Modeling the Anesthetic Effect of Ropivacaine after a Femoral Nerve Block in Orthopedic Patients
Bibliographic record
Abstract
AbstractAbstract A population pharmacokinetic–pharmacodynamic model was developed that describes the relationship between sensory response and the amount of ropivacaine remaining at the site of injection after single-dose injection for femoral nerve block. Simulation using the model suggests that following a bolus dose of 100 mg, 0.2% ropivacaine hydrochloride should be infused at least at 3 ml/h to maintain a complete sensory block for 48 h. Background: Even though ropivacaine is frequently used during orthopedic surgery, the relationship between plasma concentrations and degree of sensory anesthesia after a peripheral nerve block is currently unknown. The aim of this study was to characterize this relation using population pharmacokinetic–pharmacodynamic modeling. Methods: Femoral nerve block was performed by the anterior approach using a single injection (20 ml) of 0.5% ropivacaine hydrochloride in 20 patients scheduled for total knee arthroplasty under spinal anesthesia. Sensory thresholds in response to a gradual increase in transcutaneous electrical stimulation (primary endpoints), loss and recovery of ice-cold sensation, as well as total ropivacaine plasma concentrations were determined up to 4 days after administration of the local anesthetic. Using NONMEM (ICON, USA), sensory block was modeled by assuming an equilibration delay ( k e0 ) between amount in the depot and effect-site compartments. Results: Mean effect-site amount producing 90% of the maximum possible effect ( AE 90 ) was estimated as 20.2 mg. At 2 × AE 90 , the sigmoid E max model predicted a mean onset time of 23.4 min and mean duration of 22.9 h. Interindividual variability (IIV) for AE 50 was 49%. Typical k e0 half-life was 34.7 min (IIV = 52%) and steepness parameter 8.7 (IIV = 48%). None of the pharmacodynamic model parameters showed sex, age, or body weight dependency. Conclusions: A population pharmacokinetic/pharmacodynamic model was developed that quantitatively describes the sensory component of a femoral nerve block in orthopedic patients. Further clinical studies will be needed to validate the clinical relevance of this finding.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".