Effects of continuous infusion of phenylephrine vs. norepinephrine on parturients and fetuses under LiDCOrapid monitoring: a randomized, double-blind, placebo-controlled study

Preventing Spinal-induced Hypotension During Elective Cesarean Sections

PURPOSE

The purpose of this quality improvement project was to implement an evidence-based intraoperative protocol to reduce the incidence of spinal-induced hypotension during elective cesarean sections.

DESIGN

A quality improvement project.

METHODS

After receiving education, anesthesia providers implemented the intraoperative protocol for 6 weeks on elective cesarean sections. Intraoperative anesthesia records were retrospectively reviewed and evaluated preimplementation and postimplementation to determine the impact of the project on the incidence of spinal-induced hypotension.

FINDINGS

The final sample included 134 patient charts (64 preimplementation and 72 postimplementation). The incidence of hypotension 10 minutes after spinal placement was not significantly different before (n = 9) or after implementation (n = 13; χ2 = 0.4, P = .554). After project implementation, the rate of hypotension was 22% (n = 13) in patients not treated per the protocol and 0% (n = 0, χ2 = 3.5, P = .062) in patients treated per the protocol. There was a 39.4% (P < .001) reduction in the need for rescue doses of phenylephrine and a 27.8% (P = .001) reduction in the need for rescue doses of ephedrine after protocol implementation.

CONCLUSIONS

Hypotension was not significantly decreased for all patients after project implementation but was eliminated for patients in whom the protocol was used. Provider utilization of the intraoperative protocol was only 18%. It is recommended to pursue additional interventions to increase protocol utilization, accessibility of protocol components, and staff training. Future studies can investigate the impact of this protocol on maternal nausea and vomiting incidence during elective cesarean sections.

Optimal Infusion Rate of Norepinephrine for Prevention of Spinal Hypotension for Cesarean Delivery: A Randomized Controlled Trial, Using Up-Down Sequential Allocation

BACKGROUND

Norepinephrine has recently been suggested to be as effective as phenylephrine for the prevention of hypotension after spinal anesthesia for cesarean delivery. Moreover, compared to phenylephrine, norepinephrine may be superior in maintaining heart rate (HR) and consequently, cardiac output (CO). A recent study demonstrated that norepinephrine given as a single intravenous bolus is approximately 13 times more potent than phenylephrine. However, it is uncertain whether this finding can be applied when these vasopressors are administered as infusions. Therefore, the optimum infusion rate of norepinephrine remains unknown. We aimed to determine the median effective dose (ED50; defined as the rate of vasopressor infusion required to prevent spinal hypotension in 50% of subjects) of both drugs needed to maintain maternal systolic blood pressure within 20% of the baseline after spinal anesthesia for cesarean delivery and to derive the relative potency ratio.

METHODS

Sixty healthy patients undergoing elective cesarean delivery with standardized spinal anesthesia were randomized into 2 groups. The first patient in group 1 received phenylephrine 1200 µg in normal saline 0.9% w/v 60 mL at 60 mL/h infusion rate (20 µg.min-1). The first patient in group 2 received norepinephrine 96 µg in normal saline 0.9% w/v 60 mL at 60 mL/h infusion rate (1.6 µg.min-1). Using up-down sequential allocation technique, the vasopressor dose for every subsequent patient was determined by the response in the previous patient. If effective, the next patient received a dose reduced by 150 µg of phenylephrine (2.5 µg.min-1) or 12 µg (0.2 µg.min-1) of norepinephrine. If ineffective, the dose for the next patient was increased by the same amount. The ED50s were determined according to the Dixon-Massey formula. Stroke volume (SV), HR, and CO were also measured.

RESULTS

The ED50 was 12.7 µg.min-1 (95% CI, 10.5-14.9) for phenylephrine and 1.01 µg.min-1 (95% CI, 0.84-1.18) for norepinephrine, giving a potency ratio of 12.6 (95% CI, 9.92-15.9). HR, SV, and CO did not differ between the groups.

CONCLUSIONS

Norepinephrine is more potent than phenylephrine by a factor of approximately 13 when administered as infusion for equivalent maternal blood pressure control. Based on these findings, we recommend a variable rate prophylactic infusion of norepinephrine to be initiated at 1.9 to 3.8 µg.min-1 for the management of hypotension during cesarean delivery under spinal anesthesia.

Perioperative hypotension and use of vasoactive agents in non-cardiac surgery: A scoping review

BACKGROUND

Perioperative hypotension is common and associated with adverse patient outcomes. Vasoactive agents are often used to manage hypotension, but the ideal drug, dose and duration of treatment has not been established. With this scoping review, we aim to provide an overview of the current body of evidence regarding the vasoactive agents used to treat perioperative hypotension in non-cardiac surgery.

METHODS

We included all studies describing the use of vasoactive agents for the treatment of perioperative hypotension in non-cardiac surgery. We excluded literature reviews, case studies, and studies on animals and healthy subjects. We posed the following research questions: (1) in which surgical populations have vasoactive agents been studied? (2) which agents have been studied? (3) what doses have been assessed? (4) what is the duration of treatment? and (5) which desirable and undesirable outcomes have been assessed?

RESULTS

We included 124 studies representing 10 surgical specialties. Eighteen different agents were evaluated, predominantly phenylephrine, ephedrine, and noradrenaline. The agents were administered through six different routes, and numerous comparisons between agents, dosages and routes were included. Then, 88 distinct outcome measures were assessed, of which 54 were judged to be non-patient-centred.

CONCLUSIONS

We found that studies concerning vasoactive agents for the treatment of perioperative hypotension varied considerably in all aspects. Populations were heterogeneous, interventions and exposures included multiple agents compared against themselves, each other, fluids or placebo, and studies reported primarily non-patient-centred outcomes.

Association Between Intraoperative Noradrenaline Infusion and Outcomes in Older Adult Patients Undergoing Major Non-Cardiac Surgeries: A Retrospective Propensity Score-Matched Cohort Study

Background

Noradrenaline (NA) is commonly used intraoperatively to prevent fluid overload and maintain hemodynamic stability. Clinical studies provided inconsistent results concerning the effect of NA on postoperative outcomes. As aging is accompanied with various diseases and has the high possibility of the risk for postoperative complications, we hypothesized that intraoperative NA infusion in older adult patients undergoing major non-cardiac surgeries might potentially exert adverse outcomes.

Methods

In this retrospective propensity score-matched cohort study, older adult patients undergoing major non-cardiac surgeries were selected, 1837 receiving NA infusion during surgery, and 1072 not receiving NA. The propensity score matching was conducted with a 1:1 ratio and 1072 patients were included in each group. The primary outcomes were postoperative in-hospital mortality and complications.

Results

Intraoperative NA administration reduced postoperative urinary tract infection (OR:0.124, 95% CI:0.016-0.995), and had no effect on other postoperative complications and mortality, it reduced intraoperative crystalloid infusion (OR:0.999, 95% CI:0.999-0.999), blood loss (OR: 0.998, 95% CI: 0.998-0.999), transfusion (OR:0.327, 95% CI: 0.218-0.490), but increased intraoperative lactate production (OR:1.354, 95% CI:1.051-1.744), and hospital stay (OR:1.019, 95% CI:1.008-1.029).

Conclusion

Intraoperative noradrenaline administration reduces postoperative urinary tract infection, and does not increase other postoperative complications and mortality, and can be safely used in older adult patients undergoing major non-cardiac surgeries.

Manually Controlled, Continuous Infusion of Phenylephrine or Norepinephrine for Maintenance of Blood Pressure and Cardiac Output During Spinal Anesthesia for Cesarean Delivery: A Double-Blinded Randomized Study

BACKGROUND

To counteract the vasoplegia induced by spinal anesthesia (SA) and maintain blood pressure (BP) during cesarean delivery, phenylephrine is currently recommended, but norepinephrine might offer superior preservation of cardiac output. We aimed to compare the hemodynamic effects of phenylephrine and norepinephrine administered by manually adjusted continuous infusion during elective cesarean delivery.

METHODS

In this pragmatic, parallel-group, double-blind randomized controlled trial, 124 parturients scheduled for elective cesarean delivery under SA in a tertiary maternity in France, between February 2019 and December 2020, were randomized to receive norepinephrine at a starting rate of 0.05 μg·kg -1 ·min -1 (n = 62) or phenylephrine at a starting rate of 0.5 μg·kg -1 ·min -1 (n = 62). In both groups, the vasopressor infusion rate was then manually adjusted to maintain maternal systolic BP above 90% of the baseline value. The primary outcome, the change in cardiac index (CI) measured by thoracic bioreactance from SA to umbilical cord clamping, was analyzed through repeated measures analysis of variance and post hoc t tests. Secondary outcomes included maternal BP and neonatal outcomes.

RESULTS

In the norepinephrine group, cardiac index was maintained between 90% and 100% of baseline from SA to umbilical cord clamping, whereas it was maintained at significantly lower values (81%-88%) in the phenylephrine group ( P = .001). The percentage of elapsed time with a mean maternal BP <65 mm Hg and with systolic BP <80% of the baseline value was higher in the phenylephrine group: 2.9% (7.3) vs 0.5% (1.8) (absolute risk difference [ARD], -2.4%; 95% confidence interval, -4.4 to -0.5; P = .012) and 8.5% (16.6) vs 2.3% (5.2) (ARD, -6.2%; 95% confidence interval, -10.6 to -1.8; P = .006). Excluding parturients with gestational diabetes, severe neonatal hypoglycemia was more common in the phenylephrine group at 19.6% (9/46) vs 4.1% (2/49) ( P = .02). The other neonatal outcomes did not differ significantly between the groups.

CONCLUSIONS

When administered by manually adjusted infusion during SA for cesarean delivery, norepinephrine was associated with a higher CI; both infusions were effective for maintaining BP.