Mechanisms of Diuretic Resistance in Heart Failure, Aim 3

Briefly, the protocol will begin with pre-study determination of diuretic response at the screening visit via administration of 10 mg IV bumetanide and measuring peak FENa. Participants may proceed to the subsequent study procedures. Participants will begin a study diet provided by the metabolic kitchen five days prior to Day 0. Beginning on day 0, participants will take either NH4Cl or placebo 75mmol twice daily. On day 1, the participant will return to study site and receives the first dose of their twice daily study medication as well as their regular loop diuretic dose given as IV bumetanide, followed by completion of the biospecimen collection protocol and a 24-hour urine collection. On day 2, participants will receive a full 150mmol dose at Hr-2 (75 mmol if pH\<7.3-7.25, no NH4Cl if pH\<7.25). 2 hours after the IV bumetanide is given, 100mmol of sodium bicarbonate in 750ml of 5% dextrose will be administered to participants that received NH4Cl or 750 ml of lactated Ringer's solution to participants that received placebo (provided blinded by the investigational pharmacy). After this visit, a washout period will be conducted before the above procedures are repeated with the alternate study medication. The washout period will be a minimum of 10 days and a maximum of 28 days. Five days prior to the end of the washout period, the participant will resume the study diet until the end of the study on day 18. On day 16, the participant will be crossed over to the alternate therapy (NH4Cl or placebo). On day 17, the participant will complete the same procedures as day 1 of the first arm. On day 18, the participant will complete the same procedures as day 2 of the first arm. The administration of Bendroflumethiazide will occur under a separate ancillary protocol