Pregnancy reference intervals and exertion and breathlessness ratings for the six minute walk test in healthy nulliparous people

Background

The Six Minute Walk Test (6MWT) is a simple, non-invasive, well-validated test that assesses cardiorespiratory fitness however is rarely used in pregnant people. It may have clinical utilization to assess fitness, breathing and exertion in pregnancy however no reference intervals exist for people 14+0 to 35+6 weeks gestation. We determined the reference intervals for distance walked for the 6MWT, including exertional and breathlessness ratings for this group.

Method

We conducted a prospective observational cohort study of 196 healthy nulliparous pregnant people in earlier pregnancy (EP) 14+0 to 23+6 weeks, and middle pregnancy (MP) 24+0 to 35+6 gestation, who performed a standardized 6MWT protocol including rating exertion and breathlessness (Rating Perceived Exertion (RPE) scale (1 none -15 maximal) and Modified Borg Dyspnea (MBD) scale (0 none - 10 maximal)).

Results

The mean ± SD distance walked was 548 ± 80.9 (EP) versus 547 ± 87.3 (MP) meters (m) P = 0.928. 6MWT reference intervals for the distance walked for the 6MWT were 392-704 m (EP) and 376-718 m (MP). Median (IQR) exertion and breathlessness ratings with exercise for the EP and MP group were 6 (4,7) and 0.5 (0,1) and 6 (4,8) and 0.5 (0,1) respectively. There were no adverse events.

Conclusion

The 6MWT is safe, feasible and acceptable in pregnant people. The reference intervals for the 6MWT are 392-704 m in people 14+0 to 23+6 weeks gestation and 376-718 m for people 24+0 to 35+6 weeks gestation. Exertion was light and breathlessness was just noticeable with the 6MWT.

Baseline haemoglobin variability by measurement technique in pregnant people on the day of childbirth

Point-of-care haemoglobin measurement devices may play an important role in the antenatal detection of anaemia in pregnant people and may be useful in guiding blood transfusion during resuscitation in obstetric haemorrhage. We compared baseline haemoglobin variability of venous and capillary HemoCue® haemoglobin, and Masimo® Rad-67 Pulse CO-Oximeter haemoglobin with laboratory haemoglobin in people on the day of their planned vaginal birth. A total of 180 people undergoing planned vaginal birth were enrolled in this prospective observational study. Laboratory haemoglobin was compared with HemoCue and Masimo Rad-67 Pulse CO-Oximeter measurements using Bland-Altman analysis, calculating mean difference (bias) and limits of agreement. Five (2.8%) people had anaemia (haemoglobin < 110 g.l-1 ). Laboratory haemoglobin and HemoCue venous haemoglobin comparison showed an acceptable bias (SD) 0.7 (7.54) g.l-1 (95%CI -0.43-1.79), with limits of agreement -14.10-15.46 g.l-1 and acceptable agreement range of 29.6 g.l-1 . Laboratory and HemoCue capillary haemoglobin comparison showed an unacceptable bias (SD) 13.3 (14.12) g.l-1 (95%CI 11.17-15.34), with limits of agreement - 14.42-40.93 g.l-1 and unacceptable agreement range of 55.3 g.l-1 . Laboratory and Masimo haemoglobin comparison showed an unacceptable bias (SD) -14.0 (11.15) g.l-1 (95%CI -15.63 to -12.34), with limits of agreement to -35.85 to 7.87 g.l-1 and acceptable agreement range of 43.7 g.l-1 . Venous HemoCue, with its acceptable bias and limits of agreement, should be applied more widely in the antenatal setting to detect, manage and risk stratify pregnant people with anaemia. HemoCue capillary measurement under-estimated haemoglobin and Masimo haemoglobin measurement over-estimated, limiting their clinical use. Serial studies are needed to determine if the accuracy of venous HemoCue haemoglobin measurement is sustained in other obstetric settings.

Perioperative Exercise Testing in Pregnant and Non-Pregnant Women of Reproductive Age: A Systematic Review

BACKGROUND

Women have classically been excluded from the development of normal data and reference ranges, with pregnant women experiencing further neglect. The incidence of Caesarean section in pregnant women, and of general operative management in young women (both pregnant and non-pregnant), necessitates the formal development of healthy baseline data in these cohorts to optimise their perioperative management. This systematic review assesses the representation of young women in existing reference ranges for several functional exercise tests in common use to facilitate functional assessment in this cohort.

METHODS

Existing reference range data for the exercise tests the Six Minute Walk Test (6MWT), the Incremental Shuttle Walk Test (ISWT) and Cardiopulmonary Exercise Testing (CPET) in young women of reproductive age were assessed using the MEDLINE (Ovid) database, last searched December 2023. Results were comparatively tabulated but not statistically analysed given underlying variances in data.

RESULTS

The role of exercise testing in the perioperative period as an assessment tool, as well as its safety during pregnancy, was evaluated using 65 studies which met inclusion criteria.

CONCLUSION

There is a significant lack of baseline data regarding these tests in this population, especially amongst the pregnant cohort, which limits the application of exercise testing clinically.

Perioperative Complications in Patients with Preeclampsia Undergoing Caesarean Section Surgery

Caesarean section has risks of bleeding, infection and thromboembolism, and neuroendocrine-metabolic, and inflammatory-immune responses that may worsen outcomes in patients with preeclampsia. There is little research examining perioperative, as opposed to peripartum, outcomes in patients with preeclampsia. We conducted a single-centrecentre retrospective cohort study of perioperative patients with preeclampsia over an eight-month period to determine the rate of perioperative complication. Seventy-two patients were included. The maternal complication rate was 59.7 per 100 operations (95% CI 48.2 to 70.3%). Severe complications included pulmonary oedema 2 (2.8%), haemorrhage > 1000 mL 5 (6.9%), and blood transfusion 2 (2.8%). Twenty (27.8%) patients had a hospital length of stay ≥7 days. The rate of anaemia (haemoglobin < 110 g/L) on hospital discharge was 42 per 100 operations (95% CI 31.0 to 53.2%). Patient representation rate to hospital after discharge was 23.6% per 100 operations (95% CI 15.3 to 34.6%). There were no maternal deaths. The neonatal complication rate was 38.9 per 100 operations (95% CI 28.9 to 51.1%) with one foetal death. Patients with preeclampsia undergoing caesarean section are a very high-risk surgical group who experience significant perioperative complications. Urgent action is needed to confirm these findings and improve outcomes in these patients.

Analysis of anaesthesia incidents during caesarean section reported to webAIRS between 2009 and 2022

Anaesthesia for caesarean section occurs commonly and places specific demands on anaesthetists. We analysed 469 narratives concerning anaesthesia for caesarean section, entered by Australian and New Zealand anaesthetists into the webAIRS incident reporting system between 2009 and 2022. As expected, compared with the remaining 8978 database entries, the 469 incidents were more likely to be emergency cases (relative risk (RR) 1.95), more likely to occur between 18:00 and 22:00 hours (RR 1.81) and between 22:00 and 07:59 hours (RR 4.40) and more likely to be undertaken using neuraxial anaesthesia (RR 9.18). Most incidents involved more than one event. The most commonly reported incidents included intraoperative neuraxial anaesthesia complications (180, 38%), medication errors or issues (136, 29%), equipment issues (49, 10%), obstetric haemorrhage (38, 8%), maternal cardiac arrests (28, 6%), endotracheal tube issues (28, 6%) and neonatal resuscitation (24, 5%). Inadequate neuraxial block, reported in 95 incidents, was the most common intraoperative neuraxial complication. Allergic reactions, reported in 30 incidents, were the most common medication issue, followed by 17 associated with oxytocin and 16 syringe swaps. Thirty-eight reports included significant maternal haemorrhage, with eight of those incidents including maternal cardiac arrest. There was one maternal death and eight incidents with neonatal deaths reported, affecting nine neonates. Problems with intraoperative neuraxial anaesthesia were the most commonly reported events. Implementation of specific strategies are encouraged to enhance preparation for conversion to general anaesthesia and to mitigate medication errors, particularly those relating to oxytocic use and neuraxial anaesthesia medications.

The prevalence of perioperative iron deficiency anaemia in women undergoing caesarean section-a retrospective cohort study

Background

Caesarean section is a common surgery, with almost 23 million procedures performed globally each year. Postpartum haemorrhage, in association with caesarean section surgery, is a leading global cause of maternal morbidity and mortality. Perioperative iron deficiency anaemia is a risk factor for intraoperative bleeding. Therefore, anaemia is an important and modifiable risk factor for bleeding during caesarean section surgery. Recent recommendations advise that all preoperative patients with anaemia (defined as haemoglobin concentration (Hb) < 130 g/L), regardless of sex, be assessed and treated to normalise haemoglobin levels. It is unclear how this recommendation translates to pregnant women where the World Health Organization (WHO) defines anaemia at a much lower threshold (Hb < 110 g/L). We aimed to determine the prevalence, and characterization, of Hb levels < 130 g/L perioperatively in women undergoing caesarean section.

Method

We conducted a retrospective cohort study of 489 consecutive women who underwent caesarean section over a 12-week period, in a single-centre tertiary referral maternity unit in Australia. We calculated the proportion of women who were anaemic (Hb < 130 g/L) at four time points—first hospital appointment, third trimester, preoperatively and on discharge from hospital. The proportion of women who were iron deficient (ferritin level < 30 μg/L) at their first hospital appointment was determined.

Results

Haemoglobin was measured in 479 women. Ferritin was measured in 437 of these women. The mean (SD) Hb at the first hospital appointment, third trimester, preoperatively, and postoperatively on discharge was 126.7 (11.4) g/L, 114.6 (10.6) g/L, 124.1 (12.4) g/L, and 108.0 (13.6) g/L respectively. Iron deficiency was present in 148 (33.9%) women at their first hospital appointment; 107 of 248 (43.1%) women with anaemia and 41 of 189 (21.7%) with no anaemia. 29 women were found to have moderate anaemia (Hb 80−109 g/L) with 18 of these 29 (62.1%) women having iron deficiency. Only 68 (45.9%) women with iron deficiency at their first hospital appointment received treatment. The prevalence of anaemia classified as Hb < 130 g/L versus the WHO classification of Hb < 110 g/L from all causes was 57.4% versus 6.1% at first hospital appointment, 94% versus 26.1% in third trimester, and 66.0% versus 12.2% preoperatively. Postoperatively at least 40% of women had Hb < 130 g/L on hospital discharge versus at least 23% of women using WHO definition of Hb < 110 g/L. Of the 112 women with hospital discharge Hb < 110 g/L, 35 (31.3%) women were iron deficient at their first hospital appointment.

Conclusion

Over one in three women were iron deficient at their first hospital appointment. 62% of women with moderate anaemia (Hb 80–109 g/L) also had iron deficiency. At least four in 10 women were anaemic (Hb < 130 g/L) on hospital discharge. Less than half of the women with anaemia were treated. Our data suggests that 30% of postoperative anaemia may be prevented with intensive treatment of iron deficiency in early pregnancy. Large prospective studies, are needed to determine outcomes after caesarean section in women, stratified by preoperative Hb and ferritin levels. The prevalence of anaemia in our data suggests it is a moderate public health problem.

Optic nerve sonography and ophthalmic artery Doppler velocimetry in healthy pregnant women: an Australian cohort study

PURPOSE

Maternal ocular sonography offers a window into cerebrovascular and intracranial pressure changes in pregnancy. This study aimed to determine the Doppler velocimetric variables of the ophthalmic artery, and the mean diameter of the optic nerve sheath (ONSD), in an Australian cohort of healthy pregnant women.

METHODS

A prospective observational cohort study of healthy women with uncomplicated singleton pregnancies in the third trimester was undertaken in a tertiary maternity service. A single prenatal ultrasonographic examination was performed on all participants, with a postnatal examination performed on a subgroup with uncomplicated deliveries.

RESULTS

Fifty women were examined at a mean gestation of 35 weeks. The mean ± SD Doppler variables in the ophthalmic artery were peak systolic velocity (PSV) 41.89 ± 13.13 cm/s, second peak velocity 20.63 ± 8.97 cm/s, end diastolic velocity 9.29 ± 5.13 cm/s, pulsatility index 1.97 ± 0.53, resistive index 0.78 ± 0.07, peak ratio (second peak velocity/PSV) 0.49 ± 0.12, while the mean ONSD was 4.34 ± 0.4 mm. None of these variables had a demonstrable relationship with gestation or mean arterial pressure (MAP), nor did the sheath diameter have a relationship with any of the Doppler variables.

CONCLUSIONS

The ocular sonographic variables observed in this population are similar to those reported in other cohorts. No clear relationship could be identified in this cohort between ophthalmic artery Doppler variables and the ONSD, and between each of these variables and gestation or MAP.

Combined spinal-epidural versus spinal anaesthesia for caesarean section

BACKGROUND

Single-shot spinal anaesthesia (SSS) and combined spinal-epidural (CSE) anaesthesia are both commonly used for caesarean section anaesthesia. Spinals offer technical simplicity and rapid onset of nerve blockade which can be associated with hypotension. CSE anaesthesia allows for more gradual onset and also prolongation of the anaesthesia through use of a catheter.

OBJECTIVES

To compare the effectiveness and adverse effects of CSE anaesthesia to single-shot spinal anaesthesia for caesarean section.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP), and reference lists of retrieved studies (search date: 8 August 2019).

SELECTION CRITERIA

We considered all published randomised controlled trials (RCTs) involving a comparison of CSE anaesthesia with single-shot spinal anaesthesia for caesarean section. We further subgrouped spinal anaesthesia as either high-dose (10 or more mg bupivacaine), or low-dose (less than 10 mg bupivacaine).

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and risks of bias, extracted data and checked them for accuracy. We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We identified 18 trials including 1272 women, but almost all comparisons for individual outcomes involved relatively small numbers of women. Two trials did not report on this review's outcomes and therefore contribute no data towards this review. Trials were conducted in national or university hospitals in Australia (1), Croatia (1), India (1), Italy (1), Singapore (3), South Korea (4), Spain (1), Sweden (1), Turkey (2), UK (1), USA (2). The trials were at a moderate risk of bias overall.CSE versus high-dose spinal anaesthesiaThere may be little or no difference between the CSE and high-dose spinal groups for the number of women requiring a repeat regional block or general anaesthetic as a result of failure to establish adequate initial blockade (risk ratio (RR) 0.32, 95% confidence interval (CI) 0.05 to 1.97; 7 studies, 341 women; low-quality evidence). We are uncertain whether having CSE or spinal makes any difference in the number of women requiring supplemental intra-operative analgesia at any time after CSE or spinal anaesthetic insertion (average RR 1.25, 95% CI 0.19 to 8.43; 7 studies, 390 women; very low-quality evidence), or the number of women requiring intra-operative conversion to general anaesthesia (RR 1.00, 95% CI 0.07 to 14.95; 7 studies, 388 women; very low-quality evidence). We are also uncertain about the results for the number of women who were satisfied with anaesthesia, regardless of whether they received CSE or high-dose spinal (RR 0.93 95% CI 0.73 to 1.19; 2 studies, 72 women; very low-quality evidence). More women in the CSE group (13/21) experienced intra-operative nausea or vomiting requiring treatment than in the high-dose spinal group (6/21). There were 11 cases of post-dural puncture headache (5/56 with CSE versus 6/57 with SSS; 3 trials, 113 women) with no clear difference between groups. There was also no clear difference in intra-operative hypotension requiring treatment (46/86 with CSE versus 41/76 with SSS; 4 trials, 162 women). There were no babies with Apgar score less than seven at five minutes (4 trials, 182 babies).CSE versus low-dose spinal anaesthesiaThere may be little or no difference between the CSE and low-dose spinal groups for the number of women requiring a repeat regional block or general anaesthetic as a result of failure to establish adequate initial blockade (RR 4.81, 95% CI 0.24 to 97.90; 3 studies, 224 women; low-quality evidence). Similarly, there is probably little difference in the number of women requiring supplemental intra-operative analgesia at any time after CSE or low-dose spinal anaesthetic insertion (RR 1.75, 95% CI 0.78 to 3.92; 4 studies, 298 women; moderate-quality evidence). We are uncertain about the effect of CSE or low-dose spinal on the need for intra-operative conversion to general anaesthesia, because this was not required by any of the 222 women in the three trials (low-quality evidence). None of the studies examined whether women were satisfied with their anaesthesia.The mean time to effective anaesthesia was faster in women who received low-dose spinal compared to CSE, although it is unlikely that the magnitude of this difference is clinically meaningful (standardised mean difference (SMD) 0.85 minutes, 95% CI 0.52 to 1.18 minutes; 2 studies, 160 women).CSE appeared to reduce the incidence of intra-operative hypotension requiring treatment compared with low-dose spinal (average RR 0.59, 95% CI 0.38 to 0.93; 4 studies, 336 women). Similar numbers of women between the CSE and low-dose spinal groups experienced intra-operative nausea or vomiting requiring treatment (3/50 with CSE versus 6/50 with SSS; 1 study, 100 women), and there were no cases of post-dural puncture headache (1 study, 138 women). No infants in either group had an Apgar score of less than seven at five minutes (1 study; 60 babies).

AUTHORS' CONCLUSIONS

In this review, the number of studies and participants for most of our analyses were small and some of the included trials had design limitations. There was some suggestion that, compared to spinal anaesthesia, CSE could be associated with a reduction in the number of women with intra-operative hypotension, but an increase in intra-operative nausea and vomiting requiring treatment. One small study found that low-dose spinal resulted in a faster time to effective anaesthesia compared to CSE. However, these results are based on limited data and the difference is unlikely to be clinically meaningful. Consequently, there is currently insufficient evidence in support of one technique over the other and more evidence is needed in order to further evaluate the relative effectiveness and safety of CSE and spinal anaesthesia for caesarean section.More high-quality, sufficiently-powered studies in this area are needed. Such studies could consider using the outcomes listed in this review and should also consider reporting economic aspects of the different methods under investigation.

Echocardiographic determination of resting haemodynamics and optimal positioning in term pregnant women

Optimal positioning for anaesthesia in pregnant women involves balancing the need for ideal tracheal intubation conditions (achieved by the head elevated ramped position), with the prevention of reduced cardiac output from aortocaval compression (achieved by left lateral pelvic tilt). No studies have examined the effect on cardiac output of left lateral pelvic tilt in the ramped position. We studied non-labouring, non-anaesthetised healthy term pregnant women who underwent baseline (left lateral decubitus) cardiac assessment using transthoracic echocardiography. We then compared cardiac output, maternal physiological variables, fetal heart rate and comfort scores in three positions: left lateral decubitus; ramped position with wedge; and ramped position alone. Thirty women completed the study. Mean (SD) age, gestation and body mass index were 33.5 (3.93) years, 38.5 (0.94) weeks and 29.0 (4.0) kg.m^-2 , respectively. Mean ejection fraction, left ventricular internal diameter and mitral valve E/e' were 55.2 (6.8) %, 4.70 (0.43) cm and 7.50 (1.82), respectively. There were no differences in cardiac output between the positions (p = 0.503). There were no differences in systolic (p = 0.955) or diastolic (p = 0.987) blood pressure, maternal heart rate (p = 0.133), oxygen saturation, respiratory rate (p = 0.964) or fetal heart rate (p = 0.361) between ramped with wedge and ramped alone positions. Left lateral decubitus was most comfortable (p = 0.001), however, there were no differences in comfort levels between ramped with wedge and ramped alone positions. The ramped position without left lateral tilt is safe and acceptable in non-labouring, non-anaesthetised, healthy term pregnant women. Left lateral pelvic tilt may be unnecessary in the head elevated ramped position in term pregnant women.

Baby-directed umbilical cord clamping: A feasibility study

INTRODUCTION

Over five percent of infants born worldwide will need help breathing after birth. Delayed cord clamping (DCC) has become the standard of care for vigorous infants. DCC in non-vigorous infants is uncommon because of logistical difficulties in providing effective resuscitation during DCC. In Baby-Directed Umbilical Cord Clamping (Baby-DUCC), the umbilical cord remains patent until the infant's lungs are exchanging gases. We conducted a feasibility study of the Baby-DUCC technique.

METHODS

We obtained antenatal consent from pregnant women to enroll infants born at ≥32 weeks. Vigorous infants received ≥2 min of DCC. If the infant received respiratory support, the umbilical cord was clamped ≥60 s after the colorimetric carbon dioxide detector turned yellow. Maternal uterotonic medication was administered after umbilical cord clamping. A paediatrician and researcher entered the sterile field to provide respiratory support during a cesarean birth. Maternal and infant outcomes in the delivery room and prior to hospital discharge were analysed.

RESULTS

Forty-four infants were enrolled, 23 delivered via cesarean section (8 unplanned) and 15 delivered vaginally (6 via instrumentation). Twelve infants were non-vigorous. ECG was the preferred method for recording HR. Two infants had a HR < 100 BPM. All HR values were >100 BPM by 80 s after birth. Median time to umbilical cord clamping was 150 and 138 s in vigorous and non-vigorous infants, respectively. Median maternal blood loss was 300 ml.

CONCLUSIONS

It is feasible to provide resuscitation to term and near-term infants during DCC, after both vaginal and cesarean births, clamping the umbilical cord only when the infant is physiologically ready.

Reducing Maternal Mortality in Papua New Guinea: Contextualizing Access to Safe Surgery and Anesthesia

Papua New Guinea has one of the world's highest maternal mortality rates with approximately 215 women dying per 100,000 live births. The sustainable development goals outline key priority areas for achieving a reduction in maternal mortality including a focus on universal health coverage with safe surgery and anesthesia for all pregnant women. This narrative review addresses the issue of reducing maternal mortality in Papua New Guinea by contextualizing the need for safe obstetric surgery and anesthesia within a structure of enabling environments at key times in a woman's life. The 3 pillars of enabling environments are as follows: a stable humanitarian government; a safe, secure, and clean environment; and a strong health system. Key times, and their associated specific issues, in a woman's life include prepregnancy, antenatal, birth and the postpartum period, childhood, adolescence and young womanhood, and the postchildbearing years.

Doppler Assessment of Uterine Blood Flow in Pre-eclampsia: A Review

Doppler ultrasonography plays an ever-increasing role in obstetric imaging. Although commonly purported to assess blood flow, most studies in this area report purely on velocimetric parameters, rather than true volumetric flow. This review article highlights the physiological importance of this distinction, and reports on a literature review of uterine artery Doppler interrogation in the context of pre-eclampsia, which identified only four original research papers that attempted to assess blood flow. Attention is needed for true volumetric flow assessment in pre-eclampsia research, which may permit a more complete conceptualisation of the pathogenesis and haemodynamic consequences of this condition.

New diagnosis myasthenia gravis and preeclampsia in late pregnancy

Myasthenia gravis is a chronic autoimmune disease of neuromuscular transmission resulting in fatigable skeletal muscle weakness. Preeclampsia is a multisystem disease of pregnancy which is characterised by hypertension and involvement of one or more organ systems. Both diseases are responsible for considerable morbidity and mortality for mother and fetus. The occurrence of both preeclampsia and myasthenia gravis in pregnancy is very rare, and conflicts arise when considering the optimal management of each disease.We present a case of a parturient who was newly diagnosed with both myasthenia gravis and preeclampsia in late pregnancy. Myasthenia treatment was started with prednisolone and pyridostigmine, and delivery was by caesarean section at 37 weeks gestation under spinal anaesthesia. Postnatally, the patient developed worsening of myasthenia and preeclampsia symptoms. We consider the anaesthetic implications for both diseases and describe our approach for the management of this case.

Blood pressure assessment and first-line pharmacological agents in women with eclampsia

BACKGROUND

Eclampsia is a life-threatening complication of pregnancy. Timely blood pressure assessment and administration of magnesium sulphate are essential management. In this retrospective single-centre study we examined the timing and magnitude of maternal blood pressure before eclampsia, and whether magnesium sulphate was administered as the first agent for treatment.

METHODS

We conducted a five-year review of eclampsia in a tertiary referral obstetric hospital. Using data from electronic birthing records and hospital coding (ICD-10AM) we identified patients with the diagnostic criteria for eclampsia and assessed patient characteristics, blood pressure and pharmacological treatment.

RESULTS

There were 33812 births from July 2008 to June 2013 with 19 cases of eclampsia (1:1780). Patients were 32±5.9years of age, 36±3.9weeks of gestation, 63% were nulliparous and all had a singleton pregnancy. Antepartum eclampsia occurred in 74%. In the four hours before a fit, 47% of patients had blood pressure recorded, of whom 78% were hypertensive. Magnesium sulphate was administered as first therapy in 47% of patients but it was not given to any patient transferred to hospital by ambulance. Of the patients who fitted antenatally, 86% underwent caesarean section, of whom 25% received neuraxial anaesthesia.

CONCLUSIONS

Our study highlights the need for vigilance when managing pregnant women with hypertension, especially in the third trimester as eclampsia is most likely preceded by raised blood pressure. It also highlights the need for timely commencement of magnesium sulphate in the community and during transfer to hospital for the treatment of eclampsia, and for prevention of eclampsia in hospital when thresholds for severe preeclampsia are met.

Management of labour and delivery in a woman with refractory supraventricular tachycardia

Supraventricular tachycardia is uncommon in pregnancy. It is defined as intermittent pathological and usually narrow complex tachycardia >120 beats/min which originates above the ventricle, excluding atrial fibrillation, flutter and multifocal atrial tachycardia. It is usually self-limiting or relatively easily treated with most cases responding to physical or pharmacological therapies. We describe a case of a woman in the third trimester of pregnancy who developed treatment-resistant supraventricular tachycardia and required induction of labour and delivery to stop the arrhythmia. A multidisciplinary team approach with a critical care trained nurse and a midwife, continuous arterial blood pressure monitoring, transthoracic echocardiography, and neuraxial analgesia facilitated safe birth in the delivery suite and termination of the arrhythmia.

Combined spinal-epidural versus epidural analgesia in labour

BACKGROUND

Traditional epidural techniques have been associated with prolonged labour, use of oxytocin augmentation and increased incidence of instrumental vaginal delivery. The combined spinal-epidural (CSE) technique has been introduced in an attempt to reduce these adverse effects. CSE is believed to improve maternal mobility during labour and provide more rapid onset of analgesia than epidural analgesia, which could contribute to increased maternal satisfaction.

OBJECTIVES

To assess the relative effects of CSE versus epidural analgesia during labour.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (28 September 2011) and reference lists of retrieved studies. We updated the search on 30 June 2012 and added the results to the awaiting classification section.

SELECTION CRITERIA

All published randomised controlled trials (RCTs) involving a comparison of CSE with epidural analgesia initiated for women in the first stage of labour. Cluster-randomised trials were considered for inclusion. Quasi RCTs and cross-over trials were not considered for inclusion in this review.

DATA COLLECTION AND ANALYSIS

Three review authors independently assessed the trials identified from the searches for inclusion, assessed trial quality and extracted the data. Data were checked for accuracy.

MAIN RESULTS

Twenty-seven trials involving 3274 women met our inclusion criteria. Twenty-six outcomes in two sets of comparisons involving CSE versus traditional epidurals and CSE versus low-dose epidural techniques were analysed.Of the CSE versus traditional epidural analyses five outcomes showed a significant difference. CSE was more favourable in relation to speed of onset of analgesia from time of injection (mean difference (MD) -2.87 minutes; 95% confidence interval (CI) -5.07 to -0.67; two trials, 129 women); the need for rescue analgesia (risk ratio (RR) 0.31; 95% CI 0.14 to 0.70; one trial, 42 women); urinary retention (RR 0.86; 95% CI 0.79 to 0.95; one trial, 704 women); and rate of instrumental delivery (RR 0.81; 95% CI 0.67 to 0.97; six trials, 1015 women). Traditional epidural was more favourable in relation to umbilical venous pH (MD -0.03; 95% CI -0.06 to -0.00; one trial, 55 women). There were no data on maternal satisfaction, blood patch for post dural puncture headache, respiratory depression, umbilical cord pH, rare neurological complications, analgesia for caesarean section after analgesic intervention or any economic/use of resources outcomes for this comparison. No differences between CSE and traditional epidural were identified for mobilisation in labour, the need for labour augmentation, the rate of caesarean birth, incidence of post dural puncture headache, maternal hypotension, neonatal Apgar scores or umbilical arterial pH.For CSE versus low-dose epidurals, three outcomes were statistically significant. Two of these reflected a faster onset of effective analgesia from time of injection with CSE and the third was of more pruritus with CSE compared to low-dose epidural (average RR 1.80; 95% CI 1.22 to 2.65; 11 trials, 959 women; random-effects, T² = 0.26, I² = 84%). There was no significant difference in maternal satisfaction (average RR 1.01; 95% CI 0.98 to 1.05; seven trials, 520 women; random-effects, T² = 0.00, I² = 45%). There were no data on respiratory depression, maternal sedation or the need for labour augmentation. No differences between CSE and low-dose epidural were identified for need for rescue analgesia, mobilisation in labour, incidence of post dural puncture headache, known dural tap, blood patch for post dural headache, urinary retention, nausea/vomiting, hypotension, headache, the need for labour augmentation, mode of delivery, umbilical pH, Apgar score or admissions to the neonatal unit.

AUTHORS' CONCLUSIONS

There appears to be little basis for offering CSE over epidurals in labour, with no difference in overall maternal satisfaction despite a slightly faster onset with CSE and conversely less pruritus with low-dose epidurals. There was no difference in ability to mobilise, maternal hypotension, rate of caesarean birth or neonatal outcome. However, the significantly higher incidence of urinary retention, rescue interventions and instrumental deliveries with traditional techniques would favour the use of low-dose epidurals. It is not possible to draw any meaningful conclusions regarding rare complications such as nerve injury and meningitis.

Haemodynamics using transthoracic echocardiography in healthy pregnant and non-pregnant baboons (Papio hamadryas)

BACKGROUND

To determine systolic and diastolic function using transthoracic echocardiography in the baboon (Papio hamadryas).

METHODS

Transthoracic echocardiography was performed in eight non-pregnant female and six pregnant baboons according to American Society of Echocardiography recommendations.

RESULTS

Haemodynamic measurements were obtained from fourteen baboons. Compared to non-pregnant baboons, pregnant baboons demonstrated: (mean ± SD, pregnant vs. healthy) increased cardiac output (1615 ± 121 ml/minutes vs. 1317 ± 134 ml/minutes P = 0.001) due to an increased heart rate [120 ± 11 beats per minute (BPM) vs. 105 ± 6 BPM P = 0.018]. The inter-observer and intra-observer variability (mean difference ± SD) for the left ventricular outflow tract diameter was 0.05 ± 0.07 cm and 0.01 ± 0.03 cm respectively. There was minimal impact to the animal's daily activities.

CONCLUSIONS

Transthoracic echocardiography was applicable and reproducible for the assessment of haemodynamics in baboons thus enabling translation of animal results to human studies.

Combined spinal-epidural versus epidural analgesia in labour

BACKGROUND

Traditional epidural techniques have been associated with prolonged labour, use of oxytocin augmentation, and increased incidence of instrumental vaginal delivery. The combined spinal-epidural (CSE) technique has been introduced in an attempt to reduce these adverse effects. CSE is believed to improve maternal mobility during labour and provide more rapid onset of analgesia than epidural analgesia, which could contribute to increased maternal satisfaction.

OBJECTIVES

To assess the relative effects of CSE versus epidural analgesia during labour.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (December 2006).

SELECTION CRITERIA

All published randomised controlled trials involving a comparison of CSE with epidural analgesia initiated for women in the first stage of labour.

DATA COLLECTION AND ANALYSIS

Three review authors independently assessed the trials identified from the searches for inclusion and extracted the data.

MAIN RESULTS

Nineteen trials (2658 women) met our inclusion criteria. Twenty-six outcomes in two sets of comparisons involving CSE versus traditional epidurals and CSE versus low-dose epidural techniques were analysed. Of the CSE versus traditional epidural analyses only three outcomes showed a difference. CSE was more favourable in relation to need for rescue analgesia and urinary retention, but associated with more pruritus. For CSE versus low-dose epidurals, four outcomes were statistically significant. CSE had a faster onset of effective analgesia from time of injection but was associated with more pruritus. CSE was also associated with a clinically non-significant lower umbilical arterial pH. No differences between CSE and epidural were seen for maternal satisfaction, mobilisation in labour, modes of birth, incidence of post dural puncture headache or blood patch and maternal hypotension. It was not possible to draw any conclusions with respect to maternal respiratory depression, maternal sedation and need for labour augmentation.

AUTHORS' CONCLUSIONS

There appears to be little basis for offering CSE over epidurals in labour with no difference in overall maternal satisfaction despite a slightly faster onset with CSE and less pruritus with epidurals. There is no difference in ability to mobilise, obstetric outcome or neonatal outcome. However, the significantly higher incidence of urinary retention and rescue interventions with traditional techniques would favour the use of low-dose epidurals. It is not possible to draw any meaningful conclusions regarding rare complications such as nerve injury and meningitis.

Mechanisms of I(Ks) suppression in LQT1 mutants

Mutations in the cardiac potassium ion channel gene KCNQ1 (voltage-gated K(+) channel subtype KvLQT1) cause LQT1, the most common type of hereditary long Q-T syndrome. KvLQT1 mutations prolong Q-T by reducing the repolarizing cardiac current [slow delayed rectifier K(+) current (I(Ks) )], but, for reasons that are not well understood, the clinical phenotypes may vary considerably even for carriers of the same mutation, perhaps explaining the mode of inheritance. At present, only currents expressed by LQT1 mutants have been studied, and it is unknown whether abnormal subunits are transported to the cell surface. Here, we have examined for the first time trafficking of KvLQT1 mutations and correlated the results with the I(Ks) currents that were expressed. Two missense mutations, S225L and A300T, produced abnormal currents, and two others, Y281C and Y315C, produced no currents. However, all four KvLQT1 mutations were detected at the cell surface. S225L, Y281C, and Y315C produced dominant negative effects on wild-type I(Ks) current, whereas the mutant with the mildest dysfunction, A300T, did not. We examined trafficking of a severe insertion deletion mutant Delta544 and detected this protein at the cell surface as well. We compared the cellular and clinical phenotypes and found a poor correlation for the severely dysfunctional mutations.

Retention in the endoplasmic reticulum as a mechanism of dominant-negative current suppression in human long QT syndrome

Mutations in the cardiac potassium channel HERG (KCNH2) cause chromosome 7-linked long QT syndrome (LQT2) characterized by a prolonged QT interval, recurrent syncope and sudden cardiac death. Most mutations in HERG exhibit "loss of function" phenotypes with defective channels either inserted into the plasma membrane or retained in the endoplasmic reticulum. "Loss of function" mutations reduce I(Kr), the cardiac delayed rectifier current encoded by HERG, due to haploinsufficiency or suppression of wild-type function by a dominant-negative mechanism. One explanation for dominant-negative current suppression is that mutant subunits render tetrameric channel complexes non-conducting on co-assembly. In the present paper we describe an alternative mechanism for this phenomenon. We show (1) that the dominant-negative HERG mutation A561V is retained in the endoplasmic reticulum and (2) that wild-type channels are tagged for retention in the ER by co-assembly with trafficking deficient A561V subunits. Thus, in HERG A561V dominant-negative suppression of wild-type function is the result of an acquired trafficking defect.

Novel characteristics of a misprocessed mutant HERG channel linked to hereditary long QT syndrome

Hereditary long QT syndrome (hLQTS) is a heterogeneous genetic disease characterized by prolonged QT interval in the electrocardiogram, recurrent syncope, and sudden cardiac death. Mutations in the cardiac potassium channel HERG (KCNH2) are the second most common form of hLQTS and reduce the delayed rectifier K(+) currents, thereby prolonging repolarization. We studied a novel COOH-terminal missense mutation, HERG R752W, which segregated with the disease in a family of 101 genotyped individuals. When the mutant cRNA was expressed in Xenopus oocytes it produced enhanced rather than reduced currents. Simulations using the Luo-Rudy model predicted minimal shortening rather than prolongation of the cardiac action potential. Consequently, a normal or shortened QT interval would be expected in contrast to the long QT observed clinically. This anomaly was resolved by our observation that the mutant protein was not delivered to the plasma membrane of mammalian cells but was retained intracellularly. We found that this trafficking defect was corrected at lower incubation temperatures and that functional channels were now delivered to the plasma membrane. However, trafficking could not be restored by chemical chaperones or E-4031, a specific blocker of HERG channels. Therefore, HERG R752W represents a new class of trafficking mutants in hLQTS. The occurrence of different classes of misprocessed channels suggests that a unified therapeutic approach for altering HERG trafficking will not be possible and that different treatment modalities will have to be matched to the different classes of trafficking mutants.

Cellular dysfunction of LQT5-minK mutants: abnormalities of IKs, IKr and trafficking in long QT syndrome

Mutations in the minK gene KCNE1 have been linked to the LQT5 variant of human long QT syndrome. MinK assembles with KvLQT1 to produce the slow delayed rectifier K+ current IKs and may assemble with HERG to modulate the rapid delayed rectifier IKr. We used electrophysiological and immunocytochemical methods to compare the cellular phenotypes of wild-type minK and four LQT5 mutants co-expressed with KvLQT1 in Xenopus oocytes and HERG in HEK293 cells. We found that three mutants, V47F, W87R and D76N, were expressed at the cell surface, while one mutant, L51H, was not. Co-expression of V47F and W87R with KvLQT1 produced IKs currents having altered gating and reduced amplitudes compared with WT-minK, co-expression with L51H produced KvLQT1 current rather than IKs and co-expression with D76N suppressed KvLQT1 current. V47F increased HERG current but to a lesser extent than WT-minK, while L51H and W87R had no effect and D76N suppressed HERG current markedly. Thus, V47F interacts with both KvLQT1 and HERG, W87R interacts functionally with KvLQT1 but not with HERG, D76N suppresses both KvLQT1 and HERG, and L51H is processed improperly and interacts with neither channel. We conclude that minK is a co-factor in the expression of both IKs and IKr and propose that clinical manifestations of LQT5 may be complicated by differing effects of minK mutations on KvLQT1 and HERG.