Quantitative sensory testing in canine musculoskeletal pain: Findings from a systematic review, meta-analysis feasibility assessment, and limitations

Quantitative sensory testing (QST) allows the study of pain mechanisms, patient phenotyping, and response to therapy. The goals of this study were to conduct a systematic review of the use of QST in dogs with musculoskeletal disease including osteoarthritis (OA), and to assess, by means of a meta-analysis, the ability of QST to differentiate affected dogs from healthy controls. The study protocol was registered; three bibliographic databases were screened. Studies involving QST in healthy dogs and those with musculoskeletal disease were included. Data were extracted using a standardized form. Assessment of quality and risk of bias were performed using the CAMARADES critical assessment tool. Twenty-nine articles met the inclusion criteria [systematic review (n = 11); meta-analysis (n = 28)]. In the systematic review, ten studies performed static QST: mechanical [punctate tactile (n = 6); mechanical pressure (n = 5)]; thermal [cold (n = 3); hot (n = 4)]; electrical (n = 1); and one study performed dynamic QST [conditioned pain modulation (n = 1)]. Most studies were of good scientific quality and showed low to moderate risk of bias. A meta-analysis was not possible due to numerous and severe issues of heterogeneity of data among studies. Methods to reduce risk of bias and use of reporting guidelines are some of the most needed improvements in QST research in dogs. Standardization of QST methodology is urgently needed in future studies to allow for data synthesis and a clear understanding of the sensory phenotype of dogs with and without chronic pain including OA.

Quantitative sensory testing in feline osteoarthritic pain - a systematic review and meta-analysis

Quantitative sensory testing (QST) is a psychophysical test used to quantify somatosensory sensation under normal or pathological conditions including osteoarthritis (OA).

OBJECTIVE

This study aimed to conduct a systematic review and meta-analysis of studies using QST in healthy and osteoarthritic cats, registered at Systematic Review Research Facility (#26-06-2017).

DESIGN

Hierarchical models with random intercepts for each individual study extracted through the systematic review were fit to subject-level data; QST measures were contrasted between healthy and osteoarthritic cats. Four bibliographic databases were searched; quality and risk of bias assessment were performed using pre-established criteria.

RESULTS

Six articles were included; most were of high quality and low risk of bias. Punctate tactile threshold (n = 70) and mechanical temporal summation (n = 35) were eligible for analysis. Cats with OA have lower punctate tactile threshold [mean difference (95%HDI): -44 (-60; -26) grams] and facilitated temporal summation of pain [hazard ratio (95%HDI): 5.32 (2.19; 14) times] when compared with healthy cats. The effect of sex and body weight on sensory sensitivity remained inconclusive throughout all analyses. Due to the correlation between age and OA status, it remains difficult to assess the effect of OA on sensory sensitivity, independently of age.

CONCLUSIONS

Clear and transparent reporting using guidelines are warranted. Similar to people, centralized sensitization is a feature of OA in cats. Future studies should try to elucidate the age effect on feline OA. Research with natural OA in cats is promising with potential to benefit feline health and welfare, and improve translatability to clinical research.

Rat cardiovascular telemetry: Marginal distribution applied to positive control drugs

Cardiovascular effects are considered frequent during drug safety testing. This investigation aimed to characterize the pharmacological response of the conscious telemetered rat in vivo model to known cardiovascular active agents. These effects were analyzed using statistical analysis and cloud representation with marginal distribution curves for the contractility index and heart rate as to assess the effect relationship between cardiac variables. Arterial blood pressure, left ventricular pressure, electrocardiogram and body temperature were monitored. The application of data cloud with marginal distribution curves to heart rate and contractility index provided an interesting tactic during the interpretation of drug-induced changes particularly during selective time resolution (i.e. marginal distribution curves restricted to Tmax). Taken together, the present data suggests that marginal distribution curves can be a valuable interpretation strategy when using the rat cardiovascular telemetry model to detect drug-induced cardiovascular effects. Marginal distribution curves could also be considered during the interpretation of other inter-dependent parameters in safety pharmacology studies.

Effects of feeding a high omega-3 fatty acids diet in dogs with naturally occurring osteoarthritis

The aim of this randomized, placebo-controlled and double-blinded trial was to compare the effect of a veterinary therapeutic diet (VTD) rich in omega-3 fatty acids (omega-3) from fish origin to a regular diet used as control (CTR) over a period of 13 weeks in dogs afflicted by naturally occurring osteoarthritis (OA). Thirty privately owned dogs were selected. Dogs had lameness confirmed by an orthopaedic examination, had stifle/hip OA and had locomotor disability based on the peak of the vertically oriented ground reaction force (PVF) measured using a force platform. At Baseline, all owners were asked to determine 2-5 activities of daily living that were the most impaired. Activities were scores (0-4) in accordance with severity using case-specific outcome measures (CSOM). The PVF was also measured. Dogs (15/group) were then randomly assigned to receive either the CTR or the VTD. The CSOM was completed twice weekly. The recording of PVF was repeated at Week 7 and 13. The VTD-fed dogs showed a significantly higher PVF at Week 7 (p < 0.001) and at Week 13 (p < 0.001) when compared to Baseline. From Baseline to Week 13, VTD-fed dogs had a mean (± SD) change in PVF recording of 3.5 ± 6.8% of body weight (%BW) compared with 0.5 ± 6.1%BW (p = 0.211) in CTR-fed dogs. This change in primary outcome was consistent with an effect size of 0.5. Conversely, dogs fed the CTR did not show significant change in PVF measurements. At the end of the study, the CSOM was significantly decreased (p = 0.047) only in VTD fed dogs. In lame OA dogs, a VTD that contains high level of omega-3 from fish origin improved the locomotor disability and the performance in activities of daily living. Such nutritional approach appears interesting for the management of OA.

Combined cardiopulmonary assessments with implantable telemetry device in conscious freely moving cynomolgus monkeys

Female cynomolgus monkeys were surgically implanted with telemetry transmitters recording ECG (DII), arterial pressure, physical activity, body temperature, and tidal volume. Respiratory rate (RR) and tidal volume (TV) were monitored simultaneously with the telemetry transmitter using impedance. Impedance-based monitoring of RR and TV by telemetry correlated with controlled TV and with pneumotachometer (>98%) in restrained animals. Control drugs with cardiovascular and respiratory effects, including saline, medetomidine (0.01, 0.02 and 0.04mg/kg) and cocaine (0.5, 1.0 and 1.5mg/kg) were administered intravenously. An averaging epoch of 5min was used for analysis of respiratory data. Medetomidine induced significant respiratory depression with decrease in RR and TV in freely moving animals while cocaine increased TV, RR and minute ventilation (MV) with concomitant increase in heart rate when compared with time matched values from saline-treated animals. The onset, duration and magnitude of cardiovascular and respiratory changes were correlated. This highlights the dependency of the cardiovascular and respiratory systems. The use of cardiopulmonary monitoring can allow continuous monitoring including during night time when variability of respiratory parameters is lower. Monitoring of cardiovascular and respiratory parameters in the same animals could also help to decrease the number of animals used in research.

Temporal assessment of bone marrow lesions on magnetic resonance imaging in a canine model of knee osteoarthritis: impact of sequence selection

OBJECTIVE

To assess the evolution of bone marrow lesions (BMLs) in a canine model of knee osteoarthritis (OA) using three different magnetic resonance imaging (MRI) sequences.

DESIGN

Three MRI sequences [coronal, T1-weighted three-dimensional fast gradient recalled echo (T1-GRE), sagittal fat-suppressed 3D spoiled gradient echo at a steady state (SPGR), and sagittal T2-weighted fast spin echo with fat saturation (T2-FS)] were performed at baseline, and at week 4, 8 and 26 in five dogs following transection of the anterior cruciate ligament. The same reader scored (0-3) subchondral BMLs twice, in blinded conditions, according to their extent in nine joint subregions, for all imaging sessions, and independently on the three MRI sequences. Correlation coefficients and Bland-Altman plots evaluated intra-reader repeatability. Readings scores were averaged and the nine subregions were summed to generate global BML scores.

RESULTS

BMLs were most prevalent in the central and medial portions of the tibial plateau. Intra-reader repeatability was good to excellent for each sequence (r(s)=0.87-0.97; P<0.001). Maximal intra-reader variability (24%) was reached on T2-FS and was associated to higher scores (P<0.05). Global BML scores increased similarly on all three sequences until week 8 (P<0.05). At week 26, score on T2-FS was decreased, being lower when compared to T1-GRE and SPGR (P<0.05).

CONCLUSION

In this canine OA model, the extent of BMLs varies in time on different MRI sequences. Until the complex nature of these lesions is fully resolved, it is suggested that to accurately assess the size and extent of BMLs, a combination of different sequences should be used.

Magnetic resonance imaging can accurately assess the long-term progression of knee structural changes in experimental dog osteoarthritis

OBJECTIVES

Osteoarthritis (OA) structural changes take place over decades in humans. MRI can provide precise and reliable information on the joint structure and changes over time. In this study, we investigated the reliability of quantitative MRI in assessing knee OA structural changes in the experimental anterior cruciate ligament (ACL) dog model of OA.

METHODS

OA was surgically induced by transection of the ACL of the right knee in five dogs. High resolution three dimensional MRI using a 1.5 T magnet was performed at baseline, 4, 8 and 26 weeks post surgery. Cartilage volume/thickness, cartilage defects, trochlear osteophyte formation and subchondral bone lesion (hypersignal) were assessed on MRI images. Animals were killed 26 weeks post surgery and macroscopic evaluation was performed.

RESULTS

There was a progressive and significant increase over time in the loss of knee cartilage volume, the cartilage defect and subchondral bone hypersignal. The trochlear osteophyte size also progressed over time. The greatest cartilage loss at 26 weeks was found on the tibial plateaus and in the medial compartment. There was a highly significant correlation between total knee cartilage volume loss or defect and subchondral bone hypersignal, and also a good correlation between the macroscopic and the MRI findings.

CONCLUSION

This study demonstrated that MRI is a useful technology to provide a non-invasive and reliable assessment of the joint structural changes during the development of OA in the ACL dog model. The combination of this OA model with MRI evaluation provides a promising tool for the evaluation of new disease-modifying osteoarthritis drugs (DMOADs).

Molecular mechanisms underlying the role of nitric oxide in the cardiovascular system

In the cardiovascular system, nitric oxide (NO) is involved in the short and long-term regulation of haemodynamics, and in a number of their pathological alterations. Investigation into the biochemistry of NO-synthase isoforms has confirmed that they also all produce superoxide anion (O(*)). The free radical NO can interact with many targets on which novel information has been recently obtained. The major results of these interactions are not only the well known activation of guanylyl cyclase, but also the formation of potentially cytotoxic peroxynitrite (ONOO(-)), and the formation of S-nitrosothiols and non-haem iron-dinitrosyl dithiolate complexes. Tissue O(2), O(*), low molecular weight thiols and transition metals (especially FeII) play a pivotal role in directing NO towards targets responsible for biological effects, or storage or release from these stores. In addition, circulating forms of NO have been proposed with S-nitrosation of blood proteins. All these mechanisms provide potential pharmacological targets for future therapeutic strategies.

Brown bear (Ursus arctos arctos) femoral head and neck excision

A 30-yr-old untamed European female brown bear (Ursus arctos arctos) with a craniodorsal luxation of the right femoral head and bilateral degenerative joint disease of the coxofemoral joint had a femoral head and neck excision following unsatisfactory conservative medical therapy. The bear was injected with zolazepam-tiletamine, and anesthesia was induced with i.v. thiopental and maintained with isoflurane in oxygen via endotracheal tube. A lumbosacral epidural injection of medetomidine-bupivacaine provided additional analgesia. Slight initial cardiorespiratory depression was counteracted with fluid and inotropic drug administration and ventilatory assistance. The bear's gluteal muscle anatomy differs from that of the dog. Recovery was uneventful. The bear was confined indoors for 6 wk and was able to ambulate normally within 6 mo.

Inhaled nitric oxide in acute respiratory distress syndrome: a pilot randomized controlled study

This pilot randomized controlled clinical trial of patients with ARDS was implemented to study the impact of inhaled nitric oxide (inhNO) on lung function, morbidity, and mortality. Thirty patients with ARDS were randomly allocated to usual care or usual care plus inhNO. The optimal dose of inhNO was determined to be between 0.5 and 40 parts-per-million daily. All therapeutic interventions were standardized. ARDS resulted mainly from sepsis (25 of the 30). During the first 24 h, the hypoxia score increased greatly in patients treated with inhNO +70.4 mm Hg (+59%) versus +14.2 mm Hg (+9.3%) for the control group (p = 0.02), venous admixture decreased from 25.7 to 15.2% in the inhNO group, and from only 19.4 to 14.9% in the control group (p = 0.05). After the first day of therapy no further beneficial effect of inhNO was detected. Forty percent of the patients treated with inhNO were alive and weaned from mechanical ventilation within 30 d after randomization compared with 33.3% in the control group (p = 0.83). The 30-d mortality rate was similar in the two groups; most deaths (11 of 17) were due to multiple organ dysfunction syndrome. This study shows that inhNO, in this population, may improve gas exchange but does not affect mortality.

Inhaled nitric oxide: technical aspects of administration and monitoring

OBJECTIVES

Clinical applications of inhaled nitric oxide (NO) therapy resulted in the development of delivery systems and monitoring devices applicable to routine clinical care. This article presents the various components necessary for an adequate clinical use of inhaled NO, and discusses the NO gas mixture cylinders, inhaled NO delivery techniques and specifications, monitoring devices, and ending with an exhaustive description of the scavengers of nitrogen oxides (NOx).

DATA SOURCES

Computerized search (CURRENT CONTENTS, MEDLINE) of published original research and review articles (approximately 200), conference abstracts and compendiums up to May 1997 (approximately 50), personal files, and contact with expert informants.

STUDY SELECTION

Technical, experimental, and clinical reports were selected from the recent English, French, German, and Spanish literature, if pertinent to the administration or monitoring of inhaled NO.

DATA EXTRACTION

The authors extracted all applicable data.

DATA SYNTHESIS

The production of NO gas mixture cylinders must be certified with respect to gas purity, stability, and concentration (limits between 100 and 1000 ppm), guaranteed calibration, and specific color. An ideal inhaled NO delivery device requires a synchronized delivery, a minimal production of nitrogen dioxide (NO2), and should be simple to use (verification, calibration, convenient flushing, cylinder change possible while in use and a simple alarm setting) with full information (high and low alarms and available precision monitoring of NO, NO2, and O2). Emergency and transport systems must be readily available. The choice of the monitoring device (chemiluminescence or electrochemistry) should be made based on the knowledge of their strength and weakness for a particular clinical application. Finally, scavengers of NOx should be used with caution until specific filters are proven safe and effective.

CONCLUSIONS

The great expectancies generated by inhaled NO action have led researchers to design personal inhaled NO delivery systems, but only with mitigated results. At present, medical companies are finding a financial interest in designing a delivery system which will suit the needs of clinicians and this, along with official governmental approval, will only then permit the use of inhaled NO safely and on a larger scale.

Extra-pulmonary effects of inhaled nitric oxide in swine with and without phenylephrine

We have compared the effects of inhaled nitric oxide (iNO) and i.v. nitroglycerin (ivGTN) on the haemodynamic response to phenylephrine-induced hypertension (PEHT) in anaesthetized pigs. PEHT did not change either pulmonary vascular resistance or gas exchange throughout all experiments. Both treatments lowered pulmonary arterial pressure to the same extent (-12.4% iNO; -13.7% ivGTN) and passively via an effect on left atrial pressure (-26.3% iNO; -31.4% ivGTN). Both treatments failed to reverse the decrease in renal blood flow (RBFc) induced by PEHT, but both increased urinary flow (UF) (+128% iNO; +148% ivGTN). IvGTN significantly increased plasma concentrations of nitrite and nitrate during (+22.7% arterial blood; +26.2% venous blood) and beyond the period of infusion (iNO: +6.4% and +4.9%, respectively). In four control pigs (no PEHT), iNO markedly increased RBFc (+109%), glomerular filtration rate (+72.5%) and UF (+68.7%). We conclude that iNO may have direct cardiac and renal effects, probably via intervention of NO carrier forms such as S-nitroso compounds.

Inhaled nitric oxide: clinical applications, indications, and toxicology

PURPOSE

Although the analogy of nitric oxide (NO) to Endothelium-derived Relaxing Factor remains controversial, medical use of exogenous NO gas by inhalation has grown exponentially. This review presents the mechanisms of action of inhaled NO in pulmonary hypertension, hypoxaemia, inflammation and oedema, as well as its therapeutic and diagnostic indications with emphasis on acute respiratory distress syndrome (ARDS) and toxicology.

SOURCE

Two medical databases (Current Contents, Medline) were searched for citations containing the above-mentioned key words to December 1996. Moreover, many presentations in congresses such as 4th International Meeting of Biology of Nitric Oxide, 52nd and 53rd Annual Meeting of Canadian Anaesthetists' Society or 10th Annual Meeting of European Association of Cardiothoracic Anaesthesiologists were used.

PRINCIPAL FINDINGS

Inhaled NO is now recognized as an invaluable tool in neonatal and paediatric critical care, and for heart/lung surgery. Other clinical applications in adults, such as chronic obstructive pulmonary disease and ARDS, require a cautious approach. The inhaled NO therapy is fairly inexpensive, but it would seem that it is not indicated for everybody with regards to the paradigm of its efficiency and potential toxicity. The recent discovery of its anti-inflammatory and extrapulmonary effects open new horizons for future applications.

CONCLUSION

Clinical use of inhaled NO was mostly reported in case series, properly designed clinical trials must now be performed to establish its real therapeutic role. These trials would permit adequate selection of the cardiopulmonary disorders, and subsequently the patients that would maximally benefit from inhaled NO therapy.

Effects of reducing reagents and temperature on conversion of nitrite and nitrate to nitric oxide and detection of NO by chemiluminescence

To measure the concentration of nitrites and nitrates by chemiluminescence, we examined the efficiency of five reducing agents [V(III), Mo(VI) + Fe(II), NaI, Ti(III), and Cr(III)] to reduce nitrite (NO2-) and (or) nitrate (NO3-) to nitric oxide (NO). The effect of each reducing agent on the conversion of different amounts of NO2- and (or) NO3- (100-500 pmol, representing concentrations of 0.4 to 2 mu molar) to NO was determined at 20 degrees C for NO2- and at 80 degrees C for NO3-. The effect of temperature from 20 to 90 degrees C on the conversion of a fixed amount of NO2- or NO3- (400 pmol or 1.6 mu molar) to NO was also determined. These five reducing agents are similarly efficient for the conversion of NO2- to NO at 20 degrees C. V(III) and Mo(VI) + Fe(II) can completely reduce NO3- to NO at 80 degrees C. NaI and Cr(III) were unable to convert NO3- to NO. Increased temperature facilitated the conversion of NO3- to NO, rather than that of NO2- to NO. We evaluated the recovery of NO2- and NO3- from plasmas of pig and of dog. Recovery from plasma of both animals was reproducible and near quantitative.

Evaluation of analgesia and cardiorespiratory effects of epidurally administered butorphanol in isoflurane-anesthetized dogs

OBJECTIVE

To determine variations in minimal alveolar concentration (MAC) of isoflurane and analgesic and cardiorespiratory effects of lumbosacral epidural administration of 0.25 mg of butorphanol/kg of body weight in dogs.

ANIMALS

16 healthy male dogs.

PROCEDURE

Dogs were anesthetized with isoflurane alone. Eight dogs received butorphanol (group B) and the others an equal volume of isotonic saline solution (group S) administered by a catheter inserted in the lumbosacral epidural space. Isoflurane MAC was determined before and 30 minutes after the epidural injection, along with noxious stimulation to the fore- and bind limbs. Cardiorespiratory variables were recorded prior to and until 120 minutes after epidural administration. At that time, isoflurane anesthesia was ended, and nociception (toe pinch and pin-prick responses) was evaluated for 7 hours. Dogs were observed for 3 days to determine presence of neurologic side effects.

RESULTS

For group-B dogs, isoflurane MAC decreased by 31 +/- 8.6% after butorphanol was administered Cutaneous insensitivity (to pin-prick nociceptive test) persisted for 3 hours after the end of isoflurane anesthesia in group-B dogs. No response was observed to toe pinch stimulation for 80 minutes after anesthesia.

CONCLUSIONS

Epidural administration of 0.25 mg of butorphanol/kg in dogs was safe; minimal cardiorespiratory and no neurologic side effects were observed, and analgesia and an isoflurane-sparing effect were apparent.

CLINICAL RELEVANCE

The short duration of action of epidurally administered butorphanol limits its value for clinical practice.

Comparison of the effect of inhaled nitric oxide and intravenous nitroglycerine on hypoxia-induced pulmonary hypertension in pigs

Pulmonary hypertension is usually treated with intravenous (i.v.) vasodilators, but their use is limited by systemic effects. In the current study, we compared the effects of inhaled nitric oxide and intravenous nitroglycerine on pulmonary and systemic haemodynamic responses as well as on gas exchange measurements in anaesthetized pigs whose pulmonary pressure was increased by hypoxia (FiO2 = 15%). Both treatments reduced pulmonary pressure to the control level. Inhaled nitric oxide did not affect systemic arterial pressure but intravenous nitroglycerine decreased it from 126.2 to 108.8 mmHg (P = 0.04). Unlike intravenous nitroglycerine, inhaled nitric oxide increased arterial PaO2 from 5.3 to 5.9 kPa (P = 0.02). Both treatments diminished central venous pressure and left atrial pressure, suggesting a possible cardiac effect. Inhaled nitric oxide was shown to be a potent pulmonary vasodilator which attenuated pulmonary hypertension and improved arterial oxygenation without important direct effects on systemic pressure in porcine hypoxia-induced pulmonary hypertension.

Pharmacokinetics of epidural butorphanol in isoflurane-anaesthetized dogs

Sixteen healthy male dogs were used at random in this protocol. The dogs were anaesthetized with isoflurane in oxygen. Eight of the dogs received 0.25 mg/kg of butorphanol (group B) and the others an equal volume of isotonic saline (group S) administered by a catheter inserted in the lumbosacral epidural space. Butorphanol concentrations in plasma and cerebrospinal fluid (CSF) were measured using high-performance liquid chromatography with electrochemical detection. Maximum concentration of butorphanol and time to obtain this concentration were 42.28 ng/mL at 13.88 min in blood, and 18.03 ng/mL at 30 min in CSF. Volume of distribution, clearance, mean distribution and elimination half-lives were respectively 4.39 L/kg, 2.02 L/h.kg, 16.5 min and 189.1 min. Mean isoflurane minimal alveolar concentration values for group B obtained following hind- or forelimb stimulation decreased by 31% after epidural butorphanol. Cutaneous analgesia (to pin-prick test) persisted for 3 h after the end of isoflurane anaesthesia in group B and was in correlation with the plasmatic analgesic dose of butorphanol (9 ng/mL). These results suggested that analgesia was predominantly obtained by action of butorphanol on the supraspinal structures following its vascular systemic absorption.

Comparison of two administration techniques of inhaled nitric oxide on nitrogen dioxide production

The purpose of this study was to verify whether, compared with the introduction of the NO-N2 mixture at the air inlet of the ventilator (classical method), a direct injection of NO-N2 into the inspiratory line of the ventilator circuit with a new injection device (new method), would reduce NO2 formation by reducing contact time between O2 and NO. The effect of two FIO2(0.21 and 0.90) and NO concentrations on NO2 production was determined. In the classical method, NO and O2 were mixed with an air/oxygen blender before the gas mixture entered the ventilator. In the new method, NO was injected directly into the respiratory line with the injection system. Nitric oxide and nitrogen dioxide gases were measured using a chemiluminescence analyzer. For a FI02 of 0.90 and 90 ppm of NO2, the amount of NO2 produced was decreased from 8.9 +/- 0.8 ppm (mean +/- SD) with the classical injection system to 4.4 +/- 0.2 ppm with the new injection system (P = 0.0039, Mann-Whitney test), and NO2 production was decreased from 4.5 +/-0.2 ppm to 2.1 +/- 0.4 ppm (P = 0.02) at 60 ppm of NO. However, at a FIO2, no difference was found in the amount of NO2 produced. We conclude that, compared with the classical method of NO administration, the new NO injection system reduces considerably the concentration of inhaled NO2 when a high FIO2 and a high concentration of NO are used.

[Intravenous anesthesia in the horse: comparison of xylazine-ketamine and xylazine-tiletamine-zolazepam combinations]

Intravenous anesthesia in the horse: Comparison of xylazine-ketamine and xylaxine-tiletamine-zolazepam combinations. Six healthy adult horses were anesthetized twice at random with following intravenous combinations: 1.1 mg/kg of body weight (BW) of xylazine followed by 2.2 mg/kg BW of ketamine (X-K) and 1.1 mg/kg BW of xylazine followed by 1.65 mg/kg BW of tiletamine-zolazepam (X-TZ). The modifications of some cardiorespiratory parameters and the duration of anesthesia were evaluated and compared for the 2 protocols used. Few significant differences were observed between the 2 protocols in regard to the cardiorespiratory parameters measured. The respiratory rate was lower (7 breaths per minute) and the heart rate was higher (34 beats per minute) with the X-TZ combination. The duration of anesthesia with this technique was 33 +/- 3 minutes (X +/- Sx) and longer than with X-K (18 +/- minutes (X +/- Sx)). Superficial analgesia lasted 14,5 +/- 3 minutes with the X-K combination and 31,7 +/- 3,2 minutes for the X-TZ combination. The 2 protocols are associated with a reduction of PaO2.