Introduction

The aim of this study was to assess the presence of a relationship between intra-operative nociception and post-operative pain in dogs undergoing thoracic surgery.

Methods

The study was single-centre retrospective and observational. Clinical records from dogs undergoing median sternotomy and lateral thoracotomy (2015–2019) were reviewed and cases were allocated to one of two groups: NOCI-FREE: dogs with no evidence of intra-operative nociception; NOCI: dogs that required intra-operative rescue analgesia to address a nociceptive response. Intra-operative nociception was identified on the anaesthetic records by at least a 15% increase in heart rate or blood pressure that subsided after the administration of rescue analgesia. Population data (age, breed, sex), type of surgery performed, pre-anesthetic medications, locoregional analgesia, intra-operative infusions and rescue analgesia used, were registered and compared between groups, to assess a possible effect on intraoperative nociception. Post-operative pain scores (Glasgow composite scale) and analgesia plans were also compared between groups.

Results

During the 4.5 years period examined, 104 thoracic surgeries were performed. Statistical analysis was performed on 100 records: 53 were assigned to NOCI-FREE and 47 NOCI. Fifty-one dogs in NOCI-FREE group received loco-regional anaesthesia: extradural (n=5), peripheral nerve block (n=46) while 46 had loco-regional anaesthesia in NOCI, comprising: 3 peripheral nerve blocks (n=38), extradural (n=5), combination of peripheral nerve block and extradural (n=4). The proportion of animals with locoregional analgesia was not different between groups (p=0.09). Being on an intra-operative infusion of lidocaine, fentanyl or dexmedetomidine was identified as a protective factor for nociception [OR=11; (4.15–29.7); p=0.04]. Our study failed to identify a difference in the post-operative pain scores (p=0.22) and post-operative methadone requirements (p=0.07) between dogs having signs of intra-operative nociception and those without. Additionally, the use of post-operative preventive infusions (p=0.21) and the use of rescue analgesia (p=0.98) was similar between NOCI and NOCI-FREE.

Conclusions

In the population studied, it appears that dogs showing signs of nociception intraoperatively during thoracic surgery do not necessarily show higher pain scores nor do they need additionally pain relief in the post-operative period.

Disclosures

No disclosures to report.