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Vet Anaesth Analg [journal]
- Cardiovascular tolerance of intravenous lidocaine in broiler chickens (Gallus gallus domesticus) anesthetized with isoflurane. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Sep 17.
To determine the cardiovascular effects of lidocaine infused intravenously (IV) in broiler chickens.Two phase study: Phase 1, randomized up-and-down study to determine effective dose 50 (ED50 ) for lidocaine; Phase 2, prospective randomized study to determine the cardiovascular effects of lidocaine.Seventeen Ross-708 broiler chickens (Gallus gallus domesticus) [11 chickens (Phase 1) and 6 chickens (Phase 2)], weighing 2.6-4.3 kg.After induction of anesthesia with isoflurane and placement of monitoring equipment including invasive blood pressure, chickens were administered lidocaine IV. During Phase 1, using an up-and-down design, each animal received a variable dose selected based on the response of the previous animal. During Phase 2, each animal was administered 6 mg kg(-1) of lidocaine IV over 2 minutes. Clinically irrelevant cardiovascular effects were defined as a relative decrease of heart rate (HR) and mean blood pressure (MAP) <30% subsequent to IV lidocaine administration. The ED50 was defined as the dose rate that would cause clinically irrelevant cardiovascular depression in 50% of the population.During Phase 1, using an up-and-down study design (n = 11), the ED50 of lidocaine was determined to be 6.30 mg kg(-1) and 6.22 mg kg(-1) (95% confidence interval, 5.30-7.13 mg kg(-1) ), when calculated by Dixon's up-and-down method, and logistic regression, respectively. During Phase 2, following infusion of lidocaine (6 mg kg(-1) ), no clinically relevant effects on HR or MAP were detected in any animal.Previous reports state that the dose of lidocaine used in birds should be ≤4 mg kg(-1) . In this study, 6 mg kg(-1) of lidocaine injected IV was not associated with adverse cardiovascular effects. These results suggest that the dose of 4 mg kg(-1) can be exceeded, at least in chickens, and opens the possibility of other therapeutic uses for lidocaine in birds.
- Comparison of three ultrasound guided approaches to the lumbar plexus in dogs: a cadaveric study. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Sep 4.
To assess the accuracy of contrast material injection and the dispersion of injectate following ultrasound guided injections at the level of L6 and L7, in canine cadavers.Prospective, randomized, experimental study.Twenty nine mixed breed canine cadavers (28.9 ± 6.0 kg).Three ultrasound-guided approaches to the lumbar plexus (LP) were compared: 1) a dorsal pre-iliac approach at the level of L6; 2) a lateral paravertebral approach at mid-L6; and 3) a lateral paravertebral approach at mid-L7. An isovolumic mixture of iodine-based contrast with new methylene blue (0.1 mL kg(-1) ) was injected bilaterally in the juxta-foraminal region along the L6 or L7 nerve root. Computed tomography was performed followed by segmentation and 3D reconstruction of the lumbar spine and contrast material volumes using dedicated software. Distances between contrast material and the fifth through seventh lumbar foraminae, and length of femoral (FN) and obturator (ON) nerve staining were measured and compared between approaches (p < 0.05).Injectate moved cranial and caudal to the site of injection, and dispersed into an ovoid shape between the quadratus lumborum, iliopsoas and psoas minor muscles. Injections at L7 resulted in significantly closer contrast proximity to the L6 and L7 foraminae (p < 0.001). Femoral nerve staining was similar for all approaches, ON staining was more consistent after L7 injections (p < 0.001).An ultrasound-guided lateral paravertebral approach to the LP proved very practical and accurate, with easy visualization of the plexus and associated nerves. To ensure that the ON is covered by injectate, an approach at the level of L7 is recommended. Further studies are necessary to determine if this correlates with clinically effective local anesthesia.
- Assessing the influence of mechanical ventilation on blood gases and blood pressure in rattlesnakes. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Aug 30.
To characterize the impact of mechanical positive pressure ventilation on heart rate (HR), arterial blood pressure, blood gases, lactate, glucose, sodium, potassium and calcium concentrations in rattlesnakes during anesthesia and the subsequent recovery period.Prospective, randomized trial.Twenty one fasted adult South American rattlesnakes (Crotalus durissus terrificus).Snakes were anesthetized with propofol (15 mg kg(-1) ) intravenously, endotracheally intubated and assigned to one of four ventilation regimens: Spontaneous ventilation, or mechanical ventilation at a tidal volume of 30 mL kg(-1) at 1 breath every 90 seconds, 5 breaths minute(-1) , or 15 breaths minute(-1) . Arterial blood was collected from indwelling catheters at 30, 40, and 60 minutes and 2, 6, and 24 hours following induction of anesthesia and analyzed for pH, PaO2 , PaCO2 , and selected variables. Mean arterial blood pressure (MAP) and HR were recorded at 30, 40, 60 minutes and 24 hours.Spontaneous ventilation and 1 breath every 90 seconds resulted in a mild hypercapnia (PaCO2 22.4 ± 4.3 mmHg [3.0 ± 0.6 kPa] and 24.5 ± 1.6 mmHg [3.3 ± 0.2 kPa], respectively), 5 breaths minute(-1) resulted in normocapnia (14.2 ± 2.7 mmHg [1.9 ± 0.4 kPa]), while 15 breaths minute(-1) caused marked hypocapnia (8.2 ± 2.5 mmHg [1.1 ± 0.3 kPa]). Following recovery, blood gases of the four groups were similar from 2 hours. Anesthesia, independent of ventilation was associated with significantly elevated glucose, lactate and potassium concentrations compared to values at 24 hours (p < 0.0001). MAP increased significantly with increasing ventilation frequency (p < 0.001). HR did not vary among regimens.Mechanical ventilation had a profound impact on blood gases and blood pressure. The results support the use of mechanical ventilation with a frequency of 1-2 breaths minute(-1) at a tidal volume of 30 mL kg(-1) during anesthesia in fasted snakes.
- Perioperative physiology and pharmacology in the obese small animal patient. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Aug 6.
To review the available literature concerning the physiologic and pharmacologic alterations induced by obesity in canine and feline patients and their relevance to perioperative care.Literature review.Pubmed, CAB, Web of Science.Obesity of cats and dogs is a chronic inflammatory condition that is increasingly prevalent. Similar to the situation in humans, small animal obesity may be associated with changes in endocrine, respiratory, and cardiovascular function. In addition, alteration of body composition in obesity can affect pharmacokinetic variables. Modifications in perioperative care may need to be made for obese dogs and cats, including attention to respiratory and cardiovascular supportive care and drug dose adjustments.
- A tribute to dr. Steve haskins. [Journal Article]
- Vet Anaesth Analg 2014 Sep; 41(5):550-1.
- Cardiopulmonary and anesthetic effects of the combination of butorphanol, midazolam and alfaxalone in Beagle dogs. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Aug 12.
To evaluate the physiological variables, arterial blood gas values, induction of anesthesia quality, and recovery quality using the combination of butorphanol, midazolam and alfaxalone in dogs.Ten healthy adult Beagle dogs weighing 8.3 ± 3.1 kg.Rectal temperature (T), pulse rate (PR), respiratory rate (fR ), mean arterial pressure (MAP), and arterial blood gases were measured and recorded prior to intravenous (IV) administration of butorphanol, prior to administration of both midazolam and alfaxalone IV 10 minutes later, then every 5 minutes for 20 minutes. M-mode echocardiographic left ventricular (LV) indices were measured before and 5 minutes after administration of alfaxalone. Qualitative scores for induction of anesthesia and recovery were allocated, duration of anesthesia and recovery were calculated, and adverse events were recorded.Scores for induction and recovery quality were excellent. No significant adverse events were observed. Mean ± SD time from induction to extubation and to standing (full recovery) was 29 ± 6 and 36 ± 8 minutes, respectively. There were statistically significant changes in PR, fR and MAP after drug administration. Transient hypercarbia developed after alfaxalone injection. The echocardiographic LV indices were reduced after alfaxalone injection, although those changes were not statistically significant.The combination of butorphanol, midazolam and alfaxalone provided excellent quality of induction of anesthesia and exerted minimal cardiopulmonary effects in healthy dogs.
- Comparison of respiratory function during TIVA (romifidine, ketamine, midazolam) and isoflurane anaesthesia in spontaneously breathing ponies Part I: blood gas analysis and cardiorespiratory variables. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Aug 7.
To compare pulmonary function and gas exchange in ponies during maintenance of anaesthesia with isoflurane or by a total intravenous anaesthesia (TIVA) technique.Experimental, cross-over study.Six healthy ponies weighing mean 286 (range 233-388) ± SD 61 kg, age 13 (9-16) ± 3 years.The ponies were anaesthetized twice, a minimum of two weeks apart. Following sedation with romifidine [80 μg kg(-1) intravenously (IV)], anaesthesia was induced IV with midazolam (0.06 mg kg(-1) ) and ketamine (2.5 mg kg(-1) ), then maintained either with inhaled isoflurane (Fe'Iso = 1.1 vol%) (T-ISO) or an IV infusion of romifidine (120 μg kg(-1) hour(-1) ), midazolam (0.09 mg kg(-1) hour(-1) IV) and ketamine (3.3 mg kg(-1) hour(-1) ) (T-TIVA). Ponies were placed in lateral recumbency. Breathing was spontaneous and Fi'O2 60%. After an instrumentation/stabilisation period of 30 minutes, arterial and mixed venous blood samples were taken simultaneously every 10 minutes for 60 minutes and analysed immediately. Oxygen extraction ratio (O2 ER) and venous admixture were calculated. Tidal volume (TV), minute volume (MV), respiratory rate (fR ), packed cell volume (PCV), arterial blood pressure and heart rate (HR) were measured and recorded. Data were analysed with mixed model anova (α = 0.05). Treatments were compared overall and at two selected time points (T30 and T60) using Bonferroni correction.Arterial and mixed venous partial pressures of O2 and CO2 , and TV were significantly lower and MV and fR were higher in T-TIVA compared to T-ISO. Venous admixture did not differ between treatments. O2 ER was significantly higher in T-TIVA. Mean arterial pressure was higher and HR was lower in T-TIVA compared to T-ISO.Whilst arterial CO2 was within an acceptable range during both protocols, the impairment of oxygenation was more pronounced with the T-TIVA evidenced by lower arterial and venous oxygen partial pressures.
- The cardiopulmonary effects of dexmedetomidine infusions in dogs during isoflurane anesthesia. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Jul 31.
To determine the cardiopulmonary changes associated with intravenous (IV) infusions of dexmedetomidine at equipotent isoflurane-dexmedetomidine concentrations compared with isoflurane alone.Prospective, randomized, crossover experiment.Six adult intact female mixed-breed dogs weighing (mean ± SD [range]) 23.3 ± 3.8 (17.8-29.4) kg.Anesthesia was induced and maintained with isoflurane in oxygen. Measurements of respiratory rate (fR ), heart rate (HR), systemic and pulmonary arterial pressures (SAP, DAP, MAP, MPAP), central venous pressure (CVP), pulmonary arterial occlusion pressure (PAOP), cardiac index (CI), left and right ventricular stroke work index (LVSWI, RVSWI), systemic and pulmonary vascular resistance index (SVRI, PVRI), arteriovenous shunt (Q˙s/Q˙t), oxygen delivery (D˙O2), oxygen extraction ratio (O2 ER), oxygen consumption, arterial and mixed venous blood gases, and arterial packed cell volume (PCV) were obtained 30 minutes after instrumentation at an end-tidal isoflurane concentration (Fe'Iso) of 1.73 ± 0.02% (1.3 MAC). Dexmedetomidine was administered IV at 0.5 or 3 μg kg(-1) over 6 minutes followed by an infusion at 0.5 (LD) or 3 μg kg(-1) hour(-1) (HD), respectively, with Fe'Iso at 1.41 ± 0.02 (LD) or 0.72 ± 0.09% (HD). Measurements were taken at 10, 30, 60, 90, 120, 150 and 180 minutes after the start of the infusion.The low dose produced significant decreases in HR, increases in SAP, DAP, CVP, MPAP, PAOP and LVSWI, but no change in CI. HD produced significant increases in SAP, MAP, DAP, CVP, PAOP, SVRI, LVSWI, O2 ER and PCV and significant decreases in CI and D˙O2. There were significant differences between treatments in HR, MAP, DAP, CVP, MPAP, PAOP, CI, SVRI, HCO3-, SBE, D˙O2, O2 ER and Q˙s/Q˙t.Cardiopulmonary changes associated with LD were within clinically accepted normal ranges whereas HD produced clinically significant changes. The LD may be useful as an anesthetic adjunct in healthy dogs.
- Anaesthetic and cardiorespiratory effects of a constant rate infusion of fentanyl in isoflurane- anaesthetized sheep. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Jul 31.
To determine the anaesthetic and cardiorespiratory effects of a constant rate infusion of fentanyl in sheep anaesthetized with isoflurane and undergoing orthopaedic surgery.Prospective, randomised, 'blinded' controlled study.Twenty healthy sheep (weight mean 41.1 ± SD 4.5 kg).Sheep were sedated with intravenous (IV) dexmedetomidine (4 μg kg(-1) ) and morphine (0.2 mg kg(-1) ). Anaesthesia was induced with propofol (1 mg kg(-1) minute(-1) to effect IV) and maintained with isoflurane in oxygen and a continuous rate infusion (CRI) of fentanyl 10 μg kg(-1) hour(-1) (group F) or saline (group P) for 100 minutes. The anaesthetic induction dose of propofol, isoflurane expiratory fraction (Fe'iso) required for maintenance and cardiorespiratory measurements were recorded and blood gases analyzed at predetermined intervals. The quality of recovery was assessed. Results were compared between groups using t-tests or Mann-Whitney as relevant.The propofol induction dose was 4.7 ± 2.4 mg kg(-1) . Fe'iso was significantly lower (by 22.6%) in group F sheep than group P (p = 0). Cardiac index (mean ± SD mL kg(-1) minute(-1) ) was significantly (p = 0.012) lower in group F (90 ± 15) than group P (102 ± 35). Other measured cardiorespiratory parameters did not differ statistically significantly between groups. Recovery times and recovery quality were statistically similar in both groups.Fentanyl reduced isoflurane requirements without clinically affecting the cardiorespiratory stability or post-operative recovery in anaesthetized sheep undergoing orthopaedic surgery.