RESUMEN
The change in ionized magnesium (Mg) was investigated during isoflurane-nitrous oxide-oxygen anesthesia. The patients were divided into two groups by induction method of anesthesia. Group 1 was induced with thiamylal 4 mg.kg-1 and Group 2 was induced with ketamine 1 mg.kg-1. The ionized Mg concentration was recorded by NOVA 8 analyzer and observed during anesthesia. We also recorded the serum concentration of total Mg after administration of thiamylal. During induction of anesthesia and surgery, ionized Mg concentration decreased significantly in both groups. The ionized Mg concentration after administration of thiamylal was significantly lower than that after administration of ketamine. The serum total Mg concentration did not decrease throughout the anesthesia course. The ionized calcium concentration decreased, but the concentration of Na and K remained essentially unchanged. We conclude, therefore, that ionized Mg concentration decreases during surgery under general anesthesia, in part, possibly by the effect of anesthetic agent on the cell membrane itself.
Asunto(s)
Anestesia General , Complicaciones Intraoperatorias/etiología , Magnesio/sangre , Adulto , Anestésicos Disociativos/efectos adversos , Anestésicos Intravenosos , Femenino , Humanos , Ketamina/efectos adversos , Masculino , Persona de Mediana Edad , Tiamilal/efectos adversosRESUMEN
We synthesized poly (DL-lactic acid)-fentanyl composites and compared the duration of analgesia after the administration of a single intrathecal dose of these agents in rats. The drug was injected with an intrathecal catheter into the intrathecal space. Fentanyl composites or plain fentanyl in doses of 2.5 or 25 micrograms were administered, respectively. Animals were then tested for analgesia using the tail-flick test. The release rate of fentanyl from fentanyl composites in vitro was also evaluated. The antinociceptive effect of fentanyl composites (25 micrograms) was significantly longer than that of plain fentanyl. Administration of poly (DL-lactic acid) alone did not induce the antinociceptive effect. Four of 7 animals given plain fentanyl (25 micrograms) exhibited temporary respiratory depression, but none of the animals given fentanyl composites showed this response. In vitro experiments demonstrated a slow release of fentanyl from the fentanyl composites. We conclude that the antinociceptive effect of fentanyl can be prolonged when administered as a poly (DL-lactic acid)-fentanyl composite in the intrathecal space with decreased systemic side effects compared with the plain formulation.
Asunto(s)
Analgésicos Opioides/administración & dosificación , Fentanilo/administración & dosificación , Dolor/tratamiento farmacológico , Analgésicos Opioides/efectos adversos , Animales , Preparaciones de Acción Retardada , Portadores de Fármacos , Fentanilo/efectos adversos , Inyecciones Espinales , Ácido Láctico , Masculino , Poliésteres , Polímeros , Ratas , Ratas Sprague-Dawley , Trastornos Respiratorios/inducido químicamenteRESUMEN
Epidurally administered morphine is useful in the management of postoperative or cancer pain, and a reliable method which can produce prolongation of analgesia with a single dose may be very useful. We synthesized a polyethylene glycol-morphine (PEG-morphine) composites and examined the duration of analgesia after a single epidural administration dose of this agent in the rat. The molecular weight of PEG was functionally evaluated. PEG-morphine was injected surgically along the epidural space. Morphine in doses of 2.5, 5.0 and 7.5 mg and PEG only were administered. A second group of animals received intramuscular injections of PEG-morphine (5.0mg). Animals were then tested for analgesia using the tail-flick test. The antinociceptive effect of 7.5mg was significantly longer than that of 2.5mg or 5.0mg. Neither PEG alone nor intramuscular administration of PEG-morphine induced antinociceptive effect. Sensory blockade was reversible and the animal appeared to have normal sensory perception. We conclude that the antinociceptive effect of morphine is dose-dependent and its duration can be prolonged when administered as a PEG-morphine composite in the epidural space.