Learn — Medication administration & IV therapy

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Blood transfusion and sampling

Blood transfusion is the intravenous administration of whole blood or one of its components to replace what the patient has lost or cannot make, and it is the one therapy in which a clerical error rather than a pharmacological one is the usual cause of death. Safe practice therefore rests on identification: the sample tube labelled at the bedside from the patient in front of you, and the bedside check of that same patient against that same unit immediately before it runs.

The crossmatch sample is labelled at the bedside, in the patient's presence, immediately after it is drawn; tubes are never pre-labelled and never labelled at the nurses' station, because a mislabelled sample is how an ABO-incompatible unit reaches the ward.
The bedside check is done by two qualified persons at the patient's side and covers the patient's identity by two identifiers, the unit number, the ABO group and Rh type of both the patient and the unit, the crossmatch report, the expiry date and time, and a look at the bag itself for clots, discolouration, bubbles or a leaking port.
One unit is collected from the blood bank at a time, started within 30 minutes of leaving controlled storage, and completed within 4 hours of being spiked; a unit out of storage for more than 30 minutes is not returned to the bank.
Use a blood administration set with an in-line filter of about 170 to 260 microns and a cannula of 18 to 20 gauge in an adult; only 0.9% sodium chloride goes into the same line, never Ringer's lactate whose calcium clots citrated blood, never dextrose which haemolyses red cells, and never any drug.
Take baseline vital signs, then stay with the patient and run the first 15 minutes slowly, because most fatal reactions declare themselves in that window; record vital signs at 15 minutes, then hourly, and again at the end of the unit.
Component knowledge is examined: one unit of packed red cells raises the haemoglobin by about 1 g per dL, one random-donor platelet unit raises the count by about 5,000 to 10,000 per microlitre, fresh frozen plasma is given at about 10 to 15 mL/kg for coagulopathy, and cryoprecipitate is the fibrinogen source.
Storage differs by component: packed red cells at 2 to 6 degrees Celsius, platelets at 20 to 24 degrees with continuous gentle agitation and never in a refrigerator, and plasma frozen and then transfused soon after thawing.
Know the reaction families: acute haemolytic from ABO incompatibility within minutes, febrile non-haemolytic (the commonest, a temperature rise of 1 degree or more, prevented by leucodepleted products), allergic urticaria, anaphylaxis in the IgA-deficient recipient, circulatory overload with a raised jugular venous pressure and hypertension, transfusion-related acute lung injury with hypoxia and normal filling pressures, bacterial contamination, and delayed haemolysis at 5 to 14 days.
Massive transfusion brings its own problems: hypothermia (use a blood warmer for rapid or large-volume transfusion), citrate-induced hypocalcaemia, hyperkalaemia from stored cells, and a dilutional coagulopathy.
Anti-D immunoglobulin is given intramuscularly within 72 hours to an Rh-negative mother who delivers an Rh-positive baby, and to an Rh-negative woman after abortion, ectopic pregnancy or an antepartum sensitising event.

IV fluids — types and indications

Intravenous fluids are sterile solutions given directly into a vein to resuscitate the circulation, to maintain the daily requirement of water and electrolytes when the gut cannot be used, and to replace ongoing losses such as vomit, drainage or fever. Which bag is chosen matters because the tonicity of the fluid decides where the water goes: an isotonic fluid stays in the extracellular space and fills the circulation, a hypotonic one moves into the cells, and a hypertonic one pulls water out of them.

Isotonic fluids are for resuscitation and for replacing extracellular losses: 0.9% sodium chloride carries 154 mmol/L each of sodium and chloride at about 308 mOsm/L, and Ringer's lactate is closer to plasma with sodium 130, potassium 4, calcium 3, chloride 109 and lactate 28 mmol/L at about 273 mOsm/L.
Ringer's lactate is preferred for large-volume resuscitation and for burns because large volumes of saline cause a hyperchloraemic metabolic acidosis, but it is not run in the same line as blood, because its calcium clots citrated blood.
Hypotonic fluids such as 0.45% sodium chloride are for cellular dehydration and maintenance; 5% dextrose is isotonic in the bag but behaves as free water once the glucose is metabolised, so it is never used to resuscitate a shocked patient, and neither is used in a head injury or raised intracranial pressure because they worsen cerebral oedema.
Hypertonic fluids are 3% sodium chloride for symptomatic hyponatraemia and 10% or 25% dextrose for hypoglycaemia; sodium is corrected slowly, by no more than about 8 to 10 mmol/L in 24 hours, to avoid osmotic demyelination, and concentrated dextrose is given through a large vein because it is sclerosant.
Colloids such as albumin and gelatin hold water in the vessel by oncotic pressure, but hydroxyethyl starch is avoided in sepsis and in renal impairment, and no colloid has been shown to save more lives than crystalloid in general resuscitation.
Hourly maintenance by the 4-2-1 rule is 4 mL/kg/h for the first 10 kg, 2 mL/kg/h for the next 10 kg and 1 mL/kg/h for every kilogram beyond 20; the daily Holliday-Segar equivalent is 100 mL/kg for the first 10 kg, 50 mL/kg for the next 10 kg and 20 mL/kg thereafter.
Monitoring is the nursing work: a strict intake-output chart, a daily weight at the same time on the same scale where 1 kg of gain is about 1 litre of fluid, the jugular venous pressure and lung bases, mucous membranes and skin turgor, and a urine output of at least 0.5 mL/kg/h in an adult and 1 mL/kg/h in a child.
The infusion site is checked at least every shift and scored for phlebitis: pain or redness along the vein means phlebitis, while a cool, swollen, tight site with no blood return means infiltration, and the cannula is removed for either.
Label every bag with the patient's name, the additive, the date and time started and the rate, and never add a drug to a running bag without mixing it fully and re-labelling it.

IV cannula — gauges and colour coding

A peripheral intravenous cannula is a short plastic catheter threaded off a needle into a superficial vein, and its size is written as a gauge, a number that runs opposite to the bore so that the larger the number the thinner the cannula. The gauge matters at the bedside because flow rises steeply with the internal diameter, so the choice of cannula decides whether a shocked patient can be resuscitated quickly or whether a fragile vein survives a week of antibiotics.

The standard colours are 14 gauge orange, 16 gauge grey, 18 gauge green, 20 gauge pink, 22 gauge blue, 24 gauge yellow and 26 gauge violet, and the same colours are used across manufacturers for the common sizes.
Approximate gravity flow rates fall away sharply with size: about 240 to 330 mL a minute through a 14 gauge, 170 to 220 through a 16, 90 to 100 through an 18, 55 to 65 through a 20, 30 to 35 through a 22 and about 20 through a 24; exact figures differ with the length and the manufacturer, so read the pack.
Choose the smallest gauge that will do the job in the largest suitable vein: 20 or 22 gauge for most adult ward therapy, 18 gauge or larger for rapid resuscitation, pressurised blood and computed tomography contrast, and 22 or 24 gauge for children, neonates and fragile elderly veins.
Blood is transfused through an 18 to 20 gauge cannula in an adult; a smaller bore under pressure can haemolyse the cells, though a 22 gauge with a pump is acceptable in a child or a patient with no better vein.
Site selection favours the forearm veins, the cephalic, basilic and median, over the back of the hand and over the antecubital fossa, which occludes and infiltrates every time the elbow bends; avoid the arm on the side of a mastectomy, an arteriovenous fistula, a paralysed limb or an area of infection or injury, and avoid the leg in an adult.
Insertion runs: hand hygiene and gloves, tourniquet about 10 to 15 cm above the site, skin preparation with 2% chlorhexidine in 70% alcohol rubbed for 30 seconds and allowed to air dry without fanning or wiping, the needle bevel up at roughly 10 to 30 degrees to the skin, advance the cannula off the needle after flashback, release the tourniquet, activate the safety device, flush with 0.9% sodium chloride, secure with a sterile transparent dressing and label it with the date, time and gauge.
Assess the site at least once a shift and before every infusion for the signs that end its life: pain, redness or a palpable cord along the vein is phlebitis, and coolness, swelling, tightness and loss of blood return is infiltration.
Current standards remove a peripheral cannula on clinical indication rather than by a fixed 72 or 96 hour clock, but any cannula placed in an emergency without full asepsis is replaced as soon as the patient is stable, and one that is no longer used is taken out.
Never re-insert the needle into a cannula that has been partly withdrawn, because the tip can be sheared off and embolise.

Drug calculation basics

Drug calculation is the arithmetic that converts a prescription into what the nurse actually hangs, draws up or counts out: a volume from a stock strength, a drop rate from a gravity set, or a millilitre-per-hour rate from a weight-based infusion order. It matters because the nurse is the last checkpoint before the drug reaches the patient, and a misplaced decimal point in a paediatric or high-alert drug is a tenfold error that no later step will catch.

The basic dose formula is desired divided by what you have, multiplied by the volume the stock comes in: an order for 750 mg from a stock of 1 g in 4 mL gives 750 divided by 1000, multiplied by 4, which is 3 mL.
Drops per minute equal the volume in millilitres multiplied by the drop factor of the set, divided by the time in minutes; macrodrip sets are 10, 15 or 20 drops per millilitre and blood sets are usually 15, while a microdrip or paediatric burette is always 60 drops per millilitre.
With a 60 drops per millilitre microdrip set the number of drops per minute is the same as the number of millilitres per hour, which is the quickest bedside cross-check there is.
An infusion pump rate in millilitres per hour is simply the total volume divided by the number of hours it is to run over.
A weight-based infusion converts as rate in mL/h equals the dose in micrograms per kilogram per minute, multiplied by the weight in kilograms, multiplied by 60, divided by the concentration in micrograms per millilitre; dopamine at 5 micrograms/kg/min for a 60 kg patient from 200 mg in 500 mL (400 micrograms/mL) is (5 x 60 x 60) divided by 400, which is 45 mL an hour.
Know the unit conversions cold: 1 g is 1000 mg, 1 mg is 1000 micrograms, 1 litre is 1000 mL, and 1 kilogram is about 2.2 pounds.
A percentage solution is grams per 100 mL, so a 1% solution is 10 mg/mL: 2% lignocaine is 20 mg/mL, 25% dextrose is 250 mg/mL, and a 1 in 1000 adrenaline ampoule is 1 mg/mL while 1 in 10,000 is 0.1 mg/mL.
Paediatric doses are calculated by body weight in mg/kg or by body surface area; the classical examination formulas are Clark's rule, the adult dose multiplied by the child's weight in pounds divided by 150, and Young's rule, the adult dose multiplied by the age in years divided by the age plus 12.
Insulin is measured only in an insulin syringe graduated in units for the U-100 strength, never in a millilitre syringe, and the word units is written out in full and never abbreviated.
High-alert drugs, including insulin, heparin, concentrated electrolytes, opioids and chemotherapy, are independently double-checked by a second nurse who repeats the calculation rather than merely agreeing with it.

Medication administration — rights and routes

Medication administration is the nurse's independent verification of a prescription, followed by the preparation and delivery of the drug by the correct route and the recording of what was given and what happened. It matters because the nurse is the last of several checkpoints and the only one standing at the bedside, so the rights and the three checks are not a ritual but the last chance to stop an error before it reaches the patient.

The rights are checked every time: the right patient identified by two identifiers and never by bed number, the right drug, the right dose, the right route, the right time, and then the right documentation, the right reason or indication, the right response, the right education and the patient's right to refuse.
Three checks are made against the medication chart: when the drug is taken from the shelf or trolley, when it is prepared or poured, and again at the bedside before it is given; the label is read all three times.
Routine doses are given within about 30 minutes either side of the scheduled time, while time-critical drugs such as insulin, antibiotics in sepsis, anti-parkinsonian drugs and anticoagulants are given at the time and are not held for convenience.
Intradermal injection goes in at 5 to 15 degrees with the bevel up into the inner forearm or the deltoid area using a 26 or 27 gauge needle, delivers about 0.1 mL and must raise a visible wheal that is not massaged; it is the route for the Mantoux test and for BCG.
Subcutaneous injection goes in at 45 to 90 degrees (90 degrees with a short insulin needle, 45 degrees in a thin patient) with a 25 or 26 gauge needle, delivers up to about 1 mL into the abdomen, outer upper arm or anterior thigh with rotation of sites; do not aspirate before insulin or heparin and do not massage after heparin.
Intramuscular injection goes in at 90 degrees with a 21 to 23 gauge needle: the ventrogluteal site is the safest in an adult and takes up to about 3 mL (more in a large adult), the vastus lateralis is the site of choice in an infant and takes about 1 mL, the deltoid takes 1 mL and is used for vaccines, and the dorsogluteal site is avoided because of the sciatic nerve.
The Z-track technique is used for irritant or staining drugs such as iron: pull the skin laterally about 2.5 cm, inject, wait 10 seconds before withdrawing the needle, then release the skin so the track seals and the drug cannot leak back.
Oral rules that are examined: enteric-coated and sustained-release tablets are never crushed, sublingual and buccal tablets are not swallowed or taken with water, and a drug given through a nasogastric tube needs the position checked, a liquid or fully dispersed form, and a flush before and after.
Eye drops go into the lower conjunctival sac and not onto the cornea, with gentle pressure on the inner canthus for a minute; drops go before ointment and two different drops are separated by about 5 minutes; ear drops are warmed to room temperature and the pinna is pulled up and back in an adult and down and back in a child under three.
High-alert drugs, including insulin, heparin, concentrated electrolytes, opioids and chemotherapy, need an independent double check; potassium chloride is never given undiluted or as a bolus, and error-prone abbreviations such as U for units are not used.
Never give a drug that somebody else prepared and never leave a drug at the bedside; a verbal or telephone order is read back, written down and countersigned, and it is used only in an emergency.
After an error, assess and treat the patient first, then inform the doctor and the nurse in charge, then record the facts in the patient's notes and complete an incident report, which is filed separately and not in the patient's chart.

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