Clinical and Histological Effects of the Intrathecal Administration of a Single Dose of Dexmedetomidine in Rabbits.

BACKGROUND: There is experimental evidence that dexmedetomidine has neuroprotective effects. So, it could be expected that its intrathecal or epidural administration presents no harm. However, whether dexmedetomidine is neurotoxic to the spinal cord remains to be fully elucidated. OBJECTIVE: To evaluate the effect of preservative-free dexmedetomidine administered as a subarachnoid single injection on the spinal cord and meninges of rabbits. STUDY DESIGN: Research article. SETTING: Experimental research laboratory. METHODS: Twenty young adult female rabbits, each weighing between 3200 and 4900 g, and having a spine length between 36 and 40 cm, were divided by lot into 2 groups (G): 0.9% saline in G1 and preservative-free dexmedetomidine in G2 (dose of 10 µg). After intravenous anesthesia with ketamine and xylazine, the subarachnoid space was punctured at S1-S2 under ultrasound guidance, and a random 5 µl.cm-1 of spinal length (0.2 mL) of solution (saline or dexmedetomidine) was injected. The animals remained in captivity for 21 days under medical observation and were sacrificed by decapitation. The lumbosacral spinal cord portion was removed for immunohistochemistry to assess the glial fibrillary acidic protein (GFAP), and histology was assessed using hematoxylin and eosin (HE) stain. RESULTS: None of the animals had impaired motor function or decreased nociception during the period of clinical observation. None of the animals from the control group showed signs of injuries to meninges. In the dexmedetomidine group, however, 9 animals presented with signs of meningeal injury. The main histological changes observed were areas with meningeal thickening and lymphoplasmocitary infiltration in the pia-mater and arachnoid. Further histological examination also revealed adherence areas among the pia and arachnoid. There was no signal of injury in neural tissue in any animal of both groups. LIMITATIONS: Evaluation of the possible analgesic effects of the intrathecal dexmedetomidine was not performed. CONCLUSION: On the basis of the present results, dexmedetomidine administered in the subarachnoid space in a single dose of 10 µg is capable of producing histological changes over the meninges of rabbits.

Clinical and histological effects of the intrathecal administration of methylprednisolone in dogs.

BACKGROUND: Methylprednisolone is one of the most commonly used steroids for management of chronic back pain via epidural injection. Its inadvertent injection into the intrathecal space is associated with complications such as adhesive arachnoiditis. OBJECTIVE: The present study aimed to assess the clinical and histological changes associated with the injection of methylprednisolone into the intrathecal space of dogs. STUDY DESIGN: A randomized, double blind, controlled animal trial. METHODS: After approval by the animal research ethics committee, 14 dogs were studied in a randomized double blind controlled trial. They were assigned to one of 2 groups: Group I received 1 mL of 0.9% normal saline; Group II received 1 mL (1.15mg/kg) of methylprednisolone into the intrathecal space. Animals were clinically evaluated for 21 days, and then sacrificed. The lumbar and sacral portions of their spinal cords were removed for histological examination. RESULTS: In Group I, there were no clinical or histological changes. All animals in Group II showed no clinical changes but all exhibited histological changes in the spinal cord. The main histological changes consisted of meningeal thickening and lymphocytic infiltrates in the blood vessels. In 3 animals, adhesion of pia, arachnoid, and dura matter was noted and the nerve roots were surrounded by fibrosis. In one animal, necrosis of the spinal cord was evident. LIMITATIONS: The limitations of the present study include: small sample of animals (n=14), relative short clinical follow-up (21 days), and use of a commercially available drug solution, which is not preservative free. CONCLUSION: The present study demonstrated that the intrathecal administration of commercially available methylprednisolone was responsible for causing histological changes in the spinal cord and meninges of the animals studied.

The neuraxial effects of intraspinal amitriptyline at low concentrations.

BACKGROUND: As a result of amitriptyline's vast array of actions, it could potentially be used as an intraspinal adjuvant in neuraxial anesthesia and/or in the treatment of refractory neuropathic pain. None of the previous studies examining the safety profile of intraspinal single doses of amitriptyline found signs of toxicity at concentrations below 15.4 mM/L (0.5%) and the current hypothesis regarding the pathophysiology of amitriptyline toxicity suggests it might be safe at low concentrations while still having relevant clinical effects. Hence, we conducted this study to assess the clinical and histological toxicity of intraspinal amitriptyline at the lowest dosages previously known to be effective. METHODS: Twenty-one dogs were randomized to receive a 1-mL single intraspinal dose of one of the three solutions: saline (0.9%), amitriptyline (0.15%), or amitriptyline (0.3%). The dogs were evaluated clinically 1 h after awakening from anesthesia and 21 days later. At 21 days, all animals were killed, and histological sections of the spinal cord and surrounding meninges were retrieved for analysis. RESULTS: All dogs recovered motor function, anal sphincter tone and sensibility. With the exception of one dog in the 0.15% amitriptyline group, all animals in both amitriptyline groups had marked adhesive arachnoiditis, which was absent in the control group. No evidence of direct neural damage was found on histological sections stained by glial fibrillary acidic protein technique in any of the study animals. CONCLUSION: The intraspinal administration of amitriptyline to dogs even in low concentrations is strongly associated with the development of intense meningeal adhesive arachnoiditis and is not safe even at low concentrations for which there was no previous evidence of toxicity.

Eficácia do ondansetron e da alizaprida na prevençäo de náusea e vômito em laparoscopia ginecológica / Efficacy of ondansetron and alizapride in preventing gynecological laparoscopy nausea and vomiting

Justificativa e Objetivos: A laparoscopia ginecológica é procedimento que determina alta incidência de náusea e vômito em pacientes submetidas à laparoscopia ginecológica. Método: Participaram do estudo 52 pacientes, estado físico ASA I ou II, com idades entre 21 e 50 anos, sem queixas gástricas prévias, submetidas à laparoscopia para diagnóstico ou cirurgia. As pacientes foram divididas em 2 grupos: o grupo 1 recebeu ondansetron (4mg) e o grupo 2, alizaprida (50 mg), por via venosa, antes da induçäo da anestesia. Todas as pacientes receberam midazolan (7,5 mg) por via oral como medicaçäo pré-anestésica, sufentanil (0,5 µg.kg-û) e propofol (2 mg.kg-û) para induçäo, propofol (115 µg.kg-û) e N2O/O2 em fraçäo inspirada de O2 a 40 por cento para manutençäo e atracúrio (0,5 mg.kg-û) como bloqueador neuromuscular. A analgesia pós-operatória foi realizada com cetoprofeno (100 mg) e buscopam composto. Resultados: Ambos os grupos foram idênticos quanto aos dados antropemétricos e a duraçäo da cirurgia e da anestesia. No grupo 2, uma paciente apresentou náusea e três vomitaram, resultados estatisticamente näo significativos. Concluöes: O ondansetron e a alizaprida foram similares na prevençäo de náusea e vômito em pacientes submetidas à laparoscopia ginecológica

Peridural com ropivacaína a 1 por cento: experiência com volume proporcional à estatura / Epidural anesthesia with 1 percent ropivacaine: experience with volume proportional to height

Justificativa e objetivos - A ropivacaína, anestésico local amino amida, é um enanitômero S puro, o que confere à droga alta potência e baixa toxicidade. A proposta de nosso estudo foi avaliar o comportamento do bloqueio peridural com ropivacaína a 1 por cento em volumes menores que aqueles descritos na literatura. Método - foram selecionados 38 pacientes, estado físico ASA I e II, com idades entre 15 e 70 anos e peso de 50 a 100 kg. A medicaçäo pré-anestésica foi midazolam, (15 mg) por via oral, 60 minutos antes da anestesia. Na sala cirúrgica, após a monitorizaçäo, os pacientes recebiam infusäo venosa de 10 ml.kg elevado a menos 1 de soluçäo de Ringer com lactato. Realizava-se a punçäo peridural com o paciente na posiçäo sentada e administrava-se ropivacaína a 1 por cento em volume correspondente a 10 por cento de sua altura em centímetros. Eram entäo colocados em decúbito dorsal horizontal e avaliadas a intensidade do bloqueio motor e a extensäo dos bloqueios sensitivos e térmico, 1, 3, 5, 7, 10, 15, 20 e 30 minutos após a injeçäo da droga. Também foram observados a pressäo arterial, a frequência cardíaca e os efeitos colaterais decorrentes da técnica no per e pós-anestésico imediato e na visita pós-anestésica. Na sala de recuperaçäo pós- anestésica os pacientes foram acompanhados até a reversäo total do bloqueio motor e regressäo do bloqueio sensitivo e térmico até o nível L2. Resultados - A idade média foi de 41,4 anos, o peso 68,8 kg e a altura 165 cm. O nível superior de bloqueio térmico foi T4 e sensitivo, T6. A maioria dos pacientes apresentou bloqueio motor grau 1 (Bromage) ao final dos 30 minutos de observaçäo. A duraçäo média do bloqueio motor foi de 254 min e do térmico e sensitivo 426 min. Apenas três pacientes apresentaram complicaçöes, sendo dois casos de hipotensäo arterial e um de bradicardia. Conclusöes - Nos volumes utilizados neste estudo, a ropivacaína promoveu adequado nível de analgesia, bloqueio motor de membros inferiores pouco intenso, porém suficiente para realizaçäo dos procedimentos cirúrgicos propostos e baixa incidência de efeitos colaterais

Efeitos do sulfato de magnésio na hemodinâmica cardiovascular de cåes anestesiados com pentobarbital sódico / Effects of magnesium sulphate on the cardiovascular hemodynamics of dogs anesthetized pentobarbitone

Background and Objectives - A controversy exists in the literature regarding the effects of the acute administration of magnesium on the cardiovascular system of animals and humans. The purpose of this study was to evaluate the effects of hypermagnesemia on the cardiovascular hemodynamics of dogs. Methods - Sixteen mongrel dogs were anesthtized with pentobarbitone 30mg.kg-1 and submitted to volume expansion with Ringer's solution (0.4ml.kg-1.min-1) and mechanical ventilation with room air. In this model, the hemodynamic repercussions of the following drugs and doses were studied: pentobarbitone 5mg,kg-1 - Group 1, control - and the association of pentobarbitone and magnesium sulphate (MS), at the dose of 140 mg.kg-1, injected in 15 minutes, followed by an infusion of 80 mg.kg-1.h-1 - Group 2. The parameters studied were: heart rate, blood pressure, inferior vena cava pressure, cardiac index, systolic index and peripheral resistance index, evaluated at 5 different moments: 15(M1), 30(M2), 60(M3) and 75(M4) minutes after the first supplementary dose of pentobarbitone and 15 minutes (M5) after the second supplementary dose. In group 2, the moments M3, M4, M5 corresponded to 15, 30 and 60 minutes after the priming dose of magnesium sulphate. Results - Group 1 animals exhibited tachycardia since the beginning of the experiment. There was a decrease in the cardiac index, in the systolic index and an increase in the inferior vena cava pressure. group 2 animals also exhibited tachycardia, but heart rate decreased after MS infusion. The blood pressure and the peripheralresitance index decreased. The systolic index increased and the cardiac index decresead only at he end of the experiment. Conclusions - The antiadrenergic effects of Ms could have been responsible for the decrease in heart rate. The vasodilating effects of the magnesium induced the decrease in the peripheral resistance index. The vasodilating effects of the magnesium induced the decrease in the peripheral resistance index. The systolic index increased, showing that myocardial depression did not occur.

Sufentanil intranasal como medicaçäo pré-anestésica em crianças / Intranasal sufentanil as preanesthetic medication in children

Justificativas e objetivos - Dentre as diferentes vias utilizadas para administracao da medicacao pre-anestesica (MPA), a via intranasal oferece a vantagem da rapida absorcao sistemica, alem de evitar as dolorosas injecoes intramuscular e nevosa. O presente estudo tem como objetivo avaliar a eficacia do sufentanil como MPA na reducao da ansiedade dos pacientes pediatricos, assim como no comportamento dos memos durante a inducao anestesica. Metodo - Participaram do estudo trinta pacientes com idade de 1 a 9 anos, ASA 1, submetidos a cirurgias eletivas, que receberam sufentanil (2 mug.kg(-1) por via intransal como MPA. Utilizando-se o grau de ansiedade em 3 momentos: T0 - chegada da crianca com os pais; T5 e T10, respectivamente, cinco e dez minutos apos a administracao da droga. Avaliou-se tambem o comportamento durante a inducao. Todas as inducoes anestesicas foram venosas, utilizando-se tiopental ou cetamina. Resultados - O grau de ansiedade nao diminuiu dez minutos apos a administracao do sufentanil e nao se observou melhora na qualidade da inducao anestesica. Conclusoes - O sufentanil intranasal, nas doses empregadas neste estudo, nao mostrou ser eficiente na reducao da ansiedade nem melhorou a qualidade da inducao anestesica, quando o tempo entre a administracao da droga e a separacao dos pais foi de apenas dez minutos.