Induction and recovery characteristics and cardiopulmonary effects of sevoflurane and isoflurane in bald eagles

Minimum anesthetic concentration of isoflurane and sevoflurane and cardiorespiratory effects of varying inspired oxygen fractions in Magellanic penguins (Spheniscus magellanicus)

The aim of this study was to determine the minimum anesthetic concentration of isoflurane (MACISO) and sevoflurane (MACSEVO) and evaluate the cardiorespiratory changes induced by varying fractions of inspired oxygen (FiO2) in Magellanic penguins (Spheniscus magellanicus). Twenty adult penguins (3.53 ± 0.44 kg) of undetermined sex were used. Both MACISO (n = 9) and MACSEVO (n = 13) were established using an up-and-down design. Next, twelve mechanically ventilated penguins were maintained at 1 MACISO or 1 MACSEVO (n = 6 per group) with the FiO2 initially set at 1.0. Three FiO2 values (0.6, 0.4 and 0.2) were then held constant during anesthesia for 20 minutes each. Arterial blood samples were collected for gas analysis after the 20-minute period for each FiO2. Mean ± SD MACISO was 1.93 ± 0.10% and MACSEVO was 3.53 ± 0.13%. Other than heart rate at 0.6 FiO2 (86 ± 11 beats/minute in MACISO and 132 ± 37 beats/minute in MACSEVO; p = 0.041), no significant cardiorespiratory differences were detected between groups. In both groups, decreasing the FiO2 produced increased pH values and reduced partial pressures of carbon dioxide and bicarbonate. Partial pressures of oxygen (PaO2) gradually lowered from 1.0 FiO2 through 0.2 FiO2, though hypoxemia (PaO2 < 80 mmHg) occurred only with the latter FiO2. The MACISO and the MACSEVO for the Magellanic penguin fell within the upper range of reported avian MAC estimates. To prevent hypoxemia in healthy, mechanically ventilated, either isoflurane- or sevoflurane-anesthetized Magellanic penguins, a minimum FiO2 of 0.4 should be used.

Raptor Sedation and Anesthesia

Sedation and/or anesthesia is routinely and successfully used in raptors for a wide variety of procedures from the routine such as physical examination, radiographs, or venipuncture, to the more complex, such as orthopedic surgeries. Understanding the anatomy and physiology of raptor patients who present for care, and being fully prepared before the start of any procedure, can increase the success of anesthetic procedures. Recent advances in raptor sedation and anesthesia continue to improve the health and welfare of these avian patients.

Backyard Poultry and Waterfowl Sedation and Anesthesia

The popularity of backyard poultry (chickens, turkey, guinea fowl) and waterfowl (ducks and geese) is increasing in the United States, and these animals frequently present for veterinary care. Like other birds, these species have unique anatomy that should be clinically considered before anesthesia. A balanced approach to an injectable, inhalational, or combination anesthesia protocol must be taken to ensure a safe outcome for the patient and to achieve the procedural needs. A well-informed clinician may use both sedation and general anesthesia to care for backyard bird patients in practice.

Transvenous occlusion of patent ductus arteriosus in a domestic chicken (Gallus gallus)

A 2.5-year-old intact female Marans domestic chicken was presented for lethargy, open beak breathing, and hyporexia. Echocardiography noted left atrial and left ventricular enlargement and computed tomography angiography revealed a type III left-sided patent ductus arteriosus. Retrograde catheterization of the ductus was performed via percutaneous access of the right external jugular vein, and transvenous ductal occlusion was achieved using an 8-mm Amplatzer™ Vascular Plug 4. Transient bradycardia and hypotension occurred during right heart catheterization, which were successfully treated with atropine and epinephrine. A two-week follow-up postoperative cardiac computed tomography scan confirmed appropriate placement of the occluder within the ductus, and echocardiography demonstrated reduced left heart size. The chicken showed an improvement in clinical signs and remains apparently well six months after the intervention. This report describes the computed tomographic findings of a patent ductus arteriosus in an avian species, minimally invasive transvenous closure of this congenital anomaly with a low-profile occlusion device, and the associated challenges and considerations specific to cardiac intervention in an avian patient.

Comparison of the Anesthetic Effects of Isoflurane and Sevoflurane Inhalation on the Cardiovascular System of the Common Buzzard (Buteo buteo)

The aim of this study was to compare the effects of isoflurane (ISO) and sevoflurane (SEVO) inhalation anesthesia on the cardiovascular system of the common buzzard (Buteo buteo). Fourteen common buzzards of unknown sex and age, weighing 700-900 g each, were used for the study. The buzzards were randomly divided into an ISO group and a SEVO group, each comprising 7 buzzards. The buzzards were then anesthetized by masked induction with either ISO or SEVO. After induction, all buzzards were intubated with a 2.5-mm-diameter uncuffed endotracheal tube. Anesthesia was maintained with 3% ISO or 4% SEVO in a 3 L/min flow of 100% oxygen. Before induction, immediately after induction, and at intervals of 5, 10, 15, 20, 25, and 30 min after the patients were induced, the heart rate, respiratory rate, and body temperature of the buzzards were recorded. In addition, before and during anesthesia, serum electrolytes (sodium, ionized calcium, and potassium), blood gas measurements (arterial pH, arterial partial pressure of carbon dioxide, arterial partial pressure of oxygen, bicarbonate concentration, and oxyhemoglobin saturation), and hematocrit values were evaluated in the blood samples taken from both the ISO and SEVO groups. A statistically significant decrease in body temperature was observed in both groups. A significant decrease in heart rate was observed in the ISO group. The increases in partial pressure of carbon dioxide and bicarbonate concentration were statistically significant in both groups. The effects of ISO and SEVO anesthesia on the cardiovascular and respiratory system in the buzzards were similar based on the results of this study.

Comparative evaluation of isoflurane and sevoflurane in avian patients

Background and Aim:

Literature comparing the use of isoflurane and sevoflurane inhalation anesthetic agents in birds is scarce. This study aimed to evaluate the comparison of isoflurane and sevoflurane during induction, maintenance, and recovery of anesthesia in avian patients.

Materials and Methods:

In this study, 24 injured avian patients (n=24) were selected randomly and divided into four groups during kite flying festival. In the present study, isoflurane and sevoflurane were used as induction and maintenance anesthetic agents, with and without butorphanol tartrate premedication agent in all the birds. Different physiological parameters were evaluated, namely, cloacal temperature (°F), heart rate (beats/min), respiratory rate (breaths/min), and SpO₂ (%) were recorded at 0, 10, 20 min, and at recovery time. The quality of anesthesia was assessed on the basis of induction time, quality of induction, production of analgesia, muscle relaxation, body reflexes, recovery time, quality of recovery, sitting, standing, and complete recovery time (CRT).

Results:

The mean±standard error value of induction time was 230.00±32.55, 280.00±25.29, 180.00±21.90, and 260.00±36.87 s, respectively, in Groups I, II, III, and IV. The feather plucking, pharyngeal, and toe pinching reflexes were noticed, when the birds were passing through the light plane of anesthesia during induction. Comparison of cloacal temperature at the time of recovery between Group-I versus Group-III revealed a significant difference (p<0.05). Comparison of mean respiratory rates at the time of recovery between Group-II versus Group-IV revealed a significant difference (p<0.05). Excellent quality of recovery was observed in all the groups of anesthetic protocols. Sitting, standing, and CRT were observed shortest in avian patients maintained with sevoflurane as compared to isoflurane.

Conclusion:

The quality of induction of anesthesia was rapid in avian patients when induced with sevoflurane as compared to isoflurane. Rapid onset of induction and recovery of anesthesia were found with sevoflurane followed by isoflurane. Induction and maintenance of anesthesia in avian patients with sevoflurane resulted in the lowest time required for sitting, standing, and CRT.

Advancements in Evidence-Based Anesthesia of Exotic Animals

Anesthesia and sedation of pet nondomestic species are often necessary for both invasive and noninvasive procedures. Even minimally invasive procedures can be stressful for small prey species that are not domesticated or acclimated to human contact and restraint. Recent advancements in evidence-based practice will continue to improve the field based on scientifically sound best practices and rely less on anecdotal recommendations. This article focuses on new scientific literature that has been published in the past 5 years. For ease of reading, the authors divide the article to highlight advances in anesthetic pharmacology and discoveries in anesthetic physiology and monitoring.

INTRAMUSCULAR EPINEPHRINE RESULTS IN REDUCED ANESTHETIC RECOVERY TIME IN AMERICAN ALLIGATORS (ALLIGATOR MISSISSIPPIENSIS) UNDERGOING ISOFLURANE ANESTHESIA

Inhalants are commonly used to anesthetize reptiles, but volatile anesthetics have been associated with prolonged recovery times. The objective of this study was to determine the effects of intramuscular (IM) epinephrine on anesthetic recovery times following isoflurane anesthesia in a population of subadult American alligators ( Alligator mississippiensis ). In this prospective randomized crossover study, five clinically healthy alligators were anesthetized for 90 min with the use of isoflurane. Alligators were randomly assigned into one of two treatment groups: Group E received IM epinephrine (0.1 mg/kg), and Group S received an equal volume of 0.9% saline administered after isoflurane was discontinued. Time from the end of inhalant administration to return of spontaneous ventilation, return of the palpebral reflex, movement in response to a standardized toe pinch, and spontaneous movement was recorded. The time of extubation was noted and occurred following the return of spontaneous ventilation and movement. Pulse rate, surface body temperature, and airway gases including expiratory and inspiratory isoflurane concentrations and end-tidal carbon dioxide were measured every 5 min throughout the study. The time from the end of anesthesia to extubation was significantly faster in Group E (51.2 ± 16.7 min) compared to Group S (107.4 ± 43.7 min). Pulse rate was significantly higher within the first 15 min following epinephrine injection compared to the saline group at these time points. Therefore, IM epinephrine administered at the end of general anesthesia can significantly hasten anesthetic recovery from isoflurane in alligators.

Physiological alteration, quality of anesthesia and economy of isoflurane in domestic chickens (Gallus domesticus)

Aim:

Aim of the study was to evaluate the effect of isoflurane anesthesia on physiological parameters, assessment of anesthetic qualities, and economy of use of isoflurane in domestic chickens (Gallus domesticus).

Materials and Methods:

In this study, 18 apparently healthy adult domestic chickens were selected randomly and divided into three groups. The birds were anesthetized by masked induction with isoflurane at a dose rate of 3.5%, 4%, and 5% and were maintained with 1.5%, 2%, and 2.5% isoflurane with oxygen by endotracheal intubation in Groups I, II, and III, respectively. Physiological parameters, viz., cloacal temperature, heart rate, and respiration rate were recorded at 0, 5, 10, 20, 30, 40, 50, and 60 min. The quality of anesthesia was assessed on the basis of induction time, induction behavior, quality of sedation, production of analgesia, degree of muscle relaxation, palpebral reflex, recovery time, and recovery behavior. The economy of anesthesia was calculated in terms of quantity of isoflurane utilized during 60 min of study. Statistical analysis was performed by analysis of variance, Duncan’s multiple range tests.

Results:

There was significant decrease (p<0.01) in physiological parameters such as in cloacal temperature, heart rate and respiration rate in the birds of all the groups from 0 to 60 min. The induction time was 5.83±0.33, 2.37±0.18, and 0.87±0.15 min, respectively, in Groups I, II, and III. Induction behavior was smooth in Group III, whereas mildly stormy in Group II and I. Quality of sedation was excellent in Group III, better in Group II as compared to Group I. Analgesia was moderate in Group III whereas poor in Group II and I. Degree of muscle relaxation was excellent in Group III, whereas good in Group I and II. Palpebral reflexes were absent in all the groups. Recovery time was 15.33±0.84, 18.83±0.94, and 26.50±0.85 in Groups I, II, and III respectively. Recovery behavior was smooth in birds of all the groups. The cost of the anesthesia was 158.22±1.04, 194.27±0.66, and 236.84±0.60 Indian National Rupee in Groups I, II, and III, respectively. Quantity of anesthesia utilized in each group was 7.62±0.05, 9.35±0.03, and 11.41±0.03 ml in Groups I, II, and III, respectively.

Conclusion:

The use of isoflurane at different concentration produces different level of physiological changes, quality of anesthesia and economy without causing any deleterious effect on the birds. The physiological parameters observed in this study can serve as reference values for the wild and endangered birds.

Influência de diferentes protocolos de contenção nosvalores do eletrocardiograma de macacos-da-noite (Aotus azarae infulatus)

RESUMO: Macacos-da-noite são muito susceptíveis ao estresse e por isso a contenção química ou física deve ser cuidadosamente avaliada antes de qualquer procedimento. Protocolos anestésicos podem alterar alguns parâmetros fisiológicos, sendo o eletrocardiograma (ECG) um exame muito utilizado para avaliação do ritmo e da frequência cardíaca. O objetivo deste estudo foi avaliar a influência de quatro diferentes protocolos de contenção sobre o ECG realizado em Aotus azarae infulatus. Para isso foram utilizados 10 animais, machos, adultos, submetidos à contenção com a associação tiletamina/zolazepam (TZ), isoflurano (ISO), associação cetamina e midazolam (CET) e contenção física (CF). Não foram observadas diferenças nos parâmetros de ondas e complexos obtidos no ECG em todos os grupos testados, no entanto, durante a avaliação do traçado os animais do grupo CF apresentaram uma quantidade maior de alterações. Concluiu-se que os protocolos de contenção utilizados não alteraram os valores do ECG e que não foi possível considerar o grupo CF como controle devido causar mais alterações do que todos os protocolos testados.

External Beam Radiation Therapy of Squamous Cell Carcinoma in the Beak of an African Grey Parrot (Psittacus timneh)

Squamous cell carcinoma has been reported in a variety of bird species, most commonly psittacine and gallinaceous birds. The long-term prognosis in nongallinaceous birds is generally poor if complete surgical excision is not possible. Squamous cell carcinoma of the rhinotheca was diagnosed in a 34-year-old timneh African grey parrot (Psittacus timneh) with a 2-year history of beak abnormalities. No evidence of metastasis or local invasion were found on results of radiographs or computed tomography scan. The bird was treated with surgical debulking and palliative megavoltage radiation therapy. After 4 radiation treatments, the affected tissue was necrotic and was debrided to reveal healthy granulation tissue. The bird died approximately 7 months after diagnosis and 4 months after cessation of radiation treatment. At the time of death, a small scab lesion remained at the left oral commissure, but no visible tumor regrowth was evident. A postmortem examination was not performed, however, and tumor recurrence could not be ruled out in this bird.

Cardiorespiratory dose-response relationship of isoflurane in Cinereous vulture (Aegypius monachus) during spontaneous ventilation

Anesthesia is an inevitably important component of diagnosis and treatments examining the health condition of wild animals. Not only does anesthesia become an essential tool in minimizing stress of the patients and providing an opportunity to deliver accurate and safe procedures, but it also ensures the safety of the medical crew members. This study was conducted to investigate the dose-response cardiorespiratory effects of isoflurane during spontaneous ventilation in ten cinereous vultures. Each bird was administered isoflurane at initial concentration of 1.0, 1.5, 2.0, 2.5 and 3.0 and then an end-tidal isoflurane concentrations (ETiso) of 1.0% for an equilibration period of 15 min in the given order. At the end of the equilibration period, the direct blood pressure (BP), heart rate (HR), respiratory rate (RR) and end tidal CO₂ partial pressure (P_ETCO₂) were recorded, and blood gas analysis was performed. Increasing isoflurane concentrations during spontaneous ventilation led to dose-dependent increases in HR and P_ETCO₂, with minimal changes in RR, decreased arterial BP and respiratory acidosis. Overall, isoflurane for anesthesia of spontaneously breathing cinereous vultures is a suitable choice for diagnostic or surgical procedures.

Anaesthesia with sevoflurane in pigeons: minimal anaesthetic concentration (MAC) determination and investigation of cardiorespiratory variables at 1 MAC

The objective of the study was to determine the minimal anaesthetic concentration (MAC) of sevoflurane (SEVO) in pigeons and investigate the effects of 1 MAC SEVO anaesthesia on cardiovascular and respiratory variables compared with the awake state. This is a prospective, experimental study. Animals were seven healthy adult pigeons. After acclimatisation to handling, heart rate (HR), heart rhythm, respiratory rate (fR), end-expired carbon dioxide tension (PE'CO2), inspired CO2 tension, indirect systolic arterial blood pressure (SAP) and cloacal temperature were measured to determine baseline, 'awake' values. Pigeons were then anaesthetised with SEVO and MAC was determined by the 'bracketing' method. The same variables were monitored during a 40 minute period at 1.0 MAC SEVO for each bird. Mean MAC was 3.0±0.6 per cent for SEVO. During maintenance of anaesthesia at 1.0 MAC, SAP decreased significantly (P<0.001) without any significant change in HR. Although PE'CO2 increased significantly (P=0.001) despite an increase in fR, awake PE'CO2 values were unexpectedly low. Sinus arrhythmias were detected in two birds under SEVO anaesthesia. The times to tracheal intubation and to recovery were 2.5±0.7 and 6.4±1.7 minutes, respectively. Recovery was rapid and uneventful in all birds. In conclusion, SEVO is suitable for anaesthesia in pigeons.

Cardiorespiratory parameters in the awake pigeon and during anaesthesia with isoflurane

OBJECTIVE

To determine baseline cardiovascular and respiratory variables in the awake pigeon, and to assess those variables during anaesthesia at the individual minimal anaesthetic concentration (MAC) of isoflurane during spontaneous breathing.

STUDY DESIGN

Prospective, experimental trial.

ANIMALS

Seven healthy adult pigeons weighing a mean ± standard deviation (SD) of 438 ± 38 g.

METHODS

Heart rate (HR), heart rhythm, respiratory rate (fR), end-expired carbon dioxide tension (Pe'CO2), indirect systolic arterial pressure (SAP) and cloacal temperature (T) were measured in birds in the awake state (after acclimatization to handling). Two weeks later, the pigeons were anaesthetized with isoflurane in order to determine their MAC and evaluate the same cardiovascular and respiratory variables during a further 40 minutes of isoflurane anaesthesia.

RESULTS

In the awake pigeon, mean ± SD HR, SAP, fR, Pe'CO2 and T were, respectively, 155 ± 28 beats minute(-1), 155 ± 21 mmHg, 34 ± 6 breaths minute(-1), 38 ± 8 mmHg (5.1 ± 1.1 kPa) and 41.8 ± 0.5 °C. Mean isoflurane MAC was 1.8 ± 0.4%. During maintenance of anaesthesia at MAC, although no significant decreases between values obtained in the awake and anaesthetized states emerged in HR or respiratory rate, significant decreases in SAP and cloacal temperature and an increase in Pe'CO2 were observed. No arrhythmia was identified in awake pigeons, whereas second- and third-degree atrioventricular blocks occurred under isoflurane.

CONCLUSIONS AND CLINICAL RELEVANCE

Isoflurane MAC in pigeons appeared to be higher than in other avian species. Isoflurane anaesthesia in pigeons resulted in hypercapnia, hypotension, mild hypothermia and second- and third-degree atrioventricular blocks.

Anesthesia with isoflurane and sevoflurane in the crested serpent eagle (Spilornis cheela hoya): minimum anesthetic concentration, physiological effects, hematocrit, plasma chemistry and behavioral effects

The initial goal of this study was to determine the minimum anesthetic concentration (MAC) for isoflurane (ISO) and sevoflurane (SEVO) for the crested serpent eagle. Next, we compared the anesthetic effects of each on the physiological effects, hematocrit, plasma chemistry values and behavior in spontaneously breathing captive adult crested serpent eagles. Sixteen eagles were randomly allocated to two groups for anesthesia with ISO (n=8) or SEVO (n=8). First, we measured the MAC values of ISO and SEVO, and four weeks later, we investigated the effect of each on the physiological effects, hematocrit (HCT) and plasma chemistry values. The MAC values of ISO and SEVO for crested serpent eagles were 1.46 ± 0.30 and 2.03 ± 0.32%, respectively. The results revealed no significant differences between the two anesthetics in induction time, while time of extubation to recovery was significantly shorter with SEVO. A time-related increase in end-tidal CO₂ and decreases in body temperature and respiratory rates were observed during anesthesia with each anesthetic. There were no significant differences between the effect of the two anesthetics on heart rate, hematocrit, plasma chemistry values or respiration, although each caused minor respiration depression. We concluded that SEVO is a more effective inhalant agent than ISO for use in eagles, showing the most rapidest induction and recovery from anesthesia.

Cardiorespiratory effects of isoflurane anesthesia in crested caracaras (Caracara plancus)

To evaluate the cardiorespiratory changes induced by isoflurane (ISO) anesthesia in the crested caracara (Caracara plancus), eight crested caracaras that weighed 1.0 kg (range 0.9-1.1 kg) were the subjects for the study. The birds were anesthetized by face mask with ISO for brachial artery catheterization. After recovery, anesthesia was re-induced and maintained with ISO with spontaneous ventilation. Electrocardiography, direct systolic arterial blood pressure (SAP), diastolic arterial blood pressure (DAP), mean arterial blood pressure (MAP), respiratory rate (RR), end-tidal carbon dioxide (P(ET)CO2), and cloacal temperature (T degrees C) were measured before induction (baseline, under physical restraint) and after 5, 10, 15, 20, 25, 30, 35, and 40 min of ISO anesthesia. Arterial blood samples were collected for blood gas analysis at baseline, 10, 25, and 40 min. No cardiac arrhythmias were observed in the present study. RR, SAP, DAP, MAP, T degrees C and pH decreased from baseline values, whereas arterial partial pressures of oxygen and carbon dioxide, bicarbonate concentration, and P(ET)CO2 were significantly higher than baseline. Apnea was not observed in any bird. ISO anesthesia is suitable for use in healthy members of this species despite the moderate cardiovascular and respiratory depression produced.

Some cardiopulmonary effects of sevoflurane in crested caracara (Caracara plancus)

OBJECTIVE

To evaluate the cardiorespiratory changes induced by sevoflurane (SEV) anesthesia in the crested caracara (Caracara plancus).

STUDY DESIGN

Prospective experimental trial.

ANIMALS

Eight crested caracaras (Caracara plancus) weighing 1.0 (0.9-1.1) kg were used for the study.

METHODS

The birds were anesthetized by face mask with isoflurane for brachial artery catheterization. After recovery, anesthesia was re-induced with 6% SEV via face mask. After induction, a noncuffed endotracheal tube was placed and anesthesia was maintained with SEV (3.5% end-tidal) in oxygen (1 L minute(-1)) using an Ayre's T-piece nonrebreathing circuit, with spontaneous ventilation. Electrocardiography (ECG), direct systolic, diastolic and mean arterial blood pressure (SAP, DAP, and MAP), respiratory rate (f(R)), end-tidal carbon dioxide (Pe'CO(2)), and cloacal temperature (T degrees C) were measured before induction (baseline - under physical restraint) and after 5, 10, 15, 20, 25, 30, 35 and 40 minutes of SEV anesthesia. Arterial blood samples were collected for gas analysis at baseline and then at 10, 25 and 40 minutes.

RESULTS

No ventricular arrhythmias were observed in the present study. Respiratory rate, SAP, DAP, MAP, T degrees C and pH decreased from pre-induction values, while arterial partial pressures of oxygen and carbon dioxide, bicarbonate concentration, and Pe'CO(2) were significantly higher than baseline. None of the birds were apneic.

CONCLUSION AND CLINICAL RELEVANCE

Sevoflurane anesthesia is suitable for use in healthy members of this species, despite the moderate cardiovascular and respiratory depression produced.