Effects of intravenous dexmedetomidine infusion on local anaesthetic block: A spinal anaesthesia clinical model in dogs undergoing hind limb surgery

Multiple uses of dexmedetomidine in small animals: a mini review

Dexmedetomidine is an alpha-2 adrenergic agonist, which use had an exponential increase in human and veterinary medicine in the last 10 years. The aim of this mini review is to summarize the various uses of dexmedetomidine underlining its new applications and capabilities in the small animals' clinical activity. While this drug was born as sedative in veterinary medicine, some studies demonstrated to be effective as an analgesic both in single administration and in continuous infusion. Recent studies have also shown the role of dexmedetomidine as an adjuvant during locoregional anesthesia, increasing the duration of the sensitive block and consequently decreasing the demand for systemic analgesics. The various analgesic properties make dexmedetomidine an interesting drug for opioid-free analgesia. Some studies highlighted a potential neuroprotective, cardioprotective and vasculoprotective role of dexmedetomidine, thus conferring it a place in critical care medicine, such as trauma and septic patients. Dexmedetomidine has demonstrated to be a multitasking molecule and it is ready to face new challenges.

Evaluation of a constant rate intravenous infusion of dexmedetomidine on the duration of a femoral and sciatic nerve block using lidocaine in dogs

Objectives

This study investigated the effects of 1 μg/kg/h intravenous constant rate infusion (CRI) of dexmedetomidine on the sensory and motor blockade for femoral and sciatic nerve blocks in dogs undergoing stifle surgery.

Materials and methods

Client-owned dogs referred for stifle surgery were enrolled in this prospective, randomized, blinded study. Dogs were pre-medicated with acepromazine (0.005-0.01 mg/kg intramuscularly, IM); anesthesia was induced with propofol intravenously and maintained with isoflurane in a mixture of air and oxygen. Electrolocation-guided sciatic and femoral nerve blocks with lidocaine 2% (0.15 mL/kg) were performed using the parasacral and lateral pre-iliac approaches, respectively. After performing local block, a systemic infusion of saline solution (group C) or dexmedetomidine (group D) was started at a CRI at 1 ml/kg/h and continued until the end of surgery. Dexmedetomidine was infused at a dose of 1 μg/kg/h. Respiratory and hemodynamic variables were recorded during surgery. Sensory and motor blockade was evaluated by response to pinching the skin innervated by the sciatic/femoral nerves, with forceps and by observing the dogs' ability to walk and testing proprioception at 30, 60, 120, 180, and 240 min after extubation. Analgesia was monitored with SF-GCPS. Methadone IM was administered as rescue analgesia. Intraoperative data were analyzed by analysis of variance, while postoperative data were analyzed by the independent two-tailed t-test and a Kaplan-Meier test (p < 0.05).

Results

Twenty dogs were included in this study (10/group). A significant difference in the recovery of sensory nerve function was observed between the groups. The mean durations of the sensory blockade for femoral and sciatic nerves, respectively, was longer (p < 0.001) for group D [168 (146-191, 95% CI), 161 (143-179, 95% CI) min] than in group C [120 (96.1-144, 95% CI), 116 (90.9-142, 95% CI]. No differences in the recovery of patellar and tibial reflexes, proprioceptive function, and ability to walk were found among groups. The overall postoperative rescue analgesia requirement was significantly different (p = 0.019) between groups, with an incidence of 5/10 (50%) dogs in group D and 10/10 (100%) dogs in group C.

Conclusion

Dexmedetomidine administered as a CRI (1 μg/kg/h) combined with local lidocaine increases the duration of the sensory component of the sciatic and femoral nerve blocks and reduces the requirement for additional analgesia during the immediate postoperative hours.

Thoracic epidural anaesthesia vs intrathecal morphine in dogs undergoing major thoracic and abdominal surgery: clinical study

BACKGROUND

There is scant clinical research on neuraxial analgesia in dogs undergoing major surgery. With this study we compared the perioperative analgesic effects of thoracic epidural anaesthesia (TEA) and intrathecal morphine (ITM) in dogs scheduled for thoracic or cranial abdominal surgery. The dogs received methadone and dexmedetomidine, were anaesthetized with propofol maintained with sevoflurane, and randomly assigned to receive either TEA (ropivacaine 0.5% at 0.2 mg/kg and morphine 0.1 mg/kg administered at T₁₂-T₁₃) or ITM (morphine 30 μg/kg administered at L₆-L₇). Intraoperative rescue analgesia (iRA) was fentanyl 1 μg/kg administered if heart rate or mean arterial pressure increased by 30% above the pre-stimulation level. Glasgow Pain Composite Scale score (GPCS) dictated the use of postoperative rescue analgesia (pRA) with methadone 0.2 mg/kg.

RESULTS

There was a statistically significant difference in iRA, median time to first fentanyl bolus, median fentanyl dose after surgical opening, and median GPCS score at 30 minutes (min), 1 ,2, 4, 6, and 8 hours (h) between the two groups (p<0.001; p<0.001; p<0.001; p<0.01; p<0.01; p<0.001; p<0.01; p=0.01; p=0.01, respectively). Fewer TEA than ITM group dogs required iRA during surgical opening and pRA: 5% (1/18) and 2/18 (11%), respectively, in the TEA and 83% (16/18) and 10/18 (55%), respectively, in the ITM group. Side effects were urinary retention in 3/18 (16%) TEA group dogs and 2/18 (11%) ITM group dogs and prolonged sedation in 2/18 (11%) in ITM group dogs. TEA and ITM were effective in managing perioperative pain in dogs undergoing thoracic or cranial abdominal surgery.

Cardiopulmonary Effects and Pharmacokinetics of Dexmedetomidine Used as an Adjunctive Analgesic to Regional Anesthesia of the Oral Cavity with Levobupivacaine in Dogs

This study investigated the cardiopulmonary effects and pharmacokinetics of dexmedetomidine (DEX) used as an adjunctive analgesic for regional anesthesia of the oral cavity with levobupivacaine in anesthetized dogs. Forty dogs were randomly assigned to four groups of 10 dogs. All dogs received levobupivacaine (4 blocks) with DEX IO (infraorbital block, n = 10) or IA (inferior alveolar block, n = 10) or placebo (PLC; n = 10) or DEX (n = 10) was injected intravenously (IV) after administration of levobupivacaine. The dose of DEX was always 0.5 µg/kg. Cardiopulmonary parameters were recorded, and blood was drawn for the quantification of DEX in plasma using LC-MS/MS. Heart rate was lower in all LB + DEX groups, while mean arterial pressure (MAP) was higher in the LB + DEX IV and LB + DEX IA groups compared to the LB + PLC IV group. Compared to DEX IV, IO and IA administration resulted in lower MAP up to 2 min after application. Absorption of DEX was faster at IO administration (Cmax and Tmax were 0.47 ± 0.08 ng/mL and 7.22 ± 1.28 min and 0.76 ± 0.09 ng/mL and 7.50 ± 1.63 min for the IO and IA block, respectively). The IA administration resulted in better bioavailability and faster elimination (t1/2 was 63.44 ± 24.15 min and 23.78 ± 3.78 min for the IO and IA block, respectively). Perineural administration of DEX may be preferable because of the less pronounced cardiovascular response compared to IV administration.

Application of Different Doses of Dexmedetomidine Combined with General Anesthesia in Anesthesia of Patients with Traumatic Tibiofibular Fractures and Its Effect on the Incidence of Adverse Reactions

Objective

To explore the application of different doses of dexmedetomidine combined with general anesthesia in patients with traumatic tibiofibular fractures.

Methods

A total of 120 patients with traumatic tibiofibular fractures treated in our hospital (January 2018–January 2021) were selected as the research subjects and equally grouped into group A, group B, group C, and group D according to the dosage of dexmedetomidine. Group B, group C, and group D were pumped with 0.3 μg/kg, 0.5 μg/kg, and 0.8 μg/kg load doses of dexmedetomidine before anesthesia induction, with the same doses for maintenance during surgery. Group A was intravenously pumped with the same amount of normal saline and received tracheal intubation after anesthesia induction, with propofol and remifentanil to maintain general anesthesia during surgery.

Results

No notable differences in general data were observed among the groups (P > 0.05). Ramsay sedation scores of all groups showed a downward trend after drug withdrawal. At 10 min, 30 min, and 60 min, the scores of groups C and D were markedly higher than those of groups A and B (P < 0.05), and the scores were higher in group D than those in group C (P < 0.05). The HR changes at each period were close between groups A and B (P > 0.05). The HRs at T1 and T2 in group C were slightly lower than those in group D (P > 0.05), and the HRs at T1 in groups A and B were remarkably higher than those in groups C and D, and were higher than those at T0 and T2 (P < 0.05). The SBP levels of all groups began to rise at T0, peaked at T1, and decreased to a lower level at T2 than that at T0. Moreover, the SBP levels of groups C and D at T1 and T2 were notably lower compared with groups A and B (P < 0.05). With a lower DBP level in group C than the other three groups at T1, the DBP levels were notably lower in groups C and D than those in groups A and B at T2 (P < 0.05). With no statistical difference in the MAP levels at T0 among the four groups (P > 0.05), the MAP levels in group A at T1 and T2 were obviously higher compared with groups C and D (P < 0.05). The extubation time in group A was notably longer than that that in groups B, C, and D (P < 0.05), with longer extubation time in group B than that in groups C and D (P < 0.05). The orientation recovery time in group D was markedly shorter than that in groups A, B, and C (P < 0.05). The incidence of cognitive dysfunction, chills, and restlessness in groups C and D was notably lower compared with groups A and B (P < 0.05), with a higher incidence of chills, intraoperative hypotension, and delayed awakening in group D than in group C (P < 0.05).

Conclusion

Dexmedetomidine at doses of 0.5 μg/kg and 0.8 μg/kg has a better effect in the maintenance of general anesthesia for patients with traumatic tibiofibular fractures, with faster orientation recovery, better recovery of postoperative cognitive function, and a lower incidence of adverse reactions. Dexmedetomidine at 0.5 μg/kg is recommended in view of the increased risk of excessive sedation, chills, restlessness, and intraoperative hypotension in patients at 0.8 μg/kg.

Clinical efficacy of dexmedetomidine combined with lidocaine for femoral and sciatic nerve blocks in dogs undergoing stifle surgery

OBJECTIVE

To evaluate the effects of dexmedetomidine administered perineurally or intramuscularly (IM) on sensory, motor function and postoperative analgesia produced by lidocaine for sciatic and femoral nerve blocks in dogs undergoing unilateral tibial tuberosity advancement surgery.

STUDY DESIGN

Prospective, blinded, clinical study.

ANIMALS

A group of 30 dogs.

METHODS

Dogs were anaesthetized with acepromazine, propofol and isoflurane in oxygen/air. Electrolocation-guided femoral and sciatic nerve blocks were performed: group L, 0.15 mL kg^-1 2% lidocaine (n = 10); group LD_loc, lidocaine and 0.15 μg kg^-1 dexmedetomidine perineurally (n = 10); group LD_sys, lidocaine and 0.3 μg kg^-1 dexmedetomidine IM (n = 10). After anaesthesia, sensory blockade was evaluated by response to forceps pinch on skin innervated by the saphenous/femoral, common fibular and tibial nerves. Motor blockade was evaluated by observing the ability to walk and proprioception. Analgesia was monitored with Short Form of Glasgow Composite Pain Scale for up to 4 hours after extubation. Methadone IM was administered as rescue analgesia. Data were analysed by linear mixed effect models and Kaplan-Meier test (p < 0.05).

RESULTS

Median duration of the sensory blockade for all nerves was longer (p < 0.001) for group LD_loc than for groups L and LD_sys and was longer (p = 0.0011) for group LD_sys than for group L. Proprioception returned later (p < 0.001) for group LD_loc [285 (221-328) minutes] compared with group L [160 (134-179) minutes] or LD_sys [195 (162-257) minutes]. Return of the ability to walk was similar among all groups. Dogs in group LD_loc required postoperative rescue analgesia later (p = 0.001) than dogs in groups LD_sys and L.

CONCLUSIONS AND CLINICAL RELEVANCE

Dexmedetomidine administered perineurally with lidocaine prolonged sensory blockade and analgesia during the immediate postoperative period. Systemic dexmedetomidine also prolonged the sensory blockade of perineural lidocaine.