ABG’s

Indications Technique Complications Analysis Summary

Indications Respiratory illness Critical illness Unwell patients Other circumstances

Technique Right pt? Any artery : commonly radial Allens test Preparation pre test Monitoring Caution Don’t loose it Arterial lines and monitoring of IABP

Complications Bleeding Bruising Thrombosis AV fistula Complication of arterial lines

Analysis pH PaCO2 PaO2 HCO3 O2 sats Electrolytes Lactate Hb, Meth Hb, Carboxy Hb

Normal values pH: 7.35 – 7.45 PaCO2: 4.7 – 6 kPa PaO2: 11 – 13 kPa HCO3: 22 – 26 mEq/L Lactate: <2 O2 sats: >96%

Step wise analysis What is the pH? Normal: 7.35 – 7.45 Acidosis: < 7.35( more acid ie H+) Alkalosis: > 7.45( less acid ie H+)

What is the PaCO2 Normal: 4.7 – 6.0 Hypercapnoea: > 6 ( more CO2) Hypocapnoea: < 4.7( less CO2)

What is PaO2 Normal? High: > 13 on room air Low: < 11 on room air

What is the HCO3 Normal: 22 – 26 Low: < 22 High: > 26

Is it metabolic or respiratory? AcidosisRespiratorypHPaCO2 AcidosisMetabolicpHPaCO2 AlkalosisRespiratorypHPaCO2 AlkalosisMetabolicpHPaCO2

Is there compensation? Respiratory pathology the compensation is renal Renal pathology the compensation is respiratory

Is there compensation? DisorderpHPrimary problemCompensation Metabolic acidosis in HCO3 in PaCO2 Metabolic alkalosis in HCO3 in PaCO2 Respiratory acidosis in PaCO2 in HCO3 Respiratory alkalosis in PaCO2 in HCO3

Anion gap Na – ( Cl+HCO3) Normal 12 Metabolic acidosis with normal anion gap Metabolic acidosis with increased anion gap

Respiratory acidosis Airway obstruction - Upper - Lower: COPD, asthma CNS depression Sleep disordered breathing Neuromuscular impairment Ventilatory restriction Increased CO2 production: shivering, rigors, seizures, malignant hyperthermia, hypermetabolism Incorrect mechanical ventilation settings

Respiratory alkalosis CNS stimulation: fever, pain, fear, anxiety, CVA, cerebral edema, CNS infection Hypoxemia or hypoxia: lung disease, profound anemia, low FiO2 Stimulation of chest receptors: pulmonary edema, pleural effusion, pneumonia, pneumothorax, pulmonary embolus Drugs, hormones: salicylates, catecholamines, medroxyprogesterone, progestins Pregnancy, liver disease, sepsis, hyperthyroidism Incorrect mechanical ventilation settings

Metabolic alkalosis Hypovolemia with Cl- depletion GI loss of H+Vomiting, gastric suction, villous adenoma, diarrhea with chloride-rich fluid Renal loss H+Loop and thiazide diuretics Renal loss of H+: edematous states (heart failure, cirrhosis, nephrotic syndrome), hyperaldosteronism, hypercortisolism, excess ACTH, exogenous steroids, severe hypokalemia bicarbonate administration

Metabolic acidosis with elevated anion gap M U D P I L E S

Metabolic acidosis with normal anion gap GI loss of HCO 3 -Diarrhoea, ileostomy, proximal colostomy Renal loss of HCO 3 -proximal RTA carbonic anhydrase inhibitor (acetazolamide) Renal tubular disease, ATN, Chronic renal disease, Distal RTA, NaCl infusion

Metabolic acidosis with elevated anion gap Methanol intoxication Uremia Diabetic ketoacidosis, alcoholic ketoacidosis, starvation ketoacidosis Paraldehyde toxicity Isoniazid Lactic acidosis Ethanol Salicylate intoxication

ABG’s pH:7.38 PaCO28.0 PaO28.0 HCO332 Sats88 O22L Lac1.5 Na138 Cl99

What is the abnormality? What might this patient have?

ABG’s pH:7.50 PaCO23.0 PaO28.0 HCO322 Sats88 O2Room air Lac1.5 Na138 Cl99

What is the abnormality? What might this patient have?

ABG’s pH:7.50 PaCO23.0 PaO213.0 HCO323 Sats98 O2Room air Lac1.5 Na138 Cl99

What is the abnormality? What might this patient have?

ABG’s pH:7.20 PaCO212 PaO28.0 HCO330 Sats88 O22L Lac1.5 Na138 Cl99

What is the abnormality? What might this patient have?

ABG’s pH:7.10 PaCO23.0 PaO212 HCO310 Sats96 O22L Lac1.5 Na138 Cl99

What is the abnormality? What might this patient have? What other blood tests may you want to do?

ABG’s pH:7.10 PaCO26.5 PaO29.0 HCO315 Sats96 O22L Lac4.5 Na148 Cl94

Summary Systematic approach in analysis of ABG’s Can help you in difficult situations Always co relate clinically Should not be abused Get slick at it

Thanks