4. When carbon dioxide dissolves in water, it can do so as a gas dissolved in water or by reacting with water to produce carbonic acid. In the cells of your body, the rate of carbonic acid production is accelerated by the enzyme carbonic anhydrase when excess hydrogen ions are added to the system the equilibrium is shifted to the left. This means that some of the added hydrogen ions will react with the bicarbonate ions to produce carbonic acid and the carbonic acid will dissociate into carbon dioxide and water as shown below. Carbonic acid is known as a weak acid because it partially dissociates into the positive Hydrogen ions and negative bicarbonate ions. When hydrogen ions are removed from the reaction, the equilibrium will shift to the right. More carbon dioxide will combine with water and more carbonic acid will be produced and more hydrogen ions and bicarbonate ions will be produced.
38. Electrolyte concentrations are calculated in milliequivalents mEq/L = ion concentration (mg/L) x number of charges on one ion atomic weight Na + concentration in the body is 3300 mg/L Na + carries a single positive charge. Its atomic weight is approximately 23. Therefore, in a human the normal value for Na + is: 3300 mg/L = 143 mEq/L 23 Note: One mEq of a univalent is equal to one mOsm whereas one mEq of a bivalent ion is equal to ½ mOsm. However, the reactivity of 1 mEq is equal to 1 mEq.
42. The Thirst Mechanism An increase of 2 – 3% in plasma osmolality triggers the thirst center of the hypothalamus. Secondarily, a 10 – 15% drop in blood volume also triggers thirst. This is a significantly weaker stimulus.
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45. A rather lame illustration You do remember how osmosis works, don’t you?
1. Respiratory acidosis [more CO2 indicates acidosis] pH - <7.35 PaCO2 – excess CO2 HCO3- low carbonic acid [HCO3 levels are lower than normal indicates acidosis 2. Respiratory alkalosis [more CO2 being exhaled than normal results in alkalosis] pH - > 7.45 PaCO2 – low CO2 HCO3 - high carbonic acid 3. Metabolic acidosis pH - <7.35 PaCO2 - normal HCO3 – low bicarbonate 4. Metabolic alkalosis pH - > 7.45 PaCO2 - normal HCO3- high bicarbonate
Body fluids made up of electrolytes Electrolyte is an element Separates into ions – cations (positive, Na+, K+, Ca+) and anions (negative, Chloride, bicarbonate [HCO3} Minerals (Example: Iron and Zinc) Initiate nerve responses Initiate muscle contractions Metabolize nutrients in foods Regulate electrolyte balance Regulate hormone production Strengthen bones Too much or too little causes serious consequences
Concentration gradient = the difference between the two concentrations (i.e. movement of oxygen and CO2 between the alveoli and blood vessels in the lungs
Treatments will be directed at eliminating the cause
Sodium Problem is because Na is found is most body fluids Loss of sodium without loss of body fluids, sodium becomes diluted in ECF Vomiting, suctioning, diarrhea, burn, diuretics, SIADH
Most common cause is over-hydration with D5W Post-op fluid replacement Heart failure Cirrhosis
1. Fluid moves outside cell – cells dehydrated Signs and symptoms Dry skin Dry mucus membranes, tongue Low BP Fever CNS - Agitated Restless Lab values – Na high, Urine – high Specific gravity Thirst Causes Diabetic ketoacidosis - Diabetes Insipidus - caused by a lack of response to ADH. commonly called pituitary DI . It is also known as central or neurogenic DI . posterior pituitary can be destroyed by - tumors, infections, head injuries, infiltrations, and various inheritable defects
Note - hypokalemia [ aLKalosis associated with Low K] Potassium Acquired in the diet Excreted in urine Must be replaced daily Function Maintains acid-base balance Participates in metabolism Causes Poor intake – patient is not eating Renal loss (diuretics) GI loss (diarrhea, vomiting) Signs and symptoms Tachycardia Low BP Flaccid muscles EKG – Flattened T wave Treatment Oral replacement if preferable, could be IV Low K+ could lead to digoxin toxicity due to low circulating volume
Too much Potassium – less common than hypokalemia and More dangerous Common Causes Renal failure (Rarely occurs in person with normal renal function) Signs and symptoms Bradycardia (high K+ suppresses SA node) Tremors, twitching N/V EKG changes – Peaked T, PVC’s, arrhythmias Treat Kayexalate Insulin – pushes K+ back into the little house Dialysis
1. Calcium 1. Neuromuscular activity 2. Cardiac activity 3. Blood coagulation Etiology – how does this happen Surgical hypothyroidism Pancratitis Renal failure Vit. D deficiency 3. Signs and Symptoms 1. Hyperactive reflexes 2. Hypotension 3. Positive Trousseaus 4. Positive Chevostek’s 5. Prolonged QT interval Trousseau’s Sign - a test for latent tetany in which carpal spasm is induced by inflating a sphygmomanometer cuff on the upper arm to a pressure exceeding systolic blood pressure for 3 minutes. A positive test may be seen in hypocalcemia and hypomagnesemia. Treatment Oral route is safer IV: calcium gluconate over 5-10 minutes Monitor EKG
Etiology Ca is stored in the bones Essential for neuromuscular activity, cardiac activity, blood coagulation Cause of hypercalcemia Hyperparathyriodism (parathyroids control Ca levels by production of calcitonin Paget’s disease (bone metabolism disease) Excessive Vit. D intake Prolonged immobility Paget's disease is a metabolic bone disease that involves bone destruction and re-growth, which results in deformity. Signs and symptoms Anorexia, N/V Coma Flaccid muscles Arrhythmias and cardiac arrest Treatment Fluids IV aredia, pamidronate
Magnesium Intracellular reactions and utilization of ATP CNS transmissions Cardiovascular tone Etiology Pancreatitis Cirrhosis GI losses Alcoholism Calcium gluconate administration Treatment of Diabetic ketoacidosis S/S Increased deep tendon reflexes Chvostek’s/Trousseaus signs pos EKG changes Pre-ecclampsia Condition that is not fully understood Occurs in about 8% of pregnancies Symptoms are: high BP, edema in extremities, protein in urine, aches, blurred vision and possible seizures Treat – with Magnesium sulphate IV – acts as vasodialator (causes flushing and hypotension)
Etiology (not common) Renal disease Hypercalcemia Adrenal insufficiency Signs and symptoms Flushing Low BP, slow pulse Respiratory depression Hypoactive reflexes Increase in Mg depresses skeletal muscles and nerve function Most common cause is renal failure Bradycardia due to depression of acetylcholine Decreased respirations,coma, ECG changes
#2 – Because of the retention of CO2, the clinical profile of respiratory acidosis includes decreased pH < 7.35, PaCO# - > 42 with varying levels of HCO3 related to hypoventilation Option #1 is respiratory alkalosis which occur because of blowing off CO2 resulting in decreased level of acid and retention or production of HCO3 resulting in pH > 7.45 Option #3 is Metabolic acidosis because of high H+ or loss of HCO3 often caused by diarrhea, or retention related to kidney failure Option #4 – metabolic alkalosis caused by increased HCO3, or loss of H+, related to vomiting, gastric suction or loss of upper GI secretions