1. Fluids & Electrolytes:
Created by: Sarah A. Murphy, MD
Edited by: Camille Henry, MD and
Venee Tubman, MD

2. Fluids and Electrolytes
Background – General Princinples
Maintenance Therapy
Replacement Therapy
Important Electrolyte Abnormalities

3. Fluids and Electrolytes: Background
There are normal and abnormal losses of fluids and electrolytes from the urine, sweat, feces and respiration
The kidney is important to:
balance losses and maintain blood volume
balance of electrolytes through excretion and reabsorption
Water follows Na

4. Body fluid compartments
Plasma
Intracellular
Cations
Anions
Na (140mEq/L)
Cl (104 mEq/L)
K+ (140)
Phos (107)
HCO3 (24)
Prot (40)
Protein (14)
Na (13)
K (4mEq/L)
HCO3 (10)
Ca (2.5 mEq/L)
Other (6)
Mg (7)
Mg (1.1 mEq/L)
Phos (2 mEq/L)
Cl (3)
Na is the main extra-cellular cation in the body and the body regulates intravascular volume by regulating the excretion or re-absorption of Na in the kidneys

5. Fluids and Electrolytes: Background
Regulation of intravascular volume:
1) In the kidney, the juxtaglomerular apparatus and macula densa sense decreased renal blood flow and release renin
Renin stimulates angiotensinogen  angiotensin I  angiotensin II (via ACE)
Angiotensin II causes release of aldosterone
Aldosterone increases distal renal tubule Na reabsorption
This leads to increased blood volume as water follows Na into blood

6. Fluids and Electrolytes: Background
2) Anti-diuretic hormone is released in hypovolemia  increases renal reabsorption of water
3) In the atria and aortic arch, baroreceptors sense volume depletion
Baroreceptors signal brain via CN IX and X  sympathetic discharge
Sympathetic tone regulates renal blood flow and leads to Na conservation
4) Atrial natriuretic peptide: regulates Na by increasing glomerular filtration rate and hydrostatic pressure (dilates afferent and constricts efferent arterioles of kidney)

7. Water Balance: Background
Water losses are sensed by an increase in plasma sodium and osmolality
Patients who are alert, have an intact thirst mechanism, and are able to drink water, will self-regulate
Patients who are unable to eat or drink have urinary, skin, and respiratory tract losses that must be replaced

8. Fluids and Electrolytes: Background
The goal of fluid therapy is to maintain the normal volume and composition of body fluids and correct abnormalities
In children, the most common abnormality is hypovolemia, primarily due to vomiting and diarrhea from gastroenteritis

9. Fluids and Electrolytes
There are two components to fluid therapy:
Maintenance therapy:
Replaces the ongoing losses of water and electrolytes (through urine, sweat, respiration, and stool)
Replacement therapy:
Replaces water and electrolyte deficits that result from abnormal gastrointestinal, urinary, or skin losses, bleeding, and third-space sequestration—the water and electrolyte deficits that have accrued via some perturbation in normal processes

10. Maintenance Therapy:
How do we determine what are the on-going losses that need to be replaced?

11. Calculating Maintenance Fluid Requirement
Putting these together, we come up with this formula for daily maintenance water requirements…
Per hour
Per day
Example: for wt 34kg
For each kg up to 10
4ml/hr
100ml/day
40ml/hr
1000ml/day
+ For each kg btw 10-20
2ml/hr
50ml/day
20ml/hr
500ml/day
+ For each kg above 20
1ml/hr
20ml/day
14ml/hr
280ml/day =
74ml/hr
1780ml/day
Daily water needs are based upon insensible losses from the respiratory tract and skin, and sensible losses from urine and stool
Water requirements are estimated by caloric energy expenditures:
We need approximately 100 mL of water for every 100 kcal/kg of energy expended

12. Maintenance Therapy:
What about important electrolytes like Na and K?

13. Maintenance Therapy:
Like water, electrolyte requirements are estimated based upon caloric energy expenditure
Sodium and chloride — the body needs to take in 4 to 6 meq/kg/day
Potassium — the body needs to take in 2 to 3 meq/kg/day
The majority of the electrolyte losses are from the urine, with a lesser contribution from sweat and stool losses

14. Special Situations: Newborns
premature infants have very thin skinincreased insensible losses
infants in isolettes are in a humidified environmentdecreased insensible losses.
newborns are born with excess body waterduring the first few days of life babies do not require full maintenance
Renal failure—decreased fluid requirement due to oliguria/anuria.
Burns—increased skin losses

15. Special Situations:
Fever—increased losses from increased skin loss and, in young children/infants, also due to increased respiratory rate that often accompanies fever
Ventilation—patients who are on ventilators (air is humidified) may have decreased respiratory losses. On the other hand, patients who are hyperventilating (e.g., in ketoacidosis, pneumonia) have increased respiratory losses.
GI pathology—patients with colostomies, malabsorptive disorders, resections of bowel, diarrhea, etc., will have increased water losses in stool because of inability to resorb water.

16. Replacement Therapy

17. Replacement is based on estimation of how much water and how much Na have been lost
Water Defecit can be estimated from:
Weight loss: (if known)
what was weight before and after illness?
Estimate percent dehydration from physical exam:
10 kg child is estimated to be 10 percent dehydrated:
Total fluid deficit: 10 percent of 10 kg = 1000 mL

19. Some more background information: Body fluid compartments
Intra Cellular Water: 40% of body weight
Extra Cellular Water: 20% of body weight (interstitial 15% and intravascular 5%)
Total Body Water:
Newborns 75%
Children 60%
Adult males 60%
Adult females 50%

20. Replacement therapy Na deficit:
0.6 x (weight in kg) x (140 – measured Na)
Total Body Water = 0.6 x weight in kg

21. Therapy 1: Oral Rehydration
Oral rehydration therapy is the best way to replace fluid losses if children are stable and can tolerate it
It is a slow process: giving 5cc of fluid by mouth every 5-10 minutes
With these small volumes, children generally do not vomit, and are eventually able to work up to larger volumes

22. Therapy 2: IV Rehydration
Give isotonic fluid boluses (normal saline) 20cc/kg and repeat up to two more times (total 60cc/kg) until the patient has stable vital signs and has improved clinically (i.e., less lethargic, more alert, etc.)
Estimate the fluid deficit using clinical exam (as in chart above) or, if available, a comparison of weights. Subtract the amount of boluses given from the estimated fluid deficit.
Replace the remaining amount as D5 1/2NS or D5 1/4NS given in addition to maintenance fluids—people will usually suggest replacing the first half of the deficit over the first 8 hours and the second half over the next 16 hours.

23. Therapy 3: IV Rehydration
Maintenance electrolyte requirements, like water requirements, are calculated based upon caloric energy expenditure.
Sodium and chloride:
3meq/100 mL of water per day
Potassium:
2 meq/100 mL of water per day
Practically speaking, when you are giving maintenance fluids, this turns into 20-40mEq/L of Na+ and Cl- and 10-30mEq/L of K+.
Fluid resuscitation should use isotonic fluid (like LR, NS) or blood, albumin, etc., that will stay in the intravascular space.

24. Components of Hydration Fluids
CHO
(g/dL)
Na+
(mEq/L) K+
Cl-
HCO3
mOsm/kg NS
154
308 LR
0-10
130 4
109 28
273
D5 ½ NS c 20K 5 77 20 97
D5 ¼ NS c 10K 38 10 48
ORS 2 90 80 30
310
Gatorade
5.9 21
2.5 17
377
AppleJuice
11.9
0.4 26
700

25. Types of Losses
Insensible losses (skin and respiratory tract) which are directly related to energy expenditure (i.e., kcal/d).
Skin losses: about 2/3 of total, increase with increased body temperature (e.g., fever).
Resp losses: about 1/3 of total, increase with tachypnea.
Vomit:
H2O, H+, Cl-
Stool: water loss from stool is neglible in healthy children. Diarrhea = loss of H2O, K+, Na, Cl, HCO3.
Urine: assuming normal kidney function should not cause electrolyte “loss” (i.e., kidney will maintain nl serum lytes)

26. Therapy: General Rules
For newborns during the first 24h of life, we generally give only dextrose-containing solutions (i.e., D10W) until we are sure that their kidneys are functioning.
For patients <10kg, we generally use D5 ¼ NS c 10mEq/L of KCl
For patients >10kg, we use D5 ½ NS c 20 mEq/L of KCl.

27. A Note about Hypo/HyperNa
Most patients with Na between will tolerate adjustment of their Na by routine re-hydration as above
Rapid correction of hypoNa can lead to central pontine myelinolysis or Sz’s
Rapid drop of Na in patients with hyperNa can lead to cerebral edema
The “0.6” in the following equations is the % of BW that is water (0.75 in infants)
The “140” in the following equations relates to the desired Na-level– to slow down the rate of correction, you can change this value.

28. Hyponatremic Dehydration
Calculate Na-defecit: 0.6 x Weight in kg x (measured Na)
This Na deficit (mEq) should be added to the solution (usually, this means at least 1/2NS)– giving both Na deficit and H2O deficit over:
48 hours if long-standing (>2days) hypoNa
24 hours if more acute (2 or fewer days)

29. Hyponatremic Dehydration
Give ½ of total volume & Na in 1/3 of the time and the rest in the next 2/3 of the time.
Na should not increase >0.5mEq/hr (~2mEq/4hrs)– check at least q4-6 hrs to adjust solution.
If Na<115 or seizures: 5-8cc/kg of 3%NaCl over ½ hour OR until the seizure stops.

30. Hypernatremic Dehydration
Calculate the free H2O defecit
(Na-140) / 140 x 0.6x Weight (kg)
Replace ½ of this deficit in 24 hrs and the rest in the next 1-2days.
Again, do not decrease Na by more than 0.5mEq/hr
D5NS should be used if >165 mEq/L Na.

32. Fluid and Electrolyte Emergencies in Critically Ill Children
Case Studies:

33. Case Study #1 HPI: Hospital course:
A 3 month-old is in the PICU for shock following a two day history of fever and irritability. Blood and CSF cultures are positive for Streptococcus pneumoniae.
Hospital course:
Decreasing urine output (< 0.5 ml/kg/hr) over the last 24 hours.

34. Case Study #1
What is your differential diagnosis? What diagnostic studies would you order?

35. Case Study #1 Differential diagnosis
Oliguria
1) Pre-Renal (decreased effective renal blood flow)
Diminished intravascular volume, cardiac dysfunction, vasodilation
2) Post-Renal
Outlet obstruction (intrinsic vs. extrinsic), foley catheter occlusion
3) Renal
Acute tubular necrosis, acute renal failure, SIADH, etc.

36. Case Study #1 Laboratory studies
Serum studies
Sodium 126 mEq/L BUN 4 mg/dL
Chloride 98 mEq/L Creatinine 0.4 mg/dL
Potassium 3.7 mEq/L Glucose 129 mg/dL
Bicarbonate 25 mEq/L Osmolality 260 mosmol/kg
Urine studies
Specific gravity Sodium 58 mEq/L
Osmolality 645 mosmol/kg FeNa 2.4%
What are the primary abnormalities?

37. Case Study #1 Laboratory studies
Major abnormalities
1) Hyponatremia
2) Oliguria (inappropriately concentrated urine)
What is the most likely explanation for these findings?

38. Variable etiology Case Study #1 SIADH Trauma Infection Psychosis
Malignancy
Medications
(sulfonylureas, chlorpropamide, carbamazepine, tricyclics, amitriptyline, ssri thiazides, vincristine/blastinephenothiazines cyclophosphamides )
Diabetic ketoacidosis
CNS disorders
Positive pressure ventilation
“Stress”

39. Manifestations Case Study #1 SIADH
By definition, “inappropriate” implies having excluded normal physiologic reasons for release of ADH:
1) In response to hypertonicity.
2) In response to life threatening hypotension.
Hyponatremia
Oliguria
Concentrated urine
elevated urine specific gravity
“inappropriately” high urine osmolality in face of hyponatremia
Normal to high urine sodium excretion

40. Diagnosis Critical level of suspicion.
Case Study #1 SIADH
Diagnosis
Critical level of suspicion.
Demonstration of inappropriately concentrated urine in face of hyponatremia
 urine osmolality,  SG,  urine sodium excretion ( FeNa)
Be certain to exclude normal physiologic release of ADH
Frequently secondary to decreased perfusion
 Serum sodium,  urine osmolality,  urine sodium excretion (low FeNa)  consistent with dehydration or diminished renal blood flow. Look at patient more closely !!

41. Treatment Fluid restriction. Daily weights. Case Study #1 SIADH
50-75% of maintenance requirements, be certain to include oral intake.
Daily weights.

42. Case Study #1 The saga continues….
Hospital course:
Four hours after beginning fluid restriction, you are called because the patient is having a generalized seizure. There is no response to two doses of IV lorazepam.
What is the most likely explanation?

43. Case Study #1 The saga continues
Seizure
1) Worsening hyponatremia
2) Intracranial event
3) Meningitis
4) Other electrolyte disturbance (Ca , Ph , Mg )
5) Medication
What diagnostic studies would you order?

44. Case Study #1 The saga continues
Stat labs:
Sodium 117 mEq/L
What would you do now?

45. To correct sodium to 125 mEq/L, the deficit is equal to
Case Study #1 Hyponatremic seizure Treatment - Hypertonic saline (3% NaCl) infusion
To correct sodium to 125 mEq/L, the deficit is equal to
(0.6)(weight[kg])(125- measured sodium)
(0.6)(8)( ) = 38.4 mEq
Because patient is symptomatic with seizures, the goal is to immediately increase serum sodium by 5 mEq/L
mEq sodium = (0.6)(8 kg)(5) = 24 mEq
3% NaCl = 500 mEq/1000mL, therefore 24 mEq bolus = 48 mls, followed by slow infusion of remaining 14.4 mEq (29 mls) over next several hours
Short cut - 3% NaCl bolus for symptomatic hyponatremia = 4-6 cc/kg.
(0.6 = % body water)

46. Case Study #2 HPI: Home meds: PE:
A 5 month-old girl presents with a one day history of irritability and fever. Mother reports three days of “bad” vomiting and diarrhea.
Home meds:
Acetaminophen and ibuprofen for fever
PE:
BP 70/40, HR 200, R 60, T38.3 C. Irritable, sunken eyes and fontanelle, skin feels like Pillsbury Dough Boy

47. Case Study #2
No one can obtain IV access after 15 minutes, what would you do now?

48. Case Study #2 Place intraosseous line Serum studies
Bolus 40 ml/kg of isotonic saline
Reassessment (HR 170, RR 40, BP 75/40)
Serum studies
Sodium 164 mEq/L BUN 75 mg/dL
Chloride 139 mEq/L Creatinine 3.1 mg/dL
Potassium 5.5 mEq/L Glucose 101 mg/dL
Bicarbonate 12 mEq/L
pH pCO2 11
pO HCO3 8

49. Case Study #2
What is the most likely explanation of this patients acidosis?

50. Case Study #2 Metabolic acidosis and the anion gap
Represents unmeasured anions that balance cations in the serum (e.g. albumin)
Sodium - (chloride + bicarbonate)
Normal 12 +/- 2 meq/L
Elevated anion gap consistent with excess acid
Normal anion gap consistent with excess loss of base
164 - ( ) = 13

51. (usually hyperchloremic)
Case Study #2 Metabolic acidosis and the anion gap
Normal gap
(usually hyperchloremic)
Increased gap
Renal “HCO3”
losses
GI “HCO3”
losses
 Acid prod
 Acid elimination
MUDPILES
M Methanol U Uremia D Diabetic Ketoacidosis P Paraldehyde I Infection L Lactic Acidosis E Ethylene Glycol S Salicylates
Renal disease
Proximal RTA
Distal RTA
Diarrhea

52. Case Study #3 HPI: What is your differential diagnosis?
A five year old (18 kg) boy was involved in a a motor vehicle accident two days ago. He sustained an isolated head injury with intraventricular hemorrhage and multiple large cerebral contusions. Three hours ago, he had an episode of severe intracranial hypertension (ICP 90mm Hg, MAP 50mm Hg, requiring volume plus epinephrine infusion for hypotension. Over the last two hours, his urine output has increased to ml/hour (~8ml/kg/hr).
What is your differential diagnosis?
What test would you order?

53. Case Study #3 Differential diagnosis
Polyuria
1) Central diabetes insipidus
Deficient ADH secretion (idiopathic, trauma, pituitary surgery, hypoxic ischemic encephalopathy)
2) Nephrogenic diabetes insipidus
Renal resistance to ADH (X-linked hereditary, chronic lithium, hypercalcemia, ...)
3) Primary polydipsia (psychogenic)
Primary increase in water intake (psychiatric), occasionally hypothalamic lesion affecting thirst center
4) Solute diuresis
Diuretics (lasix, mannitol,..), glucosuria, high protein diets, post- obstructive uropathy, resolving ATN, ….

54. Case Study #3 Laboratory studies
Serum studies
Sodium 155 mEq/L BUN 13 mg/dL
Chloride 114 mEq/L Creatinine 0.6 mg/dL
Potassium 4.2 mEq/L Glucose 86 mg/dL
Bicarbonate 22 mEq/L Serum osmolality: 320 mosmol/kg
Other
Urine specific gravity 1.005, no glucose.
Urine osmolality: 160 mosmol/kg
What are the main abnormalities?

55. Case Study #3 Laboratory studies
Major abnormalities
1) Hypernatremia
2) Polyuria (inappropriately dilute urine)
What is the most likely explanation?

56. Case Study #3 Diabetes Insipidus
Diagnosis
Central Diabetes insipidus
1) Polyuria
2) Inappropriately dilute urine
(urine osmolality < serum osmolality)
May be see with midline defects
Frequently occurs in brain dead patients
What should you do to treat this child?

57. Case Study #3 Diabetes Insipidus
Treatment
Acute: Vasopressin infusion
Chronic: DDAVP (desmopressin)
Warning
Closely monitor for development of hyponatremia

58. Case Study #4 HPI: Home meds: PE:
A six year old, 25 kg, boy with severe asthma (S/P ECMO for a previous exacerbation) presents with a two day history of severe vomiting and diarrhea to the Emergency Department.
Home meds:
Albuterol MDI two puffs QID, Salmeterol MDI two puffs BID, Prednisone 10mg daily, Fluticasone 220 mcg two puffs BID
PE:
BP 70/40, HR 168, R 40, T39.0 C. He is very lethargic (GCS 11). Poor perfusion with cool extremities, mottling, and delayed capillary refill, otherwise no specific system abnormalities.

59. Case Study #4
What is your differential diagnosis? What diagnostic studies would you order?

60. Case Study #4 Differential diagnosis
Shock
1) Cardiogenic (poor pump)
Myocarditis
Pericardial effusion
2) Hypovolemic (low volume)
Hemorrhage, excessive GI losses, “3rd spacing” (burns, sepsis)
3) Distributive (low tone)
Sepsis, anaphylaxis

61. Case Study #4 Laboratory studies
Serum studies
Sodium 130 mEq/L BUN 43 mg/dL
Chloride 99 mEq/L Creatinine 0.6 mg/dL
Potassium 5.7 mEq/L Glucose 48 mg/dL
Bicarbonate 12 mEq/L
Other
WBC: 13k (60% P, 30% L), HCT 35%, PLT 223k
Chest radiograph: no abnormalities
What are the electrolyte abnormalities?

62. 1) Hyponatremic dehydration
Case Study #4 Diagnosis
Major abnormalities
1) Hyponatremic dehydration
2) Hypoglycemia
3) Hyperkalemia, mild
4) Acidosis
5) Azotemia
What is the most likely explanation for these findings?

63. Case Study #4 Adrenal Insufficiency
1o adrenal insufficiency (Addison’s disease)
Adrenal gland destruction/dysfunction (ie. autoimmune, hemorrhagic)
most common in infants 5-15 days old
2nd adrenal insufficiency
ACTH deficiency (ie. panhypopituitarism or isolated ACTH)
“Tertiary” or “iatrogenic”
Suppression of hypothalamic-pituitary-adrenal axis (ie. chronic steroid use)

64. Case Study #4 Adrenal Insufficiency
Manifestations
Major hormonal factor precipitating crisis is mineralcorticoid deficiency, not glucocorticoid.
Dehydration, hypotension, shock out of proportion to severity of illness
Nausea, vomiting, abdominal pain, weakness, tiredness, fatigue, anorexia
Unexplained fever
Hypoglycemia (more common in children and tertiary)
Hyponatremia, hyperkalemia, azotemia

65. Case Study #4 Adrenal Insufficiency
Diagnosis
Critical level of suspicion in all patients with shock
1) Demonstration of inappropriately low cortisol secretion
Basal morning level vs. random “stress” level
2) Determine whether cortisol deficiency dependent or independent of ACTH secretion.
 ACTH,  cortisol  1o adrenal insufficiency
 ACTH,  cortisol  2nd or tertiary insufficiency
3) Seek a treatable cause

66. Case Study #4 Adrenal Insufficiency
What should you do to treat this child?

67. Case Study #4 Adrenal Insufficiency
Treatment
Do not wait for confirmatory labs
Fluid resuscitation - isotonic crystalloid
Treat hypoglycemia
Glucocorticoid replacement - hydrocortisone in stress doses mg/m2 (1-2 mg/kg) IV
Consider mineralocorticoid (Florinef®)

68. Case Study #5 HPI: What do you do now?
An eight month old infant with autosomal recessive polycystic kidney disease presents with irritability. She is on nightly peritoneal dialysis at home. The lab calls a panic potassium value of 7.1 meq/L. The tech says it is not hemolyzed.
What do you do now?

69. Case Study #5 Hyperkalemia
Treatment
Immediately repeat serum potassium.
Do not wait for confirmatory labs especially if EKG changes present.
Anticipatory
Stop potassium administration including feeds

70. Cardiac Monitor
What is this rhythm?
What is your immediate treatment?

71. Case Study #5 Hyperkalemia Arrhythmia Recognition
Webster, A et al. Emerg Med J 2002;19:74-77
The ECG changes as hyperkalaemia develops. (A) A normal complex. (B) Loss of P-waves, tenting of the T-waves. (C) Broadening of the QRS complex. (D) Sine wave appearance.
Copyright ©2002 BMJ Publishing Group Ltd.

72. Case Study #5 Hyperkalemia Treatment (cont)
Control effects
Antagonism of membrane actions of potassium
Calcium chloride mg/kg over 5 minutes; may repeat x2
Shift potassium intracellularly
Glucose 1 gm/kg plus 0.1 unit/kg regular insulin
Alkalinize (increase ventilator rate; Sodium bicarbonate 1 mEq/kg IV)
Inhaled 2 adrenergic agonist (albuterol)
Removal of potassium from the body
Loop / thiazide diuretics
Cation exchange resin: sodium polstyrene sulfonate (Kayexelate®) 1 gm/kg PO or PR (or both)
Dialysis

73. Case Study #6 HPI: What is your differential diagnosis?
A three year old boy is recovering from septic shock. He received 150 ml/kg in fluid boluses in the first 24 hours and has anasarca. You begin him on a loop diuretic for diuresis. He develops severe weakness and begins to hypoventilate. You notice unifocal premature ventricular beats on his cardiac monitor.
What is your differential diagnosis?
What tests would you order?

74. Case Study #6 Laboratory studies
Serum studies
Sodium 134 mEq/L BUN 11 mg/dL
Chloride 98 mEq/L Creatinine 0.4 mg/dL
Potassium 2.4 mEq/L Calcium 9.2 mg/dL
Bicarbonate 27 mEq/L Phosphorus 3.2 mg/dL
Other
EKG: Unifocal PVC’s
What is the main abnormality?

75. Case Study #6 Laboratory studies
Major abnormality
1) Hypokalemia
What would you do now?

76. Case Study #6 Hypokalemia
Treatment
Oral
Safest, although solutions may cause diarrhea IV
Peripheral as continuous infusion. Avoid temptation to rapidly bolus
Central: mEq/kg over 1-3 hours, depending on severity. No more than 20 mEq IV at a time.
Replace magnesium also if low
(25-50 mg/kg MgSO4)

77. Summary
Disorders of sodium, water, and potassium regulation are common in critically ill children.
Diagnostic approach must be considered carefully for each patient.
Strict attention to detail is important in providing safe and effective therapy

78. In hospitalized patients, the ongoing administration of hypotonic maintenance fluids may result in hyponatremia
Hyponatremia is often caused by the intake of electrolyte-free water that cannot be excreted due primarily to persistent ADH secretion that is "inappropriate," or not triggered by usual osmotic or volume parameters
In children, inappropriate ADH secretion may occur post-operatively, with central nervous system or pulmonary pathology, after the provision of some medications, or in response to pain or anxiety

79. Maintenance Therapy Caloric expenditure varies with body weight:
Weight less than 10 kg — approximately 100 kcal/kg of caloric expenditure/ day
Weight from 10 to 20 kg — 1000 kcal for first 10 kg of body weight plus 50 kcal/kg for any increment of weight above 10 kg
Weight from 20 to 80 kg — 1500 kcal for first 20 kg of body weight plus 20 kcal/kg for any increment of weight above 20 kg.