Body Fluids and electrolite balance-1.pptx

Body fluids and electrolytes balance, the silent fundamentals of human wellbeing.

1. Body Fluids and electrolyte balance Presented by: Dr Fiston Kamabu

2. Introduction Changes in fluid volume and electrolyte composition occur: preoperatively, intraoperatively, postoperatively, and in trauma and sepsis Important to recognize and understand how to manage changes.

3. The Normal Distribution of Fluids Total body water (TBW ): 60% of the lean body mass (women 50%), about 40-42L Intracellular fluid volume (ICF ): 60% of TBW, about 25L Extracellular fluid volume (ECF ): 40% of TBW (and 20% of body weight), about 15-17L

4. Extracellular Fluid (ECF) Extracellular fluid further consists of: Plasma water (IVF) 3L Extravascular fluid 12-14L Interstitial fluid (ISF) 8-9L Transcellular water 1L Bone and dense connective tissue 4-5L

5. The TBW and ECF in full term neonates: 75% and 35% of body weight respectively. By 2yrs: 65% and 20%. The ICF changes little. The interstitial fluid is separated from the plasma only by a capillary membrane which permits rapid transfer of all except protein molecules and cellular elements. The interstitial fluid and plasma therefore act as one compartment.

6. Transcellular fluid comprises GIT secretions, CSF, joint fluids and eye fluid . The ECF is referred to as ‘inland sea’ bathes the cell mass and carries to it nutrients and oxygen while removing waste products of excretion It does to the cells what the sea does to the fish .

7. Composition Fluid Compartment

8. Osmotic Pressure Facilitates water movement across cell membranes Determined by concentration of solutes on either side membrane (mainly sodium, glucose and urea/blood urea nitrogen(BUN)) Calculated serum osmolality= 2 * sodium + (glucose/18) + (BUN/2.8) Osmolality is maintained between 290 and 310

9. Electrolytes Electrolytes are in 2 compartments in the body, intra and extracellular zones. Intracellular ions: potassium most important cation in the cells, about 140mmol/l while in extracellular, its 3.6-5.2mmol/l. Other ions are Mg 15mmol/l, Na 8mmol/l, phosphates 26mmol/l and proteins 9mmol/l. Extracellular ions: Na is the most important ion 135-145mmol/l others ions are K, Ca, HCO3 Mg and CL

10. The Normal Distribution of Fluids Distribution of fluid across the cell membrane depends on: High protein content of cells (oncotic pressure) Semi-permeability of the cell membrane The Na-K pump, which is energy dependent (keeps sodium out of the cells, and hence water since water movements follow sodium movements)

11. The Normal Distribution of Fluids Movements of fluid across the capillary bed depends on: Hydrostatic pressures at arterial and venous ends Semi-permeability of the capillary bed Plasma oncotic pressure Interstitial pressure

12. Normal Exchange of Fluid and Electrolytes Healthy person comsumes average of 2000mL water/day Daily losses average 800-1200mL urine, 250mL stool, 600mL insensible (skin, lungs) To clear products of metabolism, kidneys must excrete 500 to 800mL urine per day despite intake Average salt intake is 3-5grams/day

13. Normal Fluid Homeostatic Mechanisms Total body fluids are broadly balanced by intake and output Intake is an expression of drinking as a result of thirst which is the function of chemoreceptors which detect increased circulating and cellular osmolarity

14. Normal Fluid Homeostatic Mechanisms Total body fluids are broadly balanced by intake and output Volume receptors are less sensitive to fluid depletion as regards increasing intake, but play a role in reducing fluid losses in the kidneys, and stimulating vasoconstriction and an increased cardiac output to compensate for the shrunken circulating volume

15. Normal Fluid Homeostatic Mechanisms In hypovolaemia, volume receptors in the heart and great vessels stimulate the hypothalamus - hypophysis system: ADH for water retention ACTH and hence Aldosterone for salt retention

16. The Renin-Angiotensin-Aldosterone Mechanism The enzyme ‘Renin’ is released from the kidney in response to a low volume This in turn converts Angiotensinogen to Angiotensin I, which is further hydrolyzed to Angiotensin II in the lungs Vasoconstriction Aldosterone is then released from the adrenal cortex Salt and water retention

17. Daily fluids and electrolyte requirements Fluid intake is derived from both exogenous (consumed liquids) and endogenous (released during oxidation of solid foodstuffs)fluids. Fluid losses occur by four routes: Lungs . About 400 ml of water is lost in expired air each 24 hours . This is increased in dry atmospheres or in patients with a tracheostomy, emphasizing the importance of humidification of inspired air. Skin . In a temperate climate, skin (i.e. sweat) losses are between 600 and 1000 ml day–1 .

18. Faeces . Between 60 and 150 ml of water are lost daily in patients with normal bowel function. Urine . The normal urine output is approximately 1500 ml day–1 and, provided that the kidneys are healthy, the specific gravity of urine bears a direct relationship to volume. A minimum urine output of 400 ml day–1 is required to excrete the end products of protein metabolism.

19. The Normal Daily Fluid Turnover

20. The Normal Daily Fluid Requirements

21. Ionic Composition of Body Fluids

22. Cont. A typical daily maintenance fluid regimen would consist of a combination of 5% dextrose with either Hartmann’s or normal saline to a volume of 2 litres . The following are the approximate daily requirements of some electrolytes in adults: sodium: 50–90mMday–1; potassium: 50mMday–1; calcium: 5mMday–1; magnesium : 1mMday–1.

23. In addition to maintenance requirements:- ‘ R eplacement ’ fluids are required to correct pre-existing deficiencies and ‘ Supplemental ’ fluids are required to compensate for anticipated additional intestinal or other losses.

24. The nature and volumes of these fluids are determined by: A careful assessment of the patient including pulse, blood pressure and central venous pressure if available. Clinical examination to assess hydration status (peripheries, skin turgor , urine output and specific gravity of urine), urine and serum electrolytes and haematocrit Estimation of losses already incurred and their nature: for example , vomiting, ileus, diarrhea, excessive sweating or fluid losses from burns or other serious inflammatory conditions.

25. Estimation of supplemental fluids likely to be required in view of anticipated future losses from drains, fistulae, nasogastric tubes or abnormal urine or faecal losses. • When an estimate of the volumes required has been made, the appropriate replacement fluid can be determined from a consideration of the electrolyte composition of gastrointestinal secretions. Most intestinal losses are adequately replaced with normal saline containing supplemental potassium

26. Common Parenteral Fluids Crystalloids: - contain Na as the main osmotically active particle - useful for volume expansion (mainly interstitial space) - for maintenance infusion - correction of electrolyte abnormality

27. Cont. Isotonic crystalloids - Ringer’s lactate, 0.9% NaCl - only 25% remain intravascularly Hypertonic saline solutions - 3% NaCl Hypotonic solutions - D5W, 0.45% NaCl - less than 10% remain intra- vascularly , inadequate for fluid resuscitation

28. Colloid Solutions: Contain high molecular weight substances do not readily migrate across capillary walls Preparations - Albumin: 5%, 25% - Dextran - Gelifundol - Haes-steril 10%

29. Solutions Volumes Na + K + Ca 2+ Mg 2+ Cl - HCO 3 - Dextrose mOsm/L ECF 142 4 5 103 27 280-310 Lactated Ringer’s 130 4 3 109 28 273 0.9% NaCl 154 154 308 0.45% NaCl 77 77 154 D5W D5/0.45% NaCl 77 77 50 406 3% NaCl 513 513 1026 6% Hetastarch 500 154 154 310 5% Albumin 250,500 130-160 <2.5 130-160 330 25% Albumin 20,50,100 130-160 <2.5 130-160 330 Common parenteral fluid therapy

30. Colloids vs. Crystalloids Stay in circulation Plasma Expand May disrupt Clotting Direct and Dilutional ? Cellular acidosis Lesser Volume All fluid compartments No direct effect on Clotting ? Cellular function better preserved Greater volume c. X3

31. System Volume Deficit Volume Excess Generalized Weight loss Weight gain   Decreased skin turgor Peripheral edema Cardiac Tachycardia Increased cardiac output   Orthostasis/hypotension Increased central venous pressure   Collapsed neck veins Distended neck veins     Murmur Renal Oliguria —   Azotemia   GI Ileus Bowel edema Pulmonary — Pulmonary edema Signs and Symptoms of Volume Disturbances

32. Composition of GI secretions Type of Secretion Volume (mL/24 h) Na (mEq/L) K (mEq/L) Cl (mEq/L) HCO 3 – (mEq/L)   Stomach 1000–2000 60–90 10–30 100–130 Small intestine 2000–3000 120–140 5–10 90–120 30–40 Colon — 60 30 40 Pancreas 600–800 135–145 5–10 70–90 95–115 Bile 300–800 135–145 5–10 90–110 30–40

33. Body System Hyponatremia Central nervous system Headache, confusion, hyperactive or hypoactive deep tendon reflexes, seizures, coma, increased intracranial pressure Musculoskeletal Weakness, fatigue, muscle cramps/twitching GI Anorexia, nausea, vomiting, watery diarrhea Cardiovascular Hypertension and bradycardia if significant increases in intracranial pressure Tissue Lacrimation, salivation Renal Oliguria Body System   Hypernatremia   Central nervous system Restlessness, lethargy, ataxia, irritability, tonic spasms, delirium, seizures, coma Musculoskeletal Weakness Cardiovascular Tachycardia, hypotension, syncope Tissue Dry sticky mucous membranes, red swollen tongue, decreased saliva and tears Renal Oliguria Metabolic Fever

34. Hyperkalemia Causes Increased intake:    Potassium supplementation    Blood transfusions    Endogenous load/destruction: Hemolysis or rhabdomyolysis Crush injury Gastrointestinal hemorrhage Increased release:    Acidosis    Rapid rise of extracellular osmolality (hyperglycemia or mannitol) Impaired excretion:    Potassium-sparing diuretics   Renal insufficiency/failure

35. Hyperkalemia Symptoms GI Nausea Vomiting Intestinal colic Diarrhea Neuromuscular: Weakness Ascending paralysis Respiratory failure Cardiovascular: EKG changes: Early peaked T waves Late widened QRS, flat p-waves, prolonged PR interval, v-fib Cardiac arrest

36. Hypokalemia Causes Inadequate intake:    Dietary Potassium-free intravenous fluids Potassium-deficient TPN Excessive potassium excretion: Hyperaldosteronism    Medications GI losses:    Direct loss of potassium from GI fluid (diarrhea)   Renal loss of potassium (gastric fluid, either as vomiting or high nasogastric output)

37. Hypokalemia Symptoms GI Ileus Constipation Neuromuscular Weakness Fatigue Diminished tendon reflexes Paralysis Cardiovascular EKG changes U waves, T wave flattening, ST segment changes, arrhythmias Cardiac arrest

38. Calcium Daily Intake 1-3grams Adjust total serum calcium down by 0.8g/ dL for every 1g/ dL decrease in albumin Acidosis increases ionized fraction of calcium due to decreased protein binding Hypercalcemia Think primary hyperparathyroidism in outpatient setting vs malignancy in inpatient setting Sx : neurologic impairment, musculoskeletal weakness and pain, renal dysfunction, nausea, vomitting , abdominal pain, hypertension, arrhythmias, worsening digitalis toxicity EKG changes: shortened QT interval, prolonged PR and QRS interval, increased QRS voltage, T wave flattening and widening, AV block->arrest

39. Hypocalcemia Causes: pancreatitis, massive soft tissue infections, renal failure, pancreatic or small bowel fistulas, hypoparathyroidism, TSS, tumor lysis syndrome, abnormal magnesium levels, massive blood transfusion with citrate binding Sx : paresthesias face and extremities, muscle cramps, stridor, tetany, seizures, hyperreflexia, Trousseau’s sign, Chvostek’s sign, decreased cardiac contractility, heart failure EKG changes: prolonged QT interval, T wave inversion, heart block, V-fib

40. Phosphorus Abundant in metabolically active cells and tightly controlled by renal excretion Hyperphosphatemia Causes: decreased urinary excretion, increased intake, hypoparathyroidism, hyperthyroidism, rhabdomyolysis, tumor lysis syndrome, hemolysis, sepsis, hypothermia, malignant hyperthermia Sx: Most asymptomatic but severe cases can lead to metastatic deposition of calcium-phosphorus complexes Hypophosphatemia Causes: decreased intake, intracellular shift (respiratory alkalosis, insulin administration, hungry bone syndrome, refeeding syndrome) increased excretion, decreased GI uptake due to binders, Sx: Usually asymptomatic until severe- cardiac dysfunction and muscle weakness when high energy phosphates unavailable

41. Magnesium Hypermagnesemia Causes: severe renal insufficiency, iatrogenic- in antacids, laxatives and TPN, severe trauma, severe acidosis, thermal injury Sx: nausea, vomiting, weakness, lethargy, hyporeflexia, hypotension and cardiac arrest EKG changes: increased PR interval, widened QRS complex, elevated T waves Hypomagnesemia Causes: starvation, alcoholism, prolonged IVF tx, inadequate TPN, diuretic use, amphotericin B, primary aldosterism, diarrhea, malabsorption, acute pancreatitis Sx: neuromuscular and CNS hyperactivity, similar to hypocalcemia EKG changes:prolonged QT and PR intervals, ST segment depression, flattening or inversion of p waves, torsades de pointes , arrythmias

42. Acid-Base Disorders Acute Uncompensted Chronic (Partially Compensated) Type of Acid-Base Disorder pH PCO 2 (Respiratory Component)   Plasma HCO 3 – a (Metabolic Component)   pH PCO 2 (Respiratory Component)   Plasma HCO 3 – a (Metabolic Component)   Respiratory acidosis N Respiratory alkalosis N Metabolic acidosis N Metabolic alkalosis N ?

43. IVF Composition Solution Na CL K HCO 3 –   Ca Mg mOsm Extracellular fluid 142 103 4 27 5 3 280–310 Lactated Ringer's 130 109 4 28 3   273 0.9% Sodium chloride 154 154         308 D 5 0.45% Sodium chloride   77 77         407 D5W             253 3% Sodium chloride 513 513         1026

44. Alternative Resuscitative Fluids Solution Molecular Weight Osmolality (mOsm/L) Sodium (mEq/L) Hypertonic saline (7.5%) — 2565 1283 Albumin 5% 70,000 300 130–160 Albumin 25% 70,000 1500 130–160 Dextran 40 40,000 308 154 Dextran 70 70,000 308 154 Hetastarch 450,000 310 154 Hextend 670,000 307 143 Gelofusine 30,000 NA 154

45. Correcting Hypernatremia Treat the associated water deficit Water deficit (L)= serum sodium-140 x TBW 140 Estimate TBW as 50% lean body mass men and 40% women Correct no more than 1 mEq/hr or 12 mEq/day to avoid cerebral edema and brain herniation

46. Correcting Hyponatremia Free water restriction and occasionally administration of sodium Correct by no more that 0.5mEq/L/hr or maximum increase of 12 mEq/L/day to avoid central pontine myelinolysis

47. Correcting Hyperkalemia Potassium removal      Kayexalate      Oral administration is 15–30 g in 50–100 mL of 20% sorbitol      Rectal administration is 50 g in 200 mL of 20% sorbitol    Dialysis Shift potassium      Glucose 1 ampule of D 50 and regular insulin 5–10 units IV  Bicarbonate 1 ampule IV Counteract cardiac effects      Calcium gluconate 5–10 mL of 10% solution

48. Correcting Hypokalemia Serum potassium level <4.0 mEq/L:    Asymptomatic, tolerating enteral nutrition: KCl 40 mEq per enteral access x 1 dose    Asymptomatic, not tolerating enteral nutrition: KCl 20 mEq IV q2h x 2 doses    Symptomatic: KCl 20 mEq IV q1h x 4 doses    Recheck potassium level 2 h after end of infusion; if <3.5 mEq/L and asymptomatic, replace as per above protocol

49. Correcting Hypomagnesemia Magnesium level 1.0–1.8 mEq/L:    Magnesium sulfate 0.5 mEq/kg in normal saline 250 mL infused IV over 24 h x 3 d    Recheck magnesium level in 3 d Magnesium level <1.0 mEq/L:    Magnesium sulfate 1 mEq/kg in normal saline 250 mL infused IV over 24 h x 1 d, then 0.5 mEq/kg in normal saline 250 mL infused IV over 24 h x 2 d    Recheck magnesium level in 3 d If patient has gastric access and needs a bowel regimen:    Milk of magnesia 15 mL (approximately 49 mEq magnesium) q24h per gastric tube hold for diarrhea

50. Correcting Hypocalcemia Normalized calcium level <4.0 mg/dL:    With gastric access and tolerating enteral nutrition: Calcium carbonate suspension 1250 mg/5 mL q6h per gastric access; Recheck ionized calcium level in 3 d    Without gastric access or not tolerating enteral nutrition: Calcium gluconate 2 g IV over 1 h x 1 dose; Recheck ionized calcium level in 3 d

51. Correcting Hypophosphatemia Tolerating enteral nutrition: Neutra-Phos 2 packets q6h per gastric tube or feeding tube    No enteral nutrition: KPHO 4 or NaPO 4 0.15 mmol /kg IV over 6 h x 1 dose Recheck phosphate level in 3 d Phosphate level <1.0 mg/ dL :    Tolerating enteral nutrition: KPHO 4 or NaPO 4 0.25 mmol /kg over 6 h x 1 dose Recheck phosphate level 4 h after end of infusion; If <2.5 mg/ dL , begin Neutra-Phos 2 packets q6h    Not tolerating enteral nutrition: KPHO 4 or NaPO 4 0.25 mmol /kg (LBW) over 6 h x 1 dose; recheck phosphate level 4 h after end of infusion; If <2.5 mg/ dL , then KPHO 4 or NaPO 4 0.15 mmol /kg (LBW) IV over 6 h x 1 dose  

52. Preoperative Fluid Therapy For the first 0 to 10 kg Give 100 mL/kg per day For the next 10 to 20 kg Give an additional 50 mL/kg per day For weight >20 kg Give an additional 20 mL /kg per day Just an initial guideline, does not replace pre-existing deficit or ongoing losses No routine fluid choice. Surgeon/Anesthesia preference

53. Intraoperative Fluid Therapy Usually at discretion of Anesthesia team Be sure to note what (colloid vs crystalloid) and how much is given, particular blood or blood products and pressors Postoperative Fluid Therapy Take into account NPO status, ongoing losses from NGT, drains, fistua , etc Type of fluid can be surgeon or service dependent

54. Special Circumstances Neurologic Patients SIADH- hyponatremic with elevated urine sodium & osmolality Tx with fluid restriction and diuretics & underlying problem Diabetes Insipidus-hypernatremia with dilute urine Central (ADH secretion) vs nephrogenic (ADH responsiveness) Vasopressin tx Cerebral Salt wasting Dx of exclusion Refeeding Syndrome Insulin release leads to cellular uptake of electrolytes (Phosphate, Magnesium, Calcium, Potassium) Start feeding slowly at 20kcal/kg/day Acute Renal Failure Cancer Patients

55. references www.pubmedscholarlyjournals.com Bailey & Love’s, SHORT PRACTICE of SURGERY, 26 th Edition.