Emergency Medicine Forum

I’m called to the resuscitation suite for a medical ‘code’.  As I walk into the room, I see a middle aged cyanotic female, in obvious respiratory distress, awake and talking to the nurse with one word sentences.

Looking to the nurse, I’m glad she quickly summarizes what she knows:  A 42 y/o female with cough, fever and respiratory distress. She got sick yesterday, and now can’t breathe.  Her husband brought her in. Her room air sat is only 72%.

Most of my history is from her husband.  She became acutely ill yesterday, and has progressively been getting worse.  He wanted to bring her yesterday to the ED, but she refused.  She is a nurse and thought she might be able to manage this at home.  She thought it was a virus, but now continues to get worse so finally she agreed to come to the ED.

ROS: No vomiting, diarrhea, rashes.  She has had a decreased appetite, and felt hot with chills on and off since yesterday.  She has been coughing up green sputum, and complains of chest pain when she coughs. 
PMH:   Negative, healthy with no medical problems.  G2P2
Allergies:  None
Medications:  Ibuprofen prn
SH: No smoking.  She has not been around patients who have had an unusual illness (according to her husband).  No unusual exposures.
FH:  Neg
PE: WDWN female, cyanotic as she is placed on oxygen, in obvious respiratory distress.
VS:  HR-140, RR=32, BP=140/85, Temp=101F, Sat (now on 100%NRB = 88)
HEENT:   Unremarkable, no JVD
Heart:  RR tachy, no murmurs
Lungs:  Rales bilaterally, no rhonchi
Abd: Scaphoid, non-tender
Ext:  No rashes
Neurologic: non-focal
CXR:  Non-cardiogenic pulmonary edema with multiple patchy infiltrates
WBC: 26K with 30% Bandemia
Lactate =4.2

Answers:

1. Should you intubate?

Depending on how bad she looks, you could try non-invasive ventilation.  The real issue, regarding the success of non-invasive ventilation (BiPap) is how quickly this is reversible.  Non-invasive ventilation is a great bridge for rapidly reversible conditions (CHF, COPD, and Asthma).  For pneumonia, it’s frequently not as successful as the condition (especially if bad enough to need ventilator assistance) and is not likely to be quickly reversible.  In fact, they may get worse before they begin to get better.   For this patient, she looked toxic, so I just intubated. (Even before the CXR was done as she was in extremis, and even with 100% NRB mask, her sat only came up to high 80’s).

2. What is ECMO?

ECMO stands for Extracorporeal Membrane Oxygenation.  It is sometimes called ECLS (Extracorporeal Life Support).  It was started in the 1970’s by Dr. Bartlett (from Michigan – Go Blue!) who successfully used it to treat neonates in severe respiratory distress. (1)

Essentially, it is a portable cardiopulmonary bypass device, which is placed using only local anesthesia via cervical cannulation.  It can support ventilation for 3-10 days, and can provide time for the lung to heal from numerous insults. 

3. How is Adult Respiratory Distress Syndrome (ARDS) defined?  What should your ventilator settings be?

Acute lung injury/ARDS is defined per the American–European Consensus Conference as acute onset of impaired gas exchange defined as:
a. Ratio of partial pressure of arterial oxygen in (mm Hg) to FiO2 (fraction of inspired oxygen) < 300
AND
a. Presence of bilateral alveolar or interstitial infiltrates in the absence of congestive heart failure. (3)If these two criteria are met, then the patient has ARDS. Doing the math, if the patient has a CXR consistent with ARDS, and is intubated on 100% oxygen (FiO2=1) and their partial pressure of oxygen based on the blood gas is 180, then the ratio is 180/1 which is less than 300!  So they have ARDS.

In the past, hypoxemia often seen in ARDS was managed by increasing the tidal volume. Initial tidal volumes on the ventilator of 10cc/ kg were common when I was a resident.  Subsequent research suggested these tidal volumes, which do increase oxygenation, also cause lung damage (ventilator-induced lung injury).

Ventilation with low tidal volume is very important in ARDS (Adult Respiratory Distress Syndrome). References recommend 6 ml/kg ideal body weight (3), or 6-8cc/kg (4) for tidal volumes. When you do the math, this means that the 55 kg woman you just intubated should have a tidal volume of 330 cc (if you use the reference recommending 6cc/kg).  This hypoventilation often results in hypercarbia (Permissive Hypercarbia). The initial respiratory rate is set at 18-22 breaths /min.  The goal is to have the plateau airway pressure of 30 cm of water or less. (4)  Clearly this may cause some respiratory acidosis.  Although these ventilator issues are most important in the ICU, it is still helpful for Emergency Medicine Clinicians to understand the rational behind it.  (5)

Outcome:

She was admitted to the ICU, and IV antibiotics, aggressive fluid and Sepsis management was initiated.  Ultimately, she was transferred to a University Hospital for ECMO as her oxygenation continued to deteriorate. Even with ECMO, however, she unfortunately died. Blood cultures grew out Group B Streptococcal. While this aggressive infection is usually seen in neonates, the incidence in non-pregnant adults appears to be increasing with an overall increase of 32% from 1999 to 2005. (6) The mortality rate is estimated to be at about 20%. (6)

I remember this case so well because she was healthy and fine just two days earlier.  I also remember she had high school kids, like I do. It’s such a strange tragedy. I never found what type of nurse she was, but I wash my hands more.

References: 

1. Rodriguez-Cruz E.  Walters H III.  Extracorporeal Membrane oxygenation.  Emedicine, Mar 18, 2008.  Accessed at: http://emedicine.medscape.com/article/904996-overview

2. Kacmarek RM, Wiedemann HP, Lavin PT. Partial liquid ventilation in adult patients with acute respiratory distress syndrome. Am J Respir Crit Care Med. Apr 15 2006; 173(8):882-9.  Accessed at: http://www.ncbi.nlm.nih.gov/pubmed/16254269?ordinalpos=&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.SmartSearch&log$=citationsensor

3. Malhotra A.  Low Tidal-volume Ventilation in the Acute Respiratory Distress Syndrome. NEJM 2007 Sept 13; 357(11):1113-1120.  Accessed at:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2287190/

4. Hamed HMF, Ibrahim HG, Khater YH, Aziz ES.  Ventilation and ventilators in the ICU:  What every intensivist must know. Curr Anaesthesia and Critical care 2006 17, 77-83.  Entire manuscript accessed at: http://emcrit.org/pdf/best%20review%20of%20ventilators%20and%20ventilation.pdf

5. Harmon EM.  Acute Respiratory Distress Syndrome Emedicine, Dec 7, 2009.  Accessed at: http://emedicine.medscape.com/article/165139-overview

6. Woods CJ, Levy CS.  Streptococcus Group B Infections.  Emedicine Nov 11, 2009. Accessed at: http://emedicine.medscape.com/article/229091-overview