ABSTRACT PURPOSE: To evaluate the effects of dobutamine (DB), noradrenaline (NA), and their combination (NADB), on volume retention in rabbits submitted to hemorrhage. METHODS: Thirty six rabbits were randomly divided into 6 groups: SHAM, Control, Saline, DB, NA, DB+NA. All the animals, except for SHAM, were subjected to hemorrhage of 25% of the calculated blood volume. Control animals were replaced with their own blood. The other groups received NSS 3 times the volume withdrawn. The intravascular retention, hematocrit, diuresis, central venous pressure, mean arterial pressure, NGAL, dry-to-wet lung weight ratio (DTWR) and the lung and kidney histology were analyzed. RESULTS: Replacement with NSS and NA, DB or NA+DB did not produce differences in the intravascular retention. After hemorrhage, the animals presented a significant decrease in the MAP and CVP, which were maintained until volume replacement. Regarding NGAL, dry-to-wet-lung-weight ratio, lung and kidney histology, there were no statistical differences between the groups. CONCLUSION: The use of noradrenaline, dobutamine or their combination did not increase the intravascular retention of volume after normal saline infusion.

PURPOSE: To verify the effects of different catecholamines on volemic expansion and on the autonomic nervous system in rabbits that were subjected to hemorrhage.METHODS: Twenty four rabbits subjected to hemorrhage (with a 25% loss of blood volume) and were randomly divided into four experimental groups: 1) HEMO Group underwent replacement with their own blood in an equal volume; 2) SS Group underwent replacement with saline solution (SS) in a volume that corresponded to three times the removed blood volume; 3) ISP Group underwent replacement with SS and isoprenaline; 4) FNL Group underwent replacement with SS and phenylephrine. Spectral Analysis of the heart rate and heart rate variability were performed from the recorded data. Hematocrit was measured throughout the experiment.RESULTS:Replacement with SS and an α- or β-agonist did not produce differences in the intravascular retention compared to replacement with SS alone. An analysis of HRV showed that the FNL group maintained the LF/HF ratio better than ISP and SS.CONCLUSIONS: No difference in vascular retention when α- or β- agonists were added to SS during post-hemorrhagic recovery. The animals in the FNL group maintained the integrity of the autonomic response within normal physiological standards during hemorrhagic stress.

JUSTIFICATIVA E OBJETIVOS: O mecanismo de ação analgésica a2-adrenérgico tem sido explorado há mais de 100 anos. A clonidina aumenta de maneira dose-dependente a duração dos bloqueios sensitivo e motor e tem propriedades antinociceptivas. O objetivo desse estudo foi avaliar se a adição de clonidina na dose de 15 e 30 µg à raquianestesia, para cesariana, com bupivacaína hiperbárica a 0,5% (12,5 mg) e morfina (100 µg), melhora a qualidade da analgesia pós-operatória. MÉTODO: Foi realizado um estudo prospectivo e aleatório com 60 pacientes divididas em três grupos: BM - bupivacaína hiperbárica a 0,5% (12,5 mg) e morfina (100 µg), BM15 - bupivacaína hiperbárica a 0,5% (12,5 mg), morfina (100 µg) e clonidina (15 µg) e BM30 - bupivacaína hiperbárica a 0,5% (12,5 mg), morfina (100 µg) e clonidina (30 µg), administradas separadamente. No peri-operatório, foram anotados o consumo de efedrina e a avaliação do recém-nascido pelo índice de Apgar. No pós-operatório, a dor foi avaliada na 12ª h pela Escala Analógica Visual, o tempo para solicitação de analgésicos e efeitos colaterais pós-operatórios, como prurido, náuseas, vômitos, bradicardia, hipotensão arterial e sedação. Os valores foram considerados significativos quando p < 0,05. RESULTADOS: Os grupos foram homogêneos. O consumo de efedrina e a avaliação pelo índice de Apgar não exibiram diferença estatística significativa entre os grupos. Os escores de dor e o tempo médio de analgesia mostraram diferença entre os grupos BM e BM15/BM30 e não houve diferença com relação à incidência de efeitos colaterais pós-operatórios. CONCLUSÕES: A adição de clonidina na raquianestesia com bupivacaína hiperbárica a 0,5% (12,5 mg) e morfina (100 µg) para cesariana, melhorou a qualidade da analgesia pós-operatória, sem aumentar a incidência de efeitos colaterais, sendo 15 µg de clonidina a dose sugerida.

BACKGROUND AND OBJECTIVES: The mechanism of action of alpha2-adrenergic analgesia has been explored for more than one hundred years. The increased duration of the sensitive and motor blockades caused by clonidine is dose-dependent and has antinociceptive properties. The objective of this study was to evaluate whether the addition of 15 to 30 µg of clonidine to spinal anesthesia for cesarean sections with 0.5% hyperbaric bupivacaine (12.5 mg) and morphine (100 µg) improves the quality of postoperative analgesia. METHODS: We realized a prospective, randomized study that included 60 patients divided in 3 groups: BM - 0.5% hyperbaric bupivacaine (12.5 mg) and morphine (100 µg), BM15 - 0.5% hyperbaric bupivacaine (12.5 mg), morphine (100 µg), and clonidine (15 mg), and BM30 - 0.5% hyperbaric bupivacaine (12.5 mg), morphine (100 µg), and clonidine (30 µg), administered separately. In the perioperative period the use of ephedrine and the newborn's Apgar score were recorded. In the postoperative period, the pain was evaluated in the 12th h by the VAS, the length of time it took the patient to ask for analgesics, and the postoperative side effects, such as pruritus, nausea, vomiting, bradycardia, hypotension, and sedation. The values were considered significant when p < 0.05. RESULTS: The groups were homogenous. The use of ephedrine and the evaluation by the Apgar score did not show statistically significant differences among the different groups. The pain scores and the average time to start analgesia showed differences among the groups BM and BM15/BM30, and there were no differences regarding the incidence of postoperative side effects. CONCLUSIONS: The addition of clonidine to spinal anesthesia with 0.5% hyperbaric bupivacaine (12.5 mg) and morphine (100 µg) for cesarean section improved the quality of the postoperative analgesia without increasing the incidence of side effects. We suggest that the dose of 15 µg of clonidine should be used.

JUSTIFICATIVA Y OBJETIVOS: El mecanismo de acción analgésica alfa2-adrenérgico ha venido siendo investigado hace más de cien años. La clonidina aumenta de manera dosis-dependiente la duración de los bloqueos sensitivo y motor y tiene propiedades antinociceptivas. El objetivo de este estudio fue el de evaluar si la adición de clonidina en las dosis de 15 y 30 µg a raquianestesia, para cesárea, con bupivacaína hiperbárica a 0,5% (12,5 mg) y morfina (100 µg), mejora la calidad de la analgesia postoperatória. MÉTODO: Se realizó un estudio prospectivo, aleatorio con 60 pacientes y divididos en 3 grupos: BM - bupivacaína hiperbárica a 0,5% (12,5 mg) y morfina (100 µg), BM15 - bupivacaína hiperbárica a 0,5% (12,5 mg), morfina (100 µg) y clonidina (15 µg) y BM30 - bupivacaína hiperbárica a 0,5% (12,5 mg), morfina (100 µg) y clonidina (30 µg), administradas separadamente. En el perioperatorio, fueron anotados el consumo de efedrina y la evaluación del recién nacido por el índice de Apgar. En el postoperatório, el dolor se evaluó en la 12ª hora por la Escala Analógica Visual, el tiempo para la solicitación de analgésicos y efectos colaterales postoperatórios, como comezón, náuseas, vómitos, bradicardia, hipotensión arterial y sedación. Los valores fueron considerados significativos cuando p < 0,05. RESULTADOS: Los grupos fueron homogéneos. El consumo de efedrina y la evaluación por el índice de Apgar no exhibieron diferencia estadística significativa entre los grupos. Los rangos de dolor y tiempo promedio de analgesia indicaron una diferencia entre los grupos BM y BM15/BM30 y no hubo diferencia con relación a la incidencia de efectos colaterales postoperatórios. CONCLUSIONES: La adición de clonidina, la raquianestesia con bupivacaína hiperbárica a 0,5% (12,5 mg) y morfina (100 µg) para cesárea, mejoró la calidad de la analgesia postoperatória, sin aumentar la incidencia de efectos colaterales, siendo 15 µg de clonidina la dosis sugerida.