2INTRODUCTIONThe kidneys are responsible for maintaining plasma osmolality within a narrow range.Water is the most important solvent in the composition of the living systems.Total body water is a percentage of the body weight.TBW decreases with age.TBW consists of the ICF and ECF.
3INTRODUCTION CTD At birth TBW is 78% of body wt Drops dramatically within 1st month of lifeEquals adult level of 55%-60% at 1yrECF drops after birth due to neonatal diuresis.ICF increases to achieve adult ratio.Obligatory water loss refers to the minimum intake necessary to maintain fluid balance.
4TBW AND AGE Age Body water % ECF% ICF% Term 75 35-44 33 4-6mo 60 23 37 PubertyAdult
5ECF Constitutes 20-25% of body wt Consists of plasma water which is 5% of body wtinterstitial water dat is 15% of body wtDiffers btw males and females at pubertyMonitored by low( cardiac atria) and high pressure (aortic arch, carotid sinus,JGA)Regulated by the RAA,ANF,ADH.
6ICF Represents the difference btw TBW and ECF Forms 30-40% of body wt It is the sum of fluids in different locations of the body with different functions.
7OTHERSTrans-cellular and other slowly exchangable compartments are of lesser importance under normal conditions.Forms 8-10% of body wtFound in the bone, connective tissue and cartilageIt is not accessible to body fluid regulatory mechanism
8OTHERS CTDTrans-cellular fluid are located in the cerebrospinal, intra-occular, pleural, peritoneal and synovial fluidsTranscellular fluid is influenced by trans epithelial transport.Also described as extracoporeal.
9REGULATION OF BODY WATER Body water balance is regulated by intake and excretionExcretion is the most important in the regulatory mechanismPlasma osmolality is mosmo/kg H20 is the concentration of solute particles and this is constant irrespective of fluctuation of solutes and water intake
10INTAKE REGULATION Thirst is a major defense against fluid depletion. Regulated by a center in the midhypothalamusChange in plasma osmolality as littlle as 1-2% or ECF depletion by 10% stimulates thirstOsmoreceptors located in the hypothalamus, pancreas and hepatic portal vein but the mechanism by which volume depletion induces thirst are not understood.
11EXCRETION Losses of water occurs thru lungs ,skin, git, kidneys. Insensible loss are those lost thru evaporation and is proportionate to the surface area of the body and influenced by enviromental temp, respInsensible loss must be taken into consideration in fluid management in childrenUrinary water excretion is an obligatory one that is needed in body homeostasisObligatory loss is important in osmolality regulation.
12EXCRETION CTDUrinary loss is regulated by ADH and its receptors activity in the collecting duct and the medullary concentration gradient where there is passive re-absorption of waterADH is an octapeptide released from the posterior pitutary fossa in response to stimuli from the hypothalamus.
13FLUID THERAPYFluid therapy when employed orally or parenterally is to maintain or restore volume or composition of body fluids.The goal of fluid therapy is to normalize the ICF and ECF chemical environment for cell and organ to function well.Fluid requirement consists of three categories vizi) maintenanceii) deficitiii) supplementary or ongoing loss
14MAINTENANCE THERAPYThis is a function of metabolic rate changes of which affect h20 production.It replaces usual body losses of fluid and electrolyte.Includes usual insensible loss and the urinary output ml for mlCalculation is based on 100ml/100 cal on the assumption of negligible fecal loss .It is also assumed dat this will also address the renal water loss.
15MAINTENANCE CTD Requirement is as follows Body wt in kg Fluid requirement/dayml/kgml/kg+50ml/kgAbove ml/kg+50ml/kg+20ml/kg*** any wt above 20kg subsequently needs 20ml/kg in addition.
16EXAMPLEWhat is the maintenance fluid requirement of a 2year old with a weight of 20kg1st 10kg =100*10……1000ml+2nd 10kg = 50*10……..500mlTotal fluid = ml
17EXAMPLE CTDCalculate the fluid requirement of a child with a weight of 30kg1st 10kg=100*10=1000ml2nd 10kg= 50*10= 500ml3rd 10kg= 20*10= 200mlTotal = 1700ml
18DEFICIT THERAPYThis includes losses due to disease e.g vomiting ,diarrheaCalculation is based on body weight lossThis loss is based on clinical assessment.
19DEGREE OF LOSS Mild dehydration loss of 3% - 5% of body weight loss of 30ml/kg - 50ml/kg of body weightModerate dehydrationloss of 7%-10% of body weightloss of 70ml/kg – 100ml/kg of body weight
20DEGREE OF LOSS Severe dehydration loss of 10%-15% of body weight loss of 100ml/kg-150ml/kg of body weight
21CLINICAL FEATURES OF FLUID DEFICIT MILD DEHYDRATIONLoss of 3-5% body weightThere is mild thirstDry mucus membraneNo sunken eyesSkin tugor returns normallyBP, HR normalMental status intactUrine output normal
22MODERATE DEHYDRATION Loss of 7-10% of body weight Thirst is marked Absence of tearsDry mucus membraneSunken eyes and fontanelleSkin tugor goes back slowlyReduced urine outputHR ↑,BP↓Irritable mental state
23SEVERE DEHYDRATION Loss of 10-15% of body weight Severe thirst Parched mucus membraneVery sunken fontanelleAnuriaHypotensionDelayed capillary refillLethargy or coma
24MANAGEMENT OF DEHYDRATION Mild and moderate dehydration can be corrected orally.Severe dehydration however needs parenteral therapy cos the patient will be to weak to take enough orally and may even be in shock so iv or intra-osseous transfusion or even intraperitonealParenteral is also needed to prevent renal failure.
25SEVERE DEHYDRATION Therapy is in stages A --- Initial therapy B----Subsequent therapyC----Final
26MX OF SEVERE DEHYDRATION CTD The goal of the initial therapy is to expand the ECF rapidlyThe patient needs 100ml/kg20ml -30ml/kg of IVF is given rapidly this may be repeated if need be this is given over 30minutes or 1Hr or even longer in malnourished children
27The goal of the second or subsequent stage is to complete the existing deficit Require 70-80ml /kg and this is given over 5hrThe on going loss in the case of diarrhea is commenced after completing the lost fluid.
28When the patient is able to take again then you commence the maintenance therapy.
29ELECTROLYTESOsmolality of the body is accounted for by the electrolytes in the body.The electrolytes are Na, K, Cl, Hco3, urea,glucose.Na is the main electrolyte in the ECF alongside the Cl,Hco3, glucose urea as the anionsK is the main electrolyte in the ICF.
30ELECTROLYTES CTD Tonicity efers to the effective osmolality Also reflects the concentration of impermeable solutes in fluid.( Na, glucose)Normal tonicity is mmol/kgTonicity is important in diseases where there is inter-compartmental fluid shiftNeurologic problems are often associated with the fluid shift.Urea and ethanol affect osmolality while mannitol and glycerol affects both osmolality and tonicity.
31MAINTENANCE REQUIREMENTS OF ELECTROLYTES ELECTROLYTES REQUIREMENTNa mmol/kg/dayK mmol/kg/dayCl mmol/kg/dayHco3*** New borns do not require Na,K,Cl in the 1st 24hrs
32SODIUM Sodium is the major cation in the ECF Responsible for maintaining intravascular and interstitial volumes11% is in the plasma pool,29% in the interstitial lymph fluid 2.55 in the icf43% of total sodium is in the bone and only 1/3 of this is exchangeableICF Na is maintained at 10meq/l while ECF is140meq/lFunction includes nerve conduction,cellular nutrition and BP maintenance
33SODIUM REGULATIONThe amt of Na in the body is dependent on the intake and excretion.Regulation of Na intake is poorly understoodDifferent sources of intake which depends on the source as well as ageAbsorption occurs throughout the git minimally in the stomach and maximally in the jejunumAbsorption is aided by Na-k ATPase.
34Na REGULATION CTD Excretion of Na occurs thru sweat, urine, feces Kidney is the principal organ regulatig Na excretion.The above is dependent on the glomerular filtration and the tubular reaborption.67% of tub eab takes place in the PT and LOH ,20% in the asc limb of LOH, 7% in the DT,6% in the CDRegulation occurs mainly thru the RAA
35HYPONATREMIA Refers to serum conc <130meq/l Can occur when the intake of of fluid exceeds the excretory capacity of the kidney.Causes are as followsdecreased ADHreduced gfr,polydipsia, malnutrition, thiazide.
37CF N MX OF HYPONATREMIA Can be either symptomatic or asymptomatic Often times occurs along with dehydration when it is referred to as hypotonic dehydrationIncludes nausea, vomiting,muscle twitchingNa replacement using the formularwt* deficit *0.6Correction done over 24hrs ½ in the 1st 8hrs and the other ½ next 16hrs.
38HYPERNATREMIA Serum Na >150meq/l Results when there is excessive gain of Na usually iatrogenic in improper mixing of infant formulaExcessive loss of body water in diarrhea, feverCauses includelow ADH activity as seen in central DI, nephrogenic DIhigh ADH activity as seen in excessive intake, excessive loss thru sweat,adipsia
39CF N MX OF HYPERNATREMIA **HYPERNATREMIA IS AN EMERGENCYLethargy ,confusion, seizures, ICH, irritability, hypertonia, hyperreflexia,comaECF is preserved due to shift of water from ICF.***DO NOT CORRECT RAPIDLY AS RAPID INTERCOMPARTMENTAL SHIFT IS DANGEROUSRate of Na lowering is at 12meq/l/dayCorrection of fluid deficit is done over hrs.Choice of IVF is ½ normal saline
40POTASSIUM Potassium is the major intracellular cation Essential for cardiac and skeletal musclecontractionBalance is dependent on intake, renal and git excretionECF value of Kis meq/lDifference in K btw the two compartments is maintained by Na-K ATPase
41K REGULATION Regulate by two main processes 1) mechanism which responds to within minutes to plasma changes thus promoting import or export from the icf this include insulin,βadrenergic agonist, acidosis, alkalosis, aldosterone and hyper-osmolality. This they do by inducing a secondary messenger which alters Na-K ATPase2) mechanism responding within hrs to regulate excretion from the body.