Dehydration

1. 73: PEDIATRIC DEHYDRATION INTRODUCTION  Less tolerance to fluid/lyte changes b/c of higher metabolic rate in kids versus adults  Turnover of fluids and solute 3Xs that of adult  Higher % TBW (75% in neonate, 65% in child, 60% in adult) APPROACH TO DEHYDRATION: THE FIVE POINT ASSESSMENT...  What is the volume deficit?  Estimation by clinical assessment of % dehydration X body weight  Does an osmolar deficit exist?  Hyponatremic (hypotonic) dehydration = Na < 130  Isonatremic (isotonic) dehydration = Na 130 - 150  Hypernatremic (hypertonic) dehydration = Na > 150  Does an acid - base deficit exist?  Loss of bicarbonate in diarrhea ----> normal anion gap metabolic acidosis  Ketoacidosis (lipolysis- poor oral intake --> increased anion gap met acidosis  Lactic acisosis (tissue hypoperfusion) —> increased anion gap met acidosis  Respiratory alkalosis as compensation for above  Does a potassium disturbance exist?  K+ loss in diarrheal stools  Typical deficits: isonatremic (8-10 mEq/kg), hypoonatremic (8-10 mEq/kg) hypernatremic (0-4 mEq/kg)  Serum K+ not reflective of total bd K+ b/c of shifts (acid/base disturbance)  High K+: K+ replacement needs to be cautious, watch for renal failure  What is the renal function?  Pre-renal versus renal failure: Urine Na, FE Na, urine sediment, etc MAINTENANCE REQUIREMENTS  Fluid losses  50% urine  50% insensible (2/3 derm, 1/3 resp)  Fluid requirement  4:2:1 rule per hour or 100:50:20 rule per 24hr  4cc/kg/hr for 0 - 10kg: 2cc/kg/hr for 10 - 20kg: 1cc/kg/hr for > 20kg  100cc/kg/24hr for 0-10: 50cc/kg/24hr for 10-20: 20cc/kg/hr for > 20kg  Caloric requirement  Same 4:2:1 rule to determine Kcal/kg/hr or 100:50:20 rule for daily caloric requirement  Electrolyte requirements  Na+ requirement is 3mEq/kg/24hr  K+ requirement is 3mEq/kg/24hr  Kidney produces enough bicarbonate therefore not required  Glucose: 5g glucose per 100ml maintenance fluid enough to prevent ketosis  Requirements will increase with fever, ventilation, inc. activity, etc DEFICITS/DEHYDRATION  Loss is mainly from ECF 2.  Estimate by: (wt b/f - wt a/f)/wt b/f = % dehydration.  Rarely have accurate wt b/f :. must estimate clinically  History  Intake: what, how much?  Output: urine, sweat, feces, vomiting? how much?  Lethargic, activity level  Physical Examination  Gen: irritable, restless, lethargic, looks unwell  Vitals: temp, RR, HR, BP, cap refill, wt  H/N: mucous mem, eyes sunken, fontanelle, tearing  Derm: skin turgor  Clinical Estimation (note that 1cc = 1gm)  Mild: 0 - 5% X body weight (5% X 10kg = 500cc)  Moderate: 5 - 10% X body weight (10% X 10kg = 1000cc)  Severe: 10 - 15% (15% X 10 kg = 1500cc) History + History + History + NO physical physical severe physical findings findings findings MILD MODERATE SEVERE % < 5% 6 - 10% > 10% Appearanc e Thirsty, alert, restless Thirsty, drowsy, orthostatic Lethargic, limp, cold Vitals Normal radial pulse and RR, BP normal Rapid but strong radial pulse, increased RR, BP normal Rapid and weak radial pulse, increased RR, BP normal or low H/N Normal fontanelle Moist mucous mem Normal eyes Tears Sunken fontanelle Dry mucous mem Sunken eyes Absent tears Very sunken fontanelle Parched mucous mem Very sunken eyes Absent tears SKIN Cap refill < 2sec No tenting Cap refill 3 - 4 sec Mild tenting Cap > 5 sec Marked tenting GENERAL Normal urine Loss of 40 - 50 ml/kg Reduced, dark urine Loss of 60 - 100 ml/kg Reduce or no urine Loss of > 100 ml/kg 3. PATHOPHYSIOLOGY  Isonatremic (Isotonic) Dehydration: 80%  [Na] between 130 - 150  Roughly equal losses of Na and water  NO change in body tonicity or redistribution of fluid between extra and intravascular spaces  Hyponatremic (hypotonic) Dehydration: 5%  [Na+] is < 130 mmol/L  Sodium loss > water loss  Most common cause is sodium poor replacement of GI loss  Child appears relatively more ill than expected b/c water shifts from ECF to ICF :. there is less intravascular volume and more physical signs  Na < 120: seizures, coma  Cerebral edema can lead to seizures  Hypo-osmolar demyelination syndrome,most commonly seen as central pontine myelinolysis, can occur. Uncertain whether these are due to hyponatremia itself or too rapid correction of Na+. Pathophysiology unknown. Thought to be due to rapid correction in chronic hyponatremia. Neurological findings include fluctuating LOC, behavioral disturbances, convulsions progressing to pseudobulbar palsy and quadraparesis.  Hypernatremic (Hypertonic) Dehydration: 15%  [Na+] > 150 mmol/L  Water loss > sodium loss or increased Na+ intake (incorrect formulas)  Child appears relatively less ill than it is b/c water shifts from ICF to ECF :. there is more relative intravascularvolume and less physical signs  Risk: brain hemorrhage, SZ, coma, death  Do NOT correct rapidly w/ hypotonic solution b/c of brain shifts which can cause massive brain swelling  May have alternating LOC b/w lethargy and hyperirritability  PE: dry, rubbing, doughy skin w/ inc muscle tone (doughy skin b/c hypertonicity of body fluids in subcutaneous tissues)  Risk: intracellular dehydration :. water shifts out of the brain cells. This stress causes production of idiogenic osmols (glycine and taurine) which prevents ongoing water loss from neurons. If serum Na is lowered too quickly, these idiogenic osmols will then attract water into brain cells causing swelling, massive cerebral edema, and intractable seizures. MUST correct serum Na slowly, and remember that tissue/renal perfusion is maintained w/ high Na MANAGEMENTOF SEVERE DEHYDRATION  Approach is ABCs with emphasis on iv access  ALL types of severe dehydration require a fluid bolus of 20 cc/kg of 0.9% NaCl or Ringers  Theoretical risk of acidosis with normal saline: infusion of NaCl dilutes the extracellular HC03- creating a “dilutional acidosis”. Ringers lactate has some HCO3 in it.  Reassess q 5-10 min after bolus and repeat as needed X 2  Avoid glucose containing solutions for initial resuscitation of severe dehydration  If hypoglycemic: give 2ml/kg D25W (children) or 4ml/kg DW10 (infants)if hypoglycemic  Consider colloids (albumin, FFP, synthetics) if renal, cardiac, or pulmonary dz  Consider differential dx of shock if nonresponsive to 3 boluses (>60 ml/kg): septic, spinal, 4. hypovolemic, hemorrhagic, obstructive, cardiogenic, anaphylactic, other ISONATREMIC DEHYDRATION  Phase I (0 - 20min): Bolus 20 cc/kg X 3 prn of normal saline, lactate ringers  Phase II (0 - 8hrs): Infusion with D5W 0.45% normal saline (D5W ½ NS)  Add 20 mEq/L KCL after urine output established  Rate cc/hr = (½ deficit - bolus) + maintenance X 8hrs + ongoing losses 8 hours  Phase III (8-24hrs): Infusion with D5W 0.45%NS  Adjust according to urine output if neccessary; monitor lytes  Rate cc/hr = ½ deficit + maintenance X 16hrs + ongoing losses 16 hours HYPONATREMIC DEHYDRATION  Phase I (0-20min): Bolus 20 cc/kg X 3 prn of NS or LR  Phase II (0-8hrs)  If not seizing ... - administer D5W ½ NS with objective to raise serum Na by no more than 12 mEq/L over 24hrs - no NaCl bolus necessary - rate cc/hr = (½ deficit - bolus) + maintenanceX8hrs + losses 8 hours  If seizing... - Na deficit = (desired - current [Na]) X TBW X weight (kg) - Na deficit = (120 - [Na]) X 0.6 X kg - replace with 3% saline (0.5 mEq/ml or 513 mEq/L) - use 120 as desired Na to prevent rapid overcorrection - proceed with fluids to raise Na by no more than 12 mEq/L over next 24hrs; monitor lytes - after 3% saline, use D5W ½ NS - rate cc/hr = (½ deficit - bolus) + maintenanceX8hrs + losses 8 hours  Phase III (8-24hrs)  DW5 ½ NS  Rate cc/hr =1/2 deficit + maintenance X 16hrs + ongoing losses 16 hours HYPERNATREMIC DEHYDRATION  Phase I: Bolus 20 cc/kg NS X 3 prn  Phase II/III  Treat shock and give fluids to replace deficits over 48hrs (vs 24hr)  Reduce serum Na by no more than 10 mEq/L/24hrs  Dialysis for SeNa > 210 mEq/L  Acceptable solutions: D5W0.45%NS or D5W0.2%NS  NOTE that rate of solution more important than type of solution  Rate cc/hr = (½ deficit - bolus) + maintenanceX24hrs + ongoing losses 24 hours SPECIAL SITUATIONS 5.  Acidosis  Regardless of type of dehydration, pt may b/cm acidotic from lactate secondary to poor perfusion, ketone production, or bicarbonate loss in diarrhea  Most recover spontaneously with rehydration  Consider HCO3- for pH < 7.0 or HCO3 < 10 (debatable)  NaHCO3 deficit = 20 - SeHCO3 X 0.6 X kg  Remember that HCO3 can cause severe K+ shifts and paradoxical CSF acidemia  Do not fully correct acidosis  Potassium  Remember shifts; ddx is mainly GI vs renal loss  Always ensure urine output and renal function before replacing K+  Replace with 20 - 40 mEq Kcl/L  Maximum is 60 mEq/L in peripheral iv  Replace potassium gradually over 2 days ORAL REHYDRATION THERAPY (ORT)  Contraindications to oral rehydration therapy  Severe dehyration/shock  Lethargy  Acute abdomen  Intestinal obstruction  Underlying complicating illness  Failure of oral rehydration therapy  Circulatory collapse  Increasing deficit despite ORT  Deterioration during ORT  Intractable vomiting  Failure to rehydrate in 8hrs  Technique  Rehydrate in ED over 4hrs, reassess  Review contents of pedialyte, WHO solution, gatorade, apple juice, soup, etc  D/C home at 4 hours if rehydrated, continue if not  D/C home or admit at 8 hours  Give 1/4 of target volume Q1hr X 4  Target volumes - mild = 60 ml/kg, moderate = 80 ml/kg - or: deficit + maintenance + ongoing losses  Controversy/Discussion  Why is glucose needed? the absorption of Na occurs by a Na/Glucose cotransporter which remains functional during diarrhea (even secretory)  Is there a role for NG placement and rehydration vs oral vs iv rehydration  Does it make sense to give frequent small volumes/sips to thirsty infant to try to prevent vomiting?  Dehydration with “Vomiting after every drink” ....... some goes up, some goes down. Note studies with administration of drug followed immediately by ipecac: < 50% of drug is recovered thus at least ½ is going down. 6. APPROACH TO PEDIATRIC DEHYDRAITON 1. Initial Resuscitation  Emphasis on iv access and bolus administration of 20 cc/kg prn X3 for severe dehydration/shock 2. Determine % Dehydration (volume of deficit)  Mild: 10% 3. Define Type of Dehydration: osmolar deficit?  Hyponatremic (hypotonic): Na < 130  Isonatremic (isotonic): Na 130 - 150  Hypernatremic (hypertonic): Na > 150 4. Determine Type and Rate of Fluids  Calculate deficit, maintenance, ongoing losses 5. Final Considerations  Does an acid - base deficit exist?  Does a potassium disturbance exist?  What is the renal function? MAINTENANCE 4:2:1 RULE = 0 - 10 kg: 4cc/kg/hr 10 - 20 kg: 2cc/kg/hr > 20 kg: 1cc/kg/hr 100:50:25 RULE = 0 - 10 kg: 100cc/kg/24hr 10 - 20 kg: 50 cc/kg/24hr > 20 kg: 25 cc/kg/24hr 7. DEFICIT HOW DO YOU ASSESS % DEHYDRATION MILD MODERATE SEVERE % < 5% 6 - 10% > 10% Appearanc e Thirsty, alert, restless Thirsty, drowsy, orthostatic Lethargic, limp, cold Vitals Normal radial pulse and RR, BP normal Rapid but strong radial pulse, increased RR, BP normal Rapid and weak radial pulse, increased RR, BP normal or low H/N Normal fontanelle Moist mucous mem Normal eyes Tears Sunken fontanelle Dry mucous mem Sunken eyes Absent tears Very sunken fontanelle Parched mucous mem Very sunken eyes Absent tears SKIN Cap refill < 2sec No tenting Cap refill 3 - 4 sec Mild tenting Cap > 5 sec Marked tenting GENERAL Normal urine Loss of 40 - 50 ml/kg Reduced, dark urine Loss of 60 - 100 ml/kg Reduce or no urine Loss of > 100 ml/kg History + History + History + NO physical physical severe findings findings phys findings DEFICIT = % DEHYDRATION x BODY WEIGHT (1cc = 1gm) 8. 5% dehydrated X 10 kg = 0.05 X 10000cc = 500cc 10% dehydrated X 10kg = 0.10 X 10000cc = 1000cc 15% dehydrated X 10 kg = 0.15 X 10000cc = 1500cc CALCULATIONS IN PEDIATRIC DEHYDRATION CASE 1:  1yr old (10kg) vomiting and diarrhea X 4 days  Slightly drowsy, not lethargic, good tone, warm, tacchycardic, strong pulse, normal BP, dry mucous mem, dry eyes, cap refill 3 sec  Na = 132, K+ = 3.2, HCO3 = 20  What fluid and what rate would you use for the first 24hrs? Assume minimal ongoing losses. CASE 2:  1yr old (10kg) vomiting and diarrhea X 4 days  Lethargic, limp, cold, weak rapid pulse, normal BP, sunken eyes, dry eyes, parched mucous membranes, cap refill 5 sec, marked tenting of skin  Na = 115, K+ = 3.2, HC03 = 20  What fluid and what rate would you use for the first 24hrs? Minimal ongoing losses.  How would your management change if the child seizes? CASE #3:  1yr old (10kg) vomiting and diarrhea X 4 days  Lethargic, limp, cold, weak rapid pulse, normal BP, sunken eyes, dry eyes, parched mucous membranes, cap refill 5 sec, marked tenting of skin  Na = 175, K+ = 3.2, HC03 = 20  What fluid and what rate would you use for the first 24hrs? Minimal ongoing losses. CASE #1: ISONATREMIC DEHYDRATION PHASE I (initial resuscitation) 9.  iv access +/- bolus PHASE II (0 - 8hrs)  Fluid = D5W 0.45% normal saline (D51/2NS)  Add 20 mEq/Kcl after urine output, renal function established  Deficit (moderate dehydration) = 10% X 10kg = 1000cc  Rate cc/hr (½ deficit - bolus) + (maintenanceX8hrs) + ongoing losses 8 hrs (500 cc - 0) + (40cc/hr X 8hrs) + ongoing losses 8 hrs 500 + 320 + 0 = 102 cc/hr 8 hrs PHASE III (8 - 24hr)  Fluid = D5W0.45% normal saline + 20mEq Kcl/L  Rate cc/hr (½ deficit) + (maintenance X 16hrs) + ongoing losses 16hrs (500cc) + (40cc X 16) + 0 = 71 cc/hr 16hrs CASE #1: ISONATREMIC DEHYDRATION  Most common form  Na between 130 - 150 10.  Roughly equal losses of Na and water  NO change in body tonicity or redistribution of fluid between intra and extravascular spaces CASE #2: HYPONATREMIC DEHYDRATION PHASE I  iv access + bolus 20cc/kg NS PHASE II  NOT seizing  Fluid = D5W0.45% normal saline + 20 mEq Kcl/L  Deficit (severe dehydration) = 15% X 10kg = 1500ml  Rate = (½ deficit - bolus) + (maintenanceX8hrs) + ongoing losses 8 hrs (750cc - 200cc) + (40cc/hrX8hr) + 0 = 108 cc/hr 8hrs  Seizing  Fluid = 3% saline bolus  Followed by D5W0.45%NS + Kcl at same rate as above  Na deficit = (desired - current Na) X %TBW X weight  Na deficit = (120 - 115mEq) X 0.5 X 10kg = 25 mEq  3% normal saline is 513 mEq/l or 0.5 mEq/ml  Thus bolus 50 ml  Rule of thumb: 2.5 ml/kg of 3% NS to increase Na by 5mEq/L  PHASE III  Fluid = DW50.45% normal saline + 20 mEq Kcl/L  Rate = (½ deficit) + (maintenance X 16hrs) + ongoing losses 16hrs 11. (750cc) + (40cc/hrX16) +0 = 87 cc/hr 16 CASE #2: HYPONATREMIC DEHYDRATION  Na < 130  Sodium loss > water loss + poor sodium replacement  Cerebral edema: seizures, come  Hypo-osmolar demylination syndrome  Most commonly seen as central pontine myelinolysis  Pathophysiology unknown.  Thought to be due to rapid correction in chronic hyponatremia.  Neurological findings include fluctuating LOC, behavioral disturbances, convulsions progressing to pseudobulbar palsy and quadraparesis.  ? Incidence --------> many case reports in literature CASE #3:HYPERNATREMIC DEHYDRATION PHASE I  Bolus of NS 20cc/kg PHASE II/III  Fluid = D5W 0.45% NS or D5W0.2%NS  Deficit (severe dehydration) = 15% X 10kg = 1500ml  Rate cc/hr = (½ deficit - bolus) + (maintenanceX24hrs) + ongoing losses 24hours (750cc - 200cc) + (1000cc)+ 0 = 65 cc/hr 24 hours 12. CASE #3:HYPERNATREMIC DEHYDRATION  Na > 150  Water loss > Na loss  Correct slowly over 48 hours  Risk: seizures, coma, death  Rapid correction ------> CEREBRAL EDEMA  Hypernatremia: fluid shifts out of cells  Idiogenic osmols (glycine, taurine) prevent water loss from cells  Rapid correction ------> idogenic osmols attract water into cells ---> cerebral edema SPECIAL CONSIDERATIONS ACIDOSIS  Lactic acidosis, ketoacidosis, bicarbonate loss  Corrects itself with rehydration  Respiratory compensation  Forget bicarbonate unless severe pH < 7.0 (?) REPLACE DEFICIT OVER 48 HOURS IN HYPERNATREMIC DEHYDRATION 13.  HC03 deficit = (20 - measured) X 0.6 X weight  Remember K+ shifts and paradoxical CSF acidosis (C02 crosses BBB better than HC03) POTASSIUM  Ensure adequate urine output before replacement  Watch closely with renal failure  20 - max of 60 mEq Kcl/L in peripheral iv ORAL REHYDRATION THERAPY CONTRAINDICATIONS  Severe dehydration, acute abdomen, intestinal obstruction, underlying relevant medical illnesses FAILURE  Circulatory collapse, Increasing deficit despite ORT, deterioration during ORT, intractable vomiting, failure to rehydrate in 8hrs TECHNIQUE  Rehydrate in ED over 4hrs, reassess and d/c home or continue and reassess at 8hrs  Solutions: see table  Target volumes  mild = 60 ml/kg, moderate = 80 ml/kg  or: deficit + maintenance + ongoing losses DISCUSSION  Why is glucose needed?  NG vs oral vs iv rehydration?  “Nothing will stay down”  IV bolus and discharge home