Skin conductance responses in patients sedated with midazolam or propofol

Propofol infusion for sedation during spinal anesthesia

PURPOSE

The dose and time course of propofol infusion required to induce rapid sedation without oversedation during spinal anesthesia were investigated.

METHODS

Forty patients scheduled for spinal and epidural anesthesia were studied. After premedication with intramuscular midazolam 0.04 mg.kg(-1), an epidural catheter was inserted, followed by spinal anersthesia at L4-L5 with 0.5% hyperbaric tetracaine with epinephrine. The infusion of propofol was started with 10 mg.kg(-1).h(-1) and was decreased to 5 mg.kg(-1).h(-1) at spontaneous eye closure. According to the increase or decrease of the sedation level, the infusion does was decreased or increased to half or twice the initial dose, respectively, to keep the Observer's Assessment of Alertness Sedation (OAAS) score at 3 or 4.

RESULTS

Eye closure was observed at 1.0 +/- 0.4 min after the start of insusion. The maintenance insusion dose to keep the OAAS score at 3 or 4 was about 2.5 mg.kg(-1).h(-1).

CONCLUSION

Propofol infusion, starting with 10 mg.kg(-1).h(-1), decreasing to 5 mg.kg(-1).h(-1) after 1 minute, and then decreasing to 2.5 mg.kg(-1).h(-1) after another min induced rapid onset of sedation and kept the OAAS score at 3 or 4 during spinal anesthesia.

Drugs, sweat, and fears: a comparison of the effects of diazepam and methylphenidate on fear conditioning

RATIONALE

Classical conditioning of a fear response involves the formation of an association between a stimulus and an emotional response and can be seen as a basic form of emotional memory. While both benzodiazepines and stimulant drugs may influence the formation of episodic memories for emotional events, their effects on fear conditioning are less clear.

OBJECTIVES

This study compared the effects of diazepam with methylphenidate on fear conditioning.

MATERIALS AND METHODS

In a single-session between groups design with three conditions [placebo, diazepam (10 mg), and methylphenidate (40 mg)], classical conditioning of a skin conductance response to a visual stimulus previously paired with a 100-db white noise was tested in 45 healthy volunteers.

RESULTS

Diazepam blocked fear conditioning, despite responses to the unconditioned aversive stimulus and neutral control stimulus being unimpaired. Conditioning remained intact after methylphenidate. Conditioned responses were not extinguished completely by the end of the experiment, and it was not possible to draw conclusions about the effects of the drugs on extinction.

CONCLUSIONS

Although diazepam has well-documented amnesic effects, it has not been found to affect implicit forms of memory like perceptual and conceptual priming. As the present study found impaired fear conditioning after diazepam, it adds weight to recent findings that emotional memories are disproportionately impaired by the benzodiazepines.

Noninvasive indices of autonomic regulation after alprazolam and lorazepam: effects on sympathovagal balance

Skin conductance level (SCL) and spectral analysis of variations in heart rate (HR) and blood pressure (BP), in relation to plasma catecholamine concentrations, were used to evaluate autonomic nervous system activity during situations of supine rest within a period of 4 h after oral administration of 1 mg alprazolam and 2 mg lorazepam. Twelve healthy men received in a double-blind, randomized crossover design, either 1 mg alprazolam, or 2 mg lorazepam, or a placebo on different days. ECG, BP, respiration, and SCL were monitored continuously during each session. For HR, systolic and diastolic BP (SBP, DBP) time series, power spectra were calculated per 5 min for three 15-min periods at 30 min, 1 h and 45 min, and 3 h after dosing. Spectral power was assessed for three frequency bands: low (0.02-0.06 Hz), mid (0.07-0.14 Hz), and high (0.15-0.50 Hz). Per time segment, the gain in the mid-frequency band between the systolic BP values and the RR interval times was computed as index of baroreflex sensitivity (BRS). Blood samples for assay of plasma catecholamines were obtained after each 15-min period. Alprazolam reduced DBP during the whole recording period; the effect was accompanied by an initial increase of mid-frequency band fluctuations of BP at 30 min, which subsequently decreased at 1 h 45 min and 3 h after dose administration, in comparison with placebo (suggesting an initial reflectory increase, followed by an attenuation of sympathetic tone). The BP effects were accompanied by a reduction of plasma noradrenaline concentrations. HR showed a time-dependent decrease after alprazolam and an increase in high-frequency band fluctuations of HR and BRS (suggesting a time-dependent increase in cardiac vagal tone). SCL was decreased after alprazolam administration. Lorazepam did not show a time-dependent reduction of HR and had no effect on BP, but increased low-frequency band power of HR and DBP and mildly reduced SCL. Alprazolam and lorazepam had no effect on respiratory frequency. Noninvasive indices of autonomic regulation revealed several small, but significant, time-dependent effects of 1 mg alprazolam on sympathetic and parasympathetic processes, whereas for 2 mg lorazepam, these effects were less clear. The reduction in noninvasive indices of sympathetic tone after alprazolam administration corresponded with the attenuation of plasma noradrenaline concentrations by alprazolam.

Propofol or midazolam for sedation and early extubation following cardiac surgery

PURPOSE

The purpose of this randomized, double-blind study was to evaluate the efficacy of midazolam and propofol for postoperative sedation and early extubation following cardiac surgery.

METHODS

ASA physical status II-III patients scheduled to undergo elective first-time cardiac surgery with an ejection fraction > 45% were eligible. All patients received a standardized sufentanil/isoflurane anaesthesia. During cardiopulmonary bypass 100 micrograms.kg-1.min-1 propofol was substituted for isoflurane. Upon arrival in the Intensive Care Unit (ICU), patients were randomized to either 10 micrograms.kg-1.min-1 propofol (n = 21) or 0.25 microgram.kg-1.min-1 midazolam (n = 20). Infusion rates were adjusted to maintain sedation within a predetermined range (Ramsay 2-4). The infusion was terminated after four hours. Patients were weaned from mechanical ventilation and their tracheas extubated when Haemodynamic stability, haemostasis, normothermia and mental orientation were confirmed. Haemodynamic measurements, arterial blood gas tensions and pulmonary function tests were recorded at specified times.

RESULTS

There were no differences between the two groups for the time spent at each level of sedation, number of infusion rate adjustments, amount of analgesic and vasoactive drugs, times to awakening and extubation. The costs of propofol were higher than those of midazolam. There were no differences in haemodynamic values, arterial blood gas tensions and pulmonary function.

CONCLUSION

We conclude that midazolam and propofol are safe and effective sedative agents permitting early extubation in this selected cardiac patient population but propofol costs were higher.

Propofol versus midazolam for sedation during percutaneous transluminal angioplasty

PURPOSE

To prospectively and randomly compare use of propofol versus midazolam for sedation during percutaneous transluminal angioplasty (PTA).

MATERIALS AND METHODS

Forty patients (27 men, 13 women; mean age 64.4 years +/- 12.2) who underwent PTA of the arteries below the diaphragm were prospectively randomized for sedation with propofol or midazolam. Both drugs were administered after an initial bolus injection by means of continuous infusion to achieve conscious sedation at levels II-III according to the Ramsay classification. Patients and interventionalists were blinded to the applied sedative. Both groups were similar with regard to American Society of Anesthesiology status, heart rate, blood pressure, arterial oxygen pressure (pO2), arterial carbon dioxide pressure (pCO2), arterial oxygen saturation (SpO2), and visual analogue scores for general condition, anxiety, and pain. During PTA, heart rate, blood pressure, and pulse oximetry (tpO2) were monitored continually. Every 30 minutes, an arterial blood gas analysis was performed. Visual analogue scores were obtained before, during, and after intervention.

RESULTS

Decreases in SpO2, pO2, and tpO2 were significantly greater after sedation with midazolam (P < .05; t test). The increase in pCO2 was significantly greater after midazolam (P < .05; t test). No significant difference between the drugs was found with regard to any of the other parameters. Both drugs resulted in sufficient sedation and anxiolysis (P < .01 for both drugs for visual analogue score for anxiety before and during PTA; matched pairs test). Satisfaction of the interventionalist was significantly greater for propofol (P < .05; t test).

CONCLUSION

Propofol causes less respiratory depression than midazolam for equivalent sedation and anxiolysis in patients undergoing PTA.