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Dr. Ajith Kumar J MD
Dept. of Emergency Medicne
Travancore Medicity, Kollam
India
editor
Lactic acid is the normal endpoint of the anaerobic breakdown of glucose in the tissues.
It can be either
L-lactate
Commonly measured level in the laboratory & by product of human metabolism.
Represents increased anaerobic metabolism due to tissue hypoperfusion.
D-lactate
Byproduct of bacterial metabolism
Short-gut syndrome or in those with a history of gastric bypass or small-bowel resection
Normal value
0.5 – 1.0 mmol/L
Critical illness : < 2.0 mmol/L
Hyperlactatemia V/S Lactic Acidosis
Hyperlactatemia is defined as a persistent, mild to moderate (2-4 mmol/L) increase in blood lactate concentration without metabolic acidosis.
Lactic acidosis is characterized by persistently increased blood lactate levels (usually >5 mmol/L) in association with metabolic acidosis.
Cohen & Woods Classification
TYPE A :
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Type B1: Systemic disease, such as renal and hepatic failure, diabetes and malignancy. |
Type B2 : Drugs and toxins like biguanides, alcohols, iron, isoniazid, zidovudine, and salicylates. |
Type B3 : Due to inborn errors of metabolism like G6PD , Fructose1,6 diphosphatase deficiency, Pyruvate carboxylase deficiency.
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ETIOLOGY
Circulatory shock
Increase in lactate level indicates impaired oxygenation status.
Blood lactate levels are directly proportional to mortality rate.
Sepsis : They can lead to either
Stress hyperlactemia : It characterized by Lactate levels of 2 – 5 mEq/L;Normal lactate to pyruvate ratio & normal blood pH. It is due to hypermetabolism without impaired oxygen utilization.
Cytopathic hypoxia : It is characterized by elevated levels of lactate, increased lactate pyruvate ratio ,reduced blood pH, Impaired oxygen utilization.
LACTATE CLERANCE
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Thiamine deficiency
Co factor for pyruvate dehydrogenase enzyme that initiates pyruvate oxidation in the mitochondria.
Drugs
Drugs like nucleoside reverse transcriptase inhibitor, acetominophen, epinephrine, metformin, propofol & nitroprusside.
Propylene Glycol
It is an alcohol agent used to enhance the water solubility of many hydrophobic I.V. Medication.
Lorazepam, diazepam, esmolol, nitroglycerin & phenytoin.
Agitation, coma, seizures, tachycardia, hypotension & hyperlactemia.
Suspect : Unexplained hyperlactatemia
More common in persons receiving infusion of lorazepam & diazepam.
Midazolam doesnot have propylene glycol.
Seizures:Increased lactate production
Hepatic insufficiency:Reduced lactate clearance
Acute asthma: enhanced production by respiratory muscles.
Clinical Signs
Hypotension
Alteration in sensorium
Peripheral vasoconstriction
Oliguria
Kussmaul hyperventilation
Fever or hypothermia
Diagnosis
Blood lactate levels
High anion gap acidosis
MANAGEMENT
GENERAL PRINCIPLES
CAB
Secure an IV line
Early goal directed therapy in sepsis
Fluid resuscitation if signs of shock.
Antibiotics
Drainage
Bicarbonate Therapy
It is the standard buffer used for lactic acidosis . But has limited success. It is used in setting of severe metabolic acidosis (pH <7.1). HCO3 deficit = 0.6 * wt * (Desired HCO3 – Measured HCO3). One half of the estimated deficit is corrected.
ADVERSE EFFECTS
Paradoxical worsening of intracellular acidosis.
It can create extracellular alkalosis that will shift the oxyhemoglobin saturation curve and inhibit oxygen release.
Hypernatremia and hyperosmolarity
Hypocalcemia
It can be over come by giving slow infusions ,increasing minute volume in patients on ventilator ,correcting hypocalcemia
Carbicarb
It is a buffer solution 1:1 sodium bicarbonate & disodium bicarbonate. Produces less bicarbonate and a much lower PCO2. Has some theoretical advantage but lacks evidence.
Dichloro Acetate
Potent stimulus of pyruvate dehydrogenase. It is a rate limiting enzyme for aerobic oxidation of glucose, pyruvate & lactic acid. Inhibits glycolysis & has positive inotropic effects.
Dialysis
Dialysis may be done in severe lactic acidosis; occurs in combination with renal failure and cardiac failure.
Thiamine
Thiamine deficiency may be associated with cardiovascular compromise and lactic acidosis. Thiamine repletion given as 50-100 mg intravenously [IV] followed by 50 mg/d orally [PO] for 1-2 wk.
Tris Hydroxymethyl Aminomethane (THAM)
It is a weak alkali and theoretical has the advantage over bicarbonate as it produces less carbon dioxide.Clinical trials do not prove THAM to be more effective.
Other agents : Coenzyme Q, l-carnitine, and riboflavin have been used to treat lactic acidosis due to antiretroviral therapy. These agents has no definitive demonstration of efficacy.
Updated on : 15/1/2015
Reference
Tinitinalli
The ICU; Paul marino
Early lactate clearance is associated with improved outcome in severe sepsis and septic shock. By Bryant Ngyuen et al. Critical Care Medicine 2004.
Lactate Clerance vs Central Venous Oxygen Saturation as Goals of Early Sepsis Therapy. A Randomized Clinical Trial. By Alan E Jones. JAMA. 2010
Video : Lactic Acidosis ; Courtsey : AETCM
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emmedonline
Dr. Ajith Kumar J MD
Dept. of Emergency Medicne
Travancore Medicity, Kollam
India
editor