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8/21/2012 - Critical Care Conference with Dr. Eisen

posted Aug 21, 2012, 10:54 AM by Rohit Das   [ updated Aug 21, 2012, 1:00 PM by Purnema Madahar ]

Today we had our monthly Internal Medicine-Critical Care Medicine conference, and M&M of sorts, in which we talk about patients we’ve taken care of who’ve had, one way or another, “critical care” issues. Julie Lorton presented a patient with pulmonary embolism and significant hypoxemia, and Diane Chang presented an elderly patient with Pneumonia, Sepsis, and Respiratory Failure.

We talked about PE in the context of overdiagnosis last week. Since it’s a pretty common topic, let’s go into some different aspects. Specifically, along with the theme of our conference today, here are some things to remember regarding PROGNOSIS for patients with pulmonary emboli:

  • Evidence of RV dysfunction is a poor prognostic factor for PE, with meta analyses citing a 2-fold increase in mortality. The prevalence of RV dysfunction in PE is fairly variable in the literatures, with estimates ranging from 40-70%.
  • Elevations of pro-BNP levels, probably reflective of RV strain, also is associated with a worse outcome, with literature citing a 6-10 fold increase in mortality depending on the extent of the elevation. Similarly, positive troponins are a poor prognostic sign, with an odds ratio for PE-specific mortality of 9.4 (cited from a meta analysis of observational studies).
  • Finally, concurrent DVT is a poor prognostic factor (which represents about 30-40% of patients with PE), with a hazard ratio of PE-specific mortality of ~4 in prospective studies.

Many prognostic models have been created for pulmonary embolism as well, the most common of which is probably the “PESI” (Pulmonary Embolism Severity Index) Score. In the attached Annals study, they nicely go through predictive data for both the original PESI Score, and a simplified PESI score that they specifically studied:

  • Table 1 on this article compared the original and simplified PESI scores. Using univariate and multivariate analysis, the authors decided which variable to keep in the simplified score, and assigned all those variable a value of 1; simply – 0 is low risk, ≥1 is high risk. This risk is for short-term (30 day), PE specific mortality.
  • Table 4 gives a nice comparison summary of the predicative capabilities of the two scores. The NPV and –LR for both scores are similar, and fairly powerful (97-99% and 0.12-0.3, respectively). The positive predicative capabilities are not nearly as strong (PPV – 10.9%, +LR of 1.44).
  • So, bottom line, the simplified score is similar in its predicative capabilities for short term, PE-related mortality as compared to the original score. Unfortunately, it is only useful for predicting which patients who are NOT at risk for short-term mortality.

The second case we talked about was a pretty classic scenario of an elderly woman with Sepsis in the setting of PNA, leading to ARDS. Let’s just review some definitions and basic concepts:

  • SIRS (Systemic Inflammatory Response Syndrome) is a nonspecific inflammatory syndrome associated with both infectious and noninfectious insults. It’s characterized by ≥2 or more of: Temp >38.3 C/< 36 C; Pulse > 90; Resp Rate > 20/PaCO2 <32 mmHg; WBC >12k/<4k/>10% bands
  • Sepsis = SIRS + infection. Severe Sepsis = Sepsis with evidence of hypoperfusion or organ dysfunction (several ways to assess this – skin, lactate levels, DIC, ARDS…etc.)
  • Septic Shock = Severe Sepsis with hypotension (<60…or <80 mmHg in a patient with a history of HTN) that is refractory to adequate fluid resuscitation and/or requires pressors.

The management of sepsis is complex, and a nice review article on the management of the different aspects of managing sepsis is attached. The main issues to address immediately are – assess someone’s respiratory status, restore adequate perfusion and initiate immediately (some studies who an increased mortality with a delay as small as an hour…) and appropriately (not covering the right bugs is also associated with a higher mortality …particularly not covering for Staph).

  • ARDS is defined by an acute presentation (<1 week) of respiratory failure, that is not clearly explained by cardiac failure in the setting of bilaterally pulmonary infiltrates on chest imaging. There must also be significant impairment of oxygenation, with a Pa02/FiO2 of ≤ 300 (by Berlin criteria, this would be defined as “mild” ARDS).
  • Along with sepsis, management of ARDS is probably one of the most well-studied aspects of ICU care, with strong data supporting particular intricacies of ventilator settings. Attached is the ARDS-NET Trial, as well as a nice ARDS Clinical Therapeutics paper – both from NEJM. Some key points:
    • The most important aspect of these recent data is the concept of low-tidal volume ventilation (defined as 6cc/kg) versus high tidal volume. The latter is associated with higher mortality and increased incidence of “ventilator-induced lung injury.” This was a huge finding at the time.
    • As a result of hypoventilation, the low tidal volume approach inevitably leads to hypercapnia, which is deemed “permissive,” except in patients with cerebral disease or seizure disorder (both of which are contraindications for permissive hypercapnia).
    • Appropriate oxygenation is attained both by increasing FiO2 and PEEP. There is much debate as to whether to take a low or high PEEP strategy; Table 1 of the Malhotra summarizes the FiO2 and PEEP combinations in the ARDS Network trial, which is based on the threshold of maintaining a plateau pressure of ≤ 30 mmHg.
A lot of numbers today...that's a good thing, try to get them in your head...Thanks for reading, until tomorrow!!
Simplification of the Pulmonary Embolism Severity Index for Prognostication in Patients with Acute Symptomatic PE
Jimenez et. al., Arch Intern Med 2010; Volume 170 (15): 1383-1389

Wheeler et. al., NEJM 1999 Volume 340: 207-14

The ARDS Network, NEJM 2000 Volume 342(18): 1301-08

Malhotra, NEJM 2007 Volume 357(11): 1113-20