Thermal antinociceptive, sedative and cardiovascular effects of Governing Vessel 1 dexmedetomidine pharmacopuncture in healthy cats

Comparison of sedation with dexmedetomidine/atipamezole administered subcutaneously at GV20 acupuncture point with usual routes of administration in dogs presented for orthopaedic radiographs

OBJECTIVES

To evaluate the efficacy of subcutaneous administration of dexmedetomidine/atipamezole at the Governing Vessel 20 (GV20) acupuncture point compared with other administration routes (intramuscular and intravenous) in dogs presented for orthopaedic radiographs.

MATERIALS AND METHODS

Prospective, randomised, blinded, controlled clinical study. Sixty-four client-owned dogs were randomly injected with 200 μg/m2 of dexmedetomidine intramuscular (lumbar muscles) (n=20), intravenous (n=23) or subcutaneous at the GV20 point (n=21). Following radiographs, dogs received 2000 μg/m2 of atipamezole intramuscular (n=31), or subcutaneous at the GV20 point (n=27). Degree and time to sedation and recovery were assessed using a sedation scale and a Dynamic and Interactive Visual Analog Scale (DIVAS). Clinical physiological variables and adverse events were used. Statistical linear mixed-effect models (analysis of variance) and Cox models were performed. Significance was set at P-value <0.05.

RESULTS

Sedation was insufficient to perform orthopaedic radiographs in six dogs in the intramuscular group. The time to sedation was significantly longer, and sedation scale and DIVAS scores were significantly lower in the intramuscular group. The intravenous group had significantly higher sedation scale and DIVAS scores than the GV20 group. No significant differences were observed between the intramuscular and GV20 recovery groups, although the time effect was significantly more pronounced in the GV20 recovery group.

CLINICAL SIGNIFICANCE

Subcutaneous administration of dexmedetomidine and atipamezole at GV20 provided effective sedation and recovery in dogs undergoing orthopaedic radiographic studies. GV20 administration provided a clinically similar level of sedation to the intravenous route, and greater and faster sedation and similar recovery to intramuscular.

Use of nociceptive threshold testing in cats in experimental and clinical settings: a qualitative review

OBJECTIVE

The objective of this study was to review the scientific articles on the use of nociceptive threshold testing (NTT) in cats and to summarize the clinical and experimental applications in this species.

DATABASES USED

Pertinent literature was searched with PubMed, Scopus, Web of Science, Universitätsbibliothek Basel (swissbib Basel Bern) and Google Scholar. The search was then refined manually based first on article titles and abstracts, and subsequently on full texts.

CONCLUSIONS

Of the four classical acute nociceptive models used for NTT, thermal and mechanical are most commonly used in cats. Thermal stimulation is applicable in experimental settings and has been used in pharmacodynamics studies assessing feline antinociception. Although mechanical stimulation is currently less used in cats, in the future it might play a role in the evaluation of clinical feline pain. However, the low response reliability after stimulus repetition within a narrow time interval represents a major limitation for the clinical use of mechanical thresholds in this species. Challenges remain when thermal thresholds are used to investigate analgesics that have the potential to affect skin temperature, such as opioids and α2-adrenergic agonists, and when a model of inflammatory pain is reproduced in experimental cats with the purpose of evaluating non-steroidal anti-inflammatory drugs as analgesics.

The antinociceptive effects of intravenous administration of three doses of butorphanol tartrate or naloxone hydrochloride following hydromorphone hydrochloride to healthy conscious cats

OBJECTIVE

To evaluate thermal antinociception from intravenous (IV) administration of hydromorphone alone or followed by butorphanol or naloxone in cats.

STUDY DESIGN

Randomized, controlled, masked, crossover design.

ANIMALS

A group of eight adult female cats.

METHODS

Cats were administered six treatments of two IV injections 30 minutes apart: treatments S-S, two 0.9% saline; H-S, hydromorphone (0.1 mg kg^-1) and saline; H-LB, hydromorphone and butorphanol (0.02 mg kg^-1); H-MB, hydromorphone and butorphanol (0.1 mg kg^-1); H-HB, hydromorphone and butorphanol (0.2 mg kg^-1); H-N, hydromorphone and naloxone (0.04 mg kg^-1). Skin temperature (ST), thermal threshold (TT) and sedation score (SS) were recorded before (baseline) and for 8 hours after the first injection. Percentage maximum possible effect (%MPE), thermal excursion (TE), TT, SS and ST were compared using two-way repeated measures anova or Friedman test followed by Tukey's or Dunn's multiple comparisons test when appropriate. Significance was set at p ≤ 0.05.

RESULTS

Data from seven cats were analyzed. There were no significant differences among treatments in baseline values, SS and within S-S over time. Compared with respective 0.5 hour values following hydromorphone administration, %MPE was significantly lower at 4-8 hours for H-S; at 3-8 hours for H-LB; at 4-8 hours for H-MB; at 6-8 hours for H-HB and at 1-8 hours for H-N. Compared with respective 0.5 hour values, TE was significantly lower at 4-8 hours for H-S; at 3-8 hours for H-LB; at 2 and 4-8 hours for H-MB; at 6 and 8 hours for H-HB and at 1-8 hours for H-N.

CONCLUSIONS AND CLINICAL RELEVANCE

Butorphanol and naloxone reduced hydromorphone-induced thermal antinociception. Butorphanol preserved hydromorphone antinociceptive properties better than naloxone. Butorphanol is recommended during non-life-threatening scenarios as a partial reversal agent for hydromorphone in cats.