Let’s review

24. Let’s review

25. Regulation of Acid-Base Balance • Buffering systems neutralize acids & bases & include lungs & renals • Buffer—substance or a group of substances that can absorb or release H+ to correct an acid-base imbalance • Arterial pH indirect measurement of H+ ion

26. Regulation of Acid-Base Balance • pH reflection of balance between CO2 (lungs) & HCO3- (renal) • Acidosis • Increased amount of H+ ions • Normal pH 7.35-7.45 • pH = 7 is neutral • pH < 7 is acid • pH > 7 is alkaline

27. Regulation of Acid-Base Balance • AB balance exists when the rate at which the body produces acid or bases = the rate at which the acids or bases are excreted • Normal hydrogen ion level is necessary to maintain cell membrane integrity & speed of cellular enzymatic actions

28. Acid-Base Regulators • Chemical regulation • Largest chemical buffer in ECF is carbonic acid/bicarb buffer system • First buffer system to react • Reacts in seconds • Lungs control excretion of carbon dioxide

29. Acid-Base Regulators • Kidneys control excretion of hydrogen & bicarbonate ions • ECF becomes more acidic pH decreases • ECF receives more base substances, pH rises

30. Acid-Base Regulators • Biological Regulation • Occurs after chemical buffering • Occurs hydrogen ions are absorbed or released by cells • Hydrogen ion + charged & must be exchanged with another + charged ion—frequently K+ • Conditions that produce excess acidH+ ion enter cellpotassium ion leaves cellenters ECFelevated K+ levels

31. Acid-Base Regulators • Biological buffer • Hemoglobin-oxyhemoglobin system • CO2 diffuses to RBCforms carbonic aciddissociates to H+ & HCO3+ ionsH+ ions attach to hemoglobinHCO3+ available for buffering • Chloride shift in RBCs • Bld oxygenated in lungs, bicarb diffuses into cellchloride travels from hemoglobin to plasma to maintain electrical neutrality

32. Acid-Base Regulators Metabolic acidosisresp increasegreater amt CO2 exhaleddecreased acidic level • Physiological regulation • Lungs & kidneys • If diseased is no longer effective for regulation • Lungs adapt rapidly to imbalance • Increased H+ & CO2 ions stimulate respiration

33. Acid-Base Regulators • Physiological Regulation • Kidneys take a few hrs to several days to regulate acid-base balance • Inc or dec HCO3+ production • Certain amino acids in renal tubules change to ammonia NH3- & excreted by kidneys

34. Acidosis

35. Acid-Base Balance • Acid-base balance is regulated by the body’s ability to maintain arterial pH 7.35-7.45 • Checked by ABGs • Deviation from normal value indicates experiencing an acid-base imbalance

36. Breakdown of ABGs • pH • Measures H+ ions concentration in body fluids • Slight change can be life threatening • Acidic—increase in H+ ions • Alkaline—decrease in H+ ions

37. ABGs • PaCO2 • Partial pressure of carbon dioxide in arterial bld • Reflection of depth of pulmonary ventilation • Normal 35-45 mm Hg • **Hyperventilation PaCO2 < 35 mm Hg • Carbon dioxide is exhaled & amt dec

38. ABGs • **hypoventilation • PaCO2 is > 45 mm Hg • Less carbon dioxide is exhaled • Increasing concentration of carbon dioxide

39. ABGs • PaO2 • Parital pressure of O2 in arterial bld • Normal 80-100 mm Hg • N0 primary role in A-B regulation when normall • PaO2 < 60 causes anaerobic metabolism—produces lactic acid—metabolic acidosis

40. ABGs • Oxygen Saturation • When hemoglobin is saturated with O2 • Normall 95-99% • Changes in temp,PaCO2 & pH affect oxygen

41. ABGs • Base Excess • Amt of blood buffer • Normal +/- 2 mEq/L • High value—alkalosis • Citrate excess from rapid blood transfusions • IV HCO3 infusion DKA\ • Ingestion large amt bicarb solutions (antacids)

42. ABGs • Base excess • Low value—acidosis • Lg amts of bicarb ion excretion • ie: diarrhea

43. ABGs • Bicarbonate • Major renal component • Kidneys excrete & retain to maintain normal balance • Principal buffer ECF • Normal 22-26 mEq/L • Metabolic acidosis < 22 mEq/L • Metabolic alkalosis > 26 mEq/L

44. Acid-Base Imbalances • Either respiratory or metabolic, depend on their underlying cause • Corrects AB imbalances through process known as compensation

45. Respiratory Acidosis • pH < 7.35 • PaCO2 >45 mm Hg • PaO2 < 80 mm Hg • Bicarb level normal if uncompensated • Bicarb level > 26 mEq/L if compensated • HypoventilationCSF & brain cells become acidicneurological changes hypoxemiafurther neurological impairment • Hyperkalemia & hypercalcemia can occur • Kidneys hold to bicarb & release hydrogen ions UA—may take 24 hrs

46. Respiratory Acidosis Causes • Hypoventilation resulting primary respiratory problems • Chest wall injury • Respiratory failure • Cystic fibrosis • Pneumonia • Atelectasis (obstruction of small airways often caused by mucus) • Hypoventilation resulting from factors other than resp system • Obesity • Head injury • Drug overdose (OD) with resp depressant • Paralysis of resp muscles caused by neurological alterations

48. Respiratory Acidosis • S/S • Convulsion • Coma • Muscular twitching • Confusion • Dizziness • Lethargy • HA • Warm flushed skin • Ventricular dysrhythmia

49. Respiratory Alkalosis • pH >7.45 • PaCO2 <35 mm Hg • PaO2 normal • HCO3 nl if short-lived or uncompensated • HCO3 <22 mm Hg if compensated • Begins outside resp system ie: anxiety, panic attack OR within resp system ie: initial phase of asthma attack • Body does not usually compensate because pH returns to nl before kidneys can respond

50. Respiratory Alkalosis • Causes • Salicylate overdoes • Anxiety • Hypermetabolic states ie: fever, exercise • CNS disorders ie: head injury, infections • Asthma • Pneumonia • Inappropriate vent settings • S/S • Confusion • Dizziness • Convulsions • Coma • Tachypnea • Numbness/tingling of extremities • dysrhythmias