"Little poke": IV fluid therapy

IV Fluid Therapy:

The human body contains approximately 40L of H2O. This is divided up amongst several “compartments”.

• ECF (extracellular fluid): The fluid that resides outside of the cells of the body. 1/3 of your body fluid is in this compartment. This includes your intravascular fluid (that which resides in the circulatory vessels), and accounts for about 20% of your ECF (4.5 – 5L). The remainder of your ECF is comprised of the Interstitial fluid that exists outside of the vessels.

• ICF (Intracellular fluid): Fluid within the cells themselves. The remaining 2/3 of your fluid can be found here.

There are 3 types of IV fluids used in fluid therapy.

1. Hypotonic fluids

2. Hypertonic fluids

3. Isotonic fluids

Blood carries a number of solutes (proteins, cells, electrolytes, etc) that determine its osmolality. An isotonic fluid such as 0.9% Normal saline contains sodium at a concentration that is equal to that of blood. Meaning that when it is administered, there is no shift in the concentration gradient, and fluid does not enter or exit the vessels by the force of osmotic pressure. Hypotonic fluids contain less solute and osmosis causes them to shift out of the vessels and into areas of higher solute concentration (the ICF). Hypertonic solutions have the opposite effect and pull fluid from the ICF into the vessels.

In the prehospital setting we only use Isotonic fluids (with the exception of critical care paramedics).

IV Cannulation:

When performing IV cannulation, it is preferred to use veins in the arm, starting with the most distal sites in the hand, and working up from there if the procedure is unsuccessful.

The dorsal metacarpal veins should be attempted first, followed by the cephalic vein. If these are unsuccessful, or for the purpose of large fluid bolus, the accessory cephalic vein at the inner elbow should be used. There is risk with the latter due to potential for accidental arterial or nerve injury.

Potential complications of IV therapy include:

Local complications:

• Infiltration: Accumulation of fluid (blood or IV solution) within the tissue. Presents with white, puffy, hard, cool skin and pain at the site.Treatment is to D/C the IV and choose a new site. Inspect that the catheter is intact and apply cold pack to the site.

• Extravasation: Leakage of IV fluid into the extravascular space at the site. Presents with burning, stinging, redness, and possibly blistering at the site. Treatment: D/C the IV, confirm the catheter is intact, and raise the affected extremity.

• Hematoma: When blood escapes the vessel at the site of catheterization and accumulates in the tissue around the vein. Presents with redness, tenderness and swelling. Treatment: D/C the IV, inspect the catheter is intact, and apply direct pressure over the site.

• Phlebitis: Inflammation of the vascular wall at the site of cannulation. Presents with redness, pain, tenderness, and swelling at the site. Treatment: Use an appropriate sized catheter for the vein.

• Local infection: Result of pathogens entering through the cannulation site in the skin. Presents with redness, swelling, discharge, and foul odour that develops after 3-4 days. Treatment: Prevention using aseptic procedure when initiating IV.

• Venospasm: Constriction of a vein at the site of catheterization, resulting from irritation by certain medications or cold IV fluids. Treatment: Do not administer cold fluids. Apply a warm pack if you notice this.

Systemic complications:

• Air embolism: Introduction of air into the vascular space. Symptoms include: Stroke-like presentations, dyspnea, chest pain, heart failure, decreased LOC. Prevention: Always prime your line.

• Catheter embolism: A piece of the catheter breaks off and enters circulation. Symptoms include: pain/redness/swelling at the site, SOB, hypotension, rapid/weak pulse.

• Speed shock: Sudden adverse reaction when IV medications are administered too rapidly. Symptoms include: flushed face, headache, chest tightness, irregular pulse, decreased LOC. Prevention: Administer IV medications slowly.

• Circulatory overload: Excessive IV fluids are administered. Presents with: crackles on auscultation, dyspnea, tachypnea, decreased SPO2, pink frothy sputum. Prevention: Ensure TKVO rates and bolus volumes are calculated correctly.

• Septicemia: Introduction of bacteria into the systemic circulation. Presents with SIRS/Sepsis. Prevention: Use sterile technique.

• Allergic reaction: Immediate hypersensitivity reaction to a medication. Symptoms are that of moderate-severe allergic reaction. Prevention: Screen your patient appropriately.

Electrolytes: There are several, but we are primarily concerned with K+ and Na+ in the prehospital setting, due to their effects on cardiac conduction.

K+ Potassium:

This is probably the only electrolyte we really need to concern ourselves with in the prehospital environment. K+ works with Na+ to form electrical signals (action potentials) in cells. A Na/K pump exists in cells, and works to keep K+ highest inside the cell and Na+ is highest outside the cell.

When a stimulus is triggered, Na+ channels open, and Na+ rushes into the cell. K+ passively exits the cell through K+ channels in order to balance the shift of Na+. This shift creates an electrical impulse. These impulses are used for things like:

• Muscle contraction

• Hormone release

• Cardiac contraction

Normally, extracellular K+ levels are 3.5-5.0 mEq/L Elevated or severely decreased levels of extracellular K+ can cause major problems in the body.

Hyperkalemia: Renal failure and DKA are 2 primary causes of hyperkalemia. Impaired ability to excrete K+ in the urine leads to buildup in the blood. This impairs the ability of the cells to generate action potential effectively, and presents with:

• Fatigue

• Paresthesia

• Nausea

• Bradycardia

• Hypotension

• ECG changes (Peaked T-waves or Sin waves).

• Respiratory failure/arrest

Hypokalemia: Causes include kidney disease, excessive vomiting or diarrhea, overuse of laxatives, and penicillin. These cause a drop in extracellular K+ that impairs the ability of cells to repolarize, leading to overexcitability. Presents with:

• Weakness

• Fatigue

• Cramping

• Lethal arrhythmias (Torsades)

• Ecg changes (flat or inverted T-waves)

Na+ Sodium:

Na+ is the counter-ion to K+, and its role in action potential was discussed above. The primary role of sodium, outside of electrical conduction, is the control of water balance in the body. Where sodium goes, H2O follow, and as such, the retention and excretion of Na+ are involved in maintaining water balance. Hormones such as aldosterone and controls in the RAAS, act upon Na+. Normal Na+ values in the extracellular fluid are 135-145 mEq/L.

Hypernatremia: A number of causes lead to increased Na+ in the body, including:

• Kidney disease

• Excessive H2O loss through vomiting or diarrhea

• decreased H2O intake

Symptoms include:

• Thirst

• Tachycardia

• Anxiety

• Altered LOA

• Seizures

• Fatigue

Increased extracellular Na+, leads to cellular dehydration due to osmosis.

Hyponatremia: Decreased Na+ in the body can occur due to:

• Liver disease

• CHF

• Burns

Symptoms include:

• Fatigue

• Nausea

• Muscle spasms

• Weakness

If there is a decrease in extracellular Na+, the cells swell due to osmosis.

Medical math:

Dosage determination:

Dose given = Want x Quantity

Have

To determine the concentration of an IV medication, we divide weight by volume (mg/ml).

IV Flow rate:

gtt/min= Volume to be infused x gtt factor

Time in minutes

Next we determine gtt per second:

gtt/sec = gtt/min

60 seconds

Medication Infusion rate:

Rate = Desired dose (mg/ml) x 60 min/hr

Drug concentration (mg/ml)