Delirium, an acute change in consciousness and attention,1 has been referred to as “acute brain failure.” Negative health outcomes associated with delirium after hip fracture include death, loss of independence, and nursing home placement.2,3 In an analysis of 459 patients with hip fracture repair, Gottschalk et al.4 challenge the association between delirium and one of those outcomes, mortality, in this issue of Anesthesia and Analgesia. Although delirium on postoperative day 2 was associated with longitudinal mortality (with follow-up for up to 13 years) in univariate analysis, this association did not hold up on multivariate analysis. Thus, challenging the view that postoperative delirium predicts mortality.
Delirium unquestionably remains a common, underrecognized health crisis, and hip fracture patients are a vulnerable group. In the cohort by Gottschalk et al., 84% of patients had functional impairment and 26% met the authors’ definition of preoperative cognitive impairment. The team-based care described involved orthopedic surgery, anesthesia, as well as geriatrics, was state of the art. Randomized control trial evidence shows that geriatric collaboration reduces the incidence of delirium (risk ratio [RR], 0.64; 95% confidence interval [CI], 0.37–0.98).5 A recent meta-analysis found that geriatric collaborative care for hip fracture patients associated with a reduction in in-hospital mortality (RR, 0.60; 95% CI, 0.43–0.84) and long-term (6 months to 1 year) mortality (RR, 0.83; 95% CI, 0.74–0.94).6 Thus, it is possible that the lack of association between delirium and mortality in the study by Gottschalk et al. was due to the fact that the care model did what it was intended to do, namely, prevent delirium and associated untimely death in a subset of the cohort.
In fact, the reported incidence of delirium in this study (33%) is likely an underestimate. The authors excluded older patients with preoperative delirium (23%), a highly vulnerable group for postoperative delirium and mortality. Previous work suggests that the peak incidence of postoperative delirium occurs on postoperative day 2,7 and this is when the authors conducted the delirium assessment. However, delirium does develop on other days.7 The characteristic feature of delirium is fluctuating cognition, and this requires systematic assessment; previous research has found that 75% of delirium will be missed unless such an assessment is used.8–11
Other limitations should temper conclusions about delirium and mortality in this patient population. The patients in this analysis were seen by a geriatrician, which, as already mentioned, reduces the delirium rate. By potentially eliminating cases of delirium that might be seen in a more typical care setting, the mortality conclusions may not be generalizable to a more typical care setting where such multidisciplinary care is not available. Also, differences between in-hospital mortality and out-of-hospital mortality are not described. In general, patients with a difficult postoperative course are more likely to be admitted to the intensive care unit (ICU), and these patients are more likely to develop delirium.12 The Kaplan-Meier curves for delirium and ICU admission (Fig. 1, panels B and D, of the accompanying article by Gottschalk et al.4) illustrate as much, with the delirium group initially declining steeply. Finally, there is likely collinearity among the dependent variables identified in multivariate analyses, age at the time of surgery, ASA physical status score, and duration of ICU admission, which is a testament to the complexity of delirium and makes disentangling the impact of each variable difficult. However, the authors’ multivariable model nicely demonstrates and reinforces the overlapping risks and causes of delirium. They confirm, for example, other work that shows that delirium is intimately related to baseline cognitive function and age, as well as severity of illness.13
Delirium is increasingly, and rightly, recognized as an emergent postoperative condition. Clinical practice guidelines for postoperative delirium have recently been published by the American Geriatrics Society and the American College of Surgeons.14,15 Unfortunately, understanding the pathogenesis of delirium is poor, and it is unlikely that a single, linear causal pathway exists.16 Meager investments in delirium research, $14 million by the National Institutes of Health in fiscal year 2014 compared with $1.1 billion in Alzheimer disease research that year,17 make it improbable that causal mechanisms will be identified any time soon.
In the meantime, we must take aggressive steps to avoid, identify, and treat postoperative delirium. In this respect, there are several important takeaways for clinicians from the work of Gottschalk et al. First, delirium is common after hip fracture and, unless systematic screening occurs, is likely to be underrecognized. Second, vulnerable patients are more likely to develop delirium and have a difficult postoperative course. Third, the geriatric-orthopedic-anesthesiology collaboration model represents a significant advance in care that should be adopted more widely. Finally, although this study did not confirm an association between delirium and mortality, it makes a strong case that delirium after hip fracture repair is a morbid condition that deserves our utmost attention.
Name: James L. Rudolph, MD, SM.
Contribution: This author wrote the manuscript.
Attestation: James L. Rudolph approves and attests to the integrity this manuscript.
This manuscript was handled by: Gregory Crosby, MD.
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