Pre-prepared infusion fluids with additives such as potassium chloride should be used whenever pos- sible. This reduces the risk of extrinsic contamination, which can occur when adding drugs to infusion fluids (Weinstein 2007). Only one addition should be made to each bag of fluid after the compatibility has been ascertained as more additions can increase the risk of incompatibility occurring, leading to, for example, precipitation (Weinstein 2007; Whittington 2008). Drugs should never be added to blood, blood products, i.e. plasma or platelet concentrate mannitol solutions, sodium bicarbonate solution, and so on. Only specially prepared additives should be used with fat emulsions or amino acid prepara- tions (Downie et al. 2003).
Potential incompatibility between the drug and diluents, contributing factors such as drug brand, pH, concentration and the effect of light or temperature, and the recommended duration of infusion must be checked prior to preparation. If insufficient information is available, a reference book (e.g. the British National Formulary [BNF] 2011) or the product data sheet must be consulted (National Patient Safety Association [NPSA] 2007; Whittington 2008).
The additive and fluid must be mixed well to prevent the layering effect that can occur with some drugs and to avoid the risk of administering a bolus injection of the drug (Whittington 2008). Following any additions to the infusion fluid, the container must be inverted a number of times to ensure mixing before the fluid is hung on the infusion stand (NPSA 2007). The infusion container should be labelled clearly after the addition has been made. Infusion bags should not be left hanging for longer than 24 hours. In the case of blood and blood products, this is reduced to 5 hours (McClelland 2007;
RCN 2010).
Inspection of fluids, drugs, equipment and their packaging must be undertaken to detect any points at which contamination may have occurred during manufacture and/or transport. This intrinsic contamination may be detected as cloudiness, discoloration or the presence of particles (Weinstein 2007; RCN 2010; BNF 2011). If the nurse is unsure about any aspect of the preparation and/or administration of a drug, he or she should not proceed but should consult a senior member of
31
staff (Nursing and Midwifery Council 2008). Constant monitoring of the infusion fluid mixture for cloudiness or the presence of particles should occur, as should checking the patient’s condition and intravenous site for patency, extravasation or infiltration (Downie et al. 2003; Weinstein 2007; Whit- tington 2008).
Methods of administering intravenous drugs
There are three methods of administering intravenous drugs: continuous infusion, intermittent infusion and direct intermittent injection.
Figure 3.5 (a) Types of peripherally inserted central catheter. (b) Non-tunnelled multilumen central venous catheter. (c) Anatomical positioning of a tunnelled catheter. (d) Implantable ports. Reproduced from Dougherty, L. & Lister, S. (2011) The Royal Marsden Hospital Manual of Clinical Nursing Procedures with kind permission from Wiley Blackwell.
(a)
Superior vena cava Dacron cuff
Exit site of catheter Skin
tunnel Subclavian vein
Entry of catheter
(i)
(c) (ii) (b)
(d)
32
Continuous infusion
This is defined as the intravenous delivery of a medication or fluid at a constant rate over a prescribed time period, ranging from several hours to several days, to achieve a controlled therapeutic response (Whittington 2008; Turner & Hankins 2010). It tends to be used when the drugs to be administered needs to be highly diluted or maintenance of steady blood levels of the drug is required (Turner &
Hankins 2010). A continuous infusion is often used to replace fluids and rehydrate a patient. Examples of common infusion fluids used are crystalloids (solutions that, when placed in a solution, mix and dissolve into the solution and cannot be distinguished from the resultant soluton) such as 0.9% sodium chloride, glucose 5%, Hartmann’s solution and sodium bicarbonate, and colloids (solutions used to expand the intravascular space, known as plasma expanders) such as albumin, mannitol, gelatins (e.g.
Gelofusine) hetastarchs and dextrans (Phillips 2010).
Intermittent infusion
This is the administration of a small-volume infusion, i.e. 25–250 mL, over a period of between 15 minutes and 2 hours (Turner & Hankins 2010; Dougherty & Ansell 2011). This may be given as a specific dose at one time or at repeated intervals (Dougherty & Ansell 2011). An intermittent infusion may be used when a peak plasma level is required, the pharmacology of the drug dictates a specific dilution, the drug will not remain stable for the time required to administer a more dilute volume or the patient is on a restricted intake of fluids (Whittington 2008). Drugs commonly administered as an intermittent infusion include antibiotics. Delivery of the drug by intermittent infusion can be via a ‘Y’ set or can be piggybacked (via a needle-free injection port) or a burette set with a chamber capacity of 100 or 150 mL, but only if the primary infusion is of a compatible fluid (Turner & Hankins 2010).
Direct intermittent injection
This is also known as an intravenous push or bolus and involves the injection of a drug from a syringe into the injection port of the administration set or directly into a vascular access device (Turner & Hankins 2010; Dougherty & Ansell 2011). They tend to be used when a maximum concentration of the drug is required in the vital organs. A ‘bolus’ injection may be given rapidly over seconds, as in an emergency, for example adrenaline, where the drug cannot be further diluted for pharmacological or therapeutic reasons or does not require dilution. A controlled ‘push’ injection is given over a few minutes where a peak blood level is required and cannot be achieved by a small-volume infusion (Turner & Hankins 2010).
Rapid administration could result in toxic levels and an anaphylactic-type reaction. Manufacturers’
recommendations for the rate of administration (i.e. millilitres or milligrams per minute) should be adhered to. In the absence of such recommendations, administration should proceed slowly, over 5–10
Box 3.1 The nurse’s responsibilities in relation to intravenous drug administration (adapted from Dougherty & Watson 2011)
•
Knowledge of the therapeutic use of the drug or solution, its normal dosage, side effects, precau- tions and contraindications•
Checking the drug prescription chart•
Preparation of the drug aseptically and safely, checking the container and drug for faults, using the correct diluent and only preparing it immediately prior to administration•
Identification of the patient and allergy status prior to administration•
Checking and maintaining patency of the VAD•
Inspection of the site of the VAD and managing/reporting complications where appropriate•
Control of the flow rate of infusion and/or speed of injection•
Monitoring the condition of the patient and responding to/reporting changes•
Ensuring accurate, legible and immediate documentation of all drugs administered33
Box 3.2 Formula for calculation of the drop rate
Volume to be infused Time in hours
Drop rate
minutes Drops
× =
60 per minute
In this equation, 60 is a factor for the conversion of the number of hours to the number of minutes minutes (Whittington 2008; Dougherty & Ansell 2011). Delivery of the drug by direct injection may be via the cannula through a resealable needleless injection cap, via an extension set or via the injection site of an administration set if the infusion in progress is compatible in order to dilute the drug further and reduce local chemical irritation (Dougherty & Ansell 2011). If the infusion fluid is incompatible with the drug, the administration set may be switched off and a compatible solution may be used as a flush (NPSA 2007).