The effect of renal impairment and obesity on anti-Xa peak and trough levels in patients receiving therapeutic doses of nadroparin: a comparison with control patients.

PURPOSE: Anti-Xa peak level monitoring is recommended during LMWH treatment in renal impairment or obesity. The trough level has been proposed as marker for bleeding. We studied the influence of renal impairment and obesity on anti-Xa levels. METHODS: Peak and trough levels were collected during therapeutic nadroparin treatment in patients with renal impairment, obese patients, and controls. 27 patients (n = 68 samples) were evaluated and combined with published data (n = 319 samples from 35 patients) using population pharmacokinetic (popPK) modelling. RESULTS: Median peak level was 0.44 and 0.95 IU/mL in renal impairment with and without dose reduction and 0.60 and 0.43 IU/mL in obesity and controls, respectively. Trough levels were < 0.5 IU/mL in all patients with renal impairment with dose reduction and in 5/6 control patients. In the popPK model, total body weight and eGFR were covariates for clearance and lean body weight for distribution volume. Model-based evaluations demonstrated peak levels below the therapeutic window in controls and increased levels in renal impairment. Dose reductions resulted in a different effect on peak and trough levels. Obese patients (BMI up to 32 kg/m2) had similar levels upon weight-based dosing. CONCLUSION: In renal impairment, anti-Xa peak levels after dose reduction are comparable to those in controls. Weight-based dosing is suitable for obese patients. Aiming for peak levels between 0.6 and 1.0 IU/mL in these patients would result in overexposure compared to controls. Considering the association of trough levels and bleeding risk and our findings, trough monitoring seems to be a suitable parameter to identify nadroparin accumulation.

Disease severity is a major determinant for the pharmacodynamics of propofol in critically ill patients.

As oversedation is still common and significant variability between and within critically ill patients makes empiric dosing difficult, the population pharmacokinetics and pharmacodynamics of propofol upon long-term use are characterized, particularly focused on the varying disease state as determinant of the effect. Twenty-six critically ill patients were evaluated during 0.7-9.5 days (median 1.9 days) using the Ramsay scale and the bispectral index as pharmacodynamic end points. NONMEM V was applied for population pharmacokinetic and pharmacodynamic modeling. Propofol pharmacokinetics was described by a two-compartment model, in which cardiac patients had a 38% lower clearance. Severity of illness, expressed as a Sequential Organ Failure Assessment (SOFA) score, particularly influenced the pharmacodynamics and to a minor degree the pharmacokinetics. Deeper levels of sedation were found with an increasing SOFA score. With severe illness, critically ill patients will need downward titration of propofol. In patients with cardiac failure, the propofol dosages should be reduced by 38%.

Propofol 6% as sedative in children under 2 years of age following major craniofacial surgery.

BACKGROUND: After alarming reports concerning deaths after sedation with propofol, infusion of this drug was contraindicated by the US Food and Drug Administration in children <18 yr receiving intensive care. We describe our experiences with propofol 6%, a new formula, during postoperative sedation in non-ventilated children following craniofacial surgery. METHODS: In a prospective cohort study, children admitted to the paediatric surgical intensive care unit following major craniofacial surgery were randomly allocated to sedation with propofol 6% or midazolam, if judged necessary on the basis of a COMFORT behaviour score. Exclusion criteria were respiratory infection, allergy for proteins, propofol or midazolam, hypertriglyceridaemia, familial hypercholesterolaemia or epilepsy. We assessed the safety of propofol 6% with triglycerides (TG) and creatine phosphokinase (CPK) levels, blood gases and physiological parameters. Efficacy was assessed using the COMFORT behaviour scale, Visual Analogue Scale and Bispectral Index monitor. RESULTS: Twenty-two children were treated with propofol 6%, 23 were treated with midazolam and 10 other children did not need sedation. The median age was 10 (IQR 3-17) months in all groups. Median duration of infusion was 11 (range 6-18) h for propofol 6% and 14 (range 5-17) h for midazolam. TG levels remained normal and no metabolic acidosis or adverse events were observed during propofol or midazolam infusion. Four patients had increased CPK levels. CONCLUSION: We did not encounter any problems using propofol 6% as a sedative in children with a median age of 10 (IQR 3-17) months, with dosages <4 mg kg(-1) h(-1) during a median period of 11 (range 6-18) h.