7.1 Patient factors affecting extravasation
Certain groups of patients are more likely to develop problems after extravasation and should therefore be monitored closely.
7.1.1 Neonates
Neonates, particularly pre-term neonates, possess less subcutaneous tissue than adults, and their veins are smaller and in some cases more fragile. In addition, any extravasated material is more concentrated in the affected area. They are also much less able to vocalise their pain (see below).
7.1.2 Patients unable to vocalise/communicate their pain
Comatose or anaesthetised patients, or those being resuscitated, are not able to provide clear vocalisation of the pain caused by extravasation of a substance. They (and the neonates mentioned above) form perhaps the group of patients at greatest risk from extravasation.
7.1.3 Patients unable to sense pain
Special care should also be taken when administering injectables to patients who have an impaired ability to detect pain. Patients who suffer from peripheral neuropathy (e.g. people with diabetes) are one such group.
7.2 Medicine factors affecting extravasation
The pharmacological properties of a drug influence its ability to induce tissue damage.
7.2.1 Cytotoxic medicines
Several cytotoxic agents will cause extensive tissue damage if extravasated because they are directly toxic to the cells that they come into contact with. Centres that administer cytotoxic agents must have local extravasation guidelines, which should stipulate how to manage the incident according to the type of agent extravasated.
7.2.2 Vasoactive medicines
When vasoconstrictor medicines are administered peripherally, extravasation can produce local vasoconstriction, leading to severe tissue hypoxia and ischaemia. Vasoconstrictors include adrenaline (epinephrine), noradrenaline (norepinephrine), dopamine and vasopressin.
7.2.3 Irritant medicines
The chemical properties of the drug may influence its propensity to cause tissue damage.
Drug solutions with a pH less than 5.5 or greater than 8.5 may cause tissue damage if they infiltrate subcutaneous tissue as they disturb the normal cellular environment. Blood and tissue fluid have a pH of 7.4 and deviation from this pH will cause damage to cellular structures, particularly by disturbing the function of proteins. The table below shows examples of medicines that have particularly high or low pHs. The reader should note pH values may vary slightly between different preparations of medicine, according to the manufacturer’s formulation.
All solutions exert an osmotic pressure, dependent on the amount of substance dissolved in the solution. The tonicity of a solution is measured relative to water, which has an osmolarity of 0 mOsmol/L. Solutions with an osmolarity more or less than that of plasma (~290 mOsmol/L) may cause tissue damage. The presence of these solutions can lead to an osmotic imbalance across the cell membrane, leading to the movement of water into or out of the cell, a breakdown of cellular transport mechanisms and cell death. Most injectables are formulated to have the same osmotic pressure as plasma so that the solution to be injected into the patient is unlikely to cause vein irritation. The table below lists a selection of medicines that have high osmolarity and may potentially cause a problem if extravasated. Extra care should be taken when administering these medicines.
Medicines with high or low pH values
| Intravenous medicine | pH |
| Acetazolamide | 9.1 |
| Aciclovir | 11.3 |
| Adrenaline (epinephrine) | 2.8-3.6 |
| Aminophylline | 8.8-10 |
| Amiodarone | 3-5 |
| Argipressin | 3-5 |
| Atracurium | 3.5 |
| Atropine | 2.8-4.5 |
| Azathioprine | 10-12 |
| Buprenorphine | 3.5-5.5 |
| Clonazepam | 3.5-4.5 |
| Co-trimoxazole | 9-10.5 |
| Cyclizine | 3.3-3.7 |
| Dantrolene | 9.5 |
| Dobutamine | 2.5-5.5 |
| Dopamine | 2.5-5.5 |
| Doxapram | 3-5 |
| Ergometrine | 2.7-3.5 |
| Fentanyl | 4-7.5 |
