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Fluid and electrolyte balance within the body is necessary to maintain health and function in all body systems. The balance is maintained by the intake and output of water and electrolytes and their distribution in the body. Imbalances may result from many factors and are associated with many illnesses. A healthy adult is usually capable of maintaining normal fluid balance, even when a minor fluid loss occurs. This is related to the body's adaptive mechanisms. However, in the situation of profound fluid loss, such as dehydration or hypovolemia the body's adaptive capacities are no longer capable of maintaining fluid or electrolyte balance. These patients require fluid resuscitation. Intravenous therapy is the definitive treatment for patients with fluid loss. Intravenous cannulation is the process of placing a catheter into a peripheral vein for the administration of fluids or medications. This module will discuss the principles involved with obtaining/maintaining intravenous access, as well as the indications, contraindications, and precautions associated with the procedure. Finally, the indications, contraindications, and procedure for insertion of an intraosseous line will be presented.


A person's body composition is over half fluid. The percentage of total body water is between 60% and 80% (Potter & Perry, 1985). The variables that account for the differences in body water are related to age, sex, and body fat. For example, the younger the person the higher the percentage of body water.

 Distribution of Body Fluids

Body fluids are distributed in two distinct compartments, one containing extracellular fluids and the other intracellular fluids.

 Extracellular fluids are the portion of the body fluids comprising the interstitial fluid and blood plasma. Approximately 25% of body water is located outside of the cells with 7.5% found in the intravascular space and 17.5% found in the interstitial space. Interstitial fluid fills the spaces between most of the cells of the body.

 Intracellular fluids are liquids within cell membranes throughout the body, containing dissolved solutes essential to fluid and electrolyte balance and metabolism. Approximately 75% of all the water in the body is found within the cells. Many of the materials in the intracellular fluid compartment are the same as those in the extracellular fluid space. However, the proportion of the substances is different. For example, the proportion of potassium in the intracellular space is greater than in the extracellular compartment.

 Composition of Body Fluids

Electrolytes are located within the water. Electrolytes are composed of positively and negatively charged particles. The major electrolytes for humans are:

Sodium (Na+): It regulates water distribution and is important for the transmission of nervous impulses.

Potassium (K+): It is important for electrical impulse transmission.

Calcium (Ca++): It plays a major role in muscle contraction and is involved with transmission of nervous impulses as well.

Magnesium (Mg++): It is required for several biochemical processes in the body.

Chloride (Cl-): It plays a major role in fluid balance and renal functions.

Bicarbonate (HCO3-): It neutralizes the acids that are found in the body.

Phosphate (HPO4-): It is important as both a buffer and in the regulation of energy received from metabolism.

Movement of Body Fluids

Fluids and electrolytes within the body system are not static, as they shift from compartment to compartment to meet a variety of metabolic needs. Metabolic needs change due to tissue oxygenation or as a response to drug therapy. Body fluid and electrolyte movement is effected through diffusion, osmosis and active transport. Diffusion refers to the movement of solute particles (or concentrate), through a membrane, to an area of lesser concentration of solute particles, resulting in an even distribution of the particles in the fluid. Osmosis refers to the movement of water across a membrane in order to dilute a more concentrated solution (i.e. more solute particles). The result of either the water movement (osmosis) or the solute movement (diffusion) is an attempt to create two solutions with equal concentrations of particles. Active transport is a carrier-mediated process that can move substances against a concentration gradient from areas of lower concentration to areas of higher concentration.

Volume Disturbances

The two basic volume disturbances are fluid volume deficits and fluid volume excesses. Fluid volume excess, or overhydration, is an excess in the extracellular fluid. Fluid volume deficit is a state of water loss that is beyond the normal regulatory system's ability to repair. Intravenous therapy is definitive management of dehydration and shock.


Dehydration is the situation where fluid loss exceeds fluid intake. Patients can lose fluid through the gastrointestinal system (vomiting/diarrhea), increased insensible loss (fever states or hyperventilation), increased sweating, internal losses (third space losses), or plasma losses (burns or open wounds). Often intravenous therapy is required for patients who become dehydrated.


There are many classifications of shock. More than 100 types have been discussed in medical literature. A common classification of shock for use in emergency care is to describe the syndrome based on the initiating cause. Regardless of classification the underlying defect is inadequate tissue perfusion. This means inadequate blood flow to the organs of the body for nutrition and removal of waste products. Treatment remains maintenance of airway, breathing and circulation. These patients will require intravenous therapy.


Universal Precautions

When initiating intravenous therapy, prehospital care providers must employ universal precaution techniques. All blood and body substances should be regarded as potentially infected. Gloves must always be worn whenever working with intravenous equipment. Particular attention must be given to proper handling and disposal of needles and sharp instruments. Needle-stick injuries can largely be avoided by not recapping needles.

Indications and Contraindications for Vascular Access

Intravenous therapy is an important adjunct in the management of the seriously ill or injured patients. The indications and contraindications of its use are:


            To administer fluids / medications (or as a TKO line in potentially unstable patients who may require fluids/medications)

            To obtain blood specimens for laboratory analysis

            To insert invasive monitoring instruments (In Hospital)


            Cannulation of a particular site is contraindicated in sclerotic and burned extremities.

Attempts at intravenous therapy should not significantly delay transporting critically ill or injured patients to the hospital.


Types of Intravenous Cannulas

The most common types of intravenous catheters are:

            Catheter over the Needle (Most common in prehospital care);

            Butterfly needle (Only recommended for drawing blood samples);

            Through the needle catheters; and

            Indwelling plastic catheters inserted over a guidewire.

 Sites for Insertion

Intravenous cannulas can be inserted in either central or peripheral veins. EMT-A’s are allowed to insert intravenous cannulas into peripheral veins. In Alberta, only EMT-P’s can insert IV’s into the external jugular vein. Potential insertion sites will include:

            The veins of the hand;

            The veins of the arm (antecubital, radial, ulnar, cephalic,...); and

            The external jugular vein.


Source: Sanders, M. (1995). Mosby's Paramedic textbook. Pg. 326

 Colloids and Crystalloids

There are two major categories of intravenous fluids: crystalloids and colloids.

 Dissolving crystals such as salts and sugars in water creates crystalloids. They contain no proteins or other high molecular weight solutes. Crystalloids remain in the intravascular space for only a short period before diffusing across the capillary wall into the tissue. Because of this action, it is necessary to administer 3 liters of crystalloid solution for every 1 liter of blood loss. Normal saline (NS) and lactated ringers (RL) are examples of crystalloids.

 Colloids contain large molecules such as protein that do not readily pass through the capillary membrane. Therefore, colloids remain in the intravascular space for extended periods. These large molecules also increase the osmotic pressure in the intravascular space thereby causing fluid to move from the interstitial and intracellular space to the intravascular space. For this reason, colloids are often referred to as volume expanders. Colloids are expensive, have short half-lives, and require refrigeration. For these reasons are not commonly used in the prehospital setting.

Intravenous Solutions

It is important to understand what type of intravenous solution is being used. Hypertonic solutions have higher osmotic pressure than that of the body cells (i.e. D5W with 0.45% NS and D5W with 0.9% NS). Hypotonic solutions have a lower osmotic pressure than that of the body cells (i.e. distilled water and 0.45% NS). Isotonic solutions have an osmotic pressure equal to that of the cells of the body.

In the prehospital care setting, there are three common types of intravenous fluid.

Normal Saline

Normal saline contains sodium and chloride ions in water and it is isotonic with extracellular fluid. Saline is given to replace fluids in the hypovolemic or dehydrated patient. A small amount of saline in a special adjunct can be used to keep the vein open for medication administration (lock).

5% Dextrose in Water (D5W)

D5W is hypotonic. It has an initial effect of increasing the circulating volume. However, the glucose molecules cross the membranes of the body easily, taking water with them, and the net effect is almost negligible on circulatory volume.

Lactated Ringers

Lactated Ringer’s solution is an isotonic electrolyte solution. It contains sodium, chloride, potassium, calcium and lactate in water. It is also used for fluid replacement. However, in prehospital care, there has been no obvious benefit from the administration of lactated ringer’s over normal saline in the short term. If large volumes of fluid replacement are required (i.e. 4 litres or more), the prehospital care provider should switch to Lactated Ringers after the first 4 litres of saline are given. This prevents causing a state of hyperchloremic acidosis, which results from the administration of large amounts of saline.

The following table provides a description of the different intravenous solutions.






5% Dextrose in water (D5W)


Hypotonic sugar solution

            To maintain water balance and supply calories necessary for cell metabolism


            Is inexpensive and readily



            Causes red cell clumping (cannot be given with blood).

            Incompatible with some medications

            May cause water intoxication, low sodium, or

            high glucose

            Not the solution of choice in shock

            Use only to establish an emergency IV line for drug administration

0.9% Sodium chloride (NS)



            Initial fluid and electrolyte replacement in all types of hypovolemia

            Cardiac arrest

            Is inexpensive and readily available

            May be used as an initial plasma expander while blood is typed and matched

            May cause diuresis, high sodium and acid-base imbalance

            Use cautiously in patients with CHF or renal dysfunction

            Monitor for S&S of fluid overload.

Lactated Ringer’s



            Initial fluid replacement in all types of hypovolemia

            Cardiac arrest

            Is inexpensive and readily available

            Rarely causes adverse reactions

            May lead to volume overload, or CHF

            Use in caution in patients with liver disease or anorexia

            May induce low sodium with multiple infusions


Steps Involved for Insertion of the Intravenous Catheter

To perform intravenous cannulation the EMT-A or EMT-P must do the following:

            Identify that the patient requires an intravenous line, the proposed purpose of obtaining venous access, and select the appropriately size I.V. cathalon;

            Gather the equipment to perform the entire procedure (penrose drain/tourniquet, alcohol swab, iodophore swab, tape, gauze, IV solution, IV tubing/saline lock, and a surgical dressing);

            Verify correct solution and prime intravenous tubing;

            Apply the tourniquet and cleanse the site appropriately (iodophore first, followed by alcohol) after 30 seconds;

            Using sterile technique, insert the intravenous needle (bevel side up) until the vein is punctured, and advance the needle a few millimetres after "flashback" is obtained;

            Advance the intravenous catheter while leaving the needle in a stationary position;

            Release the tourniquet from the patient’s arm;

            Connect the intravenous tubing, or saline lock, to the intravenous catheter and set the flow rate;

            Secure the intravenous catheter with tape and or a surgical dressing; and
Document the procedure completely.

Source: Shade et al (1997). Mosby's EMT intermediate textbook. Pg 296


Calculations for Fluid Flow Rates

The fluid rate should be adjusted as ordered by medical control. The EMT-A or EMT-P must know the volume to be infused, the period of time over which the fluid is to be infused, and the number of drops per millimeter the infusion set delivers. The flow rate can then be calculated using the following formula:

Macrodrip = 10 drops/ml and Microdrip = 60 drops/ml

**The macrodrip set is most commonly 10 drops/ml, however 15 or 20 drops/ml may also be used. Always refer to the drip chamber as it indicates the drops/ml.

Drops/min = Volume to be infused x Drops/ml of infusion set

                 Total time of infusion in minutes

For example, the order reads: infuse 120 mls over 1 hour (using a 10 drops/ml set)

Drops/min = 120 mls x 10drops/ml


                                                    = 20 drops/minute

Receiving Patients with Established Intravenous Lines

When completing a patient transfer, patients may have an established intravenous. Therefore, it is important to assess the intravenous line for patency, correct choice of sites, size of cannula, as well as for any of the potential complications of intravenous therapy. If needed, the intravenous should be restarted prior to departing from the sending hospital.


Several complications may arise as a result of intravenous therapy.







            infection of the subcutaneous tissue


            creation of a blood clot


            infection of the vein


            generalized systemic infection

Pulmonary thromboembolism

            creation of a clot that lodges in the lungs

Air embolism

            allowing an air bubble to enter the circulatory system

Catheter fragment embolism

            breaking the continuity of the intravenous catheter and allowing the fragments to enter the circulatory system.

Local infiltration

            infusion of intravenous fluid into the tissues of the skin.

Circulatory overload

            administration of an excessive amount of fluid into the circulatory system that may cause heart failure and pulmonary edema.



 Intravenous access may be obtained for the purposes of administering small amounts of medication, or simply as a precaution, in case a patient's condition changes, and requires the administration of fluids or medications. Traditionally, a 5% dextrose in water solution was initiated, at a flow rate of 10-50 ml/hr (TKVO Rate). However, saline locks (Jelco Caps or Deseret PRN Adapter) are now used most commonly on "To Keep Vein Open" intravenous lines.

Intermittent Vascular Access Device Procedure - Which requires priming

( i.e. Jelco Lock)

             Prepare a syringe with 3 mls of sterile saline.

            Prime the saline cap, using the syringe / needle combination, by injecting approximately 2 ml's of normal saline. Leave the syringe and needle inserted into the Jelco Cap.

            Insert the intravenous cannula as per the usual procedure.

            Apply the saline cap to the cannula hub (syringe/needle attached).

            Flush with 1 cc of normal saline while with drawing the needle.

            Remove the syringe/needle from the saline cap.

            Secure with tape

Intermittent Vascular Access Device Procedure – Which does not require priming

(i.e. Deseret PRN Adapter )

            Prepare a syringe with 3 ml's of sterile saline.

Insert the intravenous catheter as per the usual procedure.

Connect the intermittent vascular access device to the hub of the intravenous catheter.

Wipe the access hub with an alcohol swab.

Insert the syringe needle through the cap. Inject 1-2 mls of saline while withdrawing the needle.

Secure with tape.

 Vascular access remains an early priority of Advanced Cardiac Life Support, Basic Trauma Life Support, and Pediatric Advanced Life Support. The general principles of vascular access are the same regardless of the patient's age, or illness / injury. Specific concerns regarding vascular access for trauma patients and pediatric patients will be discussed in the following sections.

 Vascular Access for the Trauma Patient

 When to Start the Intravenous

The textbook, Basic Trauma Life Support (1997, pg. 122) recommends starting the intravenous during transportation of a trauma patient. If necessary, the driver can slow down or stop momentarily for the intravenous to be inserted. The exception to this guideline is in the case of prolonged extrication times. If there will be a significant delay in freeing an entrapped patient, the intravenous can be started while the patient is entrapped.

What Fluid to Give

In prehospital care, either lactated ringers or normal saline can be used for volume replacement. If large volumes of Normal Saline are infused, a state of hyperchloremic acidosis may be induced. Most ambulance services are only carrying Normal Saline as Lactated Ringer's does not offer any clear advantage in the prehospital setting. In the future, oxygen-carrying compounds such as perflurocarbon, and stroma-free hemoglobin may be administered in hypovolemic shock, as these fluids are capable of oxygen transport.

How Much Volume to Give

For volume replacement in the trauma patient, the replacement ratio of intravenous fluid to blood lost is 3:1. In other words, for every 1 cc of blood lost, 3 cc's must be administered. The exception to this rule is when blood is administered. Only 1 cc needs to be administered for every 1 cc of blood lost. Furthermore, blood pressure should only be raised to 90-100 mm hg systolic with IV fluid replacement. There is current research to suggest that even lower systolic blood pressures are preferred (Basic Trauma Life Support, 1998 pg. 120). Always refer to local medical direction.

Other Recommendations for the Trauma Patient

The preferred site for intravenous insertion in the trauma patient is the antecubital fossa. Secondarily, the external jugular vein may be used, if accessible. Finally, the largest available peripheral vein is used. Short, large diameter I.V. cannulas are recommended, as well as short I.V. tubing. Pressure infusers, and "Y" tubing (blood tubing) are also recommended. If possible, intravenous fluids should also be warmed. This is of greater importance when infusing large volumes.


Pediatric patients can have intravenous lines established in the hands or arms. An appropriate I.V. catheter should be chosen which matches the size of the vein. Typical pediatric I.V. needles range in size from 20-24 Ga. Although scalp veins can be cannulated in pediatric patients, they are not recommended for the resuscitation phase of treatment because of their small size, and poor location.

Flow Rates

The flow rate to be used in pediatric patients varies with the patient's condition. For volume replacement, the treatment sequence is:

ASSESS - 20 ml/kg - REASSESS

For patients who only require "To Keep Vein Open" flow rates, a minidrip (60 drop) administration set, buretrol, infusion pump, or an intermittent vascular access cap should be used.

Priorities in Pediatric Vascular Access – Overview

Excess time is often wasted in trying to establish peripheral intravenous lines in pediatric patients. The current recommendation from the Textbook of Pediatric Advanced Life Support (1997), is to spend no more than 90 seconds, making up to three attempts at peripheral intravenous access (pg. 5-2). If unsuccessful, an attempt at intraosseous cannulation should be made, if the child is under 6 years of age (Ped ALS 1997, pg. 5-2).



Introduction and Background

The technique of intraosseous infusion was first demonstrated in 1922 and gained widespread use in the 1940's. However, as plastic intravenous cannulas became perfected, peripheral venous access became the preferred route for vascular access. Intraosseous was rediscovered in the 1980’s and studies have confirmed that it is a safe and effective route to infuse medications, fluid and blood. Intraosseous infusions can be used for giving medications in both adults and children, but because the flow is not as rapid as peripheral venous infusions, it can not be used for rapid volume replacement in adults.

Anatomy of the Lower Leg

The two most commonly used bones for intraosseous infusion are the femur and the tibia. They are both considered "long bones" and as such can be divided into three sections:

            Diaphysis: the portion of a long bone between the ends or extremities, which are usually articular (pertaining to a joint), and wider than the shaft of the bone, enclosing the medullary cavity.

Epiphysis: the end portion of the long bone, usually wider than the shaft, covered by a thin layer of compact bone. Articular cartilage covers the epiphysis to provide smooth surfaces for movement in the joints. During the period of growth, epiphyses are separated from the main portion of the bone by cartilage. The junction between the epiphysis and diaphysis is called the epiphyseal or growth plate.

Metaphysis: the wider part at the end of the shaft of a long bone, adjacent to the epiphyseal plate.

 Insertion Sites

Three sites are suggested for the puncture. The most commonly used site is the anteromedial surface of the tibia, approximately 1 to 3 cm below the tibial tuberosity, since the marrow cavity is large and the potential for injury to adjacent tissues is minimal (Ped ALS, 1997). The distal tibia and distal femur can also be accessed (Pons & Cason, 1997).


The intraosseous route is indicated for any urgent clinical situation in a patient requiring vascular access for the administration of fluids, or medications, when other means of vascular access may be either impossible or delayed (ie. longer than 90 seconds).

The Textbook of Pediatric Advanced Life Support (1997, pg. 2-7) defines three urgent, clinical situations:

            Respiratory Failure


        Cardiopulmonary Failure

The current recommendation is that the technique only be used in children under the age of six. Intraosseous is for temporary use only. Once the child’s condition has stabilized another form of intravenous therapy should be initiated.


All contraindications are relative, as this technique will only be used in critically ill or injured children. Furthermore, most contraindications refer to the site chosen, rather than the technique itself. The contraindications are:

            Infection in close proximity to the insertion site;

            Loss of venous integrity proximal to the insertion site;

            Fracture of the bone to be used for the insertion;

            Prior insertion (within 4 weeks), in close proximity to or proximal to the insertion site;

            Myelofibrotic conditions;

            Osteogenesis imperfecta;

            Severe Osteoporosis; and



What Can and What Can Not Be Infused

The following substances can be infused:


            Blood Products

            Total Parenteral Nutrition

            Virtually All Medications (Including bicarbonate, and 50% Dextrose)

The only substances that cannot be infused are known bone marrow toxins.

Consult the base station physician if uncertain.

Flow Rates

            Flow rates of 10 cc's per minute are possible using gravity

            Flow rates of 40 cc's per minute are possible using a pressure infuser with up to 300 mm of Hg pressure generated


The following complications may occur when using intraosseous infusions:


            Epiphyseal injuries

            Periosteal, or subcutaneous hematomas


            Extravasation of fluid and / or medications

            Inadvertent perforation of both corticles

            Soft tissue injury

Technique of Intraosseous Cannulation

            Locate the site. The tibial tuberosity is identified by palpation, and the site of intraosseous cannulation is approximately 1 to 3 cm below this on the medial surface of the tibia.

            Cleanse the skin.

            Grasp the thigh and knee above and lateral to the insertion site with the palm of the nondominant hand. Wrap the fingers and thumb around the knee to stabilize the proximal tibia. Do not allow any portion of the hand to rest behind the insertion site. The leg should be supported on a firm surface.

            Palpate the landmarks and again identify the flat surface of the tibia just below and medial to the tibial tuberosity.

            Insert the needle through the skin, advance the needle through the bony cortex of the proximal tibia, directing the needle perpendicular (90° ) to the long bone or slightly toward the toes to avoid the epiphysial plate, using a gentle but firm twisting or drilling action.

            Stop advancing when a sudden decrease in resistance is felt. This indicates entrance into the bone marrow cavity.

            Unscrew the cap and remove the stylet from the needle.

            Stabilize the needle and slowly inject 10mls of normal saline. Check for increased resistance, increased circumference of the soft tissue, or increased firmness of the tissue.

            If the test injection was successful, attach the infusion set and secure the needle and tubing with tape and a bulky dressing.

            If the test was injection unsuccessful, reinsert the stylet and advance 2-3 more mm and test again. If still unsuccessful, remove and attempt on other leg. (Pediatric Advanced Life Support 1997, pg.5-6).

Insertion is successful and the needle is clearly in the marrow if: a sudden decrease in resistance occurs as the needle passes through the bony cortex into the marrow, the needle can remain upright with no support, marrow can be aspirated (not consistently achieved), and fluid flows freely through the needle without signs of infiltration.

Source: Pons & Cason. (1997). Paramedic Field Care. Pg 811



A recent study completed by Halm and Yamamoto (1998) compared the Jamshidi and Cook needles for ease of intraosseous needle placement. They determined that insertion time was significantly shorter using the Jamshidi needle (25.5 seconds verses 56.2 seconds). The difficulty of insertion was also significantly less using the Jamshidi needle (3.0 verses 7.1 on a 10-cm visual analog scale). As well, the Jamshidi needle is less costly than the Cook needle.



Establishment of a reliable vascular access is a crucial step in adult and pediatric care. If vascular access is accomplished within the first few minutes of a resuscitation, infusion of medications and fluids is possible and a successful resuscitation is more likely. Intravenous and intraosseous techniques remain the preferred methods for medication administration and are mandatory for the infusion of fluids, especially when cardiac compromise results from noncardiac causes, such as trauma or sepsis.

 The recommended intravenous solution is normal saline in the prehospital setting. Several ambulance services now have protocols for the administration of blood and blood products for certified paramedics.

 The preferred site for intravenous cannulation in the prehospital care setting is the antecubital fossa. In noncritical patients the back of the hand and arms may be considered as well.

 Although intravenous cannulation is beneficial in a wide variety of situations, placement of an intravenous should never delay transporting the seriously ill or critically injured patient to the hospital. The exception would be the situation where the prehospital care provider can deliver the definitive treatment for the patient's condition.



1.     Take your time when choosing the right vein.

2.     Take your time performing the venipuncture.

3.     Think: Purpose > Appropriate access > Appropriate catheter size > Appropriate site.

4.     Apply tourniquet 6 to 8 inches above the selected puncture site.

5.     No veins: Let arm hang down for a while - the "praying position" for puncture.

6.     No veins: Apply warm towels over several minutes.

7.     Bad filling: "Milk" the vein…gently stroke from distal to proximal.

8.     No veins: Use double tourniquets, one high on the arm, one 4 inches from the puncture site.

9.     For low blood pressure: Use a BP cuff, not a tourniquet.

10.  For well-filled but fragile veins: Try puncture without using a tourniquet.

11.  Patients with hypovolemia: Use larger veins as small veins collapse quicker.

12.  When a patient is grossly edematous, apply a tourniquet for a few minutes to create an "indentation"; After removal a vein can usually be seen in the well of the indentation.

13.  Apply warm towels on the cannulated arm if an irritating medicine is being infused.



1.     Use the top approach. This will give you more control.

2.     Hold angiocath with bevel facing up at a 10 to 20 degree angle, on top of the skin over the chosen vein. 

3.     Pull skin taut ( but not so taut that you flatten the vein).  If cannulating on the hand, have patient loosely close the hand.

4.     Using a continuous, slow motion, advance the angiocath through the skin. Round out the angio slightly while under the skin.

5.     With a continuing slow motion, advance the cannula a minimal amount to pass it through the wall of the vein ( you should now see the beginning of a "flash"), you should feel a "pop" as the needle penetrates the vein wall ( DO NOT CANNULATE THROUGH TO THE OPPOSITE SIDE!!). Lower the angle of the cannula as you continue to advance the angio into the center of the vein. The "flash" will continue.  Now loosen the tourniquet.

6.     Once in the center of the vein, slide the angio further into the vein and off of the needle.  Pull the needle back a bit. Flash will now be observed in the cannula, which remains in the vein.

7.     You should now be able to easily advance the cannula forward into the vein. Continue to watch for "flash". If the cannula gets hung up on a valve, you might flush it up the vein with NS. The entire process should be done with one slow, continuous motion from start to finish.

8.     Loosen the tourniquet for sure at this point, straighten your back confidently, and SMILE.



Bifurcated veins are recognized by an inverted "V" shape.  These veins are less likely to roll; however, the vein should be accessed below the bifurcation for the highest chance of success.

Accessing large, "ropy" veins, often found in the elderly, should be done without the use of a tourniquet because the veins are less sound and tend to rupture easily.

The use of hand veins in the elderly is not recommended because they too tend to rupture easily.

Basilic veins located immediately below the elbow, particularly those in male patients, are large and attractive for venipuncture; however the accessing is difficult because they tend to roll easily and require significant attempts to stabilize them.



An improper tourniquet placement.

Failure to release the tourniquet once angiocath is in the vein.

With a tentative start and stop approach, the vein disappears.

Failure to recognize when a cannula has gone through the vein, resulting in a hematoma.

Stopping too soon after insertion can cause a hematoma or a disappearing vein.

Inserting a cannula too deep and missing the vein is generally a result of too steep an angle of approach for the depth of the vein.

Failure to penetrate the vein is generally a result of a dull angiocath or sclerotic vein.

Getting stuck in the wall of the vein is usually the result of not advancing the angiocath far enough into the center of the vein. Signs of this are a positive flash with an inability to advance the cannula with ease.

A ruptured vein on insertion is usually a result of the use of too large an angiocath for the size of vein.

Pain during insertion can be the result of touching a nerve ending.  Start over at a new location and document.  If the cannula is left in place, this nerve will continue to trigger and will cause a painful IV for the patient.

Improper taping of the IV tubing across the cannula and the underlying vein will later cause pain during infusion. Tape the tubing away from the cannula site.


DO NOT PROBE FOR THE VEIN UNDER THE SKIN!  Very seldom will an incorrectly placed angiocath end up in the proper place.  This action will cause damage to the vein and surrounding tissues.

 NEVER ADVANCE THE NEEDLE BACK THROUGH THE CANNULA!! This may carve parts of the cannula free and allow them to enter the venous system. (Bad,bad,bad.)


NOTE:  As a part of professional courtesy, never cannulate your instructors Medial nerve.


Crude analogies aside, "size does matter" when it comes to choosing your IV catheters. It comes down to common sense.  You choose a size appropriate for the situation and for the size of the vein.  Larger bore Ivs (18, 16, 14) are appropriate for rapid infusion of fluids and/or blood products but you need a big vein to get them in (and they hurt more).  Additionally, putting a cannula into a vein that is too small can cause damage to the vein and put the patient at risk for phlebitis (because blood cannot flow around the catheter).

 Smaller bore Ivs (20, 22, 24) are adequate as a simple route for medication, and they are less painful.  Blood can be given through a 20 or even a 22 gauge catheter, but it will be slower than if given through large bore catheters.


A Guide for Catheter Gauges

(Adapted from Loeb, 1992)







·         Large adolescents or adults

·         Trauma

·         Rapid infusion of fluids and/or blood and blood products

·         Very painful insertion

·         Requires large vein




·         Adolescents and adults

·         Trauma

·         Infusion of large volume of fluids

·         Infusion of blood or blood products

·         Painful insertion

·         Requires large vein




·         Older children, adolescents & adults

·         Fluid resuscitation

·         Infusion of blood, blood components & viscous solutions

·         Obstetric patients

·         Mildly painful insertion

·         Requires decent sized vein




·         Children, adolescents & adults

·         Suitable for most infusions, TKVO lines

·         Infusion of blood or blood components (Vollote,1989)

·         Commonly used

·         Slower to infuse large amounts of fluid



  • Infants, toddlers, children, adolescents & adults (especially the aged and emaciated)
  • Suitable for most infusions
  • Easier to insert in small, thin, fragile veins
  • Use with slower flow rates
  • Difficult to insert into tough skin


  • Neonates, infants, toddlers
  • Flow rate would be very slow


(Loeb, 1992) 





Located on dorsum of hand; formed by union of digital veins

Easily accessible

Adapter lies flat on back of hand

In adult or large child, bones of hand act as a splint

Usually first choice for cannulation


Wrist mobility decreased unless a short cannula is used

Insertion painful because of large number of nerve endings

Site becomes phlebitic more easily

May be contraindicated with an aged patient as thin skin & loss of connective tissue may predispose to extravasation of blood (Villote, 1989)


Runs along ulnar aspect of forearm & upper arm.


Straight strong vein suitable for large gauge cannula


Uncomfortable position for patient during insertion

Painful area to penetrate skin

Vein tends to roll on insertion


Runs along radial aspect of forearm & upper arm

Large vein readily accepts large gauge cannula

Does not impair mobility

Decreases elbow joint mobility

Vein tends to roll during insertion



Runs along radius as a continuation of metacarpal veins of the thumb

Large vein readily accepts large gauge cannula

Does not impair mobility

Does not require an armboard in older child or adult

Sometimes difficult to position adapter flush with skin

With adapter placed at bend of wrist, movement can cause discomfort or kinking of tubing


Located in antecubital fossa (median cephalic, located on radial side; median basilic, on ulnar side; median cubital, in front of elbow joint)


Often palpable or visible in children when other veins will not dilate

May be used for peripheral IV therapy in an emergency or as a last resort


Difficult to immobilize joint

Median cephalic vein crosses in front of brachial artery, increasing the risk of arterial puncture and intra-arterial infusion of medication, resulting in permanent damage

Veins may be small & scarred if blood has been drawn frequently


Arises from palm and runs along ulnar aspect of forearm


A last resort when no other sites available

Many nerve endings in area may cause painful venipuncture

Infiltration occurs easily, increasing risk of nerve damage


Run along dorsal & lateral portions of fingers (digits)


Last resort for fluid administration or for non-irritating medications


Finger is splinted with a tongue depressor, limiting mobility

Uncomfortable for patient

Infiltration occurs very easily

Cannot be used if metacarpal veins have already been used