Cardiovascular tolerance of intravenous bupivacaine in broiler chickens (Gallus gallus domesticus) anesthetized with isoflurane

Objective

To determine the median effective dose (ED₅₀) of intravenous (IV) bupivacaine associated with a 50% probability of causing clinically relevant cardiovascular effects [defined as 30% change in heart rate (HR) or mean arterial pressure (MAP)] in chickens anesthetized with isoflurane.

Effect of preoxygenation before isoflurane induction and rocuronium-induced apnea on time until hemoglobin desaturation in domestic chickens (Gallus gallus domesticus)

ObjectiveTo evaluate the time to hemoglobin oxygen desaturation in chickens (Gallus gallus domesticus) with and without preoxygenation before isoflurane induction of anesthesia and rocuronium-induced apnea.Study designProspective, randomized crossover study.AnimalsA total of 10 healthy adult Lohmann Brown-Lite hens.MethodsHens were anesthetized with isoflurane for intravenous (IV) and intraarterial catheter placement and allowed to fully recover from anesthesia. Hens in the preoxygenation treatment were administered oxygen (2 L minute^–1) via a facemask for 3 minutes prior to induction of anesthesia with 3% isoflurane in oxygen. In the alternative treatment, hens were not preoxygenated prior to induction of anesthesia with isoflurane in oxygen. Apnea was then induced with rocuronium bromide (1.0 mg kg^–1) administered IV, and anesthesia was maintained with IV propofol infusion. A cloacal pulse oximeter measured hemoglobin oxygen saturation (SpO₂). Time was recorded from the start of apnea until SpO₂ was 90% (desaturation). The trachea was intubated, and anesthesia was maintained with isoflurane in oxygen with manual ventilation until spontaneous breathing returned and SpO₂ ≥ 99%. PaO₂ was measured before each treatment, after preoxygenation, postinduction and at desaturation. Data were analyzed between treatments using Wilcoxon matched-pairs signed rank tests with Holm-?idák multiple comparison test, and within treatments using Friedman test with Dunn’s multiple comparison test (p < 0.05). Data are reported as median (range).ResultsTime from start of apnea until hemoglobin desaturation was not significantly different between preoxygenated and nonpreoxygenated hens [26.5 (16–50) seconds and 24.0 (5–57) seconds, respectively; p = 0.25]. No differences in PaO₂ between treatments were observed at any time point.Conclusions and clinical relevancePreoxygenation for 3 minutes before isoflurane mask induction of anesthesia and apnea does not significantly increase time until desaturation in hens.     

Effects of a single intravenous bolus of fentanyl on the minimum anesthetic concentration of isoflurane in chickens (Gallus gallus domesticus)

Objective

To assess the temporal effects of a single fentanyl intravenous (IV) bolus on the minimum anesthetic concentration (MAC) of isoflurane in chickens and to evaluate the effects of this combination on heart rate (HR) and rhythm, systemic arterial pressures (sAP) and ventilation.

Metastatic melanomas in young broiler chickens (Gallus gallus domesticus)

Four young broiler chickens affected by multiple melanotic tumors are described. Grossly, there were multiple tumors composed of melanocytes within the skin, skeletal muscle, and multiple visceral organs. Tumors ranged from flattened macules to masses that extensively replaced viscera. Microscopically, melanocytes were often well pigmented, and while there was moderate nuclear anisokaryosis, mitotic rates were low. Immunohistochemical staining of some melanomas with antibodies to S100 proteins, Melan-A, vimentin, or neuron-specific enolase after bleaching of tumor cells with potassium permanganate revealed lack of immunostaining of tumor cells with antibodies to S100, strong positive staining of tumor cells for neuron-specific enolase, moderate staining with antibodies to vimentin, and faint staining for Melan-A. Only neuron-specific enolase staining was evident in unbleached tumor cells. Attempts to identify exogenous avian leukosis viruses in these tumors were unsuccessful.     

Total intravenous anesthesia in domestic chicken (Gallus gallus domesticus) with propofol alone or in combination with methadone,nalbuphine or fentanyl for ulna osteotomy

ObjectiveTo compare the propofol infusion rate and cardiopulmonary effects during total intravenous anesthesia with propofol alone and propofol combined with methadone, fentanyl or nalbuphine in domestic chickens undergoing ulna osteotomy.Study designProspective, randomized, experiment trial.AnimalsA total of 59 healthy Hissex Brown chickens weighing 1.5 ± 0.2 kg.MethodsAnesthesia was induced with propofol (9 mg kg^–1) administered intravenously (IV) and maintained with propofol (1.2 mg kg^–1 minute^–1) for 30 minutes. Birds were intubated and supplemented with 100% oxygen through a nonrebreathing circuit under spontaneous ventilation. Thereafter, each animal was randomly assigned to one of four groups: group P, no treatment; group PM, methadone (6 mg kg^–1) intramuscularly (IM); group PN, nalbuphine IM (12.5 mg kg^–1); and group PF, fentanyl IV (30 μg kg^–1 loading dose, 30 μg kg^–1 hour^–1 constant rate infusion). During the osteotomy surgery, the propofol infusion rate was adjusted to avoid movement of birds and provide adequate anesthesia. Pulse rate, invasive blood pressure, respiratory frequency, end-tidal carbon dioxide partial pressure (Pe′CO₂) and hemoglobin oxygen saturation (SpO₂) were recorded.ResultsData were available from 58 chickens. The mean ± standard deviation propofol infusion rate (mg kg^–1 minute^–1) for the duration of anesthesia was: group P, 0.81 ± 0.15; group PM, 0.66 ± 0.11; group PN, 0.60 ± 0.14; and group PF, 0.80 ± 0.07. Significant differences were P versus PM (p = 0.042), P versus PN (p = 0.002) and PF versus PN (p = 0.004). Pulse rate, blood pressure and SpO₂ remained acceptable for anesthetized birds with minor differences among groups. Values of Pe′CO₂ >60 mmHg (8 kPa) were observed in all groups.Conclusions and clinical relevanceMethadone and nalbuphine, but not fentanyl, decreased the propofol infusion rate required for anesthesia maintenance, but resulted in no obvious benefit in physiological variables.     

Effects of two continuous infusion doses of lidocaine on isoflurane minimum anesthetic concentration in chickens

ObjectiveTo assess the effect of two intravenous (IV) doses of lidocaine on the minimum anesthetic concentration (MAC) of isoflurane in chickens.Study designBlinded, prospective, randomized, experimental crossover study.AnimalsA total of six adult female chickens weighing 1.90 ± 0.15 kg.MethodsChickens were anesthetized with isoflurane and mechanically ventilated. Isoflurane MAC values were determined (T0) in duplicate using an electrical noxious stimulus and the bracketing method. After MAC determination, a low dose (LD; 3 mg kg^–1 followed by 3 mg kg^–1 hour^–1) or high dose (HD; 6 mg kg^?1 followed by 6 mg kg^?1 hour^–1) of lidocaine was administered IV. MAC determination was repeated at 1.5 (T1.5) and 3 (T3) hours of lidocaine administration and blood was collected for analysis of plasma lidocaine and monoethylglycinexylidide (MEGX) concentrations. Pulse rate, peripheral hemoglobin oxygen saturation, noninvasive systolic arterial pressure and cloacal temperature were recorded at T0, T1.5 and T3. Treatments were separated by 1 week. Data were analyzed using mixed-effects model for repeated measures.ResultsMAC of isoflurane (mean ± standard deviation) at T0 was 1.47 ± 0.18%. MAC at T1.5 and T3 was 1.32 ± 0.27% and 1.26 ± 0.09% (treatment LD); and 1.28 ± 0.06% and 1.30 ± 0.06% (treatment HD). There were no significant differences between treatments or times. Maximum plasma lidocaine concentrations at T3 were 496 ± 98 and 1200 ± 286 ng mL^–1 for treatments LD and HD, respectively, and were not significantly different from T1.5. With treatment HD, plasma concentration of MEGX was significantly higher at T3 than at T1.5. Physiological variables were not significantly different among times with either treatment.Conclusions and clinical relevanceAdministration of lidocaine did not significantly change isoflurane MAC in chickens. Within treatments, plasma lidocaine concentrations were not significantly different at 1.5 and 3 hours.     

Intravenous regional anesthesia in isoflurane anesthetized cats: lidocaine plasma concentrations and cardiovascular effects

Objective To determine if intravenous regional anesthesia (IVRA) can be used in cats without resulting in excessive plasma lidocaine concentrations or adverse cardiovascular effects. Study design Prospective, blinded crossover study. Animals Seven healthy male young adult cats weighing 3.96 ± 0.63 kg. Methods At 2.3% end‐tidal isoflurane concentration, lidocaine (L) 3 mg kg^?1 (1%) or saline (S) was injected in a distal cephalic venous catheter after application of two tourniquets to that forelimb which remained in place for 20 minutes. Heart and respiratory rates, arterial blood pressures and ECG were recorded every 5 minutes during tourniquet application and for 20 minutes following tourniquet removal. Lidocaine plasma concentrations were measured 5 minutes after injection and 0.5, 1, 2, 4, 8, 20 and 40 minutes after tourniquet removal. End tidal isoflurane concentrations were reduced to 1.5–2.0% to elicit a response to toe pinch (RTP) in the contralateral leg. The study was repeated similarly in the contralateral leg and RTP was graded for 40 minutes. Response was also tested in the leg previously injected, the differences between the two scores determined and those differences compared between the L and S treatments. The data were analyzed using anova for repeated measures comparing values to baseline. Significance was set at p < 0.005 using the Bonferroni method for multiple comparisons. Results There were no significant differences in physiologic parameters at either isoflurane concentration. Differences in RTP were significantly larger in the lidocaine treatment. The highest mean lidocaine concentrations were measured 0.5 minutes after tourniquet removal after both injections and were 2.79 ± 1.05 and 3.10 ± 1.11 µg mL^?1. The highest individual plasma concentration was 6.46 µg mL^?1. Conclusion No adverse hemodynamic effects were evident after IVRA lidocaine in any cat. The lidocaine dose studied inhibited a RTP until 20 minutes after tourniquet removal. Lidocaine concentrations varied and were measurable prior to tourniquet removal. Clinical relevance IVRA may be a suitable technique for cats undergoing surgery of the distal limbs.     

Cardiovascular effects of a continuous rate infusion of lidocaine in calves anesthetized with xylazine,midazolam, ketamine and isoflurane

ObjectiveTo assess the cardiovascular changes of a continuous rate infusion of lidocaine in calves anesthetized with xylazine, midazolam, ketamine and isoflurane during mechanical ventilation.Study designProspective, randomized, cross-over, experimental trial.AnimalsA total of eight, healthy, male Holstein calves, aged 10 ± 1 months and weighing 114 ± 11 kg were included in the study.MethodsCalves were administered xylazine followed by ketamine and midazolam, orotracheal intubation and maintenance on isoflurane (1.3%) using mechanical ventilation. Forty minutes after induction, lidocaine (2 mg kg^?1 bolus) or an equivalent volume of saline (0.9%) was administered IV followed by a continuous rate infusion (100 μg kg^?1 minute^?1) of lidocaine (treatment L) or saline (treatment C). Heart rate (HR), systolic, diastolic and mean arterial pressures (SAP, DAP and MAP), central venous pressure (CVP), mean pulmonary arterial pressure (mPAP), pulmonary arterial occlusion pressure (PAOP), cardiac output, end-tidal carbon dioxide (Pe’CO₂) and core temperature (CT) were recorded before lidocaine or saline administration (Baseline) and at 20-minute intervals (T20-T80). Plasma concentrations of lidocaine were measured in treatment L.ResultsThe HR was significantly lower in treatment L compared with treatment C. There was no difference between the treatments with regards to SAP, DAP, MAP and SVRI. CI was significantly lower at T60 in treatment L when compared with treatment C. PAOP and CVP increased significantly at all times compared with Baseline in treatment L. There was no significant difference between times within each treatment and between treatments with regards to other measured variables. Plasma concentrations of lidocaine ranged from 1.85 to 2.06 μg mL^?1 during the CRI.Conclusion and clinical relevanceAt the studied rate, lidocaine causes a decrease in heart rate which is unlikely to be of clinical significance in healthy animals, but could be a concern in compromised animals.     

Effects of thoracolumbar epidural anesthesia with lidocaine on the systemic hemodynamics and hepatic blood flow in propofol anesthetized dogs

General anesthesia reduces hepatic blood flow (HBF) from circulatory depression. Total intravenous anesthesia (TIVA) is associated with decreased circulatory depression compared to inhalation anesthesia, and epidural anesthesia using local anesthetics increases blood flow by blocking the sympathetic nerves and expanding blood vessels. We investigated the effects of thoracolumbar epidural anesthesia with TIVA on HBF in dogs. Six Beagle dogs had epidural catheters placed between T13 and L1 and were anesthetized with propofol and vecuronium. Physiological saline (control) or 2% lidocaine (0.2 ml/kg, followed by 0.2 ml/kg/hr) was administered at 1–2 weeks intervals. Heart rate (HR), cardiac index (CI), mean arterial pressure (MAP), and systemic vascular resistance index (SVRI) were recorded at 10-min intervals from before epidural injections (T0) to 110 min. Indocyanine green test was used to measure HBF during the awake state and until 90 min after epidural injections. HR and CI did not differ between treatments. MAP and SVRI after lidocaine were significantly lower than those of controls, and the lowest MAP value was 65 ± 11 mmHg at T10. Compared to T0, after lidocaine treatment, HBF was significantly higher at T30, T60 and T90 (P<0.05); while, after control treatment, no significant change was evident at any time point. Despite a decrease in MAP by this technique, HBF was either maintained at pre-anesthetic levels or increased in comparison to controls, probably due to vasodilation of the hepatic artery induced by the selective blockade sympathetic ganglia.     

Prenatal exposure to corticosterone impairs embryonic development and increases fluctuating asymmetry in chickens (Gallus gallus domesticus)

1. The level of corticosterone in fertilised eggs from hens (Gallus gallus domesticus) was manipulated experimentally to elucidate whether stress in laying hens is harmful to the chicks, as manifested by impaired survival and reduced growth, and whether bilateral asymmetry may represent an indicator of environmental stress in poultry. 2. Three hundred and fifty eggs were randomly divided into 4 groups; 1. untreated, 2. control, 3. 10 ng corticosterone/ml and 4. 20 ng corticosterone/ml. Each of the eggs in groups 2, 3 and 4 were injected with 100 microl ethanol-saline solution (25% ethanol in saline) containing 0, 0.6 and 1.2 microg corticosterone, respectively. After the injections, the final concentration of ethanol in the egg (albumen and yolk) was 0.03%, and the concentration of added corticosterone was 0, 10 and 20 ng/ml, respectively, in groups 2, 3 and 4. All the eggs were treated on developmental d 1. 3. Corticosterone injections resulted in greater embryonic mortality, earlier termination of foetal development and reduced growth. Moreover, chicks developing in eggs with an elevated concentration of corticosterone displayed reduced developmental stability as evidenced by increased fluctuating asymmetry (FA) in tarsus length. 4. In conclusion, an increased concentration of corticosterone in the egg was detrimental to survival and growth of the chicks. Prenatal stress also generated bilateral asymmetry, and illustrates the potential application of FA as an indicator of environmental stress in poultry.     

Ontogeny of brain temperature regulation in chicks (Gallus gallus domesticus)

1. Development of brain temperature regulation was studied in the domestic fowl (Gallus gallus domesticus) from hatching to 21 d of age. 2. Body and brain temperature at hatching were relatively low compared with adult levels. However, both were effectively regulated at ambient temperatures of 30 and 35 degrees C, with only a minor difference between the 2 temperatures. 3. Body and brain temperature increased as a power function of age at significantly different rates, approaching adult levels at around 10 d of age and resulting in a linear increase in body-to-brain temperature difference with age. 4. The results indicated the existence of different patterns of post-hatching development of brain temperature regulation in relation to the degree of precocity of a species.     

Evaluation of lidocaine for brachial plexus blockade in eastern box turtles (Terrapene carolina carolina)

ObjectiveTo evaluate latency and duration of a brachial plexus block technique in eastern box turtles performed with 2% lidocaine at three dose rates.Study designProspective, randomized, blinded crossover study.AnimalsAdult eastern box turtles, two for drug dose evaluation and a group of six (three male, three female) weighing 432 ± 40 g (mean ± standard deviation) for the main study.MethodsAnimals were randomly assigned to four brachial plexus blocks with lidocaine at 5, 10 and 20 mg kg^–1 or 0.9% saline (treatments LID5, LID10, LID20 and CON, respectively), separated by 1 week. Treatment side was randomized and blocks were performed unilaterally. Baseline observations of mentation, heart rate (HR), respiratory rate (f_R), skin temperature and limb response to manipulation or toe pinch were evaluated. Assessments were made every 10 minutes until 1 hour of normal sensory and motor function to the treated thoracic limb, or for a total of 2 hours if no block was evident.ResultsMotor and sensory blockade was achieved in treatments LID10 and LID20 in one turtle, with a latency of 10 minutes and duration of 50 minutes for both doses. Raising of the ipsilateral lower palpebra occurred with both blocks. Turtles administered lidocaine experienced higher HR compared with CON, and HR decreased over time for all individuals. Mentation and f_R were not changed with any lidocaine dose.ConclusionsThe technique was unreliable in producing brachial plexus motor and sensory blockade at the lidocaine doses evaluated in this study. HR was higher in lidocaine-administered turtles but remained within normal limits for the species. No change in mentation or f_R was observed among treatments.Clinical relevanceGeneral anesthesia with systemic analgesia is recommended for surgical procedures involving the chelonian thoracic limb. Further studies are needed to optimize a brachial plexus block in this species.     

Use of intravenous lidocaine to treat dexmedetomidine-induced bradycardia in sedated and anesthetized dogs

ObjectiveTo assess cardiopulmonary function in sedated and anesthetized dogs administered intravenous (IV) dexmedetomidine and subsequently administered IV lidocaine to treat dexmedetomidine-induced bradycardia.Study designProspective, randomized, crossover experimental trial.AnimalsA total of six purpose-bred female Beagle dogs, weighing 9.1 ± 0.6 kg (mean ± standard deviation).MethodsDogs were randomly assigned to one of three treatments: dexmedetomidine (10 μg kg^–1 IV) administered to conscious (treatments SED1 and SED2) or isoflurane-anesthetized dogs (end-tidal isoflurane concentration 1.19 ± 0.04%; treatment ISO). After 30 minutes, a lidocaine bolus (2 mg kg^–1) IV was administered in treatments SED1 and ISO, followed 20 minutes later by a second bolus (2 mg kg^–1) and a 30 minute lidocaine constant rate infusion (L-CRI) at 50 (SED1) or 100 μg kg^–1 minute^–1 (ISO). In SED2, lidocaine bolus and L-CRI (50 μg kg^–1 minute^–1) were administered 5 minutes after dexmedetomidine. Cardiopulmonary measurements were obtained after dexmedetomidine, after lidocaine bolus, during L-CRI and 30 minutes after discontinuing L-CRI. A mixed linear model was used for comparisons within treatments (p < 0.05).ResultsWhen administered after a bolus of dexmedetomidine, lidocaine bolus and L-CRI significantly increased heart rate and cardiac index, decreased mean blood pressure, systemic vascular resistance index and oxygen extraction ratio, and did not affect stroke volume index in all treatments.Conclusion and clinical relevanceLidocaine was an effective treatment for dexmedetomidine-induced bradycardia in healthy research dogs.     

Baroreceptor control of heart rate in chickens (Gallus domesticus)

The baroreceptor control of heart rate was examined in nonanesthetized, nonrestrained, White Leghorn chickens (n = 10) by measuring the heart period response to modest increases in systolic blood pressure induced by IV boluses of phenylephrine (0.04 micrograms/g). In each animal, a sciatic artery and a femoral vein were chronically instrumented for the measurement of blood pressure and heart rate, together with venous access. Sustained and consistent cardiac slowing was seen in all chickens in response to small increases in systolic pressure. The mean slope of the regression equation between heart period and systolic pressure was 13.9 +/- 0.8 s X 10(-4)/mm of Hg. This sensitivity was reduced to 2.1 +/- 1.5 s X 10(-4)/mm of Hg by anesthetizing the chickens with isoflurane (inspired concentrations of 1%).     

Cardiovascular effects of dose escalating of norepinephrine in healthy dogs anesthetized with isoflurane

ObjectiveTo evaluate the systemic cardiovascular effects of dose escalating administration of norepinephrine in healthy dogs anesthetized with isoflurane.Study designExperimental study.AnimalsA total of six adult laboratory Beagle dogs, 10.5 (9.2–12.0) kg [median (range)].MethodsEach dog was anesthetized with isoflurane at an end-tidal concentration of 1.7%, mechanically ventilated and administered a continuous rate infusion of rocuronium (0.5 mg kg^–1 hour^–1). Each dog was administered incremental dose rates of norepinephrine (0.05, 0.125, 0.25, 0.5, 1.0 and 2.0 μg kg^–1 minute^–1), and each dose was infused for 15 minutes. Cardiovascular variables were recorded before administration and at the end of each infusion period.ResultsNorepinephrine infusion increased mean arterial pressure (MAP), cardiac output (CO) and oxygen delivery in a dose-dependent manner. Systemic vascular resistance did not significantly change during the experiment. Stroke volume increased at the lower dose rates and heart rate increased at the higher dose rates. Oxygen consumption and lactate concentrations did not significantly change during infusions.ConclusionsIn dogs anesthetized with isoflurane, norepinephrine increased MAP by increasing the CO. CO increased with a change in stroke volume at lower dose rates of norepinephrine. At higher dosage, heart rate also contributed to an increase in CO. Norepinephrine did not cause excessive vasoconstriction that interfered with the CO during this study.Clinical relevanceNorepinephrine can be useful for treating hypotension in dogs anesthetized with isoflurane.     

The use of eutectic mixture of lidocaine and prilocaine in mice (Mus musculus) for tail vein injections

ObjectiveTo investigate a topical local anesthesia technique as a means to prevent and/or diminish pain in mice in a laboratory setting associated with tail vein injections performed by personnel in training.Study designProspective, randomized experimental trial.AnimalsThirty six adult female, 23–28 g CD-1 mice from an in-house training colony. They were acclimated to routine training and handling classes.MethodsEutectic mixture of local anesthetics (EMLA) cream (2.5% lidocaine/2.5% prilocaine) or a bland ointment control (n = 18) was applied on the tail prior to intravenous injection. The injections were performed by novices, who had never attempted the procedure, and experienced personnel. All participants were blinded to treatment groups. Three injection attempts were allowed per animal. The mice were observed and scored by blinded evaluators for behavioral and physiological changes, including respiratory rate, vocalization, tail flick, and escape behaviors, during and after the injection.ResultsThis study demonstrates that aversive behaviors induced by lateral tail vein injection were not changed by the preemptive application of EMLA cream. The aversive behaviors associated with lateral tail vein injection were significantly affected by the number of injection attempts and the individual's experience level.Conclusions and clinical relevanceTopical EMLA cream did not reduce signs of aversive reaction to tail vein injection and thus we did not find support for its use in mouse training programs for tail vein injections.