A Prospective Comparison of Vasopressor Requirement and Hemodynamic Changes During Spinal Anesthesia for Cesarean Delivery in Patients with Multiple Gestation Versus Singleton Pregnancy

MRI of caval compression during left-lateral tilt in singleton and twin pregnancies: A prospective cohort study

BACKGROUND

It is unclear how different degrees of left-lateral tilt affect the volumes of the abdominal aorta and inferior vena cava (IVC) in pregnancy.

OBJECTIVE

To use magnetic resonance images to assess the volumes of the abdominal aorta and IVC in women with twin or singleton pregnancies in different degrees of left-lateral tilt.

DESIGN

Prospective cohort study.

SETTING

A single-centre university hospital.

PATIENTS

Women with singleton pregnancies (13) and twin pregnancies (13) at 32 to 38 weeks' gestation.

MAIN OUTCOME MEASURES

Comparison of abdominal aortic and IVC volumes measured by MRI in women with singleton and twin pregnancies while in the supine or left-lateral tilt position at 15°, 30° and 45°.

RESULTS

Supine, the mean aortic and IVC volumes were not significantly different between the women with singleton and twin pregnancies. In a left-lateral tilt position of 15 o compared with supine, the mean IVC volume was not increased in either group (singletons: 6.3 ± 6.6 ml, 95% CI, -2.4 to 0.4; P  = 0.174; twins: 3.9 ± 2.4 ml, 95% CI, -2.6 to 0.4; P  = 0.138). At tilt angles of 30° or 45°, the mean IVC volume significantly increased (singletons 30°: 9.7 ± 5.8 ml, 95% CI, -6.1 to -2.7; P  < .001; singleton 45°:13.8 ± 5.0 ml, 95% CI, -11.3 to -5.7; P  < .001; twins 30°: 5.7 ± 2.1 ml, 95% CI, -4.0 to -1.4; P  < .001; twins 45°: 12.8 ± 9.4 ml, 95% CI, -17.2 to -2.6; P  = 0.003). Aortic volume was not significantly increased in either group at any of the examined tilt angles compared with the supine.

CONCLUSION

IVC volume is significantly increased by 30° and 45° left-lateral tilt positions compared with supine in women with singleton and twin pregnancies.

TRIAL REGISTRATION

This study was registered in the University Hospital Medical Information Network (UMIN) clinical trial registration (# UMIN000031273).

Comparison of Prophylactic Norepinephrine and Phenylephrine Infusions During Spinal Anaesthesia for Primary Caesarean Delivery in Twin Pregnancies: A Randomized Double-Blinded Clinical Study

Background

Norepinephrine has been associated with improved heart rate (HR) and cardiac output (CO) compared to phenylephrine as a treatment for post-spinal hypotension during caesarean delivery (CD) in singleton pregnancies. Our current study compared the effects of norepinephrine and phenylephrine in maintaining maternal hemodynamics after spinal anaesthesia in twin pregnancies during elective CD.

Methods

This was a double-blinded, randomized, controlled study. From December 2017 to December 2018, 62 women with healthy twin term pregnancies undergoing elective CD under spinal anaesthesia were studied. Following spinal induction, either norepinephrine (6 μg/mL) or phenylepinephrine (75 μg/mL) was infused at 60 mL/h to maintain systolic blood pressure (SBP) near baseline until delivery. HR, SBP, systemic vascular resistance (SVR), and CO were collected using anaesthesia monitors and continuous-pulse waveform analysis. The primary outcome was maternal CO. Other parameters of maternal hemodynamics, umbilical cord blood gases, and adverse events were also compared.

Results

Hemodynamic variables (CO, SBP, HR, and SVR) between spinal anaesthesia induction to skin incision were similar between the two groups (P = 0.889, 0.057, 0.977, and 0.416, respectively). The incidence of bradycardia was significantly higher in the phenylephrine group (69%) than in the norepinephrine group (24.2%, P<0.001). Maternal nausea and vomiting, hypotension, reactive hypertension, and neonatal outcomes did not differ between the groups.

Conclusion

When administered as a prophylactic fixed-rate infusion, phenylephrine and norepinephrine are both capable of maintaining maternal blood pressure following spinal anaesthesia in twin pregnancies. There were no differences in the maternal hemodynamics or foetal outcomes between women receiving norepinephrine and phenylephrine.

Previous Presentations

Presented at the 51st Society for Obstetric Anesthesia and Perinatology Annual Meeting, Phoenix, Arizona, May 1–5, 2019.

Clinical Trial Number and Registry

No. ChiCTR-IOR-17013358.

Trends of blood pressure and heart rate in normal pregnancies: a systematic review and meta-analysis

BACKGROUND

Current reference ranges for blood pressure and heart rate throughout pregnancy have a poor evidence base.

METHODS

This is a systematic review and meta-analysis. We included studies measuring blood pressure or heart rate from healthy pregnant women within defined gestational periods of 16 weeks or less. We analysed systolic blood pressure, diastolic blood pressure and heart rate by gestational age. We assessed effects of measurement year and method.

RESULTS

We included 39 studies undertaken in 1967-2017, containing 124,349 systolic measurements from 36,239 women, 124,291 diastolic measurements from 36,181 women and 10,948 heart rate measurements from 8317 women. Mean (95% CI) systolic blood pressure was lowest at 10 weeks gestation, 110.4 (108.5, 112.3) mmHg, rising to 116.0 (113.6, 118.4) mmHg at 40 weeks, mean (95% CI) change 5.6 (4.0, 7.2) mmHg. Mean (95% CI) diastolic blood pressure was lowest at 21 weeks gestation, 65.9 (64.2, 67.7) mmHg; rising to 72.8 (71.0, 74.6) mmHg at 40 weeks, mean (95% CI) change 6.9 (6.2, 7.5) mmHg. Mean (95% CI) heart rate rose from 79.3 (75.5, 83.1) beats/min at 10 weeks to 86.9 (82.2, 91.6) beats/min at 40 weeks gestation, mean (95% CI) change 7.6 (1.8, 13.4) beats/min. Studies using manual measurement reported higher diastolic blood pressures than studies using automated measurement, mean (95 CI) difference 4.9 (0.8, 8.9) mmHg. Diastolic blood pressure increased by 0.26 (95% CI 0.10-0.43) mmHg/year. Including only higher-quality studies had little effect on findings, with heterogeneity remaining high (I2 statistic > 50%).

CONCLUSIONS

Significant gestational blood pressure and heart rate changes occur that should be taken into account when assessing pregnant women. Commonly taught substantial decreases in blood pressure mid-pregnancy were not seen and heart rate increases were lower than previously thought. Manual and automated blood pressure measurement cannot be used interchangeably. Increases in diastolic blood pressure over the last half-century and differences between published studies show contemporary data are required to define current normal ranges.

STUDY REGISTRATION

PROSPERO CRD42014009673.

Comparison of Phenylephrine and Ephedrine in Treatment of Spinal-Induced Hypotension in High-Risk Pregnancies: A Narrative Review

Purpose

To compare maternal and fetal effects of intravenous phenylephrine and ephedrine administration during spinal anesthesia for cesarean delivery in high-risk pregnancies.

Source

An extensive literature search was conducted using the US National Library of Medicine, MEDLINE search engine, Cochrane review, and Google Scholar using search terms “ephedrine and phenylephrine,” “preterm and term and spinal hypotension,” “preeclampsia and healthy parturients,” or “multiple and singleton gestation and vasopressor.” Society of Obstetric Anesthesia and Perinatology meeting abstracts for the past 4 years were also searched for relevant studies.

Principle findings

Both phenylephrine and ephedrine can be safely used to counteract hypotension after spinal anesthesia in patients with uteroplacental insufficiency, pregnancy-induced hypertension, and in non-elective cesarean deliveries. Vasopressor requirements before delivery in high-risk cesarean sections are reduced compared to healthy parturients. Among the articles reviewed, there were no statistically significant differences in umbilical arterial pH, umbilical venous pH, incidence of fetal acidosis, Apgar scores, or maternal hypotension when comparing maternal phenylephrine and ephedrine use.

Conclusion

From the limited existing data, phenylephrine and ephedrine are both appropriate selections for treating or preventing hypotension induced by neuraxial blockade in high-risk pregnancies. There is no clear evidence that either medication is more effective at maintaining maternal blood pressure or has a superior safety profile in this setting. Further investigations are required to determine the efficacy, ideal dosing regimens, and overall safety of phenylephrine and ephedrine administration in high-risk obstetric patients, especially in the presence uteroplacental insufficiency.

Vasopressors in obstetrics

Hypotension is a common, treatable side effect of neuraxial anesthesia, which has significant side effects for the mother and demonstrable biochemical effects in the fetus. It is clear that a shift in management of hypotension in the obstetric population is in order, but we can only speculate on the benefits for the compromised fetus due to the lack of available information in that patient population.