RE: Should animals be starved overnight prior to anaesthesia?

Gwen Covey-Crump — Mon, 18 May 2020 13:56:23 GMT

In agreement with Carl's comments, published evidence on fasting period is conflicting. Feeding at 6am in a mature healthy patient due to have a morning procedure is unnecessary, better to provide a small snack late the night before e.g midnight checks if in hospital or ask the owner to feed a small 'supper' at their bedtime rather than fasting from 7pm or whenever the dog usually has its dinner. Factors that influence gut transit time include fat content of food, wet v.s. dry kibble, stress, pain, trauma. So a healthy dog having elective surgery that is not especially stressed may be fine having a small canned food breakfast at 6am (through my experience I would still suggest not to do this) where a dog that is in pain, maybe on opioids and stressed in the clinic, will very likely still have that food in the stomach when it comes to anaesthesia. It is simple to monitor blood glucose if you are concerned about hypoglycaemia and treat accordingly.

RE: Should animals be starved overnight prior to anaesthesia?

Carl Bradbrook — Mon, 18 May 2020 09:34:08 GMT

I do not think hypoglycaemia is something I am concerned about (in healthy, mature patients) following a period of fasting. In immature patients, and those with clinical disease e.g portosystemic shunt this is something I would be monitoring for, and intervening as needed with glucose/dextrose supplementation.

Thinking about the potential for the risk of regurgitation there is some conflicting evidence, but a recent clinical study demonstrated an increased risk of reflux/regurgitation in healthy dogs when a shorter starvation period was used. They used 3hrs versus 12-18hrs (overnight fasting). Other factors were also shown to be important, increasing age and positioning in dorsal recumbency. With this in mind I advise overnight fasting in elective procedures in out healthy, mature patients and discuss immature patients, emergencies/urgent cases on an individual basis. When we use a shorter starvation period in an emergency situation then we take further precautions to reduce the risk of any gastric contents being aspirated, and if necessary using prophylactic gastroprotection.

[quote userid="20777" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/expert-help/29103/should-animals-be-starved-overnight-prior-to-anaesthesia"]As a compromise would a small snack at 6 am be a safe compromise when anaesthesia occurs 2 1/2 hours later ?[/quote]

Is there a particular reason you would like to feed the animal at this time? I would be cautious with this approach in an elective procedure, unless dictated by the patient and disease presentation and prefer to monitor blood glucose and supplement if needed and use a longer fasting period.

[quote userid="20777" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/expert-help/29103/should-animals-be-starved-overnight-prior-to-anaesthesia"] I have seen a case of aspiration pneumonia in recovery when an owner had given their pet a meal 3 to 4 hours prior to anaesthesia [/quote]

Regurgitation and aspiration of gastric contents is a risk associated with anaesthesia, and may occur with any length of fasting. Shorter periods of fasting appear from the 2017 study to be associated with an increased risk of reflux, but there is little information detailing the incidence of the potential sequelae such as oesophageal stricture formation or regurgitation and aspiration.

Carl