NEWS & VIEWS TRAUMATIC BRAIN INJURY
Intracranial pressure monitoring in traumatic brain injury Bertil Romner and Per-Olof Grände
A randomized study has indicated that continuous monitoring of intracranial pressure (ICP) in patients with traumatic brain injury does not improve outcome compared with care based on imaging and clinical examination. The results do not, however, justify elimination of continuous ICP measurement from standard care in patients with head injury. Romner, B. & Grände, P.-O. Nat. Rev. Neurol. 9, 185–186 (2013); published online 12 March 2013; doi:10.1038/nrneurol.2013.37
Raised intracranial pressure (ICP) is a lifethreatening condition that can result in brainstem compression and compromised brain circulation. Increased ICP is the most common cause of death in patients with severe traumatic brain injury (TBI). Monitoring of ICP is, therefore, a reasonable approach to discover a progressive increase in ICP in these patients. Chesnut and colleagues have recently published an interest ing randomized, multicentre controlled trial that investigated whether treatment decisions that are based on ICP monitoring are associated with improved outcomes compared with decisions that are not based on information from ICP data in patients with TBI.1
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ICP monitoring is generally viewed as the cornerstone of care in ... TBI
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Introduced by Nils Lundberg in 1960,2 continuous monitoring of ICP has been increasingly used in clinical practice and today is a routine procedure worldwide in patients with severe TBI. ICP monitoring is generally viewed as the cornerstone of care in these patients, and is recommended in all modern guidelines for treatment of TBI. However, studies showing beneficial effects of this approach are lacking. Shafi et al.3 showed that ICP monitoring in patients with TBI is associated with worsening of survival compared with patients who did not undergo ICP monitoring, and a study by Cremer et al.4 did not find evidence of improved outcome in patients with severe head injury when ICP monitoring was used.
The clinical trial by Chesnut et al.1 was cond ucted in hospitals in Bolivia and Ecuador, and involved 324 patients aged 13 years or older. The study consisted of two groups: a pressure-monitoring group in which ICP was maintained at ≤20 mmHg using the conventional guidelines for management of severe TBI,5 and an imaging–clinical examination group in which treatment decisions were based on imaging and clinical examination only. The primary outcome was a composite measure of survival time, impairment of consciousness, functional status at 3 and 6 months and neuropsychological status at 6 months. The researchers found no significant difference in patient outcome between the two groups. Mortality was 39% in the pressure-monitoring group and 41% in the imaging–clinical examination group at 6 months. The results did, however, show a trend towards improved survival in the pressure-monitoring group at 14 days, with mortality of 21% compared with 30% in the imaging–clinical examination group, although this difference was not significant (P = 0.18). The median length of stay in the intensive care unit (ICU) and the incidence of adverse events were similar in the two groups. The authors suggested the high mortality at 6 months might be related to the limited health-care resources available to patients after discharge from the ICU. Furthermore, none of the study participants received rehabilitation or extensive medical care after hospital discharge.1 The results of this study 1 and others3,4 suggest that direct monitoring of ICP as the main source of information regarding brain injury status does not improve outcome
NATURE REVIEWS | NEUROLOGY
in patients with head injury, which could raise questions about the value of using ICP monitoring. The low degree of surgical trauma associated with insertion of the catheter to measure ICP is unlikely to affect outcome or patient survival, even though this procedure is associated with a small risk of bleeding and intracranial infection.6 According to the study by Chesnut et al.,1 patients in the ICP-monitoring group did not experience such complications. In this study, the effect of ICP monitoring on outcome, therefore, may have depended on how ICP monitoring affected the choice of therapy.
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...results of this study ... could raise questions about the value of using ICP monitoring
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This study raises questions about effects of randomization on patient outcome. Random assignment of patients into groups for analysis of the effect of a specific treatment, such as a drug or a therapeutic monitoring strategy, always incurs a risk of bias. For example, the use of an investigational drug or recording device could have effects that require changes to the rest of the therapy, which might in turn have negative effects on patient outcome. The benefits of receiving information about brain injury status from ICP monitoring could be concealed by adverse effects of treatments that are selected on the basis of ICP data. For example, if high ICP is treated with vasopressors to maintain cerebral perfusion pressure, the effects of the vasopressors could worsen outcome.7,8 In such patients, VOLUME 9 | APRIL 2013 | 185
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NEWS & VIEWS the outcome would be affected not only by the modification of ICP per se, but also by the specific way in which ICP is con trolled. Alternative guidelines for the treatment of severe TBI8 have been introduced because of possible adverse effects of some of the current recommendations.5 A reasonable assumption is that, if the ICP value is unknown, fewer ICP-reducing therapies are likely to be used. Chesnut et al. 1 reported considerable differences in treatment regimens between the two groups. For example, high-dose barbiturates were administered more frequently to the pressure-monitoring group than to the imaging–clinical examination group, who received more hypertonic saline and hyperventilation, which may have had secondary effects on outcome. High-dose barbiturates are known to have severe adverse effects in terms of pulmonary, circulatory and renal complications,9,10 which could have influenced the trial outcome. Hypertonic saline might also have adverse effects, causing electrolyte disturbances and an increase in ICP on its withdrawal, and vasopressors can trigger pneumonia and adult respiratory distress syndrome.7 The results from the study by Chesnut et al. 1 do not support the view that ICP monitoring is superior to neurological examination and serial CT imaging in guiding decisions for treatment of patients with severe TBI. This finding does not, however, mean that combination of these two strategies is not an effective strategy. We find it difficult to accept that continuous ICP monitoring is of no value if the resulting information is used to guide treatment strategies correctly. The results from the study by Chesnut et al.1 should, therefore, not be used as an argument against the use of ICP monitoring. Department of Neurosurgery Rigshospitalet, Blegdamsvej 9, DK‑2100, Copenhagen, Denmark (B. Romner). Department of Aesthaesia and Intensive Care, Lund University Hospital, Getingevägen 4, 221 85 Lund, Sweden (P.‑O. Grände). Correspondence to: B. Romner
[email protected] Competing interests The authors declare no competing interests. 1.
2.
Chesnut, R. M. et al. A trial of intracranialpressure monitoring in traumatic brain injury. N. Engl. J. Med. 367, 2471–2481 (2012). Lundberg, N. Continuous recording and control of ventricular fluid pressure in neurosurgical practise. Acta Phsyciatr. Neurol. Scand. Suppl. 36, 1–193 (1960).
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Shafi, S., Diaz-Arrastia, R., Madden, C. & Gentilello, L. Intracranial pressure monitoring in brain-injured patients is associated with worsening of survival. J. Trauma 64, 335–340 (2008). Cremer, O. L. et al. Effect of intracranial pressure monitoring and targeted intensive care on functional outcome after severe head injury. Crit. Care Med. 33, 2207–2213 (2005). Brain Trauma Foundation et al. Guidelines for the management of severe traumatic brain injury. XIV. Hyperventilation. J. Neurotrauma 24 (Suppl. 1), S87–S90 (2007). Koskinen, L. O. & Olivecrona, M. Clinical experience with the intraparenchymal intracranial pressure monitoring Codman MicroSensor system. Neurosurgery 56, 693–698 (2005).
7.
Content, C. F., Valadka, A. B., Gopinath, S. P., Hannay, H. J. & Robertson, C. S. Adult respiratory distress syndrome: a complication of induced hypertension after severe head injury. J. Neurosurg. 95, 560–568 (2001). 8. Grände, P. O. The “Lund Concept” for treatment of severe head trauma— physiological principles and clinical application. Intensive Care Med. 32, 1475–1484 (2006). 9. Schalén, W., Messeter, K. & Nordström, C. H. Complications and side effects during thiopentone therapy in patients with severe head injuries. Acta Anaesthesiol. Scand. 36, 369–377 (1992). 10. Nadal, P., Nicolás, J. M., Font, C., Vilella, A. & Nogué, S. Pneumonia in ventilated head trauma patients: the role of thiopental therapy. Eur. J. Emerg. Med. 2, 14–16 (1995).
TRAUMATIC BRAIN INJURY
Giving voice to a silent epidemic Martin Rusnak
A large epidemiological study of traumatic brain injury (TBI) in New Zealand has contributed to filling the knowledge gap on TBI incidence and severity. To improve health outcomes, however, public health practice must translate such findings into policies and intervention strategies. Rusnak, M. Nat. Rev. Neurol. 9, 186–187 (2013); published online 12 March 2013; doi:10.1038/nneurol.2013.38
The term ‘silent epidemic’ is used to charac terize the incidence of traumatic brain injury (TBI) worldwide, in part because many cases are not recognized and are, therefore, excluded from official statistics. A recently published study conducted in New Zealand1 has provided an example of how scrupulous epidemiological research can elucidate the incidence of TBI. For this research, Feigin and colleagues combined data from prospective and retrospective surveillance systems to ensure registration of all TBI events in residents of all ages within a 1‑year period. The results of the Brain Injury Outcomes New Zealand In the Community (BIONIC) study suggest that the incidence of TBI, especially mild TBI, is far greater than would be estimated from the findings of previous studies conducted in other high-income countries. The study involved populations in urban and rural settings, and included mild TBI and moderate or severe TBI. Feigin et al.1 documented a total incidence of 790 TBI cases per 100,000 person years, which were predominantly (95%) mild TBI cases. Of the 1,369 individuals with TBI, 70% were children, adolescents or young adults, and male individuals were more likely to sustain TBI than were females (relative risk 1.77).
38% of TBI cases were due to falls, with mechanical forces, transport accidents and assault accounting for most other cases. In addition, incidence of moderate to severe TBI was almost 2.5 times greater in rural than in urban populations.1
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...many cases [of TBI] are not recognized and are ... excluded from official statistics
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The differences in TBI incidence across age, gender and mechanics documented by the BIONIC study were congruent with those described by similar studies in developed countries. Populations in such studies are characterized by ageing, which is associated with increased risk of falls, and high mobility of young adults, which increases the risk of motor vehicle accidents. The BIONIC study represents a unique approach to the epidemiology of TBI by incorporating mild, moderate and severe injuries. Cases of moderate and severe injuries are most frequently studied, given the clear case-definition cri teria for such injuries, whereas mild cases are more prone to misdiagnosis or neglect by patients and clinical personnel, which could introduce substantial bias. www.nature.com/nrneurol
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