Population Pharmacodynamic Modeling of the Sedative and Side Effects of Propofol

Study Overview
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Brief Summary
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Sedation during spinal anesthesia is very useful for patients' comfort. However, intermittent bolus of sedative frequently results in inappropriate sedation which comes with various side effects such as patients' discomfort and apnea. Therefore, it would be reasonable to use target-controlled infusion(TCI) to provide proper sedation without serious side effects. In this study, the investigators try to find the appropriate propofol target concentration with TCI device and build a pharmacodynamic non-linear mixed effect model between propofol target concentration and side effects.

Official Title
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Population Pharmacodynamic Modeling of the Sedative and Side Effects of Propofol in Patients Undergoing Spinal Anesthesia

Conditions
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Surgery Related to Lower Extremity Under Spinal Anesthesia

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: patients who have lower extremity surgery under spinal anesthesia and who want to be sedated Exclusion Criteria: patients who have deafness, neurologic deficit, Glasgow coma scale less than 15, history of drug allergy and who are on central nervous system-related drugs,

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| sedation score | Sedation score will be assessed with 'Modified Observer's assessment of alertness/sedation (OAA/S) score'. It has 5 scales from 1 to 5 as followed. responds readily to name spoken in normal tone lethargic response to name spoken in normal tone responds only after name is spoken loudly and/or repeatedly responds only after mild prodding or shaking does not respond to mild prodding or shaking After induction of spinal anesthesia, patient will be sedated with propofol via TCI device. The infusion dose will be adjusted every 5 minutes until the OAA/S score reaches 4. The patient's OAA/S score will be assessed overtime the infusion dose is adjusted during sedation. At the same time, airway obstruction score will be assessed and if the score reaches 4, the dose will be reduced. | every 5 minutes when the dose is adjusted up to 1 hour | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| airway obstruction score | Airway obstruction score will be assessed as followed. normal breathing deep breathing snoring severe airway obstruction After induction of spinal anesthesia, patient will be sedated with propofol via TCI device. The infusion dose will be adjusted every 5 minutes until the OAA/S score reaches 4. The patient's OAA/S score will be assessed overtime the infusion dose is adjusted during sedation. At the same time, airway obstruction score will be assessed and if the score reaches 4, the dose will be reduced. | every 5 minutes when the dose is adjusted up to 1 hour |