Rebound Defined, Diabetic Cat Care

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Diabetic Cat Care

Rebound Defined

You might be thinking your cat is experiencing the Symogi Effect - a believed condition when BG are high every morning. That may be possible (although unlikely). More often than not what you're seeing with your test results is likely some form of Rebound.

On forum you will hear many words and phrases used when it comes to "rebound" - liver tantrum, hissy fit, liver push back and zoom-zoom are some of them. There are a few different “kinds” of rebound which are described below:

Typical Rebound:

The term "rebound" is used when a cat's BG drops to a point that the liver feels is too low, and the liver then acts to correct that by bringing the BG back up to numbers that IT (temperamental Miss Liver) considers "safe." This type of rebound occurs in two separate scenarios.

The first typical form is very common and is usually seen in a newly diagnosed cat who has just started insulin - in fact it is an entirely expected result and a typical response with TR when first starting out. The cat presents with high BG at the start of TR, and the cat's liver has come to accept the high BG as "normal" over time. The liver does not know that normal range BG are from 2.8/50 to 8.3/150 and it must be retrained to accept normal range BG once again. When given insulin and the numbers start to drop considerably lower than what the liver "thinks" is safe, the liver responds by kicking out glycogen to bring the BG back up to a level the liver mistakenly believes is "normal". This usually happens around mid-shot, when the insulin has dropped the BG into lower numbers than the cat has been in for quite a while, and then by the time the insulin starts to leave the system, we see a much higher number than we started with at PS (pre-shot). The BG at nadir (insulin's peak action/lowest BG on the shot) is usually no where near low; rather it is simply a good amount lower than what the liver has come to "accept" as normal. The cause for this type of rebound is usually a combination of the amount and speed of the drop, rather than the actual BG at nadir. This is a very expected form of rebound at the start of TR when the cat starts getting to numbers lower than it has been in for quite some time. Dr. Hodgkins' advice is to shoot into it - to keep the insulin flowing at normal dosing time for the insulin type used (assuming the cat needs insulin of course), until the liver gets used to the lower numbers. This expected kind of rebound usually resolves fairly quickly.

The second typical form of rebound is usually tied to an overdose situation, where the insulin dose is too high. In this type of rebound, the BG drops too low - below 2.2/40 for most cats, even lower for others, and sometimes drops low early on the shot. Some cats will spend a good amount of time "coasting" in lower numbers - some will start to rise very quickly - regardless, eventually the BG skyrockets upwards into high numbers. This is also a very typical form of rebound and typically happens with cats whose pancreas is starting to work again, or they've been on insulin for a while so their functioning livers recognize truly low numbers. This kind of rebound has more to do with the BG at nadir than it does with the overall amount or speed of the drop itself but it can also be the combination of amount, speed of the drop and the BG at nadir. In this case, we wait to see if low BG occurs more than once and relatively close together before adjusting scale downwards.

Chronic Rebound:

The second type of rebound (mentioned above) is frequently referred to as "chronic" because it is a repeating occurrence, and is very common with cats who are not being tested as frequently as we do with TR. The problem stems from the fact there isn't testing being done in order to know what's going on inside. It is not at all uncommon because the only test being done is at shot time if at all (or by Fructosamine or a one day curve at the vet's) for it to be assumed there is need of increased insulin to get the BG down and the owner is advised to keep adding to the dose - usually in half or full units. Many cats who find their way to DCC are experiencing this kind of "chronic" rebound and typically they'll end up on much smaller doses once they've started TR.

Another form of chronic rebound occurs occasionally, and is referred to as “flats”. In this scenario, the cat has usually been on insulin long enough that the liver is functioning well and has relearned what is “normal” in terms of the BG. Most cats who show this kind of rebound have been on TR for at least a month if not longer and are generally fairly well regulated.

When a cat who is used to being well-regulated (in normal numbers for the most part), is given too much insulin (not a huge overdose, just a little too much) - depending on the insulin type, you may see a small drop occur at +2 but typically by +4 and beyond you get a series of BG numbers that are usually within 20 to 40 points (imperial) of each other and is the reason for the term "flats". Sometimes "flats" can occur with a wider spread, as much as 100 points of each other; although this is more common with the longer lasting insulin types. The BG only drops when the shot wears off, somewhere around +9 or beyond depending on the insulin type. This is usually an ongoing thing, happening several shot cycles in a row, where the caregiver sees the higher numbers, and raises the doses in an effort to get the numbers down, resulting in yet another series of “flats.”

When dealing with a cat who has been on insulin for a while but whose numbers are staying high and flat; while for this cat the “flats” theory should be considered as a possibility before significant increases are given; it is very important to remember "flats" very rarely happen in a newly diagnosed cat whose liver has not yet been retrained to recognize normal BG levels. Experienced members on forum can help you with what steps to take to determine if your cat is actually experiencing the "flats" or not.

For cats who have been in high BG for a long time, it is also important to understand there may be some resistance to insulin at the start of TR as the liver "jockeys for position". In the case of these cats, increases to scale will usually confirm or deny if the "flats" are in play. Time and again, it will prove that more insulin (not less) is the answer when it comes to newly diagnosed cats.

In the event BG becomes flat without any real explanation, a review of the things which might affect BG should be ruled out; this includes verifying when the current vial of insulin was opened (should be determined first), confirming a proper low carb diet is being fed (that there are no inappropriate treats, or "outside" opportunities to get into high carb foods, or there has not been over-feeding), correct shot placement and measurement of insulin doses, proper conversion if using U100 needles with U40 insulin, other health issues, etc. all should be ruled out first. There is a full checklist of questions in the Guidelines for Advice Givers sticky in the TR College of Knowledge.

Ruling out too little insulin is done by raising the the dosing scale for a three shot cycle, usually - ECID. If the numbers show some downward movement with an initial increase, then further increasing is in order - whether done in 0.25u or 0.5u increments, depends on the insulin type and how high the BG are. For example if the BG is over 13.9/250, 0.5u increases may be called for (depending on the insulin type). If the BG is lower than 13.9/250, then perhaps 0.25u increases will be enough to bring the BG to normal range numbers, again depending on the insulin type. The goal is to get the BG down to normal range numbers below 8.3/150 as quickly as possible, and ideally into the 2.8 to 3.8/50 to 70 range which are healing numbers.

If, after raising the scale a couple of times there is no downward movement of any kind; rather there is a continued series of high, relatively flat numbers, even with overlap having been maintained between doses, that is the time to consider chronic rebound might be in play and trying a reduced dose for a few shots is recommended to confirm or deny.

The key to confirming or denying chronic rebound is not to stick with a strategy that isn't working for long. If after a few shots your cat is not responding to a reduction to determine if chronic rebound is in play, then the next step is to start increasing once again, steadily and with confidence until ideal range bg of 2.8 to 3.8 / 50 to 70 are achieved. The lows are better than the highs and as Dr. H advises, "don't be afraid of the insulin".

To summarize:

Typical rebound is just that - typical and very much expected at the start of TR, or rebound can occur when there is too much insulin on board. When on TR, Chronic rebound is usually identified by "flat" numbers, and is for the most part caused by just a bit too much insulin - flats do not normally happen with newly DX'd cats, if their BG is flat, it almost always means there's not enough insulin on board.