Respiratory Physiology: Arterial Blood Gas Medicine I Delta Transcription Factor ^_^Page 1 Arterial Blood Gas Analysis routine investigation to monitor acid base balanceinvolves puncturing an artery with thin needle and syringe and drawing a small volume of blood only way of getting accurately determining the alveolar-oxygen gradient provides information: oOxygenation oVentilation adequacy oAcid-base levels it also indicates the severity of a condition and help to assess treatment Indications for ABG analysis: 1. Respiratory Failure (acute or chronic) 2. Any severe illnesses w/c may lead to metabolic acidosis ocardiac failure oliver failure orenal failure ohyperglycemic states assoiciated with DM oMulti-organ failure osepsis oburns opoisons/ toxins 3. Ventilated patients 4. Sleep studies 5. Severe unwell patients from any cause -affects prognosis Methods of Arterial Blood Gas 1. Radial Artery Blood Sampling 2. Femoral Artery Blood Sampling 3. Brachial Artery Blood Sampling Procedure of ABG analysis (Radial Artery Sampling) 1. Assess for Artery *Radial Arterymost common site for the direct arterial puncture for ABG analysis easily accessible can be compressed to control bleeding less risk for occlusion *Modified Allen's Test/Allen's Test CONFIMATORYTESTforthecollateral blood flow to the hand a test for occlusion of the radial or ulnar arteryinwhichoneofthesearteriesis compressedafterbloodhasbeen forcedoutwithhandbyclenchingit into a fist Failure of the blood to diffuse into the hand when open is an indicative of occlusion of uncompressed artery. a. elevate the hand first and make a first for approximately 30 seconds b. apply pressure over the ulnar and the radial arteries occluding both (keep the hand still elevated) c. open the hand which will be blanched d. release pressure on the ulnar artery and look for the perfusion of the hand for about 7 to 8 seconds f. If there is any delay then it may not be safe to perform radial artery puncture 2. Allow the patient to titrate with O2 for 5-10 minutes *if the patient has COPD, allow it for 30 minutes before taking the sample 3. Use ABG syringes which are heparinized*little amount of heparin content for anticoagulation 4. Wrist is extended5. Palpate the artery and hold fingers over the pulsation 6. Introduce the needle @ 45 degrees angle, slowly with the bevel facing upwards and aiming for the point of maximal pulsation 7. Obtain 2-3 ml once hit the artery8. Apply firm pressure for a minimum of 2 minutes. *longer, if the patient is on any antiplatelet medication or anticoagulant Side Effects of ABG analysis 1. Bleeding or bruising at the puncture site 2. Feeding Faint 3. Blood accumulation under the skin4. Infected at the puncture site Respiratory Physiology: Arterial Blood Gas Medicine I Delta Transcription Factor ^_^Page 2 Contraindications of ABG 1. Coagulopathy 2. Severe atherosclerosis 3. Infection/burn/previous surgery or cut down atsite 4. Decreased collateral flow Parameters of ABG (Normal values) arterial: rangenormal venousrange normal pH7.35 -7.457.407.31 -7.417.36 PCO235 - 45 mmHg4041 - 51 mmHg46 PaO280-95 mmHg10035 - 45 mmHg40 HCO3 22-26 mEq/L2422 - 26 mEq/L24 O2 sat95 - 99%97 68 - 77 %75% BE-2 to +20-2 to +20 *BE = base excess Interpretation of ABG pHPaCO2HCO3 Causes Respi Acidosis a.Acute b.Patially Compensated c.Compensated N. N. Lung Disease (pneumonia or COPD) Respi Alkalosis a.Acute b.Partially compensated c.Compensated N. N. Increased RR/ fast breathing, Pain or anxiety Metabolic Acidosis a.Acute b.Partially compensated c.Compensated N. N. Kidney Failure, shock, DKA Metabolic Acidosis a.Acute b.Partially compensated c.compensated N. N. Chronic vomiting, hypokalemia Organ systems responsible for acid-base regulationBlood calcium and other minerals and electrolytes are leached from bone and other tissues such as hair and nails if too acidic. Kidneys are the primary organ responsiblefor excreting acid and regulating electrolyte balance. Lungsregulate acidity by increasing the rate of respiration which results in excreting higher levels of CO2 the most efficient way of maintaining acid/base balance, especially in the short-term Skinacts as a secondary kidney.