Acute Heart Failure: IV Furosemide Dosing, Hypertensive AHF, and Initiation of ARNI/MRA

The ESC Hemodynamic Profile Framework (use this first)

1. How Much IV Furosemide Initially?

The DOSE Trial Evidence

• Low dose: IV furosemide equal to their total daily oral dose
• High dose: IV furosemide at 2.5× their total daily oral dose
• Delivered as either IV bolus every 12h OR continuous infusion

• No significant difference in the primary endpoint (patient-reported symptoms) or creatinine change at 72h
• A trend toward greater symptom improvement with high-dose
• High-dose showed more favorable secondary outcomes: lower BNP, higher diuresis, better dyspnea relief
• No significant difference between bolus and continuous infusion overall

Note: Oral furosemide bioavailability is ~50%, so 40 mg oral ≈ 20 mg IV. When converting, the IV equivalent of the oral dose is half; "2.5×" in DOSE was 2.5× the oral dose given IV.

Continuous Infusion vs. Bolus

Endpoint of Diuresis

2. Special Considerations in Hypertensive AHF

• IV nitroglycerin: Drug of choice. Primarily a venodilator, lowers preload, relieves pulmonary congestion rapidly. Especially good when hypertension + coronary ischemia + severe MR is present. Start at 10-20 mcg/min, titrate up by 10-20 mcg/min every 3-5 min to BP target. Main limitation: rapid tachyphylaxis.
• IV sodium nitroprusside: Balanced veno- and arterio-dilator, powerful. Use in markedly congested patients with severe hypertension or severe MR. Limited by risk of systemic hypotension and thiocyanate toxicity (especially with renal impairment).
• Furosemide: Used together with vasodilators but at lower doses in pure hypertensive AHF, since total body sodium/water excess may be modest. Avoid aggressive diuresis that may cause hypovolemia after vasodilators work.

As Fuster's The Heart notes: "Patients with hypertension, coronary ischemia, or severe mitral regurgitation are considered good candidates for nitroglycerin therapy." - Fuster and Hurst's The Heart, 15th Ed.

3. How to Continue Furosemide (Titration Strategy)

1. First 6 hours: Assess urine output. If < 100-150 mL/h or total < 500 mL in 2h, double the IV dose.
2. Refractory to loop diuretic: Add sequential nephron blockade:
   • Oral metolazone 2.5-5 mg once daily (30-60 min before furosemide) - thiazide synergy
   • OR IV chlorothiazide 250-500 mg
   • These block distal tubule NaCl reabsorption, overcoming loop diuretic resistance, but watch for severe hypokalemia
3. Ongoing: Once adequate diuresis is established and patient is improving, transition to oral furosemide (double the effective IV dose as a rough starting point, given the 50% bioavailability).
4. MRA augmentation: Spironolactone (or eplerenone) can augment diuresis by blocking aldosterone-driven sodium retention at the collecting duct, and also provides long-term mortality benefit in HFrEF (Fuster & Hurst, 15th Ed.).
5. Monitoring: BMP (Na, K, Cr, BUN) every 12-24h. Mild creatinine rise (≤0.3 mg/dL) during decongestion is acceptable and should not prompt diuretic withdrawal if the patient remains volume overloaded.

4. Should You Start ARNI (Sacubitril/Valsartan) During Hospitalization?

• SBP ≥ 100 mmHg (stable)
• Off IV diuretics (or on minimal oral)
• eGFR > 30 mL/min/1.73m² (use caution with lower values)
• K⁺ < 5.4 mEq/L
• No ACE inhibitor within 36 hours (risk of angioedema)
• Starting dose: Sacubitril/valsartan 24/26 mg twice daily, titrate up at 2-4 weeks

5. Spironolactone vs. Finerenone: Can They Be Started Initially?

Spironolactone (Steroidal MRA)

• Do NOT initiate during the acute congested phase if: K⁺ ≥ 5.0 mEq/L, eGFR < 30, or hemodynamically unstable
• If already on chronic spironolactone for HFrEF, continue it (do not stop unless hyperkalemia or AKI)
• Can be added during admission once diuresis is established, K⁺ is normal, and creatinine is stable - helps augment diuresis AND starts the mortality-benefit GDMT
• Starting dose: 12.5-25 mg/day (upward titration in outpatient setting)
• Evidence: RALES (HFrEF, EF ≤ 35%), EMPHASIS-HF (eplerenone, NYHA II HFrEF) - both showed survival benefit in chronic HFrEF

Finerenone (Non-Steroidal MRA)

• FINEARTS-HF (2024): Finerenone reduced HF hospitalizations and CV death in HFmrEF/HFpEF (EF ≥ 40%)
• In hypertensive HF with preserved EF, finerenone is now a rational option
• NOT a first-line agent for acute decompensation - initiate after stabilization
• Starting dose: 10 mg/day (if eGFR 25-60) or 20 mg/day (if eGFR ≥ 60), with K⁺ < 5.0

Spironolactone vs. Finerenone - Head-to-Head Considerations

• HFrEF (EF < 40%): Start spironolactone 25 mg once stable (K⁺ normal, creatinine stable)
• HFmrEF/HFpEF (EF ≥ 40-50%) - especially common in hypertensive HF: Consider finerenone 10-20 mg after stabilization
• Neither should be given in the first few hours of acute decompensation if K⁺ is borderline or renal function is impaired

Summary Flowchart for Hypertensive AHF

Hypertensive AHF (Wet + Warm, BP elevated)
├── Immediate: IV nitroglycerin (10-20 mcg/min, titrate up)
├── + IV furosemide: 40-80 mg bolus (or 2.5× oral dose)
├── O₂/CPAP if pulmonary edema
│
├── Reassess at 2-6h:
│   ├── Adequate diuresis + BP improving → titrate down vasodilator
│   ├── Inadequate diuresis → double furosemide dose / add metolazone
│   └── Persistent hypertension → continue nitro, consider nitroprusside
│
├── Once stabilized (SBP ≥ 100, off IV drugs, K⁺ OK):
│   ├── Start sacubitril/valsartan 24/26 mg BD (PIONEER-HF)
│   ├── Add spironolactone 25 mg (HFrEF) OR finerenone 10-20 mg (HFpEF)
│   ├── Transition to oral furosemide
│   └── Add beta-blocker if not already on one (after euvolemia)
│
└── Discharge: Optimize all 4 pillars of GDMT

GTN (Glyceryl Trinitrate) via Syringe Pump in Hypertensive AHF

Step 1 - Preparation (The Standard Formula)

50 mg GTN in 50 mL = 1 mg/mL = 1000 mcg/mL

• Draw up the full 50 mL of GTN 1 mg/mL into a 50 mL syringe (no further dilution needed with this concentration)
• Most manufacturers supply GTN as a ready-mixed 50 mg/50 mL vial - load it directly into the syringe pump
• Critical: Use rigid plastic syringes (BD Plastipak, Gillette Sabre) and polyethylene tubing - GTN is absorbed by PVC bags and tubing, causing significant drug loss. Never use standard PVC infusion sets.
• Discard after 24 hours

Step 2 - The Rate-to-Dose Conversion Table

Step 3 - Starting and Titrating (Hypertensive AHF Protocol)

• Record baseline BP and HR
• Ensure IV access is patent
• Check: no PDE5 inhibitor (sildenafil, tadalafil) in last 24-48h - severe hypotension risk
• Check: SBP > 100 mmHg (ideally ≥ 110 mmHg)

1. Start at 10-20 mcg/min (0.6-1.2 mL/hr) in AHF/pulmonary edema - you can be bolder than in angina given the urgency. Some protocols for flash pulmonary edema start at 20 mcg/min immediately.
2. Titrate up every 3-5 minutes by 10 mcg/min increments, reassessing BP and symptoms each time.
3. If no BP response at 20 mcg/min - increase by 10-20 mcg/min every 3-5 minutes.
4. Once partial response (BP beginning to fall, dyspnea easing) - slow increments, lengthen intervals to 15 min.
5. Target: SBP 100-120 mmHg (do not drop below 90-100 mmHg systolic). In hypertensive AHF, aim for SBP reduction by ~20-25% in the first hour.
6. Maximum dose: 200 mcg/min (some protocols allow up to 400 mcg/min in refractory cases with close hemodynamic monitoring).

Step 4 - Monitoring While on GTN Infusion

• SBP < 90-100 mmHg
• HR > 110 bpm (reflex tachycardia - consider if adequate filling)
• Severe headache (use paracetamol, do not stop unless haemodynamically unstable)
• Dizziness/pre-syncope

Step 5 - Tachyphylaxis: The Key Practical Problem

• If response is diminishing after 12-16h, do not just keep increasing the dose
• Consider switching to IV sodium nitroprusside for sustained afterload reduction
• Overlap with oral long-acting nitrate (isosorbide mononitrate) before weaning GTN
• Provide a "nitrate-free interval" if transitioning to oral/transdermal nitrates
• Some clinicians use N-acetylcysteine (sulfhydryl donor) to partly offset tolerance - evidence is limited but used in refractory cases

Step 6 - Weaning GTN

• SBP stable in target range
• Pulmonary edema/congestion improving (dyspnea reduced, SpO₂ improved, reduced crepitations)
• Patient tolerating oral medications

Special Notes for Hypertensive AHF Specifically

• In flash pulmonary edema (sudden onset, SBP > 160): some evidence supports high-dose bolus GTN (400-800 mcg IV bolus, repeat ×2-3 every 3-5 min) followed by infusion - this can be more effective than starting low and titrating up, because the pulmonary edema needs rapid preload reduction. A case series from PMC supports ultra-high dose GTN (titrating to 200+ mcg/min) in refractory hypertensive AHF.
• Combine with IV furosemide 40-80 mg simultaneously - GTN handles the preload/afterload acutely while furosemide handles the volume over 30-60 min.
• If BP is severely elevated (SBP > 180-200 mmHg) and GTN alone is insufficient, switch to sodium nitroprusside which provides more powerful and reliable afterload reduction.
• CPAP/NIV is synergistic - reduces work of breathing, decreases preload, and may let you use lower GTN doses.

Quick-Reference Card for the Bedside

GTN Syringe Pump - Hypertensive AHF

Preparation: 50 mg GTN in 50 mL = 1 mg/mL
Syringe: Rigid plastic only (NO PVC)
Tubing: Polyethylene (NO PVC giving sets)

Start:  10-20 mcg/min → 0.6-1.2 mL/hr
Titrate: ↑ by 10 mcg/min every 3-5 min
Target SBP: 100-120 mmHg
Max: 200 mcg/min (= 12 mL/hr)

STOP if: SBP < 90 mmHg | HR > 110
CHECK: No PDE5 inhibitor in last 48h
TOLERANCE: Develops within 12-24h