Jessie's Pre-Medication Sensitivity

Meet Jessie, a very lively and energetic 7-month-old Kelpie X Border Collie. Jessie has been attending AdelaideVet since she was a week 10-week old pups and has (thankfully) been given a clean bill of health at every visit!

Jessie’s owners brought her in at 6 months of age for desexing, as is routine for most young patients. After being admitted to hospital, Jessie was given a general check-up.  Her heart, lungs, temperature and mucous membranes (gums) were assessed to ensure she was fit and healthy for her operation.

Prior to undergoing anaesthesia, patients are also recommended to have blood screening to assess their organ function – in particular kidney and liver function – to ensure their body is functioning well and can process the anaesthetic drugs properly. Jessie of course had pre-anaesthetic blood screening done which again, showed a clean bill of health. Jessie was ready, fit and healthy for her anaesthetic and desexing procedure!

Anaesthesia for most veterinary patients includes a pre-medication drug, to sedate them and provide some pain relief; an induction drug, which renders them unconscious so we can place an oxygen tube and prepare the patient for surgery; and a maintenance drug, usually a gas inhalant – similar to those used in humans, which they stay on for the duration of the procedure. Jessie was quite lively when she arrived in the morning so she was given an oral medication as part of her pre-medication, to calm and settle her enough for us to place an intravenous (IV) catheter. After her IV catheter had been placed, Jessie was given her pre-medication – made up of a standard combination of drugs used for approximately 90% of otherwise healthy patients. Dr Amber Jurek who was the clinician looking after Jessie for the day noticed she was VERY sleepy after her pre-medication. Some patients are more sensitive than others, so her heart, lungs and gums were checked again. Jessie was completely stable and well - she was just having a great old snooze! After being given the all-clear Jessie was given her induction drug and placed on gas anaesthetic.

Once Jessie had entered theatre the nurse assisting with her anaesthetic notified Dr Jurek that Jessie was seemingly quite deeply asleep under anaesthetic. Dr Jurek checked with her nurse and assessed all the monitoring equipment and noticed that Jessie’s blood pressure and heart rate were lower than expected. Dr Jurek asked the nurse to place Jessie’s IV fluids on a higher rate for 10 minutes to increase the volume of fluid in her blood vessels, to help boost her blood pressure. Within a minute Jessie’s blood pressure was reading higher again. For the rest of the desexing procedure, Jessie’s blood pressure was within the normal range and the desexing procedure and anaesthetic were blissfully uneventful.

After Dr Jurek had finished stitching Jessie’s wound up, her maintenance anaesthetic gas was turned off so that Jessie could wake up from the anaesthetic. Most patients wake up within 15-20 minutes; however, Jessie just kept on snoozing! After 30 minutes had passed Dr Jurek was suspicious something else was at play. Why was Jessie still so asleep when she was on no anaesthetic at all? Dr Jurek pondered on it for a moment, and reflected on Jessie’s initial reaction to the pre-medication. Because she had become so very sleepy and sedated after a standard dose of pre-medication, Dr Jurek was strongly suspicious of a pre-medication sensitivity.

After consulting with the team looking after Jessie, Dr Jurek decided to give a pre-medication reversal drug – to effectively counteract the effects of one of the pre-medication anaesthetic drugs on Jessie’s brain. This reversal drug was given through Jessie’s IV catheter and within 10 seconds she was fully awake and lifting her head, looking around quite puzzled with why so many faces were staring down at her so expectantly. Given this reaction Dr Jurek’s suspicions were confirmed – Jessie was in fact sensitive to one of the pre-medication drugs. Her owners were called and advised of the finding, and everyone was very pleased that her pre-medication sensitivity had been discovered, and that she was recovering so well.

Jessie’s story is an example of how every individual body can respond differently to medications and treatments. Probably close to twenty other patients went under anaesthesia in hospital that week, with the same combination and dosages of the pre-medication drugs Jessie had for her procedure. But Jessie’s body was the only one that was so sensitive. Given anaesthesia requires drugs that sedate the body and brain, the effects and depth of this sedation can vary from patient to patient. Anaesthetic sensitivity is not something most people think about when their pet is admitted for a procedure under anaesthetic. Thankfully, many anaesthetics can be reversed, like Jessie’s pre-medication drug was in this story.

For veterinarian’s and pet owners, it is useful to be made aware of drug sensitivities so that in future scenarios, these drugs can either be used at lower dosages than they were previously or can be completely avoided so procedures are smoother and safer for these patients.

Written by Dr Amber Jurek, Veterinarian.

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