Campoy et al. (2012).

Comparison of bupivacaine femoral and sciatic nerve block versus bupivacaine and morphine epidural for stifle surgery in dogs

Aim: To determine whether a bupivacaine femoral and sciatic nerve block (F+S) provides superior analgesia, and fewer residual block effects compared to a bupivacaine and morphine epidural (EPID) in dogs undergoing unilateral tibial plateau levelling osteotomy (TPLO).

Population:	Healthy client-owned dogs with a median age of 3 (range 1–8 years), weighing 37 ± 11 kg, undergoing elective unilateral TPLO surgery.
Sample size:	20 dogs.
Intervention details:	Random allocation equally to one of two intervention groups: EPID group (n = 9, with 1 dog excluded due to failed EPID). Combined femoral and sciatic nerve block (F+S) group (n = 10). Anaesthesia and medication administration: All dogs received an NSAID (carprofen 2 mg/kg orally (PO) or 4 mg/kg subcutaneously (SC), deracoxib 2 mg/kg PO, or firocoxib 5 mg/kg PO) within 12 hours before anaesthesia. Premedication with acepromazine (0.02 mg/kg intramuscularly (IM) and hydromorphone (0.1 mg/kg IM) 30 minutes before anaesthesia induction with intravenous (IV) propofol, followed by maintenance with isoflurane in oxygen. Administration of respective treatment groups immediately before surgery: EPID: bupivacaine (0.5%, 0.5 mg/kg) + morphine (0.1%, 0.1 mg/kg in 0.2 mL/kg) F+S guided by electrolocation: bupivacaine (0.5%, 0.1 mL/kg) at each site. Intraoperative cardiovascular management: Dogs received dopamine infusion (5 μg/kg/minute IV) if they experienced hypotension despite a low end-tidal isoflurane concentration (FE'ISO) of 0.5%. Hydromorphone (0.05 mg/kg IV) was administered when hypertension or tachycardia persisted despite FE'ISO being 1.8%. Postoperative pain management: Hydromorphone (0.05 mg/kg IV) was given as rescue analgesia when dogs scored >5 on the Numerical Rating Scale (NRS). Statistical analysis used: Normality tested with Shapiro–Wilk test. Parametric data analysed with two-sample t-test. Non-parametric continuous data were analysed with the Wilcoxon rank-sum test, and categorical data with Fisher’s exact test.
Study design:	Prospective, blinded, randomised, controlled, clinical trial.
Outcome Studied:	Intraoperative assessments: Heart rate (HR), mean arterial pressure (MAP), FE’ISO, hypotension incidence, and dopamine use collected at 15-minute intervals to evaluate cardiovascular performance and intraoperative pain. Postoperative pain: Assessed using NRS with descriptions of their behaviour preoperatively (baseline), at extubation, and at 1, 4, and every 4 hours up to 24 hours postoperation. Recorded rescue analgesia requirements (administered based on specified pain scores) postoperatively at extubation and at intervals over a 24-hour period. Postoperative residual block: Assessed by time to first urination, urinary retention, and ambulation (walking 10 meters with an abdominal sling).
Main Findings (relevant to PICO question):	One dog in the EPID group was excluded from the study due to technique failure. Intraoperative assessments: EPID had a MAP of 74 ± 7, significantly lower than the F+S group with a MAP of 82 ± 11 (P = 0.04). EPID group had a significantly lower FE′ISO (0.9 ± 0.2) compared to the F+S group (1.1 ± 0.2) (P = 0.05). EPID had a lower HR (64 ± 14) compared to F+S (70 ± 11), but no significant difference was found (P = 0.26). The incidence of hypotension was similar in both groups, with 2 incidences each (P = 0.09). 6/9 dogs in the EPID group received dopamine, which was higher compared to the F+S group, where only 4/10 dogs received dopamine. However, this difference was not statistically significant (P = 0.24). Postoperative pain scores: Both groups had a baseline pain score of 2. At extubation, both groups scored 0, with pain scores increasing over time, reaching 4 in the EPID group and 3 in the F+S group by 24 hours postextubation; no significant differences were observed between the groups at any time point (p-value not reported). Requirement for rescue analgesia: At extubation, 2/9 dogs in the EPID group required hydromorphone, whereas none in the F+S group did (P = 0.21). In the F+S group, the first doses were administered to 2 dogs 4 hours later. 2/9 dogs in the EPID group and 3/10 dogs in the F+S group did not require hydromorphone, with no significant difference (P = 0.33). By 24 hours postanaesthesia recovery, the F+S group required significantly less overall use of rescue analgesia compared to the EPID group (0.05 mg/kg for F+S vs. 0.08 mg/kg for EPID; P = 0.04). Incidence of urinary retention: After surgery, 4/9 dogs in the EPID group developed urinary retention, whereas none in the F+S group were affected (P = 0.03). Time to first ambulation: The EPID group ambulated in about 8.3 hours postextubation, while the F+S group took approximately 8.7 hours postextubation, with no significant differences (P = 0.95). Both groups ambulated around 12 hours after the block, also showing no significant differences (P = 0.95).
Limitations:	Sample size was not calculated, posing a risk of type 2 error due to potentially small sample size. Lack of standardisation in severity and duration of original stifle joint lesions, as well as prior treatments with anti-inflammatory and analgesic drugs. Lack of specification regarding the veterinary surgeons' experience, the surgical approach to stifle joint inspection, or whether joint inspection was performed, potentially confounding the study results. The use of electrolocation for F+S, which is considered less precise and associated with greater tissue damage and longer procedure times compared to ultrasound. NSAIDs and premedications, known for their analgesic and sedative effects, alongside the addition of morphine to bupivacaine in EPID, may have influenced both the analgesic outcomes and the incidence of residual blocks, potentially confounding the study results. Use of a non-validated physiological tool for assessing intraoperative pain. Intraoperative data recorded every 15 minutes might have led to missed significant findings in pain assessment. Did not assess proprioceptive function, which is another important indicator of motor impairment. Incomplete reporting of exact p-values in some instances.