Feline perioperative pain management

Dental Pain in Cats: A Prospective 6-Month Study

Dental pathology is among the most ubiquitous diseases in cats of all ages. Dental pain is yet to be fully understood in cats and therefore its presence is often missed. To better understand feline dental disease as a pain trigger during routine examination and whether disease severity correlates to the degree of pain, a 6-month prospective study in a cats’ only veterinary hospital in Portugal was conducted. Sixty-four cats that randomly presented for different clinical procedures were evaluated. Dental and periodontal abnormalities (primary dental parameters, PDP), as well as clinical signs related to dental pain (secondary dental parameters, SDP), were assessed. All cats underwent an oral cavity examination, upon which, the Feline Acute Pain Scale from Colorado State University Veterinary Teaching Hospital (CPS), was used in order to assess pain. Six PDP (periodontal disease, gingival index, calculus index, tooth resorption, tooth fracture and missing teeth) and five SDP (mouth discomfort, halitosis, hypersalivation, difficulty in holding food and several attempts at prehension of food), were compared with CPS pain scores. All SDP were significantly associated to higher CPS pain scores (p < 0.05). The number of missing teeth was significantly associated to higher CPS pain scores (p < 0.0001). A trend was observed between higher CPS pain scores and tooth resorption (p = 0.08). This study concluded that cats with dental disease feel pain during clinical examination and the pain increases as the severity of the disease progresses.

Nonsurgical management of traumatic pneumoperitoneum in a cat

OBJECTIVE

To describe the nonsurgical management of a cat with traumatic pneumoperitoneum.

CASE SERIES SUMMARY

A 4-year-old cat was presented following vehicular polytrauma. Thoracic radiographs revealed 4 rib fractures, a scapular fracture, and pneumothorax. Abdominal ultrasound revealed a small volume of free abdominal fluid. Computed tomography showed a mild pneumoretroperitoneum and a pneumoperitoneum in the region of the porta hepatis. The cat was managed conservatively with close monitoring. Exploratory laparotomy was not pursued given patient stability and static serial imaging studies revealing no indications for surgical intervention. After 6 days, the pneumoperitoneum was no longer detectable.

NEW OR UNIQUE INFORMATION PROVIDED

To the authors' knowledge, this is the first report of successful nonsurgical management of traumatic pneumoperitoneum in a cat.

Postoperative pain control in cats: clinical trials with pre-emptive lidocaine epidural co-administered with morphine or methadone

Objectives The aim of the study was to evaluate the effectiveness of epidural lidocaine in combination with either methadone or morphine for postoperative analgesia in cats undergoing ovariohysterectomy. Methods Under general anesthesia, 24 cats that underwent ovariohysterectomy were randomly allocated into three treatment groups of eight each. Treatment 1 included 2% lidocaine (4.0 mg/kg); treatment 2 included lidocaine and methadone (4.0 mg/kg and 0.3 mg/kg, respectively); and treatment 3 included lidocaine and morphine (4.0 mg/kg and 0.1 mg/kg, respectively). All drugs were injected in a total volume of 0.25 ml/kg via the lumbosacral route in all cats. During the anesthetic and surgical periods, the physiologic variables (respiratory and heart rate, arterial blood pressure and rectal temperature) were measured at intervals of time zero, 10 mins, 20 mins, 30 mins, 60 mins and 120 mins. After cats had recovered from anesthesia, a multidimensional composite pain scale was used to assess postoperative analgesia 2, 4, 8, 12, 18 and 24 h after epidural. Results The time to first rescue analgesic was significantly ( P <0.05) prolonged in cats that received both lidocaine and methadone or lidocaine and morphine treatments compared with those that received lidocaine treatment alone. All cats that received lidocaine treatment alone required rescue analgesic within 2 h of epidural injections. All treatments produced significant cardiovascular and respiratory changes but they were within an acceptable range for healthy animals during the surgical period. Conclusions and relevance The two combinations administered via epidural allowed ovariohysterectomy with sufficient analgesia in cats, and both induced prolonged postoperative analgesia.

Effect of pretreatment with hydromorphone or buprenorphine on thermal antinociception induced by fentanyl in awake cats

OBJECTIVES

The aim of this study was to determine the effect of pretreatment with hydromorphone or buprenorphine on thermal antinociception induced by fentanyl in cats.

METHODS

Seven healthy cats received five different treatments consisting of two drugs. Drug 1 was administered intravenously 1 h before drug 2. Drug 2 was given as an intravenous loading dose followed by an infusion for 4 h. The drug combinations used were: buprenorphine 20 µg/kg followed by fentanyl (BF; 7 μg/kg, 7 μg/kg/h), buprenorphine 20 µg/kg followed by 0.9% saline solution (B), hydromorphone 0.07 mg/kg followed by 0.9% saline solution (H), hydromorphone 0.07 mg/kg followed by fentanyl (HF; 7 μg/kg, 7 μg/kg/h) and 0.9% saline solution followed by fentanyl (F; 7 μg/kg, 7 μg/kg/h). Thermal thresholds were obtained prior to treatment and at predetermined times up to 7 h after drug 1.

RESULTS

Thermal thresholds were significantly higher than baseline in all treatment groups as follows: H from 0.25 to 2.50 h; B from 0.25 to 2.50 h; F from 1.25 to 5.50 h; HF from 0.25 to 5.50 h and BF from 0.25 to 5.25 h. Thermal thresholds were significantly higher in HF and BF than in F treatment before the fentanyl infusion was commenced (from 0.25 to 1.00 h). During the fentanyl infusion thermal thresholds in BF compared with F were lower at 1.75 h and from 2.50 to 3.50 h. After the constant rate infusion of fentanyl was started, thermal thresholds were significantly lower in HF compared with F at one time point (3 h).

CONCLUSIONS AND RELEVANCE

Pretreatment with buprenorphine did partially inhibit the antinociceptive action of fentanyl. Hydromorphone did inhibit the antinociceptive action of fentanyl at one single time point in cats.

Systematic review of the behavioural assessment of pain in cats

OBJECTIVES

The objectives were to review systematically the range of assessment tools used in cats to detect the behavioural expression of pain and the evidence of their quality; and to examine behavioural metrics (considering both the sensory and affective domains) used to assess pain.

METHODS

A search of PubMed and ScienceDirect, alongside articles known to the authors, from 2000 onwards, for papers in English was performed. This was followed by a manual search of the references within the primary data sources. Only peer-reviewed publications that provided information on the assessment tool used to evaluate the behavioural expression of pain in cats, in conscious animals (not anaesthetised cats), were included.

RESULTS

No previous systematic reviews were identified. One hundred papers were included in the final assessment. Studies were primarily related to the assessment of pain in relation to surgical procedures, and no clear distinction was made concerning the onset of acute and chronic pain. Ten broad types of instrument to assess pain were identified, and generally the quality of evidence to support the use of the various instruments was poor. Only one specific instrument (UNESP-Botucatu scale) had published evidence of validity, reliability and sensitivity at the level of a randomised control trial, but with a positive rather than placebo control, and limited to its use in the ovariohysterectomy situation. The metrics used within the tools appeared to focus primarily on the sensory aspect of pain, with no study clearly discriminating between the sensory and affective components of pain.

CONCLUSIONS AND RELEVANCE

Further studies are required to provide a higher quality of evidence for methods used to assess pain in cats. Furthermore, a consistent definition for acute and chronic pain is needed. Tools need to be validated that can detect pain in a range of conditions and by different evaluators (veterinary surgeons and owners), which consider both the sensory and emotional aspects of pain.

Prepubertal gonadectomy in cats: different injectable anaesthetic combinations and comparison with gonadectomy at traditional age

Anaesthetic and analgesic effects of three different injectable anaesthetic combinations for prepubertal gonadectomy (PPG) in cats were studied. One anaesthetic protocol was compared with a similar one for gonadectomy at traditional age (TAG). Kittens were randomly assigned to PPG or TAG. For PPG, three different protocols were compared: (1) intramuscular (IM) administration of 60 μg/kg dexmedetomidine plus 20 μg/kg buprenorphine followed by an IM injection of the anaesthetic agent (20 mg/kg ketamine) (DB-IM protocol); (2) oral transmucosal (OTM) administration of 80 μg/kg dexmedetomidine plus 20 μg/kg buprenorphine followed by an IM injection of 20 mg/kg ketamine combined with 20 µg/kg dexmedetomidine (DB-OTM protocol); (3) IM injection of a 40 μg/kg medetomidine-20 μg/kg buprenorphine-20 mg/kg ketamine combination (MBK-IM protocol). For TAG, a DB-IM protocol was used, but with different doses for dexmedetomidine (40 μg/kg) and ketamine (5 mg/kg). All cats (PPG and TAG) received a non-steroidal anti-inflammatory before surgery. Anaesthetic and analgesic effects were assessed pre- and postoperatively (until 6 h). Cumulative logit, linear and logistic regression models were used for statistical analysis. Compared with the DB-OTM protocol, the DB-IM and MBK-IM protocols provided better anaesthesia with fewer adverse effects in PPG cats. Postoperative pain was not significantly different between anaesthetic protocols. PPG and TAG cats anaesthetised with the two DB-IM protocols differed significantly only for sedation and pain scores, but sedation and pain scores were generally low. Although there were no anaesthesia-related mortalities in the present study and all anaesthetic protocols for PPG in cats provided a surgical plane of anaesthesia and analgesia up to 6 h postoperatively, our findings were in favour of the intramuscular (DB-IM and MBK-IM) protocols.

Analgesia in the Perioperative Period

Untreated or undermanaged perioperative pain has systemic effects that may negatively impact a patient's welfare and return to function. A consistent analgesic plan that assesses a patient's pain and comfort at regular intervals during the perioperative period should be incorporated into practice. Validated pain assessment tools are available for use in dogs and cats. Multimodal analgesic plans should be created for individual patients and modified according to pain assessments. These plans, based on a thorough history, physical examination, and knowledge of the expected pain, should be combinations of an opioid, a nonsteroidal anti-inflammatory drug, a local anesthetic, and nonpharmacologic analgesic techniques.

Effects of surgical wound infiltration with bupivacaine on postoperative analgesia in cats undergoing bilateral mastectomy

The analgesic effect of wound infiltration with bupivacaine was evaluated in cats undergoing bilateral mastectomy. Twenty-one female cats with mammary gland tumors were anesthetized with propofol and oxygen-isoflurane anesthesia following premedication with atropine. In the trial group (Group I; n=11), 30 ml of saline containing 2 mg/kg of bupivacaine was infiltrated topically into the surgical wound right after removal of the mammary glands, whereas only saline solution was infiltrated in the control group (Group II; n=10). At the same time, carprofen (4 mg/kg) was also administered subcutaneously in both groups. Behavioral signs of pain were monitored during the recovery period after general anesthesia. In order to examine the behavioral changes associated with acute pain, a questionnaire was prepared and given to the owners to be completed 4 hr and then 10 hr after the operation. According to the owners' anwers to the questionnaire, a pain score was specified using a "numerical rating scale" for each cat. Although some cats showed mild to moderate pain, the pain score recorded at 4 hr after the operation was significantly lower in Group I (P<0.001). No significant difference was found at 10 hr after the operation between the groups. The incidence of vocalization, aggression and convulsion within 2 hr after the operation was also lower in Group I. In conclusion, wound infiltration with bupivacaine before incisional closure provided reliable analgesia at least 4 hr after bilateral radical mastectomy in cats.

Evaluation of inflammatory and hemostatic surgical stress responses in male cats after castration under general anesthesia with or without local anesthesia

OBJECTIVE

To characterize acute inflammatory and hemostatic surgical stress responses following castration in cats and to evaluate whether the addition of local anesthesia to the anesthetic protocol attenuates these responses.

ANIMALS

39 male cats.

PROCEDURES

Cats undergoing castration were randomly assigned to 2 groups: both groups underwent surgery with general anesthesia, and 1 group additionally received a local anesthetic (lidocaine [2.0 mg/kg in total, divided intratesticularly and SC]) prior to incision. Blood samples were collected after anesthetic induction (baseline) and 1, 5, and 24 hours later. Thromboelastography and coagulation variables (activated partial thromboplastin time [aPTT] and prothrombin time [PT]) were analyzed; fibrinolysis was assessed with plasma D-dimer concentrations. The acute-phase response was evaluated via measurement of plasma fibrinogen and serum amyloid A (last time point, 28 hours) concentrations. Hematologic variables were analyzed at baseline and 1, 5, and 24 hours later.

RESULTS

Evidence of hemostatic and inflammatory activation after surgery was detected in both groups. Maximum amplitude and G (global clot strength) were significantly increased at 24 hours, and significant, but not clinically relevant, decreases were detected in aPTT at 5 and 24 hours and in PT at 24 hours, compared with baseline values. Serum amyloid A concentrations were significantly higher at 24 and 28 hours than at baseline, and plasma fibrinogen concentration was significantly increased at 24 hours; WBC and RBC counts and Hct were significantly increased at multiple time points. No differences between groups were detected for any variables.

CONCLUSIONS AND CLINICAL RELEVANCE

Castration appeared to induce hypercoagulability and an acute-phase inflammatory response in cats. Local anesthesia with lidocaine did not attenuate this response.

Analgesic efficacy of perioperative use of vedaprofen, tramadol or their combination in cats undergoing ovariohysterectomy

The analgesic efficacy of tramadol and/or vedaprofen was evaluated in cats submitted for elective ovariohysterectomy, using a randomised double blind placebo controlled design. Forty adult female cats (3.0+/-0.32kg; 1.8+/-0.7 years) were distributed into four groups. Vedaprofen PO (0.5mg/kg), tramadol SC (2mg/kg), both, or placebo was administered 1h before surgery and every 24 and 8h, respectively, for 72h after surgery. Pain score evaluated by interactive visual analogue and composite pain score and hyperalgesia by the von Frey filament test were recorded at 1, 2, 4, 6, 8, 12, 24, 28, 32, 48, 52, 56, 72, 96h and on the 7th day after surgery. Animals treated with combined vedaprofen and tramadol treatment did not need rescue analgesia, did not develop hyperalgesia, and their serum cortisol concentrations and pain scores were lower than placebo until 24 and 72h after surgery, respectively. Combined vedaprofen and tramadol treatment provided more effective postoperative analgesia and prevented hyperalgesia than when used on their own. Multimodal technique is a superior method of treating pain after feline ovariohysterectomy. This work also provides evidence for the benefits of analgesia for up to 3 days following ovariohysterectomy.

Antinociceptive and side-effects of hydromorphone after subcutaneous administration in cats

The subcutaneous (SC) route is often chosen for drug administration in cats because it is easier to perform than intravenous (IV) injection and is perceived as less painful than intramuscular (IM) injection. However, little is known of how the route of administration influences the pharmacodynamics of drugs. This study measured the changes in skin temperature and thermal threshold (TT) and recorded the side-effects after SC injection of 0.1mg/kg of hydromorphone in six cats. Time to peak TT was 105min. Skin temperature was elevated at 15min and between 45 and 360min. Five cats vomited and two exhibited marked dysphoria. Compared to previously published studies of IV and IM administration of hydromorphone, the SC route results in a slower onset of peak effect, a shorter duration of antinociception and is associated with more undesirable side-effects. As with IV and IM injections, SC administration of hydromorphone at 0.1mg/kg is associated with a significant elevation in skin temperature. Overall, the SC route appears to have the least utility.

Recent developments in nonsteroidal antiinflammatory drugs in cats

Pain, particularly chronic pain, is an underestimated ailment in cats. Veterinarians tend to under-diagnose and under-treat pain in this aloof and stoic species. Until recently, there was only one analgesic (i.e., butorphanol) approved in the United States for use in cats; but many analgesics, particularly opioids, have been used extra-label for this purpose. Nonsteroidal antiinflammatory drugs (NSAIDs) have been used sparingly in cats because of safety concerns, which are less of an issue with the newer agents. Meloxicam is the only NSAID labeled for use in cats in the United States, but other agents are available in this country and are labeled for use in cats in other countries.

Dose-related thermal antinociceptive effects of intravenous hydromorphone in cats

OBJECTIVE

To describe the dose-related thermal antinociceptive effects of intravenous (i.v.) hydromorphone in cats.

STUDY DESIGN

Randomized, blinded, crossover design.

ANIMALS

Seven adult cats (3.5-7.4 kg), two spayed females, and five neutered males.

METHODS

Hydromorphone (0.025, 0.05, or 0.1 mg kg(-1)) was administered i.v.. Skin temperature and thermal threshold were measured before and at selected time points to 720 minutes post-administration. Statistical analysis of mean thermal threshold and skin temperatures over time for each dose and between doses was by way of a split-plot model and post hoc Bonferroni t-tests. p < 0.05 was considered significant.

RESULTS

A significant difference from baseline for mean thermal threshold was identified for the 0.05 mg kg(-1) dose (5-80 minutes, peak thermal threshold 46.9 +/- 6.2 degrees C) and 0.1 mg kg(-1) dose (5-200 minutes, peak thermal threshold 54.9 +/-0.2 degrees C). The thermal threshold was significantly greater after the 0.1 mg kg(-1) dose from 5 to 200 minutes compared to the 0.025 mg kg(-1) and 0.5 mg kg(-1) doses. The thermal threshold was significantly greater from 35 to 80 minutes for the 0.05 mg kg(-1) dose when compared with the 0.025 mg kg(-1) dose. Skin temperature was significantly increased from 35 to 140 minutes following the 0.1 mg kg(-1) dose.

CONCLUSIONS

A dose-related antinociceptive effect was demonstrated for i.v. hydromorphone in cats.

CLINICAL RELEVANCE

Hydromorphone at doses less than 0.1 mg kg(-1) has a modest antinociceptive effect and a short duration of action. At a dose of 0.1 mg kg(-1) i.v., onset of analgesia is rapid with a clinically useful duration of effect, but is associated with a rise in skin temperature.

A comparison of four methods of analgesia in cats following ovariohysterectomy

OBJECTIVE

To evaluate the effectiveness of preoperative administration of oral carprofen, subcutaneous ketoprofen, and local nerve block with bupivacaine in preventing postoperative pain-associated behavior in cats after ovariohysterectomy.

ANIMALS

Fifty-two female intact cats. Materials and methods Cats received butorphanol (0.44 mg kg(-1) IM), carprofen (2.2 mg kg(-1) PO), ketoprofen (2.2 mg kg(-1) SQ), or bupivacaine infiltration block (1.1 mg kg(-1) SQ) before surgery. Cortisol and drug concentrations and visual analog scale (VAS) and interactive visual analog scale (IVAS) pain-associated behavior scores were measured 2 hours before and 0, 1, 2, 4, 8, 12, and 24 hours after ovariohysterectomy.

RESULTS

Cats receiving butorphanol had significantly increased IVAS scores 2 hours after surgery compared with baseline measurements. Cats receiving carprofen, ketoprofen, and bupivacaine had significant increases from baseline in VAS and IVAS scores 1 and 2 hours after surgery. VAS and IVAS scores for cats receiving bupivacaine were significantly greater 1 and 2 hours after surgery than for cats that received butorphanol. Cats receiving carprofen had significant increases in cortisol 1 hour after surgery and significant decreases 24 hours after surgery compared with baseline measurements.

CONCLUSIONS AND CLINICAL RELEVANCE

Preoperative carprofen and ketoprofen have effects on pain-associated behavior similar to butorphanol in cats undergoing ovariohysterectomy. Cats receiving bupivacaine blocks may require additional analgesics immediately after surgery.

Postanesthetic hyperthermia in cats: a retrospective comparison between hydromorphone and buprenorphine

OBJECTIVE

To determine the prevalence of postanesthetic hyperthermia [rectal temperature >40 degrees C (104 degrees F)] in a clinical population of cats.

STUDY DESIGN

Retrospective study.

ANIMAL POPULATION

One hundred and twenty-five cats with an age range of 2 months to 16.1 years, and weighing 3.9 +/- 1.5 kg.

MATERIALS AND METHODS

Data were obtained from the medical records of 125 cats that underwent general anesthesia. Information on perioperative rectal temperatures, breed, sex, weight, surgical procedure, anesthetic time, surgery time, anesthetic and analgesic drugs were retrieved.

STATISTICAL ANALYSES

Five groups of cats were compared; group 1 (n = 15) received acepromazine and no opioids; group 2 (n = 17) received acepromazine and buprenorphine; group 3 (n = 19) received acepromazine, buprenorphine and ketoprofen; group 4 (n = 45) received acepromazine and hydromorphone and group 5 (n = 29) received acepromazine, hydromorphone and ketoprofen. Data conformed to a split-plot repeated measures analysis of variance and was analyzed using SAS PROC MIXED. Post hoc tests were by means of Bonferroni t-test; < or = 0.05 was considered significant.

RESULTS

Rectal temperature was significantly decreased in all groups at the end of anesthesia. Rectal temperature was significantly elevated at 1, 1.5, 2, 3, 4 and 5 hours after the end of anesthesia in group 4, and at 2, 3 and 4 hours in group 5. Sixty-four percent of cats in group 4 and 69% in group 5 had rectal temperatures >40 degrees C (104 degrees F) at one or more times in the postanesthetic period. The highest temperature recorded was 42.5 degrees C (108.5 degrees F) in one cat in group 4. Mean rectal temperature did not exceed the preoperative temperature at any time during the postanesthetic period in group 1, 2 and 3 animals.

CONCLUSIONS

This study indicates an association between hyperthermia and perioperative administration of hydromorphone in cats.

CLINICAL RELEVANCE

When hydromorphone is used in cats their body temperature should be closely monitored.

Evaluation of signs of postoperative pain and complications after forelimb onychectomy in cats receiving buprenorphine alone or with bupivacaine administered as a four-point regional nerve block

OBJECTIVE

To evaluate signs of postoperative pain and complications after forelimb onychectomy in cats receiving buprenorphine alone or with bupivacaine administered as a 4-point regional nerve block.

DESIGN

Prospective, randomized, double-blind clinical trial.

ANIMALS

20 cats.

PROCEDURE

All cats received buprenorphine (0.01 mg/kg [0.004 mg/lb], IM) preoperatively. One forelimb of each cat also received bupivacaine (1 mg/kg [0.45 mg/lb] of a 0.75% solution) administered as a 4-point regional nerve block. After onychectomy, discomfort (lameness, foot reaction, and pain) scores were evaluated by 2 experienced observers 2, 4, 6, 8, 24, and 168 hours postoperatively. Complication (hemorrhage, swelling, and infection) scores were evaluated 24 and 168 hours postoperatively. Surgeries were performed by 1 experienced veterinary surgeon. Rescue analgesia was provided if needed.

RESULTS

6 cats required rescue analgesia postoperatively. There was no difference in discomfort or complication scores between control limbs and limbs in which a nerve block was administered. Additionally, there was no difference in discomfort and complication scores between cats that did or did not require rescue analgesia.

CONCLUSIONS AND CLINICAL RELEVANCE

Bupivacaine administered as a 4-point regional nerve block in addition to a systemic analgesic did not decrease discomfort or complication scores in cats undergoing forelimb onychectomy.

Comparison of oral and subcutaneous administration of buprenorphine and meloxicam for preemptive analgesia in cats undergoing ovariohysterectomy

OBJECTIVE

To compare the effectiveness of preoperative PO and SC administration of buprenorphine and meloxicam for prevention of postoperative pain-associated behaviors in cats undergoing ovariohysterectomy.

DESIGN

Randomized controlled study.

ANIMALS

51 female cats (4 to 60 months old; weight range, 1.41 to 4.73 kg [3.1 to 10.4 lb]).

PROCEDURE

Cats received 1 of 5 treatments at the time of anesthetic induction: buprenorphine PO (0.01 mg/kg [0.0045 mg/lb]; n = 10), buprenorphine SC (0.01 mg/kg; 10), meloxicam SC (0.3 mg/kg 10.14 mg/lb]; 10), meloxicam PO (0.3 mg/kg; 10), or 0.3 mL of sterile saline (0.9% NaCI) solution SC (control group; 11). Sedation scores and visual analog scale and interactive visual analog scale (IVAS) pain-associated behavior scores were assigned to each cat 2 hours before and at intervals until 20 hours after surgery.

RESULTS

Cats receiving meloxicam PO or SC had significantly lower IVAS scores (2.91 and 2.02, respectively), compared with IVAS scores for cats receiving buprenorphine PO (755). Pain-associated behavior scores for cats administered buprenorphine or meloxicam PO or SC preoperatively did not differ significantly from control group scores. Rescue analgesia was not required by any of the cats receiving meloxicam, whereas 3 of 10 cats receiving buprenorphine PO, 2 of 10 cats receiving buprenorphine SC, and 1 of 11 cats receiving the control treatment required rescue analgesia.

CONCLUSIONS AND CLINICAL RELEVANCE

On the basis of pain-associated behavior scores, cats receiving meloxicam PO or SC before ovariohysterectomy appeared to have less pain after surgery than those receiving buprenorphine PO preoperatively.

Rehabilitation of medical and acute care patients

Cancer and serious systemic illness result in several physiologic changes that involve multiple body systems. While the primary conditions are addressed with traditional modalities of medicine, the side effects, secondary changes, and complications can be ameliorated or even prevented with rehabilitation and supportive care. This article reviews problems facing the oncologic and critically ill animal, discusses basic techniques in the management of these animals, and highlights the essential role of rehabilitation in obtaining maximal functional capacity in the critically ill patient.

PK-PD modeling of buprenorphine in cats: intravenous and oral transmucosal administration1

The pharmacokinetics and thermal antinociceptive effects of buprenorphine after intravenous (i.v.) or oral transmucosal (OTM) administration were studied in six adult cats. Plasma buprenorphine concentrations were measured using radioimmunoassay in a crossover study after a dose of 20 microg/kg given by the i.v. or OTM route. Oral pH was measured. Blood for drug analyses was collected before, and at 1, 2, 4, 6, 10, 15, 30, and 60 min and at 2, 4, 6, 8, 12, and 24 h after treatment. Thermal thresholds were measured before treatment, then following treatment every 30 min to 6 h, every 1 hour to 12 h and at 24 hours postadministration. Plasma buprenorphine concentration effect relationships were analyzed using a log-linear effect model. Oral pH was 9 in each cat. Peak plasma buprenorphine concentration was lower and occurred later in the OTM group but median bioavailability was 116.3%. Thermal thresholds increased significantly between 30 and 360 min in both groups. Peak effect was at 90 min and there was no difference at any time between the two groups. There was distinct hysteresis between plasma drug concentration and effect in both groups. Overall, OTM administration of buprenorphine is as effective as i.v. treatment and offers a simple, noninvasive method of administration which produces thermal antinociception for up to 6 h in cats.

In vitro effects and in vivo efficacy of a novel cyclooxygenase-2 inhibitor in cats with lipopolysaccharide-induced pyrexia

OBJECTIVE

To determine cyclooxygenase (COX)-2 selectivity, pharmacokinetic properties, and in vivo efficacy of firocoxib (ML-1,785,713) in cats.

ANIMALS

5 healthy male and 14 healthy female domestic shorthair cats.

PROCEDURE

Selectivity of firocoxib for inhibiting COX-2 was determined by comparing the potency for inhibiting COX-1 with that of COX-2 in feline blood. Pharmacokinetic properties were determined after i.v. (2 mg/kg) and oral (3 mg/kg) administration in male cats. In vivo efficacy was evaluated in female cats with lipopolysaccharide (LPS)-induced pyrexia with administration of firocoxib 1 or 14 hours before LPS challenge.

RESULTS

Blood concentrations resulting in 50% inhibition of COX-1 and COX-2 activity in vitro were 75 +/- 2 microM and 0.13 +/- 0.03 microM, respectively, and selectivity for inhibiting COX-2 relative to COX-1 was 58. Firocoxib had moderate to high oral bioavailability (54% to 70%), low plasma clearance (4.7 to 5.8 mL/min/kg), and an elimination half-life of 8.7 to 12.2 hours. Firocoxib at doses from 0.75 to 3 mg/kg was efficacious in attenuating fever when administered to cats 1 or 14 hours before LPS challenge.

CONCLUSIONS AND CLINICAL RELEVANCE

Firocoxib is a potent COX-2 inhibitor and is the only selective COX-2 inhibitor described for use in cats to date. It is effective in attenuating febrile responses in cats when administered 14 hours before LPS challenge, suggesting it would be suitable for once-a-day dosing. Because selective COX-2 inhibitors have an improved therapeutic index relative to nonselective nonsteroidal anti-inflammatory drugs in humans, firocoxib has the potential to be a safe, effective anti-inflammatory agent for cats.

Effect of postoperative analgesic protocol on limb function following onychectomy in cats

OBJECTIVE

To evaluate the analgesic effects of topical administration of bupivacaine, i.m. administration of butorphanol, and transdermal administration of fentanyl in cats undergoing onychectomy.

DESIGN

Prospective study.

ANIMALS

27 healthy adult cats.

PROCEDURE

Cats were randomly assigned to 1 of 3 treatment groups, and unilateral (left forefoot) onychectomy was performed. Gait analysis was performed before and 1, 2, 3, and 12 days after surgery. All forces were expressed as a percentage of the cat's body weight.

RESULTS

On day 2, peak vertical force (PVF) was significantly decreased in cats treated with bupivacaine, compared with cats treated with butorphanol or fentanyl. The ratio of left forelimb PVF to PVF of the other 3 limbs was significantly lower on day 2 in cats treated with bupivacaine than in cats treated with fentanyl. No significant differences in vertical impulse (VI) were found between groups on any day. Values for PVF, VI, and the PVF ratio increased progressively following surgery. However, for all 3 groups, values were still significantly decreased, compared with baseline values, 12 days after surgery.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that limb function following onychectomy is significantly better in cats treated with fentanyl transdermally or butorphanol i.m. than in cats treated with bupivacaine topically. Regardless of the analgesic regimen, limb function was still significantly reduced 12 days after surgery, suggesting that long-term analgesic treatment should be considered for cats undergoing onychectomy. Irrigation of the surgical incisions with bupivacaine prior to wound closure cannot be recommended as the sole method for providing postoperative analgesia in cats undergoing onychectomy.

Managing pain in feline patients

In the past 10 years, great strides have been made in the field of feline analgesia. A better understanding of the cat's unique metabolism has led researchers to realize that extrapolation across species boundaries is unwise,and this has resulted in feline-specific studies. The opioids are now used more commonly in cats, with good analgesic effect and few side effects. Excellent acute pain management is achievable in cats by using opioids, NSAIDs, alpha2-agonists, and local anesthetics. Although much of the research data has compared the use of single drugs, a multimodal approach using agents that work at different parts of the pain pathway is commonly used in clinical settings, with added benefit. Compared with dogs, few pain-scoring systems have been developed for cats, and this remains an important goal. Management of chronic pain in cats is a challenge because of the potential problems with long-term NSAID use; however, reports of low doses given at extended intervals are encouraging. As we gain experience with less traditional analgesics, such as amitriptyline, amantadine, and gabapentin, and critically evaluate complimentary therapies, our ability to provide comfort to this population of cats will improve.

Pain management in cats--past, present and future. Part 1. The cat is unique

Cats are popular pets but until recently their perioperative and traumatic pain was seriously underestimated and under treated. There are several causes of this under treatment. First, it may be difficult to detect pain in cats, because they do not demonstrate overt pain-associated behaviour. Secondly, there are relatively few analgesic drugs with market authorization for cats. Thirdly, cats have an unfortunate reputation for toxicity from analgesic drugs, particularly opioid-induced mania and classical non steroidal anti inflammatory drug toxicity. Fourthly, cats are deficient in some metabolic pathways used to metabolise analgesic drugs in other species; this may lead to genuine toxicity or to lack of effect. Recently, understanding of feline behaviour and physiology has improved, leading to better clinical management of this enigmatic species. Behavioural methods are proving to be the best means of assessing pain, and knowledge of unique feline physiology has enabled rational treatment protocols to be developed specifically for cats.

Pain management in cats--past, present and future. Part 2. Treatment of pain--clinical pharmacology

Opioids have an unjustified reputation for causing mania in cats, but with refinements in dosing they are now used successfully in this species. The mu-opioid agonists are generally considered the best analgesics. Morphine (0.1-0.3 mg/kg) is effective in a clinical setting. Methadone (up to 0.5 mg/kg) has a similar profile to morphine. Pethidine (Demerol, meperidine; 2-5 mg/kg) is a useful analgesic with a faster onset but shorter duration of action than morphine. Oxymorphone and hydromorphone (0.05-0.1 mg/kg) are widely used in the USA. These opioids are more potent (up to 10 times), and longer acting than morphine in cats. Butorphanol (0.1-0.4 mg/kg) is a mu-opioid antagonist that produces its analgesic actions through kappa agonist activity. It rapidly reaches a ceiling effect, is short acting and is a weaker analgesic than pure mu opioids. Buprenorphine (0.01-0.02 mg/kg), a partial mu-agonist, is the most popular opioid used in small animal practice in the UK, other parts of Europe, Australia and South Africa. In clinical studies it has produced better analgesia than several other opioids and appears to be highly suitable for perioperative pain management in cats. NSAIDs are also used in cats for pain management, although cats metabolise these differently from other species. With appropriate dosing, carprofen (1-4 mg/kg) and meloxicam (0.3 mg/kg) have proved highly effective with few side effects. The use of ketoprofen (2 mg/kg), tolfenamic acid (4 mg/kg) and vedaprofen (0.5 mg/kg) has been reported in cats. Other less traditional analgesics such as ketamine, medetomidine and local anaesthetics are also used for clinical pain management. The transmucosal, transdermal and epidural routes offer novel methods for administration of analgesic drugs and have considerable potential for improving techniques in feline pain management.