DR. PRAMILA BAJAJ SR. PROF. & HEAD

1. Perioperative Fluid Management DR. PRAMILA BAJAJ SR. PROF. & HEAD DEPTT. OF ANAESTHESIA, ADDITIONAL PRINCIPAL, RNT MEDICAL COLLEGE, UDAIPUR (RAJ.) www.anaesthesia.co.inanaesthesia.co.in@gmail.com

2. Perioperative Fluid Management Fluid & electrolyte management paramount in surgical patient. Change in Fluid (Fl.) & Electrolyte (El.) Composition Pre.op Post op. In response to trauma and sepsis

3. Distribution of Body Fluids • Helps us understand the subject. • Total body water : 50-60% of total body weight. • Relationship constant for an individual; reflection of body fat.

4. Distribution of Body Fluids • Water in muscle & solid organs > Water in fat & bones  young, lean adults – greater% of TBW than elderly / obese. Av. young adult male : 60% water of TBWt Av. young adult female : 50% water of TBWt, b/c of high adipose / fat. • Estimates of TBW  Up by 10% in malnourished Down by 10-20% in obese. • New born infants : 80% water of TBW  Decreased to 65% by 1 year, then constant.

5. Fluid Compartments • Total Body Water - Extracellular Fluid (20%); Intracellular Fluid (40%), • TBW – ECF = ICF

6. Normal Water Balance How body maintains its water volume? Kidneys : A major role. Oral / iv fluids & urine output : Important parameters of body fluid balance.

7. Insensible fluid input = 300 ml water due to oxidation insensible fluid loss = 500 ml through skin (400 ml through lung & 100 ml through stool) Fluid loss – Fluid input = 1000 – 300 ml = 700 ml • Insensible loss  in : Fever, Hypermetabolism, Hyperventilation • Sweating : Active process : Loss of electrolytes & water 1. Moderate sweating : 500 ml 2. Severe Sweating High fever 3. Burns Abd. Surgery 1000 – 1500 ml 500-3000 ml

8. Normal Water Balance ………… • Kidney must excrete about 500-800 ml urine / day (irresp. of oral intake) • Daily Sodium intake : 3-5 gm/d. • Balanced achieved by kidneys : In hyponatremia : Salt excreted <1 mEq/d In Salt wasting kidneys: >5000 mEq/d.

9. Composition of Fluid Compartments ECF compartment : Balance between electrolytes ECF ICF Principal Cation : Na+ K+, Mg2+ Principal Anion : Cl- & HCO3- Phosphate & Prot. ATP driven Na K Pump ECF ICF Conc. grad.

10. Imp. Points to Remember : • Proteins : important contributors to Osmolality • Movement of water across compart. is free but that of proteins and ions restricted. • Even distribution of water in all compartments. • Sodium confined to ECF because of osmotic & eIectrolyte properties • Sodium containing fluids  distributed in ECF  Vol. of IV and interstitial sp. as much as 3 times of plasma.

11. Definitions • What is Osmotic pressure?- Movement of water across C.M. depending primarily upon osmosis. - Determines distribution of water among different fluid compartment. (ICF & ECF) • generated by solution proportional to no. of particles / unit volume of solvent. • does not depend upon type, valence and weight of the particles To generate O.P.  Solute must be unable to cross C.M. Unit  osmoles (osm) or milliosmoles (mosm). E.g.. : One mmol of Nacl  2mosm (one each from Na+ & Cl-)

12. Define Osmolality, Effective Osmolality & Osmolarity 2. Osmolality • Determined by amt. of solute diss. in a solvent (water) measured in wt (kg) Determinants: Conc. of sodium, glucose, urea (BUN) Calculation : Serum osmolality = 2Na+ + Glucose + BUN 18 2.8 • Osmolality of ECF and ICF b/w 290-310 Osm in each compartment

13. 3. Effective Osmolality • Determined by solutes which do not freely permeate cell wall and hold water within ECF Effective Osmolality = 2xNa (mEq/L) + Glucose (mg/dl)/18 • Glucose accounts for only 5 mOsm/kg in effective osmolality.  plasma Na concentration is the determinant of the plasma osmolality. 4. Osmolarity: Determined by amt. of solute dissolved in a solvent (water) measured in vol. (litre). • Concentration of solution of a solute diss. in 1 litre of solvent is expressed as mOsm/L.

14. Concentration of Electrolytes: Expressed in terms of chemical combining activity or equivalents. Univalent ion (Sodium) ; 1 Meq = 1 Mmol Bivalent ion (Mg) ; 2 Meq = 1 Mmol

15. Paediatric Surgery How are infants and children different from adults? • Fluid Management : A critical element in paed. surgery b/c infants & children sensitive to even small degree of dehydration Higher requirement for water & electrolytes / KgBw. Inability to excrete water load due to immature kidneys  Overload. • Complex surgical procedures Rapid change in fluid requirement Frequent assessment and modification of fluid therapy.

16. Paediatric Surgery ………… • In O.T. rapid change in req. during: - Conduct of Anaesth. & Surg. - Change in temperature - Metabolism & vol. shift (due to trauma, hemorrhage, tissue exposure)  Intracompartmental fluid shift • Requires fluid replacement with sol. to compensate for energy, water, protein & electrolyte losses. • Anaesthetist : Alert for - obvious fluid loss - Hidden fluid loss (insensible loss) - Third Space loss

17. Physiological Considerations • Proportion of ECF/ICF change with age. • Body cells, surrounding fluid in electrical equilibrium • TBW Vol. & Fluid exchange rate vary with age. • Before birth, nutrition demands met through placental transfer. NFT infant - enough fluid reserve to last till full oral breast feed.

18. Physiological Considerations … …..

19. Immature Infants : Higher% of TBW and ECF Total blood volume of a newborn infant 8.5% of B.W.

20. Interstitial Space fluid filtered High cir. vol. : Vas. Comp.  interstitial sp. (reservoir) fluid filtered Low cir. vol. : Interstitial sp.  Vas. comp.  buildup circulatory vol. Adolescence: FEFV 27-30% [Inter. space vol. + Plasma vol.] 20% + 7-10% Full term infant : FEFV 45%

21. What is the importance of transcellular (III Sp.) fluid? • Non functional extracellular fluid • Unavailable pool of water  formed by transudation from cells and EC space • E.g. Fluid within GIT formed during- Int. Obst. Ascitis Urine Pleural effusion • Fluid in III space loss from FEFV • Fluid preferred for replacement : Ringer lactate

22. Intracellular Fluid • Isotonic Solution  Cell Vol. constant due to free movement of water from within cells • Hypotonic Solution  Inward water movement  Increased cell volume • Intracellular fluid bound to protein • Energy required for Potassium (inside cell) & Sodium transport (outside cell).

23. Describe the renal physiology in neonates. • Postnatal shift in body fluid med. by Na+ and H2O excretion by immature kidneys. • Sodium and water excretion by immature kidneys  Postnatal: Mediated by shift in body fluid • Urine Vol.  1st day – 0-68 ml 7th day – 40-300 ml • At birth GFR 25% of adult rate (20 ml min-1 1.73m-2) • Rapid  in 2 wks; slower  to adult rate by 2 yrs of age • Infants can handle twice the (N) vol. load b/c -ve effects of low GFR compensated by +ve effects of low concentrating & high diluting capacity Add conc. capacity of infant well below adult.

24. Renal Physiology in Neonates ……. Concentrating capacity : (Max. osmolality 500-600 (well below adults) Osm/kg) in response to water Adult : (1200 mOsm/ kg) Diluting capacity : low in dehydrated infants If water loaded  diluting capacity well above adults (Osmolality 30-50 mOsm/kg) • Fasting newborn (72 hours)  Minimum elevation of BUN & Na. (Loss of BW 13%). • 8% decrease in BW; Neg. N2 balance even when fluid given at 50ml/kg/day/ or unlimited amt. of breast milk. • Milk feed  Positive N2 balance & weight gain Wilkinson et al. 1962, Lancet 1983

25. Electrolyte Physiology Sodium Physiology : Variable therefore inaccurate indicator of hydration. • Daily requirement (Term infant)  2-5 meq kg-1 day-1 • Term infants retain Sodium when in negative Na balance like adults. •  cap. to excrete Na when in positive balance. • Ac. change in balance  Gross variation in blood pressure, Intracerebral hemorrhage. • PPV & use of PEEP  ed Natriuresis, ed vasopressin, ed water retention

26. Daily Electrolyte Requirements for Paediatric patients

27. What are the special features of CVS physiology in infants? • Immature myocardium & S.N.S.  Propensity to hypovolaemia greater in neonates / infants. • [Myocardial contractility + vas. tone & compliance]  less variable  tachycardia  Pri. comp. mech. during  vol. • Excess  HR  C.O.  • Anaesth. effect  Further depression of myocard.  Hypovolemia exaggerated maintenance of effective vas. vol. in paed. patient essential to sustain circulatory function and vital organ perfusion in peri-op. period.

28. Hepatic Function Hepatic function immature • Carbohydrate reserves accumulate in last TM of pregnancy : limited stores in pre-term neonates. • Most pre-term neonate : Require 10% dextrose infusion to prevent hypoglycemia in early perinatal period.

29. Hepatic Function ………. Clinically significant hypoglycemia : Full term neonate : < 30 mgdl-1 Pre term infant First 3 days  < 20 mgdl-1 After 3rd day  < 40 mgdl-1 Treatment : Ac. hypoglycemia : Bolus 0.5-1.0 g/kg-1 iv glucose followed by infusion 5-6 mg kg-1 as maintenance infusion Monitor serial blood glucose.

30. Hepatic Function ………. Response to surgical trauma :  Catechol.  glucocort.  blood glucose. Hypoglycemia : - Unusual during preop. fasting in children - Uncommon during surgery. - Not easily recognized during anaesth. • Dextrose in patient with prolonged fast prevents ketosis,  protein catabolism post operatively. • Continue glucose inf. commenced in OT until patient awake and oral intake established.

31. What are the fluid management protocols in infants ? Divided into 3 phases : • Deficit therapy • Maintenance therapy • Replacement therapy Deficit Therapy : Management of fluid / electrolyte loss prior to surgery : Three components • Estimate Severity of dehydration • Determine fluid deficit • Repair the deficit

32. Assessment of dehydration severity in neonates & infants

33. Fluid Management ….…. History, Clinical and Evaluation Important Confirmation by : • Serum osmolarity and serum sodium • Acid-base status, Serum pH, Base deficit • Serum Potassium compared with pH • Urine Output [To rule out ATN] Hyponatremic Dehydration : Serum Osmolarity <270 m.Osmol-1 Serum Na+ <130mEq/L

34. Fluid Management ….…. Isonatremic Dehydration : Serum Osmolarity 270-300 m.Osmol-1 Serum Na+ 130-150 mEq/L Hypernatremic Dehydration : Serum Osmolarity >310 m. Osmol-1 Serum Na+ >150 mEq/L • Initiate treatment for deficit before investigation available • Initiation with a bolus of NS over 10-12 min to improve circulation and restore renal perfusion

35. Fluid Management ….…. • Patient with known contraction alkalosis : 50% dextrose with 0.9% NS (Reasonable fluid of choice) • Patient with known met. acidosis : 250 ml of 0.9% NS + 28 ml of 7.5% Soda bicarbonate solution + 232 ml of 5% dextrose. This gives approx. Dextrose 1.2% Sodium 149 mEq Chloride 115 mEq Sod. Bicarbonate 25 mEq

36. Fluid Management ….…. • Lactate / Acetate containing solution aggravate met. acidosis because of failure of formation of bicarbonate from its precursors due to poor circulation status. • Febrile response to volume contraction – Due to decrease in skin blood flow  Decrease heat dissipation. • Hyperosmolarity  Increased threshold for sweating  Increase calorie and fluid requirement

37. Fluid Management ….…. Fluid deficit due to overnight fasting : • Advocated to prevent risk of pul. aspiration during anaesthesia • Children :  residual gastric vol.,  pH; Clear fluids allowed upto 2 hours before surgery. [Sphinter W.M. 1990: Anaesth Intensive Care 18:522-526] • Sips of fluid :  peristalsis but no gastric secretion if protein absent. • H2 blockers :  gastric pH,  gastric vol. Sertherland AD et al. 87, Can J. Anaesth 34. 117-121.

38. Fluid Management ….…. Current recommendations : Clear fluids : 2 hours Milk : 4 hours General Rule : Preop. Fluid deficit = Maint./hr. x Hrs of fluid restriction Before Surgery

39. Maintenance fluid requirements in neonates & infants: Daily and hourly

40. Composition of commonly used intravenous fluids

41. Maintenance Fluid Therapy • Meets ongoing fluid & electrolyte demands during surg. • Does not include blood loss / third space loss into gut or interstitial space. • Maintenance Fluid covers: - Insensible loss [evaporative loss] - Urinary loss • Insensible loss  Solute free loss of water through skin & lungs, usually 30-35% of total maint. req.

42. Maintenance Fluid Therapy Determinants of Insensible loss : Ambient Temp. Humidity Gest. Age Resp. pattern Exposed surface area • Ventilation with humidified gases   insensible loss. • In premature infants and patients with D. insipidus  Obligatory production of dil. urine  Appropriate  in maintenance fluid required. • In excess ADH secretion  Patients unable to  urine osmolality to 300 mOsm need to  vol. of maint. fluid Gastroschisis

43. Intravenous fluid requirements in Infants Day 1 of life 2 ml/kg per hour Day 2 of life 3 ml/kg per hour Day 3 of life 4 ml/kg per hour Intravenous fluid requirements in children <10 Kg 10 ml/kg per day 10-20 Kg 1000 ml + (50 ml/kg per day for each kg over 10 kg) >20 Kg 1500 ml + (20 ml/kg per day for each kg over 20 kg) Wt. 10 12 14 16 18 20 30 mL/h 40 45 50 55 60 65 70

44. Replacement of blood loss In children, all blood loss should be replaced. Done with packed RBCs/whole blood/Crystalloid/ Colloids Davenport’s law : <10% blood loss : No blood req. 10-20%  Consider case by case >20% Consider packed RBCs/Whole blood Replacement : Crystalloid 3 ml for each ml of blood loss Ensure adequate oxygenation Minimum hematocrit 30% older children 40% neonates acceptable Sacrococcygeal Teratoma

45. Intraoperative Fluid Management • Responsibility of an anesthesiologist • Sufficient fluid required to compensate for NBM hrs + insensible loss during op. • Loss considerable during major abdominal / thoracic surgery • In most cases 10 ml/kg/hr of Ringer lactate in D5 in water • Blood loss : Weighing sponges Suction bottle accumulation • Actual loss more because of blood in drapes and op. field

46. Intraoperative Fluid Management …….. • In a child with normal Hb pre-op. : Whole blood / packed RBCs infusion if blood loss 10% of B.V. • FFP/Albumin in extreme dissection without blood loss. • Emergency : Trauma / G.I. Bleed  Continue Pre-op. resuscitation with rapid transfusion during op. • Prolonged hours of op.  Monitoring Urine Output  Serum Electrolyte & blood glucose  Hematocrit and blood gases.

47. Post Op-Period - Optimum replacement and maintenance pre. and intraop.  child in fluid and electrolyte balance postop. Immediate Post-Op. • Drainage from chest tube/ intraperitoneal drains measured & replaced with blood plasma • GIT drainage collected  Sample for electrolytes  Measured vol. replaced at intervals of 4-12 hours. • Satisfactory oral intake : 3-5 days in most cases.

48. Review of Finer Points • Why fluid therapy needs special consideration in children? • 1) Greater insensible loss 2) Greater urinary loss 3) Larger turn over 4) Inadequate expression of thirst 5) Easy fluid overload 6) Small total volume required 7) Diffusion volume and distribution of body water

49. Disturbance in Fluid Balance in adults Extracellular vol. deficit : Common fluid disorder in surgical patients. Acute deficit associated with CVS & CNS signs. Chronic deficit :  in skin turgor and sunken eyes + CVS & CNS signs.

50. Signs and Symptoms of Volume Disturbances