Fluids and electrolytes
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“I call supplementing with electrolytes and metals: The Electrical Chemistry of the Human” ― Steven Magee, Health Forensics
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Fluids and electrolytes
- 1. FLUIDS AND ELECTROLYTES DR. MUHAMMAD USAMA KHAN
- 3. Osmolality The solute concentration in the body fluid by weight. The number of miliosmoles (mOsm) in a kilogram (kg) of a solution. Normal Plasma Osmolality = 275-295 mOsm/kg
- 4. Fluid Therapy Crystalloids Isotonic; 0.9% NaCl, Lactated Ringer’s Hypotonic; D5W, 0.45% NaCl Hypertonic; 3% NaCl Colloids 5% Albumin, Dextran Blood Products PCs, Platelets, FFPs
- 5. Solutions Na+ K+ Ca2+ Mg2+ Cl- HCO3 - Dextrose mOsm/L ECF 142 4 5 103 27 280-310 Lactated Ringer’s 130 4 3 109 28 273 0.9% NaCl 154 154 308 0.45% NaCl 77 77 154 D5W 50 253 D5+0.45% NaCl 77 77 50 406 3% NaCl 513 513 1026 5% Albumin 130-160 <2.5 130-160 330 25% Albumin 130-160 <2.5 130-160 330 Commonly Used Fluids
- 6. Patient Identification Acute presentations with vomiting or diarrhea, including intestinal obstruction, biliary colic, gastroenteritis. Patients who had been immobile or debilitated for a period before presentation causing reduced fluid intake, like, pancreatitis, pneumonia, prolonged sepsis, acute on chronic vascular insufficiency. Drugs that impair renal response to fluid changes, like diuretics. Patients with low body weight and with overall lower total body fluid volume in whom similar losses have a greater effect.
- 7. Daily Losses Water loss 2500ml/day (insensible losses from skin, respiratory and GI tract, and in urine). ↑ loss in sepsis, ventilation, diarrhea, vomiting, high output fistulas, polyuric renal failure Na+ 100mmol/day in urine. ↑ loss in pyrexias, diarrhea, vomiting, high output fistulas. K+ 80mmol/day in urine. ↑ loss in pyrexias, diarrhea, vomiting, high output fistulas.
- 8. Maintenance Fluid Calculation (Rules) 4/2/1 Rule 4ml/kg for first 10 kg 2ml/kg for next 10kg 1ml/kg for every next kg Example for a 80kg patient, 10kg x 4ml/kg = 40ml 10kg x 2ml/kg = 20ml 60kg x 1ml/kg = 60ml Maintenance rate = 120ml/hour and total fluid per day required is 2880ml
- 9. +40 Rule If the patient weighs more than 40kg, add 40 to the weight and that will be maintenance amount of fluid per hour. Example for a 80kg patient Adding 40 in the weight Total maintenance fluid for this patient will be 120ml/hour. Hence total fluid required in a day will be 2880ml by using this rule. Electrolytes Sodium (Na+): 1-2 mmol/kg/day Potassium (K+): 0.5-1 mmol/kg/day
- 10. Calculation of IV Flow Rates Intravenous fluids must be given at a specific rate, neither too fast nor too slow. The specific rate may be measured as ml/hr, litre/hr or drops/min. To control or adjust the flow rate only drops/min are used. Drop Factor Drop factor is the number of drops in one milliter used in IV fluid administration, also called drip factor. A number of different drop factors are used but the commonest are: Blood Set (10 drops/ml) Regular Set (15 drops/ml) Burette or Peadiatric Chamber (60 drops/ml)
- 11. Calculation of IV Flow Rates Formula: volume(ml) x drop factor / time(min) Example 1500ml IV fluids are to be given over 12 hours. Using a drop factor of 15 drops/min. 1500 × 15 12 × 60 = 31 drops/minute
- 12. Management The goal of fluid therapy is to maintain the urine output of 0.5 – 1.0 ml/kg/day Avoidance of fluid overload, especially in malnutrition, heart failure, and renal insufficiency patients. GI losses that exceed 250ml/day should be replaced with equal volume of crystalloids. The minimum urine volume required to maintain normal BUN and Creatinine is 0.24ml/kg/hr (oliguria is less than 400ml/day) BUN to Cr ratio is helpful in assesment of hydration status, If BUN/Cr more than 20, dry side If BUN/Cr less than 10, wet side
- 13. Assessment of Volume Status History and Examination The dry patient. May have been NPO several days preoperatively, feels thirsty, complains of dry mouth, dehydration could be due to diarrhea or vomiting, low JVP, dry mucous membranes and reduced skin turgor The over-filled patient. No thirsty feeling, raised JVP, normal skin turgor, may have dependent edema, and evidence of pulmonary edema on auscultation Observations Chart The dry patient. May have falling BP, rising pulse, low CVP not rising with fluid challenges, weight several kilos below preoperative weight. The over-filled patient. Not usually tachycardic and has high CVP that rises and plateaues with fluid challenges, BP falling with fluid challenges and weight several kilos above the preoperative weight.
- 14. Assessment of Volume Status Fluid balance chart The dry patient. Usually be in several liters of negative fluid balance, possibly over a few days, with a urine output less than 1ml/kg/hr. The over-filled patient. Will be in several liters of positive fluid balance, possibly over a few days. Urine output may be low because of heart failure or renal dysfunction. Blood results The dry patient. ↑ sodium, potassium, creatinine, and urea The over-filled patient. May have hyponatremia. CXR The dry patient. No evidence of pulmonary edema or effusions. The over-filled patient. May have both pulmonary edema and effusions.
- 15. Sodium (Na+) Normal values: 135 - 145 mEq/l Calculation of Sodium defeict in mEq Total body water x (Desired Na - Serum Na) TBW (Adult Male) = 0.6 x weight (kg) TBW (Adult Female) = 0.5 x weight (kg)
- 16. Hyponatremia Mild (130-138 mEq/l) Moderate (120-130 mEq/l) Severe (less than 120 mEq/l)
- 17. Hyponatremia (depletion) Decrease intake Low Na diet Enteral feeds Increase loss Gastrointestinal Losses Vomiting Prolonged Nasogastric suctioning Diarrhea Renal Losses Diuretics Primary renal disease
- 18. Hyponatremia (dilution) Due to excess extracellular water Intentional: excessive oral intake Iatrogenic: Intravenous Drugs Antipsychotics Tricyclic antidepressants Angiotensin-converting enzyme inhibitors Hyperosmolar Mannitol Hyperglycemia
- 19. Clinical Manifestations Headache Confusion Hyper-or hypoactive deep tendon reflexes Seizures Increased intracranial pressure Weakness Fatigue muscle cramps or twitching Anorexia Nausea Vomiting Watery diarrhea Lacrimation Salivation Oliguria
- 20. Management of Hyponatremia Asymptomatic: increase the sodium level by no more than 0.5-1meq/L/h to a maximum increase of 10meq/L per day Symptomatic: (Na<120meq/L) Increase the sodium level by no more than 1meq/L per hour until the serum Na level reaches 130meq/L or neurologic symptoms are improved
- 21. Hypernatremia Serum Sodium levels more than 145 mEq/l Asymptomatic Symptomatic if more than 160 mEq/l
- 22. Clinical Manifestations Restlessness Lethargy Ataxia Irritability Tonic spasms Delirium Seizures Tachycardia Hypotension Syncope Dry sticky mucous membranes Decreased saliva and tears Oliguria Fever
- 23. Hyperkalemia Increased intake Potassium supplementation Blood transfusions Endogenous load/destruction: Hemolysis Rhabdomyolysis Crush injury Gastrointestinal hemorrhage Impaired excretion of potassium Renal insufficiency/failure
- 24. Clinical Manifestations Nausea/vomiting, colic, diarrhea Weakness, paralysis, respiratory failure Arrhythmias, cardiac arrest ECG changes Peaked T waves (early change) Flattened P wave Prolonged PR interval (first-degree block) Widened QRS complex Sine wave formation Ventricular fibrillation
- 25. Management Potassium removal Kayexalate Oral administration is 15-30g in 50-100 ml of 20% sorbitol Rectal administration is 50g in 200 ml 20% sorbitol Dialysis Shift potassium Glucose 1 vial of D50% and regular insulin 5-10 units intravenous Bicarbonate 1 vial intravenous Counteract cardiac effects Calcium gluconate 5-10 mL of 10% solution
- 27. Hypokalemia Inadequate intake Dietary, potassium-free intravenous fluids, potassium-deficient total parenteral nutrition Excessive potassium excretion Hyperaldosteronism Medications Gastrointestinal losses Direct loss of potassium from gastrointestinal fluid (diarrhea) Renal loss of potassium (gastric fluid, either as vomiting or high nasogastric output) Intracellular-shift (metabolic alkalosis or insulin therapy)
- 28. Clinical Manifestations Ileus, constipation Decreased reflexes, fatigue, weakness, paralysis ECG changes U-waves T-wave flattening ST-segment changes Arrhythmias
- 29. Management Serum potassium level <4.0 mEq/L Asymptomatic, tolerating enteral nutrition: KCl 40 to 100 mEq/day via entral access Asymptomatic, not tolerating entral nutrition Intravenous KCl at rate of 10 to 20 mEq/hour If infused at rate >10meq then cardiac monitoring required. Rate can be 40meq through Central lines.
- 30. Thank You By Dr. Muhammad Usama Khan
Editor's Notes
- Increased losses from lungs in dry atmospheres or in patients with tracheostomy, hence humidification of air is important. This 1500ml/day urine output is warranted for normal functioning kidneys. A minimum of 400ml/day output is required to excrete the end products of protein metabolism.
- D5W is considered a isotonic solution but once the dextrose is metabolized it acts as a hypotonic solution causing the fluid shifts into the cells.
- LR is technically the closest fluid to serum composition. NS is most widely used fluid. With adequate renal function NS prevents rapid cellular fluid shifts during rehydration and excess Na is excreted via kidneys. K should usually to be added only if low serum K is present.