinephrine (EPI), however, have not been compared sufficiently regarding effect on CPP, autoregulation, and survival after TBI, and clinically, current vasoactive agent use is variable. The cerebral effects of these clinically commonly used vasoactive agents are not known. This review will emphasize pediatric work and will describe bidirectional translational studies using a more human-like animal model of TBI to identify better therapeutic strategies to improve outcome post-injury. These studies in addition investigated the mechanism(s) involved in improvement of outcome in the setting of TBI.

Pre-hospital rescue times and actions in severe trauma. A comparison between two trauma systems: Germany and the Netherlands

INTRODUCTION

The aim of this study was to compare the effect of national pre-hospital rescue strategies on the status of severely injured patients at the time of admission to a Trauma Center (TC) in Germany or the Netherlands.

PATIENTS AND METHODS

This retrospective database analysis based on the TraumaRegister DGU(®) (TR-DGU) of the German Trauma Society compares the pre-hospital trauma system of Germany with three Trauma Centers (TCs) from the Netherlands. It comprises trauma patients from 2009 to 2012 admitted to a Level I TC, all patients aged 16-80 years primarily admitted with an ISS ≥ 16 and data available for mode of transport, pre-hospital measures and total pre-hospital time. Additionally three subgroups were formed by mode of transportation and involved personnel: Ambulance/Physician, Helicopter/Physician, Ambulance/EMT. Primary endpoint is the patient's status at the time of admission to the trauma room. Secondary endpoint is hospital mortality.

RESULTS

A total of 12,168 patients met the inclusion criteria. Major differences in the injury patterns, pre-hospital rescue time, transport strategy and actions are documented. The mean ISS in the German overall group was 28.6 ± 12.2 compared to 27.4 ± 12.8 in the Dutch overall group. In the subgroups the highest injury severity with 29.8 ± 12.7 for German patients and 31.0 ± 14.6 for Dutch patients was found in the Helicopter/Physician subgroups and the lowest in patients transported by ambulance under emergency medical technician (EMT) care i.e. 24.2 ± 8.9 for German patients and 23.6 ± 10.3 for Dutch patients. The mean total pre-hospital time for patients admitted to Dutch TCs of 53.8 ± 28.7 min was 15.1 min shorter than for patients transported to German TCs 68.7 ± 28.6 min. The overall mean pre-hospital volume replacement of 1103 ± 821 ml for German patients was about twice as high as for Dutch patients (541 ± 700 ml). In physician led subgroups in the Netherlands higher rates of intubation, catecholamine administration and chest tubes are recorded. The basic vital signs from on-scene to hospital admission did not show relevant changes. Additional parameters available in the trauma room revealed a lower mean Base Excess (BE) for Dutch patients and a diminished mean prothrombin ratio for German patients. No reliable evidence was found that differences in the mortality analysis resulted from different national pre-hospital strategy.

CONCLUSIONS

Many differences in the national pre-hospital strategy were demonstrated but the effect on patient's status at the time of admission to trauma room remains unclear. A follow-up study, which mitigates the now known injury patterns has to be initiated to further substantiate the findings of this study.

Vasopressor use and effect on blood pressure after severe adult traumatic brain injury

BACKGROUND

We describe institutional vasopressor usage, and examine the effect of vasopressors on hemodynamics: heart rate (HR), mean arterial blood pressure (MAP), intracranial pressure (ICP), cerebral perfusion pressure (CPP), brain tissue oxygenation (PbtO(2)), and jugular venous oximetry (SjVO(2)) in adults with severe traumatic brain injury (TBI).

METHODS

We performed a retrospective analysis of 114 severely head injured patients who were admitted to the neurocritical care unit of Level 1 trauma center and who received vasopressors (phenylephrine, norepinephrine, dopamine, vasopressin or epinephrine) to increase blood pressure

RESULTS

Phenylephrine was the most commonly used vasopressor (43%), followed by norepinephrine (30%), dopamine (22%), and vasopressin (5%). Adjusted for age, gender, injury severity score, vasopressor dose, baseline blood pressure, fluid administration, propofol sedation, and hypertonic saline infusion, phenylephrine use was associated with 8 mmHg higher mean arterial pressure (MAP) than dopamine (P = 0.03), and 12 mmHg higher cerebral perfusion pressure (CPP) than norepinephrine (P = 0.02) during the 3 h after vasopressor start. There was no difference in ICP between the drug groups, either at baseline or after vasopressor treatment.

CONCLUSIONS

Most severe TBI patients received phenylephrine. Patients who received phenylephrine had higher MAP and CPP than patients who received dopamine and norepinephrine, respectively.

Medical pre-hospital management reduces mortality in severe blunt trauma: a prospective epidemiological study

INTRODUCTION

Severe blunt trauma is a leading cause of premature death and handicap. However, the benefit for the patient of pre-hospital management by emergency physicians remains controversial because it may delay admission to hospital. This study aimed to compare the impact of medical pre-hospital management performed by SMUR (Service Mobile d'Urgences et de Réanimation) with non-medical pre-hospital management provided by fire brigades (non-SMUR) on 30-day mortality.

METHODS

The FIRST (French Intensive care Recorded in Severe Trauma) study is a multicenter cohort study on consecutive patients with severe blunt trauma requiring admission to university hospital intensive care units within the first 72 hours. Initial clinical status, pre-hospital life-sustaining treatments and Injury Severity Scores (ISS) were recorded. The main endpoint was 30-day mortality.

RESULTS

Among 2,703 patients, 2,513 received medical pre-hospital management from SMUR, and 190 received basic pre-hospital management provided by fire brigades. SMUR patients presented a poorer initial clinical status and higher ISS and were admitted to hospital after a longer delay than non-SMUR patients. The crude 30-day mortality rate was comparable for SMUR and non-SMUR patients (17% and 15% respectively; P = 0.61). After adjustment for initial clinical status and ISS, SMUR care significantly reduced the risk of 30-day mortality (odds ratio (OR): 0.55, 95% CI: 0.32 to 0.94, P = 0.03). Further adjustments for the delay to hospital admission only marginally affected these results.

CONCLUSIONS

This study suggests that SMUR management is associated with a significant reduction in 30-day mortality. The role of careful medical assessment and intensive pre-hospital life-sustaining treatments needs to be assessed in further studies.

Role of vasopressor administration in patients with acute neurologic injury

INTRODUCTION

Pharmacologic blood pressure elevation is often utilized to prevent or treat ischemia in patients with acute neurologic injury, and routinely requires administration of vasopressor agents. Depending on the indication, vasopressor agents may be administered to treat hypotension or to induce hypertension.

METHODS

Although numerous guideline statements exist regarding the management of blood pressure in these patients, most recommendations are based largely on Class III evidence. Further, there are few randomized controlled trials comparing vasopressor agents in these patients and selection is often guided by expert consensus.

RESULTS

We discuss the clinical evidence regarding vasopressor administration for blood pressure management in patients with acute neurologic injury. The effect of various vasopressors on cerebral hemodynamics is also discussed.

CONCLUSION

Although high-quality clinical data are scarce, the available evidence suggests that norepinephrine should be considered as the vasopressor of choice when blood pressure elevation is indicated in patients with acute neurologic injury.

Aging and animal models of systemic insult: trauma, burn, and sepsis

In the acute-care setting, it is widely accepted that elderly patients have increased morbidity and mortality compared with young healthy patients. The reasons for this, however, are largely unknown. Although animal modeling has helped improve treatment strategies for young patients, there are a scarce number of studies attempting to understand the mechanisms of systemic insults such as trauma, burn, and sepsis in aged individuals. This review aims to highlight the relevance of using animals to study the pathogenesis of these insults in the aged and, despite the deficiency of information, to summarize what is currently known in this field.

Impact of norepinephrine and fluid on cerebral oxygenation in experimental hemorrhagic shock

Few data exist regarding resuscitation of hypovolemic shock in infants, and alternative strategies such as vasopressor therapy merit further evaluation. However, the effects of norepinephrine on cerebral perfusion and oxygenation during hemorrhagic shock in the pediatric population are still unclear. Eight anesthetized piglets were subjected to hypotension by blood withdrawal of 25 mL/kg. Norepinephrine was titrated to achieve baseline mean arterial blood pressure (MAP), and cerebral oxygenation was determined by brain tissue Po2 (Ptio2) and near-infrared spectroscopy-derived tissue oxygen index (TOI). Then, norepinephrine was stopped, MAP was allowed to decrease again below 30 mm Hg, and shed blood was retransfused. During hemorrhage, TOI dropped from 69+/-3 to 59+/-3%, and Ptio2 from 29+/-6 to 13+/-1 mm Hg (mean+/-SEM; p<0.001). Following norepinephrine, cerebral perfusion pressure (CPP) could be restored immediately, whereas TOI and Ptio2 did not increase significantly. In contrast, following retransfusion, TOI and Ptio2 increased to 68+/-3% and 27+/-7 mm Hg reaching baseline values, respectively. In conclusion, while norepinephrine increased CPP immediately, cerebral oxygenation as reflected by TOI and Ptio2 could not be improved by norepinephrine, but only by retransfusion.