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PV card: VBG versus ABG

abg vbgYou obtain a venous blood gas (VBG) on a patient with a COPD exacerbation because you are concerned about hypercarbia. You get a value of 55 mmHg. How correlative is that compared to an arterial blood gas (ABG). There has been a lot of literature on how well the pH correlates between the ABG and VBG but what about pCO2?

A small study (n=89) from 20121 found that with a cutoff of pCO2 < 45 mmHg, the venous pCO2 is 100% sensitive in ruling out arterial hypercarbia. When the pCO2 was ≥ 45 mmHg, the VBG was less correlative.

Below is a review by Dr. Michelle Reina (EM resident at Univ of Utah) and Dr. Rob Bryant (Intermountain Medical Center in Utah) of the VBG vs ABG correlative data, along with a proposed algorithm on what to do with patients with COPD exacerbation.

What is your practice with an elevated pCO2 value on VBG?


Adapted from [1–5]
Go to ALiEM (PV) Cards for more resources.

Updated 1/31/13 at 2 pm PST:

  • Changed range of pH correlation between VBG and ABG = 0.03-0.04
  • Was typo in abstract of Kelly et al article.2 Stated difference between pHs was 0.4, rather than 0.04 as described in main results text.

References

  1. McCanny P, Bennett K, Staunton P, McMahon G. Venous vs arterial blood gases in the assessment of patients presenting with an exacerbation of chronic obstructive pulmonary disease. Am J Emerg Med. 2012;30(6):896-900. [PubMed]
  2. Kelly A, McAlpine R, Kyle E. Venous pH can safely replace arterial pH in the initial evaluation of patients in the emergency department. Emerg Med J. 2001;18(5):340-342. [PubMed]
  3. Ma O, Rush M, Godfrey M, Gaddis G. Arterial blood gas results rarely influence emergency physician management of patients with suspected diabetic ketoacidosis. Acad Emerg Med. 2003;10(8):836-841. [PubMed]
  4. Middleton P, Kelly A, Brown J, Robertson M. Agreement between arterial and central venous values for pH, bicarbonate, base excess, and lactate. Emerg Med J. 2006;23(8):622-624. [PubMed]
  5. Koul P, Khan U, Wani A, et al. Comparison and agreement between venous and arterial gas analysis in cardiopulmonary patients in Kashmir valley of the Indian subcontinent. Ann Thorac Med. 2011;6(1):33-37. [PubMed]
By |2021-10-08T09:26:47-07:00Jan 31, 2013|ALiEM Cards, Endocrine-Metabolic, Pulmonary|
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PV card: Diagnosis of DVT (ACCP guidelines)

DVT

A patient presents with an asymmetric leg with trace pitting edema in the affected leg. What is your diagnostic approach to such a patient? What is the role of D-dimer and ultrasound (U/S)? Does this match the 2012 American College of Chest Physicians (ACCP) guidelines?

The first step is to determine your patient’s pretest probability because the recommendations vary based on risk. I can tell you that many ED patients come in with a Wells score of 1-2, which places them in the “moderate pretest probability” category. There are 2 approaches you can take based on the availability of resources at your site (high-sensitivity D-dimer or U/S) and the patient’s comorbidities. Are you referring your patient for a repeat outpatient ultrasound, if warranted?Walk through various patient scenarios to see how the D-Dimer and U/S come into play.

PV Card: Diagnosting DVT – ACCP Evidence Based Guidelines


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

Thanks to Dr. Jason West (EM resident at Jacobi/Montefiore) for this card idea and deciphering the complex recommendations from the publication.

Reference

  1. Bates S, Jaeschke R, Stevens S, et al. Diagnosis of DVT: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012;141(2 Suppl):e351S-418S. [PubMed]
By |2021-10-08T09:29:18-07:00Jan 24, 2013|ALiEM Cards, Cardiovascular|
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