Intensive Care Unit, Frenchay Hospital, Bristol BS16 1LE, UK
* Corresponding author. E-mail: alex.manara{at}north-bristol.swest.nhs.uk
Accepted for publication June 30, 2004.
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Abstract |
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Methods. A computerized patient database was used to identify all patients with severe head injury admitted to the ICU at Frenchay Hospital, Bristol, UK: a tertiary referral centre for the clinical neurosciences. We compared the ICU and hospital mortality and length of stay in patients before and after implementation of a protocol for their ICU management in 1997.
Results. Implementation of the protocol was associated with a significant reduction in ICU mortality from 19.95% to 13.5% (odds ratio 0.47; 95% CI 0.290.75), and in hospital mortality from 24.55% to 20.8% (odds ratio 0.48; 95% CI 0.310.74). This was achieved despite a significant increase in the median APACHE II score (14 vs 18) of patients admitted after implementation of the protocol. The median ICU and hospital length of stay remained constant over the study period.
Conclusions. The introduction of an evidence-based protocol to guide the ICU management of patients with severe head injury has been associated with a significant reduction in both ICU and hospital mortality.
Keywords: complications, head injury ; intensive care, audit
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Introduction |
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Methods |
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Statistics
The ICU and hospital mortalities and lengths of stay were compared between the two groups. Binary outcomes (ICU and hospital mortality) were analysed using logistic regression. Length of stay was analysed using Cox regression. Lengths of stay for patients who died in ICU were treated as censored observations. All analyses were adjusted for age, GCS and APACHE II scores. The Wilcoxon rank sum test was used to compare the age, GCS and APACHE II scores of the patients in the two groups, and a 2-test was used to test for differences in the sex distribution. All analyses were undertaken using 2001 Stata Statistical software (release 7.0; Statabase Corporation, College Station, TX, USA).
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Results |
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Discussion |
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Although there is no Class 1 evidence to support many of the specific interventions used in the management of head injuries,11 it is generally agreed that the aim of intensive care for these patients is to prevent, identify and treat the causes of secondary brain injury. The introduction of a protocol to manage severe head injuries based on the best available evidence supporting this aim was associated with a significant reduction in both ICU and hospital mortality. This was achieved without increasing the patients' length of stay in the ICU and despite a higher median age and APACHE II score in Group B patients. As the mortality on the wards after discharge from the ICU remained unchanged (Table 2), it is clear that, as might be expected, the major impact of the protocol was within the ICU itself.
Although the GCS and neurosurgical interventions of the two groups were similar, we would have expected the higher age and APACHE II score of group B patients to be associated with a higher mortality rate. The difference in age, while statistically significant, is unlikely to be clinically significant. We are unable to explain the differences in APACHE II scores between the groups. The difference almost certainly lies in the acute physiology scores of the two groups, and may reflect changes in referral and admission patterns during the study period. The act of transferring a patient from another hospital may result in deterioration in the physiological variables contributing to the APACHE II score on admission to our unit. However, there was neither a difference in the proportion of patients transferred before or after the implementation of the protocol (Table 1), nor a difference in the APACHE II scores of patients who underwent transfer when compared with those who did not.
This study, although retrospective, examined a large number of patients, but in the absence of randomization factors other than the protocol may be responsible for the observed improvement in outcome. These may include improvements in pre-ICU care, general intensive care management or high-dependency care after the ICU. The significant increase in the admission APACHE II score in Group B (Table 1) suggests that an improvement in pre-ICU care was not a major contributing factor. General intensive care management is likely to have improved over time, making it possible that other organizational changes within the ICU may have contributed to the change in ICU mortality. These would include increased numbers of ICU beds, an increase in medical and nursing staffing levels, and improved training in intensive care medicine. If these were major contributory factors, one would expect the mortality in patients with other diagnoses to have been reduced by a similar proportion to that observed in patients with head injuries. This was not the case, as the ICU mortality for patients without head injury did not change significantly (Fig. 3). Finally, while the opening of an HDU may affect the ICU length of stay and the hospital mortality, it should not influence the ICU mortality. Because the ICU length of stay was unchanged (Table 2) and the improvement in hospital mortality was primarily attributable to a reduction in ICU mortality, not post-ICU mortality, we can only conclude that the contribution of the HDU was not a significant factor.
Several other factors will have influenced the outcome measures chosen, particularly length of stay and hospital mortality. Workload pressure affects length of stay on both the ICU and in hospital, and care on the neurosurgical wards impacts upon hospital mortality. However, it is reassuring that the survival benefit observed extends beyond the ICU. In addition, the reduction in hospital mortality implies that the decrease in ICU mortality is not simply a result of transferring patients with a very poor prognosis to the ward. If post-ICU mortality could be further reduced, then the impact of the protocol on hospital mortality would be even greater. It is recognized that 2030% of intensive care patients who die will do so on the wards after discharge from the ICU,12 and that some of these deaths may be avoidable. We were disappointed to find that the opening of the HDU did not affect this post-ICU discharge mortality. This may reflect the use of the HDU primarily as an overflow ICU rather than as a proper stepdown facility or a unit for the care of elective surgical patients. The introduction of Outreach teams as recommended in Comprehensive Critical Care13 may address this issue in the future.
A study by Patel and colleagues14 reported that overall there was no reduction in mortality and no general improvement in outcome after the introduction of a head-injury management protocol, but observed significantly less morbidity in patients with severe head injuries (GCS <8) and in those with a raised intracranial pressure but no surgically remediable cause. At first sight, our results may appear to be better than those of Patel and colleagues.14 However, as our study was much larger than theirs (843 vs 285 patients), it is possible that their study lacked the power to identify a difference in hospital mortality. Furthermore, their baseline hospital mortality before the introduction of their protocol was lower than ours (22.7% vs 24.5%), yet the similarity between the mortalities in the two ICUs after the introduction of the protocol is remarkable (20.2% vs. 20.8%). Any reduction in mortality in their study would require many more patients to reach statistical significance. The effect of the protocol on their ICU mortality was not reported, which is unfortunate as the protocol is most likely to have the largest effect within the ICU, as demonstrated in our study.
Unfortunately, we do not have data on the long-term neurological function for our patients and cannot comment on this aspect of outcome. It is tempting to speculate that the combination of our results with those of Patel and colleagues14 may suggest that protocol-driven care may reduce mortality and morbidity in this population of patients. Patel and colleagues14 argue that the improvement they observed was due to the application of ICP/CPP-guided therapy within a specialist neurocritical care setting. The reduction in mortality that we observed was significant in patients with both severe (GCS 8) and less severe (GCS >8) head injuries, and in patients requiring neurosurgical intervention as well as those managed medically. Whilst it is possible that the improvements we noted may also be achieved by the application of protocol-driven care in a non-specialist ICU, we would agree with Patel and colleagues14 that there may be a case for managing all severely head-injured patients in specialist units. The comparative data from all types of ICU, provided by the Intensive Care National Audit and Research Centre (ICNARC), although open to many interpretations, adds weight to this argument (Table 4).
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Head injury remains a leading cause of death among young adults in the industrialized world,16 and survival with moderate or severe disability is more common than expected, even after a mild head injury.17 This study suggests that implementation of a protocol has resulted in a relative reduction in ICU mortality of almost 30% at this hospital. We would recommend that implementation of locally agreed guidelines, based on the available published evidence, facilitates the use of best practice and results in improved patient care.
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Acknowledgments |
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Footnotes |
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This article is accompanied by Editorial I.
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References |
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