Oxygen inhalation improves postoperative survival in ketamine-xylazine anaesthetised rats: An observational study

Abstract

ObjectiveA simple but reliable and safe anaesthetic procedure is required for surgical interventions in small rodents. Combined ketamine and xylazine injections are often used in rats for less invasive surgery, possibly with spontaneous breathing and without airway management. However, there are important pitfalls to be avoided by special precautions and monitoring, as shown subsequently.Study designObservational study.AnimalsTwenty-four anaesthetic procedures for bile duct ligation, sham operation or carotid artery dilatation in 20 male Sprague-Dawley rats, preoperatively weighing between 440 and 550 g.MethodsIntolerable high mortality rates occurred in the first 7 postoperative days while establishing a new experimental model in rats using ketamine-xylazine anaesthesia. Rats were spontaneously breathing ambient air during the first 12 surgeries without airway management. An observed high mortality rate in these animals led to a change in the trial protocol: the insufflation of 2 litres of oxygen per minute via nose cone during the following 12 rat surgeries. Retrospective comparison of the outcome (without oxygen vs. with oxygen insufflation) was conducted.ResultsThe perioperative mortality rate could be significantly reduced from 58% (7/12) to 17% (2/12) (p = 0.036) by oxygen insufflation via nose cone. Significantly different levels of intraoperative oxygen saturation (SpO2; 89 ± 4% [without oxygen] vs. 97 ± 0.5% [with oxygen], p < 0.0001), but no significant differences in heart rate (HR; 267 ± 7 beats minute–1 [bpm] [without oxygen] vs. 266 ± 6 bpm [with oxygen], p = 0.955) were observed.Conclusions and clinical relevanceIn summary, rats under ketamine-xylazine anaesthesia are susceptible to hypoxia. This may lead to increased delayed mortality related to hypoxia induced lung failure. Apparently, this is an underestimated problem. We highly recommend using additional oxygen insufflation in spontaneously breathing rats under ketamine-xylazine anaesthesia with basic monitoring such as measurement of oxygen saturation.

Sevoflurane versus ketamine+diazepam anesthesia for assessing systemic and hepatic hemodynamics in rats with non-cirrhotic portal hypertension

“…First, sevoflurane entirely prevented anesthesia-related mortality as opposed to the 21% mortality observed in the group anesthetized with KD. Of note, KD-related mortality in our study compares favorably against other prior studies, in which up to 30-60% intra-and peri-operative mortality rates have been reported [13,14].…”

“…route (between 150% to 435% higher) [26]. Other alternatives explanations are also possible, such as the increased susceptibility to hypoxia suggested in a recent study [14]. In this regard, significant differences in arterial blood gases parameters were present between sevofluraneand KD-anesthetized animals that survived the full study.…”

“…Indeed, an unpredictable individual sensitivity to ketamine resulting in associated intra-operative mortality of up to 30% has been reported, particularly in cirrhotic rats [13]. A recent study in rats anesthetized with ketamine+xylazine undergoing diverse surgical operations (median laparotomy, bile-duct ligation, or balloon dilatation of the carotid artery) suggested that hypoxia may be a contributing factor, as oxygen supplementation reduced the mortality [14]. Studies comparing the performance of different anesthetics in the setting of cirrhosis or portal hypertension, however, are scarce and limited to relatively old studies that do not include the newer anesthetic agents [13,[15][16][17][18][19] (see Table 1 for a summary).…”

The effects of post-operative oxygen supply on blood oxygenation and acid-base status in rats anaesthetized with fentanyl/fluanisone and midazolam

“…As reported in other studies [ 1 , 4 ] and our own experiences in a rat model for abdominal aortic aneurysm, oxygen supply prevents hypoxia during the surgical procedure. We wished to investigate if prolonged oxygen supply during a post-operative period of one hour, further improved blood oxygenation and if this had an influence on the arterial acid-base status.…”

“…It is well known that oxygen supply during surgery in rodents improves post-operative recovery. In rats anaesthetized by ketamine and xylazine, oxygen supply during the procedure reduced mortality from 58% to 17% during bile duct ligation [ 1 ]. As a reason for mortality, drug induced hypoxia was suggested.…”