CICM SAQ 2015.2 Q27
Question
A 60-year old male with no significant past medical history has been treated in your ICU for 21 days for severe staphylococcal sepsis and multi-organ failure, for which he is receiving linezolid.
He requires continuous renal replacement therapy (CRRT) and, despite therapeutic heparin to facilitate this, his filter keeps clotting. His platelet count has reduced from 154 x 106/L to 56 x 106/L from day 18 to day 21.
- a) List the four most likely differential diagnoses for the thrombocytopenia. (20% marks)
- b) Discuss your investigation for the thrombocytopenia. (40% marks)
- c) Outline your immediate management of this problem. (40% marks)
Answer
Answer and interpretation
a) List the four most likely differential diagnoses for the thrombocytopenia. (20% marks)
- Linezolid
- Consumption coagulopathy (from clotting on renal replacement therapy)
- Pseudothrombocytopenia (i.e., platelet clumping)
- Sepsis induced including DIC
- Heparin induced (HIT or HITTS)
- TTP/HUS (less likely)
b) Discuss your investigation for the thrombocytopenia. (40% marks)
Exclude pseudothrombocytopaenia
Increased consumption
- Repeat blood count and request for film to determine platelet clumping, evidence of haemolysis (schistocytes)
- Coagulation testing to include D-dimers, fibrinogen
- Blood cultures
- HITTS screen
- ELISA test for anti-platelet factor 4 antibody
- More specific but more technically difficult – platelet aggregation test
- Autoimmune screen (dsDNA)
- ADAMTS13 screening for TTP
Decreased production
- Bone marrow aspiration (+/-bone marrow biopsy)
- Urea / creatinine for HUS
- ‘HIT screen’
- Miscellaneous
- Drugs, sepsis, alcohol, bone marrow suppression
c) Outline your immediate management of this problem. (40% marks)
- Reassess need for linezolid but it will need to be ceased and commenced on less bone
marrow toxic anti-microbial to cover Staph aureus (vancomycin/teicoplanin) - No need to provide platelet support unless bleeding actively
- Minimise need for renal support while trying to understand thrombocytopenia, if urgently
needed will need to consider safety of anti-coagulating circuit in view of low platelet count. - Consider alternative strategies for circuit maintenance
- No anticoagulation
- Citrate
- Prostacyclin
- Thrombin antagonists
- LMWH
- Increased systemic heparinisation (if HITTS unlikely)
- Pass rate: 67%
- Highest mark: 8.8
Additional Examiners’ Comments:
- Most candidates passed but there was overall a knowledge gap on the management of this clinical problem.
Examination Library
CICM
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.
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