Fluids and Electrolytes Therapy PDF

FLUIDS AND ELECTROLYTES DR AJITE AB INTRODUCTION  The major component of the human body is water  The total body water (TBW) in early fetal life is about 90%  At birth, TBW constitutes about 75-80% of body weight, thereafter, it declines to about 60% by the end of infancy a...

FLUIDS AND ELECTROLYTES DR AJITE AB INTRODUCTION  The major component of the human body is water  The total body water (TBW) in early fetal life is about 90%  At birth, TBW constitutes about 75-80% of body weight, thereafter, it declines to about 60% by the end of infancy and remains so DISTRIBUTION OF TBW  Intracellular compartment (2/3rd of TBW, 30- 40%)  Extracellular compartment (1/3rd of TBW,20- 25%)  The extracellular fluid (ECF) is further distributed into intravascular space as plasma water (5%) and also into the extravascular (interstitial) space (15%)  At puberty, there is increased muscle mass of males and more body fat in females.  fat has very low water content and muscle has high water content, therefore, by the end of puberty, TBW in males remains at 60%, but TBW in females decreases to approximately 50% of body weight.  high fat content in overweight children causes a decrease in TBW as a percentage of body weight.  There is no significant difference in the ECF volume between post-pubertal females and males. BODY COMPOSITION non-water (40%) intracellular fluid (40%) extravascular fluid (15%) intravascular fluid (5%) MAINTENANCE OF FLUID BALANCE  The proportion of total body water varies with age, gender, presence of adipose tissue and disease conditions.  The equilibrium between the intravascular fluid and the interstitial fluid is a product of the balance of hydrostatic, osmotic and oncotic forces, this is necessary for proper tissue perfusion  Net leakage of fluid from the intravascular space is picked up by lymphatic vessels and returned to the bloodstream.  The hydrostatic pressure (HP)of the intravascular space is due to the pumping action of the heart  HP drives fluid out of the intravascular space into the interstitial space at the arterial ends of the capillaries.  Decreased HP e.g in heart failure causes movement of fluid into the venous ends of the capillaries.  Osmotic forces due to electrolytes in body fluid is important in determining the distribution of water between the compartments  Each compartment has one major solute, which because of its restriction within the compartment acts to hold water within it  Extracellular osmole-Na, intracellular osmole-K and plasma proteins help to maintain the extracellular, intracellular and the intravascular volume respectively  Osmotic equilibrum is maintained between the ECF and ICF, since the cell membranes are easily permeable to water  Water moves along osmotic gradient from compartment of low osmolality to that of high osmolality until an equilibrium is reached. WATER BALANCE  In the steady state, water intake must equal water output  Maintenance fluid is the fluid required to keep an individual in homeostasis or steady state  Water loss is usually via evaporation from the skin and respiratory tract (insensible loss) , sweat, urine and stool  Net water intake is derived from ingested water, from food and water produced from oxidation Plasma osmolality and water balance  Plasma osmolality is determined by plasma sodium ion conc and is normally maintained within a narrow limit (285-295mOsm/kg)  The regulatory system is governed by osmo- receptors in the hypothalamus which influence both thirst and secretion of anti diuretic hormone (ADH)  Following an increase in water load/hypoosmolality /hyponatraemia, there is a suppression of the ADH leading to reduction in water reabsorption at the collecting tubule and subsequently there is increase urine output  In hyperosmolality/water deficit, there is increased thirst and ADH sec Plasma osmolality  Plasma osmolality can be measured directly using osmometers as well as indirectly by estimation using the following calculation  Plasma osmolality=2(Na+) +glucose/18 + BUN/2.8  Glucose and blood urea nitrogen (BUN) are measured in mg/dL. (÷by 18 and 2.8 respectively to convert the units into mmol/L). Na is Multiplied by 2 to account for its accompanying anions  Measured values are generally greater than calculated value by 10mOsm/kg, this is osmolal gap  Increase osmolal gap may occur due to increased unmeasured osmoles e.g Hyperglycaemia, mannitol , ethanol  The intravascular fluid has a higher concentration of albumin than the interstitial fluid, and the consequent oncotic force draws water into the intravascular space.  The maintenance of this gradient depends on the limited permeability of albumin across the capillaries.  In children with hypoalbuminemia, the decreased oncotic pressure of the intravascular fluid contributes to the development of edema  Disease states that disrupt the body water balance include;  Hypoalbuminaemia  heart failure  renal impairment  Sequestration of fluid in third space/ interstitial space  Burns  Haemorrhage . ELECTROLYTES  An electrolyte is a substance that dissociates into ions in solution and acquire the capacity to conduct electricity  Sodium, potassium, bicarbonates, chloride, calcium, magnesium and phosphates are examples of electrolytes  The blood electrolytes—sodium, potassium, chloride, and bicarbonate—help regulate and maintain acid-base balance and water balance ELECTROLYTES  Sodium and chloride are the dominant cation and anion, respectively, in the ECF.  Potassium is the most abundant cation in the ICF.  Proteins, organic anions, and phosphate are the most abundant anions in the ICF . Electrolyte distribution Cations mEq/L Anions mEq/L extracellular Na+ 140 Cl- 104 K+ 4 HCO3- 24 Ca+ 2.5 PO4- 2 Mg+ 1.1 Proteins- 14 intracellular K+ 140 PO4- 107 Na +13 HCO3- 10 Mg+ 7 Cl- 3 Proteins- 40 Electrolyte balance  Having electrolytes in the right concentrations (called electrolyte balance) is important in maintaining fluid balance among the compartments.  The amount of fluid in a compartment depends on concentration of electrolytes in it. If the electrolyte concentration is high, fluid moves into that compartment (osmosis). Likewise, if the electrolyte concentration is low, fluid moves out of that compartment.  To adjust fluid levels, the body can actively move electrolytes in or out of cells.  The kidneys help maintain electrolyte concentrations by filtering electrolytes and water from blood, returning some to the blood, and excreting any excess into the urine. hyponatremia  The normal blood level of Na varies between 135- 145mmol/l  Hyponatremia is defined as Na conc below 135mmol/l.  Hyponatremia can result from solute loss (vomiting, diarrhoea, excessive sweating, burns e.t.c) when the replacement fluid is hypotonic or in instances of water retention such as inappropriate ADH secretion  In response to hyperosmolality, there is increased sec of ADH and subsequent enhanced water retention to dilute and expand TBW leading to hyponatremia and hypoosmolality  Etiology of hyponatremia  The etiology of hyponatremia depends on the volume status of the patient VOLUME DEPLETION (CCF, Diarrhoea, diuretics) Decrease in effective circulating volume Reduced GFR and increase in salt and water reabsorption by the proximal convoluted tubule+ secretion of ADH Increased water reabsorption from the collecting tubules and subsequent hyponatremia hyponatremia Hypervolemic hyponatremia-  Characterised by an increase in total body Na and water, however the increase in total body water exceeds that of Na  There is low plasma Na, presence of oedema  Example of such disease condition include liver cirrhosis, congestive cardiac failure and renal failure Hypovolemic hyponatremia  There is deficit in total body Na and TBW with a disproportionately greater Na loss  Characterized by evidence of fluid depletion, hypotension, tachycardia Euvolemic hyponatremia The plasma osmolality is usually normal  Etiology of hyponatremia Hypovolemic Normovolemic hyponatremia (SIADH) Hypervolemic hyponatremia 1. Inflammatory CNS diseases hyponatremia(excess 1. Renal loss- (meningitis, encephalitis) free.water retention) diuretic use, 2. CNS tumors osmotic diuresis, 1. CCF 3.Pulmonary diseases (severe renal salt wasting asthma, pneumonia 2. Liver cirrhosis 2. Extra renal- 4.Drugs e.g 3. Nephrotic syndrome diarhoea, vomiting, cyclophosphomide, vincristine 4.acute/chronic kidney drains, fistula, effusion, ascites diseases SIADH  High level of ADH is secreted at low plasma osmolality  The presence of hyponatremia with high urine osmolality(>100mOsm/kg) and urine Na>20- 30mEq/L confirms the diagnosis  There is impaired excretion of free water because of the ADH secretion, subsequently, urine osmolality exceeds that of the plasma  Management is by fluid restriction Clinical features of hyponatremia  Headache  Nausea and vomiting  Lethargy and confusion The above are early features. Advanced manifestations include;  Seizures  Coma  decorticate posturing  Dilated pupils  Papilloedema  Cardiac arrythmia  Cerebra oedema occurs at Na values 150mEq/L CAUSES  Deficiency of ADH hormone (diabetes insipidus, where the urine SG 1010 and urine osmolality >plasma osmolality)  Excessive intake of Na Features of hypernatraemia  Intense thirst  Lethargy  Coma  Convulsion Complication  Osmotic shift of water from neurons leads to shrinkage of the brain and tearing of the meningeal vessels with intracranial hemorrage Treatment  Rapid correction may result in cerebral oedema  infusion of quarter isotonic saline with5% dextrose  The time for correction is directly proportional to the level of plasma Na, usually not less than 24 hrs  Monitor serum Na 4hrly and value should not fall below o.5mEq/L/hr  Identify and treat the underlying cause hypokalemia  Normal serum concentration is 3.5-5mmol/L  Hypokalemia is defined as serum K 5.5mmol/L CAUSES Renal insufficiency, acidosis, insulin deficiency, hypoaldosteronism, hyperkalemic renal tubular acidosis, old blood transfusion, thrombocytosis, leucocytosis Tissue catabolism- rhabdomyolysis, drugs like spironolactone, ACEi Features of hyperkalemia  Muscle weakness  Cardiac conduction defects- tall tented T waves, short QT interval, widening of QRS complex, loss of P wave Treatment of hyperkalemia  Withhold all K containing fluid, oral intake of K and K sparing medication Use of agents which cause a rapid influx of potassium intracellularly  Calcium gluconate is used in symptomatic patients for cardioprotective effects, as it antagonizes the membrane effects of potassium  Sodium bicarbonate  Insulin and glucose  Salbutamol Treatment of hyperkalemia Removal of K 1. Sodium polystyrene sulfonate, an exchange resin which exchanges sodium for potassium in the gut 2. Dialysis  Treat the cause of hyperkalemia FLUID AND ELECTROLYTE THERAPY There are three classifications of fluid therapy 1. maintenance 2. deficit 3. Replacement  Maintenance fluid therapy is to replace estimated normal physiologic urine output and insensible losses in patients with reduced or no oral intake Deficit fluid  Deficit fluid is that lost by a patient usually prior to medical care in clinical situations such as gastrointestinal illness with vomiting and diarrhea, traumatic injuries with significant blood loss, and inadequate intake of fluids over a period of time. Replacement fluid  Replacement fluids are defined as those given to meet ongoing losses after commencement of medical treatment. E.g. fluid loss in patients with chest tubes in place, uncontrolled vomiting, continuing diarrhea, or externalized cerebrospinal fluid shunts. MAINTENANCE ELECTROLYTES  Electrolytes are determined majorly by renal function, therefore, the patient's clinical status is important when considering electrolyte requirements in children.  Any renal dysfunction requires frequent electrolyte monitoring.  Electrolyte replacement in intravenous fluids generally includes sodium, potassium, and chloride. Dehydration  Dehydration is a common cause of fluid and electrolyte imbalance in children  severity of dehydration can be assessed using parameters such as skin turgor, urine output, buccal mucosa, patient’s weight, tear production, depressed anterior fontanelle and thirst  oral route for fluid therapy is preferred except when it is not clinically indicated  MINIMAL OR NO MILD TO MODERATE SEVERE DEHYDRATION (9% LOSS OF BODY (3–9% LOSS OF LOSS OF BODY SYMPTOM WEIGHT) BODY WEIGHT) WEIGHT) Mental status Well;alert Normal, fatigued or Apathetic, lethargic, restless, irritable unconscious Thirst Drinks normally; Thirsty; Drinks poorly; might refuse liquids eager to drink unable to drink Heart rate Normal Normal to increased Tachycardia, with bradycardia in most severe cases Quality of pulses Normal Normal to decreased Weak, thready, or impalpable Breathing Normal Normal;fast Deep Eyes Normal Slightly sunken Deeply sunken Tears Present Decreased Absent Mouth and tongue Moist Dry Parched Skinfold Instant recoil Recoil in 2 sec Capillary refill Normal Prolonged Prolonged Extremities Warm Cool Cold;mottled;cyanotic Urine output Normal to decreased Decreased Minimal WHO ;Clinical assessment for degree of dehydration associated with diarrhoea is as follows if two or more of the signs in column C are present - the patient has "severe dehydration" if two or more signs from column B (and C) are present - the patient has "some dehydration". patients who fall under column A - "no signs of dehydration" A B C general well, alert restless, irritable lethargic or appearance unconscious eyes normal sunken sunken thirst drinks normally, not thirsty, drinks eagerly drinks poorly, or not thirsty able to drink skin turgor goes back quickly goes back slowly goes back very slowly Types of dehydration  Hypotonic  Isotonic  Hypertonic Depending on the serum sodium value TREATMENT BASED ON THE DEGREE OF DEHYDRATION MINIMAL OR NO DEHYDRATION – replacement of fluid loss  10 kg body weight: 120–240 mL ORS for each diarrheal stool or vomiting episode OR  To replace ongoing losses, 10 mL per kg for every loose stool and 2 mL per kg for every episode of emesis should be administered. MILD /MODERATE DEHYDRATION  Replacement of fluid loss as in instance of no dehydration  Rehydration therapy with ORS ; 50-100ml/kg over 3-4hours  ORT is considered to be unsuccessful if vomiting is severe and persistent (i.e., at least 25 percent of the hourly oral requirement) or if ORT cannot keep up with the volume of stool losses. I.V fluid may become necessary SEVERE DEHYDRATION  Rapid intravenous rehydration is the preferred treatment in this group of patients.  if the patient can drink, give ORS by mouth until the drip is set up.  start 100 ml/kg Ringer's Lactate Solution (if not available normal saline may be used) divided as follows:  infants under 12 months first give 30 ml/kg in 1 hour (repeat once if radial pulse is still very weak or not detectable) then give 70ml/kg in 5 hours  older first give 30 ml/kg in 30 minutes (repeat once if radial pulse is still very weak or not detectable) then give 70ml/kg in 2 1/2 hours SEVERE DEHYDRATION  Monitor the serum electrolyte, urea and creatinine  Monitor the urine output  Give supplemental zinc (10 - 20 mg) to the child, every day for 10 to 14 days.  Feeding should be continued to prevent malnutrition Fluid resuscitation in burns  Use Parkland formula—4ml X total body surface are burnt X Wt (kg)  Give half of your calculated volume in the first 8hours from the time of injury, while the remaining half should be given in the following 16 hours  Target urine output of 1ml/kg/hour, stable vital signs (blood pressure, pulse rate and volume PROBLEM BASED LERNING SESSION  Calculate the maintenance fluid requirement of the following children using Holliday Segar formula I. O.B one year old II. A.B aged 2YRS III. G.C aged 3YRS PROBLEM BASED LERNING SESSION  A 2year old boy was brought to the children emergency with 3days history of vomiting associated with diarhoea, one day history of reduction in urine output and loss of consciousness a) What is the likely diagnosis b) What is the fluid of choice in rehydrating this child c) Mention two important investigations you want to do and state their relevance d) What are the complications to look out for in this child