Fluid management

Duaa Migdadi

Total Body Water

• Water constitutes 50% to 60% of total body weight.

• The body of a healthy 70 kg male contains ?

• Lean tissues such as muscle and solid organs have higher water content than fat and bone.

• TBW is affected by gender and age .

about 42 litres of water.

• The highest percentage of TBW is found in newborns, with approximately 80% of their total body weight comprised of water. This decreases to approximately 65% by 1 year of age and thereafter remains fairly constant

• Estimates of percentage of TBW should be adjusted downward approximately 10% to 20% for obese individuals and upward by 10% for malnourished individuals.

( adipose tissue | muscle mass)

Fluid Compartments

Water is distributed evenly throughout all fluid compartments of the body so that a given volume of water increases the volume of any one compartment relatively little.

BODY FLUID CHANGES

‘Sensible’: these include the loss of electrolytes as well as water. ‘Insensible’: not seen and not easy to quantify ; skin (75%),and lungs (25%) water vapor in exhaled gases , can be increased by such factors as fever, hypermetabolism, and hyperventilation.

Approach to fluid therapy

The Total fluid requirement is composed of :

1. maintenance fluids

2. preoperative deficits ( NPO ,, GI losses ,, blood loss )

3. Intra operative surgical Losses ( evaporation ,, blood loss ,, 3rd space loss)

1. Maintenance.

• replaces the ongoing daily losses of water and electrolytes occurring via physiologic processes (urine formation, sweat, respiration, and stool), which normally preserve homeostasis. • Maintenance >> in all NPO pt .

• So if the patient is kept NPO, there is no input, only output, the patient may enter the surgery with a preexisting deficit that will predisopose to complications, like?

Acute renal failure hypovolemia

Goals for perioperative fluid therapy

• Intravenous fluids are used to replenish fluid losses while maintaning ?

** intravascular volume ( which is essential for adequate perfusion of vital organs )

** cardiac preload

** oxygen-carrying capacity

** coagulation status

** acid-base balance

** electrolyte balance

• Now like we said we lose water and electrolytes, we managed the water now we need to manage the electrolyte loss by either the type of solution of adding electrolytes to the solution.

• Daily requirements for:

• Na: 1-2 mEq/Kg BW/day

• K : 1-2 mEq/Kg BW/day

• CL: 1.5 mEq/Kg BW/day

• A 70 kg man will require 2.5 litres of fluid.

• For a 70 kg man the needed daily sodium is (by the previous formula) (70 x 1.5= 105 mEq) 105 mEq.

• The most common maintenance fluid used is D5 1∕2NS with 20 mEq KCL.

• This fluid contains about 77 mEq/L of sodium and 77 mEq of chloride with the added 20 mEq potassium.

The most common maintenance fluid is D5 ½ NS with 20 or 40 mEq KCL (because as we know normal

saline doesn’t have potassium)

Case

• You are asked by your senior surgical resident to calculate the maintenance fluid of the patient who is post-operative day 2 from an emergency sigmoid resection for volvulus. The patient is 66 years old with a history of hypertension and has excellent cardiac function. He weighs 70Kg, has an orogastric tube and urinary catheter. Which value below is the best estimate of MAINTENANCE FLUID NEEDS for this patient over the next 8 hours?

• A. 650 • B. 780 • C. 880 • D. 950 • E. 1080

•C. In this case the patient who has good

cardiac function will typically receive maintenance fluid based on the 4-2-1 algorithm. 4cc/hr for the first 10Kg, 2cc/hr for next 10Kg, and 1cc/hr per Kg thereafter. (4cc x 10) + (2cc x 10) + (1cc x 50)=40 + 20 + 50 = 110cc/hr.

2. Deficit :

• definition: it’s the fluid that has already been lost,

• Difference between defect and replacement >>

• Difference btw maintenance and deficit>>

replacement which refers to both the deficit + ongoing losses + future losses

Same as maintenance therapy formula, it will give a rough estimate because in

reality we have renal conservation so the deficit will be less.

1) Deficit> normal maintenance rate * length of the fast ( hours).

2) the fluid infusion rate for normal patients should be set to deliver 3-4

times the maintenance rate .so When replacing the deficit we give an

infusion rate higher than the normal maintenance rate until the deficit is

corrected ,,Once its corrected you go back to the same rate as before .

• Now what if the duration of fasting is

unknown or it is known but the patient has

abnormal fluids losses (sweating, diarrhea,

ascites), what will we do?

We will approximate bases on clinical data

(physical exam)

So we look at signs of hypovolemia……skin turgor

,hydration of mucous membranes , fullness of a

peripheral pulse , the resting heart rate , blood pressure

and the orthostatic changes from the supine to sitting or standing positions and urine output.

How to treat ?

• More rational approach is to diagnose that we actually have a deficit then just treat based on restoration of vital signs and maintaining a good urine output (.5-1 ml/kg per hour)in adult and correction of base deficit if present

• To achieve this usually the main stay is 1-2 liters of isotonic fluid, 1 liter bolus/hour followed by a continuous infusion and monitoring

• The fluid use is isotonic crystalloid given ,depending on the particular electrolyte profile

3. Replacement :

• Replacement of fluid pre- and intra-operatively involves knowing which compartment is losing fluid and then replacing with solutions based on the knowledge of the fluid lost.

• Intra operative replacement: A. Evaporation :This can occur during body cavity surgery ,,

most significant with large wounds, especially burns, and are proportional to the surface area exposed and to the duration of the surgical procedure.

B. Blood loss : Depends upon the type and site of surgery.

C. Third space loss

D. gastrointestinal loss

Blood loss

1. Suction container 2. Visually (soaked sponges (4x4), ( lap sponge 100-150ml)) 3. And even serial hematocrit can be done in long surgeries 4. And like we know each ml of blood needs about 3 to 4 ml of

crystalloids or 1 ml of colloid

• ( we prefer to start with crystalloids in replacement of blood loss bcz they're safer .. we don't prefer to use colloids bcz of the side effects ( eg. coagulopathy ,, anaphylaxis .. )

• First-line replacement for significant, acute, or ongoing blood loss,is blood

• Most common way to estimate blood loss during surgery is to measure blood in:

3 ml in the 10 × 10 gauze, 10 mL in the 30 × 30 gauze, and 40 mL in the 45 × 45 gauze.

Third space :

• first ( intra vascular ) and second ( interstitial ) spaces are the constituents of the ECF which are normal physiological compartments

• ‘’third space" its referes to space other than ICF and ECF, examples :

• ** peritoneal cavity ( eg. ascites ) ..

• ** pleural cavity ( eg. pleural effusion ) ..

• ** lumen of the gastrointestinal tract ( as in a patient with ileus ) ..

• ** swelling of the tissues after surgical trauma or burns ..

• When too much fluid from the intravascular space moves into the interstitial or third space (non functional areas) that causes serious problems; hypotention, reduced CO, edema.

• The estimation fluid loss is very hard here, if we have ascites we can do aspiration or maybe nasogastric tube in ileus >> we know amount and composition of that fluid .

Intra- op third-spacing

• Intra op its highly dependent on type of surgery and size of incision!

• Usually replaced by lactated ringer solution. • Small excision: 1-3 ml/kg/hour (like hernia) • Medium excision: 3-7 ml/kg/hour

(uncomplicated sigmoidectomy) • Large incisions: 9-11 ml/kg/hour

(pancreatoduodenectomy) • But these values are only guidelines, and actual

needs vary considerably from patient to patient.

GI loss

• GI losses that exceed 250 mL/day from nasogastric tube suction should be replaced with an equal volume of crystalloid

• The fluids used should be similar in composition to the fluids lost

• In cases of intestinal fistulae, it may be useful to measure the electrolyte content of fistula fluid in order to determine the type of fluid replacement required to maintain balance

• In general, gastric losses should be replaced with D5 ½ NS with 20 mEq K and pancreatic, biliary, largest intestine losses (e.g., diarrhea) and small intestine losses should be replaced with Lactated Ringer (LR) solution.

A brief note

• There is something called Allowable Blood Loss:

• Which is the amount of blood lost that doesn’t need resuscitation

• Which can be calculated by:

• Estimated blood volume (EBV) (75ml/kg in males, 65ml/kg females)

• Initial hemoglobin

• Final hemoglobin

• UP TO 500 roughly

EBV*(Hi-Hf)/Hi

Question

• A 65 year-old patient with a history of jejunal-cutaneous fistula requires an admission. The fistula output over the last 24 hours is 1500cc of watery, non-bloody material. Which of the following solutions would BEST REPLACE the patient’s losses?

• Na(meq) K Ca Cl HCO3

• A. 39 0 0 39 0 (0.25%NaCl)

B. 154 0 0 154 0 (0.9%NaCl)

C. 130 4 3 109 28 (LR)

D. 77 0 0 77 0 (0.45%NaCl)

E. 513 0 0 513 0 (3%NaCl)

• C. High output fistula are defined as those draining > 500cc/day. Small bowel secretions, bile, and pancreatic secretions serve to neutralize gastric acid secretion. Bile contains sodium and chloride, pancreatic secretions contain sodium and bicarbonate. Jejuna lesions are associated with significant losses of Na, Cl, HCO3. Of the solution choices listed above, Lactated Ringers solution provides the best balance of electrolytes and bicarbonate to assist with replacing these proximal intestinal losses.