AAFP Feline Anesthesia Guidelines.

AIM: The overarching purpose of the AAFP Anesthesia Guidelines (hereafter referred to as the 'Guidelines') is to make anesthesia and sedation safer for the feline patient. Scope and accessibility: It is noteworthy that these are the first exclusively feline anesthesia guidelines authored by an expert panel, making them particularly useful as an extensively referenced, practical resource for veterinary practice teams. Because much of the key content is presented in tabular or visual format, the Guidelines have a high level of accessibility and convenience that invites regular usage. While the recommendations in the Guidelines focus primarily on client-owned cats, the content is also applicable to community-sourced animals with an unknown medical history.

Effect of buprenorphine on the cardiovascular and respiratory response to visceral pain in conscious rabbits.

OBJECTIVE: To evaluate the effect of buprenorphine administration on the cardiovascular and respiratory responses to noxious colorectal distension in conscious rabbits. STUDY DESIGN: Prospective experimental trial. ANIMALS: Fifteen healthy, young adult New Zealand white rabbits (eight female). METHODS: Experiments were performed on conscious rabbits that were instrumented with intraabdominal arterial and venous catheters, and diaphragmatic and abdominal electromyographic electrodes. Colorectal distension was achieved by inflation of an acutely placed colorectal balloon catheter until mean arterial pressure increased 10-15 mmHg. Buprenorphine (0.06 mg) or saline was administered intravenously prior to, or during colorectal distension. Arterial blood pressure, heart rate, respiratory rate, abdominal electromyographic activity, and intra-balloon pressure were monitored. RESULTS: In the absence of colorectal distension, buprenorphine increased arterial blood pressure and decreased respiratory rate but did not change heart rate. Colorectal distension increased arterial blood pressure and heart rate, and decreased respiratory rate. The increase in arterial blood pressure associated with colorectal distension was attenuated following preemptive buprenorphine, but was not changed by buprenorphine administered during distension. CONCLUSIONS AND CLINICAL RELEVANCE: If cardiovascular changes reflect the intensity of noxious stimulation, then these results support the preemptive administration of buprenorphine for visceral analgesia.

Respiratory and cardiovascular effects of buprenorphine in conscious rabbits.

OBJECTIVE: To quantify the respiratory and cardiovascular effects of intravenous or subcutaneous buprenorphine in conscious rabbits. STUDY DESIGN: Prospective experimental trial. ANIMALS: Eight healthy, young adult New Zealand white rabbits (four female). METHODS: Rabbits were instrumented with intraabdominal arterial and venous catheters and diaphragmatic electromyographic electrodes 2 weeks before experiments. Arterial blood pressure, arterial blood gases, heart rate and respiratory rate were monitored during experiments. Buprenorphine (0.06 mg) was administered either intravenously or subcutaneously to conscious rabbits. Respiratory and cardiovascular parameters were compared to baseline at 10 and 22 minutes after intravenous buprenorphine administration, and at 30, 60, and 90 minutes after subcutaneous buprenorphine administration. RESULTS: Buprenorphine administration, at a dose of approximately 0.02 mg kg(-1), did not change blood pressure or heart rate. However, respiratory rate decreased from 252 +/- 26 to 39 +/- 26 breaths minute(-1) (mean +/- SD), and from 306 +/- 38 to 90 +/- 38 breaths minute(-1) following intravenous and subcutaneous administration of buprenorphine, respectively. Subsequent to intravenous and subcutaneous buprenorphine, arterial oxygen tension decreased from 88 +/- 4 to 72 +/- 4 mmHg (11.7 +/- 0.5 to 9.6 +/- 0.5 kPa) and from 87 +/- 3 to 77 +/- 3 mmHg (11.6 +/- 0.4 to 10.3 +/- 0.4 kPa), respectively. Buprenorphine, by either route of administration, increased arterial carbon dioxide tension from 36 to 41 mmHg (4.8-5.5 kPa) and increased the alveolar-arterial oxygen gradient from 15 to > or =20 mmHg (2 to > or =2.7 kPa). CONCLUSIONS AND CLINICAL RELEVANCE: Buprenorphine administration decreased respiratory rate and produced mild hypoxemia in conscious rabbits. While these changes were well tolerated by healthy animals, caution should be exercised when administering buprenorphine to rabbits predisposed to respiratory depression.

Visceral pain decreases tolerance to blood loss in conscious female but not male rabbits.

Pain is a component of traumatic blood loss, yet little is known about how pain alters the response to blood loss in conscious animals. We evaluated the effects of colorectal distension on the cardiorespiratory response to blood loss in six male and six female conscious, chronically instrumented New Zealand White rabbits. The goal of these experiments was to test the hypotheses that 1) colorectal distension would increase tolerance to hemorrhage (i.e., increase the blood loss required to decrease mean arterial pressure

A novel electrode design for chronic recording of electromyographic activity.

We describe a simple, self-retaining electromyography (EMG) electrode for use in chronic recording of EMG activity. The EMG electrode is helical in shape, resembling the screw-in fixation device on many cardiac pacing electrodes. Screw-like placement of the electrode secures it in the musculature without sutures. We have been using this electrode design to obtain months of quality diaphragmatic EMG recording in conscious rabbits. By changing the electrode wire size and coil dimensions, this design could be applied to chronic EMG recording in a variety of muscles and species.

Neuronal activity within the ventrolateral periaqueductal gray during simulated hemorrhage in conscious rabbits.

The ventrolateral (vl) periaqueductal gray (PAG) has been proposed as a site responsible for the active process triggering the onset of hypotension (i.e., phase 2) during blood loss in conscious animals (Cavun S and Millington WR. Am J Physiol Regul Integr Comp Physiol 281: R747-R752, 2001). We recorded the extracellular activity of PAG neurons in conscious rabbits to test the hypothesis that vlPAG neurons change their firing frequency before the onset of hypotension during simulated hemorrhage. Arterial and venous catheters, an intrathoracic vena caval occluder, and midbrain microelectrodes on a microdrive were implanted in 10 rabbits. During simulated hemorrhage, the occluder was inflated until arterial pressure < or = 40 mmHg. We compared changes in neuronal activity during simulated hemorrhage with those during a similar length control period for 64 vlPAG and 29 dorsolateral (dl) PAG neurons. Arterial pressure pulse modulation of neuronal activity was present in 45 and 76% of vlPAG and dlPAG neurons, respectively. When we evaluated the absolute change in activity, thus accounting for both increases and decreases, simulated hemorrhage had a significant effect on activity of vlPAG but not dlPAG neurons. The majority (56%) of vlPAG neurons did not appear to respond to simulated hemorrhage. Of the 28 responsive vlPAG neurons, 11 showed an abrupt change in firing frequency during the time interval preceding the onset of hypotension; 13 responded after the onset of hypotension; and 4 showed a consistent direction of change across the entire simulated hemorrhage. Thus 24 (38%) of the vlPAG neurons recorded responded at a time consistent with a contribution to the hypotension associated with simulated hemorrhage.

Intra-articular lidocaine plus bupivacaine in sheep undergoing stifle arthrotomy.

OBJECTIVE: To evaluate the effect of intra-articular (i.a.) lidocaine plus bupivacaine on post-operative pain in sheep undergoing stifle arthrotomy. STUDY DESIGN: Randomized controlled experimental trial. ANIMALS: Sixteen adult Rambouillet-cross ewes. METHODS: Sheep were randomly assigned to one of two treatment groups. The lidocaine/bupivacaine group (L/B, n=8) received i.a. lidocaine (40 mg (2 mL)) prior to incision and i.a. bupivacaine (10 mg (2 mL)) post-closure, while the control group (n=8) received no i.a. injections. i.a. local anesthetics were an addition to the standard analgesic protocol of phenylbutazone (1 g orally, every 24 hours for 5 days) and transdermal fentanyl (equivalent to 15 mg), initiated 24 hours prior to surgery. A stifle arthrotomy was performed with the purpose of creating a full-thickness articular cartilage defect. Two observers blinded to treatment assessed sheep for total pain score using a numeric ranking scale that included: comfort, movement, and flock behavior. The first observation (T=0) was obtained the evening of surgery (3-7 hours post-operatively); subsequent observations occurred every 12 hours for 72 hours. Nonparametric statistical tests were used to evaluate differences between groups for total pain score. RESULTS: L/B sheep had significantly lower total pain scores at T=0 than control sheep (p<0.05). No significant differences between treatments were noted at any subsequent time periods. There were no differences attributable to the use of different observers. CONCLUSIONS AND CLINICAL RELEVANCE: i.a. lidocaine plus bupivacaine provided analgesia at 3-7 hours post-operatively. Use of i.a. lidocaine and bupivacaine is a simple, effective, yet inexpensive perioperative analgesic protocol for joint surgery in sheep.

Use of a pulsed electromagnetic field for treatment of post-operative pain in dogs: a pilot study.

OBJECTIVE: To determine if pulsed electromagnetic field (PEMF) therapy reduces post-operative pain in dogs following ovariohysterectomy, and to evaluate PEMF interaction with post-operative morphine analgesia. STUDY DESIGN: Randomized controlled clinical trail. ANIMALS: Sixteen healthy dogs weighing 18 (10-32) kg [median (range)] and aged 13 (3-36) months. MATERIALS AND METHODS: Anesthesia consisted of atropine (0.04 mg kg-1, SC), acepromazine (0.02 mg kg-1, SC), fentanyl (0.01 mg kg-1, SC), thiopental (10-15 mg kg-1, IV) and halothane in oxygen. Ovariohysterectomies were performed by senior veterinary students. Pain score (numeric rating scale, 0-28), pulse rate, respiratory rate, indirect mean arterial pressure (MAP), and body temperature were evaluated prior to anesthetic premedication, at extubation, 30 minutes after extubation, and then hourly for 6 hours. Following extubation, dogs were randomly divided into four groups: a control group that received 0.9% NaCl, IV, and no PEMF; a magnet group that received 0.9% NaCl, IV, and PEMF; a morphine group that received morphine 0.25 mg kg-1, IV, and no PEMF; and, a magnet/morphine group that received morphine 0.25 mg kg-1, IV, and PEMF. A single observer, blinded to treatment, obtained all behavioral observations and physiologic data. Data were analyzed using the Kruskal-Wallis statistical test with a significance of p < 0.05. RESULTS: Significant differences in MAP (mm Hg) [median (range)] occurred at 300 minutes [morphine 108 (83-114) and magnet/morphine 90 (83-97) < magnet 135 (113-117)], and at 360 minutes [magnet/morphine 93 (81-100) < control 127 (111-129) and magnet 126 (111-129)]. At 30 minutes the total pain score for the magnet/morphine group [1.5 (0-5)] was significantly less than control [8 (6-13)], but not different from magnet [5.5 (4-7)] or morphine [4.5 (2-9)]. CONCLUSIONS AND CLINICAL RELEVANCE: Although no clear benefit was seen in this study, the results suggest that PEMF may augment morphine analgesia following ovariohysterectomy in dogs, and that further study of the analgesic effects of PEMF is warranted.