A clinical comparison between a non-invasive blood pressure monitor using high definition oscillometry (Memodiagnostic MD 15/90 Pro) and invasive arterial blood pressure measurement in anaesthetized dogs.

OBJECTIVE: To compare high definition oscillometry (HDO) to invasive blood pressure measurement in anaesthetized dogs. STUDY DESIGN: Prospective, clinical trial. ANIMALS: Fifty dogs weighing 1.95-79 kg (mean 23.5 kg). MATERIALS AND METHODS: Anaesthetic and peri-anaesthetic management was chosen according to each dog's physical status and anaesthetist's preference. Direct arterial blood pressure measurements were performed using a catheter placed in the dorsal pedal artery and an electronic pressure transducer connected to a multiparameter monitor. Non-invasive blood pressure measurements were performed using an appropriately sized cuff placed around the tail base. Comparisons between the two methods were made using Bland and Altman plots. The data are reported as mean bias (lower, upper limits of agreement). Further analysis was performed after separating the data into the following categories based on invasive mean arterial blood pressure (MAP): high (MAP > 100 mmHg), medium (70 mmHg < MAP < 100 mmHg) and low (MAP < 70 mmHg) blood pressure (BP). The two methods were compared as used clinically. RESULTS: Eight hundred measurement pairs for invasive and HDO BP readings were compared. Overall, the HDO measured lower values for SAP and DAP but higher for MAP than the invasive method. The lowest bias (upper, lower limits of agreement) were obtained for MAP, -1 (-22, 19) mmHg. The biggest discrepancy between the methods was reflected by a large bias (limits of agreement) 5 (-34, 45) mmHg, was for SAP. The results for DAP were between those for SAP and MAP with a bias (limits of agreement) of 3 (-20, 27) mmHg. When the values were separated into the pressure range categories the HDO measured higher in the high, medium and low BP groups, with the exception of SAP in the low BP group. CONCLUSIONS: When considering the mean bias, the accuracy of HDO compared well with direct arterial blood pressure, but the precision was poor, as determined by wide limits of agreement. CLINICAL RELEVANCE: Using trends and serial measurements rather than a single measurement for clinical decision making is recommended with both methods, when used as reported here.

Neuraxial morphine induced pruritus in two cats and treatment with sub anaesthetic doses of propofol.

HISTORY: Two cats were presented for orthopaedic surgery. PHYSICAL EXAMINATION: With the exception of the orthopaedic injuries found, clinical examination showed no abnormality. MANAGEMENT: As part of anaesthetic management, one cat received intrathecal morphine, the other epidural morphine. Following recovery, intense grooming was observed. After ensuring adequate analgesia this behaviour was interpreted as pruritus. In the first cat, pruritus was initially managed with medetomidine constant rate infusion (CRI) at 1 and 1.5 µg kg(-1)  hour(-1) . The lower dose produced sedation and no relief from pruritus, the higher dose ablated pruritus but induced sedation. Two propofol (lipid emulsion formulation) boli of 0.1 mg kg(-1) ablated pruritus without causing sedation. The second cat was successfully treated with four boli of 0.1 mg kg(-1) propofol over 20 minutes. FOLLOW-UP: Following treatment with propofol, pruritus did not recur in either cat and both were discharged from the hospital. CONCLUSIONS: This is the first clinical report of morphine-induced pruritus in cats and management with low-dose propofol. These cases suggest an antipruritic mechanism for lipid-formulation propofol.

Long-term use of gabapentin for musculoskeletal disease and trauma in three cats.

Gabapentin has been widely used in human medicine to control acute and chronic pain. Although the exact mechanism of action has yet to be determined, its use in veterinary medicine is increasing. The clinical use of gabapentin for analgesia in cats has been reported in review articles and one case report. Managing chronic pain, particularly in the feline patient, poses a challenge to veterinary surgeons. This report details the long-term use of gabapentin for musculoskeletal pain or head trauma in three cats. All cats received gabapentin for several months at an average dose of 6.5 mg/kg q12h. Clinical signs suggestive of pain, such as aggression, avoiding human interaction and loss of appetite, were observed to decrease with the administration of gabapentin, used as part of an analgesia regime or as sole medication. Long-term follow-up with the owners of all cats indicated that satisfactory pain management was achieved, administration was easy and no obvious side effects during the period of administration occurred. We conclude that long-term treatment with gabapentin is of potential benefit in controlling pain in cases of head trauma, as well as musculoskeletal disease. It may provide a valuable adjunct for the management of chronic pain in cats and should be investigated further for its clinical use and safety.

Use of a laryngeal mask airway in a brachycephalic dog with masticatory myositis and trismus.

An 8-month old, male, neutered bulldog was presented for investigation of a 2-day history of trismus. Endotracheal intubation was impossible as the dog was only able to open his mouth approximately 2 cm. A laryngeal mask airway was blindly inserted after induction of general anesthesia to maintain the patient on inhalational anesthesia and improve respiration for computed tomography and muscle biopsy. The dog recovered from anesthesia uneventfully.

Severe pruritus and myoclonus following intrathecal morphine administration in a dog.

During epidural needle placement in a 32-kg dog the subarachnoid space was punctured and half the intended dose of lidocaine, bupivacaine, and morphine was injected. After recovery from anesthesia the dog showed signs of severe pruritus of the tail base and limbs and myoclonus of the tail and hind limbs. Methadone, acepromazine, ketamine, buprenorphine, and butorphanol were administered to control myoclonus and pruritus, but were unsuccessful. Diazepam was used to control myoclonus until the effects of morphine abated.During epidural needle placement in a 32-kg dog the subarachnoid space was punctured and half the intended dose of lidocaine, bupivacaine, and morphine was injected. After recovery from anesthesia the dog showed signs of severe pruritus of the tail base and limbs and myoclonus of the tail and hind limbs. Methadone, acepromazine, ketamine, buprenorphine, and butorphanol were administered to control myoclonus and pruritus, but were unsuccessful. Diazepam was used to control myoclonus until the effects of morphine abated.

RésuméPrurit aigu et myoclonie après l'administration intrathécale de morphine chez un chien. Durant le placement d'une aiguille épidurale chez un chien de 32 kg, l'espace sous-arachnoïdien a été ponctionné et la moitié de la dose prévue de lidocaïne, de bupivacaïne et de morphine a été injectée. Après le réveil de l'anesthésie, le chien a manifesté des signes de prurit grave à la base de la queue et sur les membres et une myoclonie de la queue et des membres postérieurs. La méthadone, l'acépromazine, la kétamine, la buprénorphine et le butorphanol ont été administrés pour contrôler la myoclonie et le prurit, mais sans succès. Le diazépam a été utilisé pour contrôler la myoclonie jusqu'à ce que les effets de la morphine se résorbent.(Traduit par Isabelle Vallières).

Evaluation of variables to describe the shape of volumetric capnography curves during bronchoconstriction in dogs.

The aim of the study was to investigate changes in volumetric capnography (V(C)) variables during bronchoconstriction in dogs and compare it with total respiratory resistance (R(L)) measured with a Fleisch pneumotachograph. Six dogs were challenged with increasing concentrations of carbachol until obvious signs of bronchoconstriction were seen. All V(C) parameters were obtained before, directly after, 10 and 20 min after maximal bronchoconstriction. The slope of phase III (SIII) and airway and alveolar dead space parameters were significantly different from baseline directly after the challenge. The V(C) curve obtained a typical shape at the time of maximal bronchoconstriction and a trend to return to baseline shape was seen over time. A significant correlation was found for all aforementioned parameters with R(L). We conclude that the shape of the V(C) curve in combination with dead space calculation can be used to verify bronchoconstriction on a breath-to-breath basis.

The use of an acoustic device to identify the extradural space in standing horses.

OBJECTIVE: To determine the usefulness of an acoustic device to confirm correct placement of extradural needles in horses. STUDY DESIGN: Prospective experimental study. ANIMALS: Twelve adult healthy horses weighing between 434 and 640 kg. MATERIALS AND METHODS: Horses were sedated, placed in stocks and subjected to caudal extradural anaesthesia using lidocaine 2%. For extradural puncture an 18 gauge Tuohy needle connected to an acoustic device via an electronic pressure transducer was used. This device allowed recording of the extradural pressure profile and the transformation of pressure changes into an audible signal. Extradural needle advancement was stopped and the local anaesthetic administered when either a sharp decrease in sound pitch occurred or a 'pop' sensation was felt. Correct needle placement was assessed clinically by the degree of extradural anaesthesia present using needle prick stimuli, loss of tail tone and occurrence of localized sweating. Descriptive statistical analysis was used for evaluation of the data. RESULTS: Extradural anaesthesia was successful in nine of 12 horses. In these horses during extradural needle advancement the pitch of the audible signal first increased and abruptly changed to a constant low pitched sound. In the three horses with unsuccessful punctures only a slight decrease of the pitch was noted. A 'pop' was clearly distinguished in five of nine horses with successful extradural puncture. In four horses a 'pop' was not present despite correct extradural needle placement. In three horses with incorrect needle placement a 'pop' was present. In the horses with correct needle positioning the median extradural pressure after the puncture was -0.8 kPa (-6 mmHg). CONCLUSION AND CLINICAL RELEVANCE: The acoustic device is useful to assist in the identification of successful or unsuccessful extradural needle placement in the horse.

Evaluation of extradural pressure waves and the 'lack of resistance' test to confirm extradural needle placement in dogs.

This study aimed to evaluate the use of extradural pressure (EDP) waves to confirm extradural needle placement in clinical practice. Lumbosacral extradural anaesthesia was performed in 98 dogs, of which 85 were included for statistical analysis. The extradural space was identified using conventional methods and, after testing lack of resistance to injection of saline, a pressure transducer was connected to the needle. EDP and the occurrence of pressure waves were recorded before and following injection of local anaesthetic. Successful administration of the drug was confirmed by clinical assessment. Extradural anaesthesia was successful in 88% of the dogs. Pressure waves were present in 89% of the animals with successful extradural puncture, but in 35% of dogs the waves occurred following extradural injection but not before. In 11% of dogs no EDP waves were observed. EDP prior to administration of the local anaesthetic was 0.4+/-1.0 kPa but following the injection values were significantly higher (4.7+/-2.9 kPa) and there was no difference between pressures following successful and unsuccessful punctures. It was concluded that EDP waves can be used to confirm correct needle placement in dogs in clinical practice and measurement is most reliable following extradural injection.

Measurement of the puncture profile and extradural pressure of cattle during extradural anaesthesia.

OBJECTIVE: To measure the pressure profile during caudal extradural puncture and subsequent extradural anaesthesia in cattle and to investigate the presence of extradural pressure waves. STUDY DESIGN: Prospective experimental study. ANIMALS: Eleven cattle aged 4.1 +/- 2.5 years (range 0.8 to 8.8 years), with a body weight of 613 +/- 162 kg (range 302-840 kg). METHODS: Caudal extradural puncture was performed. To measure the extradural pressure profile, the needle was connected to an electronic pressure transducer placed at the height of the base of the tail. The pressure profile was recorded for 3 minutes following extradural puncture. Lack of resistance to injection of saline was assessed. One minute and 10 minutes after extradural anaesthesia with procaine extradural pressure was recorded. Correct extradural needle placement was assessed by clinical response. RESULTS: Three minutes after extradural puncture the median pressure was -16 (range -25 to 25) mmHg. Pressure in the extradural space 1 minute after the lack of resistance, 3 seconds after injection, and 10 minutes after injection was -15 (-24 to 33) mmHg, 8 (-17 to 84) mmHg, and -7 (-25 to 27) mmHg respectively. Pressure waves were visible after puncture, after lack of resistance, 3 seconds and 10 minutes after injection, in 4, 6, 8 and 7 cattle respectively. Pressure after testing lack of resistance, after the injection of local anaesthetic, as well as at the end of the measurement, period was significantly higher than baseline. All cattle showed clinical signs indicative of successful extradural needle placement. CONCLUSION AND CLINICAL RELEVANCE: Extradural pressure was sub-atmospheric in 82% of the animals. Pressure waves were not consistently present before or after extradural injection, which limits their usefulness to confirm correct extradural needle placement. Extradural pressures increase significantly after injection of local anaesthetic solution. However, the clinical significance of the increase in extradural pressures was not clear.

The extradural pressure profile in goats following extradural injection.

OBJECTIVE: To measure the extradural pressures in goats before and after extradural injection, and to investigate the occurrence of extradural pressure waves. STUDY DESIGN: Prospective experimental trial. ANIMALS: Nine healthy adult goats weighing 59.4 +/- 6.4 kg, scheduled for stifle arthroscopy. METHODS: The goats were pre-medicated with midazolam and anaesthesia was induced with propofol and maintained with sevoflurane. The goats were placed in lateral recumbency and extradural puncture was performed via the lumbosacral space. Correct placement of the needle was assessed by lack of resistance to the injection of saline. The needle was connected to an electronic pressure transducer to record extradural pressure. Measurements were taken before and after extradural injection of methadone (0.1 mg kg(-1), diluted to a total volume of 0.2 mL kg(-1)) and 10 minutes later. Contrast medium was injected and correct extradural needle placement confirmed by radiography. RESULTS: Lack of resistance to injection of saline occurred in all goats, but there were no pressure waves observed before injection in any animal. Radiography indicated incorrect needle placement in four animals and one had pressure waves synchronous with the arterial pulse after methadone injection. Correct needle placement was confirmed in the remaining five animals which exhibited pressure waves after extradural methadone injection. In the five goats with successful needle placement the baseline extradural pressure ranged from 0.4 to 2.5 kPa (3-19 mmHg), increasing to 4.4-39.9 kPa (33-300 mmHg) after injection. Ten minutes after injection, extradural pressure remained elevated and ranged from 2.5 to 17.3 kPa (19-130 mmHg). CONCLUSIONS AND CLINICAL RELEVANCE: Extradural pressure waves were not useful to confirm correct extradural needle placement in laterally recumbent goats. The presence of such waves after injection of 0.2 mL kg(-1) may be indicative of correct placement but even here we saw one of nine animals with extradural pressure waves where we failed to confirm correct needle placement. Extradural pressure increases after extradural injection.

Pressure profile in the caudal extradural space of standing horses before and after extradural drug administration.

The objectives of this study were to measure the pressure in the caudal extradural space of standing horses and to evaluate the usefulness of pressure waves to identify correct needle placement. Caudal extradural pressure was measured in 12 healthy horses. The pressure and any extradural pressure waves were recorded for 3min after puncture, for 1min after testing for lack of resistance (LOR), and for 10min after lidocaine injection. Successful extradural drug administration was confirmed in all horses. The median extradural pressure findings after puncture, after LOR, immediately after injection and 10min after needle placement were -1.60kPa (range -2.27 to 1.33kPa), -0.67kPa (-2.27 to 5.73kPa), 5.00kPa (0.93 to 9.87kPa) and 0.13kPa (-0.67 to 4.53kPa), respectively. Extradural pressure waves were not always present. Extradural space pressure was sub-atmospheric in most horses and extradural injection significantly increased this pressure for up to 10min. Extradural pressure waves had limited usefulness in the confirmation of the correct placement of the needle.

Use of endoscopy for examination of the sacral epidural space in standing cattle.

OBJECTIVE: To develop an epiduroscopic technique for use in standing cattle and describe the endoscopically visible anatomic structures of the epidural space in the sacrococcygeal area. ANIMALS: 6 healthy nonlactating, nonpregnant cows (mean +/- SD age, 60 +/- 18.5 months; mean weight, 599.7 +/- 63.87 kg) and 3 bovine cadavers. PROCEDURES: Cadavers were used to allow familiarization with the equipment and refinement of the technique. Following these experiences, procedures were performed in live animals. Each cow was restrained in a stock. After sedation with xylazine (0.03 mg/kg, IV), 2% lidocaine hydrochloride (0.25 mg/kg) was injected epidurally in the first intercoccygeal or the sacrococcygeal intervertebral space. By use of an introducer set (guidewire and dilation trocar and shaft), a flexible endoscope (length, 75 cm; diameter, 2.3 mm) was inserted through the dilation shaft into the epidural space. To obtain an optimal view, small amounts of air were insufflated into the epidural space through the working channel of the endoscope via a syringe with special filter. RESULTS: Anatomic structures of the epidural space that were viewed by means of the endoscopic procedure included blood vessels, connective tissue, fat, nerves, and the spinal dura mater. No adverse events were detected during epiduroscopy, and it was tolerated well by all 6 cows. CONCLUSIONS AND CLINICAL RELEVANCE: In ruminants, epidural structures can be viewed via endoscopy. Such epiduroscopic procedures may be useful in anatomic studies as well as for the diagnosis of disease or therapeutic interventions in ruminants.

Endoscopic removal of a bronchial carcinoma in a dog using one-lung ventilation.

OBJECTIVE: To describe anesthetic management of endoscopic electrosurgical removal of a bronchial carcinoma, partially blocking the right main stem bronchus in a Cocker Spaniel. STUDY DESIGN: Clinical case report. ANIMALS: Dog with a bronchial carcinoma. METHODS: To allow sufficient space for the endoscope and to avoid an oxygen-rich gas mixture in the trachea, which carries the risk of an airway fire when electrocautery is used, a 1 lumen endobronchial tube (EBT) was inserted into the left main stem bronchus. One-lung ventilation (OLV) started with a volume-controlled ventilator was switched to pressure-controlled ventilation in combination with positive end-expiratory pressure (PEEP). RESULTS: Resection of the bronchial carcinoma was successful. The dog was hypercapnic throughout the procedure and a high alveolar-arterial oxygen gradient was measured. CONCLUSION: An EBT may be a feasible and safe option to provide OLV for bronchoscopic electrocautery with a closed thoracic cavity in dogs. CLINICAL RELEVANCE: EBT intubation for OLV should be considered as part of the anesthetic management of airway diseases treated with bronchoscopic electrocautery.

Two cases of bradyarrhythmia and hypotension after extradural injections in dogs.

OBSERVATIONS: Two healthy obese, seven-year-old, female Rottweilers weighing 40 and 57 kg were submitted for cranial cruciate repair. They were premedicated with intravenous methadone (0.1 mg kg(-1)) and acepromazine (0.01 and 0.02 mg kg(-1)). Anesthesia was induced with propofol (3.6 and 2.5 mg kg(-1)) and maintained with isoflurane in oxygen using a circle breathing system. The dogs were placed in sternal recumbency and epidural injection of lidocaine/bupivacaine or lidocaine/bupivacaine/morphine (0.2 mL/kg, 8 and 11 mL) was carried out over 1.5 and 4 minutes. Epidural pressures were 79 and 72 mmHg at the end of the injections. The first dog's heart rate decreased from 80 to 65 beats minute(-1) with a second degree atrioventricular (AV) block. The arterial pressure decreased from 100 to 50 mmHg. These responded to atropine (0.01 mg kg(-1) IV). The second dog's heart rate decreased from 120 to 60 beats minute(-1) while arterial pressure decreased from 72 to 38 mmHg. No treatment was given and heart rate and arterial blood pressure returned to acceptable ranges. CONCLUSIONS: These cases suggest that large increases in epidural pressure may cause significant cardiovascular effects. This may be avoided by using lower volumes and discontinuing injection if significant back pressure is detected.

Comparison of the cardiopulmonary effects of anesthesia maintained by continuous infusion of ketamine and propofol with anesthesia maintained by inhalation of sevoflurane in goats undergoing magnetic resonance imaging.

OBJECTIVE: To compare the cardiopulmonary effects of anesthesia maintained by continuous infusion of ketamine and propofol with anesthesia maintained by inhalation of sevoflurane in goats undergoing magnetic resonance imaging. ANIMALS: 8 Saanen goats. PROCEDURES: Goats were anesthetized twice (1-month interval) following sedation with midazolam (0.4 mg/kg, IV). Anesthesia was induced via IV administration of ketamine (3 mg/kg) and propofol (1 mg/kg) and maintained with an IV infusion of ketamine (0.03 mg/kg/min) and propofol (0.3 mg/kg/min) and 100% inspired oxygen (K-P treatment) or induced via IV administration of propofol (4 mg/kg) and maintained via inhalation of sevoflurane in oxygen (end-expired concentration, 2.3%; 1X minimum alveolar concentration; SEVO treatment). Cardiopulmonary and blood gas variables were assessed at intervals after induction of anesthesia. RESULTS: Mean +/- SD end-expired sevoflurane was 2.24 +/- 0.2%; ketamine and propofol were infused at rates of 0.03 +/- 0.002 mg/kg/min and 0.29 +/- 0.02 mg/kg/min, respectively. Overall, administration of ketamine and propofol for total IV anesthesia was associated with a degree of immobility and effects on cardiopulmonary parameters that were comparable to those associated with anesthesia maintained by inhalation of sevoflurane. Compared with the K-P treatment group, mean and diastolic blood pressure values in the SEVO treatment group were significantly lower at most or all time points after induction of anesthesia. After both treatments, recovery from anesthesia was good or excellent. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that ketamine-propofol total IV anesthesia in goats breathing 100% oxygen is practical and safe for performance of magnetic resonance imaging procedures.