Evaluation of transversus abdominis block and serratus block regional anesthesia in dogs undergoing mastectomy

Abstract

Aim of study: This study aims to evaluate the pain management in dogs affected by mammary tumors that underwent a total monolateral mastectomy procedure with a combination of ultrasound guided blocks of serratus superficial plane block and Trasversus plane block (both paracostal approach and umbelical).

Introduction: Mastectomy is considered, in dogs, the gold standard for treating mammary tumors. The surgical approach mainly depends on size of the tumor, anatomical localization and health status of the patient In dogs, algic stimulus during mastectomy is considered to be elevated because of its extension and involvement of many anatomical structures such as skin, subcutis, and sometimes also superficial muscles. Thus, if it is mandatory to reduce the dosage of anesthetics and analgesic drugs to minimize their side effects, it is also mandatory to prevent and treat pain. Loco-regional anesthesia is widely used to reduce drug doses in animals undergoing various surgical procedures. Local anesthetics have the capacity of blocking nociceptive signals of the nervous fiber and preventing central sensibilization.

Matherials and methods: 17 female dogs undergoing a monolateral total mastectomy were enrolled in this study. All patients were premedicated with methadone 0.2 mg/kg IV, induced with propofol 20 minutes after premedication, and the general anesthesia was maintained with isofluorane. Before surgery, the following three blocks were performed: serratus superficial plane block and TAP block (paracostal and umbilicus approach). Ropivacaine was diluted at 0.35% with saline solution NaCl; the volume used for the serratus was 0.3 ml/kg and for the TAP was 0.15 ml/kg in both sites. During the surgical procedure for each patient a monitoring every five minutes was made, with multiparametric intra-operative monitoring of heart rate (HR), respiratory rate (RR), partial saturation of oxygen levels, invasive systolic pressure (SAP), invasive mean pressure (MAP), invasive diastolic pressure (DAP), CO2 concentration at the end of expiration, concentration of expirated isofluorane (FeISO). Afterward, all patients underwent a multiparametric evaluation of pain via the Glasgow Composite Pain Scale (GCPS-SF: Glasgow Composite Pain Scale). every hour five times after surgery. If the total score was over 5, a rescue analgesia was administered with methadone 0.2 mg/kg IM.

Results and discussion: No significant differences were recorded in HR, MAP, SAP, DAP, and EtCO2. And 7 out of 17 cases did not require any additional analgesia during the procedure, two cases needed 3 boluses of Fentanyl at 1 mcg/kg, one case needed 2 boluses, and last but not least 7 out of 17 only one bolus. No rescue postoperative analgesia was needed.

Conclusion: In this study the combination of serratus plane block and transverse plane block was effective in blocking the nociceptive stimuli in both thoracic and abdomen wall in dogs undergoing a monolateral total mastectomy