Modelagem farmacocinética-farmacodinâmica do propofol em pacientes submetidos à cirurgia cardíaca com anestesia venosa contínua alvo-controlada / Propofol pharmacokinetic-pharmacodynamic modeling in patients submitted to cardiac surgery with continuos venous target controlled anesthesia

O propofol é um sedativo eficiente, largamente empregado em anestesia e geralmente associado a grande números de analgésicos opióides em cirurgias de grande porte, como a cirurgia cardíaca de revascularização do miocárdio (RM) com ou sem circulação extracorpórea (CEC). Devido às suas características farmacocinéticas é administrado através de infusão alvo controlada (TCI) de forma a manter os níveis plasmáticos ótimos para obtenção de sedação e profundidade de anestesia adequadas durante a intervenção cirurgica. O objetivo do presente estudo foi investigar a famacocinética e farmacodinâmica do propofol administrado através de TCI em pacientes submetidos a RM com e sem CEC. Na administração da medicação hipnótica, fez-se necessária a validação do Diprifusor (AstraZeneca), incluindo a bomba de infusão e o software programado com o modelo famacocinético de 3 compartimentos, que necessita apenas da inclusão de dados individuais do paciente, tais como peso corporal...

Propofol is an effective sedative, largely applied in anesthesia and in general it is associated to opioids for analgesia in major surgeries, like the cardiac surgery to coronary artery bypass grafting (CABG) with or without cardiopulmonary bypass (CPB). It is administered by a target controlled infusion system (TCI) to maintain the optimal depth of sedation and anesthesia during the intervention, due to its pharmacokinetic characteristics. The objective of this study was to investigate the influence of CPB in pharmacokinetics and in pharmacodynamics of propofol, applying PK-PD modeling. For drug administration, Diprifusor (AstraZeneca), including pump plus software must enter individual data as body weight from the patient, once pharmacokinetic parameters were included previously. To validate this system of infusion, the prediction error by target controlled infusion must be estimated by comparison between obtained and predict concentration plasma ratio. In the present protocol, 20 patients (10 CONTROL and 10 CPB) were selected based on inclusion criteria for the comparative study. Patients were informed in details about the investigation and before the protocol starts, they signed the informed written consent to participate of the study. Protocol was approved by the local ethical committees of all institutions involved. Rate of infusion and the range of obtained plasma propofol concentrations required to reach 2 µg/mL and to maintain the bispectral index (BIS:40) during cardiac surgery were monitored. Subsequently, at the end of surgery, both rate of infusion and range of obtained plasma propofol concentrations required to reach 1 µg/mL were monitored either. Depth of sedation was assessed with BIS during all period reaching maximum effect in 40 at level of sedation in the operative period. At the end of surgery, the Ramsay score achieved sedation level 6, when the target plasma propofol was adjusted to 1 µg/mL; Additionally, at the end of infusion in the postoperative period, BIS and Ramsay were monitored simultaneously up to 18-20 hours for all patients. Blood samples were collected and propofol plasma levels were monitored during (TCI : 2 µg/mL) and after surgery (TCI: 1 µg/mL). Blood samples also were collected at the end of infusion for pharmacokinetics. Volumes of blood lower than 90 mL were necessary for drug monitoring and pharmacokinetic purposes. Plasma levels were determined by a quite simple, selective, sensitive and robustness analytical method HPLC, using fluorescence detector, C18 column, and binary system at low flow rate. Confidence limits were: 0.1-10 µg/mL (linearity, r2 0.9977), 0.05 µg/mL(LD), 0.1 flg/mL(LQ), 93.9% (absolute recovery), 8.4 and 8.8% (intra and inter day precision), 91.8 and 93.3% (accuracy intra and inter day). Additionally, good stability was shown for the drug and its internal standard (tymol). Plasma levels showed a large fluctuation for the CONTROL compared to CPB in the perioperative period, mainly during the surgical intervention, indicating a higher predicting error for CONTROL group. Pharmacokinetics applying three compartment open model showed significant increases on drug elimination (ClT, ß, γ) for CPB compared to CONTROL, once plasma levels for CPB Group were lower than CONTROL in the period of study.

Obesity influences propranolol pharmacokinetics in patients undergoing coronary artery bypass grafting employing cardiopulmonary bypass

Propranolol plasma levels and kinetic disposition may be altered by hypoyhermic cardiopulmonary bypass (CPB-H). We investigated the potential influence of obesity on propranolol pharmacokinetics in patients undergoing coronary artery bypass grafting employing CPB-H. Fifteen patients, receiving propranolol perorally pre-(10-40 mg, 2-3 times a day) and post-operatively (10 mg, once a day) were distributed in two groups, based on body mass index (BMI), in obese (n=9, BMI: mean 29,4 kg/m²) and non-obese (n=6 BMI: mean 24.8 kg/m²). A serial of blood samples was collected at the pre- and post-operative periods at time dosing interval (`tau´) propranolol plasma levels were measured one day before and after surgery using a high performance liquid chromatographic procedure described previously...

Pharmacotherapy up to date. Individualization of drug theraphy in Brazil Clinical pharmacokinetics-pharmacokinetics/PK and pharmacodynamics/PD

Pharmacokinetic concepts have been successfully used to individualize patient drug therapy. Many factors must be taken into consideration when deciding on the best drug dosis for a patient, as the age, gender, obesity and disease state. The enantioselective pharmacokinetics is another important factor to be considered. In most cases, one of the isomers is more pharmacologically active than the other, and each one may exhibit different pharmacolokinetic properties. Genetics also plays a role in the interindividual variability since the activity of many CYP isozymes is genetically determined. Extensive metabolizers have the gene for the isozyme and metabolize the drugs normally. Poor metabolizers may...

High performance liquid chromatography to determine propranolol in plasma. Drug accumulation in post-surgical patients

An improved, simple and sensitive micromethod based on HPLC-fluorescence is described for quantification of propranolol in plasma. Only 200µL of biological sample were required. The drug and its internal standard (verapamil) are eluted after 3.6 and 8.5 min, respectively, from a 4-micron `C IND. 18ï reverse-phase column using a mobile phase consisting of 0.38 M acetate buffer, pH 5.0 and acetonitrile (65:35, v/v, isocratically) with detection at `lâmbda IND. exï- 290 nm and `lâmbda IND. emï - 358 nm. This method, validated on basis of parameters evaluated for the confidence limits of propranolol measurements in spiked blank plasma, presented 1 ng/mL sensitivity, 1-1000 ng/mL linearity, 6.2 per cent and 7.6 per cent for intra- and inter-assay precision respectively, good accuracy and high selectivity...