Infused substances
Saline and 5% Glucose solution (Left), Levofloxacin 750mg (Right)
Substances that may be infused intravenously include volume expanders, blood-based products, blood substitutes, medications and nutrition.
Volume expanders
Main article: Volume expander
There are two main types of volume expander; crystalloids and colloids. Crystalloids are aqueous solutions of mineral salts or other water-soluble molecules. Colloids contain larger insoluble molecules, such as gelatin. Blood is a colloid.
Colloids preserve a high colloid osmotic pressure in the blood, while, on the other hand, this parameter is decreased by crystalloids due to hemodilution.[1] There does not appear to be a benefit of using colloids over crystalloids.[1] Crystalloids generally are much cheaper than colloids.[1](blood, albumin, plasma, etc.)
The most commonly used crystalloid fluid is normal saline, a solution of sodium chloride at 0.9% concentration, which is close to the concentration in the blood (isotonic). Lactated Ringer's (also known as Ringer's lactate) and the closely related Ringer's acetate, are mildly hypotonic solutions often used in those who have significant burns.(normal saline, ringer lactate, dextrose, etc.)
Volume expanders may either be isotonic, hypotonic, or hypertonic. Hypotonic fluids are not generally recommended in children due to increased risk of adverse effects.[2]
Advancements in IV Infusions: Polypropylene packaging (instead of LDPE and PVC) crystal clear bottles of polyproplylene (instead of Opaques) unmatched collapsibility (reduces the need of pricking bottle for smooth flow of fluid) impermeable to water vapours and reactive gases to prevent leaching [3]
Blood-based products
Further information: Blood product and Blood transfusion
A blood product (or blood-based product) is any component of blood which is collected from a donor for use in a blood transfusion. Blood transfusions can be life-saving in some situations, such as massive blood loss due to trauma, or can be used to replace blood lost during surgery. Blood transfusions may also be used to treat a severe anaemia or thrombocytopenia caused by a blood disease. People with hemophilia usually need a replacement of clotting factor, which is a small part of whole blood. People with sickle-cell disease may require frequent blood transfusions. Early blood transfusions consisted of whole blood, but modern medical practice commonly uses only components of the blood, such as fresh frozen plasma or cryoprecipitate.
Blood substitutes
Main article: Blood substitute
Blood substitutes (also called artificial blood or blood surrogates) are artificial substances aiming to provide an alternative to blood-based products acquired from donors.
The main blood substitutes used today are volume expanders such as crystalloids and colloids mentioned above. Also, oxygen-carrying substitutes are emerging.
Buffer solutions
Buffer solutions are used to correct acidosis or alkalosis. Lactated Ringer's solution also has some buffering effect. A solution more specifically used for buffering purpose is intravenous sodium bicarbonate.
Other medications
Medications may be mixed into the fluids mentioned above. Certain types of medications can only be given intravenously, such as when there is insufficient uptake by other routes of administration such as enterally. Examples include intravenous immunoglobulin and propofol.
Intravenous access devices[edit]
These can all be used to obtain blood (e.g. for testing), also known as phlebotomy as well as for the administration of medication/fluids.
Hypodermic needle[edit]
The simplest form of intravenous access is by passing a hollow needle through the skin directly into the vein. This needle can be connected directly to a syringe (used either to withdraw blood or deliver its contents into the bloodstream) or may be connected to a length of tubing and thence whichever collection or infusion system is desired.
The most convenient site is often the arm, especially the veins on the back of the hand, or the median cubital vein at the elbow, but any identifiable vein can be used. Often it is necessary to use a tourniquet which restricts the venous drainage of the limb and makes the vein bulge. Once the needle is in place, it is common to draw back slightly on the syringe to aspirate blood, thus verifying that the needle is really in a vein. The tourniquet should be removed before injecting to prevent extravasation of the medication.
Peripheral cannula[edit]
20 gauge peripheral IV in hand
A nurse inserting an 18-gauge IV needle with cannula.
A peripheral cannula is the most common intravenous access method utilized in both hospitals and pre-hospital services. A peripheral IV line (PVC or PIV) consists of a short catheter (a few centimeters long) inserted through the skin into a peripheral vein (any vein not situated in the chest or abdomen). This is usually in the form of a cannula-over-needle device, in which a flexible plastic cannula comes mounted over a metal trocar. Once the tip of the needle and cannula are introduced into the vein via venipuncture, the cannula is advanced inside the vein over the trocar to the appropriate position and secured, the trocar is then withdrawn and discarded. Blood samples may be drawn directly after the initial IV cannula insertion.
Any accessible vein can be used although arm and hand veins are used most commonly, with leg and foot veins used to a much lesser extent. In infants the scalp veins are sometimes used.
The caliber of cannula is commonly indicated in gauge, with 14 being a very large cannula (used in resuscitation settings) and 24-26 the smallest. The most common sizes are 16-gauge (midsize line used for blood donation and transfusion), 18- and 20-gauge (all-purpose line for infusions and blood draws), and 22-gauge (all-purpose pediatric line). 12- and 14-gauge peripheral lines are capable of delivering large volumes of fluid extremely fast accounting for their popularity in emergency medicine. These lines are frequently called "large bores" or "trauma lines".
To make the procedure more tolerable for children medical staff may apply a topical local anaesthetic (such as EMLA or Ametop) to the skin of the chosen venipuncture area about 45 minutes beforehand.
The part of the catheter that remains outside the skin is called the connecting hub; it can be connected to a syringe or an intravenous infusion line, or capped with a heplock or saline lock, a needleless connection filled with a small amount of heparin or saline solution to prevent clotting, between uses of the catheter. Ported cannulae have an injection port on the top that is often used to administer medicine.
In cases of shock, a central venous catheter, PICC (peripherally inserted central catheter), venous cutdown or intraosseous infusion may be necessary.
Complications[edit]
If the cannula is not sited correctly, or the vein is particularly fragile and ruptures, blood may leak into the surrounding tissues, this situation is known as a "tissuing" or a "blown vein". Using this cannula to administer medications causes extravasation of the drug which can lead to edema, causing pain and tissue damage, and even necrosis depending on the medication. The person attempting to obtain the access must find a new access site proximal to the "blown" area to prevent extravasation of medications through the damaged vein. For this reason it is advisable to site the first cannula at the most distal appropriate vein.
If a patient needs frequent venous access, the veins may scar and narrow, making any future access extremely difficult or impossible.
A peripheral IV cannot be left in the vein indefinitely, because of the risk of insertion-site infection leading to phlebitis, cellulitis and sepsis. The US Centers for Disease Control and Prevention updated their guidelines and now advise the cannula need to be replaced every 96 hours.[4] This was based on studies organised to identify causes of Methicillin-resistant Staphylococcus aureus (MRSA) infection in hospitals. In the United Kingdom, the UK Department of health published their finding about risk factors associated with increased MRSA infection, now include intravenous cannula, central venous catheters and urinary catheters as the main factors increasing the risk of spreading antibiotic resistant strain bacteria.[citation needed]
Catheter shearing is a very infrequent complication, but a very real danger. Shearing is when part of the catheter is cut by the sharp bevelled edge of the trochar. The sheared section may completely separate from the main body of the catheter, and become free floating in the blood stream. The large majority of the time it is due to poor technique, but infrequently a poorly manufactured catheter may break from the hub or shear. Infection, and a foreign body embolus are the two threats to the patient.[citation needed]
Central lines[edit]
Main article: Central venous catheter
Central IV lines flow through a catheter with its tip within a large vein, usually the superior vena cava or inferior vena cava, or within the right atrium of the heart. This has several advantages over a peripheral IV:
It can deliver fluids and medications that would be overly irritating to peripheral veins because of their concentration or chemical composition. These include some chemotherapy drugs and total parenteral nutrition.
Medications reach the heart immediately, and are quickly distributed to the rest of the body.
There is room for multiple parallel compartments (lumen) within the catheter, so that multiple medications can be delivered at once even if they would not be chemically compatible within a single tube.
Caregivers can measure central venous pressure and other physiological variables through the line.
Central IV lines carry risks of bleeding, infection, gangrene, thromboembolism and gas embolism (see Risks below). They are often more difficult to insert