Presentation on theme: "Fluids & Electrolytes: Created by: Sarah A. Murphy, MD Edited by: Camille Henry, MD and Venee Tubman, MD."— Presentation transcript:
Fluids & Electrolytes: Created by: Sarah A. Murphy, MD Edited by: Camille Henry, MD and Venee Tubman, MD
Fluids and Electrolytes Background – General Princinples Maintenance Therapy Replacement Therapy Important Electrolyte Abnormalities
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
Body fluid compartments PlasmaIntracellular CationsAnionsCationsAnions 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)
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
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) Fluids and Electrolytes: Background
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
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
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
Maintenance Therapy: How do we determine what are the on- going losses that need to be replaced?
Calculating Maintenance Fluid Requirement Per hourPer dayExample: for wt 34kg For each kg up to 104ml/hr100ml/day40ml/hr1000ml/day + For each kg btw ml/hr50ml/day20ml/hr500ml/day + For each kg above 201ml/hr20ml/day14ml/hr280ml/day =74ml/hr1780ml/day Putting these together, we come up with this formula for daily maintenance water requirements…
Maintenance Therapy: What about important electrolytes like Na and K?
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
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
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.
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
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%
Replacement therapy Na deficit: –0.6 x (weight in kg) x (140 – measured Na) –Total Body Water = 0.6 x weight in kg
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
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.
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.
Components of Hydration Fluids CHO (g/dL) Na+ (mEq/L ) K+ (mEq/ L) Cl- (mEq/ L) HCO3 (mEq/ L) mOsm/k g NS LR D5 ½ NS c 20K D5 ¼ NS c 10K ORS Gatorade AppleJuice
Types of Losses Urine: assuming normal kidney function should not cause electrolyte “loss” (i.e., kidney will maintain nl serum lytes) Stool: water loss from stool is neglible in healthy children. Diarrhea = loss of H2O, K+, Na, Cl, HCO3. 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-
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.
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.
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)
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.
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.
Fluid and Electrolyte Emergencies in Critically Ill Children Case Studies:
Case Study #1 HPI: –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.
Case Study #1 What is your differential diagnosis? What diagnostic studies would you order?
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.
Case Study #1 Laboratory studies Serum studies Sodium 126 mEq/LBUN 4 mg/dL Chloride 98 mEq/LCreatinine 0.4 mg/dL Potassium 3.7 mEq/LGlucose 129 mg/dL Bicarbonate 25 mEq/LOsmolality 260 mosmol/kg Urine studies Specific gravity 1.025Sodium 58 mEq/L Osmolality 645 mosmol/kgFeNa 2.4% What are the primary abnormalities?
Case Study #1 Laboratory studies Major abnormalities 1) Hyponatremia 2) Oliguria (inappropriately concentrated urine) What is the most likely explanation for these findings?
Case Study #1 SIADH Manifestations –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
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 !!
Case Study #1 SIADH Treatment –Fluid restriction % of maintenance requirements, be certain to include oral intake. –Daily weights.
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?
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?
Case Study #1 The saga continues Stat labs: Sodium 117 mEq/L What would you do now?
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)
Case Study #2 HPI: 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
Case Study #2 No one can obtain IV access after 15 minutes, what would you do now?
Case Study #2 Place intraosseous line Bolus 40 ml/kg of isotonic saline Reassessment (HR 170, RR 40, BP 75/40) Serum studies Sodium 164 mEq/LBUN 75 mg/dL Chloride 139 mEq/LCreatinine 3.1 mg/dL Potassium 5.5 mEq/LGlucose 101 mg/dL Bicarbonate 12 mEq/L pH 7.07 pCO 2 11 pO HCO 3 8
Case Study #2 What is the most likely explanation of this patients acidosis?
Case Study #2 Metabolic acidosis and the anion gap 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 ( ) = 13
Normal gap (usually hyperchloremic) Increased gap Renal “HCO 3 ” losses GI “HCO 3 ” losses Proximal RTA Distal RTA Diarrhea 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 Case Study #2 Metabolic acidosis and the anion gap
Case Study #3 HPI: –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?
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, ….
Case Study #3 Laboratory studies Serum studies Sodium 155 mEq/LBUN 13 mg/dL Chloride 114 mEq/LCreatinine 0.6 mg/dL Potassium 4.2 mEq/LGlucose 86 mg/dL Bicarbonate 22 mEq/LSerum osmolality: 320 mosmol/kg Other Urine specific gravity 1.005, no glucose. Urine osmolality: 160 mosmol/kg What are the main abnormalities?
Case Study #3 Laboratory studies Major abnormalities 1) Hypernatremia 2) Polyuria (inappropriately dilute urine) What is the most likely explanation?
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?
Case Study #3 Diabetes Insipidus Treatment –Acute: Vasopressin infusion –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.
Case Study #4 What is your differential diagnosis? What diagnostic studies would you order?
Case Study #4 Laboratory studies Serum studies Sodium 130 mEq/LBUN 43 mg/dL Chloride 99 mEq/LCreatinine 0.6 mg/dL Potassium 5.7 mEq/LGlucose 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?
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?
Case Study #4 Adrenal Insufficiency 1 o adrenal insufficiency (Addison’s disease) Adrenal gland destruction/dysfunction (ie. autoimmune, hemorrhagic) most common in infants 5-15 days old 2 nd 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 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
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 1 o adrenal insufficiency ACTH, cortisol 2 nd or tertiary insufficiency –3) Seek a treatable cause
Case Study #4 Adrenal Insufficiency What should you do to treat this child?
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/m 2 (1-2 mg/kg) IV –Consider mineralocorticoid (Florinef®)
Case Study #5 HPI: –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?
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
Cardiac Monitor What is this rhythm? What is your immediate treatment?
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
Case Study #6 HPI: –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?
Case Study #6 Laboratory studies Serum studies Sodium 134 mEq/LBUN 11 mg/dL Chloride 98 mEq/LCreatinine 0.4 mg/dL Potassium 2.4 mEq/LCalcium 9.2 mg/dL Bicarbonate 27 mEq/LPhosphorus 3.2 mg/dL Other EKG: Unifocal PVC’s What is the main abnormality?
Case Study #6 Laboratory studies Major abnormality 1) Hypokalemia What would you do now?
Case Study #6 Hypokalemia Treatment –Oral Safest, although solutions may cause diarrhea –IV Avoid temptation to rapidly bolusPeripheral 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 MgSO 4 )
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
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
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.