Patwari Academy videos: Respiratory failure and ventilators
Dr. Rahul Patwari reviews the basics of respiratory physiology, the pathophysiology behind respiratory failure, and ventilator management. What do all the ventilator settings mean?
Lytics for sub-massive PE: Ready for primetime?
There was recently a great study published in the American Journal of Cardiology (2012) by Sharifi et al1, questioning whether we should be considering tPA in patients other than those patients with massive pulmonary embolism (PE)? You know the big “Saddle Embolus” we all fear? Well it turns out this is only about 5% of all PEs.
Should we be considering tPA in patients with sub-massive PEs?
PE in pregnancy: which diagnostic tests do you use?
Pulmonary embolism (PE) can be a deadly disease and one of the most challenging diagnosis to make in a pregnant patient. Patients may present with signs and symptoms that might also be present in a normal uncomplicated pregnancy. Even in nonpregnant patients, the diagnosis of venous thromboembolism (VTE) such as PE can be quite challenging.
PV card: VBG versus ABG
You 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
- 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]
- 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]
- 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]
- 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]
- 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]
PV card: PE Severity Index (PESI) score
Do you send some of your low-risk patients with pulmonary embolism home?
This is a controversial issue which warrants a look at risk stratification tools. The primary one used is the validated Pulmonary Embolism Severity Index (PESI) score. In Lancet 2011, the authors looked at whether PESI class I and II (low risk) patients could be managed safely as outpatients. It turns out in their study, regardless of whether their PESI class I and II patients were treated as outpatients and inpatients, all fared equally well from a complications standpoint (recurrent clot, bleeding from anticoagulation).
I like the validated PESI scoring system to risk-stratify patients as low vs high risk for complications. I, however, do caution people to look closely at the exclusion criteria for this study before applying this to all ED patients.
The exclusion filter was so strict that they likely have captured a very narrow and unrealistic scope of patients to be widely applicable. It makes sense from a research standpoint to have these criteria to achieve internal validity but the question is external validity. Two exclusion criteria that struck me as awfully strict were: (1) needing parenteral opioids or (2) active alcohol or drug abuse.
Bottom line
For me, this study alone seems not have enough external validity to decide about the decision to treat PE patients as inpatient vs outpatient. Although I think that ultimately some can be managed as outpatients, I’d like to see more studies.
PV Card: PESI Score for Pulmonary Embolism
See other ALiEM (PV) Cards.
Paucis Verbis: D-Dimer test
D-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
- Wakai A, Gleeson A, Winter D. Role of fibrin D-dimer testing in emergency medicine. Emerg Med J. 2003;20(4):319-325. [PubMed]