What issues would you consider in providing renal replacement therapy to a 22-year-old patient with a traumatic brain injury and raised intracranial pressure?
How would you manage these issues?
Type of RRT:
Intermittent Hemodialysis likely to be associated with rapid fluid and solute shifts with increase in cerebral oedema and ICP – avoid.
CRRT better choice
Higher threshold for commencement in the context of raised ICP.
Risk of rebound intracranial hypertension if dialysate/replacement fluid sodium concentration is lower than plasma – consider using high sodium containing fluids
Consider using filtration rather than dialysis if possible to minimise fluid & solute shifts and rebound increase in cerebral oedema
Risk of hypotension when starting circuit and reduction in CPP: Start with small volume exchanges, ensure patient is not hypovolaemic prior, have vasopressor ready
Risk of circuit anticoagulation in traumatic brain injury leading to intracranial haemorrhage. Consider no anticoagulation, or strategies that only anticoagulate circuit – e.g. citrate
Consider placement of dialysis catheter – avoid jugular veins as risk of obstruction of venous outflow and haematoma
Use of RRT may affect temperature management
Candidates scored higher marks if they demonstrated sound knowledge of how parameters on the renal replacement prescription could be altered to improve safety for the patient.
There is plenty of literature to support this answer, and to make it somewhat more organised. Andrew Davenport published an excellent review article in 2007. He also published another excellent review article in 2008 to describe a practical approach to the issues involved. Both reviews are updates of an article he published in 2001. A slightly more recent experiment by Yeh et al (2016) focuses on the prevention of ICP fluctuations during RRT by modifying the IHD protocol. Recommendations from these studies can be summarised as follows:
|Access||Avoid internal jugular lines||Promote venous drainage from the brain|
|Modality||Prefer CRRT||Produces a more gradual solute clearance;
less likely to produce cerebral oedema
|Low efficiency IHD/SLED|
|Frequency||Daily, if not continuous||Daily treatments decrease the fluctuations of urea|
|Blood flow||Start low, increase slowly||Minimise haemodynamic effects|
|Dialysate flow||Start low, increase slowly||Minimise solute clearance|
|Dose||Under-dialyse (by half)||Minimise solute clearance per unit time|
|Solute clearance||Pre-dilution haemofiltration||Minimise urea clearance: decrease the resulting urea gradient between brain parenchyma and blood, minimising cerebral oedema|
|Filtration||Low volume fluid removal||Minimise dialysis-associated hypotension to prevent cerebral hypoperfusion|
|Anticoagulation||Regional, or none||Prevent cerebral haemorrhage extension due to anticoagulation. Minimal anticoagulation is recommended for 2 weeks following TBI.|
|Dialysate||Add sodium||Minimise the hyponatremia which develops due to exposure to hyponatremic dialysate (to keep sodium around 145-150 mmol/L)|
|Add urea||Minimise urea clearance|
|Minimise bicarbonate||Prevent intracellular acidosis (may be hypthetical)|
|Fluid warmer||Temperature matching||Maintain therapeutic hypothermia if this is being used for ICP control|
Davenport, Andrew. "Renal replacement therapy in the patient with acute brain injury." American journal of kidney diseases37.3 (2001): 457-466.
Davenport, Andrew. "Renal replacement therapy for the patient with acute traumatic brain injury and severe acute kidney injury." Acute Kidney Injury. Vol. 156. Karger Publishers, 2007. 333-339.
Davenport, Andrew. "Practical guidance for dialyzing a hemodialysis patient following acute brain injury." Hemodialysis International 12.3 (2008): 307-312.
Yeh, Shih-Hao, Chen-Yu Wang, and Chien-Min Lin. "Preventing intracranial pressure fluctuation in severe traumatic brain injury during hemodialysis." Journal of Medical Sciences 36.4 (2016): 152.