Fluid and electrolyte therapy

1. Fluid and electrolyte therapy Dr Ashoka Acharya Consultant Paediatrics Warwick hospital

2. Dehydration • Abnormal fluid losses overcoming renal compensating mechanisms • Main aim of compensation is maintaining plasma volume and BP at all cost • Loss of homeostasis –hypovolaemic shock • Principal causes: diarrhoea and DKA

3. Definition • Parenteral or oral fluid therapy • Maintain/restore volume/composition of body fluids • Takes account of corrective physiological mechanisms

4. Fluid therapy: Goal • Achieve normal intracellular and extracellular chemical environment • Thereby optimise cell and organ function

5. Factors determining requirements • Maintenance fluid: replaces usual losses of fluid and electrolytes • Deficit replacement fluid: designed to replace abnormal losses due to disease • Supplemental fluid: replaces measured or estimated continuing abnormal losses

6. Factors determining requirements • Each component is calculated separately • Fluid therapy often based on gross estimates. Deficit often overestimated. • Repeated clinical reassessment and adjustment needed

7. Maintenance fluid • Directly related to metabolic rate • endogenous water production • urinary solute excretion, • heat production- 25% lost through insensible water loss)

8. Maintenance therapy • Generally 100ml per 100 calories used • Urine: obligatory loss = 65 ml • Insensible water loss = 35 ml • Sweating =23 ml • pulmonary =12 ml

9. Maintenance therapy: increased requirements • Increased activity (30%) • Fever (1°C increases by 12%) • Dry environment • Hyperventilation • ELBW- transcutaneous losses 100-200ml/kg/day • Overhead heaters, phototherapy units

10. Maintenance fluid-decreased requirements • Comatose • Hypothermia • Highly humidified atmospheres • Humidified ventilator circuits

11. Maintenance fluid: increased renal losses • High solute load (DM, Mannitol, high protein diets) • ADH insufficiency • Central • Nephrogenic • Primary • Secondary: sickle cell, obstructive uropathy, chronic PN, reflux nehropathy, hypokalemia, hypercalcemia, drugs, psychogenic polydipsia

12. Maintenance fluid: decreased urinary losses • SIADH • Renal failure • Replace insensible water loss +urine output ml/ml with free water

13. Maintenance sodium needs • Increased: CF, salt losing nephropathy, chronic PN, obstructive uropathy, diuretics, fistulas, diversions, NG drainage • Decreased: Hepatic failure, cardiac failure, renal failure, nephrotic syndrome

14. Maintenance potassium needs • Increased: Chronic renal disease, gastric and intestinal drainage, chronic diuretics, laxative abuse • Decreased or nil: Acute renal failure, adrenal insufficiency, severe metabolic acidosis

15. Normal maintenance requirements (holiday and segar

16. Maintenance fluids: route • Oral or parenteral • Calories: usually as 5% dextrose • TPN

17. Deficit Therapy: factors affecting • Oral or parenteral intake • Pathologic body losses • Physiologic body losses • compensatory attempts to modify volume and composition • Net effect- Deficits from different causes often similar in magnitude and composition

18. Infant: moderately severe dehydration

19. Deficit therapy • Severity: Magnitude and rapidity • Estimated from recent weight or clinical features • Type: Relative loss of water and electrolytes mainly sodium • pathophysiology • therapy • prognosis

20. Deficit therapy: Types • Isotonic: sodium 130-150 mmol/l, no fluid shifts, 80% of cases • Hypotonic: sodium <130mmol/l, ECF to ICF, 10% cases • hypertonic:sodium>150 mmol/l, ICF to ECF, 10% cases

21. Deficit Therapy:types and history • D and V for days, good intake, low salt • Cholera, bacillary dysentery • High fever, poor intake • Infant with NDI, poor water intake • Intake of dilute milk formula • Intake of boiled semiskimmed milk • wrongly prepared ORS

22. Assessment of deficit severity

23. Assessment of severity: contd

24. Calculation of deficit fluid • Percentage dehydration x wt in kg x 10= ml of fluid • eg: 7% dehydration of infant weighing 10 kgs = 7x10x10=700 ml

25. Clinical features • Signs represent depletion of ECF • Plasma: tachycardia, fall of BP, postural hypotension, cool extremities, increased CRT, decreased urine • Interstitial fluid: Tenting of skin • Transcellular fluid: dry mouth, sunken eyes, decreased tears, sunken fontanel

26. Signs of dehydration • Mild dehydration: no signs • Severe dehydration: Prolonged capillary refill time,dry mucosa, decreased skin turgor, general appearance are the most sensitive and specific • Acidosis: Kussmaul’s breathing • Hypokalemia: weakness, abd dist, ileus,cardiac arrhythmias • hypocalcemia and magnesemia: tetany, muscle twitching

27. Signs V's type of deficit • Hyponatremic: increased severity of signs for amount of fluid loss • Hypernatremic: Less signs, irritable, hypertonic, hyperreflexic, warm extremities, doughy skin

28. Lab tests • FBC: Increased Hb, PCV • Serum Na: type of dehydration • serum K: gut loss, acidosis; needs ECG monitoring • Serum HCO3: acidosis- D&V, DKA: alkalosis-Pyloric stenosis, NG drainage • Serum chloride: changes with Na, chloride diarrhea • Urea/creatinine: elevated with decrease in GFR, may be normal! • Urine: infection screen, specific gravity, electrolytes • stool: culture, electrolytes

29. Treatment • Oral therapy: mild to moderate dehydration • Parenteral therapy: • severe dehydration • Persistent vomiting • Refusal of oral intake • Abdominal distension • No caregiver to give close attention

30. Stages of treatment • Initial therapy: expand ECF volume • Subsequent therapy: replace deficit/maintenance/ongoing losses • Final therapy: Return to normal composition/establish oral feeds/correct potassium deficit

31. Commonly available crystalloids: isotonic

32. Isotonic crystalloid fluids

33. Hypertonic crystalloids

34. Colloid fluids

35. Initial therapy • Normal saline or Hartmans solution regardless of type of deficit • 20 ml/kg rapid bolus, repeat if needed • IV, intraosseous line • Never use hyponatremic fluids • Adequate crystalloid dose better than colloid • No potassium till urine output established

36. Subsequent therapy • Calculate over 8 hour intervals • Deficit replaced over 24 hours but can be done over 8 to 12 hours except HYPERNATREMIA • Early K+ replacement after urine output • Maximum K+, 40 mmol/l (ITU 80 mmol/l)

37. Isonatremic dehydration • Deficit plus maintenance plus ongoing losses calculated • Use 0.45%saline with 2.5% or 5% dextrose for subsequent therapy • Give 50% in first 8 hours and remaining over 16 hours • Subtract boluses from total fluid • Assess clinical state regularly and modify if needed

38. Hyponatremic dehydration • Extra Na deficit (mmol/l)=desired Na-actual Na x 0.6 x Wt kgs • Manage as for isonatremic dehydration but replace deficit Na over 12-24 hours • Raise serum Na by 10 mmol/l/day • If Na <120mmol/l and seizures give 3% Nacl 1ml/min max 12ml/Kg

39. Hypernatremic dehydration: complications • Cerebral haemorrhage, thrombosis, subdural effusion- permanent handicap, renal vein thrombosis • During treatment- cerebral oedema, seizures, hypocalcemia • High mortality if Serum Na >160mmol/l

40. Hypernatremic dehydration • Always use isonatremic boluses • Slow correction of deficit over 48 to 72 hours • Aim to decrease serum Na by 10 mmol/l/day • Use 0.18saline or 0.45% saline with dextrose for subsequent therapy • Seizures: 3% saline, mannitol, hyperventilation, calcium gluconate

41. Supplemental fluids • Consider composition of fluid lost • D&V: 0.45% saline • Cholera:0.9% saline • NG tube aspiration: 0.45 to 0.9% saline plus potassium • Gut losses: same

42. Composition of external losses

43. Appearance, activity Skin turgor BP Intake/output chart U&E, glucose blood gas CVP monitoring Eyeballs, tears CRT Weight Urine Specific gravity Urine output ECG monitoring Assessment of response

44. Oral rehydration therapy • Mild to moderate dehydration • Types of ORS: high sodium- 90mmol/l, low Na- 50 mmol/l • Glucose facilitated sodium absorption, sucrose less effective, rice based effective

45. ORS • Use 50ml/kg in mild and 100ml/kg in moderate dehydration. • Give over 4 hours. Allow breast feeds and formula after rehydration. Reassess regularly. Small frequent feeds decrease vomiting. Consider NG tube. • Maintenance with 100ml/kg/day till diarrhoea stops • For on going losses add 10-15ml/kg/hr

46. Hyponatremia: sodium depletion • Renal losses: Preterm, ATN, Diuretics, mineralocorticoid deficiency, RTA • Extra renal loss: D&V, Burns, ascites, pleural effusion,csf drainage, NG drainage, CF • Nutritional deficits: Inadequate Na in TPN, oral intake

47. Hyponatremia: water excess • SIADH • Glucocotricoid deficiency • Hypothyroidism • Excess parenteral fluid • Psychogenic polydipsia • Tap water enema

48. Hyponatremia: excess Na and water • Nephrotic syndrome • Cirrhosis • Cardiac failure • Acute and chronic renal failure

49. Hyponatremia: asymptomatic • Water Excess: (urinary Na usually >20 mmol/l) fluid restriction, may be needed for days • Salt deficiency: (urinary Na <10 mmol/l, except in renal salt loss) Add salt to diet

50. Hypernatremia: sodium excess • Improperly mixed ORS or formula • Accidental or deliberate swap of salt for sugar in feeds • Excess Bicarb during resus • Hypernatremic enemas • Drugs: penicillin, gaviscon