Calculating a cytarabine dose
Chemotherapeutic drug doses are often calculated using the animal ' s body surface area( BSA)( Appendices 1a and 1b [ 14, 15 ]) rather than its bodyweight. This is to reduce the risk of overdosing the patient, as bodyweight can give a poor indication of drug metabolism and distribution. An example of drug dose calculation using an animal ' s BSA is given below:
Patient bodyweight = 10 kg
10 kg equates to a BSA of 0.47 m 2 using the BSA conversion chart [ 15 ]
Dose to administer = 200 mg / m 2
Actual dose = 0.47 × 200 = 94 mg: this is the total dose of cytarabine required.
Before any attempt is made to draw up the cytarabine, the total amount of drug required must be checked, checked and checked again! Having a section of the patient ' s hospital sheet, or a separate cytarabine administration sheet, is extremely beneficial for all staff involved. Having boxes next to the calculation to allow three staff to initial( to indicate that a triple check has been done) is a good way of showing that the calculation has been checked as needed. Appendix 2 provides an example of the author ' s cytarabine CRI hospital chart.
Drawing up the cytarabine
First, the VN drawing up the cytarabine should don the appropriate PPE – gown, double gloves, goggles and face guard. They should then place down the absorbable layer, such as an incontinence sheet, and prepare the laminar flow cabinet, if one is being used.
The author advises putting the administration set together before drawing up the cytarabine. This will allow the cytotoxic drug to be transferred immediately to the administration assembly once it has been drawn up.
The following steps should be followed to draw up the cytarabine safely.
1. Remove the lid of the vial to reveal the piercable top. 2. Wipe the top of the vial with an alcohol wipe. 3. Pierce the top of the vial with the CSTD vial adaptor.
4. Swab the top of the CSTD vial adaptor with an alcohol wipe.
5. Confirm the dose once more before attaching the CSTD syringe adaptor aseptically to a Luer-lock syringe of an appropriate size.
6. Remove the cap of the CSTD syringe adaptor and wipe it with an alcohol wipe before carefully connecting it to the cytarabine vial adaptor until a click is heard.
7. Invert the cytarabine vial and start to draw back the syringe to allow the cytarabine into the syringe until the correct volume is reached.
8. Once the correct dose is in the syringe, carefully detach the vial adaptor and replace the cap on the CSTD syringe adaptor.
Every administration set should have a Luer-lock adaptor to connect the syringe containing the cytarabine, to help ensure a sterile transfer. Examples of this type of adaptor include a spike port adaptor for a saline bag( this option was used in Approach 2, mentioned earlier). When using this type of adaptor, take the administration set and wipe the spike port adaptor with the second alcohol wipe. Uncap the CSTD syringe adaptor and carefully attach it to the spike port adaptor, then slowly transfer the drug. Once done, remove the CSTD syringe adaptor and attached syringe, and replace the cap. Wipe the top of the spike port adaptor with an alcohol wipe again. The person preparing the dose can then remove their outer gloves.
It is good practice to label the fluid bag, giving set and extension line clearly with cytotoxic drug labels. Complete a drugs label with the animal ' s name, drug name and dose, date, time, and the initials of the prescribing VS and preparer, and stick it to the saline bag. Place the whole of the administration set into a basket lined with an incontinence sheet for transport to the kennel area for attachment to the patient [ 13 ].
If it is not possible to draw up the cytarabine for the CRI in the practice, there are companies that can prepare and send pre-drawn doses for the patient. This is an effective way of being able to deliver a cytarabine CRI without the practice having to purchase expensive equipment. If using this option, PPE will still be required as well as a CSTD connection device for administration. The correct dose must be calculated before ordering it, which may not be suitable for emergency situations.
Dealing with spillages
A spill kit should be available in close proximity to where drug preparation takes place, and another spill kit should be kept in the kennel area for the duration of the patient ' s stay [ 3 ].
Essential items to be included in a spill kit:
• PPE – gown, gloves, eye protection, respiratory mask and shoe protectors
• Absorbent pads, such as incontinence sheets
48 Veterinary Nursing Journal