Metabolic Acidosis PDF

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Metabolic Acidosis...

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Metabolic Acidosis Monday, 28 October 2019

12:01

Describe the importance of detecting metabolic acidosis Metabolic Acidosis Low arterial blood pH with a reduced serum HCO3- concentration Normal range is pH 7.35 - 7.45, 24 - 28mmol/l HCO3-

Respiratory acidosis is generated by driving the equation to the left Metabolic acidosis is generated by driving the equation to the right Importance of Detection ↓Blood pH = ↑[H+] or ↓[HCO3-] HCO3- is the main buffer of the body, binding excess H+ Acidic milieu associated with a host of significant medical conditions Metabolic acidosis increases mortality Easily identified and potentially correctable

Summarise the causes of metabolic acidosis Causes of Metabolic Acidosis Anion Gap

Plasma is always electroneutral Measured Cations - Na and K Measured Anions - HCO3- and ClIncreased anion gap indicates an increase in the concentration of anions other than Cl- or H Equations Measured Cations + Unmeasured Cations = Measured Anions + Unmeasured Anions Normal Gap Acidosis GI losses - Diarrhoea, surgical drains/fistulae Renal losses - Renal tubular acidosis Cl- has gone up to compensate loss of HCO3GOLDMARK: • Glycols (ethylene, propylene) • Oxyproline • L-lactate • D-lactate • Methanol • Aspirin • Renal failure • Ketoacidosis ○ Result of ketone production, fat metabolism ○ Main causes are diabetes, alcohol and starvation Lactic Acidosis Reduced oxygenated perfusion to tissues leading to anaerobic respiration producing lactic Causes of shock: • Hypovolaemic - Not enough blood circulating (haemorrhage, diarrhoea, vomiting) (IV • Cardiogenic - Pump does not work (Inotropes, diuresis) • Septic - Leaky vessels • Anaphylactic

Interpret an arterial blood gas (ABG) result Arterial Blood Gas pH - 7.35 - 7.45

HCO3-

acid V fluid)

PaCO2 - 4.5 - 6.0kPa PaO2 - 10 - 13kPa HCO3- - 24 - 28mmol/l O2 Sat - 96 - 100% Base Excess - +/-2 mEq/l If base excess low -3 or below, metabolic acidosis Surgical Sieve VITAMIN CDEF: • Vascular • Infection • Trauma • Autoimmune • Metabolic • Iatrogenic • Neoplastic (Cancer) • Congenital • Diabetes • Endocrine • Functional

Describe common clinical scenarios characterised by acidosis

The use of intravenous fluids

Notes Terminology

COPD Patient COPD patients retain CO2, which is acidic Body compensates by retaining HCO3- , so baseline levels are often higher than normal...