Postpartum cerebral venous sinus thrombosis following obstetric neuraxial blockade: a literature review with analysis of 58 case reports.

BACKGROUND: Cerebral venous sinus thrombosis (CVST) is a rare complication of pregnancy. It usually presents with a headache and may mimic a post-dural puncture headache (PDPH) in women who receive a neuraxial block. METHODS: Medline, CINAHL and EMBASE databases were searched to identify postpartum cases of CVST following neuraxial block. The aim was to delineate the characteristics, presentation, investigations, and outcomes of postpartum women who presented with CVST. RESULTS: Forty-nine articles with 58 case reports were identified. Forty-two women (72.4%) had an epidural attempted whilst 16 women (27.6%) received a spinal anaesthetic. Accidental dural puncture (ADP) was reported in 17 women (40.5%). Headache was the presenting symptom in 57 women (98.3%); 26 women (44.8%) also experienced seizures. Post-dural puncture headache was reported in 46 (79.3%) and an epidural blood patch was performed in 26 women (44.8%). Superior sagittal sinus, transverse sinus, and cortical veins were the most common sites of thrombosis. The median time to diagnosis was 6.5 days from delivery. Magnetic resonance imaging was the most common diagnostic neuro-imaging modality. Full neurological recovery was reported in 48 (82.8%), whilst neurological deficits were reported in six (10.3%) women. DISCUSSION: The diagnosis of CVST may be overlooked in women who present with headache following neuraxial block. A change in character of headache with loss of postural element, and focal neurological signs are the key clinical features that could help anaesthetists differentiate headache of CVST from PDPH. The high reported rates of ADP and PDPH lend support to their possible association with CVST.

Decision-to-delivery interval and neonatal outcomes for category-1 caesarean sections during the COVID-19 pandemic.

General anaesthesia is known to achieve the shortest decision-to-delivery interval for category-1 caesarean section. We investigated whether the COVID-19 pandemic affected the decision-to delivery interval and influenced neonatal outcomes in patients who underwent category-1 caesarean section. Records of 562 patients who underwent emergency caesarean section between 1 April 2019 and 1 July 2019 in seven UK hospitals (pre-COVID-19 group) were compared with 577 emergency caesarean sections performed during the same period during the COVID-19 pandemic (1 April 2020-1 July 2020) (post-COVID-19 group). Primary outcome measures were: decision-to-delivery interval; number of caesarean sections achieving decision-to-delivery interval < 30 min; and a composite of adverse neonatal outcomes (Apgar 5-min score < 7, umbilical arterial pH < 7.10, neonatal intensive care unit admission and stillbirth). The use of general anaesthesia decreased significantly between the pre- and post-COVID-19 groups (risk ratio 0.48 (95%CI 0.37-0.62); p < 0.0001). Compared with the pre-COVID-19 group, the post-COVID-19 group had an increase in median (IQR [range]) decision-to-delivery interval (26 (18-32 [4-124]) min vs. 27 (20-33 [3-102]) min; p = 0.043) and a decrease in the number of caesarean sections meeting the decision-to-delivery interval target of < 30 min (374/562 (66.5%) vs. 349/577 (60.5%); p = 0.02). The incidence of adverse neonatal outcomes was similar in the pre- and post-COVID-19 groups (140/568 (24.6%) vs. 140/583 (24.0%), respectively; p = 0.85). The small increase in decision-to-delivery interval observed during the COVID-19 pandemic did not adversely affect neonatal outcomes.

The effect of COVID-19 on general anaesthesia rates for caesarean section. A cross-sectional analysis of six hospitals in the north-west of England.

At the onset of the global pandemic of COVID-19 (SARS-CoV-2), guidelines recommended using regional anaesthesia for caesarean section in preference to general anaesthesia. National figures from the UK suggest that 8.75% of over 170,000 caesarean sections are performed under general anaesthetic. We explored whether general anaesthesia rates for caesarean section changed during the peak of the pandemic across six maternity units in the north-west of England. We analysed anaesthetic information for 2480 caesarean sections across six maternity units from 1 April to 1 July 2020 (during the pandemic) and compared this information with data from 2555 caesarean sections performed at the same hospitals over a similar period in 2019. Primary outcome was change in general anaesthesia rate for caesarean section. Secondary outcomes included overall caesarean section rates, obstetric indications for caesarean section and regional to general anaesthesia conversion rates. A significant reduction (7.7 to 3.7%, p < 0.0001) in general anaesthetic rates, risk ratio (95%CI) 0.50 (0.39-0.93), was noted across hospitals during the pandemic. Regional to general anaesthesia conversion rates reduced (1.7 to 0.8%, p = 0.012), risk ratio (95%CI) 0.50 (0.29-0.86). Obstetric indications for caesarean sections did not change (p = 0.17) while the overall caesarean section rate increased (28.3 to 29.7%), risk ratio (95%CI) 1.02 (1.00-1.04), p = 0.052. Our analysis shows that general anaesthesia rates for caesarean section declined during the peak of the pandemic. Anaesthetic decision-making, recommendations from anaesthetic guidelines and presence of an on-site anaesthetic consultant in the delivery suite seem to be the key factors that influenced this decline.

A prospective, up-down sequential allocation study investigating the effectiveness of vital capacity breaths using high-flow nasal oxygenation versus a tight-fitting face mask to pre-oxygenate term pregnant women.

BACKGROUND: The role of high flow nasal oxygenation (HFNO) for pre-oxygenation before obstetric general anaesthesia remains unclear. This study aimed to determine the number of vital capacity breaths using HFNO required to pre-oxygenate 90% of parturients to an end-tidal oxygen concentration fraction (FETO2) of ≥0.90 (termed EN90). METHODS: Using up-down, sequential allocation trial design, volunteer term parturients undergoing caesarean delivery were investigated with HFNO with their mouth closed, followed by mouth open, and if FETO2 ≥0.90 was not achieved after a maximum of 20 vital capacity breaths, pre-oxygenation was attempted with a face mask. The primary outcome was the number of vital capacity breaths required using HFNO (mouth open and closed) to achieve EN90. Secondary outcomes included assessment of EN90 using mouth open versus mouth closed and face mask pre-oxygenation, maternal satisfaction and evaluation of fetal cardiotocography. RESULTS: Twenty women at term were recruited. Successful pre-oxygenation occurred in 4 (20%), 3 (15%) and 14 (70%) women with HFNO mouth closed, HFNO mouth open, and via face mask respectively. At up to 20 vital capacity breaths, face mask pre-oxygenation was more successful at achieving EN90 compared with both HFNO with a closed (P=0.006) or open (P=0.001) mouth. Closed mouth HFNO did not outperform open mouth pre-oxygenation. CONCLUSION: Face mask pre-oxygenation is more effective at achieving EN90 compared with to HFNO within a clinically acceptable number of vital capacity breaths. Further studies are needed to determine the role of HFNO in optimising the time before desaturation and for apnoeic oxygenation in term parturients.

Non-directed bronchial lavage is a safe method for sampling the respiratory tract in critically ill patient.

Ventilated patients are at risk of acquiring ventilator-associated pneumonia. Various techniques are available for diagnosing ventilator-associated pneumonia including bronchoalveolar lavage, protected specimen brush and non-directed bronchoalveolar lavage. There is a paucity of evidence regarding the safety profile of these techniques, particularly non-directed bronchoalveolar lavage. This service evaluation aimed to establish whether non-directed bronchoalveolar lavage is a safe procedure. A prospective service evaluation of non-directed bronchoalveolar lavage on our adult intensive care unit was undertaken by a senior physiotherapist trained into carrying out the procedure, measuring pre- and post-procedure vital signs including heart rate (HR), tidal volume (VT), systolic blood pressure (SBP) and pulse oximetry (SpO2). Eighty-five episodes in 41 patients were included in the evaluation. There was a statistically significant difference between pre- and immediately post-procedure recordings for all vital signs measure. HR (min-1), means (SD) 87.1 (16.4), 91.5 (16.5), 87.5 (15.9), 87.7 (15.7) respectively pre, immediately, 5 min after and 30 min after procedure (P < 0.01). SBP mmHg, means (SD) 133.9 (26.1), 142.1 (25.6), 136.9 (25.3), 134.8 (23.4) pre, immediately, 5 min and 30 min after procedure (P < 0.01). VT mL, median (range) 0.523 (0.118-1.180), 0.512 (0.131-1.05), 0.519 (0.104-0.95), 0.534 (0.110-1.080) each pre, immediately, 5 min and 30 min post procedure (P < 0.05). SpO2 %, median (range) 98 (89-100), 100 (96-100), 98 (92-100), 97 (90-100) again each pre-, immediately post, 5 and 30 min post-procedure time-points (P < 0.0001). The statistically significant difference was not detected between pre-, 5 or 30 min post-procedure time-points. None of the changes observed were clinically significant and no untoward events happened to any of the subjects included. Non-directed bronchoalveolar lavage is a safe and inexpensive procedure that can be carried out easily in an intensive care setting by a trained physiotherapist, avoiding the need for invasive bronchoscopy.

Cardiac output measurements during high-risk Cesarean section using electrical bioreactance or arterial waveform analysis: assessment of agreement.

OBJECTIVE: Maternal hemodynamics change significantly during Cesarean section complicated by massive hemorrhage or severe hypertensive disease. Cardiac output (CO) monitoring aids early, goal-directed hemodynamic therapy. The aim of this study was to record hemodynamic changes observed during Cesarean section in pregnancies at high risk of hemodynamic instability, using invasive (LiDCOrapid™) and non-invasive (NICOM®) devices, and to assess agreement between the two devices in measuring CO. METHODS: Simultaneous intraoperative hemodynamic measurements were taken using the LiDCOrapid and NICOM devices, following standardized techniques, in women at high risk of hemodynamic instability undergoing Cesarean section. Agreement in CO measurements between the two devices was assessed using Bland-Altman plots and the agreement:tolerability index (ATI). Agreement analyses were performed for repeated measures in subjects, using centiles. RESULTS: From 10 women, 307 paired measurements were analyzed. Mean bias (defined as the mean difference in CO measurements between the LiDCOrapid and NICOM devices) was 3.05 (95% CI, 1.89 to 4.21) L/min. Limits of agreement ranged from -1.58 (95% CI, -4.47 to -0.14) to 7.68 (95% CI, 6.24 to 10.56) L/min. The resulting agreement interval was 9.26 L/min which returned an ATI of 2.3. CONCLUSIONS: There are large mean differences between CO measurements obtained during Cesarean section using the LiDCOrapid and NICOM hemodynamic monitors in pregnant women at high risk of hemodynamic instability, indicating that they should not be considered interchangeable clinically. There is an unacceptably low level of agreement (ATI > 2) in CO measurements between the devices, conferring a high risk of clinical misclassification during massive hemorrhage. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Investigation into the visual perceptive ability of anaesthetists during ultrasound-guided interscalene and femoral blocks conducted on soft embalmed cadavers: a randomised single-blind study.

BACKGROUND: Errors may occur during regional anaesthesia whilst searching for nerves, needle tips, and test doses. Poor visual search impacts on decision making, clinical intervention, and patient safety. METHODS: We conducted a randomised single-blind study in a single university hospital. Twenty trainees and two consultants examined the paired B-mode and fused B-mode and elastography video recordings of 24 interscalene and 24 femoral blocks conducted on two soft embalmed cadavers. Perineural injection was randomised equally to 0.25, 0.5, and 1.0 ml volumes. Tissue displacement perceived on both imaging modalities was defined as 'target' or 'distractor'. Our primary objective was to test the anaesthetists' perception of the number and proportion of targets and distractors on B-mode and fused elastography videos collected during femoral and sciatic nerve block on soft embalmed cadavers. Our secondary objectives were to determine the differences between novices and experts, and between test-dose volumes, and to measure the area and brightness of spread and strain patterns. RESULTS: All anaesthetists recognised perineural spread using 0.25 ml volumes. Distractor patterns were recognised in 133 (12%) of B-mode and in 403 (38%) of fused B-mode and elastography patterns; P<0.001. With elastography, novice recognition improved from 12 to 37% (P<0.001), and consultant recognition increased from 24 to 53%; P<0.001. Distractor recognition improved from 8 to 31% using 0.25 ml volumes (P<0.001), and from 15 to 45% using 1 ml volumes (P<0.001). CONCLUSIONS: Visual search improved with fusion elastography, increased volume, and consultants. A need exists to investigate image search strategies.

Cardiac output changes with phenylephrine and ephedrine infusions during spinal anesthesia for cesarean section: A randomized, double-blind trial.

Hypotension is a common side effect of spinal anesthesia. Phenylephrine and ephedrine are the two most frequently used vasopressors to treat spinal hypotension during cesarean delivery. In this randomized double-blind study, we aimed to evaluate cardiac output (CO) changes with phenylephrine or ephedrine infusions titrated to maintain baseline systolic blood pressure (bSBP) during spinal anesthesia. Women (n = 40) scheduled for elective cesarean delivery received either phenylephrine 100 µg/min or ephedrine 5 mg/min infusions. Baseline hemodynamics (cardiac output, heart rate, systolic blood pressure) were recorded in the left lateral tilt position before fluid preload, and recorded every minute after spinal anesthesia until delivery. Umbilical cord blood gases were analyzed within 5 minutes of delivery. Good systolic blood pressure control was attained in both groups with minimal periods of hypotension (SBP <80% of bSBP) or hypertension (SBP >120% of bSBP). Cardiac output and heart rate increased over time with ephedrine, but decreased with phenylephrine. The maximum increase in CO from the baseline was 12%, in the ephedrine group, and this occurred 20 minutes after spinal injection. Cardiac output fell by more than 17% in the phenylephrine group, maximal at 10 minutes following spinal injection. Despite good systolic blood pressure control and increased cardiac output with ephedrine, administration of ephedrine was associated with significantly more fetal acidosis [Median (Interquartile range, IQR) UApH - phenylephrine = 7.33 (7.31-7.34) and ephedrine = 7.22 (7.16-7.27), P < .05].

Assessment of scoring systems to describe the position of tracheostomy tubes within the airway - the lunar study.

BACKGROUND: Malposition of tracheostomy tubes is difficult to detect at the bedside and may contribute to eventual device misplacement. Endoscopic examination can be undertaken via tracheoscopic (T-view) or trans-laryngeal (L-view) approach, offering more precise detail regarding positioning within the airway. The aims of this study were to evaluate inter-rater agreement between bespoke T and L view scoring systems and subsequently whether T-views could predict L-views. METHODS: Adult intensive care unit patients with percutaneous or surgical tracheostomies were included and paired T and L-views of their tracheostomy tube within the airway were taken on up to four occasions. Images were later scored by five independent raters using bespoke scoring systems. The primary outcome was to determine the T and L view scoring system with the best inter-rater agreement, defined by weighted kappa and intra-class correlation coefficients. The secondary outcome was to assess agreement between T and L-view scoring systems. RESULTS: Seventy-one T-views and 43 L-views were obtained from a total of 20 patients. Images were scored by five raters, resulting in 355 T-view scores, 215 L-view scores and 215 paired T and L-view scores for comparison. There was good inter-rater agreement (highest T-view k = 0.84, L-view k = 0.72). There was poor agreement between T and L-view scores for each of the paired images (highest k = 0.25) although extreme-to-extreme misclassification rates remained acceptable. CONCLUSIONS: Whilst our data demonstrated good inter-rater agreement between scoring systems, it is not possible to reliably predict the T-view orientation and position of a tracheostomy tube within the airway from the paired L-view. CLINICAL TRIAL REGISTRATION: NCT01356719.

Thromboelastography (TEG®) demonstrates that tinzaparin 4500 international units has no detectable anticoagulant activity after caesarean section.

BACKGROUND: Low molecular weight heparin is routinely used for thromboprophylaxis in pregnancy and the puerperium. Consensus guidelines recommend waiting 10-12h after administration of a thromboprophylactic dose of low molecular weight heparin before performing a neuraxial block or removing an epidural catheter. Thromboelastography (TEG®) has been reported to be sensitive to the effects of enoxaparin 4h after administration. The purpose of this study was to use TEG to examine coagulation changes in the first 10h after a thromboprophylactic dose of tinzaparin in an attempt to ratify the current consensus guidelines about timing of neuraxial blockade and epidural catheter removal. METHODS: Twenty-four women who had undergone caesarean delivery and were classified as low or intermediate risk of thrombosis were recruited. Blood samples were taken before subcutaneous administration of tinzaparin 4500IU, and at 4, 8 and 10h post-dose. Standard TEG analyses were performed using plain and heparinase cuvettes and samples were also sent for laboratory anti-Xa assay. Thromboelastograph profiles were analysed for a low molecular weight heparin effect. RESULTS: Analysis revealed no significant differences in R time, K time, alpha angle or maximum amplitude between plain and heparinase samples at any time point. Apart from a small statistically significant (P=0.033) decrease in maximum amplitude of 2.8% (95% CI 0.3 to 5.4%) at 4h, there were no significant changes in coagulation for any TEG parameter. Anti-Xa levels were virtually undetectable in all patients over the 10h period (median 0.00U/mL; range 0.00-0.13U/mL). CONCLUSION: A thromboprophylactic dose of tinzaparin 4500IU had little detectable effect on coagulation as assessed by TEG and anti-Xa assay. These findings support consensus guidelines which state that it is acceptable to perform neuraxial blockade or remove an epidural catheter 10-12h after a thromboprophylactic dose of tinzaparin. Rather than suggesting a lack of anticoagulant activity, the findings indicate that TEG may not have the sensitivity to detect a tinzaparin effect when this dose is used in this patient group.

Trainee anaesthetist diagnosis of intraneural injection-a study comparing B-mode ultrasound with the fusion of B-mode and elastography in the soft embalmed Thiel cadaver model.

BACKGROUND: The incidence of intraneural injection during trainee anaesthetist ultrasound guided nerve block varies between 16% in experts and up to 35% in trainees. We hypothesized that elastography, an ultrasound-based technology that presents colour images of tissue strain, had the potential to improve trainee diagnosis of intraneural injection during UGRA, when integrated with B-Mode ultrasound onto a single image. METHODS: We recorded 40 median nerve blocks randomly allocated to 0.25 ml, 0.5 ml, 1 ml volumes to five sites, on both arms of two soft embalmed cadavers, using a dedicated B-Mode ultrasound and elastography transducer. We wrote software to fuse elastogram and B-Mode videos, then asked 20 trainee anaesthetists whether injection was intraneural or extraneural when seeing B-Mode videos, adjacent B-Mode and elastogram videos, fusion elastography videos or repeated B-Mode ultrasound videos. RESULTS: Fusion elastography improved the diagnosis of intraneural injection compared with B-Mode ultrasound, Diagnostic Odds Ratio (DOR) (95%CI) 21.7 (14.5 - 33.3) vs DOR 7.4 (5.2 - 10.6), P < 0.001. Compared with extraneural injection, intraneural injection was identified on fusion elastography as a distinct, brighter translucent image, geometric ratio 0.33 (95%CI: 0.16 - 0.49) P < 0.001. Fusion elastography was associated with greater trainee diagnostic confidence, OR (95%CI) 1.89 (1.69 - 2.11), P < 0.001, and an improvement in reliability, Kappa 0.60 (0.55 - 0.66). CONCLUSIONS: Fusion elastography improved the accuracy, reliability and confidence of trainee anaesthetist diagnosis of intraneural injection.

Physical properties and functional alignment of soft-embalmed Thiel human cadaver when used as a simulator for ultrasound-guided regional anaesthesia.

BACKGROUND: We evaluated the physical properties and functional alignment of the soft-embalmed Thiel cadaver as follows: by assessing tissue visibility; by measuring its acoustic, mechanical and elastic properties; by evaluating its durability in response to repeated injection; and by aligning images with humans. METHODS: In four soft-embalmed Thiel cadavers, we conducted three independent studies. We assessed the following factors: (i) soft tissue visibility in a single cadaver for 28 weeks after embalming; (ii) the displacement of tissues in response to 1 and 5 ml interscalene and femoral nerve blocks in a single cadaver; and (iii) the stiffness of nerves and perineural tissue in two cadavers. We aligned our findings with ultrasound images from three patients and one volunteer. Durability was qualified by assessing B-mode images from repetitive injections during supervised training. RESULTS: There was no difference in visibility of nerves between 2 and 28 weeks after embalming {geometric mean ratio 1.13 [95% confidence interval (CI): 0.75-1.68], P=1.0}. Mean tissue displacement was similar for cadaver femoral and interscalene blocks [geometric mean ratio 1.02 (95% CI: 0.59-1.78), P=0.86], and for 1 and 5 ml injection volumes [geometric mean ratio 0.84 (95% CI: 0.70-1.01), P=0.19]. Cadavers had higher intraneural than extraneural stiffness [Young's modulus; geometric mean ratio 3.05 (95% CI: 2.98-3.12), P<0.001] and minimal distortion of anatomy when conducting 934 left-sided interscalene blocks on the same cadaver throughout a 10 day period. CONCLUSIONS: The soft-embalmed Thiel cadaver is a highly durable simulator that has excellent physical and functional properties that allow repeated injection for intensive ultrasound-guided regional anaesthesia training.