Fluid and Electrolyte Balance IN SURGICAL PATIENTS

1. Fluid and Electrolyte Balance IN SURGICAL PATIENTS By; Col. Abrar Hussain Zaidi

2. INTRODUCTION • One of the most critical aspects of patient care is management of the composition of body fluids and electrolytes. • Most diseases, many injuries, and even operative trauma have a great impact on the physiology of fluids and electrolytes in the body. • A thorough understanding of the metabolism of salt, water, and electrolytes and of certain metabolic responses is essential to the care of surgical patients.

3. A prerequisite: to understand the fluid and electrolyte management is; knowledge of the extent and composition of the various body fluid compartments.

4. INTRODUCTION BODY WEIGHT Fluids ----------60% Solids-----------40%

5. INTRODUCTION [cont] The main fluid in the body is water

6. Distribution of Water • 60% of body weight is body water. • water is distributed in three main compartments; separated from each other by cell membranes. a. The intracellular compartment - area within the cell. b. Extra-cellular compartments 1. The interstitial compartment (between and around cells) 2. The intravascular compartment

7. Distribution of Water

8. Distribution of Water • Plasma -------------5% • Interstitial ---------15% • Intracellular--------40% • Total ----------60 % Water • [Remaining -Solids - 40%:fat, protein, carbohydrates, minerals]

9. Distribution of Water • Infants have a higher percent of water than adults do as much as 77%. • The total water content of the body decreases most dramatically during the first 10 years • at old age, - only 45% of the total body weight. • Men tend to have higher percentages of water (about 65%) than women (about 55%) mainly because of their increased muscle mass and lower amount of subcutaneous fat. • Fat has less water content than any other body tissue. This also accounts for a lower than normal water percentage in obese people.

10. Regulation of fluid balance CONSIDERATIONS [in health or disease] • INTAKE VS OUT PUT • GASTROINTESTINAL TRACT • HYPOTHALAMUS/PITUTARYGLAND/Hormones • STARLING FORCES OF EQUILIBTIUM • KIDNEYS

11. Regulation of fluid balance • Water in the body is in a constant state of motion. Shifting between the three major fluid compartments of the body and in addition being continuously lost from, and taken into, the person. • In a normal, healthy human being : WATER INPUT = WATER OUTPUT. • Maintaining this ratio : is of prime importance in maintaining health. • Approximately 90% of the body's water intake comes via thegastro-intestinal tract. The remaining 10% is called metabolic water and is produced as the result of various chemical reactions in the cells of the body's tissues.

12. Regulation of fluid balance water loss from the body (healthy adult) • GASTRO-INTESTINAL TRACT (FAECES) 6% • LUNGS (WATER VAPOUR) 13% • SKIN (DIFFUSION & SWEAT) 19% • KIDNEYS (URINE) 62%

13. Regulation of fluid balance The mechanisms for the regulation of body fluids: 1- center in the hypothalamus. • receives input from the digestive tract • helps in the control of thirst. 2- Hypothalamic-pituitary axis 3- Anti Diuretic Hormone (ADH) Main regulator of fluid volume and extracellular osmolarity

14. Regulation of fluid balance • ADH - increases the permeability of the distal convoluted tubules and the collecting tubules in the kidneys. This allows more water to be reabsorbed in the kidneys. This is manifest if the body is short of fluid intake (such as during sleep) and results in a concentrated, darker coloured urine of reduced volume. Absence of ADH occurs when the individual is over-hydrated such as at a party if a lot of beer, cider, alcopops etc. are being drunk Here the urine is dilute, pale or colourless and of high volume. • Primary factors involved in the triggering of ADH production are osmoreceptors and baroreceptors (pressure receptors). • Secondary factors include, stress, pain, hypoxia, severe exercise, surgery (especially anaesthetics such as cyclopropane and nitrous oxide).

15. Regulation of fluid balance [cont] • A reduction of around 8-10% of body volume of water will result in ADH secretion.[ haemorrhage or excess perspiration in desert] • Volume changes-Sensed by- Pressure receptors located in the atria of the heart and the pulmonary artery and vein Relay their messages to the hypothalamus via the vagus nerve • Thirst response Changes in osmolality Chemoreceptors in hypothalamus Chemoreceptors in carotids

16. Regulation of fluid balance [cont] • The integrity blood vessels walls - barrier to the free passage of fluid between interstitial fluid and blood plasma. • These capillary walls are permeable to water and small solutes but impermeable to large organic molecules such as proteins. • The blood plasma tends to have a higher concentration of such molecules when compared to the interstitial fluid. • Much of this interstitial fluid is taken up by the lymphatic system and eventually finds its way back into the blood stream.

17. Regulation of fluid balance [cont] Starling forces • Water and small solutes such as sodium (Na+), potassium (K+), calcium (Ca++), etc. can be freely exchanged between the plasma and the interstitial fluid. • This exchange depends mainly upon the hydrostatic and osmotic forces of both of these fluid compartments. • Further regulation of these electrolytes is controlled by the action of the kidneys .

18. Regulation of fluid balance [cont] Starling forces • Cell membranes are completely permeable to water, • the effective osmotic pressures in the two compartments are considered to be equal. • Any condition that alters the effective osmotic pressure in either compartment results in redistribution of water between the compartments. • An increase in effective osmotic pressure in the extracellular fluid, which would occur typically as a result of increased sodium concentration, would cause a net transfer of water from the intracellular to the extracellular fluid compartment. • This transfer of water would continue until the effective osmotic pressures in the two compartments were equal. Conversely, a decrease in the sodium concentration in the extracellular fluid will cause a transfer of water from the extracellular to the intracellular fluid compartment. • Depletion of the extracellular fluid volume without a change in the concentration of ions will not result in transfer of free water from the intracellular space.

19. Regulation of fluid balance [cont] • The intracellular fluid shares in losses that involve a change in concentration or composition of the extracellular fluid, but shares only slowly in changes involving loss of isotonic volume alone. • For practical considerations, most losses and gains of body fluid are directly from the extra-cellular compartment.

20. Regulation of fluid balance [cont] Overall, there is near equilibrium between fluid forced out of the capillaries and the fluid absorbed back . [This is because the lymphatic system collects the excess fluid forced out at the artery end and eventually drains it back into the veins at the base of the neck.] • This is known as Starling's Law of the Capillaries. • A similar situation exists between the interstitial fluid and the intracellular fluid More complicated by the presence of ion pumps and carriers.

21. Homeostasis • All the body's fluid compartments are in osmotic equilibrium (except for transient changes). • The ions and small solutesthat constitute the ECF are in equilibrium with similar concentrations in each sub compartment. • The ECF volume is proportional to the total Na content.

22. Electrolytes • Electrolytes are the chemicals dissolved in the body fluid. The distribution has important consequences for the ultimate balance of fluids. • Sodium chloride is found mostly in extra-cellular fluid, while potassium and phosphate are the main ions in the intracellular fluid.

23. ELECTROLYTE DISTRIBUTION--- Total Positive ions -meq/liter Extra cellular Intracellular Function • Sodium 142 10 fluid balance, osmotic pressure • Potassium 5 160 Neuromuscular excitability acid- base balance • Calcium 5 - bones, blood clotting • Magnesium 2 26 enzymes

24. Electrolyte DistributionTotal Negative ions -meq/liter Extra cellular Intracellular Function • Chloride 105 2 fluid balance, osmotic pressure • Bicarbonate- 24 8 acid-base balance • Proteins 16 55 osmotic pressure • Phosphate- 2 149 energy storage • Sulfate 1 20 protein metabolism

25. Reminder • WATER—the main fluid • Electrolytes • State of equilibrium in the composition and concentration of the constituents in all compartments • Regulatory machanisms Sterling forces Role of hypothalamus and ADH Thirst Other hormones [aldosteron,steroids] Kidneys

26. Disorders of fluid & Electrolyte Balance CLASSIFICATION OF BODY FLUID CHANGES three general categories: (1) Disorders of volume (2) Disorders of concentration (3) Disorders of composition. Although these disturbances are separate entities –they are interrelated.

27. Disorders of fluid & Electrolyte Balance • Fluid volume excess • Fluid volume deficit • Electrolyte excess • Electrolyte deficit • Proportionate fluid and electrolyte excess/loss • Disproportionate fluid and electrolyte Excess/loss

28. Disorders of fluid & Electrolyte Balance • If an isotonic salt solution is added to or lost from the body fluids, only the the extracellular fluid volume is changed. The acute loss of an isotonic extracellular solution, such as intestinal juice, is followed by a significant decrease in the extracellular fluid volume and little, if any, change in the intracellular fluid volume. • Fluid will not be transferred from the intracellular space to refill the depleted extracellular space as long as the osmolarity remains the same in the two compartments. • Addition of hyper or hypotonic fluid to extra-cellular compartment –[ i.e. –change in osmolality] –leads to fluid shift[think of a small bag of salt put in water]

29. Disorders of fluid & Electrolyte Balance • If water alone is added to or lost from the extracellular fluid, the concentration of osmotically active particles changes. • If the extracellular fluid is depleted of sodium, water will pass into the intracellular space until osmolarity is again equal in the two compartments.

30. Disorders of fluid & Electrolyte Balance • The concentration of most other ions within the extracellular fluid compartment can be altered without significant change in the total number of osmotically active particles, thus producing only a compositional change. For instance, a rise of the serum potassium concentration from 4 to 8 mEq/L would have a significant effect on the myocardium, but it would not significantly change the effective osmotic pressure of the extracellular fluid compartment. • Normally functioning kidneys minimize these changes considerably, particularly if the addition or loss of solute or water is gradual.

31. Distributional change An internal loss of extracellular fluid into a nonfunctional space, such as the sequestration of isotonic fluid in a burn, peritonitis, ascites, or muscle trauma This transfer or functional loss of extracellular fluid internally may be extracellular (e.g., peritonitis), or intracellular (e.g., hemorrhagic shock), or both (e.g., major burns). In any event, all distributional shifts or losses result in a contraction of the functional extracellular fluid space.

32. Disorders of fluid & Electrolyte Balance • Most commonly---The problems occur when the level of sodium, potassium, or calcium is abnormal. • Electrolyte levels Often change when water levels in the body change. • Prefix "hypo-" Refer to a low levels • Prefix "hyper-" Refers to high levels For example, a low level of potassium is called hypokalemia, a high level of sodium is called hypernatremia.

33. Disorders of fluid & Electrolyte Balance • Older people more likely to develop abnormalities- more likely to become dehydrated or overhydrated. [the poor kidneys function ]. • Certain drugs- including diuretics and some laxatives, can increase the risk of developing electrolyte abnormalities. • Bed ridden state can increase the risk of developing electrolyte abnormalities because getting fluids and food may be difficult. • Chronic disorders fever, vomiting, or diarrhea can result in electrolyte abnormalities. • Operative trauma • Children very sensitive to fluid electrolyte changes

34. Diagnosis Electrolyte abnormalities Clinical examination Measuring electrolyte levels in blood or urine. Determine the cause of the abnormalities. • Treatment principles Treat the disorder causing the abnormality Assess the extent of disorder The extent of volume deficit/ecxcess The extent of electrolyte def./excess Assess the normal need for age /weight Define the mode of correction

35. FLUID disordersVolume changes A. Volume deficit/hypovolemia/Dehydration— • Volume of body fluids smaller than normal • Fluid output exceeds intake for an extended period • IF volume shrinks and not treated-- ICF volume and plasma volume decrease; B Volume excess/hypervolemia/Overhydration— • Volume of body fluids larger than normal; • Fluid intake exceeds output (for example, giving excessive amounts of intravenous fluids or giving them too rapidly )

36. FLUID/VOLUME - EXCESS OVERHYDRATION • When more fluid is consumed than can be excreted • The blood vessels overfill, and fluid moves from the blood vessels into the INTERSTITIAL SPACE causing edema. causes. • Cardiac failure - heart cannot pump blood adequately. • Kidney disorders -s cannot excrete enough water. • Antidiuretic hormone (Forces kidneys to retain more water). Overproduction of ADH caused by ; pneumonia and stroke and by drugs such as carbamazepine • Drugs, especially nonsteroidal anti-inflammatory drugs • Foods that are high in sodium – fluids retion /overhydration. Intravenous fluids or blood transfusions too rapidly.

37. FLUID/VOLUME - EXCESS OVERHYDRATION Clinical Features / Diagnosis • Oedema -Swelling in the legs or,in the lower back [if people are confined to bed]. D/D -chronic venous insufficiency -Lyphoedema • Dyspnea/Shortness of breath because fluid backs up in the lungs. worse when a person lies down The person may wake up shortly after lying • Puffiness of face

38. FLUID/VOLUME - EXCESS OVERHYDRATION Clinical Features / Diagnosis • Swelling and enlargement of organs-Cardio/hepatomegaly • The ENGORGMENT OF veins in the neck- JVP • CVP raised • Blood tests –Urea/ electrolytes or other substances that indicate how well the kidneys are functioning. • A chest x-ray –Hiler shadows fluid in the lungs. Cardiac size /heart failure .

39. FLUID/VOLUME EXCESS -Treatment a- Restrict the fluids b-Help the body excrete the excess water. Diuretics - kidneys to excrete the excess can be taken by mouth or I/V. Thiazides- often used first- mild and tend tohave few side effects. Frurosemide more potent. Potassium-sparing diuretic.

40. FLUID/VOLUME EXCESS -Treatment • Consume lesssalt also helps. If edema is due to poor circulation rather than overhydration • Increase physical activity . Usually, the blood vessel disorder that is causing poor circulation is treated. • Correct the cause of overhydration . • Give i/v fluids with caution • Treat Heart failure and kidney disorders. • Discontinue drugs if cause or limit its use- NSAIDs- arthritis • Overproduction of antidiuretic hormone –restrict fluid intake

41. FLUID/VOLUME - DEFICIT Dehydration Dehydration means not having enough water in the body.

42. FLUID/VOLUME - DEFICIT Dehydration Causes • Hot weather-sweating is increased • Fever-sweating +tachypnea • Diarrhea -water is lost in the stool • Vomiting - water is lost in the vomit • Diabetes - the body produces more urine • Kidney disorders- kidneys unable to concentrate urine as needed • Problems with walking, because getting water is difficult • Dementia- sense of thirst is reduced and the ability to get water impaired • Diuretics- increase the of water and salt excretion

43. FLUID/VOLUME - DEFICIT Dehydration Clinical features a-mild b-Moderate c-Severe

44. FLUID/VOLUME - DEFICIT Dehydration Clinical features-General • Dry skin • Fast pulse • low blood pressure • Low urine out put- [ The kidneys try to conserve -olig urea / an-urea] • Sunken eyes

45. FLUID/VOLUME - DEFICIT Dehydration Older people and Children More prone to dehydration • Sense of thirst is less • kidneys function less well • Can not help themselves

46. FLUID/VOLUME - DEFICIT Dehydration Clinical features Mild [10-20%] • May not be noticed • Skin and the membranes of the nose and eyes become dry. • Confusion / sluggishness. Tachycardia Moderate [ 20-30%] • Above symptoms + • Light-headedness Fainting • Postural hypotension • Oligurea + urine becomes dark. Severe [ 40% or above] • Above +Sunken eyes • Fall in blood pressure that can be life threatening. • Shock

47. FLUID/VOLUME - DEFICIT Dehydration Treatment involves replacing lost fluids. How rapidly -? Mild dehydration - 2 to 3 liters of water to drink over a period of a few hours. Moderate dehydration - Add some salt (sodium) and other electrolytes. Rehydration formulas (available without a prescription) Severe Dehydration -INTRAVENOUS REPLACEMENT. I/V also for those who cannot swallow, and those who are in a coma. If electrolytes must also be replaced, they are given intravenously with the fluids.

48. Concentration Changes/Electrolytes Disorders • Sodium is primarily responsible for the osmolarity of the extracellular fluid space: determination of the serum concentration of sodium generally indicates the tonicity of body fluids. • Hyponatremia and hypernatremia can be diagnosed on clinical grounds -- signs and symptoms generally are not present until the changes are severe. • Clinical signs of hyponatremia or hypernatremia occur early and with greater severity when the rate of change in extracellular sodium concentration is very rapid. • Changes in concentration should be noted early by laboratory tests and corrected promptly.

49. Disorders Of Sodium Balance Hyponatremia:result from • Not consuming enough sodium in the diet, • Excreting too much salt (in sweat or urine), or • Overhydration when a person drinks a lot of water without consuming enough salt (sodium chloride), typically during hot weather when a person also sweats more. The sodium level may decrease when large amounts of fluids that do not contain enough sodium are given intravenously. Diuretics help the kidneys excrete excess sodium and excess water. However, diuretics may cause the kidneys to excrete more sodium than water, resulting in a low sodium level.

50. Disorders Of Sodium Balance Hyponatremia [cont] • High ADH levels which signals the kidneys to retain water. caused by : pneumonia stroke drugs -anticonvulsants -carbamazepine) antidepressant -selective serotonin reuptake inhibitors (SSRIs—such as sertraline). • poorly controlled diabetes • heart failure, • liver failure, • Renal disorders.