Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Chapter 42 Agents Affecting the Volume and Ion Content of Body Fluids

2Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Drugs to Correct Disturbances  Drugs used to correct disorders of fluid volume and osmolality  Drugs used to correct disturbances of hydrogen ion concentration  Drugs used to correct electrolyte imbalances

3Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Agents Affecting the Volume and Ion Content of Body Fluids  Disorders of fluid volume and osmolality  Acid-base disturbances  Potassium imbalances  Magnesium imbalances

4Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Fluid Volume and Osmolality  Good health requires that both the volume and the osmolality of extracellular and intracellular fluids remain within a normal range  Maintenance of both is primarily the job of the kidneys  Volume contraction and volume expansion

5Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Volume Contraction and Volume Expansion  Volume contraction  Decrease in total body water  Definition, causes, and treatment Isotonic, hypertonic, and hypotonic Isotonic, hypertonic, and hypotonic  Volume expansion  Increase in total body water  Definition, causes, and treatment Isotonic, hypertonic, and hypotonic Isotonic, hypertonic, and hypotonic

6Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Isotonic Contraction  Definition  Volume contraction in which sodium and water are lost in isotonic proportions  Decrease in total volume, but no change in osmolality  Causes  Vomiting, diarrhea, kidney disease, and misuse of diuretics  Treatment  Fluids that are isotonic to plasma  0.9% NS  Replenish slowly to prevent pulmonary edema

7Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Hypertonic Contraction  Definition  Loss of water exceeds loss of sodium  Reduced extracellular fluid volume and increase in osmolality  Causes  Excessive sweating, osmotic diuresis, concentrated food given to infants  Secondary to extensive burns or CNS disorders that interfere with thirst  Treatment  Hypotonic fluids or fluids that contain no solutes at all (D 5 W)  Initial therapy: drink water

8Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Hypotonic Contraction  Definition  Loss of sodium exceeds loss of water  Both volume and osmolality of extracellular fluid are reduced  Causes  Excessive loss of sodium through the kidney (diuretic therapy, chronic renal insufficiency, lack of aldosterone)  Treatment  Mild: infusing isotonic sodium chloride solution for injection  Severe: hypertonic solution (3%) NaCl  Watch for signs of fluid overload

9Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Volume Expansion  Definition  Increase in the total volume of body fluid  May be isotonic, hypertonic, hypotonic  Causes  Overdose with therapeutic fluids  Disease states (congestive heart failure [CHF], nephrotic syndrome, cirrhosis with ascites)  Treatment  Diuretics  Agents used for heart failure

10Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Acid-Base Disturbances  Acid-base balance is maintained by multiple systems  Bicarbonate–carbonic acid buffer system  Respiratory system CO 2 (increase lowers pH) CO 2 (increase lowers pH)  Kidneys HCO 3 – (increase raises pH) HCO 3 – (increase raises pH)

11Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Acid-Base Disturbances  Respiratory alkalosis  Respiratory acidosis  Metabolic alkalosis  Metabolic acidosis

12Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Respiratory Alkalosis  Causes  Hyperventilation causes decrease in CO 2  Treatment  Mild: none needed  More severe: rebreathe CO 2 -laden expired breath

13Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Respiratory Acidosis  Causes  Retention of CO 2 secondary to hypoventilation Depression of the medullary respiratory center Depression of the medullary respiratory center Pathologic changes in the lungs Pathologic changes in the lungs  Treatment  Correction of respiratory impairment  Infusion of sodium bicarbonate if severe

14Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Metabolic Alkalosis  Causes  Excessive loss of gastric acid  Administration of alkalinizing salts  Treatment  Solution of sodium chloride plus potassium chloride

15Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Metabolic Acidosis  Causes  Chronic renal failure  Loss of bicarbonate during severe diarrhea  Metabolic disorders  Poisoning by methanol and certain medications  Treatment  Correction of the underlying cause of acidosis  Alkalinizing salt if severe

16Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Potassium  Most abundant intracellular cation  Extracellular concentrations are low  Major role in:  Conducting nerve impulses  Maintaining the electrical excitability of muscle  Regulating acid-base balance

17Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Regulation of Potassium Levels  Primarily by the kidneys  Renal excretion increased by aldosterone  Excretion also increased by most diuretics  Potassium-sparing diuretics are the exception  Influenced by extracellular pH  Alkalosis potassium uptake enhanced  Acidosis potassium exits cells  Insulin has a profound effect on potassium level

18Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Hypokalemia  Serum potassium levels less than 3.5 mEq/L  Causes and consequences  Most common cause is treatment with a thiazide or loop diuretic Less common: excessive insulin, alkalosis Less common: excessive insulin, alkalosis  Adverse effects on skeletal muscle, smooth muscle, blood pressure, and the heart  Hypokalemia increases the risk for hypertension and stroke

19Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Hypokalemia Treatment  Potassium salts preferred because chloride deficiency frequently coexists with hypokalemia  Oral potassium chloride: mild Sustained-release version has fewer GI effects Sustained-release version has fewer GI effects Abdominal discomfort, nausea and vomiting, diarrhea Abdominal discomfort, nausea and vomiting, diarrhea  IV potassium chloride: severe or cannot take PO Must be diluted and infused slowly Must be diluted and infused slowly

20Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Hypokalemia Treatment   Contraindications to potassium use   Avoid in patients who are predisposed to hyperkalemia Severe renal impairment, use of potassium-sparing diuretics, hypoaldosteronism   Principal complication of hypokalemia is hyperkalemia   Assess renal function and changes in ECG ECG = electrocardiogram.

21Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Hyperkalemia  Excessive elevation of serum potassium  Causes Severe tissue trauma Severe tissue trauma Untreated Addison’s disease Untreated Addison’s disease Acute acidosis (draws K out of cells) Acute acidosis (draws K out of cells) Misuse of potassium-sparing diuretics Misuse of potassium-sparing diuretics Overdose with IV potassium Overdose with IV potassium

22Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Hyperkalemia  Consequences  Disruption of the electrical activity of the heart  Earliest sign patient is in danger Mild elevation (5–7): T wave heightens; PR prolonged Mild elevation (5–7): T wave heightens; PR prolonged Severe elevation (8–9): cardiac arrest can occur Severe elevation (8–9): cardiac arrest can occur  Noncardiac signs Confusion, anxiety, dyspnea, weakness or heaviness of legs, numbness/tingling of hands/feet/lips Confusion, anxiety, dyspnea, weakness or heaviness of legs, numbness/tingling of hands/feet/lips

23Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Hyperkalemia  Treatment  Withhold foods that contain potassium  Withhold medicines that promote potassium accumulation  Counteract potassium-induced cardiotoxicity  Lower extracellular levels of potassium Calcium gluconate Calcium gluconate Infusion of glucose and insulin Infusion of glucose and insulin If acidotic: infusion of sodium bicarbonate If acidotic: infusion of sodium bicarbonate

24Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Magnesium  Required for the activity of many enzymes  Binding of messenger RNA to ribosomes

25Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Magnesium Imbalances  Hypomagnesemia  Causes Diarrhea Diarrhea Hemodialysis Hemodialysis Kidney disease Kidney disease Prolonged intravenous feeding Prolonged intravenous feeding Chronic alcoholism Chronic alcoholism Hypermagnesemia Hypermagnesemia  Prevention and treatment Magnesium gluconate and magnesium hydroxide Magnesium gluconate and magnesium hydroxide Magnesium sulfate Magnesium sulfate

26Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Magnesium Imbalances  Hypermagnesemia  Most common in patients with renal insufficiency