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.

Sevoflurane Sparing Effect of Morphine in Tegus (Salvator merianae) - A Preliminary Study.

This study aimed to determine the minimum anesthetic concentration (MAC) of sevoflurane in tegus (Salvator merianae) and the morphine-sparing effect on this variable. In a prospective, non-blinded, crossover study, MAC was first determined in 6 tegus under sevoflurane anesthesia alone (MACSEVO) and then following intramuscular administration of morphine (10 mg/kg), administered 3 hour before sevoflurane anesthesia (MACSEVO+MOR). A standard bracketing technique was applied to determine the MAC by an electrical supramaximal noxious stimulus (50 Hz, 30 mA) delivered at the base of the tail of the tegus. The end-tidal sevoflurane fraction was reduced or increased by 10% in any evidence of negative or positive motor responses, respectively. The MAC was calculated as the mean of the 2 highest successive sevoflurane concentrations that permitted positive responses and the 2 lowest that prevented positive responses. Heart rate, esophageal temperature, and noninvasive mean arterial blood pressure were assessed every 10 minutes. The MAC was significantly different between MACSEVO (2.41 ± 0.06%) and MACSEVO+MORF (1.88 ± 0.43%) (P = .007), with a mean ± SD morphine-induced reduction in the sevoflurane MAC of 22 ± 18% (P = .0158). Heart rate, mean arterial blood pressure, and esophageal temperature did not differ between groups or within groups over time. Results showed that intramuscular premedication with 10 mg/kg morphine produced a sevoflurane sparing effect in tegus with no significant impact on cardiovascular variables.

Intracoelomic pressure and coelomic perfusion pressure in healthy tegus (Salvator merianae) / Mensuração da pressão intracelomática e da pressã de perfusão celomática em teiús saudáveis (Salvator merianae)

ABSTRACT: The evaluation of intracoelomic pressure is very important, as many diseases can culminate with an increase in intracoelomic pressure and a consequent reduction in perfusion of the abdominal organs. The aim of this study was to measure the intracoelomic pressure and coelomic perfusion pressure in tegus (Salvator merianae). Twelve healthy tegus without sexual distinctions, weighing 1.64±0.39kg, were enrolled in this study. Intracoelomic pressure was measured using two methods: a handmade water column system and a pressure transducer connected to a multiparameter monitor. Coelomic perfusion pressure was determined by subtracting the intracoelomic pressure from the mean arterial pressure, which was measured using an oscillometric method. Intracoelomic pressure was 0mmHg (range, 0 - 0.5) according to the water column method and 2mmHg (range, 0 - 2.0) according to the pressure transducer. Coelomic perfusion pressure was 76mmHg (range, 62 - 105) according to the water column system and 82mmHg (range, 57 - 93) according to the pressure transducer. No significant difference was observed between the values obtained by the different measurement methods. Intracoelomic pressure value reported in this study might be useful in tegus, but the coelomic perfusion pressure should be used with caution, considering the blood pressure method that was used.

RESUMO: A pressão intracelomática é um importante parâmetro, uma vez que muitas doenças culminam com o aumento da pressão intracelomática e consequentemente na redução da perfusão dos órgãos abdominais. O objetivo do estudo foi mensurar a pressão intracelomática e a pressão de perfusão celomática em teiús. Foram utilizados doze teiús hígidos, sem distinção sexual, pesando 1,64±0,39kg. A pressão intracelomática foi determinada pelo sistema de coluna de água e por um transdutor de pressão conectado a um monitor multiparamétrico. Já a pressão de perfusão celomática foi determinada pela subtração da pressão intracelomática do valor da pressão arterial média, sendo este obtido pelo método oscilométrico com o manguito posicionado na base da cauda. A pressão intracelomática mensurada pelo sistema de coluna de água foi 0mmHg [0 - 0,5] e pelo transdutor de pressão foi 2mmHg [0 - 2,0]. A pressão de perfusão celomática obtida pelo sistema de coluna de água foi 76mmHg [62 - 105] e pelo transdutor de pressão foi 82mmHg [57 - 93]. Não foram detectadas diferenças estatísticas entre os métodos de mensuração. Os valores de pressão intracelomática obtidos podem ser úteis para avaliação clínica em teiús, mas os valores de pressão de perfusão celomática devem ser utilizados com cautela, a considerar o método de mensuração da pressão arterial.

Minimum alveolar concentration of isoflurane in dogs administered two morphine doses / Concentração alveolar mínima do isoflurano em cães tratados com duas doses de morfina

ABSTRACT: This study aimed to evaluate the effects of intramuscular 0.5mg kg-1 (MOR0.5) and 1.0mg kg-1 (MOR1.0) morphine premedication on the minimum alveolar concentration of isoflurane (ISOMAC) in dogs. Eighteen client-owned female dogs were scheduled for elective ovariohysterectomy. Dogs received intramuscular MOR0.5 or MOR1.0 as premedication and propofol IV for induction of anesthesia. Isoflurane was delivered for maintenance of anesthesia and dogs were maintained under normocapnia and normothermia. Determinations of the ISOMAC were conducted by use of the "up-and-down" method. Noxious stimulus (placement of Backhaus towel clamps, a midline skin incision and subcutaneous tissue dissection) was delivered approximately 50 minutes after premedication with MOR0.5 or MOR1.0. The calculated ISOMAC was 0.98±0.15% in MOR0.5 and 0.80±0.08% in MOR1.0. The ISOMAC was significantly lower in MOR1.0 compared with MOR0.5 (P=0.010). Results of this study suggested that intramuscular premedication with morphine 0.5 and 1.0mg kg-1 decreases the ISOMAC in a dose-related manner in dogs.

RESUMO: O presente estudo objetivou avaliar os efeitos da administração intramuscular de 0,5mg kg-1 (MOR0,5) ou 1,0mg kg-1 (MOR1,0) de morfina sobre a concentração alveolar mínima do isoflurano (CAMISO) em cães. Dezoito cadelas de proprietários foram agendadas para ovário-histerectomia eletiva. As cadelas receberam MOR0,5 ou MOR1,0, como medicação pré-anestésica, e propofol IV para indução da anestesia. A manutenção da anestesia foi realizada com isoflurano em condições de normocapnia a normotermia. A determinação da CAMISO foi conduzida de acordo com o método "up-and-down". O estímulo nociceptivo (colocação de pinças Backhaus, incisão da pele na linha média e dissecção de tecido subcutâneo) foi realizado aproximadamente 50 minutos após a administração de MOR0,5 ou MOR1,0. A CAMISO calculada foi 0,98±0,15% em MOR0,5 e 0,80±0,08% em MOR1,0. A CAMISO foi significativamente menor em MOR1,0 do que em MOR0,5 (P=0,010). Os resultados do estudo sugerem que a medicação pré-anestésica com morfina nas doses de 0,5 e 1,0mg kg-1, pela via intramuscular, resulta em redução dose-dependente na CAMISO em cães.

Efeitos hemodinâmicos da anestesia em plano profundo com infusão intravenosa contínua de propofol ou propofol associado à lidocaína em cães / Hemodynamic effects of deep anesthesia with a constant rate infusion of propopol or propofol combined with lidocaine in dogs

Os efeitos hemodinâmicos da anestesia total intravenosa com propofol ou propofol associado à lidocaína foram estudados em 12 cães. No grupo P (n=6), os animais receberam bolus de 6mg kg-1 de propofol e infusão contínua de 1,25mg kg-1 min-1. No grupo PL (n=6), os animais receberam bolus de 6mg kg-1 de propofol e 1,5mg kg-1 de lidocaína, seguido de infusão de 1,0mg kg-1 min-1 e 0,25mg kg-1 min-1, dos mesmos fármacos, respectivamente. Os animais foram instrumentados para mensuração das variáveis hemodinâmicas e do índice bispectral (BIS), aos 75, 90, 105 e 120 minutos de anestesia. Foram observados valores menores de índice cardíaco, índice sistólico, pressões arteriais sistólica, diastólica e média no grupo P do que no grupo PL (P<0,05). Não foram observadas diferenças entre os grupos na frequência cardíaca, índice de resistência vascular sistêmica e BIS. As concentrações plasmáticas de propofol foram menores no grupo PL do que no grupo P (medianas de 5,7 a 6,1µg mL-1 no grupo P versus 3,1 a 3,7µg mL-1 no grupo PL). As concentrações plasmáticas de lidocaína (medianas de 2,27 a 2,51µg mL-1) mensuradas encontram-se na faixa que resulta em analgesia e abaixo de valores que resultam em toxicidade em cães. Os valores de BIS obtidos nos dois grupos foram compatíveis com plano profundo de anestesia (médias de 43 a 46 e 45 a 49 nos grupos P e PL, respectivamente). A manutenção da anestesia em plano profundo com lidocaína-propofol causa menor depressão cardiovascular do que a anestesia com dose equipotente de propofol isoladamente.

The hemodynamic effects of total intravenous anesthesia with propofol or propofol in combination with lidocaine were investigated in 12 dogs. In the P group (n=6), the dogs received a loading dose (LD) of 6mg kg-1 of propofol followed by a constant rate infusion (CRI) of 1.25mg kg-1 min-1. In the PL group (n=6), dogs received a LD of 6mg kg-1 of propofol and 1.5mg kg-1 of lidocaine followed by CRIs of 1.0mg kg-1 min-1 and 0.25mg kg-1 min-1 of propofol and lidocaine, respectively. The animals were instrumented for measurement of hemodynamic variables and bispectral index (BIS), recorded at 75, 90, 105 and 120 minutes during anesthesia. Cardiac index, stroke index, systolic, diastolic and mean arterial blood pressures were lower in the P group compared to the PL group (P<0.05). There were no significant differences between groups in heart rate, systemic vascular resistance index and BIS. Plasma concentrations of propofol were lower in group PL than in group P (medians of 5.7 to 6.1mg mL-1 in the P group versus 3.1 to 3.7mg mL-1 in the PL group). Measured lidocaine plasma concentrations (medians of 2.27 to 2.51mg mL-1) were in the range that result in analgesia and were below values that result in toxicity in dogs. The BIS values observed in the two groups of dogs were compatible with deep anesthesia (mean values of 43-46 and 45-49 in groups P and PL, respectively). Maintenance of deep anesthesia with lidocaine-propofol causes less cardiovascular depression than equipotent doses of propofol alone.