Influence of rate of administration on the mechanism behind propofol induced loss of consciousness

BACKGROUND

Propofol effect-site time course models included in TCI systems have been under discussion. We hypothesized that the rate of administration is a major contributor affecting the construction of a useful effect-site model: yielding different plasmatic concentrations, loss of consciousness may occur by different mechanisms more complex than the pharmacological effect-site.

METHODOLOGY

ASA III patients were randomized in two groups: rapid induction (RI) received TCI of propofol effect-site (CeCALC) 5.4 μg/mL (modified Marsh model), and slow induction (SI) propofol infusion of 10 mg/kg/hour. A neurologist, blinded to induction method, performed neurological assessments using the FOUR score until the loss of consciousness (LOC). At LOC, the presence of brain stem reflexes, EEG index (PSI) and infusion time/mass of drug were registered. Fisher's exact test was used to describe differences between brain stem reflexes and respiration components of the FOUR score and CeCALC for 4 propofo models at LOC time.

RESULTS

16 patients divided in two groups were included. All patient in SI had brainstem reflexes free at LOC. In the RI, all patients had brain stem reflexes abolished and 1 patient had B and R of 4 points in the FOUR score (brain stem reflexes unaffected; P < .001). CeCALC at LOC time were contradictory at LOC in both groups and using 4 different Pk/Pd models.

CONCLUSIONS

Depending of the infusion rate, propofol CeCALC at LOC calculated by different Pk/Pd models could be the source of confuse data to be used to guide the state of general anesthesia.

Influence of rate of administration on the mechanism behind propofol induced loss of consciousness

BACKGROUND

Propofol effect-site time course models included in TCI systems have been under discussion. We hypothesized that the rate of administration is a major contributor affecting the construction of a useful effect-site model: yielding different plasmatic concentrations, loss of consciousness may occur by different mechanisms more complex than the pharmacological effect-site.

METHODOLOGY

ASA III patients were randomized in two groups: rapid induction (RI) received TCI of propofol effect-site (CeCALC) 5.4 μg/mL (modified Marsh model), and slow induction (SI) propofol infusion of 10 mg/kg/hour. A neurologist, blinded to induction method, performed neurological assessments using the FOUR score until the loss of consciousness (LOC). At LOC, the presence of brain stem reflexes, EEG index (PSI) and infusion time/mass of drug were registered. Fisher's exact test was used to describe differences between brain stem reflexes and respiration components of the FOUR score and CeCALC for 4 propofo models at LOC time.

RESULTS

16 patients divided in two groups were included. All patient in SI had brainstem reflexes free at LOC. In the RI, all patients had brain stem reflexes abolished and 1 patient had B and R of 4 points in the FOUR score (brain stem reflexes unaffected; P < .001). CeCALC at LOC time were contradictory at LOC in both groups and using 4 different Pk/Pd models.

CONCLUSIONS

Depending of the infusion rate, propofol CeCALC at LOC calculated by different Pk/Pd models could be the source of confuse data to be used to guide the state of general anesthesia.

Pharmacodynamic study of the cardiovascular polypill. Is there any interaction among the monocomponents?

INTRODUCTION AND OBJECTIVES

To compare the pharmacodynamics of the CNIC polypill (atorvastatin 40mg/ramipril 10mg/aspirin 100mg) in terms of low-density lipoprotein cholesterol (LDL-C) and systolic blood pressure (SBP), with the corresponding reference products (atorvastatin and ramipril).

METHODS

This was a multicenter, randomized, open-label, and parallel 3-arm study comparing the effect of the CNIC polypill vs ramipril 10mg and atorvastatin 40mg on SBP and LDL-C. The coprimary endpoints were differences in the adjusted mean 24-hour SBP (using ambulatory BP measurement) and LDL-C during the study period estimated using an ANCOVA model.

RESULTS

Of the 241 patients included in the per protocol population, 84 received the CNIC polypill (group A), 84 atorvastatin (group B), and 73 ramipril (group C). SBP decreased from 139.3±12.5 to 133.2±12.9mmHg in group A and from 138.1±11.9 to 134.0±12.8mmHg in group C (baseline adjusted mean difference for the decrease in SBP was 1.77mmHg (90%CI, -0.5 to 4.0) in favor of group A, without reaching statistical significance. LDL-C was reduced by 33.9±21.6 and 29.2±25.8mg/dL in groups A and B, respectively (baseline adjusted mean difference for the decrease in LDL-C was 7.0% (90%CI, 1.5-12.4), a significantly greater decrease with the polypill). The 3 treatments were well tolerated.

CONCLUSIONS

The results of this study rule out a negative effect on blood pressure of the interaction between the components of the CNIC polypill. The reduction in LDL-C was greater in the CNIC polypill group, suggesting a synergistic effect of the components.