The Brain: Worst Enemy in Tick Paralysis
Recently studies on human volunteers in Europe in 2011 showed how the brain reacts when blood oxygen levels drop.
Participants were put in a room with gradually decreasing levels of oxygen, and asked to perform mental puzzles and physical exercises.
What they found was the brain diverted energy to itself at the expense of energy being delivered to the muscles. The volunteers could perform mental puzzles quite well, but were unable to perform physical exercises because the muscles were being fatigued.
How is this relevant to tick poisoning?
In tick paralysis cases, a drop in oxygen delivery is caused by several factors such as:
- Paralysed diaphragm, rib and abdominal muscles used for sucking air into the lungs
- Fluid buildup in the lungs if the heart is affected by the tick poison
- Parlaysis of the vocal chords not allowing a fresh flow of air into the lungs
- Build-up of saliva in the back of the throat (pharynx) due to an inability to swallow
The brain detects this drop in blood oxygen and initiates the reflex mentioned above.
This reflex fatigues the diaphragm, rib and abdominal muscles while the brain “looks after itself”.
As these muscles are used to breathe in, there is a further reduction in the delivery of oxygen to the body, and the brain in turn will fatigue the muscles even more. A viscous circle.
Major cause of death
This brain reflex is the most common reason we lose tick cases.
In cases where the pet is having increased difficulty breathing (dyspnoea) because of the fatiguing of the breathing muscles, it is best to knock the brain out so the reflex disappears. That way the muscles can work properly and a good supply of air/oxygen can get into the lungs.
How to knock the brain out?
A general anesthetic (G/A) is the answer.
Humans with reduced oxygen delivery problems (e.g. major trauma) are placed in a coma.
When pets are placed under G/A there is an immediate improvement in the delivery of oxygen around the body as the breathing muscles start working again.
At the same time, while the pet is under G/A, we can easily place oxygen tubes down the windpipe (trachea) right down to the lungs.
The bad news…well, not too bad
Placing an animal under G/A requires someone to be with the animal while it’s asleep. For us, that means a nurse/vet during the day but at night if it’s an after hours case, it means the vet on call will probably have to stay all night at the hospital to ensure the pet does not wake up and start chewing the tubes in its throat.
Not so good for the vet if he/she has a full day of work ahead.
Not so good for the owner as the vet has to be paid for his time and expertise.
For those living in Sydney or the ACT, pets are transported to 24hr Emergency Clinics.
For country vets, it usually means using a long acting anesthetic agent called Pentobarbitone. It is given intra-venously (IV) and lasts for 4-6 hours. An initial IV dose can be “topped up” by connecting the pet to an IV drip containing Pentobarbitone which trickles in at a very slow rate.
How long does the pet stay anaesthetised?
By placing a pet under G/A, we buy ourselves some time for the body to repair the damage done by the tick toxin. Most of this damage occurs where the nerves attach to the muscles in the body. That’s why the muscles don’t work as well as they should. This may take 12-48 hours or longer. Pets are “woken up” at certain intervals to see how they cope with breathing “awake”- if they can’t cope, they get some more anaesthetic. Once they are more relaxed and able to take deep breaths, they are taken off the anaesthetic.