Acid Base Balance

1. Acid Base Balance EMT Paramedic Fall 2007

2. And Now!Acids and BasesYippy!

3. Homeostasis • The biological and chemical processes occurring in our bodies depend on a consistent environment. • Homeostasis is our body’s system for maintaining that consistency.

4. Homeostasis & Acid-Base • Metabolic processes within our bodies function within a very narrow pH range. • Many diseases and environmental influences can greatly impact this delicate range.

5. Lets First Review • SpO2 = 90-100 (measures saturated hemoglobin through skin) • SaO2 = 90-100 (measures saturated hemoglobin in arterial blood)

6. More review • PaCO2 = 35-45 (dissolved CO2 in blood) • PaO2 = 80-100 for adult and child 40-70 for newborn 60-80 for geriatric (measures dissolved oxygen in blood)

7. Matilda • Matilda is 87 years old. Her doctor has called and told her to come down because her blood gasses were off in her labs. These are her labs. • SpO2 = 68 • PaCO2 = 50 • PaO2 = 55

8. Who cares? • You do! Because the more we know about acid-base derangements the better we can treat patients in order to correct the derangements.

9. Acids and Bases Here we go!

10. Acids • A substance that releases H+ Ions when dissolved in water • Lactic acid • Ketones • Carbonic acid

11. Bases • Also known as alkalis, these are H+ seekers and also dissociate in water. When bases dissolve in water the hydroxyl ion is released (OH-) this little guy actively seeks out and attaches itself to acids floating around in the blood-stream. • Bicarbonate is most common base. • OH- + CO2 = HCO3

12. Acid-Base Physiology • During energy production, byproducts are released. Two of these main byproducts effect acid-base. • Carbon dioxide (CO2) • Hydrogen (H+)

13. Control that Hydrogen • The key to acid-base regulation is controlling hydrogen ion concentrations.

14. pH • P-what? I thought we were talking about hydrogen. The hydrogen ion concentration outside the cell is typically 4x10-8 mols/L or 0.00000004 equivalents per liter. That number is to small to work with so we use the pH scale instead.

15. pH Scale • Potential of Hydrogen • 1-14 • 7 is mid-range • 7.35-7.45 is normal for human body. • Hmm? So are we acidic or alkaloid?

16. pH and Hydrogen • pH levels are inversely proportional to H+ • This means as H+ increases pH decreases and as pH increases, H+ decreases.

18. Hmm So? • If we are normally 7.35 to 7.45 and that is considered slightly alkaloid then at what point are we acidotic? • Anything below 7.35 is acidotic to humans and anything above 7.45 is alkaloid. • 0.4 either way is as far as we like to go. About 6.9 acid and 7.8 alkalin.

19. Fatal Values • pH of less than 6.9 and pH of greater than 7.8 are typically not conducive with life.

20. Picky Picky • The body must maintain a fairly narrow alkaline environment in order for things to go smoothly. • Any imbalances can be very serious.

21. Back to Matilda • So here are her values from before and now what do you think that means to her pH? • SaO2 = 68 • PaCO2 = 50 • PaO2 = 55 • pH= 7.23

22. How do we keep it all balanced?

23. Balancing Systems • Buffer System • Respiratory System • Renal System

24. Buffer System • Fastest acting (nano-seconds) • Considered the chemical sponge (too much H+ use a sponge to clean it up. Or, need more give it a squeeze) • It can collect hydrogen ions when they are over-abundant and release them when they are scarce.

25. How does it work? • Basically the cells produce CO2 and H+ during metabolism. The buffer system will change those two through chemical reactions to keep things balanced. H+ <-> HCO3 <-> - H2CO3 <-> - H2O <-> CO2 Hydrogen Bicarb Carbonic Acid Water Carbon Dioxide

26. Gosh! What’s that mean? • Easy…if the body needs more acid, the buffer system takes water and carbon dioxide and makes carbonic acid (with the help of the enzyme carbonic anhydrase). Then carbonic acid can be split apart to make bicarbonate and hydrogen. This can go both directions

27. Respiratory System • Second fastest to respond (usually within minutes) • Triggered by Chemoreceptors in the vessels. • Example Diabetic keto-acidosis

28. Breathe! • When the pH gets a little out-o-wack a message is sent to the lungs. It tells them whether to breathe faster and harder or slower and more shallow.

29. How does that work? • Hydrogen binds with bicarbonate. This makes carbonic acid. Carbonic acid then breaks down into water and carbon dioxide. • In red blood cells carbon dioxide is carried to the lungs and exchanged for oxygen. • The majority of CO2 is transported as bicarbonates in the plasma

30. So in the lungs? • Oxygen has an affinity to hemoglobin and it climbs on board kicking off the CO2 • The CO2 and water are displaced and through osmosis and diffusion are blown out with expiration of air.

31. Gee Whiz! • After the CO2 has been blown away in the lungs…what happens? • Exactly! The pH increases, bringing the body back to normal.

32. Renal System • If the lungs and buffers are not able to keep up with the amount of acids, then the kidneys must take action. • It may take the kidneys hours or days to react to an imbalance.

33. What do the kidneys do to help? • They regulate pH by expelling excess hydrogen or bicarbonate ions. • The kidney tubules are smart. When they expel one ion they will exchange it for another.

34. Kidneys work OT with COPD • When someone chronically retains CO2 the kidneys become the primary balancing system. • Example is the chronic emphysema patient. They rely entirely on the renal system to maintain pH.

35. More Values • Base Excess BE = +or- 6 • Bicarb HCO3 = 22-26mEq/L

36. Acid-Base Derangements • Respiratory: • Acidosis • Alkalosis • Metabolic: • Acidosis • Alkalosis

37. Respiratory Acidosis • Hypoventilation • Retained CO2 • pH decreases • Causes: • Trauma, illness, medications. • You guys can treat this!

38. Causes of Resp. Acidosis • Lungs – COPD, Pneumonia, ARDS • Airway obst. – Mucous plug, atelectasis, FBAO • Respiratory depression – anesthesia, OD, trauma • Inadequate lung expansion – skeletal trauma, pneumothorax, ascites

39. S/S for Resp. Acidosis • H/A (cerebral vasodilation) • Tachycardia (hypercapnia) • Bradycardia (incr. K+) • Cardiac arrhythmias (hyperkalemia) • Decr. CNS – confusion to coma • neuromuscular weakness - hyporeflexia, flaccid paralysis

40. Tx: for Resp Acidosis • Adequate hydration • Bronchodilators • OXYGEN

41. Respiratory alkalosis • Hyperventilation • Pain, anxiety • Blows off CO2 • pH Increase • O2 orRebreathe CO2???

42. Causes of Resp Alkalosis • Anxiety, pain, or hypoxia due to epi release • Febrile • ASA OD • Brain trauma/tumor • Septic shock (early)

43. S/S of Resp. Alkalosis • Dizziness • Numbness, tingling in fingers, around mouth • Cardiac arrhythmias (decr. K+ and Ca++)

44. Tx for Resp. Alkalosis • Rebreathe CO2 • OXYGEN

45. Metabolic acidosis • Excessive acid production • N/V/D, DM, Rx • pH Decreased • CO2 Normal EMS tx is ventilation • Sometimes NaHCO3-

46. Causes of Metabolic Acidosis • Ketoacidosis • Lactic acidosis • Renal failure • Incr. Metabolic rate • Poisoning • Severe diarrhea

47. S/S of Metabolic Acidosis • Skin warm, flushed • Cardiac arrhythmias (decr. Contractility and inotropic response to catecholamines) • Lethargy to coma • Decr. Pulse (decr. CO) • Decr. BP, dehydration (GI losses)

48. Tx for Metabolic Acidosis • DKA – insulin, fluids • Alcoholism-related ketoacidosis – glucose and saline • Diarrhea – correct fluid and electrolyte imbalances • Acute renal failure – dialysis • Lactic acidosis – correct hypoxia and hypoperfusion

49. Tx for Metabolic acidosis, cont. • Admin. Sodium bicarb. IV when pH is <7.2 • Potassium replacement – when acidosis is corrected, K+ will shift back into cells = hypokalemia • Mechanical ventilation; compensatory hyperventilation

50. Metabolic alkalosis • Infrequent • Diuretics, vomiting • Too much IV bicarb • pH Increased • CO2 Normal • HCO3 Increased • H+ + HCO-3 <----> H2CO3 <---> H20 + CO2