The Role of Thiopental and Fentanyl in the Production of Balanced Anaesthesia

Publisher Website
Google Scholar
Abstract
In order to clarify the interactions between various doses of thiopental [TP] and fentanyl [FN] in producing balanced anesthesia, their effects on consciousness, superficial nociception and respiration and circulation were studied during N2O + O2 inhalation in connection with the induction of anesthesia. Sixty patients were studied; the drug combinations used were TP 5 mg/kg, TP 3 mg/kg, TP 3 mg/kg and FN 0.5 .mu.g/kg (TP3F0.5). TP 2 mg/kg and FN 1 .mu.g/kg (TP2F1), TP 1 mg/kg and FN 2 .mu.g/kg and FN 3 .mu.g/kg (F3). Five minutes after i.v. supplementation of N2O + O2 anesthesia, the depth of anesthesia and analgesia (antinociception) were evaluated from the eyelid reflex and by pinching an inguinal skin-fold. Cardiorespiratory parameters were measured during this study period at 1 min intervals. The balance between antinociception anesthesia was closest to optimum in groups TP2F1 and TP3F0.5. In pure TP groups, the analgesia was poor; only 4 patients did not respond to the nociceptive stimulus, whereas in group F3 anesthesia (disappearance of the eyelid reflex) was obtained in only 2 patients. The respiratory depression was most pronounced in groups receiving 3, 2 and 1 .mu.g/kg FN and weakest in groups where only TP was used. Blood pressure decreased in all groups but no statistically significant differences were noted. Attempts to achieve balanced anesthesia by the supplementation of an N2O + O2 mixture with FN only apparently leads to an unnecessarily pronounced respiratory depression, whereas supplementation with TP alone does not offer adequate antinociception.