Question 5.2
5.2 Following initiation of CVVHD, the following alarm is noticed (see figure below). What are the likely causes and what measures will you undertake?
College Answer
Causes
Insufficient flow noted in the venous access limb (afferent).
Obstruction along the venous access limb from the lumen in the vein to the pump
Measures
Check line for obvious kinks/obstructions
Check position on x-ray if relevant (subclavian or IJ line)
Reposition line and ensure no clot.
Consider flushing line
Consider replacing line/ site esp if the low access flow state cannot be resolved.
Discussion
This question closely resembles Question 12 (specifically, section 12.3) from the first paper of 2009.
The image granted to us by the college is fairly unambiguous.
There is a big red sign saying "Low Access Pressure".
To simplify revision, I will reproduce the answer to Question 12.3 below:
First, one should check the access side of the circuit, beginning with the patient:
- Patient position - is it appropriate? Are they agitated?
- The vas cath is of poor design (i.e. you should have inserted a short widebore vas cath, with a circular lumen crossection)
- Vas cath up against the wall of a vessel
- Vas cath is kinked
- Vas cath tip is getting clotted
- The blood flow to the vas cath is poor:
- The patient is hypovolemic
- There is increased intrathoracic or intraabdominal pressure, decreasing venous flow past the catheter tip
- The patient is breathing without positive pressure ventilation, and is hyperventilating (deep panicked breaths create a strongly negative intrathoracic pressure during inspiration, which pulls blood in the opposite direction, out of the vas cath).
The general approach to troubleshooting the CRRT circuit is summarised in a chapter from the Required Reading section.
References
The Gambro PRISMA Systems Operator's Manual is a wealth of information. However, it is very long.
This excellent nursing resource from Nepean ICU by Keren Mowbray is both succinct and complete.
So is this one (also from Nepean, by Alison Bradshaw - but it appears to be in Comic Sans)
Ricci, Zaccaria, Ian Baldwin, and Claudio Ronco. "Alarms and troubleshooting."Continuous Renal Replacement Therapy (2009): 15.
Carson, Rachel C., Mercedeh Kiaii, and Jennifer M. MacRae. "Urea clearance in dysfunctional catheters is improved by reversing the line position despite increased access recirculation." American journal of kidney diseases 45.5 (2005): 883-890.