A 54-year-old male (weight 85 kg, height 175 cm) with a medical history of Type 2 diabetes mellitus, essential hypertension, chronic kidney disease (Stage 5), ischaemic heart disease, and heart failure with reduced ejection fraction (HFrEF) was admitted to the ICU with septic shock secondary to pneumonia. Currently he is on broad-spectrum antibiotics, vasopressors, and mechanical ventilation. His hemodynamic parameters and lab investigations are as follows: Hemodynamics: Blood Pressure: 90/50 mmHg (on norepinephrine at 0.1 mcg/kg/min) Heart Rate: 110 bpm Central Venous Pressure (CVP): 12 mmHg Cardiac Output: 4 L/min Urine output of 20 to 25 ml/hr Labs: Haemoglobin: 9.5 g/dL WBC: 15,000 /µL Platelets: 120,000 /µL Serum creatinine: 6.5 mg/dL Blood Urea Nitrogen (BUN): 70 mg/dL Potassium: 5.8 mEq/L Arterial Blood Gas (ABG): pH 7.25, PaCO2 30 mmHg, PaO2 75 mmHg, HCO3- 16 mEq/L He was initiated on intermittent hemodialysis (IHD) for acute kidney injury and severe metabolic acidosis. Initial settings: Blood flow rate 300 mL/min, Dialysate flow rate 500 mL/min, Ultrafiltration goal 2 litres over 4 hours. 1 hour into dialysis, his blood pressure dropped to 80/45 mmHg, and heart rate 120 bpm. His norepinephrine infusion rate increased to 0.2 mcg/kg/min; 500 mL of normal saline bolus was administered. A review of the dialysis solution composition shows the following: Base: bicarbonate 25 mM Sodium: 130 mM Potassium: 3.5 mM Calcium: 1.5 mM (3.0 mEq/L) Magnesium: 0.375 mM (0.75 mEq/L) Dextrose: 5.5 mM (100 mg/dL) Phosphate: none Dialysis solution temperature: 33°C
Wrong Answer: A. Employing a high concentration of sodium ions in the dialysate (>145 mmol/l) is effective in preventing the movement of solutes from the extracellular to the intracellular compartment. This, in turn, helps to reduce the occurrence of hypovolemia generated by renal replacement therapy (RRT). Therefore, it is advisable to set the dialysate sodium concentration to a value higher than 145 mmol/L. This will help to improve the hemodynamic tolerance.
Wrong Answer: B. Reducing the ultrafiltration goal from 2 litres to 1 litre will help to improve the hemodynamic tolerance.
Wrong Answer: C. Utilising either cool dialysate or isothermal dialysis (with the dialysate temperature set at 35 °C) will also help to improve the hemodynamic tolerance.
Right Answer:D. Utilising a modest initial blood flow rate of less than 250 ml/min. In this case, increasing the dialysate blood flow from 300 ml/min to 350 ml/min will worsen the hemodyanmic tolerance. Therefore, this change of increasing the dialysate blood flow is not recommended. Strategies to enhance haemodynamic stability during IHD comprise: i.Utilising either cool dialysate or isothermal dialysis (with the dialysate temperature set at 35 °C) ii.Employing a high concentration of sodium ions in the dialysate (>145 mmol/l) is effective in preventing the movement of solutes from the extracellular to the intracellular compartment. This, in turn, helps to reduce the occurrence of hypovolemia generated by renal replacement therapy (RRT). Therefore, it is advisable to set the dialysate sodium concentration to a value higher than 145 mmol/L. iii.Utilising a modest initial blood flow rate of less than 250 ml/min. iv.Utilising biofeedback-enabled equipment equipped with ultrafiltration calibrated to relative blood volume v.Avoiding drugs that cause vasodilatation vi.Increasing the duration of the dialysis sessions vii.Increasing the frequency of dialysis sessions
