Fluid and Electrolyte balance

1. Fluid and Electrolyte balance Dr Sanjay De Bakshi MS;FRCS

2. Distribution of body water

3. Distribution of Body Water (contd.) • Neonates---75 to 80%. • Infants and children------65%. • Adults:- Males----60% Females---50%.

4. Distribution of Body Water (contd.) Body water is also inversely proportional to body fat.

5. Measurement of Body water and its Components

6. WATER EXCHANGE

7. WATER EXCHANGE(60 to 80kg man.)GAIN

8. WATER EXCHANGELOSS

9. MRI OF THE BRAIN SAGGITAL SECTION

10. 1 CORPUS CALLOSUM 13 3rd VENTRICLE 1a BODY 14 4th VENTRICLE 1b SPLENIUM 15 CEREBELLUM 1c GENU 1d ROSTRUM 2 LATERAL VENTRICLE 3 FORNIX 4 SEPTUM PELLUCIDUM 5 ANTERIOR COMMISURE 1a 1 2 1b 4 2 1c 3 1d 5 13 6 10 9 8 11 7 14 15 12 6 POSTERIOR COMMISURE 7 OPTIC CHIASM 8 HYPOTHALAMUS 9 MAMMILLARY NUCLEUS 10 CEREBRAL AQUEDUCT 11 DECUSSATION OF SUP. CEREBELLAR PEDUNCLE 12 PONS

11. Center for Water Balance

12. Flow of CSF • Lateral ventricles • Interventricular foramen (Monro) • 3rd ventricle • Cerebral aqueduct (Sylvius) • 4th ventricle • Central canal of spinal cord (Magendie and Luschka) • Subarachnoid space • Around brain • Around spinal cord

13. Function of Cerebrospinal Fluid • Cushions and supports brain • Transports respiratory gases, nutrients, wastes • Ependymal cells • Produced by the choroid plexus • Network of capillaries in each ventricle • Materials for CSF taken from blood • Replaced every 8 hours • Via projections from the subarachnoid space into the dural sinuses • Removed during a spinal tap for diagnosis of meninges or brain infections

14. Control of Water Intake • In humans, the thirst center is located in the anterior hypothalamus. The primary stimuli for thirst are hypertonicity and hypovolemia. • Osmoreceptors in the anterior wall of the third ventricle mediate the osmotic regulation of thirst. • Hypovolemia and hypotension stimulate thirst through the activation of low-pressure (venous) and high-pressure (arterial) vascular stretch receptors. Impulses from these receptors are transmitted by the vagus and the glossopharyngeal nerves to the medulla and from there to the hypothalamus. • In addition, the hypothalamus is stimulated directly by angiotensin II.

15. The hypothalamus and thirst response • THIRST CENTER STIMULATED BY:- • Increased Plasma Osmolarity • Increased thirst • Increased ADH • Decreased ECF Volume • a) Decreased stimulation of Atrial Type B receptors Increased sympathetic stimulation b) Decreased pressure at Renal Afferent Arteriole Stimulation of Angiotensin mechanism c) Low Sodium causes stimulation of the Renin-angiotensin System Increased Angiotensin II Vasoconstriction ADH Thirst Aldosterone

16. Renin angiotensin mechanism Low pressure at the afferent arteriole. Low sodium at the macula densa Increased Renin sectretion from the JG apparatus JG cells, Macula densa & Lacis (Polkissen)cells AngiotensinI Angiotensin Angiotensin II ACE

17. Fluid exchange

18. Fluid dynamics at the capillary CHP = Capillary Hydrostatic Pressure COP = Capillary Osmotic Pressure IFHP = Interstitial Fluid Hydrostatic Pressure IFOP =Interstitial Fluid Osmotic Pressure

19. Osmotic pressure • DEFINITION:- Is the pressure that drives water across the semipermeable cell membrane and isdependant on those substances which fail to pass through the membrane. • The total number of osmotically active particles is approximately 290 to 310 mO in each component.

20. Some more definitionsWhat is a Mole and a Molar Solution? • Molarity- A mole is a gram molecular weight of a substance. NaCl=58.5gm; C6H12O6=180gm. • 1 molar solution = gram molecular weight of the substance in a litre of solution. 1 mol= 1000mmol.

21. Some calculations • OSMOTIC PRESSURE depends on the actual number of particles in solution. • Therefore, 1 gram mol weight of NaCl ie. 58.5gm of NaCl in 1 litre exerts how much of osmotic pressure? 58.5gm NaCl exerts--------------2000mosmol/L 9gm NaCl exerts--------------2000 x 9 58.5 = 307.69 mosmol/L 180gm C6H12O6 exerts------------1000mosmol/L 50gm C6H12O6 exerts-----------1000 x 50 180 = 277.77 mosmol/L

22. INTRACELLULAR CATIONS ANIONS PLASMA CATIONS ANIONS ECF CATIONS ANIONS Na = 10 HPO4 = 150 Na = 142 Cl = 103 Na = 144 Cl = 114 K = 150 SO4 = 150 K = 4 HCO3 = 27 K = 4 HCO3 = 30 Mg = 40 HCO3 = 10 Ca = 5 SO4 = 3 Ca = 3 SO4 = 3 Prt = 40 Mg = 3 PO4 = 3 Mg = 2 PO4 = 3 Org Ac = 5 Org Ac = 5 Prt = 16 Prt = 1 Urea = 24 IONIC COMPOSITION OF DIFFERENT BODY FLUIDS

23. Calculating fluid replacement

24. What is the rule for calculating maintenance fluids for 24 hours? • 100/50/20 rule • 100mL/kg for the first 10 kg • 50mL/kg for the next 10 kg • 20mL/kg for every kg over 20

25. How much fluid for a 70 kg man? • 100/50/20 rule • 100mL/kg for the first 10 kg • 50mL/kg for the next 10 kg • 20mL/kg for every kg over 20 • 1000ml (100 X10) + • 500ml (50 X 10) + • 1000ml (20 x 50) • GRAND TOTAL = 2500ml. ?

26. How much fluid for a 40 kg woman? • 100/50/20 rule • 100mL/kg for the first 10 kg • 50mL/kg for the next 10 kg • 20mL/kg for every kg over 20 • 1000ml (100 X10) + • 500ml (50 X 10) + • 400ml (20 x 20) • GRAND TOTAL = 1900ml. ?

27. Replacement of losses • Pre-operative or pre-admission • Ongoing losses • Nasogastric aspirate • Vomit, diarrhoea • Stoma, drains, fistula etc • Most ‘surgical ‘ ongoing losses are rich in sodium and should be replaced with 0.9% saline

28. Insensible losses • Faeces approximately 100 ml/ day • Lungs approximately 400 ml/ day • Skin approximately 600 ml/ day

29. Daily requirement of Electrolytes • Sodium: 1-2 mEq/kg/d • Potassium: 0.5-1 mEq/kg/d • Calcium: 800 - 1200 mg/d • Magnesium: 300 - 400 mg/d • Phosphorus: 800 - 1200 mg/d

30. Daily requirements of major electrolytes {Rule of 1,2 & 3s} • Sodium 1mEq/kg/ day • Potassium 1mEq /kg/day • Chloride 1mEq/kg/ day • Calcium 2g/ day • Magnesium 300mEqday

31. Case StudyCalculate type and quantity of Fluid • 70 kg man in third post-operative day following an uncomplicated ventral hernia operation. • No postoperative vomiting, • Has passed 1000ml of urine, • Has received 500ml of antibiotics and analgesics • Sodium requirement = 70 to 140 mEq/d • Potassium Requirement = 35 to 70 mEq/d • Fluid required = {2500+1000+400+600}-500ml. • WHAT FLUIDS? ?

32. Case Study : A healthy young lady of 32yrs. Undergoes an appendicectomy. She is fine till the third post-operative day, when she has three grand mal seizures. She recieves 20mgm of diazepam and 250mgm of Phenytoin IV and undergoes laryngeal intubation with mechanical ventilation. CAUSE:- Infused 5% Dextrose only on Day 1. Plenty of plain water orally on Day 2. ?

33. Case Study : • Her body weight is 46kgs. • Sodium concentration-112mmol/litre • Potassium concentration-4.1 mmol/litre • Serum osmolality-228mOsm/kg of water. • Urine osmolality-510mOsm/kg of water. Plan of treatment? Withhold water. Infusion of 3 per cent Sodium Chloride. Intravenous administration of 20mgm of Furosemide.

34. Pathophysiology: Serum sodium is regulated by ADH Free water absorption from the Kidneys • thirst, • ADH, • the renin-angiotensin-aldosterone system, and • variations in renal handling of filtered sodium. Increases in serum osmolarity above the normal range (280-300 mOsm/kg) stimulate hypothalamic osmoreceptors, which, in turn, cause an increase in thirst and in circulating levels of ADH. K+ Vol Aldosterone Absorption of sodium at the distal renal tubule.

35. INTAKE 80 –100 mmols/day (5-6gms) Secretions 1000mmols/day Faeces 5mmols/day Plasma Sodium (136-144mmols) Kidney PCT 75% LH 22% DCT 4-5% CD 2-3% Loss in Urine (70-90mmols/day) NORMAL SODIUM BALANCE GI TRACT

36. Clinical features of hyponatraemia • Anorexia • Nausea and vomiting • Difficulty concentrating • Confusion • Lethargy • Agitation • Headache • Seizures

37. Hypovolemichyponatremia- sodium and free water are lost and replaced by inappropriately hypotonic fluids, such as tap water, half-normal saline, or dextrose in water • Excess fluid losses (eg, vomiting, diarrhea, excessive sweating, GI fistulas or drainage tubes, pancreatitis, burns) that have been replaced primarily by hypotonic fluids • Acute or chronic renal insufficiency • Salt-wasting nephropathy • Cerebral salt-wasting syndrome H2O Na H2O

38. H2O Na Euvolemichyponatremiaimplies normal sodium stores and a total body excess of free water. This occurs in patients who take in excess fluids. • Psychogenic polydipsia, often in psychiatric patients • Administration of hypotonic intravenous (IV) or irrigation fluids in the immediate postoperative period • Infants who may have been given inappropriate amounts of free water

39. Hypervolemichyponatremiaoccurs when sodium stores increase inappropriately. • History of hepatic cirrhosis, congestive heart failure, or nephrotic syndrome, in which patients are subject to insidious increases in total body sodium and free water stores • Uncorrected hypothyroidism or cortisol deficiency • SIADH • Consumption of large quantities of beer or use of the recreational drug MDMA (ecstasy) Na H2O

40. HYPONATRAEMIA GI or Skin

41. Effect of hyponatraemiaand its correction Water gain Normal Immediate effect of hypo state Loss of organic osmolytes Osmotic demyelination Proper therapy Water Rapid adapta-tion Slow adapta-tion Incorrect Loss of Na, K, Cl. therapy

42. Treatment of Hyponatraemia In asymptomatic patients: When symptoms are absent, the focus of therapy should be on identifying and correcting the underlying cause of hyponatraemia. • If hypovolemic on the basis of clinical assessment and urine sodium concentration, normal saline solution should be administered initially to correct the extracellular fluid volume deficit. • If hypervolemic, salt and water restriction is key. • If euvolemic and hyponatremic, therapy consists primarily of water restriction. When the cause of the syndrome of inappropriate ADH is unknown or not treatable, other methods can be used, including increased dietary protein and salt and use of urea, loop diuretics and, rarely, demeclocycline hydrochloride (Declomycin).

43. Treatment of Hyponatraemia In symptomatic patients: Patients with acute symptomatic hyponatremia are candidates for aggressive treatment • Hyponatremia can be corrected with administration of hypertonic saline solution (3%) at a rate of about 1 mL/kg per hour. A loop diuretic may be added to enhance water excretion if urine osmolality is greater than 300 mOsm/kg. • The serum sodium concentration should be raised no more than 25 mEq/L in the first 48 hours, at a rate of no more than 2 mEq/L per hour, and the target goal should be 120 to 125 mEq/L. With use of this combination therapy, sodium lost in the urine is replaced with an equal amount of sodium in a smaller volume. Treatment with hypertonic saline solution is advocated only for patients with severe hyponatremia who have profound neurologic symptoms.

44. ? Case Study : • An elderly lady of 63yrs. Undergoes a difficult resection- anastomosis for a gangrenous segment of small intestine, which was incarcerated under a post-operative band. • Her abdomen is distended, she is obtunded, and her bowel sounds are absent. • The tongue is red and swollen, skin turgor is diminished and she is not totally coherent. • She has mild orthostatic hypotension

45. Case Study : Straight X-ray • Serum sodium- 158mmol/liter • Serum Potassium-4.0mmol/liter • Body weight is 60kg. HYPERNATRAEMIA DUE TO HYPOTONIC SODIUM LOSS CT Scan

46. TYPES OF HYPERNATRAEMIA In general, hypernatremia is due to too little water, too much salt, or a combination thereof. H2O H2O Na H2O Na Na

47. THUMB RULE:- • Serum sodium levels of more than 190 mEq/L usually indicate long-term salt ingestion. • Serum sodium levels of more than 170 mEq/L usually indicate DI. • Serum sodium levels of more than 150-170 mEq/L usually indicate dehydration.

48. Hypovolemic hypernatremia (ie, water deficit >sodium deficit) • Extrarenal losses - Diarrhea, vomiting, fistulas, significant burns • Renal losses - Osmotic diuretics, diuretics, postobstructive diuresis, intrinsic renal disease • Adipsic hypernatremia is secondary to decreased thirst. This can be behavioral or, rarely, secondary to damage to the hypothalamic thirst centers. Na H2O

49. Hypervolemic hypernatremia (ie, sodium gains >water gains) • Hypertonic saline • Sodium bicarbonate administration • Accidental salt ingestion • Mineralocorticoid excess (Cushing syndrome) Na H2O

50. Euvolemic hypernatremia • Extrarenal losses - Increased insensible loss (eg, hyperventilation) • Renal losses - Central DI, nephrogenic DI • These patients appear euvolemic because most of the free water loss is from intracellular and interstitial spaces, with less than 10% occurring from intravascular space. • Typically, symptoms result if serum sodium is more than 160-170 mEq/L. H2O Na