A large number of medical devices are needed for every medical procedure. Practitioners must pick the right devices to suit every need of their patients.
Here’s a detailed guide to selecting the right IV Cannula for their patient.
What is an IV Cannula?
Also called an IV catheter, this is a flexible, small plastic tube that is used to deliver drugs directly to a patient’s bloodstream.
The components are:
- The needle punctures the skin and enters the vein
- Flexible, plastic cannula tubing delivers the medicines into the bloodstream
- Wings serve as anchors to help with insertion.
- Needle Grip provides support to the needle for better control.
- Luer Connector connects the IV cannula to external devices.
- Luer Lock Plug ensures a secure connection between the other devices and the IV cannula.
- Valve controls the flow of fluids and prevents backflow.
- Flashback chamber gives a visual confirmation of successful entry into the vein by showing a flashback of blood.
- Injection port helps deliver additional medicines or fluid without disturbing the primary IV line.
- Bushing ensures structural integrity.
- IV filters remove small particles, air bubbles and other foreign matter.
Common Uses in Medical Settings
With a wide range of applications, the most common uses of IV cannulas are:
- Administering fluids to dehydrated people
- Transfusions of blood and blood products like plasma
- Obtaining blood samples
- Delivering drugs for chemo
- Providing nutritional support to patients
- Delivering drugs directly into the bloodstream
- Administering radiologic contrast agents for procedures like MRI, CT, etc.
- Testing procedures like allergy tests, and TB screening.
Types of IV Cannulas
The flow of fluids through an IV cannula depends on their sizes and types. Usually, the sizes range from 14-22 gauge. The higher the gauge numbers have smaller cannula sizes.
The different types of IV cannulas are:
- Peripheral IV Cannulas
- Central Venous catheters
- Midline catheters
- Butterfly needles or winged infusion sets
- Draining cannulas
Let’s learn about the various IV cannula types in detail.
Peripheral IV Cannulas
They are thin, flexible tubes which are inserted into a vein for fluid and medicine delivery. Being the most common IV cannulas, they find applications in:
- The ER
- Blood transfusions
- Fluid delivery
- Drawing blood
- Delivering medicines
- Surgical procedures
- Radiology
For insertion into a peripheral vein, a catheter-over-needle device is usually used. For deeper veins, nurses and ER techs go for ultrasonic guidance. These can stay in place for several days, reducing the hassle of reinsertion.
Common sites are:
- Hands
- Inner elbow
- Foot
- Scalp (for infants)
Central Venous Catheters (CVC)
Usually inserted below the collarbone and then guided into the superior vena cava, CVCs are used for larger veins and special purposes. It can also be inserted in the neck, chest, groin or arm.
They find their uses in:
- To administer treatments:
- Chemotherapy drugs
- Blood transfusions
- IV fluids
- Providing nutrition
- Other medications
- Drawing blood samples
- Monitoring blood circulation and checking on heart health
- Cardiac imaging
- Placing transvenous pacemaker
- Temporary use in dialysis
- Treating premature babies
Depending on the patient’s needs, CVCs can stay in place for a very long period of time. This can vary from months to years. However, they are only used for short periods in the case of hemodialysis.
Some CVCs have multiple tubes for simultaneous treatments. This reduces the need for sticking multiple needles into a patient making the process somewhat comfortable.
Midline Catheters
These are used for patients who need fluids or medicines to be directly administered into their bloodstream for 1-2 days. Made up of a soft, thin, non-irritant material, they have to be inserted using ultrasound guidance.
Since they don’t extend past the armpit, they are considered safer than CVCs. However, they cannot be used for routine blood draws or administering medications.
They find uses in:
- Prolonged therapies like cardiology
- Administering antibiotics
- Patients who have difficult venous access
- Administering electrolytes and nutrition
- Being alternatives to CVCs
They are common in medium-term IV therapy which lasts 1-4 weeks.
Butterfly Needles
Some patients have fragile veins which cannot be accessed with a straight needle. For this purpose, butterfly needles (also known as winged infusion sets) for the delivery of fluids or drugs via IV. The most common among them are:
- Infants
- Children
- Elderly
- Any individual with delicate veins
They are used in:
- IV delivery for people with fragile veins
- Difficult venipuncture (infants, children, elderly)
- Blood collection
- Plastic surgery
- Saline infusion
- Irrigation of wounds
- Continuous suction drain
- Accessing difficult veins in the
- Hands
- Foot
- Wrist
- Scalp
Butterfly needles are more flexible than others, thus reaching more of the body’s surface. Also, they are more tolerant of patient movement.
How to Choose an IV Cannula?
Considering the different types of IV cannulas available, various things factor into choosing the right IV cannula. These can be:
- The target patient
- Vein condition
- Type of procedure:
- Surgery
- Medical emergency
- Cancer treatment (oncology)
- Pediatric care
- Geriatric care
- Type of medicine to be administered
- Whether fast or slow infusion is required (flow rate)
Further, the different things to consider while selecting an IV cannula are:
- Gauge of the IV cannula:
- Larger gauges for rapid infusions
- Smaller gauges for delicate veins and slower infusions
- Location of the site
- Avoiding injured peripheral access sites
- Ultrasonic guidance for prolonged therapy
Furthermore, the IV cannula size should not exceed two-thirds of the vein (vessel size). Let’s see how different requirements influence IV cannula selection.
Who is the Patient?
The scope and procedure for a treatment depends upon a patient’s age, physical condition and the stage of the ailment.
Choosing the wrong cannula size can lead to:
- Swelling around the insertion site
- Numbness or tingling
- Leakage of IV fluid
- Inability to get blood return
- Tenderness and discomfort
- Blistering and ulcers
- Risk of injuries and vein damage
Age and Size of the Patient
To minimize discomfort and risk of complications, choosing the right IV cannula size is very important. The age and size of a patient influence the size and condition of their veins. People of either young or advanced age have more delicate veins as compared with adults.
Pediatric Patients
Both infants and newborns are classified as pediatric patients. Care should be taken regarding:
- Using smaller gauges like 24-26 IV cannula gauges for infants
- Slightly larger gauges like 22-24 gauge sizes for toddlers and children
- Ensuring the comfort of the patient
- Easing their anxiety for the procedure
Adult Patients
Widely used IV cannula gauge sizes for adults range from 18-22. However, when choosing the right gauge, the following factors should be accounted for:
- Purpose for inserting an IV cannula
- Condition of the veins
- Flowrate needed
While a 22/20 gauge is usually chosen, for people with difficult venous access, a larger gauge might be preferred.
Geriatric Patients
The following should be considered when selecting an IV cannula for an older patient:
- A 22/24 gauge size due to their smaller vein size.
- Shorter needles for those with superficial veins
- Applying pressure because they have longer bleeding times
- Shallow angles
- Applying cold compress in case of bruising
What is the Vein Condition?
Due to age or medical conditions, a patient can have a narrow vein cross-section, less depth, and a changed vein visibility. Here are some factors to be considered:
- Vein size: A larger IV cannula is used for a larger vein size.
- Vein depth which influences the angle of insertion
- Location of the vein: The cannula size will vary depending upon the vein location (wrist/armpit/femoral artery)
Vein Visibility and Accessibility
This is something which varies from patient to patient. Visible veins have a higher chance of success when it comes to inserting an IV cannula. Further, veins which have a diameter of less than 3mm even after a tourniquet, have difficult IV access. Medical professionals who are inserting the IV should be aware of the catheter-to-vein ratio when inserting an IV cannula.
Is the Vein Fragile or Hardened?
For patients with fragile veins, using a smaller gauge will reduce discomfort and chances of complication. Similarly, seek advice when inserting an IV into hardened veins, since this can require additional therapy.
Considerations About the Procedure
Different medical procedures call for different types of IV cannula requirements:
- Routine IV therapy generally needs a peripheral IV cannula
- Central line cannulas are needed when the medicines have to be inserted into the superior vena cava.
- Placing pacemakers also requires CVCs.
- Surgical procedures can need specialized IV cannulas
- Midline catheters are used for prolonged IV treatments
- For people with fragile veins, butterfly needles are needed for successful IV insertion
Duration
IV cannulas should be chosen keeping the duration of the medical therapy in mind.
- Peripheral IV should be removed within 72 hours
- CVCs can remain in place for months, and even years before they need to be removed. This makes them useful for procedures which require prolonged IV therapy.
- Midline catheters can remain in place for 1-4 weeks before they need to be removed.
Short-Term vs. Long-Term Usage
Period of usage should be taken into consideration when selecting the type of IV cannula to be used. IV cannulas for long-term usage are designed keeping in mind the risks of infection, allergy needs, and the comfort of the patient.
Short-term use of an IV cannula can lead to minor bruising, pain, bleeding, clots, and swelling. However, prolonged usage can cause infections, major blood clot formation, and artery/vein/nerve damage.
It is essential to keep these in mind when choosing the IV cannula for your patient.
Consideration of Medication
IV cannulas have the following effects vis-a-vis delivery of medicines:
- Precise control over the dosage
- Directly administering medicines into the bloodstream
- Faster delivery of medicines via wider gauges
Consider the below when medicines are being delivered via IVs:
- Does the medicine need a quicker or a slower application?
This can affect the size of the gauge to be selected for medicine delivery.
- Is the medicine compatible with the material of the IV?
Some chemicals can react with the plastic of the IV tubing.
- Viscosity of the IV fluid
- The pH level of the IV fluid
Viscosity
For more viscous IV fluids, a higher pressure needs to be maintained by the fluid pump. This will ensure that the flow rate is accurately maintained. Conversely, if the IV fluid has a low viscosity, a lower pressure will be enough for successful IV fluid delivery.
PH level
This is an indication when the liquid is acidic or basic. Some liquids can be corrosive in nature. While IV fluids are neither overly acidic nor basic, they need to be maintained at a particular pH level for their efficacy.
The material that has been used to make the IV cannula should not affect the pH of the IV fluids administered.
Compatibility with Cannula Material
If the cannula material is not compatible with the IV fluid, there remains a chance of the IV fluid getting denatured. Ensure that the IV fluid is compatible with the cannula material for an effective medicine delivery.
Flow Rate Requirements
Not all medications need to be administered at a fast rate. The main reason for drug delivery via IV is to allow precise control over the concentration. For maximum effectiveness, drugs like antibiotics should be administered at a slower rate for maximum efficacy.
High Flow Rate for Rapid Infusion
When drugs need to be absorbed within 1-30 minutes, they need rapid infusion. Generally, painkillers and anesthetics are drugs which need rapid infusion. IV cannulas with a larger cross-section are used for rapid drug infusion.
Low Flow Rate for Maintenance Infusion
Maintenance infusion is needed for drugs like antibiotics and chemotherapy. A low flow rate ensures precise control over drug concentration in the patient’s body. Further, slow infusion rates can control blood loss in case of a hemorrhage.
IV Cannulas in Surgery (Preoperative and Intraoperative Use)
During operations, peripheral IV cannula is the most commonly used. These short-term IVs are used for surgical procedures (like anesthetic administration), radiological imaging and in the ER.
However, getting a transvenous pacemaker will need a central venous catheter.
Fluid Resuscitation and Medication Administration
Quick infusions help with:
- Maintaining hydration during surgery
- Drug delivery
- Providing nutrients for patients
- Rehydrating patients suffering from an injury or illness
Blood Transfusions
Both rapid and controlled blood transfusions can be done for patients who are suffering from:
- Blood loss due to an accident or surgery
- Severe anemia
- Poor blood production
IV Cannulas in Medical Emergencies
The emergency room provides the first response to trauma patients. Using an IV cannula to effectively deliver blood, medication and fluids to patients is an important step in providing medical support to a patient.
Further, IV cannulas can also be used to draw blood samples, without inserting additional needles. Temporary IV lines via peripheral IV cannula are often used as the initial intervention for the patients.
Rapid Infusion and Resuscitation
Peripheral IV cannula can be used to quickly infuse fluids in a patient’s body to resuscitate them.
Trauma and Shock Management
Trauma patients usually come into the ER with high blood loss and shock. Drugs like dopamine and adrenaline, along with saline, can help a patient recover quickly.
Rapid Volume Replacement
Conditions like hypovolemic shock and severe intravascular volume depletion can be treated with rapid volume replacement via IV. This includes:
- Blood transfusion
- Saline solutions for replacing nutrients
IV Cannulas in Oncology
Patients who need chemo get either a 22-gauge peripheral IV cannula or a CVC in their arm. This cannula stays throughout treatment and is removed before discharge.
However, there can be a few complications including:
- Redness, pain and swelling at the injection site
- Leaking of the IV fluids if the catheter is dislodged
- Risks of infection
Chemotherapy Administration
These drugs can be administered via IV in the following ways:
- A cannula in the lower arm or hand
- CVC or central line in the chest
- Peripherally inserted venous catheter
Drugs can be delivered in these lines via:
- IV push through a catheter via a syringe
- An infusion to be delivered over a few hours
- An IV pump to control infusions over a longer period of time
IV Cannulas in Pediatric Care
In pediatric care, IVs in addition to being inserted into the arm of a patient can also be inserted in the scalp of a child. The needles are usually a 22/24 gauge size and inserted at a 10-25° angle. For newborns, they are inserted into the scalp and taped down. The child’s condition determines the type of fluid administered along with its flow rate and amount.
Side effects can include:
- Pain and bleeding
- Blood clots
- Vein/ arterial puncture
- Peripheral nerve palsy
- Tissue death
What are the Different Types of IV Cannula Sizes and Gauges?
Classified based on their diameter and denoted by their gauge numbers, these come in several types. To make sure that people can tell them apart easily, they are further color-coded.
Understanding Cannula Sizes
IV cannula sizes commonly range from 14G to 24G. The lower gauge numbers denote larger cannula sizes. For a faster flow of liquids, like in trauma cases, a larger gauge should be used.
Gauge Number and Diameter
The gauge numbers for IV cannulas are inversely proportional to their diameter. Larger diameters have smaller gauge numbers and vice versa.
Commonly Used Gauges in Various Procedures
The various uses for common IV gauges are:
- 14G is used for rapid fluid transfusion in emergencies
- 16G is generally used for blood transfusion and donation
- 18G is used for administering fluid and medication
- 20G is used as an all-purpose line
- 22G is used in pediatric cases
- 24G is used for people with fragile veins
Choosing the Right Gauge
Selecting the right IV gauge depends on the age, conditions and needs of the patient. Larger IV cannula gauges are used for general patients in trauma care, and administering fluid and medication. Furthermore, a smaller gauge is used for slower infusion rates and fragile patients.
High Flow Needs (14G, 16G)
Trauma care demands quick action by administering drugs and fluids into a patient’s system. To ensure this, larger gauges with wider diameters are used.
Standard Infusion (18G, 20G)
Standard infusion for pre-op, post-op and drug delivery requires gauge sizes which ensures a patient’s comfort. Medium-sized gauges ensure proper IV cannula insertion without leakages and discomfort.
Pediatric and Delicate Veins (22G, 24G)
The selection depends on the age and weight of patients.
- 0-5 months and 3-6 kg: 22/24 IV cannula size for a secure fit with minimal discomfort.
- 6-12 months and 4-9 kg: a 22 size IV cannula.
- 1-3 years and 10-15 kg: toddlers have larger veins which are more accessible making a 22/18 IV cannula ideal for them.
- 4-7 years and 16-20 kg: with growing bodies, these children can go for an 18/22 IV cannula size depending on their veins.
Which Cannula Size Should I Choose?
Take the following into account when picking an IV cannula for your patient:
- Age of the patient
- The need for an IV cannula
- The condition of the patient’s veins
Like all things, even the different sizes of IV gauges have their own pros and cons.
Pros and Cons of Larger Gauzes
Larger gauges ensure rapid fluid infusion and are better for collecting blood samples. However, they also have a high chance of forming blood clots and can be painful.
Pros and Cons of Smaller Gauges
A major pro of smaller gauges is that they cause less trauma, discomfort, and are better for medicines which need a slow infusion rate.
However, these gauges can lead to fluids leaking into the tissues, and vein damage. Further, they are unsuitable for rapid infusions.
Conclusion
IV cannulas are an essential part of delivering medical care to patients. To choose the right IV cannula for the patient, factors like flow rate, compatibility, and patient comfort should be taken into account. The doctors and nurses for a particular patient should properly evaluate these parameters before selecting the IV Cannula for insertion.
