Aims of peri-operative fluid management
- To identify and replace fluid deficits • To provide maintenance fluid requirements • To identify and replace ongoing losses • To prevent peri-operative fluid instability
Principles of peri- operative fluid management
Assessment of peri-operative fluid status
- Fluid therapy to replace >> Existing deficits (eg: ECF, blood)
>> Obligatory losses (eg: insensible losses via skin /
respiratory tract, urine)
(maintenance fluids)
>> Ongoing losses (eg: blood, intestinal fluids,
evaporative and 3rd space losses)
- Ideally ALL deficits / losses should be replaced with fluids of similar composition and volume
Assessment of peri-operative fluid Status
Clinical assessment by monitoring-
vital signs (heart rate, pulse volume, blood pressure)
Tachycardia, low pulse volume, low blood pressure & pulse
pressure Suggest depletion of ECF volume
capillary refill time of > 2 seconds suggests hypovolaemia
colour / warmth of extremities
Cold, clammy & pale extremities
state of mucous membranes & elasticity of skin
dry mucous membranes with loss of skin turgor
hourly urine output
< 0.5 to 1.0 ml/kg/hour suggests hypovolaemia
period of fasting
Period of fasting in excess of 6-8 hours may incur significant fluid
deficits especially in extremes of age
trends in CVP, if available: values to be interpreted in the
light of underlying clinical setting
Investigations
urine:
Specific gravity > 1.035
osmolality > 1200 mosm/kg
Urinary Na+ < 20 mmol/l
blood:
Packed cell volume (PCV) > 45%
Basic Physiology
Water balance
Osmolality
¬ Normal plasma osmolality -290 mOsm/kg
¬ Osmolality = 2( Na+ +k+ ) + glucose +
(mOsm/kg) urea (mmol/l)
Intravenous fluid replacement
Fluid replacement
1. Maintenance - basic needs
¬ Normal water requirement-30/35ml/kg/day
¬ Sodium-2mmol/kg/day
¬ Potassium-1mmol/kg/day
2. Prior deficits - Fasting , vomiting ,diarrhoea,
NG suction etc.
To identify which compartment / compartments
the fluid has been lost from.
To assess the extent of dehydration.
Bowel losses - ECF
Pure water losses - total body water
Protein loss - plasma
3. Continuing abnormal losses - Blood loss,
NG suction, Third space loss, fever etc.
eEg- Bowel obstruction
- By normal saline with added [k+] - Keep a fluid balance chart - Monitor input and output - Replace 24 hour all fluid out + insensible (urine, drainage, vomitus) loss.
Any patient on IV fluids should have a daily fluid balance, daily electrolyte measurement, new regimen prescribed.
Clinical assessment of dehydration
Investigations
¬ Blood urea
¬ Serum electrolytes
¬ Urine specific gravity & osmolality
¬ Haematocrit - Unreliable in acute blood loss
Three questions
WHAT TO GIVE?
HOW MUCH TO GIVE?
HOW FAST?
WHAT TO GIVE?
HOW MUCH TO GIVE?
How fast?
Give half the requirement in 12 hours and
other half in the next 48 hours.
¬ In severe depletion 20 ml/kg for the 1st
hour. (caution-elderly)
Monitoring
Pulse ,blood pressure ,JVP ,Lung bases
Urine output/hour, serial PCV
Adequacy-urine output of 1ml/kg/hr
Over hydration-jugular venous engorgement ,
lung crepitations ,hypertension
Post op fluid management
QUestions
What is the purpose of dextrose infusion?
What is the best guide to adequate fluid
replacement?
What do you understand by the term
“Third space loss”?
Goals of therapy in hypovolaemia
The idea is to achieve an effective intravascular volume status,,
normal left ventricular filling pressure, normal cardiac output and to
achieve adequate O2 delivery.
>> Improvement in level of consciousness
>> Reduction in pulse rate is the first response to fluid
>> Systolic blood pressure above 90 mmhg
|>> Normal urine output
>> Hb% more than 8 with PCV 20-39%
Assessment of adequacy of fluid replacement
therapy in the peri operative period
vital signs
heart rate, pulse volume, capillary refill time, BP
hourly UOP
e” 0.5 to 1.0 ml/kg/hr
fluid input / output charts
look for negative / positive balance
trends in CVP
response to fluid challenges
Fluid therapy in patients with no significant
peri operative fluid deficit or loss
Majority of patients undergoing minor, elective surgery will not
require fluid therapy in the peri operative period. Those undergoing
prolonged surgery or having a delay in establishing oral feeds will requiremaintenance fluids
- Calculation of maintenance fluid volume: 1 – 2 ml/ kg/hour
• Types of replacement fluids: crystalloids - 0.9%
saline, Hartmann’s solution
* Maintenance fluid volume may need to be restricted in elderly
and those with underlying severe cardio respiratory diseases
Fluid therapy in patients with significant peri
operative fluid deficits
(a) Fluid deficits due to prolonged fasting
(b) Fluid deficits due to the loss of ECF / ICF fluids (dehydration)
(c) Fluid deficits due to the loss of intravascular volume
(blood)
(d) Fluid therapy in patients with on going fluid
losses
(e) Fluid deficits due to loss of blood
(f) Fluid deficits due to losses from GIT
(a) Fluid deficits due to prolonged fasting
These patients may or may not show any clinical evidence of their
fluid deficits. However if they are to undergo prolonged surgery or anyanticipated delay in establishing oral feeds, additional fluids are indicatedto replace the deficits incurred as a result of prolonged fasting
Calculation of fluid volume deficit:
Maintenance fluids (1 – 2 ml/kg/hour) x
number of hours of fast
Types of replacement fluids: Crystalloids - 0.9% saline, Hartmann’s solution
(b) Fluid deficits due to the loss of ECF / ICF fluids (dehydration)
The loss of ECF / ICF fluids over a period of time will give
rise to various degrees of dehydration
eg: - losses from the GIT – vomitus, diarrhoea, nasogastric aspirate,
via fistulae, fluids collected in the intestinal lumen
- losses from the body surfaces – evaporation
of sweat etc.losses via kidneys – polyuria
Types of replacement fluids:
Crystalloids: 0.9% saline, Hartmann’s solution
Colloids: gelatin, starch preparations colloids are preferred to crystalloids in those with severe dehydration & underlying cardio vascular
instability
* In patients with severe dehydration, colloids (20 mls / kg) to
be given initially to correct hypotension followed by crystalloids
Time frame for fluid replacement
50% of the calculated fluid deficit to be replaced with in
the first hour of treatment. Half of the remaining fluids to be given over the next hour. Fluids left over to be given at a rate based on the volume status. Fluid therapy and the assessment of the volume status should go hand in hand to prevent over or under hydration.
(c) Fluid deficits due to the loss of intravascular volume
(blood)
Estimation of intra vascular volume deficit is difficult unless the
losses are revealed. However the monitoring of clinical parameters and
the results of relevant investigations shall guide the fluid therapy
Fluid therapy in hypovolaemic patients:
> Hypotension is treated with colloid 20ml/kg bolus
>Start Crystalloid using a large bore cannula.
> Rapid infusion is recommended in moderately and severely
affected patients (up to 1.5-2 l)
> Blood is given when the blood is available or O Negative
> All fluids should be warm to prevent hypothermia
> Use other measures such as elevation of limbs
> Treat the cause
(d) Fluid therapy in patients with on going fluid
losses
- Fluid losses during surgery include the loss of blood, intestinal fluids apart from • 3rd space and evaporative losses incurred during major surgery of body cavities. • These losses need to be replaced with fluids of appropriate composition and volume to prevent cardio vascular instability
(e) Fluid deficits due to loss of blood
Blood loss may be easy to estimate where it is revealed (eg: suction
apparatus, blood soaked towels / swabs) but difficult when the
loss is concealed (eg: blood in drapes / floor, pelvic & long bone fractures)
(f) Fluid deficits due to losses from GIT
Fluid deficits due to loss of NG fluids
Replace the deficit with equal volumes of Hartmann’s
or 0.9% saline
Fluid deficits due to loss of fluids into the
intestinal lumen
Replace the deficit with isotonic fluids
Fluid deficits due to the evaporation from
exposed surfaces
• Estimation of evaporative losses
Evaporative fluid loss μ surface area exposed
duration of exposure
Fluid loss is approximately 200-250 mls / hour with exposed
body cavities.
Fluid deficits are replaced with 0.9% saline and 5% DW
Correction of electrolyte abnormalities
Potassium
Potassium should be corrected if the serum potassium is less than
3.5 mmol/l
BWx Deficit x 1/5. This is given over 2-4 hours in 250-500 ml of
5% Dextrose
Adult Requirement -- 0.6 – 1mg / kg / day
Treatment of hyperkalaemia
>> 10 ml of 10% calcium gluconate i.v. over10 min.(why ?)
>>10 U of Insulin in 50ml of 50% dextrose i.v.over 30min.
>> NaHCO3 50 mmol
>> Beta 2 agonist
Sodium
Correction of sodium is more difficult than Potassium
Serum Na of <120 needs vigilant correction upto 130 mmol/l
BW x Deficit x1/5 is given at the rate of 1-2 mmol/hour
Hypertonic Saline or Sodium bicarbonate has to be used.
Check fluid in the perio operative section of critical care as well
