fluid and electrolyte.pptx fluid and electrolyte balannce

Fluid and electrolyte

1. Jimma University medical Center Department of Surgery Lecture for year I Clinical students on Fluid and electrolyte management in surgical patients: BY; DR NEGASSA G (MD. GENERAL SURGEON)

2. Learning Objectives Defining the normal distribution of fluids and electrolytes in each body fluid compartment. Discussing the major electrolytes in maintenance of homeostasis. Identifying factors affecting normal fluid and electrolyte balance. Defining clinical presentation and utilizing laboratory data to detect common fluid and electrolyte imbalances. Discussing the common fluid and electrolyte imbalances in surgical patients and its management accordingly.

3. Course outline Introduction to fluid and electrolyte balance. Physiologic distribution of fluid and electolytes in fluid compartments. Physiologic regulation of volume and osmolality Etiologies of common fluid and electrolyte disturbances in surgical patients Common fluid and electrolyte abnormalities in surgical patients. Clinical evalution of patients with fluid and electolyte disturbances Highlights on management of the common fluid and electrolyte imbalances in surgical patients

4. Introduction to fluid and electrolyte In an average young adult male, TBW accounts for 60% of total body weight, whereas in an average young adult female, it is 50 %. Higher in newborns and at younger age.

5. Fluid compartments

6. Chemical composition of fluid Compartments

7. Plasma osmolality The plasma osmolality ( P- osm ) is determined by the ratio of plasma solutes and plasma water. Most of the plasma solutes are sodium salts with lesser contributions from other ions like potassium, calcium, glucose, and urea. The normal Posm is ~ 275 to 310 mosmol /kg . The plasma osmolality can be estimated from the following equation Posm = 2 x [Na] +[Glucose]/18 + [Urea ]/2.8 OR Posm = 2 x [Na] + [Glucose] + [Urea]

8. Normal Exchange of Fluid and Electrolytes

9. Osmoregulation and volume regulation Volume changes are sensed by both osmoreceptors and baroreceptors. H ypothalamus is stimulated to secrete vasopressin, which increases water reabsorption in the kidneys. These two mechanisms return the plasma osmolality to normal. The net result of alterations in renal sodium excretion and free water reabsorption is restoration of volume to the normal state.

10. Osmoregulation and volume regulation

11. Fluid and electrolyte in surgical patients Fluid and electrolyte management is paramount for the care of surgical patients. Surgical patients are prone to electrolyte disturbance Blood and body fluid loss Stress response to surgery Fluid and blood administration Underlying surgical diseases

12. Fluid and electrolyte in surgical patients Extracellular volume deficit is the most common fluid disorder in surgical patients and can be either acute or chronic. May be classified into three general categories: disturbances in a, Volume b, Concentration c, Composition Although each of these may occur simultaneously, each is a separate entity with unique mechanisms demanding individual correction

13. Signs and symptoms of fluid balance disturbance

14. Hyponatremia/Hypernatremia Hyponatremia ( <135 mlmol /L ) occurs when there is an excess of extracellular water relative to sodium. S odium depletion Dilutional. Clinical manifestations primarily have a central nervous system origin and are related to cellular water intoxication and associated increases in intracranial pressure Hypernatremia ( >146mmol/L ) usually occurs in patients with impaired thirst or restricted access to fluid .

15. Hyponatremia/Hypernatremia

16. Clinical manifestation of sodium abnormalities

17. Hyperkalemia / Hypokalemia The average dietary intake of potassium is approximately 50 to 100 mEq /day, which in the absence of hypokalemia is excreted primarily in the urine About 98% of potassium is stored in the cells. The intracellular and extracellular distribution of potassium is influenced by a number of factors, including surgical stress, injury, acidosis, and tissue catabolism .

18. Major causes of hyperkalemia

19. Major causes of hypokalemia

20. Hypercalcaemia /Hypocalcaemia The vast majority of the body’s calcium is contained within the bone matrix, with <1% found in the ECF . Daily calcium intake is 1 to 3 g/d. Serum calcium is distributed among three forms: protein bound (40 %), complexed with anions (10%), and ionized (50%). It is the ionized fraction that is responsible for neuromuscular stability and can be measured directly. Most of this is excreted via the bowel, with urinary excretion relatively low.

21. Hypercalcemia/ Hypocalcemia

22. Manifestations of potassium, Calcium and Magnesium abnormalities

23. Management of electrolyte abnormalities Hypernatremia : Treatment of hypernatremia usually consists of treatment of the associated water deficit. Water deficit (L) = S erum sodium −140 ×TBW 140 Once adequate volume has been achieved, the water deficit is replaced using a hypotonic fluid such as 5% dextrose, 5% dextrose in ¼ normal saline, or enterally administered water. The rate of fluid administration should be titrated to achieve a decrease in serum sodium concentration of no more than 1 mEq /h and 12 mEq /d for the treatment of acute symptomatic hypernatremia.

24. Management of electrolyte abnormalities Hyponatremia : In patients with normal renal function, symptomatic hyponatremia usually does not occur until the serum sodium level is ≤120 mEq /L. If neurologic symptoms are present, 3% normal saline should be used to increase the sodium by no more than 1 mEq /L per hour until the serum sodium level reaches 130 mEq /L or neurologic symptoms are improved.

25. Hyponatremia Rx Sodium deficit is calculated as: Desired Na+ -Serum Na+ ×TBW Chronic hyponatremia may have only subtle neurologic abnormalities with serum Na + level of 110 mEq /L .

26. Management of electrolyte abnormalities Hypokalemia Treatment for hypokalemia consists of potassium repletion, the rate of which is determined by the symptoms. Oral repletion is adequate for mild, asymptomatic hypokalemia. If IV repletion is required, usually no more than 10 mEq /h is advisable in an unmonitored setting. Hyperkalemia: The goals of therapy include Reducing the total body potassium, Shifting potassium from the extracellular to the intracellular space. Protecting the cells from the effects of increased potassium. Dialysis should be considered when conservative measures fail.

27. Management of electrolyte abnormalities Hypocalcemia ; A cute symptomatic hypocalcemia should be treated with IV 10% calcium gluconate to achieve a serum concentration of 7 to 9 mg/ dL . Associated deficits in magnesium, potassium, and pH must also be corrected. Hypercalcemia ; Treatment is required when hypercalcemia is symptomatic, which usually occurs when the serum level exceeds 12 mg/ dL . The initial treatment is aimed at repleting the associated volume deficit and then inducing a brisk diuresis with normal saline

28. Management of electrolyte abnormalities

29. Fluid therapy Maintenance therapy maintenance fluid therapy is usually undertaken when the patient is not expected to be able to eat or drink normally for a prolonged period of time The goal of maintenance fluid therapy is to preserve water and electrolyte balance and to provide nutrition. Replacement therapy It is replacing pre-existing volume deficit and ongoing fluid loss There is no formula that can be used to accurately estimate the total fluid deficit. The rate of correction of volume depletion depends upon its severity.

30. Fluid Therapy The administration of maintenance fluids should be all that is required in an otherwise healthy individual who may be under orders to receive nothing by mouth for some period before the time of surgery. This does not, however, include replenishment of a pre-existing deficit or ongoing fluid losses.

31. Fluid therapy There are commercially available electrolyte solutions for parenteral administration. Crystalloids like lactated Ringer’s solution and normal saline are considered isotonic. Colloids also are used in surgical patients, and their effectiveness as volume expanders compared with isotonic crystalloids has long been debated.

32. Fluid therapy Due to their molecular weight, colloids are confined to the intravascular space, and their infusion results in more efficient transient plasma volume expansion. However, under conditions of severe hemorrhagic shock, capillary membrane permeability increases; and colloids enter the interstitial space , which can worsen edema and impair tissue oxygenation.

33. Fluid therapy An alternative approach is to replace the calculated daily water losses in urine, stool, and insensible loss with a hypotonic saline solution rather than water alone However, many surgical patients have volume and/or electrolyte abnormalities associated with their surgical disease. Acute volume deficits should be corrected as much as possible before the time of operation. Resuscitation should be guided by the reversal of the signs of volume deficit , such as restoration of acceptable values for vital signs, maintenance of adequate urine output (½–1 mL/kg per hour in an adult), and correction of base deficit.

34. E lectrolyte abnormalities in specific surgical patients SIADH- ADH secretion is considered inappropriate when it is not in response to osmotic or volume-related conditions. SIADH should be considered in patients who are euvolemic and hyponatremic with elevated urine sodium levels and urine osmolality. The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) can occur after head injury or surgery to the central nervous system, but it also is seen in association with administration of drugs such as morphine, nonsteroidals, and oxytocin, and in a number of pulmonary and endocrine diseases, including hypothyroidism and glucocorticoid deficiency. Correction of the underlying problem should be attempted when possible.

35. C ontd The goal is to achieve net water balance while avoiding volume depletion that may compromise renal function. Furosemide also can be used to induce free water loss. If hyponatremia persists after fluid restriction, the addition of isotonic or hypertonic fluids may be effective. In chronic SIADH, when long-term fluid restriction is difficult to maintain or is ineffective, demeclocycline and lithium can be used to induce free water loss.

36. Electrolyte abnormalities in specific surgical patients Diabetes Insipidus: Diabetes insipidus (DI) is a disorder of ADH stimulation and is manifested by dilute urine in the case of hypernatremia. Central DI is frequently seen in association with pituitary surgery, closed head injury, and anoxic encephalopathy. Nephrogenic DI occurs in association with hypokalemia, administration of radiocontrast dye, and use of certain drugs such as aminoglycosides and amphotericin B In patients tolerating oral intake, volume status usually is normal because thirst stimulates increased intake.

37. contd The diagnosis can be confirmed by documenting a paradoxical increase in urine osmolality in response to a period of water deprivation. In mild cases, free water replacement may be adequate therapy. In more severe cases, vasopressin can be added. However, serum electrolytes and osmolality should be monitored to avoid excess vasopressin administration with resulting iatrogenic SIADH.

38. Electrolyte abnormalities in specific surgical patients Cerebral Salt Wasting. Cerebral salt wasting is a diagnosis of exclusion that occurs in patients with a cerebral lesion and renal wasting of sodium and chloride with no other identifiable cause. Natriuresis in a patient with a contracted extracellular volume should prompt the possible diagnosis of cerebral salt wasting. Hyponatremia is frequently observed but is nonspecific and occurs as a secondary event, which differentiates it from SIADH.

39. Electrolyte abnormalities in specific surgical patients Refeeding Syndrome . Refeeding syndrome is a potentially lethal condition that can occur with rapid and excessive feeding of patients with severe underlying malnutrition due to starvation, alcoholism, delayed nutritional support, anorexia nervosa, or massive weight loss in obese patients. With refeeding, a shift in metabolism from fat to carbohydrate substrate stimulates insulin release, which results in the cellular uptake of electrolytes, particularly phosphate, magnesium, potassium, and calcium.

40. Electrolyte abnormalities in specific surgical patients S evere hyperglycemia may result from blunted basal insulin secretion. C an be associated with enteral or parenteral refeeding, and symptoms include cardiac arrhythmias, confusion, respiratory failure, and even death. U nderlying electrolyte and volume deficits should be corrected T hiamine should be administered before the initiation of feeding . Caloric repletion should be instituted slowly. Vital signs, volume status, and electrolytes should be closely monitored and any deficits corrected.

41. References

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