[Alfentanil as the last dose (on top) in neuroleptanesthesia with fentanyl. Pharmacokinetics and pharmacodynamics with reference to the cortical effect].

Due to its predictable duration of action, its low volume of distribution in the organism (muscle, fat tissue, skin) and a corresponding low terminal elimination half life (t 1/2 beta), alfentanil seems suitable for use as the last dose of opioid given during NLA. In order to compare the efficacy of this regimen, patients (n = 10) during routine-NLA (induction 0.3 mg/kg etomidate, 140 micrograms/kg droperidol, 5 micrograms/kg fentanyl with a maintenance dose of 2 micrograms/kg when necessary and mechanical N2 O/O2 = 2:1 ventilation) received alfentanil (20 micrograms/kg) as the last opioid, while another set of patients (n = 5) received fentanyl (1.5 micrograms/kg). For recording of vigilance continuous EEG power spectra were derived (position Fpz--C3), and in addition minute volume was monitored postoperatively. After the last dose of the opioid, alfentanil--and fentanyl--blood plasma levels were determined every 10 min over a period of 100 min Vigilance, i.e. the sensitivity of the organism in responding to a stimulus, was significantly higher in the "on-top"-alfentanil group. This was derived from the high power in fast frequency domains, beta (greater than 460%) and alpha (greater than 34%) compared to routine NLA in the post op. period. No significance was observed among both groups in regard to postop. respiratory minute volumes and fentanyl plasma levels. There was no correlation between power in the various frequency bands (delta, theta, alpha and beta), postoperative respiratory minute volumes and corresponding plasma levels of fentanyl. Due to a higher state of postoperative vigilance, alfentanil is considered a suitable alternative as the last opioid during narcotic anaesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)