Intravenous Fluid Therapy: A comprehensive review

Ivan A Jones

Department of General Medicine, Kauvery Hospital, Cantonment, Trichy

Background

Fluid therapy is a medical prescription- the drug, dose, duration, de-escalation—the 4 D’s are significant in medical treatment. In the case of fluids – the volume and electrolytes play a vital role in the therapy. This paper is all about the significance of fluid therapy in the medical management.

Uses of fluid therapy

  • Resuscitation –Hemodynamic stability, restore volume status.
  • Replacement – correcting existing/ongoing loses.
  • Maintenance
  • Fluid creep –drug dilution/fluids given for IV catheter patency

Overview – Distribution of Total Body Water

*Fluid placement in the intravascular compartment is the most important aspect of resuscitation

Daily Fluid Homeostasis

Our armamentarium: IV Fluids and composition

Classification of IV Fluids

FactorsCrystalloidsColloids
PropertyLow-molecular weight salts, dissolved in water, constitute crystalloids.

Eg 0.9%NS,RL
Colloids are high molecular weight molecules that do not dissolve completely in water, nor do they pass freely through the capillary membrane.

Eg Albumin, Dextran, gelatian
Vascular permeabilityHighlow
Plasma oncotic pressureReducedMaintained
Hemodynamic stabilizationTransientProlonged
EdemaPeripheral, interstitial, pulmonaryPulmonary edema
CostInexpensiveMore expensive

Crystalloids

  • Based on tonicity/solute concentration/osmolarity
  • Isotonic
  • Hypotonic
  • Hypertonic
FactorsIsotonicHypotonicHypertonic
Osmolarity/Solute ConcentrationOsmolarity is same as that of serum osmolarityOsmolarity is lower than serum osmolarityOsmolarity is higher than serum osmolarity
Fluid shift across compartmentsNo shift. Stays in the intravascular space, it expands the intravascular compartmentShifts fluid out of the intravascular compartment, hydrating the cellsShifts fluid from the cells into the intravascular compartment
Examples0.9% NS, RL0.45% NS, D5W3% NS

Crystalloids-evolution over time

  • Unbalanced crystalloids (no buffer): Normal saline
  • Balanced crystalloids (have buffer – Lactate): Ringer lactate
  • Multiple electrolyte solutions – Acetate Buffer
    • Isolyte (Braun)
    • Plasmalyte (Baxter)
    • Kabilyte (Fresenius Kabi)

*All the above fluids are capable of staying in the intravascular compartment

Crystalloids PropertiesCrystalloid Indications
Isotonic Fluid.Hypovolemic shock
Unbalanced crystalloid – no base-bufferDehydration -- Water and salt depletion
One litre contains Sodium 154 mEq/L and Chloride 154 mEq/L.Initial fluid therapy in DKA
1 litre contains 9 g of NaCl.Fluid challenge in prerenal ARF
0.9 grams of salt per 100 milliliters of waterHypercalcemia
Very useful to correct both fluid and electrolyte deficit.Diluent for drugs.

Normal saline 0.9 %

Normal Saline vs Plasma

ElectrolytesPlasmaNormal saline
Sodium142154
Potassium4
Magnesium2
Calcium5
Chloride104154
Lactate
Sulphate1
Phospahte2
Bicarbonate27
Protein13
Organic acids6
pH7.45.7

Problems with Saline -when given in large volume disproportionately

  • Sodium is higher
  • Chloride is very much higher
  • There is no base
  • Kidney is very slow at downregulating chloride reabsorption à
  • It effectively dilutes the bicarbonate à Acidosis
  • It can cause hyperkalemia (d/t acidosis)

Problems with hyperchloremia

  • Decreased renal cortical blood flow,
  • Decreased GFR.
  • Reduces gastric perfusion, causing abdominal discomfort.

Ringer Lactate

Isotonic fluid

Most physiological fluid

Balanced crystalloid

One litre contains,

  • Sodium 130 mEq/L
  • Chloride 109 mEq/L
  • Potassium 4 mEq/L
  • Calcium 3 mEq/L
  • Lactate 28 mEq/L —base-buffer

*Good fluid for resuscitation, maintenance

ElectrolytesPlasmaRinger lactate
Sodium142130
Potassium44
Magnesium2
Calcium53
Chloride104109
Lactate28
Sulphate1
Phospahte2
Bicarbonate27
Protein13
Organic acids6
pH7.46.4

Lactate Buffer vs Acetate Buffer

  • Acetate-metabolised in liver, peripheral muscle, heart, kidney.
  • Acetate-faster conversion to bicarbonate.
  • Acetate-no interference with lactate assay interpretation

Crystalloids –Acetate buffer

  • Isolyte fluids –M,P,E
  • Plasmalyte
  • Kabilyte

Isolyte Fluids

TypesDextrose (gms/l)Na (mEq/l)K (mEq/l)Cl (mEq/l)OthersUses
Isolyte G506317150NH4Cl- 70
Isolyte M50403540Acetate- 20
HPO4-15		Maintenance fluid
Isolyte P50252022Acetate- 23
HPO4-3
Citrate-3		Neonates
Isolyte E5014010103Acetate-47, Ca- 5,
Mg- 3,
Citrate- 8

Dextrose Containing Fluids

  • D5W
  • D10W
  • 25%Dextrose
  • D5NS
  • D5 1/2NS
  • Isolyte

These fluids move out of intravascular compartment and replenish intracellular water

Uses: provide calories to the patient (maintanence fluids), hypoglycaemia, Diluent for drugs.

Precaution: Don’t add KCL to dextrose containing fluids.

Hypotonic Fluids

0.45% Normal saline, 5% Dextrose: Shifts fluid out of the intravascular compartment, hydrating the cells

UsesAvoid
Diabetic ketoacidosisIn cerebral edema
Hypernatremia

Hypertonic Fluids

3% Nacl, 5% Dextrose with normal saline: Fluid shift —from the cells into the intravascular compartment.

Uses: Cerebral edema.

Colloids

Large molecules when infused into the vascular space, they remain within the vascular system

Natural: Albumin

Artificial: Dextran, gelatin, hydroxyethyl starch

More effective than crystalloids as plasma volume expanders; 3 times more potent. Can be used in hemorrhagic shock. Do not use in non hemorrhagic shock

Synthetic colloids

*Used in Haemorrhagic shock: Dextran 40 –used in Refractory dengue hgic shock

Clinical Assessment: Fluid Therapy

Clinical examination

  • Dry tongue,
  • Skin turgor
  • CRT-BP-postural hypotension, tachycardia,
  • Edema +/- presence of peripheral edema does not necessarily mean adequate intra vascular volume status
  • JVP, pleural effusion, pulmonary edema
  • Urine output.

Estimating requirements

  • Existing deficit
  • Ongoing Losses-Urine/stools/3rd space loss/fever/drain tubes/dressing soakage
  • Cumulative fluid balance/weight chart.

Periodic assessment-needed

Assessment and grading of dehydration

Skin turgor

  • Normal:Skin quickly returns to its original position when pinched.
  • Mild dehydration:Skin slowly returns to its original position.
  • Severe dehydration:Skin remains tented for an extended period after pinching.

Eyes:

  • Normal:Moist, not sunken.
  • Mild dehydration:Slightly sunken eyes.
  • Severe dehydration:Deeply sunken eyes.

Mucous membranes:

  • Normal:Moist
  • Dehydrated:Dry

Thirst:

  • Normal:Drinks normally, not thirsty
  • Dehydrated:Increased thirst, drinks eagerly

Urine output:

  • Normal:Adequate urine production
  • Dehydrated:Decreased urine output, dark urine color

Mental status:

  • Normal:Alert, responsive
  • Mild dehydration:Slightly lethargic, irritable
  • Severe dehydration:Confused, lethargic, unresponsive

Grading of Dehydration:

Mild dehydration:

  • Usually considered a fluid loss of less than 5% of body weight, with minimal symptoms.

Moderate dehydration:

  • Represents a fluid loss between 5-9% of body weight, with more noticeable signs like increased thirst, sunken eyes, and decreased urine output.

Severe dehydration:

  • Considered a fluid loss exceeding 10% of body weight, including symptoms like rapid heart rate, low blood pressure, significant lethargy, and potential shock.

Fluid Therapy in Common Medical Conditions

1). Maintenance fluid for patients

2). Dehydration

  • Vomiting
  • Diarrhoea

3). Diabetic ketoacidosis.

Maintenance Fluid Therapy

For patients who are hemodynamically stable, but unable to meet their daily fluid requirements due to acute illness, patients who are kept NPO due to medical/surgical reasons

Maintenance fluid regimen

  • Free water, electrolyte, calorie requirements/per day.
  • Water-2 to 2.5 litres,
  • Potassium-20 to 60 mEq K/day
  • NaCl-75 to 175 mEq Na/day,
  • Dextrose-100 gms

Example

40/male, H/0 Insecticide poison is kept NPO on day 1.

2.5 litres fluid adviced;

2 × 500ml of D1/2 NS,

2 × 500 ml of Isolyte M,

1 × 500 ml of RL

Maintenance fluid therapy if inappropriate

  • Hypovolemia
  • Volume overload –peripheral/pulmonary edema.
  • Hyponatremia
  • Hypernatremia
  • Hypokalemia
  • Hyperkalemia

Fluid therapy: Vomiting and Metabolic Abnormalities

 

 

 

 

 

 

 

 

IV. fluids for Vomiting?

1) Normal saline

  • Corrects fluid deficit
  • Reduces aldosterone secretion by replacing plasma volume
  • Corrects hypochloremia directly
  • Decreases bicarbonate re-absorption promotes its excretion

2) Potassium supplementation should be given – 10-20 mEq/hour

Fluid Therapy-Diarrhoea: Metabolic abnormalities.

  • Hypovolemia
  • Sodium Deficit
  • Metabolic acidosis: Loss of HCO3 rich fluid
  • Hyperchloremia: Cl absorbed in exchange of HCO3 which is secreted in the stools.
  • Hypokalemia: Actual serum levels may be normal or high because of acidosis.

Treatment

  1. ORT
  2. IV. Fluids

Ringer Lactate

  • -Best and preferred solution for diarrhea
  • -Contains K+, and lactate is converted to HCO3-
  • -Corrects sodium and water deficit.

Normal saline 0.9%-Not ideal

  • Corrects only Na and Water deficit
  • Too much chloride content.
  • Does not effectively replenish K+ and HCO3.

Diabetic Ketoacidosis

  • Hyperglycemia
  • Acidosis
  • Ketonemia
  • Due to absolute or relative insulin deficiency

DKA Treatment

  • IV fluids to correct hypovolemia—volume deficit–Hypovolemia: 5-8 litres or 100ml/kg
  • Supplementation of potassium – check twice daily
  • Insulin
  • Correct 75 % of the deficit on day one and remaining in subsequent days
  • Switch from NS to D5W and 0.45 % NS at Blood glucose level < 250 mg / dl. &/OR serum sodium is more than 145 meq/l.
  • Treat the precipitating cause.

Learning points

  • IV fluids are indispensable drugs in the medical management of several condtions.
  • In shock due to any cause IV access and fluid management – most often with just Normal Saline is essential to restore and maintain circulation.
  • Crystalloids are cheap and easily available and are recommended first line drugs in most situations
  • During resuscitation use fluids that will fill the intravascular compartment
  • Dextrose containing fluids supply energy and water
  • Frequent reassessment of volume status is necessary – typically every 6 to 12 hr in a sick patient.

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