A pilot trial comparing cerebral perfusion pressure-targeted therapy to intracranial pressure-targeted therapy in children with severe traumatic brain injury

Non-invasive estimation of cerebral perfusion pressure using transcranial Doppler ultrasonography in children with severe traumatic brain injury

OBJECTIVE

To identify if cerebral perfusion pressure (CPP) can be non-invasively estimated by either of two methods calculated using transcranial Doppler ultrasound (TCD) parameters.

DESIGN

Retrospective review of previously prospectively gathered data.

SETTING

Pediatric intensive care unit in a tertiary care referral hospital.

PATIENTS

Twenty-three children with severe traumatic brain injury (TBI) and invasive intracranial pressure (ICP) monitoring in place.

INTERVENTIONS

TCD evaluation of the middle cerebral arteries was performed daily. CPP at the time of the TCD examination was recorded. For method 1, estimated cerebral perfusion pressure (CPPe) was calculated as: CPPe = MAP × (diastolic flow (Vd)/mean flow (Vm)) + 14. For method 2, critical closing pressure (CrCP) was identified as the intercept point on the x-axis of the linear regression line of blood pressure and flow velocity parameters. CrCP/CPPe was then calculated as MAP-CrCP.

MEASUREMENTS AND MAIN RESULTS

One hundred eight paired measurements were available. Using patient averaged data, correlation between CPP and CPPe was significant (r = 0.78, p = < 0.001). However, on Bland-Altman plots, bias was 3.7 mmHg with 95% limits of agreement of - 17 to + 25 for CPPe. Using patient averaged data, correlation between CPP and CrCP/CPPe was significant (r = 0.59, p = < 0.001), but again bias was high at 11 mmHg with wide 95% limits of agreement of - 15 to + 38 mmHg.

CONCLUSIONS

CPPe and CrCP/CPPe do not have clinical value to estimate the absolute CPP in pediatric patients with TBI.

Children With Severe Traumatic Brain Injury, Intracranial Pressure, Cerebral Perfusion Pressure, What Does it Mean? A Review of the Literature

Severe traumatic brain injury is a leading cause of morbidity and mortality in children. In 2003 the Brain Trauma Foundation released guidelines that have since been updated (2010) and have helped standardize and improve care. One area of care that remains controversial is whether the placement of an intracranial pressure monitor is advantageous in the management of traumatic brain injury. Another aspect of care that is widely debated is whether management after traumatic brain injury should be based on intracranial pressure-directed therapy, cerebral perfusion pressure-directed therapy, or a combination of the two. The aim of this article was to provide an overview and review the current evidence regarding these questions.

Elevation of the head during intensive care management in people with severe traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a major public health problem and a fundamental cause of morbidity and mortality worldwide. The burden of TBI disproportionately affects low- and middle-income countries. Intracranial hypertension is the most frequent cause of death and disability in brain-injured people. Special interventions in the intensive care unit are required to minimise factors contributing to secondary brain injury after trauma. Therapeutic positioning of the head (different degrees of head-of-bed elevation (HBE)) has been proposed as a low cost and simple way of preventing secondary brain injury in these people. The aim of this review is to evaluate the evidence related to the clinical effects of different backrest positions of the head on important clinical outcomes or, if unavailable, relevant surrogate outcomes.

OBJECTIVES

To assess the clinical and physiological effects of HBE during intensive care management in people with severe TBI.

SEARCH METHODS

We searched the following electronic databases from their inception up to March 2017: Cochrane Injuries' Specialised Register, CENTRAL, MEDLINE, Embase, three other databases and two clinical trials registers. The Cochrane Injuries' Information Specialist ran the searches.

SELECTION CRITERIA

We selected all randomised controlled trials (RCTs) involving people with TBI who underwent different HBE or backrest positions. Studies may have had a parallel or cross-over design. We included adults and children over two years of age with severe TBI (Glasgow Coma Scale (GCS) less than 9). We excluded studies performed in children of less than two years of age because of their unfused skulls. We included any therapeutic HBE including supine (flat) or different degrees of head elevation with or without knee gatch or reverse Trendelenburg applied during the acute management of the TBI.

DATA COLLECTION AND ANALYSIS

Two review authors independently checked all titles and abstracts, excluding references that clearly didn't meet all selection criteria, and extracted data from selected studies on to a data extraction form specifically designed for this review. There were no cases of multiple reporting. Each review author independently evaluated risk of bias through assessing sequence generation, allocation concealment, blinding, incomplete outcome data, selective outcome reporting, and other sources of bias.

MAIN RESULTS

We included three small studies with a cross-over design, involving a total of 20 participants (11 adults and 9 children), in this review. Our primary outcome was mortality, and there was one death by the time of follow-up 28 days after hospital admission. The trials did not measure the clinical secondary outcomes of quality of life, GCS, and disability. The included studies provided information only for the secondary outcomes intracranial pressure (ICP), cerebral perfusion pressure (CPP), and adverse effects.We were unable to pool the results as the data were either presented in different formats or no numerical data were provided. We included narrative interpretations of the available data.The overall risk of bias of the studies was unclear due to poor reporting of the methods. There was marked inconsistency across studies for the outcome of ICP and small sample sizes or wide confidence intervals for all outcomes. We therefore rated the quality of the evidence as very low for all outcomes and have not included the results of individual studies here. We do not have enough evidence to draw conclusions about the effect of HBE during intensive care management of people with TBI.

AUTHORS' CONCLUSIONS

The lack of consistency among studies, scarcity of data and the absence of evidence to show a correlation between physiological measurements such as ICP, CCP and clinical outcomes, mean that we are uncertain about the effects of HBE during intensive care management in people with severe TBI.Well-designed and larger trials that measure long-term clinical outcomes are needed to understand how and when different backrest positions can affect the management of severe TBI.

Establishing a Clinically Relevant Large Animal Model Platform for TBI Therapy Development: Using Cyclosporin A as a Case Study

We have developed the first immature large animal translational treatment trial of a pharmacologic intervention for traumatic brain injury (TBI) in children. The preclinical trial design includes multiple doses of the intervention in two different injury types (focal and diffuse) to bracket the range seen in clinical injury and uses two post-TBI delays to drug administration. Cyclosporin A (CsA) was used as a case study in our first implementation of the platform because of its success in multiple preclinical adult rodent TBI models and its current use in children for other indications. Tier 1 of the therapy development platform assessed the short-term treatment efficacy after 24 h of agent administration. Positive responses to treatment were compared with injured controls using an objective effect threshold established prior to the study. Effective CsA doses were identified to study in Tier 2. In the Tier 2 paradigm, agent is administered in a porcine intensive care unit utilizing neurological monitoring and clinically relevant management strategies, and intervention efficacy is defined as improvement in longer term behavioral endpoints above untreated injured animals. In summary, this innovative large animal preclinical study design can be applied to future evaluations of other agents that promote recovery or repair after TBI.

Variations of the blood gas levels and thermodilutional parameters during ICP monitoring after severe head trauma in children

PURPOSE

The purpose of this study was to define, in children following head trauma and GSC ≤ 8, at which level of intracranial pressure (ICP), the thermodilutional, and gas analytic parameters implicated in secondary cerebral insults shows initial changes.

METHODS

We enrolled in the study 56 patients: 30 males and 26 females, mean age 71 ± 52 months. In all children, volumetric hemodynamic and blood gas parameters were monitored following initial resuscitation and every 4 h thereafter or whenever a hemodynamic deterioration was suspected. During the cumulative hospital stay, a total of 1050 sets of measurements were done. All parameters were stratified in seven groups according to ICP (group A1 = 0-5 mmHg, group A2 = 6-10 mmHg, group A3 = 11-15 mmHg, group A4 16-20 mmHg, group A5 21-25 mmHg, group A6 26-30 mmHg, group A7 >31 mmHg).

RESULTS

Mean values of jugular oxygen saturation (SJO2), jugular oxygen partial pressure (PJO2), extravascular lung water (EVLWi), pulmonary vascular permeability (PVPi), fluid overload (FO), and cerebral extraction of oxygen (CEO2) vary significantly from A3 (11-15 mmHg) to A4 (16-20 mmHg). They relate to ICP in a four-parameter sigmoidal function (4PS function with: r(2) = 0.90), inflection point of 15 mmHg of ICP, and a maximum curvature point on the left horizontal asymptote at 13 mmHg of ICP.

CONCLUSIONS

Mean values of SJO2, PJO2, EVLWi, PVPi, FO, and CEO2 become pathologic at 15 mmHg of ICP; however, the curve turns steeper at 13 mmHg, possibly a warning level in children for the development of post head trauma secondary insult.

Age-specific cerebral perfusion pressure thresholds and survival in children and adolescents with severe traumatic brain injury*

OBJECTIVES

Evidence-based traumatic brain injury guidelines support cerebral perfusion pressure thresholds for adults at a class 2 level, but evidence is lacking in younger patients. The purpose of this study is to identify the impact of age-specific cerebral perfusion pressure thresholds on short-term survival among patients with severe traumatic brain injury.

DESIGN

Institutional review board-approved, prospective, observational cohort study.

SETTING

Level I or II trauma centers in New York State.

PATIENTS

Data on all patients with a postresuscitation Glasgow Coma Score less than 9 were added in the Brain Trauma Foundation prospective New York State TBI-trac database.

MEASUREMENTS AND MAIN RESULTS

We calculated the survival rates and relative risks of mortality for patients with severe traumatic brain injury based on predefined age-specific cerebral perfusion pressure thresholds. A higher threshold and a lower threshold were defined for each age group: 60 and 50 mm Hg for 12 years old or older, 50 and 35 mm Hg for 6-11 years, and 40 and 30 mm Hg for 0-5 years. Patients were stratified into age groups of 0-11, 12-17, and 18 years old or older. Three exclusive groups of CPP-L (events below low cerebral perfusion pressure threshold), CPP-B (events between high and low cerebral perfusion pressure thresholds), and CPP-H (events above high cerebral perfusion pressure threshold) were defined. As an internal control, we evaluated the associations between cerebral perfusion pressure events and events of hypotension and elevated intracranial pressure. Survival was significantly higher in 0-11 and 18 years old or older age groups for patients with CPP-H events compared with those with CPP-L events. There was a significant decrease in survival with prolonged exposure to CPP-B events for the 0-11 and 18 years old and older age groups when compared with the patients with CPP-H events (p = 0.0001 and p = 0.042, respectively). There was also a significant decrease in survival with prolonged exposure to CPP-L events in all age groups compared with the patients with CPP-H events (p< 0.0001 for 0- to 11-yr olds, p = 0.0240 for 12- to 17-yr olds, and p < 0.0001 for 18-yr old and older age groups). The 12- to 17-year olds had a significantly higher likelihood of survival compared with adults with prolonged exposure to CPP-L events (< 50 mm Hg). CPP-L events were significantly related to systemic hypotension for the 12- to 17-year-old group (p = 0.004) and the 18-year-old and older group (p < 0.0001). CPP-B events were significantly related to systemic hypotension in the 0- to 11-year-old group (p = 0.014). CPP-B and CPP-L events were significantly related to elevated intracranial pressure in all age groups.

CONCLUSIONS

Our data provide new evidence that cerebral perfusion pressure targets should be age specific. Furthermore, cerebral perfusion pressure goals above 50 or 60 mm Hg in adults, above 50 mm Hg in 6- to 17-year olds, and above 40 mm Hg in 0- to 5-year olds seem to be appropriate targets for treatment-based studies. Systemic hypotension had an inconsistent relationship to events of low cerebral perfusion pressure, whereas elevated intracranial pressure was significantly related to all low cerebral perfusion pressure events across all age groups. This may impart a clinically important difference in care, highlighting the necessity of controlling intracranial pressure at all times, while targeting systolic blood pressure in specific instances.

Cyclosporin A preserves mitochondrial function after traumatic brain injury in the immature rat and piglet

Cyclosporin A (CsA) has been shown to be neuroprotective in mature animal models of traumatic brain injury (TBI), but its effects on immature animal models of TBI are unknown. In mature animal models, CsA inhibits the opening of the mitochondrial permeability transition pore (MPTP), thereby maintaining mitochondrial homeostasis following injury by inhibiting calcium influx and preserving mitochondrial membrane potential. The aim of the present study was to evaluate CsA's ability to preserve mitochondrial bioenergetic function following TBI (as measured by mitochondrial respiration and cerebral microdialysis), in two immature models (focal and diffuse), and in two different species (rat and piglet). Three groups were studied: injured+CsA, injured+saline vehicle, and uninjured shams. In addition, we evaluated CsA's effects on cerebral hemodynamics as measured by a novel thermal diffusion probe. The results demonstrate that post-injury administration of CsA ameliorates mitochondrial dysfunction, preserves cerebral blood flow (CBF), and limits neuropathology in immature animals 24 h post-TBI. Mitochondria were isolated 24 h after controlled cortical impact (CCI) in rats and rapid non-impact rotational injury (RNR) in piglets, and CsA ameliorated cerebral bioenergetic crisis with preservation of the respiratory control ratio (RCR) to sham levels. Results were more dramatic in RNR piglets than in CCI rats. In piglets, CsA also preserved lactate pyruvate ratios (LPR), as measured by cerebral microdialysis and CBF at sham levels 24 h after injury, in contrast to the significant alterations seen in injured piglets compared to shams (p<0.01). The administration of CsA to piglets following RNR promoted a 42% decrease in injured brain volume (p<0.01). We conclude that CsA exhibits significant neuroprotective activity in immature models of focal and diffuse TBI, and has exciting translational potential as a therapeutic agent for neuroprotection in children.

The role for osmotic agents in children with acute encephalopathies: a systematic review

BACKGROUND

Raised intracranial pressure (ICP) is known to complicate both traumatic and non-traumatic encephalopathies. It impairs cerebral perfusion and may cause death due to global ischaemia and intracranial herniation. Osmotic agents are widely used to control ICP. In children, guidelines for their use are mainly guided by adult studies. We conducted this review to determine the current evidence of the effectiveness of osmotic agents and their effect on resolution of coma and outcome in children with acute encephalopathy.

METHODS

We searched several databases for published and unpublished studies in English and French languages, between January 1966 and March 2009. We considered studies on the use of osmotic agents in children aged between 0 and 16 years with acute encephalopathies. We examined reduction in intracranial pressure, time to resolution of coma, and occurrence of neurological sequelae and death.

RESULTS

We identified four randomized controlled trials, three prospective studies, two retrospective studies and one case report. Hypertonic saline (HS) achieved greater reduction in intracranial pressure (ICP) compared to mannitol and other fluids; normal saline or ringer's lactate. This effect was sustained for longer when it was given as continuous infusion. Boluses of glycerol and mannitol achieved transient reduction in ICP. Oral glycerol was associated with lower mortality and neurological sequelae when compared to placebo in children with acute bacterial meningitis. HS was associated with lower mortality when compared to mannitol in children with non-traumatic encephalopathies.

CONCLUSION

HS appears to achieve a greater reduction in ICP than other osmotic agents. Oral glycerol seems to improve outcome among children with acute bacterial meningitis. A sustained reduction in ICP is desirable and could be achieved by modifying the modes and rates of administration of these osmotic agents, but these factors need further investigation.

New concepts in treatment of pediatric traumatic brain injury

Emerging evidence suggests unique age-dependent responses following pediatric traumatic brain injury. The anesthesiologist plays a pivotal role in the acute treatment of the head-injured pediatric patient. This review provides important updates on the pathophysiology, diagnosis, and age-appropriate acute management of infants and children with severe traumatic brain injury. Areas of important clinical and basic science investigations germane to the anesthesiologist, such as the role of anesthetics and apoptosis in the developing brain, are discussed.

Clinical outcome of severe head injury in different protocol-driven therapies

In the past 5 years cerebral perfusion pressure (CPP) management has become mainstream in the treatment of severe head injuries. The American Association of Neurological Surgeons guidelines (2000) suggest that CPP should be maintained at least 70 mmHg; however, there is still debate about optimal CPP level. The purpose of this study is to evaluate the effectiveness of three widely used therapies: intracranial pressure (ICP)-targeted therapy, CPP-targeted therapy with CPP > 70 mmHg, and modified CPP-targeted therapy with CPP > 60 mmHg. The clinical procedures, complications, and patient outcomes are compared. Data including patient age, sex, initial Glasgow Coma Score (GCS), ICP, CPP, fluid status, amount of mannitol and vasopressor used, daily intake and output, complications, and clinical results were collected from 213 patients with severe head injuries over a 12-year period. Patients were categorized into three groups (ICP, CPP, modified CPP [mCPP]) according to treatment protocol used. Retrospective data collection was by chart review. The mortality rate was 28.6%, 14.3%, and 13.5% in groups ICP, CPP, and mCPP, respectively. Highest intake/output ratio, amount of vasopressor used, and pulmonary complication rates were seen in group CPP patients. Group mCPP patients showed the best clinical outcome and lowest complication rate. Though CPP-targeted therapy is the most recommended therapeutic protocol, our data showed that the outcome is as good in the mCPP-targeted group with CPP > 60 mmHg as in the CPP-targeted group, but complications are fewer in the mCPP group.