FLUIDS AND ELECTROLYTES

FLUIDS AND ELECTROLYTES J a s leen G r ewal, M D J u ly 2 017 A d a p te d f ro m B indu S waro o p, M D W illiam G r a h a m, M D S a m Lai, M D

FLUIDS & ELECTROLY TES: OBJECTIVES Understand replacement strategies for common electrolytes Potassium Magnesium Phosphorus Calcium Know the common clinical manifestations of electrolyte disturbances Know the common causes of electrolyte disturbances

CASE 1 Mr. Frodo, a 60 y/o male from New Zealand with no significant medical history, presents to the UCI ER for increased fatigue and lethargy. He is noted to have dry mucous membranes and, although he denies any medication usage, in his knapsack is a prescription for Lasix. His K is found to be 3.0. The intern on call, Dr. Acula, stops his Lasix and decides to replace his potassium. 1. What are other manifestations of hypokalemia? 2. What are the most common causes of hypokalemia? 3. How do you replace potassium?

HYPOKALEMIA 1. Clinical manifestations of hypokalemia? Cardiac AV block, PAC, PVC, Vtach/Vfib Which unique wave might you see on ECG? MSK Ascending weakness Rhabdomyolysis (vasoconstriction during exercise) GI Nausea/vomiting Ileus

HYPOKALEMIA 2. What are the most common causes of hypokalemia? GU losses Diuretic usage GI losses Diarrhea Hypomagnesemia

HYPOKALEMIA 3. How do you treat hypokalemia? Oral: Potassium Chloride (most common formulation) Usually patients are also hypochloremic and alkalotic Can be liquid or pill form The liquid has bad taste and the pill is large and hard to swallow 0.1 increase in serum K for each 10 meq given IV Potassium Chloride Can be painful if infusion through a peripheral vein (Goal K Serum K) Serum Creatinine

CASE 1: CONTINUED Mr. Frodo, a 60 y/o male from New Zealand with no significant medical history, presents to the UCI ER for increased fatigue and lethargy. He is noted to have dry mucous membranes and, although he denies any medication usage, in his knapsack is a prescription for Lasix. His K is found to be 3.0. The intern on call, Dr. Acula, stops his Lasix and decides to replace his potassium. Give me the order to replace his potassium deficit?

CASE 1: CONTINUED Dr. Acula checks on Mr. Frodo after 4 hours and, while checking his blood pressure, he notices that Mr. Frodo s hand starts to curl and twist. He starts to mumble I won t make it Sam. Sam... Repeat labs show K of 2.8 and Mg 1.1. 1. What are the common manifestations of hypomagnesemia? 2. What are some common causes of hypomagnesemia? 3. How do you replace magnesium?

HYPOMAGNESEMIA 1. What are the common manifestations of hypomagnesemia? Neuromuscular Tetany (Trousseau s and Chvostek s sign more classic for hypocalcemia) Seizures Delirium Cardiovascular Widening QRS Torsades Electrolytes Hypokalemia Luminal transporters on the collecting ducts are inhibited by magnesium Low magnesium allows high intracellular potassium to efflux in to the urine

F/E: HYPOMAGNESEMIA 2. What are the most common causes of hypomagnesemia? GU losses Chronic diuretic usage GI losses Diarrhea (severe or prolonged)

HYPOMAGNESEMIA 3. How do you replace magnesium? Oral Take 3 tabs/day for mild, 6 tabs/day for moderate Each tab has 60-80 mg of elemental magnesium Magnesium Chloride: preferred, available at UCI Magnesium Oxide: more diarrhea than MgCl Mg Citrate? 0.5 increase for 2g given IV: overused and causes renal wasting of Mg IV Mg causes an abrupt but temporary rise in the plasma Mg, this partially inhibits the stimulus to magnesium reabsorption in the loop of Henle. Up to 50% of infused Mg will be excreted in the urine. In addition, Mg uptake by the cells is slow and therefore adequate repletion requires sustained correction of the hypomagnesemia. (from uptodate.com) If Mg < 1 mg/dl 8 grams over 12 hours If Mg 1-1.5 mg/dl 4 grams over 6 hours If Mg 1.5 2 mg/dl 2 grams over 2 hours Give me the order to replace the patient s Mg

CASE 1: CONTINUED Dr. Acula walks by Mr. Frodo s telemetry and notices a prolonged QT interval. While checking on Mr. Frodo, he notices some mild muscle twitching. Mr. Frodo asks him Where have you taken it? It s MINE! His repeat BMP shows normal K and Mg, but calcium of 7.0. 1. What are the common manifestations of hypocalcemia? 2. What are some common causes of hypocalcemia? 3. How do you replace hypocalcemia?

HYPOCALCEMIA 1. What are the common manifestations of hypocalcemia? Neuropsychiatric Tetany, Seizures Hallucinations and frank psychosis Cardiovascular Hypotension Heart Failure Prolonged QT Arrhythmia

HYPOCALCEMIA 2. What are some common causes of hypocalcemia? Electrolytes Hyperphosphatemia Hypomagnesemia Inhibits PTH secretion in response to hypocalcemia Vitamin D resistance/deficiency Primary PTH disorders Surgery Autoimmune

HYPOCALCEMIA 3. How do you replace hypocalcemia? Oral (~ 1000-1200 mg elemental calcium/day) Calcium Carbonate Calcium Citrate IV (symptomatic or < 7.5 mg/dl) Calcium Gluconate (1-2g over 20 minutes) Calcium Chloride (can cause tissue necrosis) Must treat with slow infusion afterwards 0.5 increase for 1 g given

CASE 1: CONTINUED After infusing Mr. Frodo with calcium, Dr. Acula goes to his coffinlike sleep-room. Nurse Weasley pages him a few minutes later, just as he s about to fall asleep. Hey doctor, Mr. Frodo in room 9 ¾ can t breathe, just FYI Labs show Phosphorus of 1 mg/dl 1. What are the common manifestations of hypophosphatemia? 2. What are some common causes of hypophosphatemia? 3. How do you replace hypophosphatemia?

HYPOPHOSPHATEMIA 1. What are the common manifestations of hypophosphatemia? Lungs Respiratory failure from diaphragm weakness MSK Rhabdomyolysis Dysphagia Neuro Paresthesia or confusion

HYPOPHOSPHATEMIA 2. What are some common causes of hypophosphatemia? Refeeding syndrome Malabsorption Vitamin D deficiency Chronic diarrhea Increased urinary excretion Primary/Secondary Hyperparathyroidism

HYPOPHOSPHATEMIA 3. How do you replace hypophosphatemia? Oral Sodium-Phos (tab/powder, each one = 250 mg or 8 mmol) 1-2 packets (TID or QID, weight based) IV Sodium Phosphate IV If Phos > 1.3 mg/dl 0.2 mmol/kg over 6 hours If Phos < 1.3 mg/dl 0.4 mmol/kg over 12 hours

Mg Chloride @ UCI 64-128mg BID

FLUIDS: OVERVIEW Mr. Frodo returns to UC Irvine and is found to have abnormal CXR and CT Chest concerning for malignancy. He is NPO after midnight for possible bronch and biopsy. He weighs 85 kg. As Mr. Frodo is a bounce-back admission, Dr. Acula places him on D5 ½ NS @ 75 ml/hr Is that the right rate?

FLUIDS: OBJECTIVES Understand daily fluid and electrolyte requirements Differentiate between different fluid preparations Maintenance versus Repletion Know the basic distribution of a fluid bolus

FLUIDS: TOTAL BODY WATER Total Body Water Weight (kg) x 0.6 (Male) or 0.5 (female) 2/3 Intracellular, 1/3 Extracellular ¾ Interstial, ¼ Intravascular Example: 70 kg male TBW = 70 kg x 0.6 = 42 Liters 42L x 1/3 = 14L Extracellular 14L x ¼ = 3.5L Intravascular

FLUIDS: OBJECTIVES Understand daily fluid and electrolyte requirements Differentiate between different fluid preparations Maintenance versus Repletion Know the basic distribution of a fluid bolus

FLUID: DAILY MINIMAL Daily Water output: Urine: 500 ml Skin: 500 ml Respiratory: 400 ml Stool: 200 ml OUTPUT = 1600 ml MINIMAL Daily Water input Ingested: 500 ml Water Content, Food: 800 ml Water Oxidation: 300 ml INPUT = 1600 ml Fever? GI Loss? Average adult 35 ml/kg/day

FLUIDS: OBJECTIVES Understand daily fluid and electrolyte requirements Differentiate between different fluid preparations Maintenance versus Repletion Know the basic distribution of a fluid bolus

FLUIDS: T YPES Na (meq/l) K (meq/l) Cl (meq/l) HCO3 (meq/l) Dextrose (gm/l) Osmolality (mosm/l) D5W 50 278 ½ NS 77 77 154 D5 ½ NS 77 77 50 432 NS 154 154 308 D5NS 154 154 50 586

FLUIDS: T YPES Na (meq/l) K (meq/l) Cl (meq/l) HCO3 (meq/l) Dextrose (gm/l) Osmolality (mosm/l) D5W 50 278 ½ NS 77 77 154 D5 ½ NS 77 77 50 432 NS 154 154 308 D5NS 154 154 50 586

FLUIDS: T YPES Na (meq/l) K (meq/l) Cl (meq/l) HCO3 (meq/l) Dextrose (gm/l) Osmolality (mosm/l) D5W 50 278 ½ NS 77 77 154 D5 ½ NS 77 77 50 432 NS 154 154 308 D5NS 154 154 50 586

FLUIDS: T YPES Na (meq/l) K (meq/l) K (meq/l) HCO3 (meq/l) Dextrose (gm/l) Osmolality (mosm/l) D5W 50 278 ½ NS 77 77 154 D5 ½ NS 77 77 50 432 NS 154 154 308 D5NS 154 154 50 586

FLUIDS: T YPES Na (meq/l) K (meq/l) Cl (meq/l) HCO3 (meq/l) Dextrose (gm/l) Osmolality (mosm/l) D5W 50 278 ½ NS 77 77 154 D5 ½ NS 77 77 50 432 NS 154 154 308 D5NS 154 154 50 586 LR is a common fluid used for pancreatitis and can be used when worried about worsening metabolic acidosis from excessive NS

FLUIDS: OBJECTIVES Understand daily fluid and electrolyte requirements Differentiate between different fluid preparations Maintenance fluid calculation Know the basic distribution of a fluid bolus

FLUIDS: MAINTENANCE What is the goal of maintenance fluid? Replace ongoing losses of water/electrolytes under normal conditions Such as when patient is not eating and afebrile

FLUIDS: MAINTENANCE 3 ways you can calculate rate: Use hard math 35 ml/kg/day x weight (kg) Use easier math: 4-2-1 rule 4 ml/kg/hr for first 10 kg 2 ml/kg/hr for next 10 kg 1 ml/kg/hr for remaining weight Use easiest math! Weight (kg) + 40

FLUIDS: MAINTENANCE Mr. Frodo returns to UC Irvine and is found to have abnormal CXR and CT Chest concerning for malignancy. He is NPO after midnight for possible bronch and biopsy. He weighs 85 kg. As Mr. Frodo is a bounce-back admission, Dr. Acula places him on D5 ½ NS @ 75 ml/hr Is that the right rate?

FLUIDS: MAINTENANCE Is that the right rate? Weight (kg) + 40 85 kg + 40 125 ml/hr

FLUIDS: MAINTENANCE After his biopsy, the patient spikes a temperature to 103 F, HR 110 and BP 80/60. Dr. Acula decides to initiate fluid resuscitation with 2L of ½ NS. Is this the right fluid solution?

FLUIDS: OBJECTIVES Understand daily fluid and electrolyte requirements Differentiate between different fluid preparations Maintenance versus resuscitation Know the basic distribution of a fluid bolus

FLUIDS: CONCEPTS CONCEPTS Free water is essentially distributed across all compartments Sodium is essentially confined in the extracellular space Remember the 2/3 and 1/3, then ¾ and ¼ rule for fluids

FLUIDS: WHERE S THE BOLUS GOING? 1000 ml D5W distributed into Total Body Water Interstitial 255cc Intravascular 85cc (8.5%)!!

FLUIDS: WHERE S THE BOLUS GOING? Free water content ICF ECF Interstitial Intravascular D5W 1000 ml 660 ml 340 ml 255 ml 85 ml (8.5%) ½ NS 500 ml 500 ml 670 ml 500 ml 170 ml (17%) NS 0 0 1000 ml 750 ml 250 ml (25%)

FLUIDS: WHERE S THE BOLUS GOING? Free water content ICF ECF Interstitial Intravascular D5W 1000 ml 660 ml 340 ml 255 ml 85 ml (8.5%) ½ NS 500 ml 500 ml 670 ml 500 ml 170 ml (17%) NS 0 0 1000 ml 750 ml 250 ml (25%) Normal saline has no free water and is confined to ECF space; this is why it is the preferred IVF for resuscitation!

FLUIDS: THE END Mr. Frodo goes home to New Zealand. Dr. Acula follows up with him in a few days and tells him the good news! The mass was just a metal ring and the doctors threw it away.

FLUIDS: SUMMARY Assess DAILY the need for fluids Choose fluids based on weight Recognize the concentration of solutes in each fluid