Derli Conceição Munhoz

Comparação entre os efeitos hemodinâmicos da intoxicação aguda com bupivacaína racêmica e a mistura com excesso enatiomérico de 50% (S75-R25): estudo experimental em cães

JUSTIFICATIVA Y OBJETIVOS: La bupivacaina racemica ha sido ampliamente utilizada en bloqueos locorregionales por la calidad y duracion de la anestesia proporcionada. Su toxicidad cardiovascular, sin embargo ya hace mucho tiempo preocupa a los anestesiologos y nuevas opciones han sido buscadas. Una de ellas es la utilizacion de su isomero levogiro que por una menor afinidad con los receptores de los canales de sodio de la celula cardiaca que seria menos cardiotoxico. En nuestro medio existe la presentacion que contiene un 75% del isomero levogiro y 25% del isomero dextrogiro, denominada mezcla con exceso enantiomerico de 50% (S75-R25). El objetivo de este estudio fue comparar en animales los efectos hemodinamicos de la intoxicacion aguda con bupivacaina racemica y con la mezcla S75-R25. METODO: Cuarenta y cuatro perros fueron anestesiados con pentobarbital, entubados y ventilados mecanicamente, siendo en seguida instalada la monitorizacion hemodinamica con cateter de Swan-Ganz y presion invasiva. Despues del periodo de reposo fueron divididos aleatoriamente en dos grupos de estudio encubierto, segun la intoxicacion con uno u otro agente en la dosis de 5 mg.kg-1. Los resultados hemodinamicos se recolectaron durante 30 minutos, tratados estadisticamente permitiendo la comparacion de la accion de los dos agentes. RESULTADOS: La mezcla S75-R25 causo mayores repercusiones hemodinamicas, particularmente, con importante disminucion de la presion arterial promedio, del indice cardiaco y del indice de trabajo del ventriculo izquierdo. CONCLUSIONES: Esos resultados se contraponen con los encontrados en humanos, cuando se utiliza el isomero levogiro puro, pero estan de acuerdo con estudios recientes en animales. Rebasar datos obtenidos en animales para seres humanos exige mucha cautela. Nuevos estudios se hacen necesarios en muestras mas abarcadoras y en grupos mas homogeneos.BACKGROUND AND OBJECTIVES Racemic bupivacaine has been widely used in locoregional anesthesia due to the quality and duration of its anesthetic action. However, its cardiovascular toxicity has worried anesthesiologists for a long time, and new options have been sought. One of them is the use of its levorotatory isomer that, due to a lesser affinity for the sodium channel receptors in the cardiac cell, would be less toxic. The presentation containing 75% of the levorotatory isomer and 25% of the dextrorotatory isomer, named 50% enantiomeric excess mixture (S75-R25), is available in our country. The objective of this study was to compare the hemodynamic effects of the acute intoxication with racemic bupivacaine and with the S75-R25 mixture in animals. METHODS Forty-four dogs were anesthetized with pentobarbital, intubated and placed on mechanical ventilation. Hemodynamic monitorization was accomplished with a Swan-Ganz catheter and intra-arterial blood pressure measurements. After a period of rest, they were randomly and blindly divided in two groups, according to the intoxication with either agent at a dose of 5 mg.Kg-1. Hemodynamic data were collected during 30 minutes and analyzed statically to allow for the comparison of both agents. RESULTS The mixture S75-R25 had more hemodynamic repercussions causing, especially, a significant reduction of the mean arterial pressure, cardiac index, and the left ventricle work index. CONCLUSIONS These results contradict those found in human beings regarding the pure levorotatory isomer, but confirm recent animal studies. One must be very careful when extrapolating animal data to human beings. Further studies involving larger samples and more homogeneous groups are necessary.

Influence of propofol and etomidate on rocuronium-induced euromuscular block: evaluation with acceleromyography

BACKGROUND AND OBJECTIVES Some hypnotics may interact with neuromuscular blockers and potentiate their effects. This study aimed at evaluating the influence of propofol and etomidate on rocuronium-induced neuromuscular block. METHODS Participated in this study 60 patients, physical status ASA I and II, scheduled for elective surgeries under general anesthesia, who were randomly distributed in two groups according to the hypnotic drug: Group I (propofol) and Group II (etomidate). All patients were premedicated with intramuscular midazolam (0.1 mg.kg-1), 30 minutes before surgery. Anesthesia was induced with propofol (2.5 mg.kg-1) or etomidate (0.3 mg.kg-1) preceded by alfentanil (50 microg.kg-1) and followed by rocuronium (0.6 mg.kg-1). Patients were ventilated under mask with 100% oxygen until achieving a decrease of 75% or more in the adductor pollicis muscle response amplitude. Neuromuscular function was monitored by accelerometry. The following parameters were evaluated: rocuronium onset (T1 <= 25%); time for complete neuromuscular block; neuromuscular block degree at tracheal intubation; tracheal intubation conditions and hemodynamic effects. RESULTS Complete rocuronium-induced neuromuscular block onset times (in seconds) were: Group I (48.20 +/- 10.85 s and 58.87 +/- 10.73 s) and Group II (51.20 +/- 13.80 s and 64.27 +/- 18.55 s). Neuromuscular block degree at tracheal intubation was: Group I (77.50%) and Group II (76.96%). Tracheal intubation conditions were satisfactory in 100% of Group I patients and in 83.33% of Group II patients. There has been a significant decrease in mean blood pressure, followed by an increase after hypnotic injection, in both groups. CONCLUSIONS Propofol and etomidate had a similar behavior regarding time for rocuronium-induced neuromuscular block and tracheal intubation conditions.JUSTIFICATIVA E OBJETIVOS: Alguns hipnoticos podem interagir com os bloqueadores neuromusculares (BNM) potencializando seus efeitos. O objetivo deste estudo foi avaliar a influencia do propofol e do etomidato sobre o bloqueio neuromuscular produzido pelo rocuronio. METODO: Foram incluidos no estudo 60 pacientes, estado fisico ASA I e II, submetidos a cirurgias eletivas sob anestesia geral, distribuidos aleatoriamente em dois grupos de acordo com o hipnotico empregado: Grupo I (propofol) e Grupo II (etomidato). Todos os pacientes receberam midazolam (0,1 mg.kg-1) por via muscular como medicacao pre-anestesica, 30 minutos antes da cirurgia. A inducao anestesica foi obtida com propofol (2,5 mg.kg-1) ou etomidato (0,3 mg.kg-1) precedido de alfentanil (50 µg.kg-1) e seguido de rocuronio (0,6 mg.kg-1). Os pacientes foram ventilados sob mascara com oxigenio a 100% ate a obtencao de reducao de 75% ou mais na amplitude da resposta do musculo adutor do polegar, quando foram realizadas as manobras de laringoscopia e intubacao traqueal. A funcao neuromuscular foi monitorizada com aceleromiografia. Foram avaliados: tempo de inicio de acao do rocuronio (T1 £ 25%); tempo para instalacao do bloqueio neuromuscular total; grau de bloqueio neuromuscular no momento da intubacao traqueal; condicoes de intubacao traqueal e repercussoes hemodinâmicas. RESULTADOS: Os tempos de inicio de acao e instalacao de bloqueio neuromuscular total (segundos) produzido pelo rocuronio foram: Grupo I (48,20 ± 10,85 s e 58,87 ± 10,73 s) e Grupo II (51,20 ± 13,80 s e 64,27 ± 18,55 s). O grau de bloqueio neuromuscular no momento da intubacao traqueal foi: Grupo I (77,50%) e Grupo II (76,96%). As condicoes de intubacao traqueal foram satisfatorias em 100% dos pacientes do Grupo I e em 83,33% no Grupo II. Nos dois grupos, apos a injecao do hipnotico, observou-se diminuicao significativa da pressao arterial media seguida de elevacao. CONCLUSOES: O propofol e o etomidato comportaram-se de maneira semelhante em relacao a instalacao do bloqueio neuromuscular e as condicoes de intubacao traqueal produzidos pelo rocuronio.

Influência do propofol e do etomidato no bloqueio neuromuscular produzido pelo rocurônio: avaliação pela aceleromiografia

BACKGROUND AND OBJECTIVES Some hypnotics may interact with neuromuscular blockers and potentiate their effects. This study aimed at evaluating the influence of propofol and etomidate on rocuronium-induced neuromuscular block. METHODS Participated in this study 60 patients, physical status ASA I and II, scheduled for elective surgeries under general anesthesia, who were randomly distributed in two groups according to the hypnotic drug: Group I (propofol) and Group II (etomidate). All patients were premedicated with intramuscular midazolam (0.1 mg.kg-1), 30 minutes before surgery. Anesthesia was induced with propofol (2.5 mg.kg-1) or etomidate (0.3 mg.kg-1) preceded by alfentanil (50 microg.kg-1) and followed by rocuronium (0.6 mg.kg-1). Patients were ventilated under mask with 100% oxygen until achieving a decrease of 75% or more in the adductor pollicis muscle response amplitude. Neuromuscular function was monitored by accelerometry. The following parameters were evaluated: rocuronium onset (T1 <= 25%); time for complete neuromuscular block; neuromuscular block degree at tracheal intubation; tracheal intubation conditions and hemodynamic effects. RESULTS Complete rocuronium-induced neuromuscular block onset times (in seconds) were: Group I (48.20 +/- 10.85 s and 58.87 +/- 10.73 s) and Group II (51.20 +/- 13.80 s and 64.27 +/- 18.55 s). Neuromuscular block degree at tracheal intubation was: Group I (77.50%) and Group II (76.96%). Tracheal intubation conditions were satisfactory in 100% of Group I patients and in 83.33% of Group II patients. There has been a significant decrease in mean blood pressure, followed by an increase after hypnotic injection, in both groups. CONCLUSIONS Propofol and etomidate had a similar behavior regarding time for rocuronium-induced neuromuscular block and tracheal intubation conditions.JUSTIFICATIVA E OBJETIVOS: Alguns hipnoticos podem interagir com os bloqueadores neuromusculares (BNM) potencializando seus efeitos. O objetivo deste estudo foi avaliar a influencia do propofol e do etomidato sobre o bloqueio neuromuscular produzido pelo rocuronio. METODO: Foram incluidos no estudo 60 pacientes, estado fisico ASA I e II, submetidos a cirurgias eletivas sob anestesia geral, distribuidos aleatoriamente em dois grupos de acordo com o hipnotico empregado: Grupo I (propofol) e Grupo II (etomidato). Todos os pacientes receberam midazolam (0,1 mg.kg-1) por via muscular como medicacao pre-anestesica, 30 minutos antes da cirurgia. A inducao anestesica foi obtida com propofol (2,5 mg.kg-1) ou etomidato (0,3 mg.kg-1) precedido de alfentanil (50 µg.kg-1) e seguido de rocuronio (0,6 mg.kg-1). Os pacientes foram ventilados sob mascara com oxigenio a 100% ate a obtencao de reducao de 75% ou mais na amplitude da resposta do musculo adutor do polegar, quando foram realizadas as manobras de laringoscopia e intubacao traqueal. A funcao neuromuscular foi monitorizada com aceleromiografia. Foram avaliados: tempo de inicio de acao do rocuronio (T1 £ 25%); tempo para instalacao do bloqueio neuromuscular total; grau de bloqueio neuromuscular no momento da intubacao traqueal; condicoes de intubacao traqueal e repercussoes hemodinâmicas. RESULTADOS: Os tempos de inicio de acao e instalacao de bloqueio neuromuscular total (segundos) produzido pelo rocuronio foram: Grupo I (48,20 ± 10,85 s e 58,87 ± 10,73 s) e Grupo II (51,20 ± 13,80 s e 64,27 ± 18,55 s). O grau de bloqueio neuromuscular no momento da intubacao traqueal foi: Grupo I (77,50%) e Grupo II (76,96%). As condicoes de intubacao traqueal foram satisfatorias em 100% dos pacientes do Grupo I e em 83,33% no Grupo II. Nos dois grupos, apos a injecao do hipnotico, observou-se diminuicao significativa da pressao arterial media seguida de elevacao. CONCLUSOES: O propofol e o etomidato comportaram-se de maneira semelhante em relacao a instalacao do bloqueio neuromuscular e as condicoes de intubacao traqueal produzidos pelo rocuronio.

Efeitos hemodinâmicos da oclusão da aorta durante anestesia inalatória com isoflurano e sevoflurano: estudo experimental em cães

BACKGROUND AND OBJECTIVES Aortic flow suppression and release during aortic procedures promote major hemodynamic disorders. This study aimed at evaluating these disorders in dogs anesthetized with isoflurane or sevoflurane. METHODS This study involved 41 dogs divided in two groups according to the anesthetic agent used for maintenance with 1 MAC: GI (n = 21) isoflurane; GS (n = 20) sevoflurane. Aorta was occluded by intra-arterial infra-diafragmatic cuff inflation for 30 minutes. Hemodynamic parameters were observed in moments M1 (control), M2 and M3, 15 and 30 minutes after aortic occlusion, M4 and M5, 15 and 30 minutes after cuff deflation. RESULTS During aortic occlusion there has been increased mean blood pressure (MBP), central venous pressure (CVP), pulmonary artery pressure (PAP), pulmonary capillary wedge pressure (PCWP) and systemic vascular resistance (SVR), without increase in pulmonary vascular resistance (PVR) and cardiac output (CO). CO was more stable with isoflurane as compared to sevoflurane where it has decreased after occlusion. Heart rate has initially decreased followed by increase during occlusion, being more expressive in GS as compared to GI, however without statistically significant difference between groups. Systolic volume was not importantly changed; left and right ventricular function have similarly increased after occlusion for both groups. With flow release, MBP, CVP, PAP, PCWP and SVR have decreased, and PVR has increased for both groups; ventricular function has abruptly decreased. CONCLUSIONS This study has shown that isoflurane is a better indication for such interventions for promoting less hemodynamic changes.JUSTIFICATIVA Y OBJETIVOS: La supresion del flujo aortico y su posterior liberacion en intervenciones quirurgicas de la aorta, ocasionan importantes disturbios hemodinamicos. El objetivo de este estudio fue el de evaluar esas alteraciones en perros anestesiados con isoflurano o sevoflurano. METODO: Se estudiaron 41 perros, divididos en dos grupos segun el anestesico empleado en el mantenimiento con 1 CAM: GI (n = 21) isoflurano; GS (n = 20) sevoflurano. Se realizo la oclusion aortica por insuflacion de globo intraarterial infradiafragmatico por 30 minutos. Los parametros hemodinamicos fueron observados en los momentos M1 (control), M2 y M3, 15 y 30 minutos despues de la oclusion aortica, M4 y M5, 15 y 30 minutos despues de la desinsuflacion del globo. RESULTADOS: Durante la oclusion de la aorta, se observo el aumento de la presion arterial promedio (PAM), de la presion venosa central (PVC), de la presion de arteria pulmonar (PAP), de la presion de capilar pulmonar (PCP) y de la resistencia vascular sistemica (RVS) sin aumento de la resistencia vascular pulmonar (RVP) y del debito cardiaco (DC). El DC se mantuvo mas estable con el isoflurano comparado al sevoflurano, con el cual presento disminucion despues de la oclusion. La frecuencia cardiaca tuvo disminucion inicial que despues aumento durante la oclusion, siendo en GS mas expresiva que en GI, sin embargo, sin diferencia significativa entre los grupos. El volumen sistolico no tuvo grandes alteraciones; el trabajo sistolico de los ventriculos izquierdo y derecho aumento despues de la oclusion de forma similar en los dos grupos. Con la liberacion del flujo PAM, PVC, PAP, PCP y RVS bajaron, la RVP aumento en los dos grupos; el trabajo ventricular disminuye abruptamente. CONCLUSIONES: El estudio demostro que el isoflurano es el mas indicado en esas intervenciones quirurgicas por causar menores alteraciones hemodinamicas.

Influence of stimulation frequency on rocuronium and pancuronium-induced neuromuscular block onset: acceleromyography evaluation

JUSTIFICATIVA E OBJETIVOS: Fatores relacionados ao paciente e ao bloqueador neuromuscular (BNM), assim como outros inerentes a monitorizacao da funcao neuromuscular podem influenciar na instalacao do bloqueio neuromuscular. O objetivo deste estudo foi avaliar a influencia de duas diferentes frequencias de estimulos sobre o tempo de instalacao do bloqueio produzido pelo pancuronio e pelo rocuronio. METODO: Foram incluidos no estudo 120 pacientes, estado fisico ASA I e II, submetidos a cirurgias eletivas sob anestesia geral, distribuidos aleatoriamente em dois grupos, de acordo com a frequencia de estimulo empregada, para a monitorizacao do bloqueio neuromuscular: Grupo I - 0,1 Hz (n = 60) e Grupo II - 1 Hz (n = 60). Em cada grupo formaram-se dois subgrupos (n = 30) de acordo com o bloqueador neuromuscular empregado: Subgrupo P (pancuronio) e Subgrupo R (rocuronio). A medicacao pre-anestesica consistiu de midazolam (0,1 mg.kg-1) por via muscular, 30 minutos antes da cirurgia. A inducao anestesica foi obtida com propofol (2,5 mg.kg-1) precedido de alfentanil (50 µg.kg-1) e seguido de pancuronio ou rocuronio. Os pacientes foram ventilados sob mascara com oxigenio a 100% ate a obtencao de reducao de 75% ou mais na amplitude da resposta do musculo adutor do polegar, quando foram realizadas as manobras de laringoscopia e intubacao traqueal. A funcao neuromuscular foi monitorizada com aceleromiografia. Foram avaliados: tempo de inicio de acao do pancuronio e do rocuronio; tempo para instalacao do bloqueio total e condicoes de intubacao traqueal. RESULTADOS: Os tempos medios (segundos) para o inicio de acao e instalacao de bloqueio neuromuscular total produzido pelo pancuronio foram: Grupo I (159,33 ± 35,22 e 222 ± 46,56) e Grupo II (77,83 ± 9,52 e 105,96 ± 15,58); para o rocuronio: Grupo I (83 ± 17,25 e 125,33 ± 20,12) e Grupo II (48,96 ± 10,16 e 59,83 ± 10,36) com diferenca significativa entre os grupos. As condicoes de intubacao traqueal foram satisfatorias em 117 pacientes (97,5%) e insatisfatorias em 3 (2,5%). CONCLUSOES: O inicio de acao e o tempo para obtencao do bloqueio neuromuscular total no musculo adutor do polegar, produzidos pelo rocuronio e pelo pancuronio, sao mais curtos quando ha emprego de maiores frequencias de estimulos.BACKGROUND AND OBJECTIVES Factors associated to patients and neuromuscular blockers (NMB), as well as others inherent to neuromuscular function monitoring, may affect neuromuscular block onset. This study aimed at the influence of two different stimulation frequencies on rocuronium and pancuronium-induced neuromuscular block. METHODS Participated in this study 120 patients, physical status ASA I and II, submitted to elective procedures under general anesthesia, who were randomly allocated in two groups, according to the stimulation frequency employed to monitor neuromuscular block: Group I - 0.1 Hz (n = 60) and Group II - 1 Hz (n = 60). Two subgroups were formed within each group (n = 30), according to the neuromuscular blocker: Subgroup P (pancuronium) and Subgroup R (rocuronium). Patients were premedicated with muscular midazolam (0.1 mg kg(-1)), 30 minutes before surgery. Anesthesia was induced with propofol (2.5 mg kg(-1)) preceded by alfentanil (50 microg kg(-1)) and followed by pancuronium or rocuronium. Patients were ventilated under mask with 100% oxygen until 75% or more decrease in adductor pollicis muscle response, when laryngoscopy and tracheal intubation were performed. Neuromuscular function was monitored by acceleration transducer. The following parameters were evaluated: pancuronium and rocuronium onset time; time for complete block and tracheal intubation conditions. RESULTS Mean times (seconds) for pancuronium-induced neuromuscular block onset and for complete neuromuscular block were: Group I (159.33 +/- 35,22 and 222 +/- 46.56) and Group II (77.83 +/- 9.52 and 105.96 +/- 15.58); rocuronium-induced values were: Group I (83 +/- 17.25 and 125.33 +/- 20.12) and Group II (48.96 +/- 10.16 and 59.83 +/- 10.36) with statistical difference between groups. Tracheal intubation conditions were satisfactory in 117 patients (97.5%) and unsatisfactory in 3 (2.5%). CONCLUSIONS Rocuronium and pancuronium-induced neuromuscular block onset and time required for complete adductor pollicis muscle neuromuscular block are shorter when higher stimulation frequencies are applied.

Influence of Hypnotics on Cisatracurium-induced Neuromuscular Block. Use of Acceleromyograhpy

BACKGROUND AND OBJECTIVE Different drugs, including hypnotics, may influence the pharmacodynamic effects of neuromuscular blockers (NMB). The aim of this study was to evaluate the influence of propofol and etomidate on cisatracurium-induced neuromuscular blockade. METHOD We included 60 patients, ASA I and II, undergoing elective surgery under general anesthesia in the study and randomly allocated them into two groups, according to their hypnotic drug: GI (propofol) and GII (etomidate). Patients received intramuscular (IM) midazolam (0.1mg.kg(-1)) as premedication and we performed induction with propofol (2.5mg.kg(-1)) or etomidate (0.3mg.kg(1)), preceded by fentanyl (250mg) and followed by cisatracurium (0.1mg.kg(-1)). The patients were ventilated with 100% oxygen until obtaining a reduction of 95% or more in the adductor pollicis response amplitude, with subsequent laryngoscopy and tracheal intubation. Neuromuscular function was monitored by acceleromyograhpy. We evaluated the onset of action of cisatracurium, tracheal intubation conditions, and hemodynamic repercussions. RESULTS The mean time and standard deviations of cisatracurium onset were: GI (86.6±14.3s) and GII (116.9±11.6s), with a significant difference (p<0, 0001). Intubation conditions were acceptable in 100% of GI and 53.3% of GII patients (p<0.0001). CONCLUSION Induction of neuromuscular blockade with cisatracurium was faster, with better intubation conditions in patients receiving propofol compared to those receiving etomidate, without hemodynamic repercussions.

Comparación entre los efectos hemodinámicos de la intoxicación aguda con bupivacaína racémica y la mezcla con exceso enatiomérico de 50% (S75-R25): estudio experimental en perros

JUSTIFICATIVA Y OBJETIVOS: La bupivacaina racemica ha sido ampliamente utilizada en bloqueos locorregionales por la calidad y duracion de la anestesia proporcionada. Su toxicidad cardiovascular, sin embargo ya hace mucho tiempo preocupa a los anestesiologos y nuevas opciones han sido buscadas. Una de ellas es la utilizacion de su isomero levogiro que por una menor afinidad con los receptores de los canales de sodio de la celula cardiaca que seria menos cardiotoxico. En nuestro medio existe la presentacion que contiene un 75% del isomero levogiro y 25% del isomero dextrogiro, denominada mezcla con exceso enantiomerico de 50% (S75-R25). El objetivo de este estudio fue comparar en animales los efectos hemodinamicos de la intoxicacion aguda con bupivacaina racemica y con la mezcla S75-R25. METODO: Cuarenta y cuatro perros fueron anestesiados con pentobarbital, entubados y ventilados mecanicamente, siendo en seguida instalada la monitorizacion hemodinamica con cateter de Swan-Ganz y presion invasiva. Despues del periodo de reposo fueron divididos aleatoriamente en dos grupos de estudio encubierto, segun la intoxicacion con uno u otro agente en la dosis de 5 mg.kg-1. Los resultados hemodinamicos se recolectaron durante 30 minutos, tratados estadisticamente permitiendo la comparacion de la accion de los dos agentes. RESULTADOS: La mezcla S75-R25 causo mayores repercusiones hemodinamicas, particularmente, con importante disminucion de la presion arterial promedio, del indice cardiaco y del indice de trabajo del ventriculo izquierdo. CONCLUSIONES: Esos resultados se contraponen con los encontrados en humanos, cuando se utiliza el isomero levogiro puro, pero estan de acuerdo con estudios recientes en animales. Rebasar datos obtenidos en animales para seres humanos exige mucha cautela. Nuevos estudios se hacen necesarios en muestras mas abarcadoras y en grupos mas homogeneos.BACKGROUND AND OBJECTIVES Racemic bupivacaine has been widely used in locoregional anesthesia due to the quality and duration of its anesthetic action. However, its cardiovascular toxicity has worried anesthesiologists for a long time, and new options have been sought. One of them is the use of its levorotatory isomer that, due to a lesser affinity for the sodium channel receptors in the cardiac cell, would be less toxic. The presentation containing 75% of the levorotatory isomer and 25% of the dextrorotatory isomer, named 50% enantiomeric excess mixture (S75-R25), is available in our country. The objective of this study was to compare the hemodynamic effects of the acute intoxication with racemic bupivacaine and with the S75-R25 mixture in animals. METHODS Forty-four dogs were anesthetized with pentobarbital, intubated and placed on mechanical ventilation. Hemodynamic monitorization was accomplished with a Swan-Ganz catheter and intra-arterial blood pressure measurements. After a period of rest, they were randomly and blindly divided in two groups, according to the intoxication with either agent at a dose of 5 mg.Kg-1. Hemodynamic data were collected during 30 minutes and analyzed statically to allow for the comparison of both agents. RESULTS The mixture S75-R25 had more hemodynamic repercussions causing, especially, a significant reduction of the mean arterial pressure, cardiac index, and the left ventricle work index. CONCLUSIONS These results contradict those found in human beings regarding the pure levorotatory isomer, but confirm recent animal studies. One must be very careful when extrapolating animal data to human beings. Further studies involving larger samples and more homogeneous groups are necessary.

Comparison of the hemodynamic effects in acute intoxication with racemic bupivacaine and with 50% enantiomeric excess mixture (S75-R25): an experimental study in dogs

JUSTIFICATIVA Y OBJETIVOS: La bupivacaina racemica ha sido ampliamente utilizada en bloqueos locorregionales por la calidad y duracion de la anestesia proporcionada. Su toxicidad cardiovascular, sin embargo ya hace mucho tiempo preocupa a los anestesiologos y nuevas opciones han sido buscadas. Una de ellas es la utilizacion de su isomero levogiro que por una menor afinidad con los receptores de los canales de sodio de la celula cardiaca que seria menos cardiotoxico. En nuestro medio existe la presentacion que contiene un 75% del isomero levogiro y 25% del isomero dextrogiro, denominada mezcla con exceso enantiomerico de 50% (S75-R25). El objetivo de este estudio fue comparar en animales los efectos hemodinamicos de la intoxicacion aguda con bupivacaina racemica y con la mezcla S75-R25. METODO: Cuarenta y cuatro perros fueron anestesiados con pentobarbital, entubados y ventilados mecanicamente, siendo en seguida instalada la monitorizacion hemodinamica con cateter de Swan-Ganz y presion invasiva. Despues del periodo de reposo fueron divididos aleatoriamente en dos grupos de estudio encubierto, segun la intoxicacion con uno u otro agente en la dosis de 5 mg.kg-1. Los resultados hemodinamicos se recolectaron durante 30 minutos, tratados estadisticamente permitiendo la comparacion de la accion de los dos agentes. RESULTADOS: La mezcla S75-R25 causo mayores repercusiones hemodinamicas, particularmente, con importante disminucion de la presion arterial promedio, del indice cardiaco y del indice de trabajo del ventriculo izquierdo. CONCLUSIONES: Esos resultados se contraponen con los encontrados en humanos, cuando se utiliza el isomero levogiro puro, pero estan de acuerdo con estudios recientes en animales. Rebasar datos obtenidos en animales para seres humanos exige mucha cautela. Nuevos estudios se hacen necesarios en muestras mas abarcadoras y en grupos mas homogeneos.BACKGROUND AND OBJECTIVES Racemic bupivacaine has been widely used in locoregional anesthesia due to the quality and duration of its anesthetic action. However, its cardiovascular toxicity has worried anesthesiologists for a long time, and new options have been sought. One of them is the use of its levorotatory isomer that, due to a lesser affinity for the sodium channel receptors in the cardiac cell, would be less toxic. The presentation containing 75% of the levorotatory isomer and 25% of the dextrorotatory isomer, named 50% enantiomeric excess mixture (S75-R25), is available in our country. The objective of this study was to compare the hemodynamic effects of the acute intoxication with racemic bupivacaine and with the S75-R25 mixture in animals. METHODS Forty-four dogs were anesthetized with pentobarbital, intubated and placed on mechanical ventilation. Hemodynamic monitorization was accomplished with a Swan-Ganz catheter and intra-arterial blood pressure measurements. After a period of rest, they were randomly and blindly divided in two groups, according to the intoxication with either agent at a dose of 5 mg.Kg-1. Hemodynamic data were collected during 30 minutes and analyzed statically to allow for the comparison of both agents. RESULTS The mixture S75-R25 had more hemodynamic repercussions causing, especially, a significant reduction of the mean arterial pressure, cardiac index, and the left ventricle work index. CONCLUSIONS These results contradict those found in human beings regarding the pure levorotatory isomer, but confirm recent animal studies. One must be very careful when extrapolating animal data to human beings. Further studies involving larger samples and more homogeneous groups are necessary.

Efectos hemodinámicos de la oclusión de la aorta durante anestesia por inhalación con isoflurano y sevoflurano: estudio experimental en perros

BACKGROUND AND OBJECTIVES Aortic flow suppression and release during aortic procedures promote major hemodynamic disorders. This study aimed at evaluating these disorders in dogs anesthetized with isoflurane or sevoflurane. METHODS This study involved 41 dogs divided in two groups according to the anesthetic agent used for maintenance with 1 MAC: GI (n = 21) isoflurane; GS (n = 20) sevoflurane. Aorta was occluded by intra-arterial infra-diafragmatic cuff inflation for 30 minutes. Hemodynamic parameters were observed in moments M1 (control), M2 and M3, 15 and 30 minutes after aortic occlusion, M4 and M5, 15 and 30 minutes after cuff deflation. RESULTS During aortic occlusion there has been increased mean blood pressure (MBP), central venous pressure (CVP), pulmonary artery pressure (PAP), pulmonary capillary wedge pressure (PCWP) and systemic vascular resistance (SVR), without increase in pulmonary vascular resistance (PVR) and cardiac output (CO). CO was more stable with isoflurane as compared to sevoflurane where it has decreased after occlusion. Heart rate has initially decreased followed by increase during occlusion, being more expressive in GS as compared to GI, however without statistically significant difference between groups. Systolic volume was not importantly changed; left and right ventricular function have similarly increased after occlusion for both groups. With flow release, MBP, CVP, PAP, PCWP and SVR have decreased, and PVR has increased for both groups; ventricular function has abruptly decreased. CONCLUSIONS This study has shown that isoflurane is a better indication for such interventions for promoting less hemodynamic changes.JUSTIFICATIVA Y OBJETIVOS: La supresion del flujo aortico y su posterior liberacion en intervenciones quirurgicas de la aorta, ocasionan importantes disturbios hemodinamicos. El objetivo de este estudio fue el de evaluar esas alteraciones en perros anestesiados con isoflurano o sevoflurano. METODO: Se estudiaron 41 perros, divididos en dos grupos segun el anestesico empleado en el mantenimiento con 1 CAM: GI (n = 21) isoflurano; GS (n = 20) sevoflurano. Se realizo la oclusion aortica por insuflacion de globo intraarterial infradiafragmatico por 30 minutos. Los parametros hemodinamicos fueron observados en los momentos M1 (control), M2 y M3, 15 y 30 minutos despues de la oclusion aortica, M4 y M5, 15 y 30 minutos despues de la desinsuflacion del globo. RESULTADOS: Durante la oclusion de la aorta, se observo el aumento de la presion arterial promedio (PAM), de la presion venosa central (PVC), de la presion de arteria pulmonar (PAP), de la presion de capilar pulmonar (PCP) y de la resistencia vascular sistemica (RVS) sin aumento de la resistencia vascular pulmonar (RVP) y del debito cardiaco (DC). El DC se mantuvo mas estable con el isoflurano comparado al sevoflurano, con el cual presento disminucion despues de la oclusion. La frecuencia cardiaca tuvo disminucion inicial que despues aumento durante la oclusion, siendo en GS mas expresiva que en GI, sin embargo, sin diferencia significativa entre los grupos. El volumen sistolico no tuvo grandes alteraciones; el trabajo sistolico de los ventriculos izquierdo y derecho aumento despues de la oclusion de forma similar en los dos grupos. Con la liberacion del flujo PAM, PVC, PAP, PCP y RVS bajaron, la RVP aumento en los dos grupos; el trabajo ventricular disminuye abruptamente. CONCLUSIONES: El estudio demostro que el isoflurano es el mas indicado en esas intervenciones quirurgicas por causar menores alteraciones hemodinamicas.

[Hemodynamic effects of aortic occlusion during inhalational anesthesia with isoflurane and sevoflurane: experimental study in dogs].

BACKGROUND AND OBJECTIVES Aortic flow suppression and release during aortic procedures promote major hemodynamic disorders. This study aimed at evaluating these disorders in dogs anesthetized with isoflurane or sevoflurane. METHODS This study involved 41 dogs divided in two groups according to the anesthetic agent used for maintenance with 1 MAC: GI (n = 21) isoflurane; GS (n = 20) sevoflurane. Aorta was occluded by intra-arterial infra-diafragmatic cuff inflation for 30 minutes. Hemodynamic parameters were observed in moments M1 (control), M2 and M3, 15 and 30 minutes after aortic occlusion, M4 and M5, 15 and 30 minutes after cuff deflation. RESULTS During aortic occlusion there has been increased mean blood pressure (MBP), central venous pressure (CVP), pulmonary artery pressure (PAP), pulmonary capillary wedge pressure (PCWP) and systemic vascular resistance (SVR), without increase in pulmonary vascular resistance (PVR) and cardiac output (CO). CO was more stable with isoflurane as compared to sevoflurane where it has decreased after occlusion. Heart rate has initially decreased followed by increase during occlusion, being more expressive in GS as compared to GI, however without statistically significant difference between groups. Systolic volume was not importantly changed; left and right ventricular function have similarly increased after occlusion for both groups. With flow release, MBP, CVP, PAP, PCWP and SVR have decreased, and PVR has increased for both groups; ventricular function has abruptly decreased. CONCLUSIONS This study has shown that isoflurane is a better indication for such interventions for promoting less hemodynamic changes.JUSTIFICATIVA Y OBJETIVOS: La supresion del flujo aortico y su posterior liberacion en intervenciones quirurgicas de la aorta, ocasionan importantes disturbios hemodinamicos. El objetivo de este estudio fue el de evaluar esas alteraciones en perros anestesiados con isoflurano o sevoflurano. METODO: Se estudiaron 41 perros, divididos en dos grupos segun el anestesico empleado en el mantenimiento con 1 CAM: GI (n = 21) isoflurano; GS (n = 20) sevoflurano. Se realizo la oclusion aortica por insuflacion de globo intraarterial infradiafragmatico por 30 minutos. Los parametros hemodinamicos fueron observados en los momentos M1 (control), M2 y M3, 15 y 30 minutos despues de la oclusion aortica, M4 y M5, 15 y 30 minutos despues de la desinsuflacion del globo. RESULTADOS: Durante la oclusion de la aorta, se observo el aumento de la presion arterial promedio (PAM), de la presion venosa central (PVC), de la presion de arteria pulmonar (PAP), de la presion de capilar pulmonar (PCP) y de la resistencia vascular sistemica (RVS) sin aumento de la resistencia vascular pulmonar (RVP) y del debito cardiaco (DC). El DC se mantuvo mas estable con el isoflurano comparado al sevoflurano, con el cual presento disminucion despues de la oclusion. La frecuencia cardiaca tuvo disminucion inicial que despues aumento durante la oclusion, siendo en GS mas expresiva que en GI, sin embargo, sin diferencia significativa entre los grupos. El volumen sistolico no tuvo grandes alteraciones; el trabajo sistolico de los ventriculos izquierdo y derecho aumento despues de la oclusion de forma similar en los dos grupos. Con la liberacion del flujo PAM, PVC, PAP, PCP y RVS bajaron, la RVP aumento en los dos grupos; el trabajo ventricular disminuye abruptamente. CONCLUSIONES: El estudio demostro que el isoflurano es el mas indicado en esas intervenciones quirurgicas por causar menores alteraciones hemodinamicas.