Phenylephrine Bolus Research Articles

Cerebral desaturation and delirium in patients having non-cardiac surgery - a pilot study

BackgroundPostoperative delirium (POD) is associated with increased short- and long-term mortality and several risk factors have been described. Decreased regional cerebral oxygen saturations (rScO2) may be a modifiable risk factor for POD yet its measurement is not used in routine clinical practice. AimsThe primary aim of this study was to assess the feasibility of measuring rScO2 and screening for POD in patients over 60 years of age having non-cardiac surgery. Our secondary aim was to perform exploratory analyses of the relationship between boluses of intra-operative vasopressor and rScO2 values. MethodsrScO2 were recorded in 60 patients over the age of 60 years having non-cardiac surgery in a single centre. Patients were screened daily for delirium for up to 7 days of the inpatient stay or until discharge, which ever occurred sooner. ResultsOf the 60 patients recruited, 58 underwent complete daily assessment for POD. Of those, 2 developed POD (3.4%). Patients that developed POD tended to be older, but no other statistically significant differences were observed. Analysis of the effect of phenylephrine boluses on rScO2 observed a ‘rise, drop, return’ pattern in an 8-minute window post-bolus administration. ConclusionThe study protocol was found to be feasible to deliver. The study was unable to find any associations between rScO2 and POD, however, the study identified a relationship between intraoperative vasopressor boluses and subsequent rScO2.

A Randomized comparative study: Prophylactic use of phenylephrine infusion versus phenylephrine bolus to treat hypotension in caesarean section patients

A Randomized comparative study: Prophylactic use of phenylephrine infusion versus phenylephrine bolus to treat hypotension in caesarean section patients

Comparison of bolus phenylephrine, Ephedrine and Mephentermine for maintenance of arterial pressure during Spinal anaesthesia in Caesarean section

Background: Hemodynamic changes during cesarean delivery after spinal anesthesia are common. The hypotension seen after spinal anesthesia in a cesarean delivery can be treated by many agents. In the management of hypotension during spinal anesthesia for cesarean section, the effects of Phenylephrine, Ephedrine and Mephentermine were compared in this study based on the following parameters-1. The efficacy of the vasopressor in treating hypotension 2. Incidence of undesirable side effects. Materials and method: This study included a total of 120 patients (ASA Grade I and II) undergoing elective cesarean section (with a normal singleton pregnancy, full term/near term) under spinal anesthesia. The patients were randomly allocated into three groups of 40 each. Group ‘P’ was given prophylactic bolus dose of Phenylephrine 100 mcg IV, Group ‘E’ was given prophylactic bolus dose of Ephedrine 10 mg IV and Group ‘M’ received prophylactic bolus dose of Mephentermine 6 mg IV. Blood pressure and heart rate was recorded every 2 minutes for 20 minutes and thereafter every 5 minutes till the end of the surgery. Results: In managing hypotension between the three groups, no difference was found between them. The incidence of bradycardia was higher in the Phenylephrine group. Conclusion: All the three vasopressors are effective (in intravenous form) in maintenance of maternal arterial pressure. Although Phenylephrine has quicker peak effect, in comparison to Ephedrine and Mephentermine and it causes reduction in heart rate.

A comparative study of bolus phenylephrine and mephentermine for treatment of hypotension during spinal anaesthesia for caesarean section

Background: Spinal anesthesia for caesarean section has several advantages over general anaesthesia like decreased risk of failed intubation, decreased risk of pulmonary aspiration of gastric contents, avoidance of the depressant effects of general anesthetics on neonate etc.Aim and Objectives: This comparative study was designed to evaluate the efficacy of Mephentermine and Phenylephrine in treating hypotension during spinal anaesthesia for cesarean section. The incidence of undesirable side effects like maternal bradycardia, nausea and vomiting also noted.Methodology: The study was conducted in the Department of OBG the Maternity Hospital, Osmania Medical College during the year August 2018- November 2019.The study includes 60 patients grouped into two groups.Results: Both Phenylephrine and Mephentermine maintained the arterial pressure effectively within 20% of baseline values. The mean value of heart rate was high in Mephentermine group compared with Phenylephrine group. The mean values of Systolic BP, Diastolic BP and MAP were higher in Phenylephrine group compared with Mephentermine group throughout the study period. Phenylephrine group required fewer number of bolus doses when compared with Mephentermine. The heart rate generally remained low throughout the study period in Phenylephrine group and the incidence of bradycardia was more in Phenylephrine group when compared with Mephentermine group. The occurrence of nausea and vomiting were similar in both groups.Conclusion: Thus, it can probably enhance organ blood flow more than mephentermine. Mephentermine increases heart rate and thus may be avoided in population where the effect may be detrimental.

Evaluation of analgesic, sympathetic and motor effects of 1% and 2% lidocaine administered epidurally in dogs undergoing ovariohysterectomy

ObjectiveTo compare, versus a control, the sensory, sympathetic and motor blockade of lidocaine 1% and 2% administered epidurally in bitches undergoing ovariohysterectomy. Study designRandomized, blinded, controlled clinical trial. AnimalsA total of 24 mixed-breed intact female dogs. MethodsAll dogs were administered dexmedetomidine, tramadol and meloxicam prior to general anesthesia with midazolam–propofol and isoflurane. Animals were randomly assigned for an epidural injection of lidocaine 1% (0.4 mL kg−1; group L1), lidocaine 2% (0.4 mL kg−1; group L2) or no injection (group CONTROL). Heart rate (HR), respiratory rate (fR), end-tidal partial pressure of carbon dioxide (Pe′CO2), and invasive systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures were recorded every 5 minutes. Increases in physiological variables were treated with fentanyl (3 μg kg−1) intravenously (IV). Phenylephrine (1 μg kg−1) was administered IV when MAP was <60 mmHg. Postoperative pain [Glasgow Composite Pain Score – Short Form (GCPS–SF)] and return of normal ambulation were recorded at 1, 2, 3, 4 and 6 hours after extubation. ResultsThere were no differences over time or among groups for HR, fR, Pe′CO2 and SAP. MAP and DAP were lower in epidural groups than in CONTROL (p = 0.0146 and 0.0047, respectively). There was no difference in the use of phenylephrine boluses. More fentanyl was administered in CONTROL than in L1 and L2 (p = 0.011). GCPS–SF was lower for L2 than for CONTROL, and lower in L1 than in both other groups (p = 0.001). Time to ambulation was 2 (1–2) hours in L1 and 3 (2–4) hours in L2 (p = 0.004). Conclusions and clinical relevanceEpidural administration of lidocaine (0.4 mL kg−1) reduced fentanyl requirements and lowered MAP and DAP. Time to ambulation decreased and postoperative pain scores were improved by use of 1% lidocaine compared with 2% lidocaine.

A Clinical Trial on the Effects of Different Regimens of Phenylephrine on Maternal Hemodynamic After Spinal Anesthesia for Cesarean Section.

BackgroundPhenylephrine is used to prevent and treat hypotension during spinal anesthesia for cesarean delivery.ObjectivesThe present study aims to investigate the effects of different regimens of phenylephrine on blood pressure of candidates for the cesarean section.MethodsIn this double-blind, randomized clinical trial, a total of 120 candidates of elective cesarean delivery under spinal anesthesia was randomly categorized into three groups. Groups 1, 2, and 3 received bolus and prophylactic saline (control group), prophylactic bolus phenylephrine (100 µg), and prophylactic phenylephrine infusion (50 µg/min), respectively. The incidence of hypotension, maternal hemodynamics, hypertension, rescue phenylephrine dose, nausea, and vomit were compared between the groups.ResultsIn all the three groups, the incidence of nausea and vomit, bradycardia, hypertension, and neonatal Apgar score were not statistically different (P > 0.05). However, the adjuvant phenylephrine dose requirement was remarkably different. Moreover, the mean systolic blood pressure differed significantly in the second and 7th minutes after the spinal block (P < 0.05). 35% in the first group, 15% in the second group, and 2.5% in the third group had hypotension (P = 0.001). Apart from the first measurement after spinal anesthesia, the mean heart rate showed no significant difference between the groups.ConclusionsThe use of prophylactic phenylephrine infusion is recommended to control the optimal blood pressure in parturients undergoing cesarean section after spinal anesthesia.

Hypotension after spinal anaesthesia is not always the rule in parturients undergoing caesarean section

Background General anaesthesia is a real challenge for the anaesthetist when anaesthetizing obstetric patients due its well-known complications of difficult intubation and thereby increasing morbidity and mortality of pregnant women. These risks can be easily avoided by regional anaesthesia. Spinal anaesthesia is frequently associated with hypotension which can have detrimental effects both on the mother and the neonate. Prophylactic phenylephrine administration had been widely practiced to prevent post-spinal hypotension during caesarean section. The goal of this study is to prove and determine that it is not always necessary to use a vasoconstrictor to avoid hypotension after spinal anesthesia for parturients undergoing caesarean section.Method We enrolled 100 patients in this randomized controlled study who were having elective caesarean delivery. Spinal anaesthesia was performed under aseptic conditions. Immediately following spinal blockade, patients were randomly allocated to receive either a single bolus of phenylephrine 100 μg in a volume of 10 ml, or equivalent volume of normal saline 0.9%. Incidence of post-spinal hypotension was used as the primary outcome. Maternal haemodynamic parameters, intraoperative nausea and vomiting, the need for phenylephrine or glycopyrrolate administration, neonatal Apgar score at 1, 5 minutes, and base excess (BE) value of the neonatal umbilical venous blood were all recorded and reflected the secondary outcomes.Results There was no significant difference regarding the incidence of post-spinal hypotension in phenylephrine and placebo group. There was no difference in neonatal Apgar score at 1, 5 minutes, and base excess in both groups.ConclusionThe present study demonstrated that it is not necessary to provide a vasoconstrictor to avoid hypotension that results from spinal anaesthesia in caesarean sections.

Effectiveness of intravenous boluses of phenylephrine, ephedrine and mephentermine as vasopressors for management of perioperative hypotension in elective lower segment caesarean section under spinal anaesthesia – A prospective comparative study

Hypotension after subarachnoid block for caesarean section is the commonest but serious complication encountered by anaesthesiologists. Various vasopressors are used to prevent/treat this complication. This study was done to compare the efficacy of three commonly used vasopressors – phenylephrine, ephedrine, mephentermine for treatment of perioperative hypotension. Sixty American Society of Anaesthesiologists (ASA) physical status class II parturients undergoing elective caesarean section under subarachnoid block were randomly allotted three groups (P, E, M) (n = 20) to receive intravenous boluses of phenylephrine 100 mcg, ephedrine 6mg &amp; mephentermine 6mg respectively, following hypotension. Maternal Haemodynamic parameters, complications &amp; neonatal APGAR scores were recorded. P-value &amp;#60; 0.05 was considered significant and P-value &amp;#60; 0.001 considered highly significant. Demographic values, baseline vital parameters and mean number of vasopressor boluses required were similar in the three groups (P &amp;#62; 0.05). The mean trends of systolic blood pressure (P = 0.06), diastolic blood pressure (P = 0.7) and mean arterial pressure (P = 0.6) were similar in the three groups. Heart rate was raised during periods of hypotension; the mean heart rate was lower in the phenylephrine group after vasopressor administration. The overall trend was similar (P = 0.1) among the three groups. There was (P = 0.003) higher incidence of bradycardia in the phenylephrine group. The neonatal APGAR scores were &amp;#62; 7 in the three groups at the 1st and 5th minute (P = 0.5). All three vasopressors effectively maintained arterial blood pressure during the subarachnoid block for caesarean section. Phenylephrine caused a significant reduction in heart rate compared to ephedrine or mephentermine.

Uterine Exteriorization Compared With In Situ Repair of Hysterotomy After Cesarean Delivery: A Randomized Controlled Trial.

To compare the effect of exteriorized with in situ uterine repair on intraoperative nausea and vomiting during elective cesarean delivery under spinal anesthesia using a phenylephrine infusion. This study was a randomized double-blinded controlled trial of 180 women undergoing elective cesarean delivery using a standardized anesthetic protocol. Patients were randomized to exteriorization (n=90) or in situ uterine repair (n=90). The spinal anesthetic, phenylephrine infusion, and blood pressure management were all standardized. The primary outcome was postdelivery intraoperative nausea and vomiting using a 4-point scale (0-3). A sample size of 80 patients per group was needed to demonstrate a 50% reduction in intraoperative nausea and vomiting with in situ repair. From November 2015 through July 2018, 180 patients were enrolled. Incidence of postdelivery intraoperative nausea and vomiting was 39% in the exteriorization group compared with 22% in the in situ group (P=.01). Incidence of hypotension (80% vs 50%; P<.001) and tachycardia (33% vs 17%; P=.02) was significantly higher in the exteriorization group, and more phenylephrine boluses were administered to this group (median 4 boluses [first and third quartiles 1.25-7] vs 2 [0-4]; P<.001). The duration of surgery, blood loss, and postoperative hemoglobin decline were similar between groups. In situ uterine repair for elective cesarean delivery under spinal anesthesia with a phenylephrine infusion is associated with less postdelivery intraoperative nausea and vomiting. ClinicalTrials.gov, NCT02587013.

Using Near Infrared Spectroscopy, Diffuse Correlation Spectroscopy, and Intravital Video Microscopy to Monitor the Skeletomuscular and Cerebral Microcirculation

IntroductionThe microcirculation is the primary facilitator of oxygen delivery in tissue, and dysfunction in the microvasculature is often the first indication of a disease state. The microcirculation can be studied using a variety of methods, both invasive and non‐invasive. Two non‐invasive optical methods are near infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS). NIRS is sensitive to changes in tissue hemoglobin concentration and oxygen, while DCS is sensitive to changes in blood flow. However, neither method can directly visualize changes on a capillary by capillary basis. Intravital Video Microscopy (IVVM) allows us to do so, but is an invasive technique that requires surgery to expose the microcirculation. By using IVVM we can compare a direct visualization of the microvasculature to the signal received by NIRS/DCS in an equivalent microvascular bed. In addition, we can compare the NIRS/DCS signal from the skeletal muscle to the signal from the brain, allowing us to simultaneously monitor change in these two organs in response to disease progression or in response to stimulus.MethodsData is collected from Sprague Dawley rats (n=4) using both a dual wavelength Olympus inverted microscope (with 2 Rolera XR cameras and a beam splitter) and an in‐house NIRS/DCS device. Rats are anaesthetized and have their right extensor digitorum longus (EDL) muscle, found in the hind limb, exposed and reflected over the objective. Probes for the NIRS/DCS device are located on the left hind limb and the top of the skull. IVVM is used to collect microvascular velocity, hematocrit, and oxygen saturation from the right EDL, and NIRS/DCS will be used to collect microvascular hematocrit, oxygen saturation, and blood flow data from the left hind limb and the brain. Microvascular blood flow and oxygen saturation data from the left and right hind limbs will be compared, then the NIRS/DCS‐gathered data from the left hind limb will be compared to NIRS/DCS‐gathered data from the brain.DiscussionThis study will be the first to make a direct comparison between NIRS/DCS and IVVM measurements of the microcirculation, and will provide insight into the sensitivity of NIRS/DCS and its ability to accurately monitor the microvasculature. In addition, this study will be the first to make a direct comparison between skeletomuscular and cerebral NIRS/DCS measurements. Future work includes using this approach to determine the differences in effect of a phenylephrine bolus or an inspired oxygen challenge on these two microvascular beds. Further studies will determine whether disease progression occurs on the same timeline in the brain as it does in skeletal muscle.Support or Funding InformationNSERC Discovery Grant to C.G. Ellis.

Testing individual baroreflex responses to hypoxia-induced peripheral chemoreflex stimulation

IntroductionBaroreflexes and peripheral chemoreflexes control efferent autonomic activity making these reflexes treatment targets for arterial hypertension. The literature on their interaction is controversial, with suggestions that their individual and collective influence on blood pressure and heart rate regulation is variable. Therefore, we applied a study design that allows the elucidation of individual baroreflex–chemoreflex interactions.MethodsWe studied nine healthy young men who breathed either normal air (normoxia) or an air–nitrogen–carbon dioxide mixture with decreased oxygen content (hypoxia) for 90 min, with randomization to condition, followed by a 30-min recovery period and then exposure to the other condition for 90 min. Multiple intravenous phenylephrine bolus doses were applied per condition to determine phenylephrine pressor sensitivity as an estimate of baroreflex blood pressure buffering and cardiovagal baroreflex sensitivity (BRS).ResultsHypoxia reduced arterial oxygen saturation from 98.1 ± 0.4 to 81.0 ± 0.4% (p < 0.001), raised heart rate from 62.9 ± 2.1 to 76.0 ± 3.6 bpm (p < 0.001), but did not change systolic blood pressure (p = 0.182). Of the nine subjects, six had significantly lower BRS in hypoxia (p < 0.05), two showed a significantly decreased pressor response, and three showed a significantly increased pressor response to phenylephrine in hypoxia, likely through reduced baroreflex buffering (p < 0.05). On average, hypoxia decreased BRS by 6.4 ± 0.9 ms/mmHg (19.9 ± 2.0 vs. 14.12 ± 1.6 ms/mmHg; p < 0.001) but did not change the phenylephrine pressor response (p = 0.878).ConclusionWe applied an approach to assess individual baroreflex–chemoreflex interactions in human subjects. A subgroup exhibited significant impairments in baroreflex blood pressure buffering and BRS with peripheral chemoreflex activation. The methodology may have utility in elucidating individual pathophysiology and in targeting treatments modulating baroreflex or chemoreflex function.

Clinical comparison of prophylactic phenylephrine infusion vs. bolus regimens on maternal hemodynamics and neonatal outcomes during cesarean section

Background and Objective: Phenylephrine bolus or infusion is used to maintain arterial blood pressure during the subarachnoid block (SAB) for cesarean section. The objective was to assess the clinical efficacy of prophylactic phenylephrine infusion or bolus doses for maternal hemodynamics maintenance and its effect on fetal outcomes. Materials and Methods: Sixty parturients were randomized to receive either a continuous prophylactic IV infusion of phenylephrine (n = 30, group A) at a dose of 0.50 μg.kg−1.min−1 or phenylephrine (n = 30, Group B) 50 μg bolus dose after the systolic blood pressure (SBP) fell by 20% from the baseline. The changes in hemodynamics, ill effects, neonatal APGAR scores, and fetal acidosis were recorded at different time intervals. Results: SBP was significantly higher over time in group A. Group A showed a significant fall in heart rate from baseline after giving SAB and remained significantly low throughout the intraoperative period (P 20% from the baseline; however, hypotension was observed in 21 patients in group B (P 20% of baseline value, were noted in 3 out of 30 patients in the Group A. There was also a statistically nonsignificant trend toward a less frequent incidence of nausea and vomiting in the group A (P

Comparison of Bolus Phenylephrine, Ephedrine and Mephentermine for the Management of Hypotension during Spinal Anaesthesia in Caesarean Section: A Clinical Study

Comparison of Bolus Phenylephrine, Ephedrine and Mephentermine for the Management of Hypotension during Spinal Anaesthesia in Caesarean Section: A Clinical Study

Effect of Phenylephrine and Ephedrine on Cerebral (Tissue) Oxygen Saturation During Carotid Endarterectomy (PEPPER): A Randomized Controlled Trail

Introduction - Adequate blood pressure during carotid endarterectomy (CEA) is essential to preserve cerebral perfusion. To achieve and maintain adequate blood pressure intraoperative, short-acting vasopressor agents like phenylephrine or ephedrine can be used. Previous studies in healthy subjects revealed that besides a systemic hemodynamic effect, these vasopressors also affected frontal lobe cerebral tissue oxygenation (ScO2) showing a decrease after administration of phenylephrine.1,2 This decrease in ScO2 after phenylephrine administration is unwarranted in patients with jeopardized cerebral perfusion, like CEA patients. The aim of this study was to evaluate the impact of both phenylephrine and ephedrine on ScO2 during CEA. Methods - In this double blinded randomized controlled trial 29 patients underwent CEA under general anesthesia for > 70% symptomatic or asymptomatic stenosis. This number of patients matches the number of subjects required according to the power calculation, which suggested 14 patients for each vasopressor study arm.3 Patients were preoperative allocated randomly (1:1) by computer-generated randomization for receiving either phenylephrine or ephedrine in case intraoperative hypotension occurs. During CEA mean arterial pressure (MAP) was measured by radial artery line, placed on the arm with the highest preoperative systolic blood pressure. In case of a decreased MAP ³20% compared to (awake) baseline, patients received a bolus of either phenylephrine (50μg; N=14) or ephedrine (5mg; N=15). After administration the MAP, cardiac output, heart rate, stroke volume and ScO2 were measured. The chosen timeframe for data analysis was 120 seconds before, until 300 seconds after administration. Results - Both phenylephrine (70±9 to 99±22 mmHg; P<0.001; mean±SD) and ephedrine (75±11 mmHg to 109±19 mmHg; P<0.01) adequately restored the MAP. Heart rate did not change significantly after infusion of both vasopressors. However cardiac output was raised after administration of both, 15% and 14% for phenylephrine and ephedrine respectively. ScO2 did not change significantly after administration of either phenylephrine or ephedrine (from 73% to 71% and 72% to 71% respectively). Conclusion - Within this randomized prospective study, we did not observe a different response in ScO2 when MAP was corrected by either phenylephrine or ephedrine in patients who underwent CEA.

Induction techniques that reduce redistribution hypothermia: a prospective, randomized, controlled, single blind effectiveness study

BackgroundWhile much effort has been devoted to correcting intraoperative hypothermia, less attention has been directed to preventing redistribution hypothermia. In this study, we compared three different anesthetic induction techniques to standard IV propofol inductions (control) in their effect on reducing redistribution hypothermia.MethodsElective, afebrile patients, age 18 to 55 years, were randomly assigned to one of four groups (n = 50 each). Group “INH/100” was induced with 8% sevoflurane in 100% oxygen, Group “INH/50” with 8% sevoflurane in 50% oxygen and 50% nitrous oxide, Group “PROP” with 2.2 mg/kg propofol, and Group “Phnl/PROP” with 2.2 mg/kg propofol immediately preceded by 160 mcg phenylephrine. Patients were maintained with sevoflurane in 50% nitrous oxide and 50% oxygen in addition to opioid narcotic. Forced air warming was used. Core temperatures were recorded every 15 min after induction for 1 h.ResultsCompared to control group PROP, the mean temperatures in groups INH/100, INH/50, and Phnl/PROP were higher 15, 30, 45 and 60 min after induction (p < 0.001 for all comparisons), averaging between 0.39 °C and 0.54 °C higher. In group PROP, 60% of patients had at least one temperature below 36.0 °C in the first hour whereas only 16% did in each of groups INH/100, INH/50, and Phnl/PROP (p < 0.0001 in each group compared to PROP).ConclusionsIn this effectiveness trial, inhalation inductions with sevoflurane or with prophylactic phenylephrine bolus prior to propofol induction reduced the magnitude of redistribution hypothermia by an average of 0.4 to 0.5 °C in patients aged 18 to 55 years.Trial registrationRetrospectively registered on clinical-trials.gov as NCT02331108, November 20, 2014.

Variable versus fixed-rate infusion of phenylephrine during cesarean delivery: a randomized controlled trial

BackgroundPhenylephrine is the most commonly used vasopressor for prophylaxis against maternal hypotension during cesarean delivery; however, the best regimen for its administration is not well established. Although variable infusion protocols had been suggested for phenylephrine infusion, evidence-based evaluation of variable infusion regimens are lacking. The aim of this work is to compare variable infusion, fixed on-and-off infusion, and intermittent boluses of phenylephrine for prophylaxis against maternal hypotension during cesarean delivery.MethodsA randomized controlled study was conducted, including full-term pregnant women scheduled for elective cesarean delivery. Participants were divided into three groups which received phenylephrine by either intermittent boluses (1.5 mcg/Kg phenylephrine), fixed on-and-off infusion (with a dose of 0.75 mcg/Kg/min), or variable infusion (with a starting dose of 0.75 mcg/Kg/min). The three groups were compared with regard to frequency of: maternal hypotension (primary outcome), second episode hypotension, reactive hypertension, and bradycardia. Other outcomes included heart rate, systolic blood pressure, physician interventions, and neonatal outcomes.ResultsTwo-hundred and seventeen mothers were available for final analysis. The 2 infusion groups showed less incidence of maternal hypotension {26/70 (37%), 22/71 (31%), and (51/76 (67%)} and higher incidence of reactive hypertension compared to the intermittent boluses group without significant differences between the two former groups. The number of physician interventions was highest in the variable infusion group compared to the other two groups. The intermittent boluses group showed lower systolic blood pressure and higher heart rate compared to the two infusion groups; whilst the two later groups were comparable.ConclusionBoth phenylephrine infusion regimens equally prevented maternal hypotension during cesarean delivery compared to intermittent boluses regimen. Due to higher number of physician interventions in the variable infusion regimen, the current recommendations which favor this regimen over fixed infusion regimen might need re-evaluation.

Dissecting genetic factors affecting phenylephrine infusion rates during anesthesia: a genome-wide association study employing EHR data

BackgroundThe alpha-adrenergic agonist phenylephrine is often used to treat hypotension during anesthesia. In clinical situations, low blood pressure may require prompt intervention by intravenous bolus or infusion. Differences in responsiveness to phenylephrine treatment are commonly observed in clinical practice. Candidate gene studies indicate genetic variants may contribute to this variable response.MethodsPharmacological and physiological data were retrospectively extracted from routine clinical anesthetic records. Response to phenylephrine boluses could not be reliably assessed, so infusion rates were used for analysis. Unsupervised k-means clustering was conducted on clean data containing 4130 patients based on phenylephrine infusion rate and blood pressure parameters, to identify potential phenotypic subtypes. Genome-wide association studies (GWAS) were performed against average infusion rates in two cohorts: phase I (n = 1205) and phase II (n = 329). Top genetic variants identified from the meta-analysis were further examined to see if they could differentiate subgroups identified by k-means clustering.ResultsThree subgroups of patients with different response to phenylephrine were clustered and characterized: resistant (high infusion rate yet low mean systolic blood pressure (SBP)), intermediate (low infusion rate and low SBP), and sensitive (low infusion rate with high SBP). Differences among clusters were tabulated to assess for possible confounding influences. Comorbidity hierarchical clustering showed the resistant group had a higher prevalence of confounding factors than the intermediate and sensitive groups although overall prevalence is below 6%. Three loci with P < 1 × 10−6 were associated with phenylephrine infusion rate. Only rs11572377 with P = 6.09 × 10−7, a 3′UTR variant of EDN2, encoding a secretory vasoconstricting peptide, could significantly differentiate resistant from sensitive groups (P = 0.015 and 0.018 for phase I and phase II) or resistant from pooled sensitive and intermediate groups (P = 0.047 and 0.018).ConclusionsRetrospective analysis of electronic anesthetic records data coupled with the genetic data identified genetic variants contributing to variable sensitivity to phenylephrine infusion during anesthesia. Although the identified top gene, EDN2, has robust biological relevance to vasoconstriction by binding to endothelin type A (ETA) receptors on arterial smooth muscle cells, further functional as well as replication studies are necessary to confirm this association.

Phenylephrine Effectiveness in Handling Hypotensive Issues During Spinal Anesthesia Conductance for Cesarean Section Deliveries

Background: Hypotension is frequent clinical challenge during spinal mode of anesthetic induction for cesarean delivery. Requiring an effective and prompt management mode since it has unfavorable clinical outcomes such as hemodynamic cardiovascular instability issues besides reduced uteroplacental perfusion. Aim: Investigating the impact and effectiveness of different prophylacticdosages of Phenylephrine on hypotensive issues during spinal anesthesia for cesarean section deliveries. Methodology:A prospective, randomized, clinical research study involved 184 cases That are classified as American Society of Anesthesiologists physical status I and II with term singleton pregnancies scheduled for elective cesarean section under spinal anesthesia randomized to receive 0.9% saline 2 mL (Control Group) or phenylephrine1.0 ug/kg (PHE1 research Group), 1.5 ug/kg (PHE1.5 research Group), or 2.0 ug/kg (PHE2 research Group) immediately after induction of spinal anesthesia. Results: The adverse effects of prophylactic bolus ofPhenylephrine among the research groups control, Phenylephrine 1, 1.5,2 in which there was statistically significant difference as regards hypotension, rescue Phenylephrine,lowest SBP,highest SBP,early highest SBP,mean SBP, occurrence of hypertension (p values= &lt;0.001, &lt;0.001, 0.002, &lt;0.001, &lt;0.001, &lt;0.001, &lt;0.001consecutively) there was no statistical significant difference as regards nausea and bradycardia (p values=0.929, 0.823consecutively). Conclusions: The research findings obtained denote and imply that a prophylactic Phenylephrine 1.5 ug/kg bolus followed by additional boluses when necessary could be an alternative management protocol to decrease the frequency of hypotensive issues occurrence during spinal anesthetic mode for cesarean deliveries.

Human Errors and Adverse Hemodynamic Events Related to "Push Dose Pressors" in the Emergency Department.

Though the use of small bolus doses of vasopressors, termed "push dose pressors," has become common in emergency medicine, data examining this practice are scant. Push dose pressors frequently involve bedside dilution, which may result in errors and adverse events. The objective of this study was to assess for instances of human error and adverse hemodynamic events during push dose pressor use in the emergency department. This was a structured chart and video review of all patients age ≥ 16years undergoing resuscitation and receiving push dose pressors from a single center from January 2010 to November 2017. Push dose pressors were defined as intended intravenous boluses of phenylephrine (any dose) or epinephrine (≤ 100mcg). A total of 249 patients were analyzed. Median age was 60years (range, 16-97), 58% were male, 49% survived to discharge. Median initial epinephrine dose was 20mcg (n = 139, IQR 10-100, range 1-100); median phenylephrine dose was 100mcg (n = 110, IQR 100-100, range 25-10,000). Adverse hemodynamic events occurred in 98 patients (39%); 30 in the phenylephrine group (27%; 95% CI, 19-36%), and 68 in the epinephrine group (50%; 95% CI, 41-58%). Human errors were observed in 47 patients (19%), including 7 patients (3%) experiencing dosing errors (all overdoses; range, 2.5- to 100-fold) and 43 patients (17%) with a documentation error. Only one dosing error occurred when a pharmacist was present. Human errors and adverse hemodynamic events were common with the use of push dose pressors in the emergency department. Adverse hemodynamic events were more common than in previous studies. Future research should determine if push dose pressors improve outcomes and if so, how to safely implement them into practice.

Randomized Double-blind Comparison of Bolus Phenylephrine or Ephedrine for Treatment of Hypotension in Women With Preeclampsia Undergoing Caesarean Section

(Anaesthesia. 2018;73:839–846) Preeclampsia is a common complication of pregnancy. In the past, anesthesiologists had sometimes avoided the use of spinal anesthesia in parturients with preeclampsis due to concerns about spinal-induced hypotension leading to inadequate uteroplacental perfusion. However, more recent studies have shown spinal anesthesia to be a safe technique in preeclamptic women as the hypotension associated with it is less severe than that experienced by normotensive parturients and is easily treated. However, effective treatment of postspinal hypotension remains an important component of anesthetic management. While phenylephrine has become the vasopressor of choice for treatment of hypotension in healthy women undergoing cesarean section due to the lower risk of fetal acidosis, the preferred vasopressor for preeclamptic women remains unclear. This randomized, double blind study was performed to compare the effects of phenylephrine versus ephedrine for the treatment of spinal-induced hypotension in preeclamptic women undergoing cesarean section.