MCQ-Ultrafiltration in the ICU

Q1. A 58-year-old woman with ischaemic cardiomyopathy (LVEF 30%), vasopressor-dependent septic shock, and +11 L cumulative fluid balance is started on CRRT. Within 90 minutes, she becomes hypotensive despite only 150 mL of net fluid removal. What is the primary determinant of ultrafiltration tolerance in this patient?

a. Total degree of fluid overload

b. Integrated cardiovascular reserve — vascular refilling, cardiac output, venous capacitance, and vascular tone

c. Net fluid balance over 24 hours

d. Serum albumin concentration

Q2. A vasopressor-dependent patient with biventricular dysfunction and severe pulmonary oedema undergoes passive leg raising (PLR) before CRRT initiation. Pulse pressure and VTI show no meaningful change. The nurse asks: “Does the negative PLR mean she’s safe to ultrafilter?” The most accurate response is:

a. Yes — a negative PLR confirms haemodynamic stability

b. Yes — cardiac output is already maximised, so fluid removal cannot reduce it further

c. No — it excludes preload-mediated instability but does not rule out hypotension from impaired vascular tone, venous recruitment failure, or myocardial stunning

d. No — a negative PLR in vasopressor-dependent patients always indicates occult hypovolaemia

Q3. Two hours into a CRRT session at 100 mL/hr net ultrafiltration, a vasopressor-dependent patient becomes hypotensive. Only 200 mL has been removed. What is the most likely mechanism, and what is the most appropriate immediate response?

a. Preload depletion — administer a crystalloid bolus

b. Dialysis-induced myocardial stunning — pause ultrafiltration and reassess with point-of-care echo

c. Glycocalyx disruption — give albumin 20% to restore oncotic pressure

d. Electrolyte shift causing dysrhythmia — adjust dialysate potassium

Q4. A patient with bilateral confluent B-lines, SpO₂ 88% on FiO₂ 0.6, biventricular dysfunction, and MAP 60 mmHg on noradrenaline 0.25 mcg/kg/min is started on CRRT. The team targets 2 L fluid removal in the first 8 hours. Which approach is most physiologically appropriate?

a. Proceed with 2 L in 8 hours — severity of pulmonary congestion justifies urgency

b. Start with no net ultrafiltration; stabilise haemodynamics first, then titrate removal incrementally

c. Increase the target to 3 L in 8 hours — biventricular dysfunction demands faster offloading

d. Defer ultrafiltration entirely until vasopressors are weaned

Q5. The ICU team debates whether to use CRRT or intermittent haemodialysis (IHD) in a vasopressor-dependent, fluid-overloaded patient. The registrar argues: “Trials show no mortality difference, so logistics should decide.” What is the most accurate critique?

a. Correct — equivalent trial outcomes make logistical preference clinically defensible

b. Incorrect — modality determines how haemodynamic physiology interacts with fluid removal; continuous therapy is physiologically appropriate in haemodynamically unstable patients

c. Incorrect — IHD is preferred because higher solute clearance efficiency outweighs haemodynamic concerns

d. Irrelevant — haemodynamic responses to ultrafiltration are driven by vasopressor dose, not modality

Q6. A vasopressor-dependent patient on CRRT at 150 mL/hr undergoes serial point-of-care echocardiography. At 3 hours, new septal shift and reduced TAPSE are noted. Blood pressure remains at MAP 65 mmHg. What is the most appropriate next step?

a. Continue current rate — intervene only when MAP falls below target

b. Reduce or pause ultrafiltration — worsening RV function signals early intolerance preceding overt hypotension

c. Increase vasopressor dose before reducing ultrafiltration rate

d. Administer a fluid bolus to restore RV preload

Q7. A haemodynamically fragile patient with AKI has pH 7.18, bicarbonate 12 mmol/L, K⁺ 6.4 mmol/L, MAP 60 mmHg on noradrenaline 0.3 mcg/kg/min, and +10 L fluid balance. CRRT is initiated. What is the most appropriate initial prescription priority?

a. Maximise ultrafiltration rate — address fluid overload first, metabolic correction will follow passively

b. Prioritise solute clearance; minimise or defer net ultrafiltration until partial metabolic stabilisation is achieved

c. Target rapid correction of both fluid and metabolic derangements simultaneously with high-volume haemofiltration

d. Defer CRRT until MAP exceeds 65 mmHg on current vasopressor support

Q8. A 64-year-old woman recovers from septic shock requiring 9 days of CRRT. Creatinine has improved from a peak of 480 to 210 µmol/L. A colleague argues CRRT duration makes dialysis dependence likely. Which statement best reflects the determinants of renal recovery?

a. CRRT beyond 7 days independently predicts dialysis dependence; earlier IHD transition may have helped

b. Recovery is primarily jeopardised by secondary events — recurrent hypotension, excessive ultrafiltration, and persistent venous congestion — rather than modality or duration

c. Age over 60 and peak creatinine above 400 µmol/L are reliable predictors of dialysis dependence regardless of ICU management

d. IHD confers superior long-term renal recovery due to more efficient solute clearance

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