Five Studies (Day 1)

Hi everyone:

With interview season over, we just have to wait. Being a touch obsessive (maybe more than a touch), I’d be thinking about nothing else until Match Day if I didn’t stay busy. So I’m glad to be on service all month: a week of MICU, two of Step Down, then one more in the MICU.

The MICU is my clinical home. Before becoming Program Director, I was an ICU director from 1995 to 2010. It was a transformative time in critical care. As a resident and fellow, much of ICU practice was driven by personal preference and theory, from ventilator modes to IV fluids to weaning strategies. We pushed oxygen delivery with dobutamine, dialed up tidal volumes to combat hypercapnia, and sedated patients to oblivion so they could “sleep” through their illness.

But all of a sudden, study after study produced practice-changing evidence. Dogma was challenged, theories were subjected to rigorous investigation, and the focus was shifted to patient-centered outcomes like survival. The best studies remain relevant today. For example:

• Effect on the Duration of Mechanical Ventilation of Identifying Patients Capable of Breathing Spontaneously by Ely et al (1996). This landmark study was done by my friend Wes Ely, who is now an internationally renowned physician scientist at Vanderbilt. At the time, Wes was a Chief Resident wondering how we could extubate patients more quickly and safely. In this paper, he and his colleagues showed that a nursing and respiratory therapist-led protocol, emphasizing daily spontaneous breathing trials, led to faster extubation and fewer complications- which is why we now do daily SBTs in the ICU. Wes’s paper also highlighted the importance of partnering with our talented nursing and respiratory therapy colleagues.
• A Multicenter, Randomized, Controlled Clinical Trial of Transfusion Requirements in Critical Care by Hébert et al (1999). Before this study was published, we routinely transfused patients when their hemoglobin fell below 10 g/dL (I’ve always assumed it was because 10 is a double digit). In this multicenter trial known as the Transfusion Requirements in Critical Care (TRICC) study, Hébert and his colleagues in the Canadian Critical Care Trials Group showed that it was generally safe to restrict transfusions until a patient’s hemoglobin fell below 7 g/dL, which remains our threshold today. Just imagine how much blood was saved, and how many cases of TRALI and TACO were prevented by, this study!
• Daily Interruption of Sedative Infusions in Critically Ill Patients Undergoing Mechanical Ventilation by Kress et al (2000). I’m eternally frustrated by heavy-handed sedation, which I presume to be driven by a wish to keep patients comfortable and prevent them from yanking out tubes. Unfortunately, patients pay a price when they’re sedated too heavily: their blood pressures drop, they’re more likely to become delirious, they can’t participate in physical therapy, and they can’t communicate their needs. It’s especially frustrating when we can’t extubate them because they’re too sleepy to protect their airways or breathe, sometimes for days after the sedatives are stopped. In this study, J.P. Kress (a fellow at the time and now a leader in critical care) and colleagues at the University of Chicago showed that pausing sedative infusions each day led to more rapid extubation and decreased ICU length of stay. To this day, “spontaneous awakening trials” remain standard of care for most patients requiring continuous sedation.
• Ventilation with Lower Tidal Volumes as Compared with Traditional Tidal Volumes for Acute Lung Injury and the Acute Respiratory Distress Syndrome by The Acute Respiratory Distress Syndrome Network (2000). When I was a resident and fellow, we chose tidal volumes by multiplying the patient’s weight by 10- so a 70 kg patient would get 700 mL tidal volumes. I try not to think about the number of patients whose lungs were damaged by that strategy. Everything changed with this landmark study by the NIH-sponsored ARDSNET, which showed that lower tidal volumes, targeting 6 mL/kg ideal body weight and a plateau pressure <30 cm H₂O, decreased mortality in patients with ARDS. Since then, low tidal volume ventilation (LTVV) has been our standard for ventilating patients with ARDS.
• Comparison of routine and on-demand prescription of chest radiographs in mechanically ventilated adults: a multicentre, cluster-randomised, two-period crossover study by Hejblum et al (2009). Before this study, we got daily chest x-rays on most intubated patients, assuming we needed films to know if patients’ lines or tubes had become displaced, or if they had developed a pneumothorax, pleural effusion, pulmonary edema, or pneumonia. Each morning, radiology techs came to the ICU to take films, and after rounds we reviewed the x-rays with the radiologists. To the surprise of many, Hejblum’s study showed that getting a film every day was no better than getting them when needed, for example after a procedure or when a patient’s condition changed. Since then, the number of chest x-rays done in the MICU has plummeted. In an accompanying editorial, Dr. Ami Rubinowitz and I endorsed this approach, provided the teams paid close attention to changes in patients’ conditions and as long as chest x-rays could be performed and interpreted promptly. An unintended consequence from this practice change is that ICU teams spend less time speaking face to face to our radiologists, which we can correct by reviewing studies with them when questions arise.

One of the rewards of becoming an expert is the opportunity to use research to help patients. This is true throughout medicine and especially in the MICU, where nearly everything we do, or should do, is driven by evidence. Every Sunday for the rest of March, I’ll serve up five studies which have transformed medical critical care and stood the test of time.

Enjoy your Sunday everyone, I’ll be spending today on MICU Red with Eman, Sarita, and Steph.

Mark

P.S. What I’m reading and listening to:

• Can a Vaccine Cure the World’s Deadliest Cancer? On Plain English with Derek Thompson
• Lightening up By Melissa Kirsch
• The big idea: the simple trick that can sabotage your critical thinking By Amanda Montell