Which of the following statements is MOST likely to be true of continuous renal replacement therapy (CRRT) in comparison to intermittent hemodialysis (IHD):
Correct Answer: B
IHD is an efficient dialysis technique, which is performed over 3 to 4 hours. CRRT is less efficient, as it is continuous over an entire 24-hour period. IHD allows for early mobilization of patients compared to CRRT but is not tolerated well in hemodynamically unstable patients. Hence the most recent KDIGO guidelines recommend CRRT in hemodynamically unstable patients. Dialysis-induced increase in intracranial pressure is more likely to occur in patients undergoing IHD. This is postulated to occur due to the rapid removal of solutes and consequent fluid shifts. The slower fluid and solute removal with CRRT minimizes its occurrence.
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A 44-year-old male with a long-standing history of insulindependent diabetes mellitus is admitted to the intensive care unit (ICU) with diabetic ketoacidosis. He has acute kidney injury (AKI) and is being started on hemodialysis in the ICU.
Which of the following is the LEAST preferred route for vascular access insertion for renal replacement therapy (RRT)?
Correct Answer: D
The site and length of vascular access catheters play an important role in the provision of optimal RRT. The subclavian vein is the least preferred route for vascular access insertion intended for RRT. Contact of the catheter with the vessel wall and subsequent thrombosis could result in vessel stenosis, jeopardizing the possibility for an arteriovenous fistula in case the patient remains dialysis-dependent.
Right internal jugular vein is the preferred vein for hemodialysis access as the vein takes a straight path into the superior vena cava (SVC). Access through the left internal jugular vein requires the catheter makes two right angles prior to reaching the SVC resulting in a higher incidence of catheter dysfunction. The length of the catheter is equally important with optimal flows occurring when the catheter tip is positioned in the right atrium SVC junction for internal jugular access and in the inferior vena cava for femoral access. Appropriate lengths of catheters need to be chosen for this purpose. The right internal jugular, femoral, left internal jugular, and subclavian are recommended in order as options for vascular access in patients requiring RRT. The right internal jugular vein should be the first consideration for hemodialysis access.
Which of the following techniques does hemodialysis employ for solute clearance?
Correct Answer: A
The goals of RRT could be one or a combination of the following—solute and fluid clearance, normalization of electrolytes, and acid-base status. This could be achieved through diffusion or convection, depending on the modality of RRT.
In diffusion, which is employed in hemodialysis, blood and the dialysate fluid flow in a countercurrent fashion on either side of the semipermeable membrane of the hemofilter. The driving force that moves solutes across the semipermeable membrane is the solute concentration gradient. Diffusion is effective in removing small molecules, such as potassium, ammonium, and creatinine (<20 kDa). It is less efficient in removing larger solutes and water.
In hemofiltration, a convective process is utilized wherein solutes and water are transported across the membrane by a pressure differential. Pressure forces water and consequently “drags” solutes with it from the blood compartment to the so-called effluent compartment. The permeability coefficient of the membrane and the difference in pressure between both sides of the membrane determine the amount of fluid and solutes transported across the membrane. With a large amount of fluid removed, crystalloid replacement is given back to the patient to restore circulating volume.
A 63-year-old female has been admitted to the ICU from another hospital with ongoing acute upper gastrointestinal bleeding, necessitating multiple blood transfusions. She has a history of a previous coronary artery bypass grafting and end-stage renal disease (ESRD) on dialysis. The records from the other hospital indicate that she was recently diagnosed with heparin-induced thrombocytopenia (HIT). She is due to get her dialysis today and feels short of breath after the blood transfusions.
Which of the following is the MOST ideal anticoagulation strategy for hemodialysis in this patient?
All forms of heparin should be avoided in a patient with recent history of HIT. Anticoagulation strategies in patients with HIT requiring hemodialysis include regional anticoagulation with citrate or use of direct thrombin inhibitors. Parenteral direct thrombin inhibitors—argatroban, danaparoid, and lepirudin—have been used for this purpose. Dabigatran, an oral direct thrombin inhibitor is contraindicated in patients with ESRD and hence cannot be used in this patient. Dialysis without anticoagulation can be used in an acutely bleeding patient, requiring hemodialysis, but filter clogging can lead to acute drop in hematocrit from blood lost in the dialysis circuit and is not usually preferred. Regional citrate anticoagulation is an option in patients with HIT, requiring dialysis.
In which of the following clinical scenarios is RRT LEAST likely to be urgently initiated?
While hyperkalemia >6 mEq/L with ECG abnormalities is an absolute indication for RRT, asymptomatic hyperkalemia >6 mEq/L is only a relative indication, especially in a patient with ESRD. In the setting of AKI, metabolic acidosis with a pH <7.15, diuretic resistant fluid overload, and hypermagnesemia >8 mEq/L with anuria and absent deep tendon reflexes are absolute indications for RRT. In patients with AKI, refractory metabolic acidosis, diuretic resistant fluid overload, and hypermagnesemia >8 mEq/L with anuria are absolute indications for initiation of RRT.
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