The diverse effects of vasopressors on the fetoplacental circulation of the dual perfused human placenta

The effects of inflammation and acidosis on placental blood vessels reactivity

INTRODUCTION

Inflammation and acidosis are two stress stimuli that correspond to pathophysiological processes occurring in placental-mediated vascular disorders. We aimed to investigate the effects of these stimuli on placental chorionic blood vessels reactivity using the ex-vivo placental perfusion model.

METHODS

Term placentas were obtained immediately after cesarean deliveries, and selected cotyledons were cannulated and dually perfused ex-vivo. Placentas were perfused with three different protocols: culture medium (M199-controls, n = 5), culture medium with lipopolysaccharide (inflammatory stimuli) (LPS,1 μg/ml, n = 7), and acidotic culture medium (M - 199, pH: 6.9-7, n = 6). Each perfusion experiment was maintained for 180 min. Fetal perfusion pressure was continuously measured. Measurements in response to angiotensin II (AT II) at the end of the perfusion were compared between the treatment groups, including amplitude of the contraction response, relaxation factor, time to maximal constriction and the area under the pressure curve (AUC).

RESULTS

In response to ATII there was a significant difference in the amplitude of the contraction and the AUC between the treatment groups, (p = 0.049, p = 0.015, respectively). As compared with control perfused cotyledon, the inflammatory stimuli significantly increased the vasoconstriction response to ATII in fetal placental blood vessels, as expressed by increased AUC - median (IQR): 555 (235-1184) vs. 133 (118-207), respectively, p = 0.017. The time to maximal constriction and the relaxation factor did not differ between the groups.

DISCUSSION

Inflammatory stimuli but not acidosis impact fetal-placental vasculature in response to ATII, suggesting that inflammation can compromise vascular function.

Fetoplacental vascular effects of maternal adrenergic antihypertensive and cardioprotective medications in pregnancy

Maternal cardiovascular diseases, including hypertension and cardiac conditions, are associated with poor fetal outcomes. A range of adrenergic antihypertensive and cardioprotective medications are often prescribed to pregnant women to reduce major maternal complications during pregnancy. Although these treatments are not considered teratogenic, they may have detrimental effects on fetal growth and development, as they cross the fetoplacental barrier, and may contribute to placental vascular dysregulation. Medication risk assessment sheets do not include specific advice to clinicians and women regarding the safety of these therapies for use in pregnancy and the potential off-target effects of adrenergic medications on fetal growth have not been rigorously conducted. Little is known of their effects on the fetoplacental vasculature. There is also a dearth of knowledge on adrenergic receptor activation and signalling within the endothelium and vascular smooth muscle cells of the human placenta, a vital organ in the maintenance of adequate blood flow to satisfy fetal growth and development. The fetoplacental circulation, absent of sympathetic innervation, and unique in its reliance on endocrine, paracrine and autocrine influence in the regulation of vascular tone, appears vulnerable to dysregulation by adrenergic antihypertensive and cardioprotective medications compared with the adult peripheral circulation. This semi-systematic review focuses on fetoplacental vascular expression of adrenergic receptors, associated cell signalling mechanisms and predictive consequences of receptor activation/deactivation by antihypertensive and cardioprotective medications.

Incidence of bradycardia during noradrenaline or phenylephrine bolus treatment of postspinal hypotension in cesarean delivery: A randomized double-blinded controlled trial

The treatment of choice for spinal anesthesia-induced hypotension during cesarean section is phenylephrine. As this vasopressor can cause reflex bradycardia, noradrenaline is a suggested alternative. This randomized double-blinded controlled trial included 76 parturients undergoing elective cesarean delivery under spinal anesthesia. Women received noradrenaline in bolus doses of 5 mcg or phenylephrine in bolus doses of 100 mcg. These drugs were used intermittently and therapeutically to maintain systolic blood pressure ≥ 90% of its baseline value. The primary study outcome was bradycardia incidence (<60 bpm) with intermittent bolus administration of these drugs. Secondary outcomes included extreme bradycardia (<40 bpm), number of bradycardia episodes, hypertension (systolic blood pressure > 120% of baseline value), and hypotension (systolic blood pressure < 90% of baseline value and requiring vasopressor use). Neonatal outcomes per the Apgar scale and umbilical cord blood gas analysis were also compared. The incidence of bradycardia in both groups (51.4% and 70.3%, respectively; p = 0.16) were not significantly different. No neonates had umbilical vein or artery pH values below 7.20. The noradrenaline group required more boluses than phenylephrine group (8 vs. 5; p = 0.01). There was no significant intergroup difference in any of the other secondary outcomes. When administered in intermittent bolus doses for the treatment of postspinal hypotension in elective cesarean delivery, noradrenaline, and phenylephrine have a similar incidence of bradycardia. When treating hypotension related to spinal anesthesia in obstetric cases, strong vasopressors are commonly administered, thought these can also have side effects. This trial assessed bradycardia after bolus administration of noradrenaline or phenylephrine, and found no difference in risk for clinically meaningful bradycardia.

Aneurysmal subarachnoid hemorrhage during pregnancy: a comprehensive and systematic review of the literature

Aneurysmal subarachnoid hemorrhage (aSAH) is an emergent condition requiring rapid intervention and prolonged monitoring. There are few recommendations regarding the management of aSAH in pregnancy. We identified all available literature and compiled management decisions as well as reported outcomes through a systematic literature review without meta-analysis to provide recommendations for management of aSAH during pregnancy. We included a total of 23 articles containing 54 cases of pregnancy-related aSAH in our review. From these reports and other literature, we evaluated information on aSAH pathophysiology, diagnosis, and management with respect to pregnancy. Early transfer to an appropriate facility with neurocritical care, a high-risk obstetric service, and a neurosurgery team available is crucial for the management of aSAH in pregnancy. Intensive monitoring and a multidisciplinary approach remain fundamental to ensure maternal and fetal health.

A randomised dose-response study of prophylactic Methoxamine infusion for preventing spinal-induced hypotension during Cesarean delivery

BACKGROUND

α-receptor agonists have been reported to be safe and effective for treating or preventing spinal-induced hypotension during cesarean delivery. As a pure α₁ adrenergic agonist, methoxamine has potential advantages of reducing myocardial oxygen consumption and protecting the heart in obstetric patients compared to phenylephrine. The aim of this study was to determine the optimal prophylactic methoxamine infusion dose that would be effective for preventing spinal-induced hypotension in 50% (ED₅₀) and 95% (ED₉₅) of parturients.

METHODS

Eighty parturients with a singleton pregnancy scheduled for elective cesarean delivery were randomly allocated to receive prophylactic methoxamine infusion at one of four different fixed-rates: 1 μg/kg/min (group M1), 2 μg/kg/min (group M2), 3 μg/kg/min (group M3), or 4 μg/kg/min (group M4). An adequate response was defined as absence of hypotension (maternal SBP < 80% of baseline or SBP < 90 mmHg). The values for ED₅₀ and ED₉₅ of prophylactic methoxamine infusion were determined by probit regression model. The outcomes of maternal hemodynamics and fetal status were compared among the groups.

RESULTS

The calculated ED₅₀ and ED₉₅ (95% confidence interval) of prophylactic methoxamine infusion dose were 2.178 (95% CI 1.564 to 2.680) μg/kg/min and 4.821 (95% CI 3.951 to 7.017) μg/kg/min, respectively. The incidence of hypotension decreased with increasing methoxamine infusion dose (15/20, 11/20, 7/20 and 2/20 in group M1, M2, M3 and M4 respectively, P <  0.001). 1-min Apgar scores and umbilical arterial PaO2 were lower but umbilical arterial PaCO2 was higher in Group M1. No difference was found in the other incidence of adverse effects and neonatal outcomes among groups.

CONCLUSIONS

Under the conditions of this study, when prophylactic methoxamine infusion was given at a fixed-rate based on body weight for preventing spinal-induced hypotension in obstetric patients, the values for ED₅₀ and ED₉₅ were 2.178 μg/kg/min and 4.821 μg/kg/min respectively.

CLINICAL TRIAL REGISTRATION

Chinese Clinical Trial Registry (ChiCTR), registry number of clinical trial: ChiCTR-1,800,018,988 , date of registration: October 20, 2018.

A randomized double-blind study comparing prophylactic norepinephrine and ephedrine infusion for preventing maternal spinal hypotension during elective cesarean section under spinal anesthesia: A CONSORT-compliant article

BACKGROUND

Studies have shown the efficacy of norepinephrine in the treatment of maternal hypotension during cesarean section by comparing it to treatment with phenylephrine. However, few studies have compared the efficacy of norepinephrine to ephedrine.

METHODS

Ninety-seven women undergoing elective cesarean section were administered norepinephrine at 4 μg/minute (group N; n = 48) or ephedrine at 4 mg/minute (group E; n = 49) immediately postspinal anesthesia, with an on-off titration to maintain systolic blood pressure (SBP) at 80% to 120% of baseline. A rescue bolus of 8 μg norepinephrine was given whenever SBP reached the predefined lower limit. Our primary outcome was the incidence of tachycardia. Secondary outcomes included the incidence of bradycardia, hypertension, hypotension, severe hypotension, hypotensive episodes, number of rescue top-ups, hemodynamic performance error including median performance error (MDPE), and median absolute performance error (MDAPE). Neonatal Apgar scores and umbilical arterial (UA) blood gas data were also collected.

RESULTS

Women in group N experienced fewer cases of tachycardia (4.2% vs 30.6%, P = .002, odds ratio: 0.11 [95% confidence interval, CI: 0.02-0.47]), a lower standardized heart rate (HR) (70.3 ± 11 vs 75 ± 11, P = .04, difference: 4.7 ± 2.2 [95% CI: 0.24-9.1]), and a lower MDPE for HR (1.3 ± 9.6 vs 8.4 ± 13.5 bpm, P = .003, difference: 3.1 ± 1.8 [95% CI: -0.6-6.7]). In addition, the lowest or the highest HR was lower in group N compared to group E (both P < .05). Meanwhile, the standardized SBP in group N was lower than that in group E (P = .04). For neonates, the UA blood gas showed a higher base excess (BE) and a lower lactate level in group N compared to E (both P < .001). Other hemodynamic variables, maternal, and neonatal outcomes were similar.

CONCLUSION

Infusion of 4 μg/minute norepinephrine presented fewer cases of tachycardia, less fluctuation and a lower HR compared to baseline values, as well as a less stressed fetal status compared to ephedrine infusion at 4 mg/minute. In addition, norepinephrine infusion presented a lower standardized SBP compared to ephedrine.

A Comparative Study of Bolus Norepinephrine, Phenylephrine, and Ephedrine for the Treatment of Maternal Hypotension in Parturients with Preeclampsia During Cesarean Delivery Under Spinal Anesthesia

Background

This study aimed to compare the efficacy and safety of bolus norepinephrine, phenylephrine, and ephedrine in parturient with preeclampsia who had hypotension during cesarean delivery under spinal anesthesia.

Material/Methods

One hundred and sixty-six parturient women with preeclampsia who had a baseline systolic blood pressure (SBP) <80% during spinal anesthesia for cesarean section were divided into three treatment groups; bolus norepinephrine 4 μg (group N) (n=56), phenylephrine 50 μg (group P) (n=55), and ephedrine 4 mg (group E) (n=55). Primary outcomes included overall SBP and heart rate (HR) until delivery. Secondary outcomes included the incidence of tachycardia (HR >120 bpm), bradycardia (HR <60 bpm), hypertension (SBP >120% baseline), number of boluses of vasopressor required and episodes of hypotension, maternal side effects, and neonatal outcome.

Results

Overall HR in group N was significantly increased compared with group P (80.5±12 vs. 76.6±6.9 bpm; P=0.04), and significantly lower compared with group E (80.5±12 vs. 84.9±7.1 bpm; P=0.02). Parturients in group N had fewer episodes of bradycardia compared with group P (3.6% vs. 21.8%; RR=0.26l; 95% CI, 0.07–0.73; P=0.004) and fewer episodes of tachycardia compared with group E (16.1% vs. 36.4%; RR 0.54; 95% CI, 0.29–0.90; P=0.02).

Conclusions

A bolus dose of norepinephrine showed similar efficacy to phenylephrine but improved maternal and neonatal safety in parturients with preeclampsia with hypotension during cesarean section under spinal anesthesia.

Comparison of Ephedrine vs. Norepinephrine in Treating Anesthesia-Induced Hypotension in Hypertensive Patients: Randomized Double-Blinded Study

Background

Hypotension is a common problem in general anesthesia. Maintaining the mean arterial pressure by choosing a vasopressor with minimal complications is still discussed in various surgeries.

Objectives

The aim of this study is comparison of ephedrine versus norepinephrine in treating anesthesia-induced hypotension in hypertensive patients in spinal surgery in a randomized double-blinded study.

Methods

This randomized, double-blinded study was approved by Iran University of Medical Sciences, operating room of medical center. Data collection was completed between Jan to Dec 2017. Inclusion criteria included age between 20 and 75 years, history of high blood pressure (a patient who has been treated for maximum 5 years with a anti hypertensive medication), and patients under general anesthesia in spinal surgery. The exclusion criteria were based on American Society of Anesthesiologists physical status of 3 or higher, history of arrhythmia, heart valve disease, cerebrovascular disease, kidney failure, beta-blocker use and diabetes, as well as intra operative massive blood loss. After initiation of anesthesia, when the pressure reaches less than 60, the patient entered the protocol and simultaneously administration of 5 mL/kg serum crystalloid and vasopressor. Patients were randomized to the ephedrine group (n = 28) who received 5 mg ephedrine intravenous (i.v.) or norepinephrine Group (n = 28) who received 10 µg (i.v.) bolus norepinephrine at anesthesia-induced hypotension. The administration of 5 mL/kg serum crystalloid and vasopressor was simultaneous. If the mean arterial pressure (MAP) had not reached 60 mmHg, the same dose should be repeated at a maximum of three or more times at five-minute intervals in the ephedrine group and at two minutes intervals in the norepinephrine group. All parameters were collected before and at the end of administration anesthesia drug and during episodes of hypotension. Hemodynamic variables, frequency of hypotension, and total number of vasopressors doses during anesthesia were recorded and analyzed.

Results

The mean number of hypotension times, the number of vasopressors doses in the first hypotension, the total number of doses consumed during the anesthesia, and heart rate at the end of anesthesia were lower in the norepinephrine group (P) respectively. MAP, 5 minutes after the first episode of hypotension and MAP at the end of anesthesia were higher in norepinephrine group.

Conclusions

Norepinephrine is more effective than ephedrine in maintenance of MAP in hypertensive patients undergoing spinal surgery under general anesthesia.

Sepsis in pregnancy and the puerperium

Sepsis remains a leading cause of maternal morbidity and mortality. Recognition and treatment of maternal sepsis are often delayed due to the physiological adaptations of pregnancy and vague or absent signs and symptoms during its initial presentation. Over the past decade, our understanding of sepsis has evolved and maternal early warning systems have been developed in an effort to help providers promptly identify and stratify parturients who are at risk. In addition, new consensus definitions and care bundles have recently been published by the World Health Organization and the Surviving Sepsis Campaign to facilitate earlier recognition and timely management of sepsis. In this narrative review, we summarize the available evidence about sepsis and provide an overview of the research efforts focused on maternal sepsis to date. Controversies and challenges surrounding the anesthetic management of parturients with sepsis or at risk of developing sepsis during pregnancy or the puerperium will be highlighted.

Norepinephrine versus Ephedrine to Maintain Arterial Blood Pressure during Spinal Anesthesia for Cesarean Delivery: A Prospective Double-blinded Trial

Background:

Ephedrine was conventionally regarded as the first-choice drug to maintain maternal blood pressure during spinal anesthesia for cesarean delivery, due to its stimulant activity on α- and β-adrenergic receptors. Norepinephrine is a weak β-adrenergic and potent α-adrenergic receptor agonist. Therefore, it may be suitable for maintaining blood pressure with less chronotropic effects compared to ephedrine.

Patients and Methods:

One hundred and forty healthy patients having cesarean delivery under spinal anesthesia were randomized to Group N (n = 61) who received a prophylactic bolus of norepinephrine 5 μg intravenous (i.v.) at the time of intrathecal block or Group E (n = 61) who received a prophylactic bolus of i.v. ephedrine 10 mg. Rescue i.v. bolus interventions of norepinephrine 5 μg or ephedrine 10 mg were given as required to maintain systolic blood pressure. Maternal and fetal hemodynamic variables, Apgar score, and number of boluses of vasopressors used were recorded.

Results:

The numbers of maternal hypotension and hypertension episodes and the frequency of bradycardia and tachycardia were significantly lower in Group N compared with Group E (P = 0.02, 0.003, 0.0002, and 0.008, respectively). The number of boluses of vasopressors used was also lower in Group N (P = 0.005). Uterine artery pulsatility index was lower in Group N compared to Group E (P = 0.01) when measured 5 min after spinal anesthesia. Moreover, it was higher at 5 min in Group E when compared with the baseline readings in the same group (P = 0.001).

Conclusions:

Norepinephrine is a suitable and potent drug to counterbalance the hemodynamic effects of spinal anesthesia during cesarean delivery.

Feeding Your Baby In Utero: How the Uteroplacental Circulation Impacts Pregnancy

The utero-placental circulation links the maternal and fetal circulations during pregnancy, ensuring adequate gas and nutrient exchange, and consequently fetal growth. However, our understanding of this circulatory system remains incomplete. Here, we discuss how the utero-placental circulation is established, how it changes dynamically during pregnancy, and how this may impact on pregnancy success, highlighting how we may address knowledge gaps through advances in imaging and computational modeling approaches.

Phenylephrine infusion for spinal-induced hypotension in elective cesarean delivery: Does preload make a difference?

Background and Aims:

Patients undergoing elective cesarean delivery (CD) have a high-risk of spinal-induced hypotension (SIH). We hypothesized that a colloid preload would further reduce SIH when compared with a crystalloid preload.

Material and Methods:

Eighty-two healthy parturients undergoing elective CD were included in the study. Patients were randomly assigned to two groups (41 patients in each group) to receive either Lactated Ringer's solution (1500 ml) or hydroxyethyl starch (6% in normal saline, 500 ml) 30 min prior to placement of spinal anesthesia. All patients were treated with a phenylephrine infusion (100 mcg/min), titrated during the study.

Results:

There was no statistical difference between groups with regards to the incidence of hypotension (10.8% in the colloid group vs. 27.0% in the crystalloid group, P = 0.12). There was also no difference between groups with respect to bradycardia, APGAR scores, and nausea and vomiting. Significantly less phenylephrine (1077.5 ± 514 mcg) was used in the colloid group than the crystalloid group (1477 ± 591 mcg, P = 0.003).

Conclusion:

The preload with 6% of hydroxyethyl starch before CD might be beneficial for the prevention of SIH.

Caesarean delivery vasopressor management

PURPOSE OF REVIEW

This review assesses the maternal and fetal effects of vasopressor administration during spinal anaesthesia for caesarean delivery, with emphasis on recent findings.

RECENT FINDINGS

Maternal heart rate is a good surrogate for cardiac output. The initial hypotensive effect of spinal anaesthesia is caused by a rapid decrease in systemic vascular resistance, which makes α-agonists the logical first-line therapy. Effective prophylactic phenylephrine administration can be associated with reduced maternal cardiac output, but this has not been associated with adverse maternal or fetal effects. Prophylactic phenylephrine infusion can cause hypertension if increasing arterial pressure does not trigger a timely reduction in the rate of administration. Phenylephrine has been used safely in mothers with cardiac disease and in pregnancies with suspected fetal compromise. Fetal genotype may increase resistance to ephedrine-induced acidosis. The combination of vagolytics and vasopressors has caused maternal hypertensive crises with serious adverse outcome.

SUMMARY

Phenylephrine is the current vasopressor of choice for the prevention of maternal hypotension and nausea. Phenylephrine regimens need to be developed that can reliably and safely be used with noninvasive blood pressure cycle times less frequent than every minute. Further vasopressor should be used with caution when vagolytic therapy is, quite rightly, used to treat bradycardia associated with hypotension.

Reactivity of blood vessels in response to prostaglandin E2 in placentas from pregnancies complicated by fetal growth restriction

OBJECTIVE

The authors aimed to study the contractility responses of normal and fetal growth restriction (FGR) placentas to prostaglandin E(2) (PGE(2) ) and to correlate the results to subsequent placental histological analysis.

METHOD

A dual-perfused single cotyledon model was used. Placentas from pregnancies complicated by FGR and from normal pregnancies were obtained. Selected cotyledons were cannulated and dually perfused. Following stabilization, three concentrations of PGE(2) (0.05, 0.1, and 0.15 mg/mL) were administered to the fetal arterial side causing contraction/relaxation response. Fetal perfusion pressure was measured continuously during these contraction and relaxation phases. Following the perfusion experiments, the placentas were analyzed for fetal or maternal origin vascular lesions.

RESULTS

A total of 21 complete experiments were performed (16 normal, 5 FGR). In response to PGE(2) , FGR placentas exhibited lower change in the perfusion pressure and lower relaxation time constant. Basal perfusion pressure did not differ significantly between the two groups. Placental histopathology lesions, fetal or maternal origin, were more common in the FGR compared with the controls placentas, 80% versus 25%, respectively, P=  0.047.

CONCLUSIONS

The lower vascular reactivity in response to PGE(2) and the presence of fetal and maternal vascular placental lesions suggest a mechanism explaining the altered vascular supply in FGR.