Complications of obstetric epidural analgesia and anaesthesia: a prospective analysis of 10 995 cases

Total spinal anaesthesia following obstetric neuraxial blockade: a narrative review

BACKGROUND

Total spinal anaesthesia (TSA) is an emergency caused by high neuraxial blockade. It is a recognised complication of all neuraxial techniques in obstetric anaesthesia. Its incidence and outcomes have not been evaluated. There is compelling evidence that TSA continues to be a problem in contemporary practice, having the capacity to cause significant morbidity and mortality if not recognised early and promptly treated. This review based on a literature search aims to clarify the epidemiology of TSA, summarise its pathophysiology, and identify risk factors and effective treatments.

METHODS

We performed a literature search using PubMed, Web of Science and Google Scholar databases using specified search terms for materials published using search terms. For each case, the type of block, the difficulty of the procedure, the dose of local anaesthetic, positivity of aspiration before and after the event, maternal outcome, Apgar score, onset of symptoms, cardiorespiratory and neurological manifestations, cardiorespiratory support employed, admission to an intensive care unit, cardiac arrest events and duration of mechanical ventilation were extracted.

RESULTS

A total of 605 cases were identified, of which 51 were sufficiently detailed for analysis. Although TSA is described after all neuraxial techniques, spinal after epidural was a particular concern in recent reports. Respiratory distress was universal but apnoea was not. The onset of apnoea was variable, ranging from 1 to 180 min. Hypotension was not invariable and occurred in approximately half of cases. Multiple fatalities and neurological injuries were reported, often in under-resourced areas when providers were not skilled in airway management or when recognition and intervention were delayed. In the most recent reports good outcomes were achieved when effective treatments were rapidly provided.

CONCLUSIONS

The available literature confirms that TSA remains an active clinical problem and that with prompt recognition and treatment good outcomes can be achieved. This requires anticipation and preparedness in all clinical areas where neuraxial techniques are performed.

A randomized double-blinded study assessing the dose-response of ropivacaine with dexmedetomidine for maintenance of labor with epidural analgesia in nulliparous parturients

Background: The combination of ropivacaine and dexmedetomidine has been used as an epidural analgesic for inducing labor. However, there is limited data regarding the administration of epidural analgesia for labor maintenance, hence, this study aimed to determine the optimum concentration through dose-response curves of ropivacaine plus dexmedetomidine, which could be used along with the Programmed Intermittent Epidural Bolus (PIEB) technique. Methods: One hundred parturients were randomized into 4 groups who were administered four different doses of ropivacaine (dexmedetomidine at 0.4 μg mL-1): 0.04%, 0.06%, 0.08%, and 0.1%. The primary outcome that was determined included the proportion of patients experiencing breakthrough pain during their 1st stage of labor. Breakthrough pain was described as a visual analog scale [VAS] score of >30 mm, requiring supplemental epidural analgesia after the administration of at least one patient-controlled bolus. The effective concentration of analgesia that was used for labor maintenance in 50% (EC50) and 90% (EC90) of patients were calculated with the help of probit regression. Secondary outcomes included epidural block characteristics, side effects, neonatal outcomes, and patient satisfaction. Results: The results indicated that the proportion of patients without breakthrough pain was 45% (10/22), 55% (12/22), 67% (16/24), and 87% (20/23) for 0.04%, 0.06%, 0.08%, and 0.10% doses of the analgesic that were administered, respectively. The EC50 value was 0.051% (95% confidence interval [CI], 0.011%-0.065%) while the EC90 value was recorded to be 0.117% (95% CI, 0.094%-0.212%). Side effects were similar among groups. Conclusion: A ropivacaine dose of 0.117% can be used as epidural analgesia for maintaining the 1st stage of labor when it was combined with dexmedetomidine (0.4 μg mL-1) and the PIEB technique. Clinical Trial Register: https://www.chictr.org.cn/index.aspx, identifier ChiCTR2200059557.

Bibliometric Analysis of Research Studies on Postoperative Pain Management of Cesarean Section

Purpose

Cesarean section (C-section) is associated with moderate-to-severe postoperative pain. Many studies on pain management after C-section have been published in recent decades, many of which focused on new regional techniques. The purpose of this study is to outline the connections within the dynamic evolution of postcesarean delivery analgesia research publications using retrospective bibliometric analysis.

Patients and Methods

Published studies on postoperative pain management of C-section were retrieved from the Science Citation Index Expanded (SCI-E) of Web of Science (WOS) Core collection database. All papers published from 1978 to October 22, 2022 were searched. The research progress and growing trend were quantitatively analyzed by total publications, research institutions, journal impact factors, and author's contribution. Total citations frequency, average citations per item and h-index were used for evaluating literature quantity. Top 20 journals with the highest number of publications were charted. The keywords co-occurrence overlay map was visualized by the VOSviewer software.

Results

From 1978 to 2022, a total of 1032 articles in postcesarean delivery analgesia research field were published, with 23,813 times cited, average citations of 23.07 per item, and an h-index of 68. The most high-yield publication year, countries, journals, authors, institutions were 2020 (n=79), the United States (n=288), Anesthesia and Analgesia (n=108), Carvalho B (n=25), and Stanford University (n=33), respectively. The United States had the most cited papers. The future research interest might be "prescription", "quadratus lumborum block", "postnatal depression", "persistent pain", "dexmedetomidine", "enhanced recovery", and "multimodal analgesia".

Conclusion

By employing the online bibliometric tool and VOSviewer software, we found that studies on postcesarean analgesia had grown markedly. The focus had evolved to nerve block, postnatal depression, persistent pain, and enhanced recovery.

Risk factors for labor epidural conversion failure requiring general anesthesia for cesarean delivery

Background and Aims:

To evaluate the rate and risk factors of labor epidural conversion failure requiring general anesthesia for Caesarean delivery (CD).

Material and Methods:

Pregnant patients requiring conversion from labor to CD with a pre-existing labor epidural at our institution from 2009 to 2014 were identified. Through a retrospective review, we compared successful epidural conversion with those who required general anesthesia for CD. Patient characteristics were analyzed to identify risk factors for failed epidural conversion for CD.

Results:

A total of 673 patients were included in the study. The rate of epidural conversion failure was 21%. Main risk factors for epidural conversion failure requiring general anesthesia included: younger maternal age (95% CI 0.94, P = 0.0002) and supplementation of intravenous fentanyl (95% CI 0.19, P < 0.0001) or midazolam (95% CI 0.26, P = 0.0008) during CD. A higher risk of conversion failure was also associated with a more urgent CD (CD category 1, 2, and 3 vs category 4).

Conclusion:

Consistent with previous reports, young age and the urgency of CD increases the likelihood of epidural conversion failure. While conversion failure is likely multifactorial and complex, many of these factors are suggestive of inadequate and poorly functioning labor epidurals prior to CD. Prospective studies to further evaluate these factors are necessary, and the best prevention of epidural conversion failure is diligent diagnosis and evaluation of ineffective labor epidural analgesia prior to impending CD.

Machine learning approach to needle insertion site identification for spinal anesthesia in obese patients

Background

Ultrasonography for neuraxial anesthesia is increasingly being used to identify spinal structures and the identification of correct point of needle insertion to improve procedural success, in particular in obesity. We developed an ultrasound-guided automated spinal landmark identification program to assist anesthetists on spinal needle insertion point with a graphical user interface for spinal anesthesia.

Methods

Forty-eight obese patients requiring spinal anesthesia for Cesarean section were recruited in this prospective cohort study. We utilized a developed machine learning algorithm to determine the needle insertion point using automated spinal landmark ultrasound imaging of the lumbar spine identifying the L3/4 interspinous space (longitudinal view) and the posterior complex of dura mater (transverse view). The demographic and clinical characteristics were also recorded.

Results

The first attempt success rate for spinal anesthesia was 79.1% (38/48) (95%CI 65.0 - 89.5%), followed by successful second attempt of 12.5% (6/48), third attempt of 4.2% (2/48) and 4th attempt (4.2% or 2/48). The scanning duration of L3/4 interspinous space and the posterior complex were 21.0 [IQR: 17.0, 32.0] secs and 11.0 [IQR: 5.0, 22.0] secs respectively. There is good correlation between the program recorded depth of the skin to posterior complex and clinician measured depth (r = 0.915).

Conclusions

The automated spinal landmark identification program is able to provide assistance to needle insertion point identification in obese patients. There is good correlation between program recorded and clinician measured depth of the skin to posterior complex of dura mater. Future research may involve imaging algorithm improvement to assist with needle insertion guidance during neuraxial anesthesia.

Trial registration

This study was registered on clinicaltrials.gov registry (NCT03687411) on 22 Aug 2018.

Anesthesia-related adverse events in obstetric patients: a population-based study in Canada

BACKGROUND

Anesthesia-related complications in obstetric patients could be catastrophic and impact the lives of both the parturient and the neonate. The objective of this study was to determine the frequency, temporal trend, and risk factors of anesthesia-related adverse events during hospitalization for delivery in Canada.

METHODS

This retrospective population-based study utilized the hospitalization database of the Canadian Institute for Health Information for all parturients (gestation ≥ 20 weeks) in Canada (except Quebec) hospitalized for childbirth from April 2004 to March 2017. Complications were identified by the enhanced Canadian version of the tenth revision of the International Statistical Classification of Diseases and Related Health Problems codes. Data were summarized with descriptive statistics. Associations between hospitalizations with an anesthesia-related adverse event and patient characteristics, delivery method, and modality of anesthesia were assessed using multivariate logistic regression.

RESULTS

Among 2,601,034 hospitalizations (3,194,875 interventions), 8,361 anesthesia-related adverse events occurred over a 13-year period (262 per 100,000 interventions; 95% confidence interval [CI], 256 to 267), with a significant decline over time (P < 0.001). These were two-fold and seven-fold higher per 100,000 interventions with general (488; 95% CI, 438 to 542) and general plus neuraxial (1,476; 95% CI, 1,284 to 1,689) anesthesia compared with neuraxial anesthesia alone (225; 95% CI, 219 to 230). Serious adverse events constituted 9% of all adverse events. The most common adverse event was spinal and epidural anesthesia-induced headache (6,908/8,361; 83%); the overall rate of failed or difficult intubations was low (201/8,361; 2%). Anesthesia-related events were more likely in those who had a Cesarean delivery compared with vaginal delivery (odds ratio [OR], 1.12; 95% CI, 1.06 to 1.18) and general anesthesia compared with neuraxial anesthesia (OR, 1.71; 95% CI, 1.53 to 1.93). Noteworthy associations were found between any anesthesia-related adverse events and cardiomyopathy (OR, 8.34; 95% CI, 2.59 to 26.83), eclampsia (OR, 3.11; 95% CI, 1.95 to 4.97), and obstructive sleep apnea (OR, 1.91; 95% CI, 1.66 to 2.19).

CONCLUSION

The incidence of anesthesia-related adverse events in obstetric patients in Canada is low and declining. High vigilance is required in parturients undergoing Cesarean delivery, receiving general anesthesia, and those with pre-existing medical conditions.

Delivery and neuraxial technique outcomes in patients with hemophilia and in hemophilia carriers: a systematic review

Female carriers are more common than males with hemophilia and unrecognized factor VIII or IX deficiency is associated with intrauterine growth retardation, epidural hematomas, blood transfusion, and peripartum hemorrhage. A review was conducted to assess the evidence for professional society recommendations for > 50% factor levels during labor. Two searches of Pubmed, CINAHL, Cochrane, and Google Scholar were completed in October 2019. The first for case reports and series described neuraxial techniques in patients with hemophilia-regardless of sex, age, or pregnant status. The second for case reports and series described bleeding outcomes of parturients with hemophilia. Primary outcomes were diagnosis of neuraxial hematoma (first search) and postpartum bleeding complications (second search). Thirteen articles (n = 134) described neuraxial techniques in patients with hemophilia. Neuraxial hematoma with paraplegia occurred in 3/134 patients-all had a factor level of 1%. Nineteen articles (2712 deliveries in 2657 women) described bleeding outcomes. Postpartum hemorrhage occurred in 7.1% (193/2712) of deliveries, of which 60% necessitated blood transfusion. Postpartum bleeding complications were twice as likely (51.0% [25/49] vs. 25.6% [52/203], P < 0.001) with factor activity < 50%. Therefore, factor levels should be assessed and increased above 50% prior to neuraxial technique and delivery.Trial registration: PROSPERO 2018 CRD42018110215.

The relationship between resited epidural catheters after secondary epidural catheter failure and vaginal delivery: A retrospective case-control study

BACKGROUND

There are cases where epidural analgesia is initially effective but subsequently fails and needs to be resited. We evaluated the rate of normal vaginal delivery and operative delivery among parturients who had resited epidurals compared to parturients with epidurals that were not resited.

METHODS

A retrospective electronic medical review of parturients with a singleton gestation attempting normal vaginal delivery under epidural analgesia between the years 2012-2016 was conducted. Resited epidurals were defined as epidurals that were considered effective but subsequently removed and reinserted. For each resited epidural, two previous and two consecutive deliveries of parturients with normally functioning epidural catheter inserted by the same anesthesiologist were matched controls (non-resited epidurals).

RESULTS

There were 35,984 attempted vaginal deliveries with 118 resited epidurals and 472 non-resited epidurals. When adjusted for nulliparity, oxytocin administration, sex and weight of the baby, and maternal BMI, labor epidural catheter replacement was not associated with need for instrumental or caesarean delivery, (OR 1.5, 95% CI 0.91-2.49, P = .11).

CONCLUSIONS

Need for labor epidural catheter replacement does not appear to be associated with need for operative delivery based on this single-centre cohort analysis.

The association between labour epidural case volume and the rate of accidental dural puncture

Accidental dural puncture is a recognised complication of labour epidural placement and can cause a debilitating headache. We examined the association between labour epidural case volume and accidental dural puncture rate in specialist anaesthetists and anaesthesia trainees. We performed a retrospective cohort study of labour epidural and combined spinal-epidural nerve blocks performed between 1 July 2013 and 31 December 2017 at Waitemata District Health Board, Auckland, New Zealand. The mean (SD) annual number of obstetric epidural and combined spinal-epidural procedures for high-case volume specialists was 44.2 (15.0), and for low-case volume specialists was 10.0 (6.8), after accounting for caesarean section combined spinal-epidural procedures. Analysis of 7976 labour epidural and combined spinal-epidural procedure records revealed a total of 92 accidental dural punctures (1.2%). The accidental dural puncture rate (95%CI) in high-case volume specialists was 0.6% (0.4-0.9%) and in low-case volume specialists 2.4% (1.4-3.9%), indicating probable skill decay. The odds of accidental dural puncture were 3.77 times higher for low- compared with high-case volume specialists (95%CI 1.72-8.28, p = 0.001). Amongst trainees, novices had a significantly higher accidental dural puncture complication rate (3.1%) compared with registrars (1.2%), OR (95%CI) 0.39 (0.18-0.84), p = 0.016, or fellows (1.1%), 0.35 (0.16-0.76), p = 0.008. Accidental dural puncture complication rates decreased once trainees progressed past the 'novice' training stage.

Characterization of tissue properties in epidural needle insertion on human specimen and synthetic materials

The force experienced while inserting an 18-gauge Tuohy needle into the epidural space or dura is one of only two feedback components perceived by an anaesthesiologist to deduce the needle tip position in a patient's spine. To the best of the authors knowledge, no x-ray validated measurements of these forces are currently available to the public. A needle insertion force recording during an automated insertion of an 18-gauge Tuohy needle into human vertebral segments of four female donors was conducted. During the measurements, x-ray images were recorded simultaneously. The force peaks due to the penetration of the ligamentum supraspinale and ligamentum flavum were measured and compared to the measurements of an artificial patient phantom for a hybrid patient simulator. Based on these force peaks and the slope of the ligamentum interspinale, a mathematical model was developed. The model parameters were used to compare human specimens and artificial patient phantom haptics. The force peaks for the ligamenta supraspinale and flavum were 7.55 ± 3.63 N and 15.18 ± 5.71 N, respectively. No significant differences were found between the patient phantom and the human specimens for the force peaks and four of six physical model parameters. The patient phantom mimics the same resistive force against the insertion of an 18-gauge Tuohy needle. However, there was a highly significant (p < 0.001, eff_size = 0.949 and p < 0.001, eff_size = 0.896) statistical difference observed in the insertion depth where the force peaks of the ligamenta supraspinale and flavum were detected between the measurements on the human specimens and the patient phantom. Within this work, biomechanical evidence was identified for the needle insertion force into human specimens. The comparison of the measured values of the human vertebral segments and the artificial patient phantom showed promising results.

Prediction of breakthrough pain during labour neuraxial analgesia: comparison of machine learning and multivariable regression approaches

INTRODUCTION

Risk-prediction models for breakthrough pain facilitate interventions to forestall inadequate labour analgesia, but limited work has used machine learning to identify predictive factors. We compared the performance of machine learning and regression techniques in identifying parturients at increased risk of breakthrough pain during labour epidural analgesia.

METHODS

A single-centre retrospective study involved parturients receiving patient-controlled epidural analgesia. The primary outcome was breakthrough pain. We randomly selected 80% of the cohort (training cohort) to develop three prediction models using random forest, XGBoost, and logistic regression, followed by validation against the remaining 20% of the cohort (validation cohort). Area-under-the-receiver operating characteristic curve (AUC), sensitivity, specificity, and positive and negative predictive values (PPV and NPV) were used to assess model performance.

RESULTS

Data from 20 716 parturients were analysed. The incidence of breakthrough pain was 14.2%. Of 31 candidate variables, random forest, XGBoost and logistic regression models included 30, 23, and 15 variables, respectively. Unintended venous puncture, post-neuraxial analgesia highest pain score, number of dinoprostone suppositories, neuraxial technique, number of neuraxial attempts, depth to epidural space, body mass index, pre-neuraxial analgesia oxytocin infusion rate, maternal age, pre-neuraxial analgesia cervical dilation, anaesthesiologist rank, and multiparity, were identified in all three models. All three models performed similarly, with AUC 0.763-0.772, sensitivity 67.0-69.4%, specificity 70.9-76.2%, PPV 28.3-31.8%, and NPV 93.3-93.5%.

CONCLUSIONS

Machine learning did not improve the prediction of breakthrough pain compared with multivariable regression. Larger population-wide studies are needed to improve predictive ability.

Feasibility of Using the Epidural Space Detecting Device (EPI-DetectionTM) for Interlaminar Cervical Epidural Injection

Cervical epidural injection (CEI), which is widely used for the treatment of cervical radiculopathy, sometimes has been associated with post-operative complications. Recently, EPI-Detection^TM, which detects the negative pressure of the epidural space and notifies the proceduralist by flashing a light and producing a beeping sound, was introduced. We assumed that the newly developed device could be as safe and efficient as the conventional loss of resistance (LOR) method. Therefore, we aimed to evaluate the effectiveness of the EPI-Detection^TM and compare it to that of the conventional LOR method. We randomly assigned 57 patients to the LOR and EPI-Detection groups (29 and 28 patients, respectively). Subjects were treated with interlaminar CEI (ILCEI) using one of two methods. The measured parameters, i.e., operation time and radiation dose were lower in the EPI-Detection^TM group (4.6 ± 1.2 min vs. 6.9 ± 2.1 min; and 223.2 ± 206.7 mGy·cm² vs. 380.3 ± 340.9 mGy·cm², respectively; all p < 0.05) than in the LOR group. There were no complications noted in either group. Both the EPI-Detection^TM and LOR methods were safe and effective in detecting the epidural space, but the former was superior to the latter in terms of operation time and radiation exposure. The EPI-Detection^TM may help perform ILCEI safely.

Epidural test dose in obstetric patients: should we still use it?

PURPOSE OF REVIEW

As the application of a test dose after epidural catheter insertion in obstetrics has recurrently been associated with serious adverse events affecting both maternal and foetal outcomes, the question whether to test or not remains a controversial issue.

RECENT FINDINGS

Present guidelines do not provide clear recommendations in this regard and several recent surveys indicate a heterogeneity in clinical routine.

SUMMARY

Physiological alterations during pregnancy and labour restrict the use and also the validity of traditional test agents. Epinephrine is not appropriate to detect a vascular insertion in labour and the application of a local anaesthetic test dose may lead to dose-dependent fatal consequences should the catheter be intrathecal, due to an increased sensitivity in parturients. Given the current practice of opioid-amended-low-concentration epidurals, the waiving of a test dose results at worst in a failed epidural, a stark contrast to the potentially severe to fatal complications of a 'traditional' test dose. Hence, an originally preventive measure providing potentially more harm than the consequences of the situation aimed to prevent, should not be recommended. A simple fractionated administration of the initial analgesic dose seems reasonable though.

Loss of resistance: A randomised controlled trial assessing four low-fidelity epidural puncture simulators

BACKGROUND

Detecting loss of resistance (LOR) can either be taught with dedicated simulators, with a cost ranging from &OV0556;1500 to 3000, or with the 'Greengrocer's Model', requiring simply a banana.

OBJECTIVES

The purpose of this study was to compare three dedicated epidural puncture training simulators and a banana in their ability to simulate LOR. Our hypothesis was that there was a difference between the four simulators when comparing the detection of LOR.

DESIGN

Single-blinded, randomised, controlled study.

SETTING

Department of Anaesthesiology and Pain Therapy, Bern University Hospital, Switzerland.

PARTICIPANTS

Fifty-five consultant anaesthesiologists.

INTERVENTIONS

The participants were asked to insert an epidural catheter in four different epidural puncture training simulators: Lumbar Puncture Simulator II (Kyoto Kagaku, Kyoto, Japan), Lumbar Epidural Injection Trainer (Erler-Zimmer, Lauf, Germany), Normal Adult Lumbar Puncture/Epidural Tissue (Simulab Corp., Seattle, Washington, USA) and a banana. The simulators were placed in identical boxes to blind the participants.

MAIN OUTCOME MEASURES

The primary outcome was the detection of LOR rated on a 100-mm visual analogue scale, in which 0 mm represented 'completely unrealistic' and 100 mm represented 'indistinguishable from a real patient'.

RESULTS

The mean visual analogue scale scores for LOR in the four simulators were significantly different: 60 ± 25 mm [95% confidence interval (CI), 55 to 65 mm], 50 ± 29 mm (95% CI, 44 to 55 mm), 64 ± 24 mm (95% CI, 58 to 69 mm) and 49 ± 32 mm (95% CI, 44 to 54 mm); P less than 0.001, Friedman test.

CONCLUSION

Two of the three dedicated epidural simulators were rated more realistic in detecting LOR than the banana, but some participants preferred the banana to the other three simulators. Given the relative cost of a banana compared with a dedicated simulator, we suggest that a banana be used to teach the technique of LOR for epidural puncture.

TRIAL REGISTRATION

KEK Nr: Req-2015-z087.

Bilateral Vocal Fold Paralysis After Epidural Anesthesia

Cranial neuropathies are known potential complications of spinal anesthesia, with most reports describing upper cranial nerve involvement. Intrathecal hypotension resulting in traction injury of the cranial nerves is the likely mechanism of injury. Unilateral vagal neuropathy was first described recently. The patient discussed in this case presented with hoarseness and dysphagia after receiving epidural anesthesia for childbirth. Following videostroboscopy and laryngeal electromyogram, she was diagnosed with bilateral vocal fold paralysis. The patient was managed conservatively with expectant management. She exhibited complete spontaneous recovery, as has been the natural history previously described for similar injuries. The proposed mechanism for this patient, and in others described in the literature, is puncture of the dura with subsequent egress of cerebrospinal fluid, leading to intracranial hypotension and traction on cranial nerves. Unilateral vocal fold paralysis following spinal anesthesia has been reported in one case series consisting of three patients, but this represents the first case of bilateral paralysis. Spontaneous resolution has been observed in all patients. Patients presenting with idiopathic vocal fold paralysis, in summary, should be questioned about recent history of epidural or spinal anesthesia, as a positive history may point to transient intrathecal hypotension as a potential etiology of the paralysis. 

The training environment of junior anaesthetic registrars learning epidural labour analgesia in Australian teaching hospitals

Junior anaesthetic registrars perform epidural labour analgesia in many Australian hospitals, however data evaluating training and outcomes are scarce. We aimed to describe and evaluate training practices and environments provided for registrars who learn epidural labour analgesia in their first year of training. Twenty-nine registrars audited their epidurals, participated in semi-structured interviews and completed surveys for six months. The median (interquartile range) number of epidurals performed by each registrar was 17 (15–25). Fifty percent performed less than 20. Among 216 audited cases, complications were reported in 19% (dural puncture in 1.4%) and technical difficulties in 16%. Direct supervision was provided for a median (range) of 2.5 (6) epidurals per registrar and for a significantly higher proportion of epidurals performed in tertiary hospitals compared with district metropolitan and rural hospitals (35%, 6% and 22% respectively; P=0.001). Registrars felt senior staff had supportive attitudes, however the onus for initiating supervision appeared to be with the registrars and responses to survey items addressing role clarity and access to supervision showed wide variation. Only 33% of registrars agreed that they received adequate training before their first epidural and 67% reported workplace stress. None received formal assessments designed to ensure adequate supervision and competency. These results suggest that current training practices for these trainees are inadequate and could be improved by audit and structured workplace learning and assessment activities. We have demonstrated the potential value of measuring a range of training outcomes and environmental factors and have provided baseline data for future research.

Development and validation of a predictive risk factor model for epidural re-siting in women undergoing labour epidural analgesia: a retrospective cohort study

Background

Epidural catheter re-siting in parturients receiving labour epidural analgesia is distressing to the parturient and places them at increased complications from a repeat procedure. The aim of this study was to develop and validate a clinical risk factor model to predict the incidence of epidural catheter re-siting in labour analgesia.

Methods

The data from parturients that received labour epidural analgesia in our centre during 2014–2015 was used to develop a predictive model for epidural catheter re-siting during labour analgesia. Multivariate logistic regression analysis was used to identify factors that were predictive of epidural catheter re-siting. The forward, backward and stepwise variable selection methods were applied to build a predictive model, which was internally validated. The final multivariate model was externally validated with the data collected from 10,170 parturients during 2012–2013 in our centre.

Results

Ninety-three (0.88%) parturients in 2014–2015 required re-siting of their epidural catheter. The training data set included 7439 paturients in 2014–2015. A higher incidence of breakthrough pain (OR = 4.42), increasing age (OR = 1.07), an increased pain score post-epidural catheter insertion (OR = 1.35) and problems such as inability to obtain cerebrospinal fluid in combined spinal epidural technique (OR = 2.06) and venous puncture (OR = 1.70) were found to be significantly predictive of epidural catheter re-siting, while spontaneous onset of labour (OR = 0.31) was found to be protective. The predictive model was validated internally on a further 3189 paturients from the data of 2014–2015 and externally on 10,170 paturients from the data of 2012–2013. Predictive accuracy of the model based on C-statistic were 0.89 (0.86, 0.93) and 0.92 (0.88, 0.97) for training and internal validation data respectively. Similarly, predictive accuracy in terms of C-statistic was 0.89 (0.86, 0.92) based on 2012–2013 data.

Conclusion

Our predictive model of epidural re-siting in parturients receiving labour epidural analgesia could provide timely identification of high-risk paturients required epidural re-siting.

Ultrasound guided L5-S1 placement of labor epidural does not improve dermatomal block in parturients

BACKGROUND

Based on their experience or training, anesthesiologists typically use the iliac crest as a landmark to choose the L3-4 or L2-3 interspace for labor epidural catheter placement. There is no evidence-based recommendation to guide the exact placement. We hypothesized that lower placement of the catheter would lead to a higher incidence of S2 dermatomal block and improved analgesia in late labor and at delivery.

METHODS

One-hundred parturients requesting epidural analgesia were randomly assigned to receive ultrasound-guided L5-S1 epidural catheter placement (experimental group) or non-ultrasound-guided higher lumbar interspace placement (control group). The primary outcome was the incidence of S2 block 30 minutes after administering 10 mL 0.125% bupivacaine. Secondary outcomes were average pain throughout labor and maximum pain during labor or during delivery.

RESULTS

Forty-nine subjects were enrolled in control group and 47 in the experimental group. The primary endpoint did not significantly differ between groups (control group 81% vs experimental group 91%, P=0.24). The secondary endpoints were not significantly different: pain relief after 30 minutes (mean pain score 1.4 in the control group vs 1.9 in the experimental group, P=0.2) and pain at delivery (mean score 4 in the control group vs 3.9 in the experimental group, P=0.6).

CONCLUSION

Placement of an epidural catheter at the L5-S1 interspace using ultrasound did not improve sacral sensory block coverage when compared with an epidural catheter placed at a higher lumbar interspace, without using ultrasound guidance.

Gabor-based automatic spinal level identification in ultrasound

This paper presents an automatic lumbar spine level identification system based on image processing of ultrasound images. The goal is to aid anesthetists in identifying the correct spinal level during epidural anesthesia. Spine level identification is initiated by detecting the location of the sacrum using a classifier based on a support vector machine. Image stitching is then conducted to produce a panorama image of the spinal area. During this process, the location of spinal processes are enhanced using a Gabor filter and detected through template matching. The locations of the spinal processes are tracked and used as an overlay on the ultrasound image in real-time. The system then informs the anesthetists when the correct spinal level has been reached. The system was evaluated on forty volunteers by two anesthetists with varying experience level and was able to detect the correct position of the L3-L4 spinal level in all of the volunteers. The average time taken to produce the location of the L3-L4 spinal level was 30.92 seconds. The results show that the system can quickly and accurately detect the location of the target spinal level.

A hybrid, low-cost tissue-like epidural needle insertion simulator

Epidural and spinal anesthesia are mostly performed "blind" without any medical imaging. Currently, training of these procedures is performed on human specimens, virtual reality systems, manikins and mostly in clinical practice supervised by a professional. In this study a novel hybrid, low-cost patient simulator for the training of needle insertion into the epidural space was designed. The patient phantom provides a realistic force feedback comparable with biological tissue and enables sensing of the needle tip position during insertion. A display delivers the trainee a real-time feedback of the needle tip position.

Investigating determinants for patient satisfaction in women receiving epidural analgesia for labour pain: a retrospective cohort study

BACKGROUND

Epidural analgesia is a popular choice for labour pain relief. Patient satisfaction is an important patient-centric outcome because it can significantly influence both mother and child. However, there is limited evidence in the correlations between clinical determinants and patient satisfaction. We aim to investigate clinical covariates that are associated with low patient satisfaction in parturients receiving labour neuraxial analgesia.

METHODS

After institutional ethics approval was obtained, we conducted a retrospective cohort study using electronic and corresponding hardcopy records from 10,170 parturients receiving neuraxial analgesia between the periods of January 2012 to December 2013 in KK Women's and Children's Hospital in Singapore. Demographic, obstetric and anesthetic data were collected. The patient satisfaction scores on the neuraxial labour analgesia was reported by the parturient at 24 to 48 h post-delivery during the post-epidural round conducted by the resident and pain nurse. Parturients were stratified into one of three categories based on their satisfaction scores. Ordinal logistic regression models were used to identify potential covariates of patient dissatisfaction.

RESULTS

10,146 parturients were included into the study, of which 3230 (31.8%) were 'not satisfied', 3646 (35.9%) were 'satisfied', and 3270 (32.2%) were 'very satisfied'. Multivariable ordinal logistic regression analysis showed that instrument-assisted vaginal delivery (p = 0.0007), higher post-epidural pain score (p = 0.0016), receiving epidural catheter resiting (p <  0.0001), receiving neuraxial analgesia at a more advanced cervical dilation (p = 0.0443), multiparity (p = 0.0039), and post-procedure complications headache (p = 0.0006), backache (p <  0.0001), urinary retention (p = 0.0002) and neural deficit (p = 0.0297) were associated with patient dissatisfaction. Chinese, compared with other ethnicities (p = 0.0104), were more likely to be dissatisfied.

CONCLUSIONS

Our study has identified several clinical determinants that were independent associated factors for low patient satisfaction. These covariates could be useful in developing a predictive model to detect at-risk parturients and undertake time-sensitive precautionary measures for better patient satisfaction.

A survey of international antisepsis procedures for neuraxial catheterisation in labour

BACKGROUND

Neuraxial analgesia during labour is a mainstay of anaesthetic practice globally. Despite the potential for significant neurological and infectious complications, international antisepsis practices for neuraxial anaesthesia vary widely.

AIMS

The primary aim of this study was to clarify international antisepsis practices prior to neuraxial analgesia in labour. The secondary aim was to determine an approximate international incidence of neuraxial infections and neurological complications secondary to neuraxial analgesia techniques in labour.

MATERIALS AND METHODS

Heads of Departments of Anaesthesiology were invited to complete an online questionnaire exploring antisepsis practices and complications of neuraxial catheterisation. Data from 151 institutions in 13 countries were collected over 11months.

RESULTS

Data were collected for an estimated 6008540 deliveries and 3770800 neuraxial catheterisations. The average annual birth rate per institution was 3979 births, with an average of 2497 neuraxial catheterizations (representing 62.8% of deliveries). Forty-nine percent of responders reported always wearing sterile gowns for the procedure, whereas 47.7% never wear gowns. Chlorhexidine was used by 88.1% of those surveyed, and 96.7% always wore facemasks. Thirty-four percent of institutions reported infectious complications over a 10-year period. Ninety neuraxial infections were estimated, giving an approximate incidence of 1:41898 catheterisations (2.39 infections per 100000 catheterisations). A total of 202 neurological complications were reported, with an approximate incidence of 1:18667 catheterisations (5.36 neurological complications per 100000 catheterisations).

CONCLUSION

The survey demonstrated marked variation in aseptic practice between both responding centres and countries. The incidence of infectious and neurological complications secondary to neuraxial catherisation in labour has been approximated.

Risk factors for peripheral nerve injuries following neuraxial labour analgesia: a nested case-control study

BACKGROUND

Post-partum lower extremity motor and sensory dysfunctions occur in 0.1-9.2‰ of deliveries. While macrosomia, lithotomy position and forceps use are well-identified causes of peripheral nerve injuries, additional contributors such as patient condition and anaesthesia care may also have to be considered.

METHODS

We performed a case-control study nested in a cohort of 19,840 patients having neuraxial anaesthesia for childbirth. Cases were all patients who developed motor or sensory dysfunction of lower extremities in the post-partum period. These were compared, using Chi-square, Fisher's exact test, logistic regression and time series, to a random sample of controls without any neurological symptoms or injury.

RESULTS

We identified 19 (0.96‰) patients with peripheral nerve injuries of which 15 (0.76‰) were likely associated with obstetrical care. In four additional cases (0.20‰), a nerve root injury due to the Tuohy needle was suspected. Univariate risk factors were: a gestational age ≥ 41 weeks, Odds Ratio (OR) 3.8; 95% CI: 1.1-13.1, late initiation of neuraxial anaesthesia OR 8.2; 95% CI: 1.8-37.9, a repeated anaesthetic procedure OR 2.8; 95% CI: 1.0-7.8, assisted delivery with forceps OR 9.8; 95% CI: 1.2-114.1 and newborn birth weight > 3.5 kg with an OR 6.8; 95% CI: 2.0-22.5.

CONCLUSION

Obstetrical related factors are the most prominent risk associated with peripheral nerve injuries. This study highlights however that patient and anaesthesia-related factors may also contribute to peripheral nerve injuries.

Comparative Analysis of the Paravertebral Analgesic Pump Catheter with the Epidural Catheter in Elderly Trauma Patients with Multiple Rib Fractures

Presently, trauma guidelines recommend epidural analgesia as the optimal modality of pain relief from rib fractures. They are not ideally suited for elderly trauma patients and have disadvantages including bleeding risk. The paravertebral analgesic pump (PVP) eliminates such disadvantages and includes ease of placement in the trauma setting. This study compares pain control in patients treated by EPI versus PVP. This is a retrospective, historical cohort study comparing two methods of pain management in the trauma setting. Before 2010, patients who had epidural catheters (EPI) placed for pain control were compared with patients after 2010 in which the PVP was used. All patients had multiple rib fractures as diagnosed by CT scan. Analysis was adjusted for age, number of fractures, and comorbid conditions. Multiple linear regression analysis was conducted to compare average reported pain. A total of 110 patients, 31 PVP and 79 epidural catheters, were included in the study. Overall mean age was 65 years. The mean Injury Severity Score was 12.0 (EPI) and 11.1 (PVP). Mean number rib fractures was 4.29 (EPI) and 4.71 (PVP). PVP was associated with a 30 per cent greater decrease in pain than that seen with EPI (6.0–1.9 vs 6.4–3.4). After controlling for age, Injury Severity Score, and number of rib fractures, there were no differences in intensive care unit or total length of stay (P = 0.35) or in pain score (3.76 vs 3.56, P = 0.64). In conclusion, the PVP compares well with epidural analgesia in older trauma patients yet is safe, well tolerated, and easily inserted.

Development of artificial tissue-like structures for a hybrid epidural anesthesia simulator

Puncturing the epidural space and lumbar puncture are common procedures in anesthesia. They are carried out blind, where a needle is advanced from posterior between two adjacent vertebrae. Two different approaches are common practice for this technique, the midline and the paramedian one. The learning curve characteristics of both approaches significantly depends on the number of punctures carried out by a medical novice. For the training of these blind procedures a hybrid simulator requires artificial structures imitating the tissues which are penetrated by the needle. Within this work a patient phantom for spinal needle insertion procedures was developed and validated successfully against literature as well as by a study carried out with medical experts.

Localization of epidural space: A review of available technologies

Although epidural analgesia is widely used for pain relief, it is associated with a significant failure rate. Loss of resistance technique, tactile feedback from the needle, and surface landmarks are traditionally used to guide the epidural needle tip into the epidural space (EDS). The aim of this narrative review is to critically appraise new and emerging technologies for identification of EDS and their potential role in the future. The PubMed, Cochrane Central Register of Controlled Clinical Studies, and Web of Science databases were searched using predecided search strategies, yielding 1048 results. After careful review of abstracts and full texts, 42 articles were selected to be included. Newer techniques for localization of EDS can be broadly classified into techniques that (1) guide the needle to the EDS, (2) identify needle entry into the EDS, and (3) confirm catheter location in EDS. An ideal method should be easy to learn and perform, easily reproducible with high sensitivity and specificity, identifies inadvertent intrathecal and intravascular catheter placements with ease, feasible in perioperative setting and have a cost-benefit advantage. Though none of them in their current stages of development qualify as an ideal method, many show tremendous potential. Some techniques are useful in patients with difficult spinal anatomy and infants, and thus are complementary to traditional methods. In addition to improving the existing technology, future research should aim at proving the superiority of these techniques over traditional methods, specifically regarding successful EDS localization, better safety profile, and a favorable cost-benefit ratio.

Anaesthetic Management of Obese Parturients: What is the Evidence Supporting Practice Guidelines?

Increasing rates of obesity in western populations present management difficulties for clinicians caring for obese pregnant women. Various governing bodies have published clinical guidelines for the care of obese parturients. These guidelines refer to two components of anaesthetic care: anaesthetic consultation in the antenatal period for women with a body mass index (BMI) > 40 kg/m2 and the provision of early epidural analgesia in labour. These recommendations are based on the increased incidence of obstetric complications and the predicted risks and difficulties in providing anaesthetic care. The concept behind early epidural analgesia is logical—site the epidural early, use it for surgical anaesthesia and avoid general anaesthesia if surgery is required. Experts support this recommendation, but there is weak supporting evidence. It is known that the management of labour epidurals in obese women is complicated and that women with extreme obesity require higher rates of general anaesthesia. Anecdotally, anaesthetists view and apply the early epidural recommendation inconsistently and the acceptability of early epidural analgesia to pregnant women is variable. In this topic review, we critically appraise these two practice recommendations. The elements required for effective implementation in multidisciplinary maternity care are considered. We identify gaps in the current literature and suggest areas for future research. While prospective cohort studies addressing epidural extension (‘top-up’) in obese parturients would help inform practice, audit of local practice may better answer the question “is early epidural analgesia beneficial to obese women in my practice?”.

Evaluation of failed and high blocks associated with spinal anesthesia for Cesarean delivery following inadequate labour epidural: a retrospective cohort study

PURPOSE

The purpose of this retrospective cohort study was to investigate factors associated with failed and high spinal blocks in patients who received spinal anesthesia for Cesarean delivery following a labour epidural that was inadequate for surgical anesthesia.

METHODS

We searched our perioperative database for women with a labour epidural who received spinal or combined spinal-epidural anesthesia for Cesarean delivery due to the inadequacy of the existing epidural. The primary outcome was the occurrence of failed spinal blocks, and the secondary outcome was the occurrence of high blocks following spinal administration.

RESULTS

Of the 263 patients in the analysis, there were 29 (11%) failed spinals and nine (3%) high spinals. There was a significant difference between patients with failed spinals and those with successful spinals with regards to receipt of an epidural top-up dose for Cesarean delivery within 30 min of the spinal, type of neuraxial block, body mass index, age, and dose of hyperbaric bupivacaine. In a multivariable analysis, only receipt of an epidural top-up dose was associated with failure (OR, 6.0; 95% CI, 2.1 to 17.0; P < 0.001). As for the risk of a high spinal, patient characteristics and block details were not different amongst patients, except for a younger age in those with a high block.

CONCLUSIONS

Administration of spinal anesthesia within 30 min of an epidural top-up dose is associated with increased risk of failure. We speculate that this may be due in part to the presence of a large volume of local anesthetic in the epidural space, which may be mistaken for cerebrospinal fluid during spinal placement.

Nationwide incidence of serious complications of epidural analgesia in the United States

BACKGROUND

This study aimed to describe the incidence and risk factors of in-hospital spinal hematoma and abscess associated with epidural analgesia in adult obstetric and non-obstetric populations in the United States.

METHODS

The Nationwide Inpatient Sample was analyzed to identify patients receiving epidural analgesia from 1998 to 2010. Primary outcomes were incidence of spinal hematoma and epidural abscess. Use of decompressive laminectomy was also investigated. Regression analyses were conducted to assess predictors of epidural analgesia complications. Differences in mortality and disposition of patients at discharge were compared in patients with and without neuraxial complications. Obstetric and non-obstetric patients were studied separately.

RESULTS

A total of 3,703,755 epidural analgesia procedures (2,320,950 obstetric and 1,382,805 non-obstetric) were identified. In obstetric patients, the incidence of spinal hematoma was 0.6 per 100,000 epidural catheterizations (95% CI, 0.3 to 1.0 × 10(-5) ). The incidence of epidural abscess was zero. In non-obstetric patients, the incidence of spinal hematoma and epidural abscess were, respectively, 18.5 per 100,000 (95% CI, 16.3 to 20.9 × 10(-5) ) and 7.2 per 100,000 (95% CI, 5.8 to 8.7 × 10(-5) ) catheterizations. Predictors of spinal hematoma included type of surgical procedure (higher in vascular surgery), teaching status of hospital, and comorbidity score. Patients with spinal complications had higher in-hospital mortality (12.2% vs. 1.1%, P < 0.0001) and were significantly less likely to be discharged to home.

CONCLUSIONS

This large nationwide data analysis reveals that the incidence of epidural analgesia-related complications is very low in obstetric population epidural analgesia and much higher in patients having vascular surgery.

Risks of parenteral antihypertensive therapy for the treatment of severe maternal hypertension are low

OBJECTIVE

To determine whether the incidence of hypotension or adverse fetal heart tracing (FHT) category change differed following antepartum administration of intravenous (IV) labetalol versus hydralazine.

METHODS

Blood pressure and FHT categories were assessed one hour before and after medication administration. Hypotension was defined as ≥30% reduction in baseline systolic blood pressure (SBP) or SBP <90 mmHg. Changes in mean arterial pressure (MAP) were also compared. The National Institute for Child Health and Human Development (NICHD) three-tier category system was used to describe the FHT. For all category II tracings, Parer and Ikeda's system was also used.

RESULTS

Sixty-nine women received hydralazine and 31 women received labetalol during the study period. The incidence of hypotension (≥30% reduction in SBP) was similar between the labetalol (10%) and hydralazine (11%) groups (p = 0.98). No women experienced post-treatment SBP <90 mmHg. No association was observed between fetal heart rate category change and drug used. No women required emergent delivery for fetal indications.

CONCLUSIONS

The incidence of maternal hypotension was low and did not differ following antepartum IV labetalol versus hydralazine use. These data should reassure providers about the use of parenteral labetalol and hydralazine for the treatment of severe hypertension.

Clinical Practice of Epidural Puncture in Dogs and Cats Assisted by a Commercial Acoustic Puncture Assist Device-Epidural Locator: Preliminary Results

The objective of this study was to compare an Acoustic Puncture Assist Device-Epidural Locator (APAD-EL) with the "pop sensation" (POP) and "lack of resistance" (LOR) commonly used to confirm penetration of the ligamentum flavum and to ensure correct epidural placement in dogs and cats. We recruited 38 dogs and cats undergoing surgery and receiving epidural analgesia. Two anesthetists performed epidural puncture using the POP and LOR signs. Simultaneously, APAD-EL was used to collect visual and acoustic confirmation during advancement and placement of the needle tip for post hoc evaluation. A positive APAD-EL sign consists of a sudden pressure drop at the needle tip visible on a display and a concomitant pitch change of an acoustic signal. Failure to record a sudden pressure drop is considered a negative APAD sign. Descriptive statistics were used. In 32 patients with positive POP and LOR, the APAD was also positive. In one patient, POP was positive with a negative LOR and APAD result. Five patients had negative POP but positive LOR. Four patients had APAD positive and one (a dog) APAD negative. The study results showed that the APAD-EL information supports the subjective signs of correct needle placement suggested by positive POP and LOR experienced by trained anesthetists. The technique can be useful to assist difficult epidural puncture and as a training and teaching tool.

Comparative evaluation of continuous intercostal nerve block or epidural analgesia on the rate of respiratory complications, intensive care unit, and hospital stay following traumatic rib fractures: a retrospective review

BACKGROUND

Thoracic trauma accounts for 10%-15% of all trauma admissions. Rib fractures are the most common injury following blunt thoracic trauma. Epidural analgesia improves patient outcomes but is not without problems. The use of continuous intercostal nerve blockade (CINB) may offer superior pain control with fewer side effects. This study's objective was to compare the rate of pulmonary complications when traumatic rib fractures were treated with CINB vs epidurals.

METHODS

A hospital trauma registry provided retrospective data from 2008 to 2013 for patients with 2 or more traumatic rib fractures. All subjects were admitted and were treated with either an epidural or a subcutaneously placed catheter for continuous intercostal nerve blockade. Our primary outcome was a composite of either pneumonia or respiratory failure. Secondary outcomes included total hospital days, total ICU days, and days on the ventilator.

RESULTS

12.5% (N=8) of the CINB group developed pneumonia or had respiratory failure compared to 16.3% (N=7) in the epidural group. No statistical difference (P=0.58) in the incidence of pneumonia or vent dependent respiratory failure was observed. There was a significant reduction (P=0.05) in hospital days from 9.72 (SD 9.98) in the epidural compared to 6.98 (SD 4.67) in the CINB group. The rest of our secondary outcomes showed no significant difference.

CONCLUSION

This study did not show a difference in the rate of pneumonia or ventilator-dependent respiratory failure in the CINB vs epidural groups. It was not sufficiently powered. Our data supports a reduction in hospital days when CINB is used vs epidural. CINB may have advantages over epidurals such as fewer complications, fewer contraindications, and a shorter time to placement. Further studies are needed to confirm these statements.

Feature extraction and classification for ultrasound images of lumbar spine with support vector machine

In this paper, we proposed a feature extraction and machine learning method for the classification of ultrasound images obtained from lumbar spine of pregnant patients in the transverse plane. A group of features, including matching values and positions, appearance of black pixels within predefined windows along the midline, are extracted from the ultrasound images using template matching and midline detection. Support vector machine (SVM) with Gaussian kernel is utilized to classify the bone images and interspinous images with optimal separation hyperplane. The SVM is trained with 800 images from 20 pregnant subjects and tested with 640 images from a separate set of 16 pregnant patients. A high success rate (97.25% on training set and 95.00% on test set) is achieved with the proposed method. The trained SVM model is further tested on 36 videos collected from 36 pregnant subjects and successfully identified the proper needle insertion site (interspinous region) on all of the cases. Therefore, the proposed method is able to identify the ultrasound images of lumbar spine in an automatic manner, so as to facilitate the anesthetists' work to identify the needle insertion point precisely and effectively.

Lumbar Ultrasound Image Feature Extraction and Classification with Support Vector Machine

Needle entry site localization remains a challenge for procedures that involve lumbar puncture, for example, epidural anesthesia. To solve the problem, we have developed an image classification algorithm that can automatically identify the bone/interspinous region for ultrasound images obtained from lumbar spine of pregnant patients in the transverse plane. The proposed algorithm consists of feature extraction, feature selection and machine learning procedures. A set of features, including matching values, positions and the appearance of black pixels within pre-defined windows along the midline, were extracted from the ultrasound images using template matching and midline detection methods. A support vector machine was then used to classify the bone images and interspinous images. The support vector machine model was trained with 1,040 images from 26 pregnant subjects and tested on 800 images from a separate set of 20 pregnant patients. A success rate of 95.0% on training set and 93.2% on test set was achieved with the proposed method. The trained support vector machine model was further tested on 46 off-line collected videos, and successfully identified the proper needle insertion site (interspinous region) in 45 of the cases. Therefore, the proposed method is able to process the ultrasound images of lumbar spine in an automatic manner, so as to facilitate the anesthetists' work of identifying the needle entry site.

Blood volume determination in obese and normal-weight gravidas: the hydroxyethyl starch method

OBJECTIVE

The impact of obesity on maternal blood volume in pregnancy has not been reported. We compared the blood volumes of obese and normal-weight gravidas using a validated hydroxyethyl starch (HES) dilution technique for blood volume estimation.

STUDY DESIGN

Blood volumes were estimated in 30 normal-weight (pregravid body mass index [BMI] <25 kg/m(2)) and 30 obese (pregravid BMI >35 kg/m(2)) gravidas >34 weeks' gestation using a modified HES dilution technique. Blood samples obtained before and 10 minutes after HES injection were analyzed for plasma glucose concentrations after acid hydrolysis of HES. Blood volume was calculated from the difference between glucose concentrations measured in hydrolyzed plasma.

RESULTS

Obese gravidas had higher pregravid and visit BMI (mean [SD]): pregravid (41 [4] vs 22 [2] kg/m(2), P = .001); visit (42 [4] vs 27 [2] kg/m(2), P = .001), but lower weight gain (5 [7] vs 12 [4] kg, P = .001) than normal-weight women. Obese gravidas had similar estimated total blood volume to normal-weight women (8103 ± 2452 vs 6944 ± 2830 mL, P = .1), but lower blood volume per kilogram weight (73 ± 22 vs 95 ± 30 mL/kg, P = .007).

CONCLUSION

Obese gravidas have similar circulating blood volume, but lower blood volume per kilogram body weight, than normal-weight gravidas near term.

Algorithm for the anesthetic management of cesarean delivery in patients with unsatisfactory labor epidural analgesia

The management of a patient presenting with unsatisfactory labor epidural analgesia poses a severe challenge for the anesthetist wanting to provide safe anesthetic care for a cesarean delivery. Early recognition of unsatisfactory labor analgesia allows for replacement of the epidural catheter. The decision to convert labor epidural analgesia to anesthesia for cesarean delivery is based on the urgency of the cesarean delivery, airway examination, and the existence of a residual sensory and motor block.  We suggest an algorithm which is implemented in our department, based on the urgency of the cesarean delivery.