90% Effective Dose of Phenylephrine Infusions Under Intensive and Standard Treatment

Study Overview
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Brief Summary
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The objective of this study is to investigate the 90% effective dose of phenylephrine infusions for preventing postspinal anesthesia hypotension under intensive and standard treatment during cesarean section

Detailed Description
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Post-spinal anesthesia hypotension is a frequent complication during spinal anesthesia for cesarean section. The incidence of post-spinal anesthesia hypotension is as high as 62.1-89.7% if prophylactic measures are not taken. The 2016 ASA guidelines for obstetric anesthesia suggest avoiding hypotension following spinal anesthesia in women and emphasize the use of vasopressors, specifically alpha-receptor agonists, as the preferred strategy to prevent and manage post-spinal anesthesia hypotension. The 2018 International Consensus in the United Kingdom and Northern Ireland recommends maintaining maternal systolic blood pressure above 90% of the baseline value following lumbar anesthesia, while avoiding dropping below 80% of the baseline value. Currently, the threshold for maintaining blood pressure above 80% of the baseline value is widely adopted as a standard; however, limited evidence supports the advantage of sustaining maternal blood pressure above 90% of the baseline value. The objective of this study is to investigate the 90% effective dose of phenylephrine infusions for preventing postspinal anesthesia hypotension under intensive and standard treatment during cesarean section.

Official Title
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90% Effective Dose of Phenylephrine Infusions for Preventing Postspinal Anesthesia Hypotension Under Intensive and Standard Treatment During Cesarean Section

Conditions
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Adverse Effect

Intervention / Treatment
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* Drug: Alpha-Agonist
* Drug: α-adrenergic receptor agonist


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: 18-45 years Primipara or multipara Singleton pregnancy ≥37 weeks American Society of Anesthesiologists physical status classification I to II Scheduled for cesarean section under spinal anesthesia Exclusion Criteria: Body height < 150 cm Body weight > 100 kg or body mass index (BMI) ≥ 40 kg/m2 Eclampsia or chronic hypertension or baseline blood pressure ≥180 mmHg Hemoglobin < 7g/dl

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Standard group<br>The maternal systolic blood pressure was consistently maintained above 80% of the preoperative baseline value from the initiation of spinal anesthesia until fetal delivery. | Drug: Alpha-Agonist<br>* An initial infusion dose of prophylactic phenylephrine (0.625 ug/kg/min) simultaneous with spinal anesthesia. The dose administered to subsequent patients varied by increments or decrements of 0.125 ug/kg/min of prophylactic phenylephrine according to the responses of previous patients according to the up-down sequential allocation.<br>* Other names: norepinephrine;|
| Other: Intensive group<br>The maternal systolic blood pressure was consistently maintained above 90% of the preoperative baseline value from the initiation of spinal anesthesia until fetal delivery. | Drug: α-adrenergic receptor agonist<br>* An initial infusion dose of prophylactic phenylephrine (0.625 ug/kg/min) simultaneous with spinal anesthesia. The dose administered to subsequent patients varied by increments or decrements of 0.125 ug/kg/min of prophylactic phenylephrine according to the responses of previous patients according to the up-down sequential allocation.<br>* Other names: norepinephrine;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| ED50 and ED90 | The dose of prophylactic phenylephrine that would be effective in preventing postspinal anesthesia hypotension in 50% (effective dose, ED 50) and 90% (ED90) of patients | 1-15 minutes after spinal anesthesia | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The incidence of post-spinal anesthesia hypotension | Systolic blood pressure (SBP) < 80% of the baseline | 1-15 minutes after spinal anesthesia. | 
| The incidence of severe post-spinal anesthesia hypotension. | Systolic blood pressure (SBP) < 60% of the baseline. | 1-15 minutes after spinal anesthesia. | 
| The incidence of bradycardia. | Heart rate < 60 beats/min. | 1-15 minutes after spinal anesthesia. | 
| The incidence of nausea and vomiting. | Presence of nausea and vomiting in patients after spinal anesthesia | 1-15 minutes after spinal anesthesia. | 
| The incidence of hypertension. | Systolic blood pressure (SBP) >120% of the baseline. | 1-15 minutes after spinal anesthesia. | 
| pH | From umbilical arterial blood gases. | Immediately after delivery | 
| Base excess | From umbilical arterial blood gases. | Immediately after delivery | 
| Partial pressure of oxygen (PO2) | From umbilical arterial blood gases. | Immediately after delivery | 
| APGAR score | A= Appearance P=Pulse G=Grimace A=Attitude R=Respiration; 0(Worst)-10(Best) | 1 min after delivery | 
| APGAR score | A= Appearance P=Pulse G=Grimace A=Attitude R=Respiration; 0(Worst)-10(Best) | 5 min after delivery |