METABOLIC ACIDOSIS                        <A-RespAc.TXT>
                        ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ

þ Lactic Acidosis

Recent changes in the management of trauma and sepsis emphasize the
importance of lactic acidosis in disease prognosis. These authors
evaluated the anion gap as a screening test for lactic acidosis in the
emergency department setting. In a retrospective cohort study, they
analyzed serum electrolyte and lactic acid levels in all patients who
had lactate testing for any reason at a single ED over 7 months.
Patients were excluded if they had alcoholic or diabetic ketoacidosis,
suspected toxin ingestion, or blood samples drawn for the two tests
more than 60 minutes apart.

Among 303 patients, the incidence of lactic acidosis (serum lactate
level >2.5 mmol/L) was 16.2%. At a normal value of <12 mEq/L, the
anion gap had a sensitivity of 58.2%, a specificity of 81.0%, and a
negative predictive value (NPV) of 89.7% for detecting lactic
acidosis. Lowering the cutoff to <6 mEq/L yielded a sensitivity of
93.2%, a specificity of 17.3%, and an NPV of 91.8%. The authors note
that the anion gap at neither cutoff value is sufficiently reliable
for eliminating the possibility of lactic acidosis.
[Adams BD et al. The anion gap does not accurately screen for lactic
acidosis in emergency department patients. Emerg Med J 2006 Mar;
23:179-82.]


Renal Tubular Acidosis  <A-RTA.TXT>
Pseudo-acidosis         <L-HCO3.TXT>
D-Lactic Acidosis       <ShortGut.TXT -acidosis>

First question:  is it adequately compensated?
Use Winter's Formula:  pH = 1.5 ([HCO3-] + 8) +- 2  for good compensation
except:  lactic acidosis may have overcompensation due to CNS effects.

2. Anion Gap vs. Non-anion-gap (Hyperchloremic):
   i. [Na+] - ([Cl-] + [HCO3-]) >> 12  is anion gap acidosis
   ii. [Na+] - ([Cl-] + [HCO3-]) ~= 12  is hyperchloremic acidosis
   iii.  in anion gap should be same as  in HCO3-, or has BOTH anion-
      gap and non-anion-gap metabolic acidoses.
3. High Anion Gap Metabolic Acidoses
   i. Mnemonics:
     MUDPILES:
      M- methanol
      U- uremia
      D- diabetic ketoacidosis
      P- paraldehyde
      I- iron/isoniazid (INH)
      L- lactic acidosis
      E- ethanol
      S- salicylates (and acetaminophen)
     KUSMAL:
      K- ketoacidosis
      U- uremia
      S- salicylates
      M- methanol (and ethelyne glycol, pareldehyde)
      A- alcohol (EtOH)
      L- lactic acidosis
         can come from metformin (e.g., Glucophage) <d-dm.txt -acidosis>
4. Normal Anion Gap (Hyperchloremic) Metabolic Acidoses
   i. high K+ vs. low K+
      a. high K+
         1. hyperal and increased amino acid catabolism
         2. post-hypocapnic (it takes a while for the HCO3- to rise)
         3. dilutional
         4. hypoaldo (either from low renin or adrenal dysfunction)
         5. NH4Cl, CaCl2, lysine, or arginine (effectively adds HCl)
      b. low K+
         1. GI-- diarrhea, fistulas (K+ loss and high aldo)
         2. GU-- surgical ureteral conduits
         3. RTA-- see separate section.
   ii. Urine pH < 5.0 or > 5.5
      a. urine pH < 5.0-- suggests interstitial nephritis and a defect
         in NH4+ and NH3 buffering
      b. urine pH > 5.5-- suggests RTA
  Topamax (topiramate) is known to cause bicarb loss and metabolic acidosis,
  dose-dependent effect.