3Total Body Water (TBW) Varies with age, gender, body habitus 55% body weight in males45% body weight in females80% body weight in infantsLess in obese: fat contains little water
4Body Water Compartments Intracellular water: 2/3 of TBWExtracellular water: 1/3 TBW- Interstitial water: 3/4 of extracellular water- Intravascular water: 1/4 of extracellular waterWater is present in plasma, interstitial and intracellular fluid volumes and passes freely between compartments, under the influence of osmotic pressure gradients.Total Body Water (TBW) in liters = Wt (Kg) x .6 (m) . 5 (f)=70 x .6 = 42 L
5TBW 42 L Intracellular Fluid 2/3 of TBW 28 L Extracellular Fluid Intravascular Fluid1/3 of ECF5 LInterstitial Fluid2/3 of ECF9 L
6NORMAL FLUID AND ELECTROLYTE REQUIREMENTS Average adults in temperate climates lose between 2.5 and 3 litres of water per day,( mls urine, 1000mls insensible loss from lungs and skin, 100mls in the faeces).Normally fluid enters the body orally although around 200mls/day is produced from metabolic processes.Average adults lose about 1.5mmol/kg/day of sodium ions and 1 mmol/kg/day of potassium ions in the urine.If a patient is nil by mouth then normal daily requirements may be provided by:◙ 1000mls Normal saline 0.9%◙ mls Dextrose 5%◙ 60 mmol KC1
12They are the primary fluid used for IV therapy. Crystalloids contain electrolytes (e.g. sodium, potassium, calcium, chloride) but lack the large proteins and molecules found in colloids.Crystalloids are classified according to their tonicity into:Hypertonic , Isotonic ,and Hypotonic
14Lactated Ringer’s and Normal Saline LR and NS : they contain sodium in similar concentrations as found in the plasma so they are the most common isotonic solutions used for fluid replacement because of their immediate ability to expand the volume of circulating blood.They are rapidly and evenly distributed throughout the extracellular space, with only 25-30% remaining in the intravascular compartment.So it is recommend that for every1 liter of blood lost, 3 liters of an isotonic crystalloid be administered for replacement.
155% Dextrose in waterD5W : Is an isotonic carbohydrate that contains glucose as the solute.It is useful in supplying sugar, which is used by the cells to create energy.once D5W ( and other Crystalloids which contain a lower concentration of sodium than Plasma as 0.18% saline with 4% glucose) administered IV , they are distributed throughout the total body water after the glucose has been metabolised .
17They are IV fluids that contain solutes of high molecular weight particles derived from: gelatin (gelofusine, haemaccel),Protein (albumin solutions)starch (hetastarch)The high molecular weight particles are so large that they cannot pass onto the cells.Colloid solutions remain longer intravascularly and can significantly increase the intravascular volume.They should be given in a volume equivalent to the estimated blood lossalso colloids have the ability to attract water from the cells into the blood vessels and this can cause cell dehydration.
19crystalloids colloids inexpensive and non-allergic greater expense, and allergic reactions (gelatins)not associated with transmission of infection, impairment of coagulation orcross matching.infection risk (HAS), coagulopathy (dextrans and starches), impaired cross matching (dextrans), and reduction in ionised calcium (HAS).They are more effective at replacing depleted ECFpreferentially expand plasma volume rather than interstitial fluid volumeShort lived haemodynamic effectsRemain longer intravascularlyWhen used for massive fluid resuscitation they invariably produce peripheral oedema and occasionally pulmonary oedema.In disease states associated with increased alveolar capillary permeability (sepsis, ARDS), infusion of colloid may aggravate pulmonary oedema. Similarly capillary leakof infused colloid in head injuries may cause increased cerebral oedema and increased intracranial pressure.
22Oxygen delivery to the tissues is primarily a function of haemoglobin level, haemoglobin oxygen saturation and cardiac output.Ensuring an adequate haemoglobin level and intravascular volume is therefore vital for oxygen delivery.Transfusion of one unit of packed red cells (volume 300ml Hct 60-70%) will raise Hb by 1 to 1.5g/dl.blood products includes (platelets, packed red blood cells, plasma, cryoprecipitate)
24Synthetic fluids that carry and deliver oxygen to the cells. These fluids, remain experimental.It is hoped that oxygen-carrying solutions will be similar to crystalloid solutions in cost, storage capability, and ease of administration, and be capable of carrying oxygen, which presently can only be accomplished by blood or blood products.
25ASSESSMENT OF HYDRATION STATUS AND INTRAVASCULAR VOLUME
27reflects loss of water.This may come from extracellular fluid (ECF) and intracellular fluid (ICF) depletion.Hydration status and intravascular volume is assessed by the patient’s history, examination, test results and response to intravenous fluid administration.In perioperative care the emphasis is to use IV fluids to maintain the circulating volume and tissue oxygen delivery.The patients undergoing major surgery in a dehydrated, un-resuscitated state do worse than those who have received adequate IV fluid preoperatively.
32American society of Anaesthesiologists (ASA) guidelines: No solid food for 6 h preoperatively.No formula milk and non clear fluid for 4 h preoperatively.No clear fluids and breast milk for 2h preoperatively.
34Perioperative fluid replacement is divided into maintenance fluidsfluid deficit (pre-existing losses ) NPO and other deficits: NG suction, bowel preparation)third space lossesreplacement of intraoperative loss (Replacement of blood loss, and Special additional losses)
35Maintenance Fluid Requirements Insensible losses such as evaporation of water from respiratory tract, sweat, feces, urinary excretion.Adults: approximately 1.5 ml/kg/hr“4-2-1 Rule”4 ml/kg/hr for the first 10 kg of body weight2 ml/kg/hr for the second 10 kg body weight1 ml/kg/hr subsequent kg body weight
36Deficits FluidNPO deficit = number of fasting hours NPO x maintenance fluid requirement.Bowel prep may result in up to 1 L fluid loss.Measurable fluid losses, e.g. NG suctioning, vomiting, colostomy output.½ the amount given in the 1st hour¼ in the 2nd hour¼ in the 3rd hour
38replacement of intraoperative loss Blood Loss :Replace 3 cc of crystalloid solution per 1 cc of blood lossWhen using blood products or colloids replace blood loss volume per volumeSpecial additional losses:Ongoing fluid losses from other sites:- gastric drainage- colostomy output- diarrheaReplace volume per volume with crystalloid solutions
4062 y/o male, 80 kg, for hemicolectomy NPO after 2200, surgery at 0800received bowel prep3 hr. procedure500 cc blood lossWhat are his estimated intraoperative fluid requirements?
411- maintenance fluid 4 x x x 60 = 120 ml/hr = 360 ml/3hrs 2- deficit fluid 120 ml x 10hrs (fasting)+1000ml (bowel prep ) = 2200ml 1100 ml in the 1st hr 550 ml in the 2nd hr 550ml in the 3rd hr 3- Third Space Losses 6 ml/kg/hr x 3 hrs = 1440 mls 4- Blood Loss 500ml x 3 = 1500ml Total = =5500mls crystalloid