Critical care: what’s old is new

As compared to the exciting technological and pharmacological advances we have witnessed in some other medical specialties, progress in critical care medicine often resembles the recycling of fashion trends: the adage “what’s old is new” comes to mind. While rheumatologists are improving lives with the anti-TNF antibodies that failed in our sepsis trials, and cardiologists’ stents and statins have slashed mortality from myocardial infarction, we intensivists are left rehashing debates such as whether corticosteroids are again en vogue for sepsis.1

The tools of critical care medicine – ventilator, central line, vasopressor, antibiotics, corticosteroids, sedatives – have changed little in decades. To our credit, what has changed are patient outcomes we have squeezed out of our static therapeutic armamentarium. Despite an aging population with an increasing burden of comorbidities, the past two decades have seen substantially reduced mortality rates for hallmark critical illness syndromes such as severe sepsis.2,3 A patient with severe sepsis today (20-30% case-fatality) has almost ½ the mortality of a patient with severe sepsis of similar illness severity in 1990 (45-50% case-fatality). However, outcome trends in ARDS are less clearly positive.4

Are such differences inherent to these disease processes, or are there still gains to be made in patient outcomes? What is the nature of the complex interplay between emerging evidence and changing physician practice patterns? What pushes individual clinicians to implement evidence? Here we explore the very different evidence uptake patterns for three fundamental interventions during critical illness: pressure-volume limited ventilation during ARDS, noninvasive ventilation during acute respiratory failure, and central venous catheters during septic shock, presented through the literary cliché of the Three Bears.

Pressure-volume limited ventilation in ARDS: too cold?

The poor uptake of pressure and volume limited mechanical ventilation strategies for patients with ARDS has been well-documented.5,6 Although tidal volumes in ARDS have declined over time, 5 years after publication of the ARDSNet ARMA trial only 40% of patients with ARDS in the ARDSNet centers were receiving <6.5 cc/kg tidal volume prior to trial enrollment.5 Major factors contributing to underuse of pressure-volume limited ventilation likely include difficulties recognizing ARDS,7 and a “one-tidal volume fits all” approach that does not take into account the actual height of the patient.5 Is the conspicuous absence of specific societal guidelines on how to ventilate patients with ARDS – now 13 years since the ARMA trial – also slowing implementation of lung protective ventilation?

Noninvasive ventilation for acute respiratory failure: too hot?

Noninvasive ventilation (NIV) has been shown to improve mortality in patients with acute exacerbations of COPD8 and heart failure.9 Despite the different evidence base for COPD and heart failure as compared with other causes of respiratory failure, uptake of NIV into routine practice has occurred at a similar rate regardless of the etiology of respiratory failure.10 Importantly, when NIV is used outside the evidence it is more likely to fail and NIV failure is associated with increased mortality. Given the ease of using NIV and its demonstrated success in COPD and heart failure, we may be too enthusiastic about putting NIV on everyone who is short-of-breath, without always critically thinking about why they are dyspneic. Clinical practice guidelines provide variable recommendations as to use of NIV for non-COPD/heart failure indications.11,12,13 Could a false sense of security generated by success with using NIV for COPD/heart failure, coupled with ambivalent societal guidelines, be driving over-exuberant use of NIV?

Early resuscitation during severe sepsis and septic shock: Just right?

Outcomes are improving markedly for patients with severe sepsis and septic shock. What are we doing right? One possibility (but certainly not the only one), is improved early resuscitation. Since 1998, ‘real world’ population-based data from the Nationwide Inpatient Sample has demonstrated that use of central venous catheters (necessary, but not sufficient, to implement early goal directed therapy)14 in the first 24 hours of septic shock has increased more than 3-fold.15 What is fascinating is that prior to the 2001 Rivers et al. trial showing improved outcomes for patients receiving early goal directed therapy, the mortality associated with receiving a central venous catheter for septic shock was stable (risk-adjusted odds ratio of 1.29). Could this be because before Rivers et al, the central venous catheter did not come with any evidence-based instructions? Right heart catheters and arterial lines still do not come with instructions for use, and they have had a constant associated mortality rate in septic shock since 1998.15 Remarkably, risk-adjusted mortality associated with an early central venous catheter in septic shock began to decline after 2001: now receiving a central venous catheter early during septic shock is associated with a decreased risk of death (risk-adjusted odds ratio 0.87). Results from the PROCESS trial now indicate that the increase in central line utilization for septic shock is likely not driving the outcome improvement in sepsis.16 However, the early placement of a central line during severe sepsis may serve as a marker for an increased attention to other evidence-based sepsis therapy. These improvements have come simultaneously with the Surviving Sepsis Campaign and Guidelines which have specifically outlined goals for early sepsis therapy.

Conclusion

These vignettes show various ways in which evidence is being implemented for three common critical illness syndromes. Each syndrome appears to have different evidence uptake patterns. Why? Whereas the Surviving Sepsis Campaign may stimulate more rapid uptake of evidence into practice for severe sepsis,17 or ambivalence in NIV Guidelines may stimulate over-exuberant use of NIV outside the evidence, lack of societal guidelines may be hindering uptake of lung-protective ventilation in ARDS. The American Heart Association’s Get With the Guidelines program has established registries of millions of patients with heart failure, myocardial infarction, stroke, and cardiac arrest to monitor uptake of evidence.18 Perhaps it is time to follow the American Heart Association’s lead and begin to implement professional societally-organized, large scale registries to study processes of care for the major non-cardiac critical illness syndromes. By more consistently and rationally applying the evidence we have, we might squeeze out further improvements from our limited armamentarium to get more patient outcomes just right.