Vascular Access Recirculation: A Hidden Threat to Kidney Replacement Therapy
Unveiling the Mystery of a Rare Case
Vascular access recirculation (AR) is a silent saboteur, often overlooked in continuous kidney replacement therapy (CKRT). This case report sheds light on a rare scenario where AR occurred without conventional warning signs, such as circuit pressure alarms, in a 75-year-old woman with diabetes and hypertension. The patient underwent a complex surgery for cervical cancer, which led to acute kidney injury requiring CKRT with regional citrate anticoagulation (RCA).
The Diagnostic Puzzle
Despite uninterrupted CKRT-RCA, the patient experienced persistent high anion-gap metabolic acidosis and worsening uraemia. The absence of circuit pressure alarms and stable haemodynamic parameters made the diagnosis challenging. However, a unique calcium profile emerged as a diagnostic clue: rising systemic total and ionized calcium levels, with a stable total-to-ionized calcium ratio, requiring a decrease and eventual discontinuation of intravenous calcium replacement.
Uncovering the Culprit
Simultaneous blood sampling from the systemic circulation, access limb, and post-filter circuit revealed significantly lower access line urea, total and ionic calcium levels compared to systemic levels, confirming AR. The underlying cause was identified as clots partially occluding the infrarenal inferior vena cava, which was confirmed by a computerised tomography (CT) venogram.
The Impact of AR
This case highlights the diagnostic value of targeted biochemical sampling from systemic, access, and circuit ports. It also underscores the importance of maintaining a high index of suspicion for AR, even in the absence of typical warning signs. The patient's persistent metabolic abnormalities were likely due to significant AR, resulting in a "very low dose of CKRT" being delivered, partially meeting ongoing metabolic demands but failing to correct the abnormalities.
A Call for Vigilance
This report expands our understanding of AR in CKRT-RCA and emphasizes the need for strategic diagnostic sampling when faced with persistent treatment failure. Physicians should be vigilant for atypical biochemical patterns, especially in calcium dynamics, as they may signal occult circuit dysfunction. The case also raises questions about the optimal timing of AR diagnosis and the potential impact of delayed detection on patient outcomes.
Controversy and Comment
Is the current approach to diagnosing AR in CKRT-RCA sufficient? Should more frequent monitoring of post-filter ionized calcium be considered? How can we improve the early detection of AR to ensure timely intervention and better patient outcomes? Share your thoughts and experiences in the comments below.
