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Feasibility of an electric current stimulator device to assess the sensory response after transversus abdominis plane block in Guinea pigs (Cavia porcellus)
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Background
In medicine, the transversus abdominis plane (TAP) block has been shown as an effective method of analgesia in several surgical procedures. In this context, this prospective, randomized, blinded study aimed to evaluate the analgesic efficacy of TAP block, guided by ultrasound in female dogs submitted to ovariectomy.
Methods
Therefore, 32 animals randomly assigned in two groups (n = 16) were used. Groups consisted of TAP block control (TBC) which received water injection (0.2 ml kg⁻¹ point), and TAP block bupivacaine (TBB) which received bupivacaine (0.2 ml kg⁻¹ point at 0.25%); both groups were submitted to four-point approach. Animals were pre-medicated with acepromazine (0.03 mg kg⁻¹) and meperidine (2 mg kg⁻¹) IM, propofol was used as anesthetic induction (3–5 mg kg⁻¹) IV, and isoflurane was used to maintain. To standardize groups, the animals received a continuous infusion of remifentanil (0.2μg kg⁻¹ min) and rocuronium (0.6 mg kg⁻¹) IV in the intraoperative period. Variables measured were the heart and respiratory rates, blood pressure, temperature, peripheral oxyhemoglobin saturation, exhaled carbon dioxide concentration, exhaled isoflurane concentration, serum cortisol, analgesia, and sedation. Before the pre-anesthetic medication (Baseline) and 1, 2, 4, 6, and 8 h after extubation, pain and sedation were assessed using a numeric rating scale (NRS), Glasgow composite measure pain scale (GCMPS-SF), and sedation scale. Moreover, serum cortisol was measured at different moments.
Results
The results show that in the intraoperative period, there was no significant difference between groups. After surgery, in TBC, 13 out of 16 animals required analgesic rescue, whereas, in TBB, this occurred only in one animal. Regarding the measurement of serum cortisol, the TBC group showed a significant difference when compared to the baseline time in the traction of the first ovary (p < 0.0001), 2 h (p = 0.0441), and 8 h (p = 0.0384) after extubation. In TBB, cortisol showed a significant increase only in the traction of the first ovary and 2 h after extubation (p < 0.0001).
Conclusion
The technique using ultrasound-guided TAP block in two points approach by hemiabdomen with 0.2 ml kg⁻¹ bupivacaine 0.25% was effective in providing post-operative analgesia in dogs undergoing ovariectomy.
Guinea pigs (Cavia porcellus) are a frequently used species in research, often involving potentially painful procedures. Therefore, evidence-based recommendations regarding analgesia are critically needed to optimize their wellbeing. Our laboratory examined the efficacy of carprofen and extended-release (ER) buprenorphine, alone and as a multimodal combination, for relieving postsurgical pain in guinea pigs. Animals were assessed by using evoked (mechanical hypersensitivity), nonevoked (video ethogram, cageside ethogram, time-to-consumption test), and clinical (weight loss) measurements for 96 h during baseline, anesthesia-analgesia, and hysterectomy conditions. In addition, ER buprenorphine was evaluated pharmacologically. Guinea pigs treated with a single analgesic showed increased mechanical sensitivity for at least 96 h and indices of pain according to the video ethogram for as long as 8 h, compared with levels recorded during anesthesia-analgesia. In contrast, animals given both analgesics demonstrated increased mechanical sensitivity and behavioral evidence of pain for only 2 h after surgery compared with anesthesia-analgesia. The cageside ethogram and time-to-consumption tests failed to identify differences between conditions or treatment groups, highlighting the difficulty of identifying pain in guinea pigs without remote observation. Guinea pigs treated with multimodal analgesia or ER buprenorphine lost at least 10% of their baseline weights, whereas weight loss in carprofen animals was significantly lower (3%). Plasma levels for ER buprenorphine exceeded 0.9 ng/mL from 8 to 96 h after injection. Of the 3 analgesia regimens evaluated, multimodal analgesia provided the most effective pain control in guinea pigs. However the weight loss in the ER buprenorphine-treated animals may need to be considered during analgesia selection.
The primary aim of this report is to assist scientists in selecting more reliable/suitable identification (ID) methods for their studies. This is especially true for genetically altered (GA) animals where individual identification is strictly necessary to link samples, research design and genotype. The aim of this Federation of European Laboratory Animal Science Associations working group was to provide an update of the methods used to identify rodents in different situations and to assess their implications for animal welfare. ID procedures are an indispensable prerequisite for conducting good science but the degree of invasiveness differs between the different methods; therefore, one needs to make a good ethical evaluation of the method chosen. Based on the scientific literature the advantages and disadvantages of various methods have been presented comprehensively and this report is intended as a practical guide for researchers. New upcoming methods have been included next to the traditional techniques. Ideally, an ID method should provide reliable identification, be technically easy to apply and not inflict adverse effects on animals while taking into account the type of research. There is no gold standard method because each situation is unique; however, more studies are needed to better evaluate ID systems and the desirable introduction of new and modern approaches will need to be assessed by detailed scientific evaluation.
Objectives:
This randomised, prospective, masked clinical trial evaluated the postoperative analgesic efficacy of an ultrasound-guided transversus abdominis plane block (TAPB) with bupivacaine in cats undergoing ovariohysterectomy.
Methods:
Thirty-two healthy adult female cats undergoing elective ovariohysterectomy were randomised to undergo TAPB with bupivacaine (treatment group [TG], n = 16) vs placebo (control group [CG], n = 16) in addition to preoperative analgesia with buprenorphine (0.02 mg/kg IM). All patients received a general anaesthetic and, before surgical incision, a bilateral two-point (subcostal and lateral-longitudinal) TAPB was performed using 1 ml/kg bupivacaine 0.25% (0.25 ml/kg/point) or saline. Each cat was assessed by a blinded investigator before premedication (0 h) and at 1, 2, 3, 4, 8, 10 and 24 h postoperatively using the UNESP-Botucatu Feline Pain Scale - short form. Buprenorphine (0.02 mg/kg IV) and meloxicam (0.2 mg/kg SC) were administered when pain scores were ⩾4/12. Ten hours postoperatively, meloxicam was administered to cats that did not receive rescue analgesia. Statistical analysis included Student's t-tests, Wilcoxon tests and χ2 tests, and a linear mixed model with Bonferroni corrections (P <0.05).
Results:
Of the 32 cats enrolled, three in the CG were excluded from the analysis. The prevalence of rescue analgesia was significantly higher in the CG (n = 13/13) than in the TG (n = 3/16; P <0.001). Only one cat in the CG required rescue analgesia twice. Pain scores were significantly higher in the CG compared with the TG at 2, 4 and 8 h postoperatively. Mean ± SD pain scores were significantly higher in the CG, but not in the TG, at 2 (2.1 ± 1.9), 3 (1.9 ± 1.6), 4 (3.0 ± 1.4) and 8 h postoperatively (4.7 ± 0.6) than at 0 h (0.1 ± 0.3).
Conclusions and relevance:
A bilateral ultrasound-guided two-point TAPB with bupivacaine in combination with systemic buprenorphine provided superior postoperative analgesia than buprenorphine alone in cats undergoing ovariohysterectomy.
Evaluation of the response to externally applied physical stimuli, such as pressure, heat, or cold is termed quantitative sensory testing (QST). QST may be used to identify and quantify alterations (gain or loss) in function of the sensory systems which detect and mediate these phenomena in both man and animals, and potentially discriminate peripheral and central sensitisation. It has been postulated that evaluation of QST parameters may predict response to analgesics, ultimately increasing the individualisation of treatment for pain. However, while there do appear to be correlations between QST measures and responses to analgesics in man, there is currently insufficient evidence to recommend QST to direct clinical treatments. The use of psychophysical testing, such as QST, in non-verbal subjects presents additional challenges, and requires familiarity with species and individual responses. This narrative review describes the investigations into QST in clinical populations of dogs to date, and discusses the potential benefits and limitations of such testing.
Veterinary regional anesthesia (RA) has been rapidly increasing in popularity over the last 10 years, as evidenced by the increasing amount of literature available and the continuous development of new techniques in small animals. The introduction of new technologies such as nerve stimulation and ultrasound (which increased the objectivity and precision of the procedure) and the promising beneficial perioperative effects conferred by RA are encouraging clinicians to incorporate these techniques in their daily perioperative anesthetic and analgesic animal care. However, there is a lack of consensus regarding outcomes when RA is used, as well as outcome comparisons between regional anesthetic techniques. Further large-scale clinical studies are still necessary. This article is the first part of a two-part review of RA in small animals, and its aim is to discuss the most relevant studies in the veterinary literature, where objective methods of nerve location have been used, and to illustrate in pictures the currently used techniques for providing RA to the thoracic limb and the thorax in small animals.
Increasing interest in using peripheral nerve blocks in small animals is evident, given the numerous studies published recently on this topic in important veterinary journals. Initially, research was focused on intraoperative analgesia to the pelvic limb, and several descriptions of lumbosacral plexus, femoral and sciatic nerve blocks have been described in studies. There is recent interest in developing techniques for somatosensory blockade of the abdominal wall. This article is the second part of a two-part review of regional anesthesia (RA) in small animals, and its aim is to discuss the most relevant studies in the veterinary literature, where objective methods of nerve location have been used, and to illustrate in pictures the currently used techniques for providing RA to the abdominal wall and the pelvic limb in small animals.
Guinea pigs (Cavia porcellus) are a frequently used species in research, often involving potentially painful procedures.Therefore, evidence-based recommendations regarding analgesia are critically needed to optimize their wellbeing. Ourlaboratory examined the efficacy of carprofen and extended-release (ER) buprenorphine, alone and as a multimodal combination,for relieving postsurgical pain in guinea pigs. Animals were assessed by using evoked (mechanical hypersensitivity),nonevoked (video ethogram, cageside ethogram, time-to-consumption test), and clinical (weight loss) measurements for 96 h during baseline, anesthesia-analgesia, and hysterectomy conditions. In addition, ER buprenorphine was evaluated pharmacologically. Guinea pigs treated with a single analgesic showed increased mechanical sensitivity for at least 96 h and indices of pain according to the video ethogram for as long as 8 h, compared with levels recorded during anesthesia-analgesia. In contrast, animals given both analgesics demonstrated increased mechanical sensitivity and behavioral evidence of pain for only 2 h after surgery compared with anesthesia-analgesia. The cageside ethogram and time-to-consumption tests failed to identify differences between conditions or treatment groups, highlighting the difficulty of identifying pain in guinea pigs without remote observation. Guinea pigs treated with multimodal analgesia or ER buprenorphine lost at least 10% of their baseline weights, whereas weight loss in carprofen animals was significantly lower (3%). Plasma levels for ER buprenorphine exceeded 0.9 ng/mL from 8 to 96 h after injection. Of the 3 analgesia regimens evaluated, multimodal analgesia provided the most effective pain control in guinea pigs. However the weight loss in the ER buprenorphine-treated animals may need to be considered during analgesia selection.
The local anaesthestic properties of 1-propyl-2',6'-pipecoloxylidide, a congener of mepivacaine and bupivacaine, and its enantiomers were compared in animals. The (S)-enantiomer (ropivacaine, LEA 103) produced a longer duration of sciatic nerve block and infiltration anaesthesia than the racemate and the (R)-form. Ropivacaine and bupivacaine were equally potent in terms of block of evoked action potential in vitro and minimum effective concentration in vivo. Ropivacaine 0.25-1.0% was distinctly longer acting than bupivacaine on infiltration, equally effective in sciatic and brachial plexus block and somewhat shorter lasting in epidural and spinal blockade. There were tendencies towards a greater benefit from the addition of adrenaline with ropivacaine in epidural anaesthesia and a shorter latency to block in some of the tests. Ropivacaine seems less vasodilative than bupivacaine and capable of producing some vasoconstriction over a wider range of low concentrations, which may explain its longer duration of intradermal anaesthesia. The somewhat shorter duration of central blockade of ropivacaine is probably a result of lesser lipid solubility. Ropivacaine was less toxic (i.v. and s.c. LD50-values) than bupivacaine but more toxic than lidocaine, and produced only weak local irritation. Due to a combination of interesting local anaesthetic properties and relative safety including cardiotoxic potential, we consider ropivacaine a candidate for further studies.
We describe a mouse model for evaluation of skin anesthesia after infiltration of local anesthetic. The method involves subcutaneous injection of the anesthetic over the abdomen, and monitoring the vocalization response to electrical stimulus as a measure of analgesia. Prior to drug injection, the vocalization threshold was determined. Mice that vocalized at < or = 8 mA were included in the study. The model was tested using representative agents of the two classes of local anesthetics, bupivacaine, an amide, and chloroprocaine, an ester. The time course and dose response were assessed after injection. The median analgesic time was 15, 40, and 55 min for 0.015%, 0.0625%, and 0.25% bupivacaine and 30, 50, and 55 min for 0.125%, 0.25%, and 2.0% chloroprocaine, respectively. Statistical analysis of the data showed that this method is sufficiently sensitive to detect differences between the dose and duration of local anesthesia (p<0.05, by log rank test of the survival curves). To further validate the model, we compared the duration of anesthesia between the 0.5% bupivacaine and a new long-acting liposomal formulation of 2% bupivacaine. The results showed that the new formulation significantly prolonged the duration of anesthesia (p<0.05). This simple and reliable method may facilitate research on the pharmacology of infiltration anesthesia and the development of new local anesthetics and/or formulations.
AVMA guidelines for the euthanasia of animals: 2020 edition
- S Leary
- W Underwood
- R Anthony