2014-18 Excretion of h+ in a intercalated cells Excretion of h* in a intercalated cells Collecting tubule Peritubular capillar Tubular Lumen Collecting tubule Peritubular cap HPO, H oH·CO→3Hco 叶HcO→3Hco3 Can be stimulated by low K Acid-base balance The kidneys must excrete the 50 to 100 meq of noncarbonic acid g The daily acid load is excreted as NH4'and H2(PO)- The daily acid load also cannot be excreted unless virtually all of the Regulation: The extracellular pH Can be independent o serum pH Steps in acid-base diagnosis Henderson-Hasselbalch equation (ABGs)and electrolytes simultaneously Eq1)H++HCO3-<->H2C0O3<->H20+Co2 PC02 Eq2)[H+]=24x or by the Henderson-Hasselbalch equation mare change in ( Ci] with change in( Nal Acidosis: PCO2=1. X HCO3+82014-1-8 3 Tubular Lumen Collecting tubule Peritubular capillary H+ H2O2 OH- + CO2 3HCO3 - CA HPO + H+ 4 2- H2PO4 Cl￾ATPase ATPase H+ K+ Excretion of H+ in a intercalated cells Tubular Lumen Collecting tubule Peritubular capillary H+ H2O2 OH- + CO2 3HCO3 - CA H+ + NH3 NH4 + Cl￾H+ -ATPase NH3 Excretion of H+ in a intercalated cells Can be stimulated by low K Acid-base balance • The kidneys must excrete the 50 to 100 meq of noncarbonic acid generated each day. • The daily acid load is excreted as NH4+ and H2 (PO4 ). • The daily acid load also cannot be excreted unless virtually all of the filtered HCO3- has been reabsorbed, because HCO3- loss in the urine is equivalent to adding H+ ions to the body. • Regulation: – The extracellular pH – the effective circulating volume, – aldosterone, and – the plasma K+ concentration Can be independent of serum pH Steps in acid-base diagnosis • Obtain arterial blood gas (ABGs) and electrolytes simultaneously • Compare [HCO3-]on ABGs and electrolytes to verify accuracy • Calculate anion gap (AG) • Know 4 causes of high AG acidosis – Ketoacidsis – Lactic acid acidosis – Renal failure – Toxins • Know 2 causes of hyperchloremic or nongap acidosis – Bicarbonate loss from GI, – RTA • Estimate compensatory response • Compare ΔAG and ΔHCO3- • Compare change in [Cl] with change in [Na] Henderson-Hasselbalch equation (Eq. 1) H+ + HCO3- <—> H2CO3 <—> H2O + CO2 PCO2 (Eq. 2) [H+] = 24 x ———— [HCO3-] or by the Henderson-Hasselbalch equation [HCO3-] (Eq. 3) pH = 6.10 + log ——————— 0.03 PCO2 Acidosis: PCO2=1.5 X HCO3 + 8