Acid base lecture (1)
- 3. It’s as simple as the HendersonHasselbalch Calculation…
- 5. Acid-Base is about 2 things: The patient’s pH & what is causing it
- 6. WHY DOES A PATIENT’S Acid-Base Status MATTER?
- 8. So let’s learn how to do what we do BETTER.
- 9. What is pH?
- 10. pH is the potential for Hydrogen pH = Hydrogen = H+ So, when you think pH, think H+
- 12. pH < 7.35 = Acidosis
- 14. pH > 7.45 = Alkalosis
- 16. So, pH < 7.35 = acidosis pH > 7.45 = alkalosis
- 17. Now the money question: What is causing the imbalance?
- 19. Four Categories of Disturbance Metabolic Metabolic Acidosis Metabolic Alkalosis Alkalosis Respiratory Respiratory Acidosis Respiratory Alkalosis
- 20. Metabolic The most basic way to determine metabolic disturbance is to look at a patient’s bicarb level. Metabolic = HCO3
- 22. Metabolic HCO3 is a base. So, if a patient’s HCO3- is low, what is their acid-base disturbance?
- 23. Metabolic Acidosis The patient’s body has a deficit of bicarbonate. -< HCO3 22
- 25. Causes of Metabolic Acidosis • • • • • • • Ketones (Diabetic, Alcoholic, Starving) Uremia Lactic Acidosis Glycols Salicylates Rhabdomyolysis Various Toxins
- 26. Metabolic Alkalosis The patient’s body has an excess of bicarbonate. -> HCO3 26
- 27. Causes of Metabolic Alkalosis • • • • • • • Renal Failure Excessive Vomiting GI Suctioning Overuse of Antacids (Calcium Carbonate) Diuretics, Laxative Abuse Hypo-kalemia, calcemia, chloremia Hyperaldosteronism
- 29. Respiratory The most basic way to determine respiratory disturbance is to look at a patient’s PaCO2. Respiratory = PaCO2
- 31. Respiratory CO2 is an acid. So, if a patient’s PaCO2 is high, what is their acid-base disturbance?
- 32. Respiratory Acidosis Respiratory acidosis is an excess of carbon dioxide. PaCO2 > 45
- 34. Causes of Respiratory Acidosis Practically every Respiratory Disorder known in Medicine Anything that causes decreased ventilation. - COPD, Asthma, CHF, Pneumonia, Aspiration, Flail Chest, Pneumothorax, Pleural Effusion, etc… Anything that causes decreased respiratory rate. - Narcotics, Sedatives, Brainstem Injury, Cardiac Arrest, etc.
- 35. Respiratory Alkalosis Respiratory alkalosis is a deficit of carbon dioxide. PaCO2 < 35
- 37. Causes of Respiratory Alkalosis Anything that can cause increased minute volume. Pulmonary Embolism Alcohol Fever Head Trauma CVA’s Pneumonia Hyperthyroidism Exercise Anxiety Overaggressive Mechanical Ventilation
- 38. Four Categories of Disturbance Metabolic Acidosis Respiratory Acidosis Metabolic Respiratory Alkalosis Alkalosis
- 39. To Sum it Up: HCO3- = Metabolic Acidosis - HCO3 = Metabolic Alkalosis PaCO2 = Respiratory Acidosis PaCO2 = Respiratory Alkalosis
- 41. Simple Disorders: Case 1 65 y/o Female Carbon Monoxide Poisoning pH: 7.20 torr HCO3: 12 mEq/L PaCO2: 38 torr What is her acid-base status?
- 42. Simple Disorders: Case 2 32 y/o Male Acute Asthma pH: 7.08 torr HCO3: 26 mEq/L PaCO2: 60 torr What is his acid-base status?
- 43. Simple Disorders: Case 3 21 y/o Male Suspected Pulmonary Embolism pH: 7.48 torr HCO3: 22 mEq/L PaCO2: 20 torr What is his acid-base status?
- 44. Simple Disorders: Case 4 28 y/o Pregnant Female Excessive Vomiting X4 days pH: 7.58 torr HCO3: 32 mEq/L PaCO2: 35 torr What is her acid-base status?
- 45. well, that was easy.
- 46. Well, we aren’t quite there yet…
- 47. Keep Going
- 48. Let’s talk about exceptions. Sometimes a pH is normal, but there is still a disturbance. Sometimes there is more than one disorder at play.
- 50. The Body STRIVES for a pH of about 7.40
- 52. Buffer System • Activates in Seconds • Fastest & First Line of Defense • The MOST important buffer system is the bicarbonate-carbonic acid system. • Hemoglobin and Oxyhemoglobin, Protein, and Phosphate Buffer Pairs
- 53. TENACITY
- 54. Respiratory System • Activates in Minutes to Hours • Second Defense to Activate • H+ concentration stimulates breathing center
- 56. Renal System • Activates in Days • Works by conserving or excreting H+ and HCO3• Strongest mechanism for control.
- 57. When the body uses these systems to attempt to maintain a pH that is NORMAL, this is called COMPENSATION
- 58. Example: Pt has Respiratory Acidosis Buffer System increases HCO3- in Blood Increase in pH
- 59. Example: Pt has Metabolic Acidosis Increases Respiratory Rate Decreases CO2 Increase in pH
- 60. Compensation If changes in pH don’t normalize, the disturbance is called Partially Compensated If changes in pH normalize, it is called Fully Compensated
- 61. Compensation: pH normal = Fully Compensated pH abnormal = Partially Compensated
- 63. Compensated Disorders: Case 1 65 y/o Female COPD Exacerbation pH: 7.35 torr HCO3: 18 mEq/L PaCO2: 60 torr What is her acid-base status?
- 64. Compensated Disorders: Case 2 18 y/o Female Type I Diabetic Patient pH: 7.30 torr HCO3: 18 mEq/L PaCO2: 24 torr What is her acid-base status?
- 65. Compensated Disorders: Case 3 18 y/o Male Traumatic Brain Injury pH: 7.45 torr HCO3: 18 mEq/L PaCO2: 22 torr What is his acid-base status?
- 67. Extra Bad Mixed Disorders Sometimes you have two independent disorders that drive the pH in the same direction. This is extra BAD. Example: COPD patient in Shock (Respiratory and Metabolic Acidosis)
- 70. Summary
- 71. Summary • Determine the pH
- 72. Summary • Determine the pH • Determine the category of disorder
- 73. Summary • Determine the pH • Determine the category of disorder • Is it a mixed disorder?
- 74. Summary • • • • Determine the pH Determine the category of disorder Is it a mixed disorder? Is it fully or partially compensated?
- 75. the patient you have, ot the one you wish you had.