PERIOPERATIVE

FLUID THERAPY

INTRODUCTION

Total Body Water (TBW)•Varies with age, gender, body habitus

•55% body weight in males

•45% body weight in females

•80% body weight in infants

•Less in obese: fat contains little water

Body Water Compartments• Intracellular water: 2/3 of TBW• Extracellular water: 1/3 TBW• - Interstitial water: 3/4 of extracellular water• - Intravascular water: 1/4 of extracellular water•Water 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

TBW 42 L

Interstitial Fluid

2/3 of ECF9 L

Intravascular Fluid

1/3 of ECF5 L

Extracellular Fluid

1/3 of TBW14 L

Intracellular Fluid

2/3 of TBW28 L

NORMAL FLUID AND ELECTROLYTE

REQUIREMENTS• Average adults in temperate climates lose

between 2.5 and 3 litres of water per day,(1300-1800mls 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%• ◙ 1500-2000mls Dextrose 5%• ◙ 60 mmol KC1

AIMS OF FLUID THERAPY

Perioperative fluids are required to maintain adequate:HydrationBlood volume and oxygen delivery

Renal functionElectrolyte balanceSplanchnic and hepatic circulation

TypesOf Intravenous Fluids

IV fluids come in four forms:• Crystalloids• Colloids• Blood and blood products• Oxygen-carrying solutions

IV fluids are comprised of

solutes dissolved in a solvent.

Crystalloid Solutions

•They 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

1 2 3

Lactated 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.

5% Dextrose in water•D5W : 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 .

Colloid Solutions

They 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 loss

also colloids have the ability to attract water from the cells into the blood vessels and this can cause cell dehydration.

Crystalloids versus colloids

crystalloids colloidsinexpensive 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 ECF

preferentially expand plasma volume rather than interstitial fluid volume

Short lived haemodynamic effects Remain longer intravascularly

When 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.

Blood and

Blood Products

• Oxygen 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)

Oxygen-CarryingSolutions

Synthetic 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.

ASSESSMENT OF HYDRATION STATUS AND

INTRAVASCULAR VOLUME

Dehydration

reflects 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.

PERIOPERATIVEFLUID MANAGEMENT

Fasting Policy

American 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.

Perioperative fluid replacement

Perioperative fluid replacement is divided into

1. maintenance fluids2. fluid deficit (pre-existing

losses ) NPO and other deficits: NG suction, bowel preparation)

3. third space losses4. replacement of intraoperative

loss (Replacement of blood loss, and Special additional losses)

Maintenance Fluid RequirementsInsensible 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

Deficits Fluid• NPO 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 hour• ¼ in the 2nd hour • ¼ in the 3rd hour

Third Space Losses• Superficial surgical trauma: 1-2

ml/kg/hr• Minimal Surgical Trauma: 3-4 ml/kg/hr

(head and neck, hernia, knee surgery)• Moderate Surgical Trauma: 5-6

ml/kg/hr(hysterectomy, chest surgery)

• Severe surgical trauma: 8-10 ml/kg/hr (or more)(AAA repair, nephrectomy)

replacement of intraoperative loss • Blood Loss :• Replace 3 cc of crystalloid solution per 1 cc

of blood loss • When using blood products or colloids

replace blood loss volume per volume

Special additional losses:• Ongoing fluid losses from other sites:

- gastric drainage- colostomy output- diarrhea

• Replace volume per volume with crystalloid solutions

Example

• 62 y/o male, 80 kg, for hemicolectomy

• NPO after 2200, surgery at 0800

• received bowel prep• 3 hr. procedure• 500 cc blood loss• What are his estimated intraoperative fluid requirements?

1- maintenance fluid 4 x 10 +2 x 10 + 1 x 60 = 120 ml/hr = 360 ml/3hrs2- deficit fluid120 ml x 10hrs (fasting)+1000ml (bowel prep ) = 2200ml 1100 ml in the 1st hr 550 ml in the 2nd hr 550ml in the 3rd hr3- Third Space Losses6 ml/kg/hr x 3 hrs = 1440 mls4- Blood Loss500ml x 3 = 1500mlTotal = 2200+360+1440+1500=5500mls crystalloid