Fluid and Electrolytes in Surgical Management

Water in Human body

• Adult male has 60% of lean body weight as water.

• While in females its 50% of lean body weight and in new born its 80%.

Total Body Water = 0.6 >< Lean Body Weight (in male)

0.5 >< Lean Body Weight (in female)

• Muscles & solid organ contain more water and fat & bone almost lack water.

Compartmental water distribution

• Extra cellular 1/3

20% Plasma

80% Interstitium

• Intra cellular 2/3

Physiology of body fluids

• Osmolarity =2 Na+ + Glucose/18 + BUN /2.8

• Approximately 2 liter of fluid intake daily intake

75% oral water

25% food

Daily 3-5 g salt

• Out put

1 liter in urine

250 ml stool

600ml insensible loss from lung and skin

A minimum of 500ml urine daily

For the ‘average’ 70 Kg manTotal body water is 42 L (~60% of body weight)

28 L is in the intracellular and 14 L in the extracellular compartments

The plasma volume is 3 L

The extravascular volume is 11 L

Total body Na+ is 4200 mmol (50% in ECF)

Total body K+ is 3500 mmol (only about 50-60 mmol in ECF)

Normal osmolality of ECF is 280 –295 mosmol/kg

Maintenance requirementsDaily maintenance fluid requirements vary between individuals.

70 Kg male = 2.5 - 3.0L water,120 – 140 mmol sodium and 70 mmol potassium

40 Kg woman = 2.0L water,70 – 90 mmol sodium

and 40 mmol potassium

children0-10 kg is 100 ml/kg

10-20 kg is 1000 ml + 50 ml/kg for each kg > 10>20 kg is 1500 ml + 25 ml/kg for each kg > 20

Volume deficit

1. Naso gastric suction

2. Vomiting

3. Diarrhea

4. Fistula

5. Burn

6. Peritonitis

7. Soft tissue injury

8. Intestinal obstruction

9. Prolonged surgery

Features of volume deficit

1. Weight loss

2. Decreased skin turgor

3. Tachycardia

4. Hypotension

5. Collapsed vein

6. Oliguria

Volume excess

1. Iatrogenic

2. Renal dysfunction

3. Congestive heart failure

4. Cirrhosis

Features of volume excess

1. Weight gain

2. Peripheral edema

3. Increased central venous pressure

4. Distended neck veins

5. Murmur

6. Pulmonary edema

Electrolyte imbalance

• Hyper nateremia

• Hypo nateremia

• Hyper kalemia

• Hypo kalemia

Hyper nateremia

• Causes:A. Hyper volemic1. Iatrogenic overloading with Na containing fluids.2. Excess mineralocorticoidB. Normo volemic1. Renal (Diabetes insipidus,diuretic and renal disorders)2. Non renal (GI losses and skin)C. Hypo volemic1. Renal (Diabetes insipidus, adrenal failure, osmotic

diuretics and Renal tubular disorders)2. Non renal (Fever, tracheostomy, diarrhea)

Correction

• Calculate water deficit

= serum Na -140 >< Total body water

140

D5%, D 5% in 0.25% NS

Cerebral edema, herniation

Hyponatremia• Causes:1. Fluid overloada. Iatrogenic over administration of hypotonic fluids

b. Excess oral intake of water or hypotonic fluidsc. Drugs like Tricyclic antidepressant, antipsychotics and ACE inhibitorsd. Post operative patients due to high ADH.

2. Fluid depletiona. Decreased sodium intakeb. GI losses like vomiting, diarrhea, nasogastric suctionc. Renal loss- high urinary sodiumFeatures of dehydration

3. Excess solutes a. Hyper glycemiab. Excess mannitol administration

4. Pseudo hyponatremiaa. Hyper lipidemiab. Hyper proteinemia

Correction

• Calculate Na+ deficit

Deficit = (140- Serum sodium) >< TBW

Correct 0.5mEq/L to 12 mEq/L in a day

Fast correction can lead to Pontine myelinosis

Hyper kalemiaCausesA. Increased intakea. Supplementsb. Transfusionc. Hemolysisd. Rhabdomyolysise. Crush injuryf. GI hemorrhage

B. Increase release by intact cellsa. Acidosisb. Alteration in extracellular osmolarity

C. Impaired secretion a. Potassium sparing diureticsb. Renal failure

ECG features

1. Peak T wave

2. Flat P wave

3. PR prolongation

4. QRS prolongation

5. Sine wave

Correction

1. Cation exchange resin, kayexalate

2. Glucose and HCO3-, Glucose Insulin

3. If ECG changes occur, Ca++ Cl-

4. Beta agonist

5. Dialysis

Hypo kalemia

CausesA. Decreased intakea. K+ free fluidsB. Increase lossa. Hyper aldosteroneb. DiureticsC. GI lossa. Diarrheab. Vomitingc. RT aspirate

ECG changes

1. U wave2. T wave3. ST segment changes

Correctiona. Potassium deficit in mmol is calculated as given below:

Kdeficit (mmol) = (Knormal lower limit - Kmeasured) x kg body weight x 0.4

b. Daily potassium requirement is around 1 mmol/Kg body weight.c. 13.4 mmol of potassium found in 1 g KCl. (molecular weight KCl = 39.1 + 35.5 = 74.6)

Composition of crystalloids

• 3L of Dextrose saline is not equivalent to 2L 5% Dextrose and 1L Normal saline

• 3L Dextrose Saline = 3L water and 90 mmol sodium• 2L 5% Dextrose saline + 1L Normal saline = 3L water and 154 mmol sodium

Hartmann’s

Solution

Normal

Saline

Dextrose

Saline

Sodium (mmol/

l)131 150 30

Chloride

(mmol/l)111 150 30

Potassium

(mmol/l)5 Nil Nil

Bicarbonate

(mmol/l)29 Nil Nil

Calcium

(mmol/l)2 Nil Nil

Normal saline

• 154 mEq/L

Disadvantages

• Cl- overload

• Hyper chloremic metabolic acidosis

Advantages

• Hypo natremia

• Hypo chloremia

Ringer lactate

• Contain lactate gets converted to HCO3-in liver.

• Advantage

Physiological fluid

• Disadvantage

D isomer shows inflammatory response

Colloids

• Stay in intravascular compartment for long time.

• Disadvantages

Detrimental in severe hemorrhagic shock when capillary permeability is high it may worsen edema

Composition of colloids

Volume effect (%) Average MW (kDa) Circulatory half life

Gelatins (Haemaccel) 80 35 2-3 hours

4% Albumin 100 69 15 days

Dextran 70 120 41 2-12 hours

6% Hydroxyethyl

Starch100 70 17 days

• Monodispersed = All molecules of similar molecular weight

• Polydispersed = Molecules have spread of molecular weights

Albumin

• Monodispersed

• Sterlized pooled human plasma

• Expensive

• May worsen renal failure, pulmonary edema and cause hypersensitivity.

• Long half life

• Accounts for 60-80% of normal plasma oncoticpressure

• No adverse effect on coagulation

Dextrans• Polysaccharides

• Bacteria grown on sucrose medium

• Polydispersed with MW 10-90 kDa

• Reduces plasma viscosity

• Reduces platelet aggregation

• 1-5% develop anaphylaxis

Gelatins• Polypeptides• Bovine collagen• Not approved in US• Polydispersed with MW ~35 kDa• Rapidly lost from vascular space

Hydroxyethyl starch• Synthetic polysaccharide polymers derived from

amylopectin• Polydispersed with MW 50-450 kDa• Large molecules engulfed by reticuloendothelial system• Associated with bleeding diathesis, renal dysfunction

and hyperchloremic acidosis

Assessment of adequacy of resuscitation

• Clinical history and observations – Pulse, blood pressure, skin turgor

• Urine output – oliguria < 0.5 ml/kg/hr• CVP or pulmonary capillary wedge pressure• Response of urine output or CVP to fluid challenge• A fluid challenge should be regarded as a 200-250 ml

bolus of colloid• This should be administered as quickly as possible• A response in the CVP or urine output should be seen

within minutes• The size and duration of the CVP response rather the

actual values recorded is more important

GIFTASUP Recommendations (2008) Guidelines for Intravenous Fluid Therapy for Adult Surgical Patients

Preoperative fluid managementRecommendation 4In patients without disorders of gastric emptying undergoing elective surgery clear

non-particulate oral fluids should not be withheld for more than two hours prior to the induction of anaesthesia

Recommendation 5In the absence of disorders of gastric emptying or diabetes, preoperative

administration of carbohydrate rich beverages 2-3 h before induction of anaesthesia may improve patient well being and facilitate recovery from surgery. It should be considered in the routine preoperative preparation for elective surgery

Recommendation 6Routine use of preoperative mechanical bowel preparation is not beneficial and may

complicate intra and postoperative management of fluid and electrolyte balance. Its use should therefore be avoided whenever possible

Recommendation 7Where mechanical bowel preparation is used, fluid and electrolyte derangements

commonly occur and should be corrected by simultaneous intravenous fluid therapy with Hartmann’s or Ringer-Lactate/acetate type solutions

Recommendation 8Excessive losses from gastric aspiration or vomiting should be treated preoperatively

with an appropriate crystalloid solution which includes an appropriate potassium supplement. Hypochloraemia is an indication for the use of 0.9% saline, with sufficient

additions of potassium and care not to produce sodium overload. Losses from diarrhoea, ileostomy, small bowel fistula, ileus or obstruction should be replaced

volume for volume with Hartmann’s or Ringer-Lactate/acetate type solutions. “Saline depletion,” for example due to excessive diuretic exposure, is best managed with a

balanced electrolyte solution such as Hartmann'sRecommendation 9

In high risk surgical patients, preoperative treatment with intravenous fluid and inotropes should be aimed at achieving predetermined goals for cardiac output and

oxygen delivery as this may improve survivalRecommendation 10

Although currently logistically difficult in many centres, preoperative or operative hypovolaemia should be diagnosed by flow-based measurements wherever possible.

The clinical context should also be taken into account as this will provide an important indication of whether hypovolaemia is possible or likely. When direct flow

measurements are not possible, hypovolaemia will be diagnosed clinically on the basis of pulse, peripheral perfusion and capillary refill, venous pressure and Glasgow Coma Scale together with acid-base and lactate measurements. A low urine output can be misleading and needs to be interpreted in the context of the patient’s cardiovascular

parameters above

Recommendation 11Hypovolaemia due predominantly to blood loss should be treated with either a

balanced crystalloid solution or a suitable colloid until packed red cells are available. Hypovolaemia due to severe inflammation such as infection, peritonitis, pancreatitis or burns should be treated with either a suitable colloid or a balanced crystalloid. In

either clinical scenario, care must be taken to administer sufficient balanced crystalloid and colloid to normalise haemodynamic parameters and minimise overload. The

ability of critically ill patients to excrete excess sodium and water is compromised, placing them at risk of severe interstitial oedema. The administration of large volumes

of colloid without sufficient free water (e.g. 5% dextrose) may precipitate a hyperoncotic state

Recommendation 12When the diagnosis of hypovolaemia is in doubt and the central venous pressure is

not raised, the response to a bolus infusion of 200 ml of a suitable colloid or crystalloid should be tested. The response should be assessed using the patient’s

cardiac output and stroke volume measured by flow-based technology if available. Alternatively, the clinical response may be monitored by measurement/estimation of

the pulse, capillary refill, CVP and blood pressure before and 15 minutes after receiving the infusion. This procedure should be repeated until there is no further

increase in stroke volume and improvement in the clinical parameters

Intraoperative fluid management

Recommendation 13In patients undergoing some forms of orthopaedic and

abdominal surgery, intraoperative treatment withintravenous fluid to achieve an optimal value of strokevolume should be used where possible as this may reducepostoperative complication rates and duration of hospitalstay

Recommendation 14Patients undergoing non-elective major abdominal or

orthopaedic surgery should receive intravenous fluid toachieve an optimal value of stroke volume during and forthe first eight hours after surgery. This may besupplemented by a low dose dopexamine infusion

Postoperative fluid, and nutritional management

Recommendation 15Details of fluids administered must be clearly recorded and

easily accessibleRecommendation 16When patients leave theatre for the ward, HDU or ICU their

volume status should be assessed. The volume and type of fluids given perioperatively should be reviewed and compared with fluid losses in theatre including urine and insensible losses

Recommendation 17In patients who are euvolaemic and haemodynamically stable

a return to oral fluid administration should be achieved as soon as possible

Recommendation 18

In patients requiring continuing i.v. maintenance fluids, these should be sodium poor and of low enough volume until the patient has returned their sodium and fluid balance over the perioperative period to zero. When this has been achieved the i.v. fluid volume and content should be those required for daily maintenance and replacement of any on-going additional losses

Recommendation 19

The haemodynamic and fluid status of those patients who fail to excrete their perioperative sodium load, and especially whose urine sodium concentration is <20mmol/L, should be reviewed

Recommendation 20

In high risk patients undergoing major abdominal surgery, postoperative treatment with intravenous fluid and low dose dopexamine should be considered, in order to achieve a predetermined value for systemic oxygen delivery, as this may reduce postoperative complication rates and duration of hospital stay

Recommendation 21In patients who are oedematous, hypovolaemia if present must be treated,

followed by a gradual persistent negative sodium and water balance based on urine sodium concentration or excretion. Plasma potassium concentration

should be monitored and where necessary potassium intake adjustedRecommendation 22

Nutritionally depleted patients need cautious refeeding orally, enterally or parenterally, with feeds supplemented in potassium, phosphate and

thiamine. Generally, and particularly if oedema is present, these feeds should be reduced in water and sodium. Though refeeding syndrome is a risk, improved nutrition will help to restore normal partitioning of sodium,

potassium and water between intra and extra-cellular spacesRecommendation 23

Surgical patients should be nutritionally screened, and NICE guidelines for perioperative nutritional support adhered to. Care should be taken to

mitigate risks of the refeeding syndrome