Pan-scan CT: Not just for trauma?

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Zaf Qasim
Zaf Qasim
Dr Zaf Qasim is an attending physician in Emergency Medicine and Critical Care based at the University of Pennsylvania in the United States. He has particular interests in trauma, prehospital care and advanced resuscitation including endovascular techniques. You can find him on Twitter as @ResusOne

The Pre-brief

Your team has just finished resuscitating a 61-year-old man who suffered a cardiac arrest at home. Standard ACLS ensued ultimately resulting in a return of spontaneous circulation. Further history is obtained from a family member – the patient seemed to be doing “just fine” before he collapsed. Diagnostics in the resuscitation bay yield little additional information as to a cause. The MICU resident asks if obtaining a pan-scan will help narrow down a cause for the arrest.

What does the literature say?

 Branch et al recently published on just this topic – read their paper here in the journal Academic Emergency Medicine. 

Here is a summary of the paper:

  •   Prospective observational study carried out at two academic centers in Seattle between December 2015 and February 2018.
  •   Protocol involved obtaining a head-to-pelvis “sudden-death CT” (SDCT) within 6 hours of return of circulation.

o   Consent for the scan was obtained when feasible.

o   Scan included a non-contrast head CT, electrocardiogram-gated cardiac and thoracic CT angiogram, and a nongated venous-phase abdominopelvic CT angiogram

  •   Inclusion criteria

o   SDCT within 6 hours of OHCA event

o   No obvious cause for OHCA identified in the ED

o   Hemodynamic stability to undergo SDCT

  •   Exclusion criteria

o   Acute ST-elevation myocardial infarction or other indication for emergent angiography

o   Known non-revascularized coronary artery disease

o   Known severe renal dysfunction (eGFR < 30 mL/h/1.73m2, creatinine >1.7mg/dL) unless the SDCT was still deemed to be warranted by the ordering physician

o   Implantable defibrillator

o   Known contrast allergy

o   Known hospice patient or terminal disease with <3 months expected survival

  •   Primary outcomes

o   Number of OHCA causes found on SDCT as compared to adjudicated cause (adjudication by an emergency physician and cardiologist)

o   Frequency at which SDCT identified time-critical findings affecting clinical management (such as acute coronary syndrome, pulmonary embolism, aortic dissection, abdominal aortic rupture, or pneumonia)

  •   Safety endpoints

o   Development of acute kidney injury (AKI)

o   Inappropriate intervention performed based on SDCT findings

o   Development of allergic reactions from SDCT implementation



What did they find?

  •   104 patients enrolled (of 307 patients presenting to two centers)

o   Mean age 56 years (+/-15)

o   Male sex 69%

o   Race – White 61%, Black 16%

o   Witnessed arrest 59%

o   Bystander CPR 60%

o   Initial rhythm VF/VT 29%, asystole 25%, PEA 38%

  •   Mean time to SDCT was 1.8h from hospital arrival
  •   Cause of OHCA arrest identified in 39% (41/104)

o   Acute coronary syndrome (13/14)

o   Pneumonia (9/9)

o   Hemorrhagic stroke (2/2)

o   Pulmonary embolism (3/3)

o   Heart failure (5/6)

o   Abdominal catastrophe such as perforated viscus or mesenteric ischemia (3/3)

  •   Time-critical findings were identified in 44% patients (44/104)

o   Identified on SDCT in 98% cases (43/44) including:

  • Organ laceration (liver, spleen or lung)
  • Pericardial or mediastinal bleeding
  • Pneumothorax
  • Pneumonia
  • Hemorrhagic stroke
  • Hemorrhage related to vascular access
  •   SDCT identified a cause exclusively in 13/104 (13%) cases
  •   Safety endpoints

o   55% had elevated creatinine at presentation

  • 25% undergoing SDCT developed AKI
  • 28% had persistent elevated creatinine at 48 hours
  • One patient needed renal replacement therapy

o   No incidence of inappropriate interventions based on SDCT findings or contrast allergies

What were the limitations?

  •   The results of the SDCT were not completely blinded clinically, and hence may have affected the adjudicated diagnosis
  •   Majority of patients did not undergo a SDCT
  •   Whether AKI was due to the initial insult (OHCA) or contrast use is not able to be determined
  •   Whether the findings of the SDCT affected overall outcomes was not evaluated

What does this mean?

The authors determined that performing a post-OHCA pan-scan CT was feasible and may have a role in identifying potential causes of the arrest.  If you don’t look for something of course, you won’t find it. This study shows there are things to find, but it is still to be determined whether looking is beneficial to outcomes. Nevertheless, it can be presumed that early identification of,for example, injuries (which may have caused the arrest or been an effect of resuscitation efforts) is beneficial to patient care and likely outcomes.

The Debrief

  • Pan-scan CT post-OHCA may identify causes of the arrest not immediately evident by other routine investigations in a small number of cases.
  •   Time-critical problems do occur (either causing the arrest or as a result of the resuscitation) and the CT scan protocol may be useful in the early identification of this.
  •   The described protocol is relatively safe.
  •   Further prospective randomized study is necessary to determine the usefulness of this approach on outcomes.

References

Branch KRH, Strote J, Gunn M, et al. Early head-to-pelvis computed tomography in out-of-hospital circulatory arrest without obvious etiology. Acad Emerg Med 2021 Apr;28(4):394-403 PMID: 33606342

 Viniol S, Thomas RP, Konig AM, et al. Early whole-body CT for treatment guidance in patients with return of spontaneous circulation after cardiac arrest. Emerg Radiol. 2020 Feb;27(1):23-29. PMID 31468207

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