Ketamine is a highly specialised pain management drug. It was invented in the 1960s for use in anaesthesia. These days it is mainly used in disaster relief or emergency anaesthesia. Vets often use it as an anaesthetic agent. Its use in the management of chronic pain arose when people recovering from anaesthesia who had chronic pain reported improvements in their pain, which lasted sometimes for months following the ketamine anaesthesia.
Research into how best to use ketamine infusions is ongoing. The Wikipedia page for ketamine has a lot of background information regarding the use of ketamine in anaesthesia, but only a little information about the type of infusion you will be having.
Ketamine infusions as done by Pain Matrix involve delivering a carefully controlled dose around the clock via a small pump. A butterfly needle is placed in the skin of your abdomen so that the ketamine being pumped in forms a small 'puddle' under the skin. This puddle is absorbed into the bloodstream, which allows the level of ketamine to rise in a steady fashion. This is called the subcutaneous route of drug delivery.
Compared to the more familiar intravenous route where the drug is to leave it directly into the bloodstream, there is less risk of hospital-acquired infection and a wider margin of safety if there are problems with the pump. Although there are still some pain practices, which do their ketamine infusions intravenously, we believe that the subcutaneous infusion is safer and suits our patients better.
When you come in for your first trial of ketamine infusion, the starting dose will be very low. This is because some people (less than 1%) are very sensitive to even lower doses. The doses are reviewed every 24-hours and slowly increased until the desired pain relief is obtained, or side effects begin to occur.
Because of the slow and steady protocol that we use, side effects are generally predictable and are at the milder end of what ketamine can cause. A feeling of slight sedation, perhaps even some grogginess is common as the dose increases into the range where most people get some benefit.
Problems concentrating or judging distances are also predictable as these parts of the brain contain nerve cells, which can be blocked by the action of the ketamine. Actually more unpleasantly end of these effects, a feeling of 'floating' or lack of spatial awareness can occur. This goes away (as do all the ketamine related side-effects) within a few hours of ceasing the infusion. At very high doses, disorientation and forgetfulness can occur.
Hallucinations and behaviour can also occur with very high doses. Few of our patients require doses at the high end of the range where these side effects may occur, and though we do several infusions a week we might see hallucinations occur in one patient every couple of years. The senior nurses on the ward have quite a bit of experience with these infusions and are happy to explain them in detail and answer questions about symptoms you think may be related to the ketamine.
Allied health professionals like physiotherapists and psychologists are available to see you on the ward while you are having the infusion, and can assist with assessments or advice about a range of issues. Your pain specialist will usually have mentioned if you will be seeing any of these professionals during the admission.
You should plan to continue your normal pain relief measures, including medications, while on the ketamine. If the plan for your infusion involves lower doses of your current medications, your pain specialists will supervise these changes during the infusion. You don't need to worry about trying to reduce or stop medications yourself. Leave that to us!
While the infusion is running you will be able to walk around, get dressed and mostly do normal things, as the infusion pump can be kept in a small satchel that you wear around your neck. We encourage people to dress in their normal clothes and try to be active around the ward. You can even go out of the ward to the coffee shop to sit and chat with visitors if you like. After all you only have pain, you're not actually sick!
You will be asked to fill out some questionnaires before starting the ketamine, and also on the day you go home. The idea of these is for us to be able to document whether an improvement has taken place, and if so, by how much the pain has gotten better. Collecting these questionnaires on large numbers of patients will allow us to audit our results and contribute to the research literature on how to use ketamine best.
If there are other particular questions you or your family have, note them down in the space below and bring them in so the nurses or pain specialists.