UCONN Emergency Medicine Interest Group

Archive for the ‘OFF SERVICE’ Category

Off Service #3: Critical Care

In OFF SERVICE on February 4, 2012 at 5:19 PM

I’m in the ICU this month, where acid-base disorders are more the rule than the exception. One issue that frequently comes up is metabolic acidoses and the specter of mixed acid-base disorders looming its ugly head. I feel this topic is frequently made overly complex, and thus ends up being ignored, when figuring it out is really not that complicated. I think this is because of the delta gap, or in Dr. Henry’s words, the “delta-delta”:

Delta-delta = (measured anion gap from labs – normal anion gap)/(normal HCO3 – measured HCO3 from labs) = (measured anion gap from labs – 12)/(24 – measured HCO3 from labs)

I think this equation gets easily confused because of the fact that the calculation involves subtraction in the denominator. Since I am not particularly facile at math at the drop of a hat (or at least, not with an ICU team as my audience), I will outline the very simple way that I have reasoned how to determine if a mixed acid-base disorder is present, in a way that should be easy to remember:

In the setting of an INCREASED anion gap metabolic acidosis (AKA an anion gap metabolic acidosis):

If there is an additional METABOLIC ALKALOSIS…

HCO3 is HIGHER than it should be, therefore…
The denominator is SMALLER, therefore…
The delta-delta is BIGGER, and…
If the delta-delta > 2, there is an increased anion gap metabolic acidosis AND a metabolic alkalosis.

If there is an additional NON-ANION GAP METABOLIC ACIDOSIS…

HCO3 is LOWER than it should be, therefore…
The denominator is BIGGER, therefore…
The delta-delta is SMALLER, and…
If the delta-delta < 1, there is an increased anion gap metabolic acidosis AND a non-anion gap metabolic acidosis.

For a more comprehensive discussion, see this selective project created by a UCONN student here.

Why should you care? Well, particularly if you are resuscitating with large volumes of normal saline (which contains a lot of chloride), the pH may not give a full indication of what is going on with the patient, and you may make changes in your management accordingly. For instance, you might want to switch to Lactated Ringers as your IV fluid.

Click below to see a BONUS section on patients with hypoalbuminemia, and how not to miss metabolic disturbances in this population!

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Off Service #2: Heme/Onc

In OFF SERVICE on August 26, 2011 at 7:00 AM

Dr. Gilcrease, Heme/Onc Fellow, University of Utah/Huntsman Cancer Institute

Approach towards neutropenic fever

1. Identify using definitions:

  • ANC < 500 (or will be <500 in 48 hrs, but this is difficult for EPs to determine). Profound neutropenia is ANC < 100.¬†Note: this count includes neutrophils and bands (but not more immature cells).
  • Fever = any T>38.3 (101 F), or T>38 (100.4) for >1 hr.¬†Note: the elderly and pts on corticosteroids may not mount a fever! Also,¬†remember that not all fever = infection.

2. Risk stratify

  • Hisk risk by IDSA 2010 criteria: ANC<100 for >7 days, comorbidities (including GI sx, neuro sx, central venous catheter infection, etc.), hepatic injury (transaminases >5x upper limit of normal), renal insufficiency (CrCl<30)
  • Alternative risk stratification is the MASCC score, but this is more complicated; if used, score >=21 is high risk.
  • If high risk, hospitalize and give IV abx.
3. Initial management
  • Exam- be thorough, do not forget skin, mucosal, port-a-cath, central lines, wounds, abdominal exam. Remember that neutropenic pts frequently will not show signs of infection (eg. abscess, induration, warmth, pulmonary infiltrate). DO NOT do a rectal exam (may cause a bacteremia).
  • Labs- CBC, CMP, UA, directed imaging, blood cx from central venous catheter if present and 2 peripheral sites, directed tests as needed (eg. LP, wound cx, CDiff toxin, stool cx).
  • Abx: within 2 hrs of presentation.
    • Outpatient: cipro/augmentin or levofloxacin
    • Inpatient: meropenem +/- vancomycin
      • If any mucosal breakdown, skin breakdown, concern for central-line infection, pneumonia, give a dose of vanco.

Off Service #1: OB/GYN

In OFF SERVICE on April 18, 2011 at 8:02 PM

This is the first entry in what will be a recurring series. Seasoned attendings from specialties outside EM will be asked the following question: “What clinical advice would you give students going into Emergency Medicine regarding an acute issue in your field?”

Dr. Larhmann, OB/GYN, Hartford Hospital:

1. Order type and Rh on pregnant women that come into the ED with a complaint of bleeding, and give Rhogam if appropriate. Rhogam needs to be given within 72 hours to be effective.

2. Consider the diagnosis of preeclampsia if a pregnant woman comes in with headache and visual changes- order a UA and LFTs!

3. Don’t rely on serum B-hCG level for figuring out gestational age; remember that it has a bell-shaped curve.

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