In the event of a serious loss of fluid, or electrolyte and fluid imbalances, fluid substitution is the first thing to do. If this is not possible orally, fluid must be administered parenterally, most often as an iv. infusion. Infusion thera- py provides a possibility for the administration of a major volume of fluid, electrolytes and drug into the circulatory
system. The rate and duration of fluid administration can be regulated. If the concentration of a drug exceeds the physiological range, it can be administered in an infu- sion. Thus, a longer period of administration and a con- stant concentration in the blood can be achieved. Infusion therapy is proposed before admission in the following cases:
acute myocardial infarction, left heart failure, pulmonary embolism,
stroke, hypertensive crisis,
status asthmaticus,
acute bleeding,
shock, allergic reaction, burns, an unconscious state,
acute artery blockade in the extremities,
acute metabolic comas (hyperglycemia), Addison, or a hyper- or hypothyroid crisis.
Infusions are usually delivered into superficial veins (in the forearm, or the dorsum of the hand/foot); most of- ten, it is delivered into the cubital vein. If a vein cannot be reached by punctures, it must be exposed surgically. In a long-term continuous infusion, etc, a catheter may be inserted into the superior vena cava after the exposure and dissection of the jugular veins. This catheter can al- so be used to measure the central venous pressure. The iv. infusion therapy involves many risks, and should be per- formed strictly in accordance with the rules of asepsis. Infusions
Devices for iv. infusion
A sterile plastic infusion bag (infusion glass bottle), a sterile iv. administration set, hypodermic needles (“but- terfly” and braunule), disinfecting solution, gauze, tapes, an infusion stand, and sterile disposable gloves.
The infusion set
The sterile set is wrapped in a double package (plastic and paper). The package should be opened only just before use. Sets of damaged packages must not be used (sterility!). Parts of the iv. administration set
A spike, a drip chamber (flexible), and long tubing with the flow regulator (a plastic roller clamp for control of the flow rate):
The protective covering is removed from the port of the infusion bag and from the spike of the set, and the spike is
inserted into the bag. The bag is hung on the stand; the low- er part of the drip chamber is squeezed to set the fluid lev- el, until the drip chamber is approximately one-third full. If the level of the fluid is too low, the chamber is squeezed to remove air to the bag. If the chamber is overfilled, the bag is lowered to below the level of the drip chamber and some fluid is squeezed back into the bag. The flow regula- tor is opened and the fluid is allowed to flow into the tub- ing (removing air). The end of the tubing is connected to the iv. catheter in the patient’s vein, and the flow rate is ad- justed as desired. After a loop has been made in the tubing, the catheter is secured to the skin with strips of tape. Dur- ing infusion, the patient, the administration set and the flow of fluid must be controlled continuously.
Dosage of infusion
There are two types of drip chambers: microdrip (60
drops/mℓ; for the administration of medication or fluid delivery in pediatrics), and macrodrip (10–15 drops/mℓ; for routine/rapid fluid delivery or keeping the vein open).
The volume of infusion fluid/drugs should be calculat-
ed. A formula to calculate drops: volume of infusion flu- id (mℓ) × drop factor (drops/mℓ) / time to infuse (min) = drops/min. As an example, an infusion of 1000 mℓ of saline during 12 h with a microdrip chamber should be delivered at a rate of 1000 × 60/720=83 drops/min.
The amount of the infusion depends on different fac- tors (the body surface area, the physical condition, the age and the osmolarity of the infusion fluid).
At the end of the infusion, the tubing is clamped, the
tapes are removed, followed by the needle or braunule catheter, and sterile gauze is placed on the site of the puncture.
Other iv. administration sets
1. Set with hydrophobic bacteria filter
2. Dual drip infusion iv. set (with a micro- and a macr- odrip chamber)
Risks and complications of iv. infusion therapy
In peripheral iv. therapy, the position of the vein
puncture should be changed after 48 or 72 h, and the catheters must be changed after 24 h.
Hematoma: during the vein puncture, the wall of the
vessel may be damaged (therapy: compression).
Inflammation-thrombosis (during long-term infu- sions or the administration of acidic or alkaline so- lutions, or infusions of high osmolarity).
The endothelium of the vessel wall may be damaged
by the tip of the needle (compress).
Air embolism (remove air!).
Fever (rules of asepsis!).
Circulatory insufficiency (in heart or renal failure
during infusion at too high a rate!). Variations of iv. infusion
Infusion of two different solutions. Two infusion sets are used. The tubes are connected with a Y tubing below the drip chambers.
Medication administration with an iv. infusion. This is delivered slowly together with the infusion fluid to at- tain a constant drug level in the blood.