INTRODUCTION Distribution of fluids and electrolytes:.Water is by far the most abundant component of the human body..BODY WATER AND AGE: AgeTBWECFICF (%bwt)(%bwt)(%bwt) Prem855530 Term804535 1-3yrs652540 Adults652540
.The fall in the % body weight with increasing age is due to accumulation of fat. Fat is low in water content..Increasing cellular tissue growth and increasing rate of growth of collagen relative to muscle during the early months of life may explain the increase in ICF and decrease in ECF.
FLUID COMPARTMENTS 1.Intracellular (30%-40% of body weight) 2.Extracellular (20%-25% of body weight) Plasma5% of body weight Interstitial 15% of body weight Transcellular 1-3% of body wt eg GI secretions,CSF,Intraocular,pleural,peritoneal 3.Slowly exchangeable compartments (8-10% of body wt). Bone Dense CT Cartilage. This compartment is not accessible to the body fluid regulating mechanisms
Electrolyte distribution in compartments: ECFICF Cations:Na 140mmols/lK 140mmols/l Anions: Cl proteins HCO3sulphates Regulation of Body Water Plasma osmolality=285-295mosm/kg. This is maintained by a finely regulated feedback system involving osmoreceptors. These receptors can be found in the hypothalamus,posterior pituitary,atria,collecting ducts of nephrons
Sources of water – Intake which is stimulated by thirst. - Oxidation of CHO, fat and protein Major stimuli for thirst – plasma osmolality increases of 1-2%. - depletion of ECF vol by ≥ 10%
Basic Fluid and Electrolyte therapy Maintenance: GOAL; Intake=output, zero bal Maintenance fluid req is defined as the volume of daily fluid intake which replaces the insensible losses(from breathing and skin ), and at the same time, allows excretion of the daily production of excess solute load(Ur, Cr, electrolytes etc) in a volume of urine that is of an osmolality similar to plasma.
Major objectives of maintenance fluids are: prevent dehydration prevent electrolyte disorders prevent ketoacidosis prevent protein degradation eg 5% D in maintenance fluids(supplying 17 calories/100ml) will provide ≈20% of the normal caloric needs of the patient. This is enough to prevent starvation ketoacidosis starting and diminishes protein degradation that could occur if the pt received no calories.
The commonly used method for ≈ the water requirement is the Holliday-Segar normogram.It relates water loss to the caloric expenditure. The approach assumes that for every 100 kilocalories metabolized,100ml of water is required. 1 st 10kg → → 100mls/kg/24hrs 2 nd 10kg → → 50mls/kg/24hrs Subs. Kg → → 20mls/kg/24hrs Main electrolytes: aimed at replacing normal urinary loses and provide additional, needed for growth. Na 2-3mEq/kg/day Cl 2-3mEq/kg/day K 2 mEq/kg/day
Conditions that increase Fluid requirement:.phototherapy.radiant warmers.in persistent pyrexia illnesses.abnormal fluid losses.hypermetabolic states.increased urinary vol associated with glycosurea Circumstances that req a reduction maintenance fluid include:.In edematous and antidiuretic states.In sedated or paralyzed pts..In the presence of compromised renal fxn and oligoanuria
DEHYDRATION This occurs when loss of water and salts exceeds the intake. Etiology : vomiting diarrhea burns excess sweating 3 rd space losses eg bowel obstructn DKA Classification : Tonicity Signs and symptoms
Tonicity Isotonic Dehydration Hypotonic Dehydration Hypertonic Dehydration Isotonic Dehydration:.Commonest.Losses of water and electrolytes are proportional..no shift of fluids from ICF to ECF or vice- versa..serum Na 130-150mEq/l
Hypotonic:.loss of salt over a period exceeds loss of water.tonicity of the body fluids reduces..Serum Na < 130mEq/l Hypertonic:.loss of water exceeds loss of salt.commonly in infants < 6 months of age..Serum Na >150mEq/l.Fluid losses are predominantly intracellular..CNS signs and symptoms are common possibly due to intracellular dehydration.
IsoHypo Hyper.Psyche Lethargic Coma Hyperirritable.Pulse Rapid Rapid Mod. Rapid.BP low Very low Mod low
Clinical Correlates of Dehydration SeveritySigns Fluid therapy(mls/kg) Infants Adol. MildSlightly50(5%) 30(3%) dry muc memb,↑ thirst, slightyly ↓ U.O. Mod Dry mucous memb,lethargy little or no U.O. sunken eyes & 100(10) 50-60(5-6%) fontanelle,loss of skin turgor Severe Above+rapid thready pulse no tears,cyanosis,150(15) 70-90(7-9%) rapid breathing, delayed cap refill hypotension, mottled skin, coma
Rehydration Therapy Fluid Replacement : Maintenance + Deficit + Ongoing losses Phase 1 → over 8 hours Phase 2 → over 16 hours SHOCK Types of fluids that can be used:.ORS.Ringers lactate → Na, K,Ca, Cl, lactate.½ Strength Darrows → Na, K, Cl, lactate.4.3% D/S →Glucose, Na,Cl.Normal Saline →Na,Cl.
Indications for IV Therapy: Severe dehydration ± shock Uncontrollable vomiting Prolonged oliguria or anuria Structural or functional GI obstructn Severe diarrhea > 10ml/kg/hr of stools Signs of fluid overload: Puffiness of eyes Cough Tachypnoea Basal crepitations Hepatomegaly
Monitoring:.Input/output.Body weight.Oedema.Palpation of peripheral pulses.Auscultation of heart and lungs.PCV.Blood sugar.Serum urea
ELECTROLYTE DEFICIT CORRECTION Sodium Deficit (Desired – Observed) x wt x0.6 Desired is taken as 140mEq/l Potassium Deficit (Desired – Observed) x wt x0.6 Desired is taken as 4mEq/l Bicarbonate Deficit (Desired – Observed) x wt x0.3 Desired is taken as 20mEq/l Correction of Na must not exceed an increase of 0.5mmol/hr or 10mmol/24hrs. Correction of K, ensure child is making urine, never give K as a bolus and never exceed 40mE/l without ECG monitoring.