Use of noninvasive dental dolorimetry to evaluate analgesic effects of intravenous and intrathecal administration of morphine in anesthetized dogs

Early Analgesic Efficacy of Morphine, Butorphanol, Lidocaine, Bupivacaine or Carprofen After Periodontal Treatment in Dogs

The early effectiveness of 5 analgesics was investigated after periodontal treatment. Dogs were assigned to 6 groups (n = 14 each). A prospective, randomized and blinded clinical study was performed. Before anesthesia was induced, butorphanol, morphine, carprofen and saline were administered. After induction, a maxillary and mandibular block was performed with lidocaine or bupivacaine. Painful periodontal therapies were performed. Two hours after the administration of analgesics and after anesthesia reversal, pain was scored using the Visual Analog Scale for pain (VAS) and the modified University of Melbourne Pain Score (UMPS). Blood glucose and cortisol levels were measured prior to analgesic administration and again 2 hours later. Rescue analgesia was provided when the VAS exceeded 50 mm or the UMPS exceeded 14 points. Rescue analgesia was required in one patient in the morphine group and one in the carprofen group. The VAS values were significantly lower in the butorphanol group compared to those of the saline group and in the bupivacaine group vs. those in the saline and lidocaine groups. Significantly lower UMPS values were obtained in the bupivacaine group compared to those in the saline, butorphanol and lidocaine groups and in the carprofen group vs. those in the saline and lidocaine groups. Significantly higher serum cortisol values were found in the lidocaine group compared to those in the saline, bupivacaine and carprofen groups. Administration of carprofen or the use of nerve blocks with bupivacaine improved analgesia after periodontal treatment more than did butorphanol, morphine or nerve blocks using lidocaine.

Effects of Buprenorphine Added to Bupivacaine Infraorbital Nerve Blocks on Isoflurane Minimum Alveolar Concentration Using a Model for Acute Dental/Oral Surgical Pain in Dogs

Bupivacaine appears to have a duration of action longer than previously reported. Results of this study demonstrate that the addition of buprenorphrine may enhance the analgesic duration of effect for bupivacaine regional nerve blocks. In addition, the use of bupivacaine alone may have analgesia that exceeds 24 hours in many cases. Although not statistically significant based on sample size, 50% of dogs receiving the bupivacaine/buprenorphine regional anesthetic block demonstrated a decreased anesthetic requirement 48 hours postadministration when compared to 25% of dogs receiving the bupivacaine anesthetic. No adverse cardiorespiratory effects were noted secondary to either local anesthetic treatment. Use of bupivacaine may have analgesic effects extending greater than 24 hours (24-72) when used in regional anesthetic blocks in veterinary dental patients with acute dental pain. The addition of buprenorphine to bupivacaine may extend the duration of analgesia (48-96 h). The limited sample size, in addition to patient variability in response to medications, may account for the fact that no differences were detected between the treatments administered.

Early pain management after periodontal treatment in dogs – comparison of single and combined analgesic protocols

The aim of this study was to assess the analgesic effectiveness of three analgesic protocols in dogs undergoing a periodontal treatment. The study was performed as a prospective, randomized, “double blind” clinical study. A total of 45 client-owned dogs scheduled for periodontal treatment were included. Dogs of Group C received carprofen (4 mg·kg-1), dogs of Group B received bupivacaine (1 mg·kg-1) and dogs of Group CB received a combination of carprofen (4 mg·kg-1) and bupivacaine (1 mg·kg-1). Carprofen was administered subcutaneously 30 min before anaesthesia, bupivacaine was administered by nerve blocks in anaesthetized dogs. Painful periodontal treatment was performed in all patients, lasting up to one hour. Modified University of Melbourne Pain Score (UMPS), Visual Analogue Scale for pain assessment (VAS), plasma glucose and serum cortisol levels were assessed 30 min before administration of analgesics (C-0, B-0, CB‑0) and 2 h after recovery from anaesthesia (C-2, B-2, CB-2). For statistical analysis Friedman test, Mann-Whitney U-test, ANOVA and Fischer exact tests were used (P < 0.05). In CB‑2 compared to CB‑0 significantly decreased modified UMPS values. In CB‑2 UMPS values were significantly lower compared to C‑2 or B‑2. In C‑2 VAS values were significantly increased compared to C‑0, and in B‑2 VAS values were significantly increased compared to B‑0. Visual Analogue Scale values were significantly lower in CB‑2 compared to C‑2 or B‑2. Significantly increased plasma glucose concentrations were found in C‑2 compared to C‑0 and in B‑2 compared to B‑0. No other significant differences were detected. Administration of carprofen, bupivacaine or their combination is sufficient for early postoperative analgesia following periodontal treatment. Carprofen-bupivacaine combination is superior to carprofen or bupivacaine administered separately.

Determination of the minimum alveolar concentration of isoflurane in Shetland ponies using constant current or constant voltage electrical stimulation

OBJECTIVE

To determine the minimum alveolar concentration (MAC) of isoflurane in Shetland ponies using a sequence of three different supramaximal noxious stimulations at each tested concentration of isoflurane rather than a single stimulation.

STUDY DESIGN

Prospective, experimental trial.

ANIMALS

Seven 4-year-old, gelding Shetland ponies.

METHODS

The MAC of isoflurane was determined for each pony. Three different modes of electrical stimulation were applied consecutively (2 minute intervals): two using constant voltage (90 V) on the gingiva via needle- (CVneedle) or surface-electrodes (CVsurface) and one using constant current (CC; 40 mA) via surface electrodes applied to the skin over the digital nerve. The ability to clearly interpret the responses as positive, the latency of the evoked responses and the inter-electrode resistance were recorded for each stimulus.

RESULTS

Individual isoflurane MAC (%) values ranged from 0.60 to 1.17 with a mean (+/-SD) of 0.97 (+/-0.17). The responses were more clearly interpreted with CC, but did not reach statistical significance. The CVsurface mode produced responses with a longer delay. The CVneedle mode was accompanied by variable inter-electrode resistances resulting in uncontrolled stimulus intensity. At 0.9 MAC, the third stimulation induced more positive responses than the first stimulation, independent of the mode of stimulation used.

CONCLUSIONS

The MAC of isoflurane in the Shetland ponies was lower than expected with considerable variability among individuals. Constant current surface electrode stimulations were the most repeatable. A summation over the sequence of three supramaximal stimulations was observed around 0.9 MAC.

CLINICAL RELEVANCE

The possibility that Shetland ponies require less isoflurane than horses needs further investigation. Constant current surface-electrode stimulations were the most repeatable. Repetitive supramaximal stimuli may have evoked movements at isoflurane concentrations that provide immobility when single supramaximal stimulation was applied.

Quantitative assessment of nociceptive processes in conscious dogs by use of the nociceptive withdrawal reflex

OBJECTIVE

To investigate the feasibility of evoking the nociceptive withdrawal reflex (NWR) from fore and hind limbs in conscious dogs, score stimulus-associated behavioral responses, and assess the canine NWR response to suprathreshold stimulations.

ANIMALS

8 adult Beagles.

PROCEDURE

Surface electromyograms evoked by transcutaneous electrical stimulation of ulnaris and digital plantar nerves were recorded from the deltoideus, cleidobrachialis, biceps femoris, and tibialis cranialis muscles. Train-of-five pulses (stimulus(train)) were used; reflex threshold (I(t train)) was determined, and recruitment curves were obtained at 1.2, 1.5, and 2 x I(t train). Additionally, a single pulse (stimulus(single)) was given at 1, 1.2, 1.5, 2, and 3 x I(t train). Latency and amplitude of NWRs were analyzed. Severity of behavioral reactions was subjectively scored.

RESULTS

Fore- and hind limb I(t train) values (median; 25% to 75% interquartile range) were 2.5 mA (2.0 to 3.6 mA) and 2.1 mA (1.7 to 2.9 mA), respectively. At I(t train), NWR latencies in the deltoideus, cleidobrachialis, biceps femoris, and cranial tibialis muscles were not significantly different (19.6 milliseconds [17.1 to 20.5 milliseconds], 19.5 milliseconds [18.1 to 20.7 milliseconds], 20.5 milliseconds [14.7 to 26.4 milliseconds], and 24.4 milliseconds [17.1 to 40.5 milliseconds], respectively). Latencies obtained with stimulus(train) and stimulus(single) were similar. With increasing stimulation intensities, NWR amplitude increased and correlated positively with behavioral scores.

CONCLUSIONS AND CLINICAL RELEVANCE

In dogs, the NWR can be evoked from limbs and correlates with behavioral reactions. Results suggest that NWR evaluation may enable quantification of nociceptive system excitability and efficacy of analgesics in individual dogs.

Assessment of a von Frey device for evaluation of the antinociceptive effects of morphine and its application in pharmacodynamic modeling of morphine in dogs

OBJECTIVE

To assess the use of a von Frey device as a mechanical nociceptive stimulus for evaluation of the antinociceptive effects of morphine in dogs and its potential application in the pharmacodynamic modeling of morphine in that species.

ANIMALS

6 healthy Beagles.

PROCEDURE

von Frey thresholds were measured in all dogs before and at intervals after they received no treatment (control dogs) and i.v. administration of morphine sulfate (1 mg/kg; treated dogs) in a crossover study. The von Frey device consisted of a rigid tip (0.5 mm in diameter) and an electronic load cell; the operator was unaware of recorded measurements.

RESULTS

Application of the von Frey device was simple and well tolerated by all dogs and caused no apparent tissue damage. No significant changes in thresholds were detected in the control dogs at 8 hourly measurements, indicating a lack of acquired tolerance, learned aversion, or local hyperalgesia. When assessed as a group, treated dogs had significantly high thresholds for 4 hours following morphine administration, compared with baseline values; individually, thresholds decreased to baseline values within (mean +/- SE) 2.8 +/- 0.6 hours. The maximal effect (change from baseline values) was 213 +/- 43%, and the plasma morphine concentration to achieve 50% maximal effect was 13.92 +/- 2.39 ng/mL.

CONCLUSIONS AND CLINICAL RELEVANCE

Data suggest that, in dogs, evaluation of the antinociceptive effect and pharmacodynamic modeling of a dose of morphine sulfate (1 mg/kg, i.v.) can be successfully achieved by use of a von Frey device.

β-Phenylethylamines and the isoquinoline alkaloids

This review covers beta-phenylethylamines and isoquinoline alkaloids derived from them, including further products of oxidation. condensation with formaldehyde and rearrangement, some of which do not contain an isoquinoline system, together with naphthylisoquinoline alkaloids, which have a different biogenetic origin. The occurrence of the alkaloids, with the structures of new bases, together with their reactions, syntheses and biological activities are reported. The literature from July 2002 to June 2003 is reviewed, with 568 references cited.

Endogenous opiates and behavior: 2002

This paper is the twenty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2002 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Effect of intrathecal and intravenous administration of oxytocin on amplitude of the reflex-evoked muscle action potential after electrical stimulation of the tooth pulp in anesthetized dogs

OBJECTIVE

To determine whether intrathecal (IT) or IV administration of oxytocin will diminish amplitude of the reflex-evoked muscle action potential (REMP) in the digastricus muscle during electrical stimulation of the tooth pulp in anesthetized dogs, thus suggesting an analgesic effect for oxytocin.

ANIMALS

6 male Beagles that were 2 to 6 years old.

PROCEDURE

Dogs were used in a crossover design with at least a 5-day washout period between treatments. Each dog received morphine, saline (0.9% NaCl) solution, and oxytocin by both the IT and IV routes of administration. Noninvasive dental dolorimetry was used to assess changes in pain threshold following administration of treatments. Effectiveness of analgesia was determined on the basis of change in REMP amplitude in the digastricus muscle.

RESULTS

Morphine administered IV significantly inhibited REMP amplitude, compared with IV administration of saline solution or oxytocin. There was not a significant change in REMP amplitude between saline solution and oxytocin administered IV. Intrathecal administration of morphine significantly inhibited REMP amplitude, compared with IT administration of saline solution or oxytocin. Intrathecal administration of oxytocin significantly increased REMP amplitude, compared with IT administration of saline solution or morphine.

CONCLUSIONS AND CLINICAL RELEVANCE

Although IV administration of oxytocin did not have an effect on REMP amplitude, compared with IV administration of saline solution, IT administration of oxytocin had the opposite effect of morphine and increased REMP amplitude of the digastricus muscle. These data do not support the use of oxytocin as an analgesic agent in dogs.