Comparison of mean heart rate in anaesthetized dachshunds and other breeds of dog undergoing spinal Magnetic Resonance Imaging

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Clinical experience suggests that dachshunds are prone to bradycardia during general anaesthesia (GA). The study investigated mean heart rates in anaesthetized dachshunds and other breeds of dog.

Study Design

Retrospective clinical study.


Sixty one dachshunds and 62 dogs of other breeds met inclusion criteria.


Clinical records of small breed dogs undergoing GA for spinal Magnetic Resonance Imaging between September 2008 and March 2010 were identified and examined. Data collected included drugs administered, baseline heart (HR) and respiratory (fR) rates and rectal temperature. The following information was noted from anaesthetic records: HR, fR, mean non-invasive arterial pressure and end-tidal carbon dioxide (Pe′CO2) and anaesthetic agent (Fe′agent) during the first 60 minutes of anaesthesia; rectal temperature at a time closest to the cessation of anaesthesia, ventilatory mode (spontaneous/mechanical) and fluid infusion rate. Univariate analysis with Student t-test and Fisher's test identified parameters significant in predicting a lowered HR. A multivariate analysis investigated their effect on the mean HR during GA.


No differences were found between groups regarding: age, baseline HR, baseline temperature, incidence of hypotension, Fe′agent, mean Pe′CO2 and fluid infusion rate. Body mass was smaller for dachshunds (6.7 ± 1.5 kg) compared to other breeds (7.8 ± 1.8 kg) (p = 0.0005). The lowest HR recorded was lower in dachshunds (64 ± 19 beats minute−1) compared to other breeds (72 ± 21 beats minute−1) (p = 0.03). Mean HR was lower in dachshunds (75 ± 21 beats minute−1) compared to other breeds (84 ± 21 beats minute−1) (p = 0.02). Post-procedural temperature (°C) was lower in dachshunds (35.5 ± 1.1) compared to other breeds (36.1 ± 1.2) (p = 0.007) and anticholinergics were also administered more frequently (p = 0.026). Multivariate analysis identified that breed and mean Pe′CO2 affected mean HR during anaesthesia.


This study supported our hypothesis that dachshunds have a lower mean HR under GA than other small breed dogs.

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