This document summarizes arterial blood gas (ABG) analysis, including indications, sample collection techniques, measurement interpretations, and compensation mechanisms. It describes how ABG tests are used to assess respiratory and acid-base status by measuring pH, pCO2, pO2, HCO3, and other values. The radial artery is most commonly used for puncture due to low risk of complications. Interpretation of ABG values indicates acid-base and oxygenation status, and whether the lungs or kidneys are compensating. Normal ABG ranges are also provided for reference.

1. Arterial Blood Gas Analysis Dr. Tongjun Ma Emergency Department of Tianjin medical university General Hospital

2. 3 parts: introduction: contents, indications artery puncture technique explain the important measurements

3. Contents of ABG Measures pH Percent of H + Concentration pCO 2 Pressure of Carbon Dioxide pO 2 Pressure of Oxygen Sao 2 Oxygen Saturation BE Base Excess HCO 3 Bicarbonate

5. Indications assess respiratory function adequacy of ventilation and oxygenation make changes in treatment, such as ventilator settings evaluate acid-base status

6. Blood sample collection 2 methods: artery puncture capillary blood

7. Complications of Puncture Bleeding Local, occult Ischemic consequences spasm, thrombosis, embolism trauma Nerve, tendon Infection With the use of proper technique, the complication rate is extremely low.

8. Puncture sites consider the risk of hemorrhage and how to control the risk of complete blood flow loss the risk of injury patient comfort and nursing care concerns possible sites: Radial, Femoral, Brachial

9. Radial artery the one most commonly used collateral circulation the risk of obtaining venous blood or damaging a nerve is low

10. Femoral artery

11. Brachial artery the risk of complications is greater than radial artery has little collateral circulation avoid except in extreme circumstances

12. Puncture technique 4 steps: Preparation cleanse the skin, local anesthesia Puncture Cap the syringe and transport

13. Preparation 1 Preparation of Client Oxygen, the settings for the respirator, the temperature Found the artery The pulsations of the radial artery should be palpable just proximal to the transverse wrist creases

14. Preparation 2 Syringe a prepackaged ABG kit Choose a syringe with minimal dead space (e.g., BD insulin syringe) , 0.5-1.0 ml, Airtight Heparinized, eliminate heparin-related errors ,All heparin should be ejected

15. Step 2 cleanse the skin iodine and alcohol local anesthesia an intradermal wheal of 1% lidocaine

16. Puncture Angle 30°to 45°, 60 °, 75 ° If resistance is met or no blood returns, the needle should be slowly withdrawn press for 5 minutes or longer to control bleeding

17. Cap and transport expel all air bubbles within 2 min Cap the syringe transport to the laboratory put the sample on ice if the test is not completed within 10 min

18. Key points Use small-gauge needle Do not puncture the same site repeatedly Confirm the potency of the ulnar artery Doppler examination Allen test

20. What is pH Acidic Alkaline Neutral 0 14 7 How acidic or base a substance is Scale runs from 1 – 14 Less than 7 is acidic, Greater than 7 is base

21. Arterial Blood pH 7.4 Academia Acidosis? Alkalemia Alkalosis? 7.35~7.45 6.8 7.8 DEATH DEATH

22. Importance of pH Ensure metabolic intermediates are in the ionized state Intracellular enzymes have a pH optimum DNA, RNA and protein synthesis is facilitated at this pH Every enzymatic reaction in the body is affected by pH!

23. Adverse Clinical Effects of Acidemia

24. Compensation The goal is to try to maintain normal pH If the compensation occurs fully, the pH returns to normal If the compensating organ cant work hard enough to compensate, the pH will still be abnormal

25. Lungs Compensation by changing respiratory rate  pH (acid) , respiratory rate  to blow off CO 2 Very sensitive and can compensate quickly tires easily so cant continue long term

26. Body is open If add 12 mM H + to closed system if all acid is buffered [CO 2 ] = 13.2, [HCO 3 ] = 12, pH = 6.06 : lethal If add 12 mM H + to body Body is open through lungs, all extra CO2 expelled [CO 2 ] = 1.2, [HCO 3 ] =12, pH = 7.1

27. Kidneys Compensation Changes the amount of hydrogen excreted and bicarbonate retained  pH (acid) = kidneys excrete more H + and retain more bicarbonate so HCO 3  More powerful but slower (hours to days)

28. pH pH  ? uncompensated alkalosis pH ↓ ? uncompensated acidosis Normal pH ?

29. PCO 2 Carried as carbonic acid , so it has an inverse ration with pH Controlled by the lungs Normal range 35~ 45 mmHg  35 = hyperventilation or base (alkalosis)  45 = hypoventilation or acidic (acidosis) [H 2 CO 3 ]: 40×0.03=1.2mmol/L

30. HCO 3 - Measurement of amount of bicarbonate in blood Normal range 22~ 26 mmol/L, Controlled by kidneys  22 = acidosis  26 = alkalosis

31. Hendersen-Hasselbalch equation

32. If = 1 pH = 6.1 If = 10 pH = 7.1 If = 20 pH = 7.4 If = 30 pH = 7.6

33. Base Excess Indication of how much extra base is available to the body Normal ABG: -2 to +2  -2 = acidic (acidosis)  +2 = base (alkalosis)

34. PaO 2 Measures oxygen carried by red blood cells and dissolved in plasma 75-100mmHg <75=hypoxia drops about 3-5mmHg for each decade after 30 years of age

35. SaO 2 the actual amount of oxygen carried by Hb compared with the amount of oxygen that Hb is capable of carrying 95~100% Often measured by a probe that is attached to a finger or earlobe decreased occurs in carbon monoxide poisoning and hypoxia Unreliable if peripheral perfusion is poor or in the presence of nail polish, excessive movement

36. Comparison with PO2 values 20mmHg 35% 50mmHg 84% 60mmHg 89% 80mmHg 95% 100mmHg 98%

37. Review of Normal ABG pH 7.35 – 7.45 pCO2 35 – 45 pO2 75 – 100 HCO 3 - 22 – 26 SaO 2  95%

38. Thank you