Ability of radial arterial palpation and observation of the pulse oximetry trace to estimate non-invasive systolic pressure in healthy volunteers and in women undergoing spinal anaesthesia for elective caesarean section*

Color Doppler Ultrasonography for the Evaluation of Subclavian Artery Stenosis

Background

It is of great significance to evaluate symptomatic subclavian artery (SA) stenosis by color Doppler ultrasonography. More than 50% SA stenosis may induce symptoms. Currently, there is a paucity of published literature and lack of practitioner consensus for how ultrasonic findings should be interpreted in patients with SA stenosis.

Objective

The study aimed to prospectively evaluate SA stenosis using color Doppler ultrasonography, with digital subtraction angiography as a reference. Moreover, we aimed to determine the optimal thresholds to predict SA stenosis (≥50%).

Methods

A total of 423 SAs from 234 patients with normal or stenotic lumen were enrolled. The peak systolic velocity (PSV) and acceleration time at the stenotic and distal segments of the SA, peak reversed velocity of the vertebral artery, and waveforms of the stenotic SA, distal SA, and vertebral artery were recorded. The ratios of stenotic PSV to distal PSV (PSVr) and distal AT to stenotic AT were also calculated. The optimal cutoff values were determined using receiver operating characteristic analysis.

Results

All ultrasonic parameters were significantly correlated with the degree of SA stenosis, whereas PSV (r = 0.624, P < 0.001), PSVr (r = 0.654, P < 0.001) and VA waveform change (r = 0.631, P < 0.001) had the strongest correlation with SA stenosis. The optimal cutoff values were as follows: PSV ≥ 230 cm/s and PSVr ≥ 2.2 to predict ≥ 50% stenosis, and PSV ≥ 340 cm/s and PSVr ≥ 3.0 to predict ≥ 70% stenosis.

Conclusions

Symptomatic patients with the ultrasonic parameters of PSV ≥ 230 cm/s and PSVr ≥ 2.2 need to be considered for further verification by computed tomographic angiography or magnetic resonance angiography, or by digital subtraction angiography with a view to percutaneous transluminal angioplasty/stent implantation in the same session. The recommended graded cutoff values can help in long-term management of patients with SA stenosis.

Lack of controlled studies investigating the risk of postpartum haemorrhage in cesarean delivery after prior use of oxytocin: a scoping review

BACKGROUND

Postpartum haemorrhage (PPH) is a major cause of maternal mortality and morbidity worldwide. Experimental and clinical studies indicate that prolonged oxytocin exposure in the first or second stage of labour may be associated with impaired uterine contractility and an increased risk of atonic PPH. Therefore, particularly labouring women requiring cesarean delivery constitute a subset of patients that may exhibit an unpredictable response to oxytocin. We mapped the evidence for comparative studies investigating the hypothesis whether the risk for PPH is increased in women requiring cesarean section after induction or augmentation of labour.

METHODS

We performed a systematic literature search for clinical trials in Medline, Embase, Web of Science, and the Cochrane Library (May 2016). Additionally we searched for ongoing or unpublished trials in clinicaltrials.gov and the WHO registry platform. We identified a total of 36 controlled trials investigating the exogenous use of oxytocin in cesarean section. Data were extracted for study key characteristics and the current literature literature was described narratively.

RESULTS

Our evidence map shows that the majority of studies investigating the outcome PPH focused on prophylactic oxytocin use compared to other uterotonic agents in the third stage of labour. Only 2 dose-response studies investigated the required oxytocin dose to prevent uterine atony after cesarean delivery for labour arrest. These studies support the hypotheses that labouring women exposed to exogenous oxytocin require a higher oxytocin dose after delivery than non-labouring women to prevent uterine atony after cesarean section. However, the study findings are flawed by limitations of the study design as well as the outcome selection. No clinical trial was identified that directly compared exogenous oxytocin versus no oxytocin application before intrapartum cesarean delivery.

CONCLUSION

Despite some evidence from dose-response studies that the use of oxytocin may increase the risk for PPH in intrapartum cesarean delivery, current research has not investigated the prepartal application of oxytocin in well controlled clinical trials. It was striking that most studies on exogenous oxytocin are focused on PPH prophylaxis in the third stage of labour without differing between the indications of cesarean section and hence the prepartal oxytocin status.

Ability of non-invasive intermittent blood pressure monitoring and a continuous non-invasive arterial pressure monitor (CNAP™) to provide new readings in each 1-min interval during elective caesarean section under spinal anaesthesia

We compared the ability of automated non-invasive intermittent oscillometric blood pressure monitoring with a new device, CNAP(TM) (continuous non-invasive arterial pressure) to provide a new blood pressure reading in each 1-min interval between spinal anaesthesia and delivery during caesarean section. We also compared the accuracy of continuous non-invasive arterial pressure readings with non-invasive blood pressure measurements before spinal anaesthesia. Fifty-nine women participated. The non-invasive and continuous non-invasive monitors displayed new blood pressure readings in a mean of 82% (11%) and 83% (13%) (p = 0.97) of the one-minute intervals between spinal anaesthesia and delivery, respectively. Continuous non-invasive arterial pressure was more likely to fail on two or more consecutive minutes (p=0.001). From the pre-spinal readings, the mean bias, defined as non-invasive-continuous non-invasive arterial pressure, and limits of agreement (±2SD mean bias) for systolic, diastolic and mean blood pressure respectively were +1.3 (±26.0), -2.9 (±21.8) and +2.6 (±20.4) mmHg. The new monitor has disadvantages compared with conventional non-invasive intermittent blood pressure monitoring.