fluids and electrolytes
TRANSCRIPT
Cesar MellaPediatric Critical Care
IntroductionCase #14 year old male presents to ER.History of vomiting and diarrhea. He has had 10 episodes of vomiting (clear then
yellow tinged) 8 episodes of diarrhea with some mucousy
material in the first few episodes. The diarrhea is now watery and the last few episodes have been red in color. The diarrhea odor is very foul.
He has had a fever T-max 101 degrees at home.
Case #1His parents gave him a sports drink (red
color), and then they tried clear Pedialyte.Continues to have vomiting and diarrhea.He feels weak and tired and he looks slightly
pale at times. He has only urinated twice in the last 15
hours.
Case #1Exam: VS T 38.2 degrees (oral), P 110, R45, BP
90/65, oxygen saturation 100% in room air. Weight 18 kg.
He is alert and cooperative, but not very active. He is not toxic or irritable. His eyes are not
sunken. Oral mucosa is moist but he just vomited. CVS/RS exams are normal except for tachycardia.
His abdomen is soft and non-tender. Bowel sounds are normoactive. He has no inguinal hernias and his testes are normal. His overall color is slightly pale, his capillary refill time is 2 seconds over his chest, and his skin turgor feels somewhat diminished.
Body Water CompositionBody composition is 60% to 75% water. The 60% applies to adults and the 75% applies to
newborns. Younger children have more water than adults. Out of this, about 60% is intracellular and 40% is
extracellular. Of the extracellular fluid, 3/4 is interstitial and
1/4 is circulating as plasma There is also a small percentage known as trans-
cellular water (about 2%).
Total Body WaterTotal Body Water60%60%
Intracellular Water 40%Intracellular Water 40%
ExtracellularExtracellularwater 20%water 20%
Interstitial Interstitial Fluid 15%Fluid 15%
PV 5%PV 5%
Total Body WaterHowever, total blood volume is actually 8% to 9%
of body weight for children and 7% of body weight for adults
This is because the red blood cell elements of blood are not considered to be "body water".
Thus, if plasma consists of 5% of the body weight, a few more percentage points would account for the circulating blood volume (which is larger than the circulating plasma volume).
Normal fluid lossesFluid losses occur routinely through urine, stools,
respiratory vapor and insensible skin losses. Perspiration can exaggerate skin losses.
Illness and exercise can exaggerate respiratory fluid loss through vapor. (Remember tachypneic patients)
Other conditions such as burns, vomiting, diarrhea, hemorrhage, diuretics, etc., can also exaggerate fluid losses.
Normal fluid losses:
Insensible 30-40 cc/kg (skin and lungs)
Urine 60 cc/kg
Stool 10-20 cc/kg
Osmolality of body fluidsDefinition- Solute concentration per unit of
solution (i.e.. serum)Normal: 280 -295 mOsm/lTightly regulated and equal between compartments
Fluid moves from one compartment to the other to maintain osmolality.
Serum Osmolality
2Na + Bun + Blood Glucose 2.8 18
Renal Fluid PhysiologyThe postnatal shift in body fluids is
principally mediated through the kidneys' regulation of water and sodium excretion.
Related to GFR and tubular function. A term newborn's glomerular filtration rate
(GFR) is 25% of an adult's.
Renal Electrolyte and Fluid PhysiologyClinical states that can increase basal fluid
requirements in the infant include:HyperthermiaIncreased evaporative losses from mechanical
ventilationAltered transepithelial losses from premature
gestational age.
Renal PhysiologySimple maneuvers include increasing
basal fluid replacement in infants with hyperthermia or in those placed under bilirubin heating lamps and ensuring that all ventilator tubing is humidified.
The patient's state of hydration, renal function, and osmolar load determine his or her urine output and concentration.
Renal PhysiologyOsmolar load consists of endogenous and
exogenous solutes that the kidney must clear to maintain homeostasis.
The volume of renal water must be sufficient for the kidney to clear the osmolar load given its concentrating capacity.
BW ( kg ) Cal/kg/day
2.5 - 10 10011 - 20
50 (+ 1000)20 +
20 (+ 1500)
1 calorie = amount of heat necessary to increase the temperature of 1g of water from 14.5 to 15.5 degree Centigrade.
Add more calories when metabolic demand is increased; e.g., 12 % for each degree C body temperature increased
Maintenance FluidsMaintenance Fluids
Maintenance Fluids II100 cc/kg for the first 10 kg of body
weight50 cc/kg for the next 10 kg of body20 cc/kg for every kilogram thereafter.
For example, 40kg patient would be:10 x 100= 1000cc10 x 50= 500cc20x 20= 400ccTotal: 1900cc/ 24h
IVFNormal Saline (0.9 %) = 154 mEq/L
½ N/S (0.45%) = 77 mEq/L
1/3 N/S (0.33%) = 51 mEq/L
¼ NS (0.2 %) = 39 mEq/L
Fluid Deficit StatesClinical
Mild Dehydration (5%)Moderate Dehydration (10%)Severe Dehydration (15% or more)
Body Weight
Clinical Dehydration AssessmentExamination Mild Moderate Severe
Percentage 5% 10% 15% or >
Older Child 3% 6% 9% or >
Skin turgor Normal Tenting None
Skin touch Normal Dry Clammy
Buccal Mucosa Moist Dry Cracked
Eyes Normal Deep Set Sunken
Tears Present Reduced None
Fontanelle Flat Soft Sunken
CNS Consolable Irritable Lethargic/Obtunded
Pulse Rate Normal Slightly Increased
Increased
Pulse Quality Normal Weak Feeble/Impalpable
Capillary Refill Normal 2 secs >3secs
Urine Output Normal Decreased Anuric
ORSPreferredCheaperLess InvasiveCan be done at homeBut… needs frequent assessments and is
much slower
Contraindications>10 % DehydrationPO IntoleranceIntractable vomitingAltered Mental statusRapid ongoing losses
IV HydrationNS or LR 20cc/kg is a common starting pointSevere dehydration -> infuse in < 10 minsModerate dehydration can be given 1 hrNS or LR are “isotonic fluids”
Type of FluidsMaintenance ElectrolytesNa is given as 3 meq/ 100 cc of IVFK is given as 2 meq / 100 cc of IVFReplaced evenly over time
Deficit ElectrolytesRapid onset dehydration > ECFProlonged dehydration ECF and ICFECF 140 meq/L NaICF 140 meq/L K
Duration of symptoms<3 days: 80% ECF, 20% ICF> 3days: 60% ECF, 40% ICF
Other FactorsBolusElectrolyte ImbalancesRapid CorrectionsCorrect SlowlyReassessReassess
Numbers to MemorizeMaintenance Fluid Calculations
100/ 50/ 20Maintenance Electrolytes
3 meq Na/ 100cc IVF 2 meq K/ 100 cc IVFBolus 20 cc/kgNormal Osmolarity: 290 mOsm/ L30 cc= 1 ounceDuration of symptoms
<3 days: 80% ECF, 20% ICF> 3days: 60% ECF, 40% ICF
Clinical Cases
Case Study #1HPI:
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: The urine output had decreased (< 0.5 mL/kg/hr)
over the last 24 hours.What is your differential diagnosis regarding the
cause of the oliguria?
Case Study #1Differential DiagnosisOliguria
1) Pre-Renal (decreased effective renal blood flow) Diminished intravascular volume, cardiac
dysfunction, vasodilatation
2) Renal Acute tubular necrosis, acute renal failure, SIADH, ...
3) Post-Renal Outlet obstruction (intrinsic vs. extrinsic), Foley
catheter occlusion
What laboratory studies would you order?
Case Study #1Laboratory studiesSerum studies
Sodium 126 mEq/L BUN 4 mg/dLChloride 98 mEq/L Creatinine 0.4 mg/dLPotassium 3.7 mEq/L Glucose 129 mg/dLBicarbonate 25 mEq/L Osmolality 260 mosm/kg
Urine studiesSpecific gravity 1.025 Sodium 58 mEq/LOsmolality 645 mosm/kg FeNa 2.4%
What are the primary abnormalities?
Case Study #1Laboratory studiesMajor abnormalities 1) Hyponatremia 2) Oliguria (inappropriately
concentrated urine)
What is the most likely explanation for these findings?
Case Study #1 SIADHSyndrome of Inappropriate Antidiuretic
Hormone (SIADH) Variable etiologyTrauma InfectionPsychosis MalignancyMedications Diabetic ketoacidosisCNS disorders Positive pressure ventilation“Stress”
Case Study #1 SIADHManifestations
By definition, “inappropriate” implies the exclusion of normal physiologic reasons for release of ADH: 1) In response to hypertonicity. 2) In response to life threatening hypotension.
Euvolemia with:1. Hyponatremia2. Oliguria3. Concentrated urine
elevated urine specific gravity “inappropriately” high urine osmolality in face of
hyponatremia4. Normal to high urine sodium excretion
Case Study #1 SIADHDiagnosis
Critical level of suspicion.Demonstration of inappropriately concentrated urine in
face of hyponatremia urine osmolality SG urine sodium excretion ( FeNa)
Be certain to exclude conditions with 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 !!
Case Study #1 SIADHTreatment
Fluid restriction. 50-75% of maintenance requirements, be certain to
include oral intake.Daily weights.
Case Study #1The saga continues….Hospital course:
Four hours after beginning fluid restriction, you are called because the patient developed generalized seizures. There is no response to two doses of IV lorazepam (Ativan®) and a loading dose of fosphenytoin (Cerebyx®)
What is the most likely explanation?
Case Study #1The saga continuesSeizure 1) Worsening hyponatremia 2) Intracranial event 3) Meningitis 4) Other electrolyte disturbance 5) Medication 6) Hypertension
What diagnostic studies would you order?
Case Study #1The saga continuesStat labs: Sodium 117 mEq/L
What would you do now?
Case Study #1 Hyponatremic SeizuresTreatment: Hypertonic saline (3% NaCl) infusion
Because patient is symptomatic (seizures), immediately increase serum sodium by 5 mEq/L mEq sodium = (0.6) (Wt in kg) (Desired Na in mEq) = = (0.6) (8kg) (5 mEq increase) = 24 mEq 3% NaCl = 0.5 mEq/L, therefore 24 mEq = 48 mL
To correct sodium to 125 mEq/L, the deficit is equal to (0.6) (weight [kg]) (125- measured sodium) (0.6)(8)(125-117) = 38.4 mEq
Follow the initial 24 mEq by slow infusion of remaining 14.4 mEq (29 mL) over next several hours
This equation can be estimated by (slight underestimate) 1mL/kg of 3% NaCl will raise Na by 1 mEq If you want to raise Na by 5 mEq give 5 mL/kg
Case Study #2HPI:
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 fontanel, skin feels “doughy”
No one can obtain IV access after 15 minutes,
What would you do now?
Case Study #2Place intraosseous line
Bolus 40 mL/kg of isotonic saline Reassessment (HR 170, RR 40, BP 75/40)
Serum studiesSodium 164 mEq/L BUN 75 mg/dLChloride 139 mEq/L Creatinine 3.1 mg/dLPotassium 5.5 mEq/L Glucose 101 mg/dLBicarbonate 12 mEq/L
VBG pH 7.07 pCO2 11 pO2 121 HCO3 8
What type of acid/base disorder does this patient have?
What is the most likely explanation of this patient’s acidosis?
Case Study #2Non-anion Gap Metabolic AcidosisAnion GapSodium - (chloride + bicarbonate)Normal 12 +/- 2 mEq/LElevated anion gap consistent with excess
acidNormal anion gap consistent with excess loss
of basePatient’s Anion Gap: 164 - (139 + 12) = 13
1. Normal gap
2. Increased gap
1. Renal “HCO3” losses
2. GI “HCO3” losses
Proximal RTA Distal RTA
Diarrhea“Rectal Tubular Acidosis”
1. Acid prod 2. Acid elimination
MethanolUremiaDKAParaldhydeIEM, IronLactateEthylene GlycolSalicylates
Renal disease
Case Study #3HPI:
A five year old (18 kg) boy was involved in a a motor vehicle crash 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 90 mmHg, MAP 50 mmHg, requiring intravascular volume expansion and epinephrine infusion for hypotension. Over the last two hours, his urine output has increased to 130-150 mL/hour (~ 8mL/kg/hr).
What is your differential diagnosis?What test would you order?
Case Study #3Differential diagnosisPolyuria
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, ….
Case Study #3Laboratory studiesSerum studies
Sodium 155 mEq/L BUN 13 mg/dLChloride 114 mEq/L Creatinine 0.6 mg/dLPotassium 4.2 mEq/L Glucose 86 mg/dLBicarbonate 22 mEq/L Serum osmolality: 320 mosm/kg
OtherUrine specific gravity 1.005, no glucose.Urine osmolality: 160 mosm/kg
What are the main abnormalities?
Case Study #3Laboratory studiesMajor abnormalities 1) Hypernatremia 2) Polyuria (inappropriately dilute urine)
What is the most likely explanation?
Case Study #3Diabetes InsipidusDiagnosisCentral Diabetes insipidus
1) Polyuria2) Inappropriately dilute urine (urine osmolality < serum
osmolality)
May be seen with midline CNS defectsFrequently observed in patients with severe
intracranial hypertension resulting in herniation and loss of cerebral perfusion
What should you do to treat this child?
Case Study #3Diabetes InsipidusTreatment
Acute: Vasopressin infusion - begin with 0.5 milliunits/kg/hour, double every 15-30 minutes until urine flow controlled
Chronic: DDAVP (desmopressin)Warning
Closely monitor for development of hyponatremia
Case Study #4 HPI:
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.
What is your differential diagnosis? What diagnostic studies would you order?
Case Study #4Differential diagnosisShock
1) Cardiogenic Myocarditis Pericardial effusion
2) Hypovolemic Hemorrhage, excessive GI losses, “3rd spacing”
(burns, sepsis)
3) Distributive Sepsis, anaphylaxis
Case Study #4Laboratory studiesSerum studies
Sodium 130 mEq/L BUN 43 mg/dLChloride 99 mEq/L Creatinine 0.6 mg/dLPotassium 5.7 mEq/L Glucose 48 mg/dLBicarbonate 12 mEq/L
OtherWBC: 13k (60% P, 30% L), HCT 35%, PLT 223kChest radiograph: no abnormalities
What are the electrolyte abnormalities?
Case Study #4DiagnosisMajor abnormalities 1) Hyponatremic dehydration 2) Hypoglycemia 3) Hyperkalemia, mild 4) Acidosis 5) Azotemia
What is the most likely explanation for these findings?
Case Study #4 Adrenal Insufficiency1o adrenal insufficiency (Addison’s disease)
Adrenal gland destruction/dysfunction (ie. autoimmune, hemorrhagic)
most common in infants 5-15 days old Secondary adrenal insufficiency
ACTH deficiency (ie. panhypopituitarism or isolated ACTH)
“Tertiary” or “iatrogenic” Suppression of hypothalamic-pituitary-adrenal
axis (ie. chronic steroid use)
Case Study #4 Adrenal InsufficiencyManifestations
Major hormonal factor precipitating crisis is mineralocorticoid deficiency, not glucocorticoid.
Dehydration, hypotension, shock out of proportion to severity of illness
Nausea, vomiting, abdominal pain, weakness, tiredness, fatigue, anorexia
Unexplained feverHypoglycemia (more common in children and
tertiary)Hyponatremia, hyperkalemia, azotemia
Case Study #4 Adrenal InsufficiencyDiagnosis - critical level of suspicion in all patients
with shock1) Demonstration of inappropriately low cortisol
secretion Basal morning level vs. random “stress” level Significant controversy exists as to what level is adequate
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 What should you do to treat this child?
Case Study #4 Adrenal InsufficiencyTreatment
Do not wait for confirmatory labsFluid resuscitation - isotonic crystalloidTreat hypoglycemiaGlucocorticoid replacement - hydrocortisone in
stress doses - 25-50 mg/m2 (1-2 mg/kg) IV every 6 hours
Consider mineralocorticoid (Florinef®)
Case Study #5HPI:
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 states that the sample did not have hemolysis.
What do you do now?
Case Study #5HyperkalemiaTreatment
Immediately recheck serum potassium. Immediately check EKG and treat if EKG
changes are presentAnticipatory – discontinue all sources of
potassium including feeds
The Patient’s EKG Strip:
What is the immediate next step in treatment?
Case Study #5HyperkalemiaCalcium chloride 10-20 mg/kg over 5 minutes; may repeat
x2Antagonism of membrane actions of potassiumFirst treatment!!!Avoid rapid IV push
Shift potassium intracellularlyGlucose 1 gm/kg plus 0.1 unit/kg regular insulinAlkalinize (increase ventilator rate; Sodium bicarbonate
1 mEq/kg IV)Inhaled 2 adrenergic agonist (albuterol)
Removal of potassium from the bodyLoop / thiazide diureticsCation exchange resin: sodium polstyrene sulfonate
(Kayexelate®) 1 gm/kg PO or PR (or both)Dialysis
Case Study #6HPI:
A three year old boy is recovering from septic shock. He received 150 mL/kg in fluid boluses in the first 24 hours of therapy and has developed anasarca. You begin him on a bumetanide infusion (Bumex®) for diuresis. He develops significant generalized 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?
Case Study #6Laboratory studies Serum studies
Sodium 134 mEq/L BUN 11 mg/dLChloride 98 mEq/L Creatinine 0.4 mg/dLPotassium 2.4 mEq/L Calcium 9.2 mg/dLBicarbonate 27 mEq/L Phosphorus 3.2 mg/dL
OtherEKG: Unifocal PVC’s
What is the main abnormality?
Case Study #6Laboratory studiesMajor abnormality
Hypokalemia
What would you do now?
Case Study #6HypokalemiaTreatment
Oral Safest, although solutions may cause diarrhea
IV Peripheral: do not exceed 40-50 mEq/L potassium -
Avoid temptation to administer potassium by rapid bolus
Central: 0.5 -1 mEq/kg over 1-3 hours, depending on severity
Replace magnesium also if low (25-50 mg/kg MgSO4)
Questions? Comments?