Case 31: Diagnostic Testing

Case 31 Index

Take a look at some initial testing below (click!):
Head CT Scan

The patient’s head CT is normal without evidence of intracranial hemorrhage, extracerebral fluid collection, midline shift or mass effect. There is some artifact from patient motion.
Basic labs

protein BMP

You are able to locate an ultrasound machine and obtain the point-of-care ultrasound images below (click!):
Inferior vena cava (IVC)
Here, you see an IVC < 21 mm in diameter with < 50% variation with respiration
Here, you see A-lines without B-lines.

A post-intubation chest x-ray reveals a small right sided pleural effusion as well as the tip of HeRO graft (hemodialysis access graft) in the right atrium. 

Hm…what’s a HeRO graft?
A type of catheter that can be placed in any large vein and used for hemodialysis in patients with numerous vascular complications
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A graft more durable than polytetrafluethylene (PTFE) that can be used to create distal upper extremity arterio-venous grafts (AVGs).
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A graft more durable than polytetrafluethylene (PTFE) that can be used to create lower extremity arterio-venous grafts (AVGs).
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An access that connects an artery in the upper extremity directly to the heart through a completely subcutaneous route.
Excellent! The HeRO (Hemodialysis Reliable Outflow) graft is composed of venous and arterial outflow component. It is placed in the upper extremity and the tip of the outflow component  is placed in the right atrium. An anastomosis between the arterial outflow component and target inflow artery in the upper extremity is performed.
Image reference
What next? Choose the highest yield diagnostic tests below!
Blood cultures
While obtaining blood cultures to investigate sepsis is reasonable, especially in the setting of pleural effusion and right femoral dialysis catheter, this is not the highest yield test as the patient has no evidence of systemic inflammatory response  and infection is lower on differential. Try again!
Diagnostic thoracentesis
Not the highest yield test here. The small pleural effusion is less likely to explain this patient’s clinical presentation. If the patient subsequently develops evidence of infectious process, this might be a higher yield test. Pick again! 
Not so fast! Respiratory failure might tempt us to choose this test, but there are some higher yield, less invasive tests that may be more informative. Pick again! 
Ventilation/Perfusion (V/Q) Scan
Great thought – though in this anuric ESKD patient without residual kidney function, there might be a better test with better sensitivity and specificity. Choose again!
Computed tomography pulmonary angiogram (CTPA)
Excellent! This test reveals an acute pulmonary embolism straddling the bifurcation of right and left pulmonary trunk with bilateral multiple sub-segmental PE’s.
Transesophageal echocardiogram (TEE)
Close – we might be able to get enough information from a less invasive test. Pick again!
Transthoracic echocardiogram (TTE)
Great! In the setting of unexplained hypotension, this is an appropriate test. The TTE reveals a dilated right ventricle, hypokinetic RV, akinesia at mid-free wall but normal motion at apex (McConnell’s sign). The right ventricular systolic pressure is 50 mm Hg. There is an acute thrombus that appears to be originating from the tip of the HERO catheter tip in the right atrium

Click here once you’re ready to wrap up this case!

Case 31 Index
Case 31 Introduction
Case 31 Physical Exam