Intra‐operative assessment of pulmonary artery pressure by transoesophageal echocardiography

The clinical value of the estimation of systolic pulmonary artery pressure, based on Doppler assessment of peak tricuspid regurgitant velocity using transoesophageal echocardiography, is unclear. We studied 109 patients to evaluate the feasibility of obtaining adequate Doppler recordings, and compared Doppler estimates with values measured using a pulmonary artery catheter in a subset of 33 patients. Tricuspid regurgitation was evaluated at the mid‐oesophageal level at 0–120° using Doppler echocardiography. A Doppler signal was defined as adequate if there was a ≤ 20° alignment and a full envelope. Doppler estimates of systolic pulmonary artery pressure within 10 mmHg and 15% of the value recorded with the pulmonary artery catheter were considered to be in sufficient agreement. Adequate Doppler signals were obtained in 64/109 (59%) patients before and 54/103 (52%) after surgery. Doppler estimates by transoesophageal echocardiography were within 10 mmHg and 15% of values recorded with the pulmonary artery catheter in 28/33 (75%) patients and 22/31 (55%) patients, respectively. In 7 (21%) patients, the echocardiographic Doppler measurement exceeded the measured systolic pulmonary artery pressure by more than 30%. Our study indicates that estimation of the systolic pulmonary artery pressure using transoesophageal Doppler echocardiography is not a reliable and clinically useful method in anaesthetised patients undergoing mechanical ventilation.     

Continuous assessment of right ventricular ejection fraction: new pulmonary artery catheter versus transoesophageal echocardiography

In 25 cardiac surgical patients, right ventricular ejection fraction was continuously measured with a new pulmonary artery catheter and transoesophageal echocardiography, scanning the 'fractional area change' in a standardised transatrial cross section area. Measurements were recorded at three predefined time points (pre-, intra-, and postoperatively). Both methods were compared using the Bland-Altman analysis. Comparing right ventricular ejection fraction values obtained from the pulmonary artery catheter with those assessed by transoesophageal echocardiography, bias was -3.7%, with a precision of 30.9%. Bias and precision significantly improved when the heart rate was less than 100 beats.min(-1), pulmonary artery pressures were low and cardiac performance adequate. In conclusion, the new continuous pulmonary artery catheter system appears to be a valid and useful bedside monitoring device in the haemodynamic management of critically ill patients.     

Assessment of an updated double‐vasopressor automated system using Nexfin™ for the maintenance of haemodynamic stability to improve peri‐operative outcome during spinal anaesthesia for caesarean section

Hypotension occurs commonly during spinal anaesthesia for caesarean section, associated with maternal and fetal adverse effects. We developed a double‐vasopressor automated system with a two‐step algorithm and continuous non‐invasive haemodynamic monitoring using the Nexfin^? device. The system delivered 25 μg phenylephrine every 30 s when systolic blood pressure was between 90% and 100% of baseline, or 2 mg ephedrine at this blood pressure range and heart rate < 60 beats.min^?1; and 50 μg phenylephrine or 4 mg ephedrine when systolic blood pressure was < 90% of baseline with the same heart rate criterion. Fifty‐seven women received standardised spinal anaesthesia. Twenty‐seven (47.4%) had at least one reading of hypotension defined as systolic blood pressure < 80% baseline. Systolic blood pressure was within 20% of the baseline in a mean (SD) of 79.8 (20.9)% of measurements. Fifty‐three (93.0%) women required phenylephrine before delivery while 10 (17.5%) required ephedrine. Six women (10.5%) experienced nausea and three (5.3%) vomited. The system was able to achieve a low incidence of maternal hypotension with good maternal and fetal outcomes.     

The utility of transoesophageal echocardiography for estimating right ventricular systolic pressure

With the reduction in use of the pulmonary artery catheter, alternative methods of pulmonary pressure estimation are required. The use of echocardiographically‐derived right ventricular systolic pressure has recently been questioned, but this technique has not been validated in anaesthetised surgical patients with transoesophageal echocardiography. One hundred measurements of right ventricular systolic pressure with transoesophageal echocardiography were compared with the pulmonary artery systolic pressure obtained simultaneously from a pulmonary artery catheter in patients undergoing cardiac surgery. Simultaneous right ventricular systolic pressure and pulmonary artery systolic pressure measurements were possible in all patients, and these measurements were strongly correlated (r = 0.98, p < 0.001), with minimal bias and narrow limits of agreement (approximately ?5 to +5 mmHg), across a broad range of pulmonary pressures. Measurement of right ventricular systolic pressure using tranoesophageal echocardiography is readily achievable and closely correlates with pulmonary artery systolic pressure, with minimal bias, in cardiac surgical patients undergoing general anaesthesia and positive pressure mechanical ventilation of the lungs.     

Non-invasive prediction of fluid responsiveness during major hepatic surgery

Background. The aim of this study was to evaluate potentialpredictors of fluid responsiveness obtained during major hepaticsurgery. The predictors studied were invasive monitoring ofintravascular pressures (radial and pulmonary artery catheter),including direct measurement of respiratory variation in arterialpulse pressure (PPVart), transoesophageal echocardiography (TOE),and non-invasive estimates of PPVart from the infrared photoplethysmographywaveform from the Finapres^® (PPVfina) and the pulse oximetrywaveform (PPVsat). Methods. We conducted a prospective study of 54 fluid challenges(250 ml colloid) given for haemodynamic instability in eightpatients undergoing hepatic resection. Fluid responsivenesswas defined as an increase in stroke volume index (SVI)     

Maternal cardiac output response to colloid preload and vasopressor therapy during spinal anaesthesia for caesarean section in patients with severe pre‐eclampsia: a randomised,controlled trial

We examined the haemodynamic effects of colloid preload, and phenylephrine and ephedrine administered for spinal hypotension, during caesarean section in 42 women with severe early onset pre‐eclampsia. Twenty patients with pre‐delivery spinal hypotension were randomly allocated to receive an initial dose of either 50 μg phenylephrine or 7.5 mg ephedrine; the primary outcome was percentage change in cardiac index. After a 300‐ml colloid preload, mean (SD) cardiac index increased from 4.9 (1.1) to 5.6 (1.2) l.min^?1.m^?2 (p < 0.01), resulting from an increase in both heart rate, from 81.3 (17.2) to 86.3 (16.5) beats.min^?1 (p = 0.2), and stroke volume, from 111.8 (19.0) to 119.8 (17.9) ml (p = 0.049). Fourteen (33%) and 23 (54.8%) patients exhibited a stroke volume response > 10% and > 5%, respectively; a significant negative correlation was found between heart rate and stroke volume changes. Spinal hypotension in 20 patients was associated with an increase from baseline in cardiac index of 0.6 l.min^?1.m^?2 (mean difference 11.5%; p < 0.0001). After a median [range] dose of 50 [50–150] μg phenylephrine or 15 [7.5–37.5] mg ephedrine, the percentage change in cardiac index during the measurement period of 150 s was greater, and negative, in patients receiving phenylephrine vs. ephedrine, at ?12.0 (7.3)% vs. 2.6 (6.0)%, respectively (p = 0.0001). The percentage change in heart rate after vasopressor was higher in patients receiving phenylephrine, at ?9.1 (3.4)% vs. 5.3 (12.6)% (p = 0.0027), as was the change in systemic vascular resistance, at 22.3 (7.5) vs. ?1.9 (10.5)% (p < 0.0001). Phenylephrine effectively reverses spinal anaesthesia‐induced haemodynamic changes in severe pre‐eclampsia, if left ventricular systolic function is preserved.     

The influence of transoesophageal echocardiography on intra-operative decision makingA European multicentre study

The role of transoesophageal echocardiography (TOE) in anaesthesia remains controversial because it is a rapidly evolving technique with few proven benefits and considerable cost. Recently, the Society of Cardiovascular Anaesthesiologists has published practice guidelines for the use of peri-operative TOE. To determine the current role of transoesophageal echocardiography and the relative impact of category-based transoesophageal echocardiographic indications the present study investigated its use in seven Western European countries. The study sample was taken from a prospective cohort of 224 patients with acute or chronic haemodynamic disturbances or at risk of myocardial ischaemia. All patients were monitored with two-lead electrocardiography and radial and pulmonary artery catheters, as well as biplane or multiplane transoesophageal echocardiography. A total of 2232 clinical interventions were made in these patients. The most frequently observed intervention was the administration of a fluid bolus (45% of all interventions). Overall, transoesophageal echocardiography was the most important guiding factor in 560 (25%) interventions. It was the most important monitor in guiding the following therapeutic interventions: anti-ischaemic therapy — 207 of 372 interventions (56%); fluid administration — 275 of 996 (28%) interventions; vasopressor or inotrope administration — 56 of 316 (16%) interventions; vasodilator therapy — six of 142 (4%) interventions and depth of anaesthesia — four of 211 (2%) interventions. We found that transoesophageal echocardiography is frequently influential in guiding clinical decision making and is used most frequently for category II indications but category I indications were associated with more frequent change in management.     

Simulation‐based teaching versus point‐of‐care teaching for identification of basic transoesophageal echocardiography views: a prospective randomised study

In recent years, the use of transoesophageal echocardiography has increased in anaesthesia and intensive care. We explored the impact of two different teaching methods on the ability of echocardiography‐naïve subjects to identify cardiac anatomy associated with the 20 standard transoesophageal echocardiography imaging planes, and assessed trainees' satisfaction with these methods of training. Fifty‐two subjects were randomly assigned to one of two groups: a simulation‐based and a theatre‐based teaching group. Subjects undertook video‐based tests comprised of 20 multiple choice questions on echocardiography views before and after receiving echocardiography teaching. Subjects in simulation‐ and theatre‐based teaching groups scored 40% (30–40 [20–50])% and 35% (30–40 [15–55])% in the pre‐test, respectively (p = 0.52). Following echocardiography teaching, subjects within both groups improved upon their pre‐test knowledge (p < 0.001). Subjects in the simulation‐based teaching group significantly outperformed their theatre‐based group counterparts in the post‐intervention test (p = 0.0002).     

The accuracy of transoesophageal echocardiography in estimating pulmonary capillary wedge pressure in anaesthetised patients

The objective of this study was to identify whether pulmonary capillary wedge pressure can be estimated in anaesthetised patients receiving mechanical ventilation, using transoesophageal echocardiography. A retrospective validation study investigated a 10-patient cohort with variable haemodynamic conditions, and a 102-patient series in which a single measurement was made during stable haemodynamic conditions. Concurrent echocardiographic Doppler and pulmonary artery catheter wedge pressure measurements were performed. In the 10-patient cohort, the systolic fraction of Doppler measurements in the pulmonary vein (r = -0.32, p = 0.035) and the E/A ratio (r = 0.56, p = 0.0009) were correlated with the wedge pressure. In all cases, the limits of agreement exceeded 10 mmHg, and sensitivity or specificity for detecting wedge pressure ≥ 15 mmHg was poor. This study demonstrates proof of concept that using transoesophageal echocardiography for estimating the pulmonary artery wedge pressure may not be sufficiently accurate for clinical use.     

Randomised double‐blind comparison of bolus phenylephrine or ephedrine for treatment of hypotension in women with pre‐eclampsia undergoing caesarean section

Treatment of post‐spinal hypotension during caesarean section assumes special concern in pre‐eclamptic patients due to a compromised fetoplacental circulation and increased risk of placental hypoperfusion. Phenylephrine and ephedrine are the most commonly used vasopressors, although the best choice is still not clear. We studied 80 pre‐eclamptic women with a singleton pregnancy who underwent caesarean section with spinal anaesthesia, and who developed hypotension defined as a decrease in systolic arterial pressure ≥ 20% from baseline or absolute value < 100 mmHg. Women were randomly allocated to receive phenylephrine 50 μg or ephedrine 4 mg boluses for treatment of hypotension. Blood pressure changes following vasopressor administration were similar in both groups, but heart rate remained higher after ephedrine at all time‐points. The primary outcome measure of umbilical artery pH was 7.26 (0.11) in the phenylephrine group and 7.25 (0.09) in the ephedrine group (p = 0.86). The incidence of neonatal acidosis (umbilical artery pH < 7.20) was 9 (22.5%) in the phenylephrine group and 11 (27.5%) in the ephedrine group (p = 0.80). Other secondary outcome measures were comparable. In conclusion, phenylephrine 50 μg and ephedrine 4 mg, administered as intravenous boluses to treat post‐spinal hypotension during caesarean section in pre‐eclamptic patients, resulted in similar fetal acid‐base values, were equally effective in treating hypotension and were associated with good maternal and neonatal outcome.     

Evaluation of TAPSE as a measure of right ventricular output

Purpose

This study was designed to show the relationship between tricuspid annular plane systolic excursion (TAPSE) and stroke volume (SV) by thermodilution using three different methods and also to assess whether TAPSE can track hemodynamic changes associated with volume loading and ephedrine administration.

Methods

This was an observational study in 61 elective patients with a pulmonary artery catheter who were undergoing coronary artery bypass graft surgery in a cardiac surgical centre. We measured TAPSE by three methods using transesophageal echocardiography: M mode, speckle tracking at the lateral wall, and tissue tracking at the inferior wall. There were two interventions: leg raising (volume recruitment) or administration of ephedrine 5?mg iv. Echo and hemodynamic measurements were performed before and after each intervention.

Results

Eleven patients were excluded due to poor imaging. There were 26 patients in the leg raising group and 24 patients in the ephedrine group. The correlation coefficient between stroke volume (SV) and TAPSE by M mode, speckle tracking, and tissue tracking was 0.48, 0.44, and 0.09, respectively. There was a significant increase in SV following each intervention; however, the changes in TAPSE by any method and velocity were not large enough to reach statistical significance.

Conclusion

Tricuspid annular plane systolic excursion by M mode and by speckle tracking correlates modestly with SV. There was no correlation between TAPSE and SV by tissue tracking at the inferior wall of the right ventricle. Tricuspid annular plane systolic excursion by M mode and by speckle tracking does not track changes in SV following either volume loading or ephedrine administration.     

Transoesophageal echocardiography: a useful tool to diagnose entrapment of pulmonary artery catheter

Placement of a pulmonary artery catheter during cardiac surgery is associated with various complications, one of which is entrapment. On the day following surgery unusual resistance was encountered while attempting to remove a pulmonary artery catheter from a patient who had undergone coronary artery bypass grafting. Entrapment of the catheter was confirmed by transoesophageal echocardiography, which demonstrated invagination of the free wall of the pulmonary trunk on gentle traction on the pulmonary artery catheter. Surgical exploration revealed that the catheter was transfixed by the suture used to close the pulmonary artery vent site. Surgical re-exploration and other potential complications related to catheter retrieval can be avoided if catheter entrapment is diagnosed intra-operatively. We suggest that a high index of clinical suspicion along with the use of intra-operative transoesophageal echocardiography is considered in situations where catheter entrapment is a possibility.     

A prospective observational study of stroke volume responsiveness to a passive leg raise manoeuvre in healthy non‐starved volunteers as assessed by transthoracic echocardiography

Current guidelines for intra‐operative fluid management recommend the use of increments in stroke volume following intravenous fluid bolus administration as a guide to subsequent fluid therapy. To study the physiological premise of this paradigm, we tested the hypothesis that healthy, non‐starved volunteers would develop an increment in their stroke volume following a passive leg raise manoeuvre. Subjects were positioned supine and stroke volume was measured by transthoracic echocardiography at baseline, 30 s, 1 min, 3 min and 5 min after passive leg raise manoeuvre to 45 ° . Stroke volume was measured at end‐expiration during quiet breathing, as the mean of three sequential measurements. Seventeen healthy volunteers were recruited; one volunteer in whom it was not possible to obtain Doppler measurements and a further five for reasons of poor Doppler image quality were not included in the study. Mean (SD) percentage difference from baseline to the largest change in stroke volume was 5.7 (9.6)% (p = 0.16). Of the 11 volunteers evaluated, five (45%) had stroke volume increases of greater than 10%. Mean (SD) maximum percentage change in cardiac index was 14.8 (9.7)% (p = 0.004). A wide variation in baseline stroke volume and response to the passive leg raise manoeuvre was seen, suggesting greater heterogeneity in the normal population than current clinical guidelines recognise.     

The impact of internet and simulation‐based training on transoesophageal echocardiography learning in anaesthetic trainees: a prospective randomised study

With the increasing role of transoesophageal echocardiography in clinical fields other than cardiac surgery, we decided to assess the efficacy of multi‐modular echocardiography learning in echo‐naïve anaesthetic trainees. Twenty‐eight trainees undertook a pre‐test to ascertain basic echocardiography knowledge, following which the study subjects were randomly assigned to two groups: learning via traditional methods such as review of guidelines and other literature (non‐internet group); and learning via an internet‐based echocardiography resource (internet group). After this, subjects in both groups underwent simulation‐based echocardiography training. More tests were then conducted after a review of the respective educational resources and simulation sessions. Mean (SD) scores of subjects in the non‐internet group were 28 (10)%, 44 (10)% and 63 (5)% in the pre‐test, post‐intervention test and post‐simulation test, respectively, whereas those in the internet group scored 29 (8)%, 59 (10)%, (p = 0.001) and 72 (8)%, p = 0.005, respectively. The use of internet‐ and simulation‐based learning methods led to a significant improvement in knowledge of transoesophageal echocardiography by anaesthetic trainees. The impact of simulation‐based training was greater in the group who did not use the internet‐based resource. We conclude that internet‐ and simulation‐based learning methods both improve transoesophageal echocardiography knowledge in echo‐naïve anaesthetic trainees.     

Non‐invasive continuous arterial pressure and pulse pressure variation measured with Nexfin® in patients following major upper abdominal surgery: a comparative study

We compared the accuracy and precision of the non‐invasive Nexfin^® device for determining systolic, diastolic, mean arterial pressure and pulse pressure variation, with arterial blood pressure values measured from a radial artery catheter in 19 patients following upper abdominal surgery. Measurements were taken at baseline and following fluid loading. Pooled data results of the arterial blood pressures showed no difference between the two measurement modalities. Bland–Altman analysis of pulse pressure variation showed significant differences between values obtained from the radial artery catheter and Nexfin finger cuff technology (mean (SD) 1.49 (2.09)%, p < 0.001, coefficient of variation 24%, limits of agreement ?2.71% to 5.69%). The effect of volume expansion on pulse pressure variation was identical between methods (concordance correlation coefficient 0.848). We consider the Nexfin monitor system to be acceptable for use in patients after major upper abdominal surgery without major cardiovascular compromise or haemodynamic support.     

Physiological controversies and methods used to determine fluid responsiveness: a qualitative systematic review

Accurate assessment of intravascular fluid status and measurement of fluid responsiveness have become increasingly important in peri‐operative medicine and critical care. The objectives of this systematic review and narrative synthesis were to discuss current controversies surrounding fluid responsiveness and describe the merits and limitations of the major cardiac output monitors in clinical use today in terms of usefulness in measuring fluid responsiveness. We searched the MEDLINE and EMBASE databases (2002–2015); inclusion criteria included comparison with an established reference standard such as pulmonary artery catheter, transthoracic echocardiography and transoesophageal echocardiography. Examples of clinical measures include static (such as central venous pressure) and dynamic (such as stroke volume variation and pulse pressure variation) parameters. The static parameters measured were described as having little value; however, the dynamic parameters were shown to be good physiological determinants of fluid responsiveness. Due to heterogeneity of the methods and patient characteristics, we did not perform a meta‐analysis. In most studies, precision and limits of agreement (bias ±1.96SD) between determinants of fluid responsiveness measured by different devices were not evaluated, and the definition of fluid responsiveness varied across studies. Future research should focus on the physiological principles that underlie the measurement of fluid responsiveness and the effect of different volume expansion strategies on outcomes.     

Closed‐loop double‐vasopressor automated system vs manual bolus vasopressor to treat hypotension during spinal anaesthesia for caesarean section: a randomised controlled trial

Hypotension necessitating vasopressor administration occurs commonly during caesarean section under spinal anaesthesia. We developed a novel vasopressor delivery system that automatically administers phenylephrine or ephedrine based on continuous non‐invasive arterial pressure monitoring. A phenylephrine bolus of 50 μg was given at 30‐s intervals when systolic blood pressure fell < 90% of baseline; an ephedrine bolus of 4 mg was given instead if systolic pressure fell < 90% of baseline together with a heart rate < 60 beats.min^?1. The control group used manual boluses of either phenylephrine 100 μg or ephedrine 8 mg, administered at 1‐min intervals based on the same thresholds for systolic pressure and heart rate. This randomised, controlled, double‐blinded trial involved 213 healthy women who underwent elective caesarean delivery under spinal anaesthesia using 11 mg hyperbaric bupivacaine with 15 μg fentanyl and 100 μg morphine. The automated vasopressor group had better systolic pressure control, with 37/106 (34.9%) having any beat‐to‐beat systolic pressure reading < 80% of baseline compared with 63/107 (58.9%) in the control group (p < 0.001). There was no difference in the incidence of reactive hypertension, defined as systolic pressure > 120% of baseline, with 8/106 (7.5%) in the automated vasopressor group vs 14/107 (13.1%) in the control group, or total dose of vasopressors. The automated vasopressor group had lower median absolute performance error of 8.5% vs control of 9.8% (p = 0.013), and reduced incidence of nausea (1/106 (0.9%) vs 11/107 (10.3%), p = 0.005). Neonatal umbilical cord pH, umbilical lactate and Apgar scores were similar. Hence, our system afforded better control of maternal blood pressure and reduced nausea with no increase in reactive hypertension when compared with manual boluses.     

Randomized trial of bolus phenylephrine or ephedrine for maintenance of arterial pressure during spinal anaesthesia for Caesarean section

Thirty-eight healthy women undergoing elective Caesarean section under spinal anaesthesia at term were allocated randomly to receive boluses of either phenylephrine 100 micrograms or ephedrine 5 mg for maintenance of maternal arterial pressure. The indication for administration of vasopressor was a reduction in systolic pressure to < or = 90% of baseline values. Maternal arterial pressure (BP) and heart rate (HR) were measured every minute by automated oscillometry. Cardiac output (CO) was measured by cross-sectional and Doppler echocardiography before and after preloading with 1500 ml Ringer lactate solution and then every 2 min after administration of bupivacaine. Umbilical artery pulsatility index (PI) was measured using Doppler before and after spinal anaesthesia. The median (range) number of boluses of phenylephrine and ephedrine was similar; 6 (1-10) vs 4 (1- 8) respectively. Maternal systolic BP and CO changes were similar in both groups, but the mean [95% CI] maximum percentage change in maternal HR was larger in the phenylephrine group (-28.5 [-24.2, - 32.9]%) than in the ephedrine group (-14.4 [-10.6, -18.2]%). As a consequence atropine was required in 11/19 women in the phenylephrine group compared with 2/19 in the ephedrine group (P < 0.01). Mean umbilical artery pH [95% CI] was higher in the phenylephrine group (7.29 [7.28-7.30]) than in the ephedrine group (7.27 [7.25-7.28]). The results of the present study support the use of phenylephrine for maintenance of maternal arterial pressure during spinal anaesthesia for elective Caesarean section.      

Volumetric preload measurement by thermodilution: a comparison with transoesophageal echocardiography

Background. End-diastolic volume indices determined by transpulmonarythermodilution and pulmonary artery thermodilution may givea better estimate of left ventricular preload than pulmonarycapillary wedge pressure monitoring. The aim of this study wasto compare volume preload monitoring using the two differentthermodilution techniques with left ventricular preload assessmentby transoesophageal echocardiography (TOE). Methods. Twenty patients undergoing elective cardiac surgerywith preserved left–right ventricular function were studiedafter induction of anaesthesia. Conventional haemodynamic variables,global end-diastolic volume index using the pulse contour cardiacoutput (PiCCO) system (GEDVI_PiCCO), continuous end-diastolicvolume index (CEDVI_PAC) measured by a modified pulmonary arterycatheter (PAC), left ventricular end-diastolic area index (LVEDAI)using TOE and stroke volume indices (SVI) were recorded beforeand 20 and 40 min after fluid replacement therapy. Analysisof variance (Bonferroni–Dunn), Bland–Altman analysisand linear regression were performed. Results. GEDVI_PiCCO, CEDVI_PAC, LVEDAI and SVI_PiCCO/PAC increasedsignificantly after fluid load (P<0.05). An increase >10%for GEDVI_PiCCO and LVEDAI was observed in 85% and 90% of thepatients compared with 45% for CEDVI_PAC. Mean bias (2 SD) betweenpercentage changes (     

An open-label randomized controlled clinical trial for comparison of continuous phenylephrine versus norepinephrine infusion in prevention of spinal hypotension during cesarean delivery

BackgroundDuring spinal anesthesia for cesarean delivery phenylephrine is the vasopressor of choice but can cause bradycardia. Norepinephrine has both β- and α-adrenergic activity suitable for maintaining blood pressure with less bradycardia. We hypothesized that norepinephrine would be superior to phenylephrine, requiring fewer rescue bolus interventions to maintain blood pressure.MethodsEighty-five parturients having spinal anesthesia for elective cesarean delivery were randomized to Group P (phenylephrine 0.1 μg/kg/min) or Group N (norepinephrine 0.05 μg/kg/min) fixed-rate infusions. Rescue bolus interventions of phenylephrine 100 μg for hypotension, or ephedrine 5 mg for bradycardia with hypotension, were given as required to maintain systolic blood pressure. Maternal hemodynamic variables were measured non-invasively.ResultsThere was no difference between groups in the proportion of patients who required rescue vasopressor boluses (Group P: 65.8% [n=25] vs. Group N: 48.8% [n=21], P=0.12). The proportion of patients who received ⩾1 bolus of phenylephrine was similar between groups (Group P: 52.6% [n=20] vs. Group N: 46.5% [n=20], P=0.58). However, more patients received ⩾1 bolus of ephedrine in the phenylephrine group (Group P: 23.7% [n=9] vs. Group N: 2.3% [n=1], P <0.01). The incidence of emesis was greater in the phenylephrine group (Group P: 26.3% vs. Group P: 16.3%, P <0.001). Hemodynamic parameters including heart rate, the incidence of bradycardia, blood pressure, cardiac output, cardiac index, stroke volume, and systemic vascular resistance and neonatal outcome were similar between groups (all P <0.05).ConclusionNorepinephrine fixed-rate infusion has efficacy for preventing hypotension and can be considered as an alternative to phenylephrine.