Up-Down Determination of the 90% Effective Dose of Phenylephrine for the Treatment of Spinal Anesthesia-Induced Hypotension in Parturients Undergoing Cesarean Delivery
Bibliographic record
Abstract
INTRODUCTION: Hypotension frequently complicates spinal anesthesia for cesarean delivery, and vasopressors are the mainstay for treatment. The most effective dose of phenylephrine for the treatment of spinal anesthesia-induced hypotension has not been estimated. METHODS: Healthy nonlaboring women undergoing a cesarean delivery were recruited. All women received spinal anesthesia using hyperbaric bupivacaine 12 mg with fentanyl and morphine. Each subject received an i.v. crystalloid fluid bolus before and at the time of initiation of spinal anesthesia (preload and coload). An up-down sequential allocation method using the biased-coin design was used to estimate the 90% effective dose (ED(90)) of phenylephrine. The assigned phenylephrine dose was based on the response of the preceding subject. If the systolic blood pressure (SBP) decreased > 20% of baseline (i.e., SBP 20%) or to an SBP < 90 mm Hg, the assigned dose of phenylephrine was administered. If the SBP returned to within 20% of baseline or > or = 90 mm Hg within 1 min, this was considered a success, otherwise it was a failure. The initial dose of phenylephrine was 100 microg. The ED(90) with 95% confidence intervals (CIs) was calculated using the maximum likelihood estimation and Firth logistic regression. RESULTS: Sixty-nine subjects were screened to participate, of whom 66 subjects consented. Forty-five of the enrolled subjects experienced spinal anesthesia-induced hypotension and received a blinded dose of phenylephrine. Those subjects who developed hypotension received doses of phenylephrine between 80 and 180 microg. No subjects experienced hypertension. Determined with the maximum likelihood estimation method, the ED(90) of phenylephrine was 147 microg (95% CI, 98-222 microg). With Firth regression, the probability of a successful response at 150 microg is 90.5% (95% CI, 66.0%-99.0%). CONCLUSION: In this study, we estimated that the ED(90) of phenylephrine required to treat spinal anesthesia-induced hypotension in cesarean delivery is approximately 150 microg.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.007 |
| 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) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".