Infants maintain a state of positive K balance for growth: 1st 3 months is 1.2mmol/day, 3-12mo is 0.8mmol/day, >1yr is 0.4mmol/day.Discuss routes in (diet and/or IVF or TPN) AND Routes out (poo or pee).
TALK ABOUT THINGS THAT CAUSE K to be FALSELY ELEVATED.Spurious hi K can be from hemolysis, spherocytosis.K also moves out of white cells and platelets after clotting has occurred, so the lab value is usually 0.1-0.5mmol/L higher than true plasma value (which is why a blood gas usually differs from the BMP value). This is rarely significant in most patients, but can be as high as 9mmol/L in patients with marked leukocytosis or thrombocytosis.
The gradient of potassium across the cell membrane is the major determinant of the resting membrane potential, which is the basis for the action potential that is essential for neuronal and muscular function. As the extracellular potassium levels increase in AKI, the gradient and membrane potential are affected, resulting in the clinical signs of muscle weakness and cardiac arrhythmias
For either case, STOP THE K GOING IN! (IVF/TPN/enteral)
Hypokalemia can cause: CV: arrhythmias (usu PAC, PVCs), sinus brady, AV block, others; increased SVR Neuromusc: wekaness, cramps, smooth muscle dysfunction (intestinal & urinary) Renal: dec urinary concentrating ability, dec Na excretion, incr renal ammonium production Endo/Metab: negative nitrogen balance (poor growth), glucose intolerance, decreased aldo release and increased renin release
It’s not usually a sodium deficit, but rather too much water.
What happens with hypernatremia: water moves out of cells to establish osmotic equilibrium, and brain cells shrink. Progressive lethargy, even coma. Intracranial bleeding can occur, and is more common in children. The dehydrated, shrunken brain “hangs” by the meninges in the skull which can tear the delicate bridging veins.
Electrolyte Emergencies for Pediatric Residents July 2010 Jennifer Vick, MD
Cases 1 & 2: Serum K of 7.0 12 yo boy involved in MVC, 3 hours ago Leg was pinned between front passenger seat and door Foley inserted, with urine seen here: 11 do baby presented to ED with fever but was overall well-appearing Sepsis work-up initiated
Potassium Balance DIET or IVF/TPN 98% intracellular Distribution maintained by Na/K ATPase Daily balance Adults: net zero Kids require + K balance for growth (infants>toddlers>kids) CELL 140 mmol/L BLOOD 3.5-5.0 mmol/L SWEAT & STOOL (5-10%) URINE (90-95%)
Most Common Etiologies of True Emergent Hyperkalemia Increased K load Acute Renal Failure ↑ed Tissue Catabolism Tumor Lysis Syndrome Rhabdomyolysis Severe hemolysis Immediately post cardiac surgery Nonoliguric hyper-kalemia of the premature infant
Can be used in recovery from DKA, in patients at risk of refeeding syndrome and in TPN
Disorders of Water Metabolism
Cases 3 & 4: Serum Na 110 18 mo boy with known diagnosis of Bartter’s syndrome, appearing ill after GI illness Initial labs: 110/0.9/76/32/16/0.3 3yo girl got dehydrated during a GI illness Received 20cc/kg NS, then admitted overnight for IVF. Initial lab studies (3pm): 144/5/110/16/28/0.6 Called to bedside at 3am when she is not rousing
Hyponatremia Most common electrolyte abnormality in hospitalized children
SIADH VERY common in hospitalized kids Sosm & Uosm for diagnosis Fluid restriction is primary treatment Often resolves with child’s recovery
Cases 5 & 6: Serum Na 150 13yo girl with severe CP and developmental delay in a group home Has recently not been feeling well, and has had decreased interest in taking po 16yo boy with recent diagnosis of ALL, who developed a hemorrhagic stroke as a complication of dialysis needed for TLS Water intake and UOP each exceed 10L per day
Hypernatremia Breaks down to either 1) Loss of water, or 2) Failure to adequately replace water loss Moritz M, Ayus JC. Disorders of Water Metabolism in Children: Hyponatremia and Hypernatremia. Pediatrics in Review Vol 23, No 11, Nov 2002.
Management of Hypernatremia If ECFV depletion: bolus with NS Subsequent IVF should slowly correct fluid loss Can calculate water deficit and/or monitor serum Na closely H20 deficit: TBW x (Measured Na – Desired Na)/ Desired Na. TBW is 0.6 x wt in kg Possible complication of rapid correction: CEREBRAL EDEMA Generally correct 0.5-1.0mEq/L per hour, and complete correction over 36-72 hours
Cases 7 & 8: Serum Ca 5.5 16yo girl with ESKD with a several year history of non-compliance Presented to ED complaining of leg cramping over past several days that has worsened, and now hand cramping 21 mo boy with FTT, weakness Cries when his mom changes his diaper X-ray of hips/legs showed severe osteopenia and fractures in various states of healing