Paucis Verbis: Does this adult patient need blood cultures?

Blood Cultures Bottle

Do you order blood cultures for all your ED patients with a fever? Obviously no. What’s your decision making process on ordering this test? There are really no findings or tests with high specificity (rules-IN bacteremia), except interestingly “shaking chills”. Notice almost all the criteria listed below approach a likelihood ratio (LR) of 1.0. Two prediction rules do exist, however, to help you virtually rule-OUT bacteremia:

  • SIRS
  • Shapiro prediction rule

The list of LRs also will be helpful to show learners in the ED that an isolated serum WBC number is useless risk-stratifier.

Patient Case

A 55 y/o man with a PMH of hypertension presents with a community-acquired pneumonia on CXR, no fevers, no chills, no vomiting.

  • Temperature 37.8 C, BP 160/90, HR 100, RR 16, Sat 100% RA
  • Serum WBC 20K (no bands)
  • Platelets 300K
  • Creatinine 1.1 mg/dL

What is the patient’s pre-test and post-test probability for having bacteremia? Use these helpful stats from the Rational Clinical Examination series from JAMA.

PV Card: Blood Cultures for Suspected Bacteremia


Adapted from [1]
Go to ALiEM (PV) Cards for more resources.

Answer to patient case

  • Start with 7% pretest probability for bacteremia with a community acquired pneumonia.
  • Using the clinical prediction rules, the WBC 20K and HR 100 bpm are criteria for SIRS but do not fulfill the Shapiro prediction criteria. LR = 1.8 * 0.08 = 0.144. Post-test probability for bacteremia = 0.06%.
  • If the patient had instead a normal HR of 80 bpm, both the SIRS and Shapiro criteria would have been negative. LR = 0.09 * 0.08 = 0.0072. Post-test probability for bacteremia = << 0.1%.

This discussion doesn’t address WHETHER we should get blood cultures despite a risk for bacteremia in the setting of uncomplicated pneumonia receiving IV antibiotics or pyelonephritis with a pending urine culture.

References

  1. Coburn B, Morris A, Tomlinson G, Detsky A. Does this adult patient with suspected bacteremia require blood cultures? JAMA. 2012;308(5):502-511. [PubMed]
  2. Shapiro N, Wolfe R, Wright S, Moore R, Bates D. Who needs a blood culture? A prospectively derived and validated prediction rule. J Emerg Med. 2008;35(3):255-264. [PubMed]
By |2021-10-10T08:43:50-07:00Aug 17, 2012|ALiEM Cards, Infectious Disease|

Paucis Verbis: Overanticoagulation and supratherapeutic INR

I find it amazing that I know more non-emergency physicians virtually in the social media world rather than in person. Primarily through Twitter, I follow and am followed by medical educators from various specialties. If you haven’t joined Twitter yet, I think it might be time. There is a whole world of collaboration and conversation going on in this virtual community, which crosses specialties and geography.

Last week, Dr. Javier Benítez (@jvrbntz) was tweeting a Question of the Day, referencing a 2010 Paucis Verbis card on overanticoagulation, which was based on the 2008 American College of Chest Physicians (ACCP) guidelines. About 8 minutes after I retweeted his question, Dr. Roy Arnold (@cholerajoe), a pulmonary/critical care physician kindly informed me that the 2012 ACCP guidelines have been out since February.

So this PV card is replacing the 2010 card with revised recommendations. For more in-depth discussion, definitely take a look at Dr. Scott Weingart’s great podcast over at EMCrit. He helps to clarify holes which the 2012 ACCP guidelines don’t really address such as:

What if the patient is minorly bleeding with a high INR?

  • Oral vitamin K and 15 mL/kg FFP

What if you only have the 3-factor PCC (factors II, IX, X) and not the recommended 4-factor PCC (factors II, IX, X plus factor VII)?

  • If PCC is indicated, add recombinant factor VIIa or FFP to the 3-factor PCC to cover for factor VII.

PV Card: Overanticoagulation and Supratherapeutic INR


Adapted from [1]
Go to ALiEM (PV) Cards for more resources.

Reference

  1. Holbrook A, Schulman S, Witt D, et al. Evidence-based management of anticoagulant therapy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012;141(2 Suppl):e152S-84S. [PubMed]
By |2021-10-10T08:47:06-07:00Aug 10, 2012|ALiEM Cards, Heme-Oncology, Tox & Medications|

Mythbuster: The 10% cephalosporin-penicillin cross-reactivity risk

RedSirenTo give or not to give a cephalosporin in penicillin-allergic patients?

I remember back to my days in pharmacy school when I learned that there was approximately a 10% risk of cross-reactivity, if a cephalosporin was given to a penicillin-allergic patient. They probably said something about the risk being less with 3rd and 4th generations cephalosporins, but lets be honest… who remembers anything but that magic 10%? When I started working more with physicians, I found that they also learned the same 10% rule in medical school. Well, I guess that means it’s fact, right? Not so fast!

(more…)

Paucis Verbis: D-Dimer test

LabD-Dimer: To order or not to order?

That’s the question when it comes to risk stratifying a patient for a pulmonary embolism with a low pretest probability. One should consider confounding conditions which may cause an elevated D-Dimer level. There’s always confusion about what may cause an elevated D-Dimer besides venous thromboemboli. So I thought I would make a pocket card as a reminder.

PV Card: D-Dimer Test


Adapted from [1]
Go to ALiEM (PV) Cards for more resources.

Reference

  1. Wakai A, Gleeson A, Winter D. Role of fibrin D-dimer testing in emergency medicine. Emerg Med J. 2003;20(4):319-325. [PubMed]
By |2021-10-10T08:49:42-07:00Jul 27, 2012|ALiEM Cards, Cardiovascular, Pulmonary|
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