[Modern pharmacological principles for intravenous anaesthesia]. / Moderne farmakologiske prinsipper for intravenøs anestesi.

BACKGROUND: Anaesthetic pharmacology is characterized by use of drugs in high doses for a short period of time. Knowledge of pharmacokinetics is important for precise control of drug effects (onset, maintenance and offset). MATERIAL AND METHODS: The paper is based on own research, experience from clinical practice, teaching, and up-to-date knowledge of the available literature. RESULTS: Traditional pharmacokinetic terms; such as volume of distribution, clearance and elimination half-life are useful within anaesthesiology, but two other important concepts should be considered: time to effect onset (keO) and context sensitive elimination half-life. keO is dependent upon distribution of drug from plasma to site of effect and the speed of cellular effect activation. The context sensitive elimination half-life upon discontinuation of a drug depends on how long the drug has been administered, and is shorter than terminal elimination half-life for anaesthetic drugs when used shorter than 12 - 24 hrs. With short-term use of drugs there is a profound initial drug distribution into tissues in addition to elimination. With prolonged use there is more drug deposited in the tissues, lower diffusion gradient and prolonged context sensitive elimination half-time. Computerized infusion pumps (Target Control Infusion, TCI) enable dosing of opioids or propofol to a preset concentration, either in plasma or at the site of effect. INTERPRETATION: Knowledge of pharmacologic principles and modeling from studies on volunteers and patients form the basis for good clinical monitoring of anaesthetic drug effects.

[Assessing the depth-of-hypnosis]. / Måling av narkosedybde.

BACKGROUND: There has been a breakthrough in the understanding of anaesthetic drug effects during the last two decades, and new monitors aimed at quantifying such effects have been developed. MATERIAL AND METHODS: This review is based on publications from the last 15 years, oral presentations, and rewritten parts of the author's PhD thesis. RESULTS: General anaesthesia can be regarded as a combination of hypnosis (sleep), analgesia and muscle relaxation. Modern anaesthetic drugs aim at each of these effects separately. Pharmacological variation makes it impossible to find one dose suitable for all, so tools for measuring drug effects in the individual patient are warranted. Monitors for measuring depth-of-hypnosis and partly analgesic effect are commercially available. Among these, BIS (bispectral index), based on EEG, is by far the best documented. BIS is proven useful for preventing undesired awareness and overdosing, but there are major limitations. Use of such technology in clinical practice is under constant debate. INTERPRETATION: Even though the BIS technology is promising and used widely, no health authorities have so far recommended that such monitors should be compulsory during general anaesthesia, but rather that it should be considered on an individual basis. So far, it seems like this is a sensible approach in Norway as well.

[Do women with Caesarean section have to choose between pain relief and breastfeeding?]. / Må keisersnittspasienter velge mellom smertebehandling og amming?

BACKGROUND: The Caesarean section is a unique surgical procedure in that physicians postoperatively not only have to cater to the mothers' need for analgesics, but must also take into account the impact of this medication on the infant. Too cautious prescription of strong analgesics postoperatively may have untoward consequences, such as immobilisation and delayed onset of breastfeeding. MATERIAL AND METHOD: A questionnaire on procedures for standard postoperative analgesics after Caesarean section was sent to the 46 Norwegian hospitals with anaesthesiology departments organized in conjunction with delivery units. 38 questionnaires were returned to us. RESULTS: Most of these hospitals routinely prescribe both Paracetamol (95%) and NSAID (90%) in postoperative care immediately after Caesarean section. However, only 61% routinely prescribed an opioid. INTERPRETATION: When the mother is most in need of opioid analgesics, lactation is barely established. Therefore, even if traces of opioids are absorbed into the mother's milk, the doses will be very small and the infant's oral bioavailability at this time is likely to be low. Consequently, there is little evidence to support a policy of overly restrictive use of opioids.

Spectral entropy monitoring is associated with reduced propofol use and faster emergence in propofol-nitrous oxide-alfentanil anesthesia.

BACKGROUND: This multicenter study evaluated the effect of a new depth of anesthesia-monitoring device based on time-frequency-balanced spectral entropy of electroencephalogram monitoring (GE Healthcare Finland, Helsinki, Finland) on consumption of anesthetic drugs and recovery times after anesthesia. METHODS: The study was a prospective, randomized, single-blind study performed in six hospitals in Finland, Sweden, and Norway. After institutional review board approval and written informed consent from each patient, the patients were randomly allocated to anesthesia with entropy values either shown (entropy group) or not shown (control group). Anesthesia was maintained with propofol, nitrous oxide, and alfentanil. In the entropy group, propofol was given to keep the state entropy value between 45 and 65, and alfentanil was given to keep the state entropy-response entropy difference below 10 units and heart rate and blood pressure within +/-20% of the baseline values. The control group patients were anesthetized to keep heart rate and blood pressure within +/-20% of the baseline values. Statistical methods included Mann-Whitney U test and unpaired t tests. RESULTS: A total of 368 patients were studied. In the entropy group, entropy values were higher during the whole operation and especially during the last 15 min (P < 0.001). Consequently, propofol consumption was smaller in the entropy group during the whole anesthesia period (P < 0.001) and especially during the last 15 min (P < 0.001). This shortened the time delay in the early recovery parameters in the entropy group. CONCLUSION: Entropy monitoring assisted titration of propofol, especially during the last part of the procedures, as indicated by higher entropy values, decreased consumption of propofol, and shorter recovery times in the entropy group.