Acid-‐Base Balance Compensation refers to the body processes that occur to counterbalance an acid-base disturbance. When compensation has occurred, the pH will be within normal limits. Metabolic acidosis A total concentration of buffer base that is lower than normal, with a relative increase in the hydrogen ion concentration. This results from loss of buffer bases or retention of too many acids without sufficient bases, and occurs in conditions such as renal failure and diabetic ketoacidosis, from the production of lactic acid, and from the ingestion of toxins, such as acetylsalicylic acid (aspirin). Metabolic alkalosis A deficit or loss of hydrogen ions or acids or an excess of base (bicarbonate) that results from the accumulation of base or from a loss of acid without a comparable loss of base in the body fluids. This occurs in conditions resulting in hypovolemia, the loss of gastric fluid, excessive bicarbonate intake, the massive transfusion of whole blood, and hyperaldosteronism. Respiratory acidosis A total concentration of buffer base that is lower than normal, with a relative increase in hydrogen ion concentration; thus a greater number of hydrogen ions is circulating in the blood than the buffer system can absorb. This is caused by primary defects in the function of the lungs or by changes in normal respiratory patterns as a result of secondary problems. Any condition that causes an obstruction of the airway or depresses respiratory status can cause respiratory acidosis. Respiratory alkalosis A deficit of carbonic acid or a decrease in hydrogen ion concentration that results from the accumulation of base or from a loss of acid without a comparable loss of base in the body fluids. This occurs in conditions that cause overstimulation of the respiratory system. Respiratory acidosis: (carbonic acid excess) occurs when a person hypoventilates which leads to a buildup of CO2, resulting in a buildup of carbonic acid in the blood i. Cause: COPD, barbiturate or sedative OD, chest wall abnormality, severe pneumonia, atelectasis, respiratory muscle weakness, and mechanical hypoventilation ii. Pathophysiology: CO2 retention from hypoventilation iii. Compensatory mechanism: HCO3- retention by kidney and secretion of H+ into the urine iv. Clinical manifestations: drowsiness, confusion, dizziness, HA, coma, decreased blood pressure, ventricular fibrillation (related to Hyperkalemia from compensation), warm flushed skin, seizures, and hypoventilation with hypoxia Respiratory alkalosis: (carbonic acid deficit) occurs with hyperventilation and the primary cause is hypoxemia from acute pulmonary disorders. v. Cause: hyperventilation (hypoxemia, pulmonary emboli, anxiety, fear, pain, exercise, fever), stimulated respiratory center (septicemia, encephalitis, brain injury, salicylate poisoning), and mechanical hyperventilation vi. Pathophysiology: increased CO2 excretion from hyperventilation vii. Compensatory mechanism: HCO3- excretion by the kidneys. Compensated respiratory alkalosis is rare. viii. Clinical manifestations: dizziness, light-headedness, confusion, HA, tachycardia, dysrhythmias (related to hypokalemia from compensation), nausea, vomiting, epigastric pain, tetani, numbness, tingling of extremities, hyperreflexia, seizures, and hyperventilation Metabolic acidosis (base bicarbonate deficit) occurs when an acid other than carbonic acid accumulates in the body or when bicarbonate is lost from body fluids ix. Cause: diabetic ketoacidosis, lactic acidosis, starvation, severe diarrhea, renal tubular acidosis, renal failure, GI fistulas, and shock x. Pathophysiology: gain of fixed acid and inability to excrete acid or loss of bicarbonate. xi. Compensatory mechanism: CO2 excretion by lungs. Patients often develop kussmaul respirations (deep, rapid breathing) while the kidneys attempt to excrete additional acid. xii. Clinical manifestations: drowsiness, confusion, dizziness, HA, coma, decreased blood pressure, dysrhythmias (related to Hyperkalemia from compensation), warm flushed skin, nausea, vomiting, diarrhea, abdominal pain, and deep, rapid respirations Metabolic alkalosis: (base bicarbonate excess) occurs when a loss of acid or a gain in bicarbonate occurs xiii. Cause: severe vomiting, excess gastric suctioning, diuretic therapy, K+ deficit, excess NaHCO3 intake, and excessive mineral corticoids xiv. Pathophysiology: loss of strong acid or gain of base xv. Compensatory mechanisms: CO2 retention by the lungs, The compensatory mechanism to correct metabolic alkalosis is limited. There is a decreased respiratory rate to increase the plasma level of CO2, but once the plasma CO2 reaches normal levels it causes stimulation of chemoreceptors and results in ventilation. xvi. Clinical manifestations: dizziness, light-headedness, confusion, HA, tachycardia, dysrhythmias (related to hypokalemia from compensation), nausea, vomiting, anorexia, tetany, tremors, tingling of fingers and toes, muscle cramps, hypertonic muscles, seizures, and hypoventilation In both respiratory and metabolic acidosis the CNS is depressed à acidosis is a “downer” In both respiratory and metabolic alkalosis the CNS is irritated à alkalosis is an “upper” IV Therapy 0.Acid-‐Base Balance Many patients need maintenance IV fluid therapy when they cannon take oral fluids while other patients need corrective or replacement therapy for losses. . xxiii. but provides 170 cal/L xxvii. does not provide free water or calories. . Include colloids (protein solutions such as plasma. used as maintenance fluid although it does not replace daily losses of other electrolytes. calories. KCl. but provides 170 cal/L . Hypotonic solutions: provide more water than electrolytes therefore diluting the ECF. These solutions are used to treat hypovolemia and hyponatremia. Ringer’s solution: similar in composition to plasma except that is has excess CL. provides 170 cal/L and does not provide electrolytes. but any concentration higher needs to given through a central line. and serum Na levels because of the risk for intravascular fluid volume excess. and does not provide free water or calories Hypertonic solutions: inititially raises the osmolality of ECF and expands it. Maintenance fluids are generally hypotonic because normal daily losses are hypotonic. Cl. 5% Dextrose in water: (technically isotonic. Isotonic solutions: expands only the ECF with no net loss from the ICF. and lactate (precursor to bicarb). K. and free water. and provides 340 cal/L xxv. used to replaced water losses. These fluids have the potential to cause cellular swelling so patients need to be monitored closely for changes in mental status as this may indicate cerebral edema. MgSO4. These additions help to increase vascular fluid. Lactated Ringer’s solution: similar in composition to normal plasma except does not contain Mg. dextran. but physiologically hypotonic) provides 50 g/L of glucose. and may cause intravascular overload or hyperchloremic acidosis xxi. and replace extracellular fluid losses.45% NS.45% NS: hypotonic. and no HCO3. Isotonic saline can be used when a patient is experiencing both fluid and sodium losses or with vascular fluid replacement in hypervolemic shock.IV additives can be added to these solutions for specific electrolyte imbalances. You can administer 10% dextrose or less through a peripheral line.9% NS: isotonic. contains. no Mg. xvii. 5% Dextrose in 0. and commercial plasmas). xxiv. These solutions require close monitoring of blood pressure.are common additives in basic IV solutions. provides free water necessary for renal excretion of solutes. Cl. Ca. and provides no calories. contains Na and CL in excess of plasma levels. does not provide free water. albumin. 5% Dextrose in water xx. The primary use of these solutions is for provisional calories with parenteral nutrition. This draws water out of the cells into the EFC. no electrolytes. used to replace hypotonic losses and treat hypernatremia. lung sounds. used to replaced hypotonic fluid losses. provides free water in addition to Na and Cl.0% NS: used to treat symptomatic hyponatremia and must be administered slowly and with extreme caution because it may cause dangerous intravascular volume overload and pulmonary edema xxvi. xix. This type of fluid replacement is idea for a patient with an ECF volume deficit. 5% Dextrose in 0. used to expand the intravascular volume.225% NS: provides Na. 0. 10% Dextrose in water: provides free water only. and hetastarch (Hespan). 3. may be used to treat mild metabolic acidosis but should not be used to treat lactic acidosis.Plasma Expanders: these stay in the vascular space and increase the osmotic pressure. 5% Dextrose in 0. and HCO3. Na. used to treat losses from burns and lower GI. used to expand intravascular volume and replace extracellular fluid losses. treats hypernatremia.9% NS: same as 0. CaCl. only solution that can be administered with blood products. xviii.9% NS. or other electrolytes. Excessive administration of isotonic saline should be avoided because it can result in elevated sodium and chloride levels. and provides 170 cal/L xxii.45% NS: same as 0. Acid-‐Base Balance .