Pharmacokinetics of Bupivacaine Following Administration by an Ultrasound-Guided Transversus Abdominis Plane Block in Cats Undergoing Ovariohysterectomy

A Survey Study on the Current Veterinary Practice and Attitudes to Anaesthesia and Analgesia for Spay Surgery in the United Kingdom

BACKGROUND

In the United Kingdom, spay surgery is routinely performed in dogs and cats by general practitioners. Data from a decade ago showed that, despite an increased attentiveness of veterinarians to peri-operative pain compared to the past, analgesia could be further improved.

OBJECTIVES

To investigate the current veterinary practice and attitude towards anaesthesia and analgesia for spay surgery in the United Kingdom.

METHODS

An electronic questionnaire composed of 57 questions organised in 6 sections was designed using the Checklist for Reporting Results of Internet E-Surveys (CHERRIES guidelines) and distributed online via a hyperlink. Participants were recruited through both personalised email invitation and publication of the hyperlink on social media. Data were analysed with descriptive statistics, analysis of means and analysis of proportions, using commercially available software.

RESULTS

Entries from 150 participants were used for data analysis. The proportion of participants who were confident in treating pain did differ by decade of graduation, with a lower proportion of confident colleagues graduated before 2001 (6%) and from 2021 (14%), compared to those graduated in the decades 2001-2010 (43%) and 2011-2020 (37%) (p = 0.007). Colleagues reported to implement multimodal analgesia for spay procedures of cats and dogs in 43% and 44% of cases, respectively. The proportions of participants who reportedly used locoregional blocks, mostly with lidocaine, in dogs (82%), were higher than that in cats (43%) (p < 0.001). Post-spay surgery pain was perceived by the participants as more intense in dogs than in cats (p < 0.001).

CONCLUSIONS

Despite an overall good level of attentiveness of British veterinary professionals to feline and canine analgesia during and following spay surgery, this study identified as areas of improvements perception and assessment of feline pain and implementation of locoregional anaesthetic techniques, particularly in cats.

Perioperative analgesic management using bilateral ultrasound-guided lateral quadratus lumborum block in a dog with extrahepatic biliary obstruction

Extrahepatic bile-duct obstruction is commonly caused by pancreatitis in canines. Surgical decompression of the biliary tree is required when medical management is unsuccessful. The clinical presentation often includes severe vomiting and abdominal pain requiring targeted analgesic and anesthetic protocols. Locoregional anesthesia has been largely advocated as part of multimodal analgesic plans to reduce opioid consumption and decrease opioid-related side effects. This report describes a case where the lateral quadratus lumborum block provided effective analgesia and opioid-sparing effect in a 7-year-old mixed-breed dog with extrahepatic bile-duct obstruction undergoing common bile-duct stent placement. Key clinical message: Anesthetic stability in critically ill patients undergoing abdominal surgery is challenging. However, implementation of an ultrasound-guided locoregional technique may help blunt the sympathetic response to surgery and reduce opioid requirements, facilitating anesthetic stability and a comfortable early postoperative period. This is apparently the first report on using ultrasound-guided quadratus lumborum block in a critically ill dog with pancreatitis.

Description and Evaluation of Dye and Contrast Media Distribution of Ultrasound-Guided Rectus Sheath Block in Cat Cadavers

The rectus sheath block is an ultrasound-guided anaesthetic technique which aims to provide analgesia to the abdominal midline. This study aimed to assess the distribution of 0.4 mL kg-1 of a mixture of methylene blue and iopromide injected into each hemiabdomen in the internal rectus sheath in cat cadavers. We hypothesise that this technique would be feasible and would cover the rami ventrales of the last thoracic and the first lumbar spinal nerves. The study was divided into two phases. Phase 1 aimed to study the anatomical structures of the ventral abdominal wall (four cats were dissected). Phase 2 (ten cadavers) consisted of an ultrasound-guided injection of the mixture mentioned above and the assessment of its distribution by computed tomography and anatomical dissection. The results showed the staining of the cranioventral abdominal wall with a craniocaudal spread of four (three to eight) vertebral bodies. Methylene blue stained three (one to four) rami ventrales, affecting T10 (60%), T11 (100%), T12 (90%), T13 (50%) and L1 (5%). Based on these results, it could be stated that this technique could supply anaesthesia to the midline of the abdominal midline cranial to the umbilicus in clinical patients, but it may not be able to provide anaesthesia to the middle and caudal midline abdominal region.

Sevoflurane reduces the cardiac toxicity of bupivacaine compared with propofol in rabbits: an experimental study using early electrocardiographic detection and measurement of toxic plasma concentration

BACKGROUND

The effect of both propofol and sevoflurane on bupivacaine cardiac toxi-city has not been conclusively defined. The goal of this study was to investigate the effects of propofol vs sevoflurane general anesthesia (GA) on bupivacaine-induced arrhyth-mias.

MATERIAL AND METHODS

Ten rabbits were randomized to two groups: propofol- or sevoflurane-based GA. At the maintenance stage of anesthesia heart rate and QRS/QT durations were recorded as "baseline" and an intravenous (i.v.) bupivacaine 0.25% infusion at the rate of 1.0 mg kg -1 min -1 was initiated. Blood samples were obtained when predefined electrocardiographic (ECG) changes were observed and when the heart rate (HR) reached 75%, 50%, and 25% of the baseline and 0 bpm.

RESULTS

The mean time to first predefined ECG changes was 131 ± 25.02 s for the propofol group and 223 ± 34.11 s for the sevoflurane group ( P = 0.001). Time of progression of bradycardia in both groups was evaluated as a percentage of the initial HR for the understanding of the dynamics of changes during the local anesthetic systemic toxicity (LAST). The 25% HR time was shorter for the propofol group (480 ± 117 vs. 673 ± 146 s, P = 0.05). Time to asystole was shorter in the propofol group (110.7 ± 22.22 vs. 226.6 ± 98.61 s, P = 0.047). Mean serum bupivacaine concentration was lower for the propofol group during the occurrence of the first ECG changes (2.542 ± 1.415 vs. 6.997 ± 2.197 mg mL -1 , P = 0.005) and asystole (110.7 ± 22.22 vs. 226.6 ± 98.61 mg mL -1 , P = 0.047).

CONCLUSIONS

It seems that sevoflurane-, but not propofol-based anesthesia reduces the risk of LAST during GA combined with peripheral nerve blocks. Sevoflurane-based anesthesia may protect the myocardium from the toxic effects of bupivacaine.

Analgesic efficacy of an ultrasound-guided transversus abdominis plane block with bupivacaine in cats: a randomised, prospective, masked, placebo-controlled clinical trial

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.

The pharmacokinetics of levobupivacaine 0.5% after infraorbital or inferior alveolar block in anesthetized dogs

Introduction

Data are lacking on the pharmacokinetic profile and safety of levobupivacaine (LB) used for regional anesthesia of the maxilla and mandibles in dogs.

Methods

Infraorbital block (n = 10), inferior alveolar block (n = 10) or both infraorbital and inferior alveolar blocks (n = 10) were administered to dogs undergoing dental surgery under isoflurane anesthesia. The dose of LB was calculated as 0.11 ml/kg^2/3 for the infraorbital block and 0.18 ml/kg^2/3 for the inferior alveolar block. Blood samples were collected before and immediately after administration of the oral blocks, and 3, 4, 7, 12, 17, 32, 47, 62, 92, and 122 min thereafter. Quantification of LB in plasma was performed by LC-MS/MS.

Results and discussion

The results are presented as median and interquartile range. In dogs in which all four quadrants of the oral cavity were desensitized with LB, the C _max was 1,335 (1,030-1,929) ng/ml, the T _max was 7 (4-9.5) min, and the AUC_{(0 → 120)} was 57,976 (44,954-96,224) ng min/ml. Plasma concentrations of LB were several times lower than the reported toxic concentrations, and no signs of cardiovascular depression or neurotoxicity were observed in any of the dogs, suggesting that the occurrence of severe adverse effects after administration of LB at the doses used in this study is unlikely.

An Anatomical, Sonographic, and Computed Tomography Study of the Transversus Abdominis Plane Block in Cat Cadavers

This study compared the distribution of a bupivacaine-iopamidol-dye solution following ultrasound-guided in-plane TAP injection using a 1-point (TAP-L) or 2-point (TAP-SL) approach in cat cadavers. Two cadavers were used to study the TAP sonoanatomy while eight cadavers were enrolled in a randomized, prospective, blinded investigation. Each cat randomly received a TAP-L with 0.5 mL/kg in one hemiabdomen and a TAP-SL with 0.25 mL/kg/point in the contralateral hemiabdomen. After injection, computed tomography and dissection were performed to assess contrast distribution and number of stained target nerves. TAP-SL resulted in a wider contrast spread (mm) compared with TAP-L (87 ± 7 versus 71 ± 9; p = 0.002). The prevalence of nerve staining was higher using TAP-SL than TAP-L (p = 0.001). The ventral branches of T10, T11, T12, T13, L1 and L2 were stained in 2/8, 2/8, 5/8, 7/8, 4/8 and 1/8, and in 7/8, 7/8, 8/8, 8/8, 8/8 and 1/8 using TAP-L and TAP-SL approaches, respectively. Computed tomography and dissection identified minimal injectate intraperitoneally or within the falciform ligament fat following 1 TAP-L and 2 TAP-SL. Ultrasound-guided TAP-SL provided better injectate distribution around the thoracolumbar spinal nerve branches than TAP-L.