Presentation on theme: "Fluids & Electrolytes:"— Presentation transcript:
1Fluids & Electrolytes: Created by: Sarah A. Murphy, MDEdited by: Camille Henry, MD andVenee Tubman, MD
2Fluids and Electrolytes Background – General PrincinplesMaintenance TherapyReplacement TherapyImportant Electrolyte Abnormalities
3Fluids and Electrolytes: Background There are normal and abnormal losses of fluids and electrolytes from the urine, sweat, feces and respirationThe kidney is important to:balance losses and maintain blood volumebalance of electrolytes through excretion and reabsorptionWater follows Na
4Body fluid compartments PlasmaIntracellularCationsAnionsNa (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
5Fluids and Electrolytes: Background Regulation of intravascular volume:1) In the kidney, the juxtaglomerular apparatus and macula densa sense decreased renal blood flow and release reninRenin stimulates angiotensinogen angiotensin I angiotensin II (via ACE)Angiotensin II causes release of aldosteroneAldosterone increases distal renal tubule Na reabsorptionThis leads to increased blood volume as water follows Na into blood
6Fluids and Electrolytes: Background 2) Anti-diuretic hormone is released in hypovolemia increases renal reabsorption of water3) In the atria and aortic arch, baroreceptors sense volume depletionBaroreceptors signal brain via CN IX and X sympathetic dischargeSympathetic tone regulates renal blood flow and leads to Na conservation4) Atrial natriuretic peptide: regulates Na by increasing glomerular filtration rate and hydrostatic pressure (dilates afferent and constricts efferent arterioles of kidney)
7Water Balance: Background Water losses are sensed by an increase in plasma sodium and osmolalityPatients who are alert, have an intact thirst mechanism, and are able to drink water, will self-regulatePatients who are unable to eat or drink have urinary, skin, and respiratory tract losses that must be replaced
8Fluids and Electrolytes: Background The goal of fluid therapy is to maintain the normal volume and composition of body fluids and correct abnormalitiesIn children, the most common abnormality is hypovolemia, primarily due to vomiting and diarrhea from gastroenteritis
9Fluids 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
10Maintenance Therapy:How do we determine what are the on-going losses that need to be replaced?
11Calculating Maintenance Fluid Requirement Putting these together, we come up with this formula for daily maintenance water requirements…Per hourPer dayExample: for wt 34kgFor each kg up to 104ml/hr100ml/day40ml/hr1000ml/day+ For each kg btw 10-202ml/hr50ml/day20ml/hr500ml/day+ For each kg above 201ml/hr20ml/day14ml/hr280ml/day=74ml/hr1780ml/dayDaily water needs are based upon insensible losses from the respiratory tract and skin, and sensible losses from urine and stoolWater requirements are estimated by caloric energy expenditures:We need approximately 100 mL of water for every 100 kcal/kg of energy expended
12Maintenance Therapy:What about important electrolytes like Na and K?
13Maintenance Therapy:Like water, electrolyte requirements are estimated based upon caloric energy expenditureSodium and chloride — the body needs to take in 4 to 6 meq/kg/dayPotassium — the body needs to take in 2 to 3 meq/kg/dayThe majority of the electrolyte losses are from the urine, with a lesser contribution from sweat and stool losses
14Special Situations: Newborns premature infants have very thin skinincreased insensible lossesinfants in isolettes are in a humidified environmentdecreased insensible losses.newborns are born with excess body waterduring the first few days of life babies do not require full maintenanceRenal failure—decreased fluid requirement due to oliguria/anuria.Burns—increased skin losses
15Special Situations:Fever—increased losses from increased skin loss and, in young children/infants, also due to increased respiratory rate that often accompanies feverVentilation—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.
17Replacement 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
19Some more background information: Body fluid compartments Intra Cellular Water: 40% of body weightExtra Cellular Water: 20% of body weight (interstitial 15% and intravascular 5%)Total Body Water:Newborns 75%Children 60%Adult males 60%Adult females 50%
20Replacement therapy Na deficit: 0.6 x (weight in kg) x (140 – measured Na)Total Body Water = 0.6 x weight in kg
21Therapy 1: Oral Rehydration Oral rehydration therapy is the best way to replace fluid losses if children are stable and can tolerate itIt is a slow process: giving 5cc of fluid by mouth every 5-10 minutesWith these small volumes, children generally do not vomit, and are eventually able to work up to larger volumes
22Therapy 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.
23Therapy 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 dayPotassium:2 meq/100 mL of water per dayPractically 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.
24Components of Hydration Fluids CHO(g/dL)Na+(mEq/L)K+Cl-HCO3mOsm/kgNS154308LR0-10130410928273D5 ½ NS c 20K5772097D5 ¼ NS c 10K381048ORS2908030310Gatorade5.9212.517377AppleJuice11.90.426700
25Types of LossesInsensible 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)
26Therapy: 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 KClFor patients >10kg, we use D5 ½ NS c 20 mEq/L of KCl.
27A Note about Hypo/HyperNa Most patients with Na between will tolerate adjustment of their Na by routine re-hydration as aboveRapid correction of hypoNa can lead to central pontine myelinolysis or Sz’sRapid drop of Na in patients with hyperNa can lead to cerebral edemaThe “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.
28Hyponatremic 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) hypoNa24 hours if more acute (2 or fewer days)
29Hyponatremic 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.
30Hypernatremic 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/hrD5NS should be used if >165 mEq/L Na.
32Fluid and Electrolyte Emergencies in Critically Ill Children Case Studies:
33Case 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.
34Case Study #1What is your differential diagnosis? What diagnostic studies would you order?
39Manifestations 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.HyponatremiaOliguriaConcentrated urineelevated urine specific gravity“inappropriately” high urine osmolality in face of hyponatremiaNormal to high urine sodium excretion
40Diagnosis Critical level of suspicion. Case Study #1 SIADHDiagnosisCritical 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 ADHFrequently 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 !!
41Treatment Fluid restriction. Daily weights. Case Study #1 SIADH 50-75% of maintenance requirements, be certain to include oral intake.Daily weights.
42Case 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?
43Case Study #1 The saga continues Seizure1) Worsening hyponatremia2) Intracranial event3) Meningitis4) Other electrolyte disturbance (Ca , Ph , Mg )5) MedicationWhat diagnostic studies would you order?
44Case Study #1 The saga continues Stat labs:Sodium 117 mEq/LWhat would you do now?
45To correct sodium to 125 mEq/L, the deficit is equal to Case Study #1 Hyponatremic seizure Treatment - Hypertonic saline (3% NaCl) infusionTo correct sodium to 125 mEq/L, the deficit is equal to(0.6)(weight[kg])(125- measured sodium)(0.6)(8)( ) = 38.4 mEqBecause patient is symptomatic with seizures, the goal is to immediately increase serum sodium by 5 mEq/LmEq sodium = (0.6)(8 kg)(5) = 24 mEq3% NaCl = 500 mEq/1000mL, therefore 24 mEq bolus = 48 mls, followed by slow infusion of remaining 14.4 mEq (29 mls) over next several hoursShort cut - 3% NaCl bolus for symptomatic hyponatremia = 4-6 cc/kg.(0.6 = % body water)
46Case 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 feverPE:BP 70/40, HR 200, R 60, T38.3 C. Irritable, sunken eyes and fontanelle, skin feels like Pillsbury Dough Boy
47Case Study #2No one can obtain IV access after 15 minutes, what would you do now?
48Case Study #2 Place intraosseous line Serum studies Bolus 40 ml/kg of isotonic salineReassessment (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/LpH pCO2 11pO HCO3 8
49Case Study #2What is the most likely explanation of this patients acidosis?
50Case 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/LElevated anion gap consistent with excess acidNormal anion gap consistent with excess loss of base164 - ( ) = 13
51(usually hyperchloremic) Case Study #2 Metabolic acidosis and the anion gapNormal gap(usually hyperchloremic)Increased gapRenal “HCO3”lossesGI “HCO3”losses Acid prod Acid eliminationMUDPILESM Methanol U Uremia D Diabetic Ketoacidosis P Paraldehyde I Infection L Lactic Acidosis E Ethylene Glycol S SalicylatesRenal diseaseProximal RTADistal RTADiarrhea
52Case 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?
53Case Study #3 Differential diagnosis Polyuria1) Central diabetes insipidusDeficient ADH secretion (idiopathic, trauma, pituitary surgery, hypoxic ischemic encephalopathy)2) Nephrogenic diabetes insipidusRenal resistance to ADH (X-linked hereditary, chronic lithium, hypercalcemia, ...)3) Primary polydipsia (psychogenic)Primary increase in water intake (psychiatric), occasionally hypothalamic lesion affecting thirst center4) Solute diuresisDiuretics (lasix, mannitol,..), glucosuria, high protein diets, post- obstructive uropathy, resolving ATN, ….
54Case Study #3 Laboratory studies Serum studiesSodium 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 mosmol/kgOtherUrine specific gravity 1.005, no glucose.Urine osmolality: 160 mosmol/kgWhat are the main abnormalities?
55Case Study #3 Laboratory studies Major abnormalities1) Hypernatremia2) Polyuria (inappropriately dilute urine)What is the most likely explanation?
56Case Study #3 Diabetes Insipidus DiagnosisCentral Diabetes insipidus1) Polyuria2) Inappropriately dilute urine(urine osmolality < serum osmolality)May be see with midline defectsFrequently occurs in brain dead patientsWhat should you do to treat this child?
57Case Study #3 Diabetes Insipidus TreatmentAcute: Vasopressin infusionChronic: DDAVP (desmopressin)WarningClosely monitor for development of hyponatremia
58Case 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 BIDPE: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.
59Case Study #4What is your differential diagnosis? What diagnostic studies would you order?
61Case Study #4 Laboratory studies Serum studiesSodium 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/LOtherWBC: 13k (60% P, 30% L), HCT 35%, PLT 223kChest radiograph: no abnormalitiesWhat are the electrolyte abnormalities?
621) Hyponatremic dehydration Case Study #4 DiagnosisMajor abnormalities1) Hyponatremic dehydration2) Hypoglycemia3) Hyperkalemia, mild4) Acidosis5) AzotemiaWhat is the most likely explanation for these findings?
63Case Study #4 Adrenal Insufficiency 1o adrenal insufficiency (Addison’s disease)Adrenal gland destruction/dysfunction (ie. autoimmune, hemorrhagic)most common in infants 5-15 days old2nd adrenal insufficiencyACTH deficiency (ie. panhypopituitarism or isolated ACTH)“Tertiary” or “iatrogenic”Suppression of hypothalamic-pituitary-adrenal axis (ie. chronic steroid use)
64Case Study #4 Adrenal Insufficiency ManifestationsMajor hormonal factor precipitating crisis is mineralcorticoid deficiency, not glucocorticoid.Dehydration, hypotension, shock out of proportion to severity of illnessNausea, vomiting, abdominal pain, weakness, tiredness, fatigue, anorexiaUnexplained feverHypoglycemia (more common in children and tertiary)Hyponatremia, hyperkalemia, azotemia
65Case Study #4 Adrenal Insufficiency DiagnosisCritical level of suspicion in all patients with shock1) Demonstration of inappropriately low cortisol secretionBasal morning level vs. random “stress” level2) Determine whether cortisol deficiency dependent or independent of ACTH secretion. ACTH, cortisol 1o adrenal insufficiency ACTH, cortisol 2nd or tertiary insufficiency3) Seek a treatable cause
66Case Study #4 Adrenal Insufficiency What should you do to treat this child?
67Case Study #4 Adrenal Insufficiency TreatmentDo not wait for confirmatory labsFluid resuscitation - isotonic crystalloidTreat hypoglycemiaGlucocorticoid replacement - hydrocortisone in stress doses mg/m2 (1-2 mg/kg) IVConsider mineralocorticoid (Florinef®)
68Case 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?
69Case Study #5 Hyperkalemia TreatmentImmediately repeat serum potassium.Do not wait for confirmatory labs especially if EKG changes present.AnticipatoryStop potassium administration including feeds
70Cardiac MonitorWhat is this rhythm?What is your immediate treatment?
72Case Study #5 Hyperkalemia Treatment (cont) Control effectsAntagonism of membrane actions of potassiumCalcium chloride mg/kg over 5 minutes; may repeat x2Shift 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
73Case 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?
74Case Study #6 Laboratory studies Serum studiesSodium 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/dLOtherEKG: Unifocal PVC’sWhat is the main abnormality?
75Case Study #6 Laboratory studies Major abnormality1) HypokalemiaWhat would you do now?
76Case Study #6 Hypokalemia TreatmentOralSafest, although solutions may cause diarrheaIVPeripheral as continuous infusion. Avoid temptation to rapidly bolusCentral: 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)
77SummaryDisorders 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
78In hospitalized patients, the ongoing administration of hypotonic maintenance fluids may result in hyponatremiaHyponatremia 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 parametersIn 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
79Maintenance Therapy Caloric expenditure varies with body weight: Weight less than 10 kg — approximately 100 kcal/kg of caloric expenditure/ dayWeight 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 kgWeight 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.