Chapter Nineteen: Metabolic Acidosis, part 2

ReferencesChapter 19, Part 12Metabolic acidosis  June 14, 2023ReferencesChapter 19, Part 2Roger mentioned MELAS syndrome MELAS syndrome: Clinical manifestations, pathogenesis, and treatment optionsJosh mentioned this blog on lactate- Understanding lactate in sepsis & Using it to our advantageWe discussed the Warburg effect The Warburg Effect: How Does it Benefit Cancer Cells? - PMC and here’s a case from skeleton key- Skeleton Key Group Case #28: Mysterious Acidosis in Cancer - Renal Fellow NetworkOtto Warburg won the Nobel Prize in Physiology and Medicine in 1931 for describing how animal tumors produce large quantities of lactic acid (Wikipedia)Joel calls it the Lactate saline reflex, but the accepted term of art is Lacto-Bolo reflex The origins of the Lacto-Bolo reflex: the mythology of lactate in sepsisBuffer agents do not reverse intramyocardial acidosis during cardiac resuscitation.Josh mentioned this article the BICAR-ICU Sodium bicarbonate therapy for patients with severe metabolic acidaemia in the intensive care unit (BICAR-ICU): a multicentre, open-label, randomised controlled, phase 3 trial - The LancetRoger shared 3 quotes to make the point that there has been little movement in our knowledge the past 40 years:Bicarbonate does not improve hemodynamics in critically ill patients who have lactic acidosis. A prospective, controlled clinical study from Cooper in the AnnalsLactic Acidosis and Bicarbonate Therapy | Annals of Internal Medicine from Robert HollanderLactic acidosis from Nick MadiasJosh mentioned the use of sodium bicarbonate for CKD Eubicarbonatemic Hydrogen Ion Retention and CKD Progression - Kidney Medicine  (Madias) Bicarbonate therapy for prevention of chronic kidney disease progression (from Wesson),  Sodium Bicarbonate Prescription and Extracellular Volume Increase: Real‐world Data Results from the AlcalUN StudyAmy’s VoG on metabolic acidosis/KDIGO guidelinesVery nice JASN review that describes the mechanisms of how metabolic acidosis leads to CKD progressionFirst description by THE Dr. Bright1930 Lancet description of benefit2009 RCT that the 2012 KDIGO guidelines sort of based their 2b recommendations off of2020 BiCARB Study2021 META AnalysisWe discussed methanol toxicity : Case Study: Methanol Poisoning from Adulterated Liquor | Food Safety, Acute methyl alcohol poisoning: a review based on experiences in an outbreak of 323 cases and josh poking at the osmolar gap: PulmCrit- Toxicology dogmalysis: the osmolal gap and shared these guidelines: METHANOL | extrip-workgroup and Roger loves this: Urine fluorescence using a Wood's lamp to detect the antifreeze additive sodium fluorescein: a qualitative adjunctive test in suspected ethylene glycol ingestionsFrom China to Panama, a Trail of Poisoned Medicine - The New York Times (diethylene glycol) . The Accidental Poison That Founded the Modern FDA - The AtlanticOutline: Chapter 19 Metabolic AcidosisEtiologies and DiagnosisLactic AcidosisPyruvate → lactate (LDH; NADH → NAD+)Normal production: 15–20 mmol/kg/dayMetabolized in liver/kidney → pyruvate → glucose or TCANormal lactate: 0.5–1.5 mmol/L; acidosis if > 4–5 mmol/LCauses:↑ production: hypoxia, redox imbalance, seizures, exercise↓ utilization: shock, hepatic hypoperfusionMalignancy, alcoholism, antiretroviralsD-lactic acidosisShort bowel/jejunal bypassGlucose → D-lactate (not metabolized by LDH)Symptoms: confusion, ataxia, slurred speechSpecial assay neededTx: bicarb, oral antibioticsTreatmentUnderlying causeBicarb controversial: may worsen intracellular acidosis, overshoot alkalosis, ↑ lactateTarget pH > 7.1; prefer mixed venous pH/pCO2Ketoacidosis (Chapter 25 elaborates)FFA → TG, CO2, H2O, ketones (acetoacetate, BHB)Requires:↑ lipolysis (↓ insulin)Hepatic preference for ketogenesisCauses:DKA (glucose > 400)Fasting ketosis (mild)Alcoholic ketoacidosisPoor intake + EtOH → ↓ gluconeogenesis, ↑ lipolysisMixed acid-base (vomiting, hepatic failure, NAGMA)Congenital organic acidemias, salicylatesDiagnosis:AG, osmolar gap (acetone, glycerol)Ketones: nitroprusside only detects acetone/acetoacetateBHB can be 90% of total (false negative)Captopril → false positiveTreatment:Insulin +/- glucoseRenal Failure↓ excretion of daily acid loadGFR < 40–50 → ↓ ammonium/TA excretionBone buffering stabilizes HCO3 at 12–20 mEq/LSecondary hyperparathyroidism helps with phosphate bufferingAlkali therapy controversial in adultsIngestionsSalicylatesSymptoms at >40–50 mg/dLEarly: respiratory alkalosis → Later: metabolic acidosisTreatment: bicarb, dialysis (>80 mg/dL or coma)MethanolMetabolized to formic acid → retinal toxicityOsmolar gap elevatedTx: bicarb, ethanol/fomepizole, dialysisEthylene glycol→ glycolic/oxalic acid → renal failureSame treatment + thiamine/pyridoxineOtherToluene, sulfur, chlorine gas, hyperalimentation (arginine, lysine)GI Bicarbonate LossDiarrhea, bile/pancreatic drainage → loss of alkaline fluidsUreterosigmoidostomy → Cl-/HCO3- exchange in colonCholestyramine → Cl- for HCO3-