Cristian Arzola

Ultrasound Using the Transverse Approach to the Lumbar Spine Provides Reliable Landmarks for Labor Epidurals

BACKGROUND: Ultrasound imaging of the spine has recently been proposed to facilitate identification of the epidural space. In this study, we assessed the accuracy and precision of the transverse approach, using a “single-screen” method, to facilitate labor epidurals. METHODS: We enrolled 61 patients requesting labor epidurals. Ultrasound imaging (transverse approach, 2–5 MHz curved array probe) identified the midline, the intervertebral space, and the distance from the skin to the epidural space (ultrasound depth/UD). During the epidural puncture, we recorded the success of the insertion point, and measured the distance to the epidural space to the nearest half-centimeter of the marked Tuohy needle (needle depth/ND). We calculated the agreement between UD and ND by the concordance correlation coefficient and Bland–Altman analysis with 95% limits of agreement. RESULTS: The average maternal age was 33 ± 4.6 yr, body mass index 29.7 ± 4.8, UD 4.66 ± 0.68 cm, and ND 4.65 ± 0.72 cm. The success of the insertion point was 91.8%, with no need to redirect the needle in 73.8% of the patients. The concordance correlation coefficient between UD and ND was 0.881 (95% CI 0.820–0.942). The 95% limits of agreement were −0.666 to 0.687 cm. CONCLUSIONS: We found a good level of success in the ultrasound-determined insertion point, and very good agreement between UD and ND. This suggests that our proposed ultrasound single-screen method, using the transverse approach, can be a reliable guide to facilitate labor epidural insertion.

Ultrasound imaging for lumbar punctures and epidural catheterisations: systematic review and meta-analysis

Objective To determine whether ultrasound imaging can reduce the risk of failed lumbar punctures or epidural catheterisations, when compared with standard palpation methods, and whether ultrasound imaging can reduce traumatic procedures, insertion attempts, and needle redirections. Design Systematic review and meta-analysis of randomised controlled trials. Data sources Ovid Medline, Embase, and Cochrane Central Register of Controlled Trials up to May 2012, without restriction by language or publication status. Review methods Randomised trials that compared ultrasound imaging with standard methods (no imaging) in the performance of a lumbar puncture or epidural catheterisation were identified. Results 14 studies with a total of 1334 patients were included (674 patients assigned to the ultrasound group, 660 to the control group). Five studies evaluated lumbar punctures and nine evaluated epidural catheterisations. Six of 624 procedures conducted in the ultrasound group failed; 44 of 610 procedures in the control group failed. Ultrasound imaging reduced the risk of failed procedures (risk ratio 0.21 (95% confidence interval 0.10 to 0.43), P<0.001). Risk reduction was similar when subgroup analysis was performed for lumbar punctures (risk ratio 0.19 (0.07 to 0.56), P=0.002) or epidural catheterisations (0.23 (0.09 to 0.60), P=0.003). Ultrasound imaging also significantly reduced the risk of traumatic procedures (risk ratio 0.27 (0.11 to 0.67), P=0.005), the number of insertion attempts (mean difference −0.44 (−0.64 to −0.24), P<0.001), and the number of needle redirections (mean difference −1.00 (−1.24 to −0.75), P<0.001). Conclusions Ultrasound imaging can reduce the risk of failed or traumatic lumbar punctures and epidural catheterisations, as well as the number of needle insertions and redirections. Ultrasound may be a useful adjunct for these procedures.

Efficacy of low-dose bupivacaine in spinal anaesthesia for Caesarean delivery: systematic review and meta-analysis

We have conducted a meta-analysis of the clinical effects of morphine and hydromorphone to compare their benefit in analgesia. Embase and Medline were searched with an end-date of June 2009 for randomized, controlled trials or observational studies that addressed comparative analgesic and side-effects or particular side-effects. Two researchers independently identified included studies and extracted the data. Estimates of opioid effects were combined by using a random-effects model. Meta-analysis of eight studies suggested that hydromorphone (494 patients) provides slightly better (P=0.012) clinical analgesia than morphine (510 patients). The effect-size was small (Cohens d=0.266) and disappeared when one study was removed, although the advantage of hydromorphone was more evident in studies of better quality (Jadads rating). Side-effects were similar, for example, nausea (P=0.383, nine studies, 456 patients receiving hydromorphone and 460 morphine); vomiting (P=0.306, six studies, 246 patients receiving hydromorphone and 239 morphine); or itching (P=0.249, eight studies, 405 patients receiving hydromorphone, 410 morphine). This suggests some advantage of hydromorphone over morphine for analgesia. Additional potential clinical pharmacological advantages with regard to side-effects, such as safety in renal failure or during acute analgesia titration, are based on limited evidence and require substantiation by further studies.Spinal anaesthesia is the preferred anaesthetic technique for elective Caesarean deliveries. Hypotension is the most common side-effect and has both maternal and neonatal consequences. Different strategies have been attempted to prevent spinal-induced hypotension, including the use of low-dose bupivacaine. We conducted a systematic search for randomized controlled trials comparing the efficacy of spinal bupivacaine in low dose (LD ≤8 mg) with conventional dose (CD >8 mg) for elective Caesarean delivery. Thirty-five trials were identified for eligibility assessment, 15 were selected for data extraction, and 12 were finally included in the meta-analysis. We investigated sources of heterogeneity, subgroup analysis, and meta-regression for confounding variables (baricity, intrathecal opioids, lateral vs sitting position, uterine exteriorization, and study population). Sensitivity analysis was performed to test the robustness of the results. In the LD group, the need for analgesic supplementation during surgery was significantly higher [risk ratio (RR)=3.76, 95% confidence interval (95% CI)=2.38-5.92] and the number needed to treat for an additional harmful outcome (NNTH) was 4 (95% CI=2-7). Furthermore, the LD group exhibited a lower risk of hypotension (RR=0.78, 95% CI=0.65-0.93) and nausea/vomiting (RR=0.71, 95% CI=0.55-0.93). Conversion to general anaesthesia occurred only in the LD group (two events). Neonatal outcomes (Apgar score, acid-base status) and clinical quality variables (patient satisfaction, surgical conditions) showed non-significant differences between LD and CD. This meta-analysis demonstrates that low-dose bupivacaine in spinal anaesthesia compromises anaesthetic efficacy (risk of analgesic supplementation: high grade of evidence), despite the benefit of lower maternal side-effects (hypotension, nausea/vomiting: moderate grade of evidence).

Ultrasound Improves Cricothyrotomy Success in Cadavers with Poorly Defined Neck Anatomy: A Randomized Control Trial.

Background: Misidentification of the cricothyroid membrane in a “cannot intubate-cannot oxygenate” situation can lead to failures and serious complications. The authors hypothesized that preprocedure ultrasound-guided identification of the cricothyroid membrane would reduce complications associated with cricothyrotomy. Methods: A group of 47 trainees were randomized to digital palpation (n = 23) and ultrasound (n = 24) groups. Cricothyrotomy was performed on human cadavers by using the Portex® device (Smiths Medical, USA). Anatomical landmarks of cadavers were graded as follows: grade 1—easy = visual landmarks; 2—moderate = requires light palpation of landmarks; 3—difficult = requires deep palpation of landmarks; and 4—impossible = landmarks not palpable. Primary outcome was the complication rate as measured by the severity of injuries. Secondary outcomes were correct device placement, failure to cannulate, and insertion time. Results: Ultrasound guidance significantly decreased the incidence of injuries to the larynx and trachea (digital palpation: 17 of 23 = 74% vs. ultrasound: 6 of 24 = 25%; relative risk, 2.88; 95% CI, 1.39 to 5.94; P = 0.001) and increased the probability of correct insertion by 5.6 times (P = 0.043) in cadavers with difficult and impossible landmark palpation (digital palpation 8.3% vs. ultrasound 46.7%). Injuries were found in 100% of the grades 3 to 4 (difficult–impossible landmark palpation) cadavers by digital palpation compared with only 33% by ultrasound (P < 0.001). The mean (SD) insertion time was significantly longer with ultrasound than with digital palpation (196.1 s [60.6 s] vs. 110.5 s [46.9 s]; P < 0.001). Conclusion: Preprocedure ultrasound guidance in cadavers with poorly defined neck anatomy significantly reduces complications and improves correct insertion of the airway device in the cricothyroid membrane.

Intra- and interrater reliability of ultrasound assessment of gastric volume.

Background:Gastric sonography can provide information about gastric content and volume that can help determine aspiration risk at the bedside. The primary objective of this study is to assess the intrarater and interrater reliability of a previously validated method of gastric volume assessment based on gastric antral area. The secondary objective is to evaluate the agreement between two different methods to measure gastric antral area. Methods:Three independent raters performed a standardized gastric ultrasound assessment in healthy subjects who had been randomly allocated to ingest a predetermined volume of clear fluid (apple juice) from 0 to 400 ml. Each rater measured the gastric antral area, using twice the two-diameter method and twice the free-tracing method. The rater order was allocated at random and raters were unaware of the volume ingested and of one-another’s measurements. The Guidelines for Reporting Reliability and Agreement Studies were followed for conducting and reporting this study. Results:Twenty-two volunteers were studied. Ultrasound assessment of antral cross-sectional area and volume was found to have “nearly perfect” intrarater and interrater reliability (correlation coefficient >0.8) with maximum differences within 13%. A Bland–Altman analysis suggests that the free-tracing method and the two-diameter method are essentially equivalent, within a clinically acceptable level of agreement. Conclusions:Ultrasound assessment of gastric volume by clinical anesthesiologists is highly reproducible with high intrarater and interrater reliability. The free-tracing method to measure antral cross-sectional area is equivalent to the two-diameter method.

Challenging authority during a life-threatening crisis: the effect of operating theatre hierarchy

BACKGROUND Effective operating theatre (OT) communication is important for team function and patient safety. Status asymmetry between team members may contribute to communication breakdown and threaten patient safety. We investigated how hierarchy in the OT team influences an anaesthesia trainees ability to challenge an unethical decision by a consultant anaesthetist in a simulated crisis scenario. METHODS We prospectively randomized 49 postgraduate year (PGY) 2-5 anaesthesia trainees at two academic hospitals to participate in a videotaped simulated crisis scenario with a simulated OT team practicing either a hierarchical team structure (Group H) or a non-hierarchical team structure (Group NH). The scenario allowed trainees several opportunities to challenge their consultant anaesthetist when administering blood to a Jehovahs Witness. Three independent, blinded raters scored the performances using a modified advocacy-inquiry score (AIS). The primary outcome was the comparison of the best-response AIS between Groups H vs NH. Secondary outcomes included the comparison of best AIS by PGY and the percentage in each group that checked and administered blood. RESULTS The AIS did not differ between the groups (P=0.832) but significantly improved from PGY2 to PGY5 (P=0.026). The rates of checking blood (92% vs 76%, P=0.082) and administering blood (62% vs 57%, P=0.721) were high in both groups but not significantly different between the groups. CONCLUSIONS This study did not show a significant effect of OT team hierarchical structure on trainees ability to challenge authority; however, the results are concerning. The challenges were suboptimal in quality and there was an alarming high rate of blood checking and administration in both groups. This may reflect lack of training in appropriately and effectively challenging authority within the formal curriculum with implications for patient safety.

Deficits in information transfer between anaesthesiologist and postanaesthesia care unit staff: an analysis of patient handover

Background The immediate postoperative period is important, as the patient recovers from the acute derangements resulting from the surgical insult and anaesthesia. Incomplete or incorrect communication between the anaesthesiologist and the postanaesthesia care unit nurse during the transfer process may lead to dangerous clinical mistakes. The literature examining handovers from operating room to the postanaesthesia care unit is scarce. Objectives The primary objective of this study was to examine the current transfer practice through observation of handovers between the anaesthesiologists and the postanaesthesia care unit staff in order to identify data omissions. The secondary objective was to learn which data items the clinicians and nurses thought were a necessary part of the transfer process and whether this information was communicated at the time of handover. Design A prospective observational study. Setting Academic hospital in Toronto, Canada. Participants and interventions After Research Ethics Board approval, a prospective observational study was conducted at a university-affiliated teaching centre. During a 2-month period, multiple observations of patient handover were performed. The data provided were marked on a checklist. At the end of the study, participating nurses and physicians were surveyed regarding the necessity of communicating different items on the checklist. Results A total of 526 transfers were observed. Of 29 data items examined, only two items (type of surgery and analgesics given) were reported in more than 90% of handovers. Only three items (difficult intubation, ST-wave changes and co-morbidities/healthy) were reported in more than 80% of cases. Many items deemed as needed to be reported by the participants in the study were not communicated. Conclusion This study demonstrates that the handover process is inconsistent and in some cases information defined as important by the physicians and the nurses is not transferred. Further studies need to investigate whether a handover protocol leads to a minimisation of omissions in information transfer.

Spinal ultrasound versus palpation for epidural catheter insertion in labour: A randomised controlled trial.

BACKGROUND Ultrasound imaging of the spine is thought to reduce failed and traumatic neuraxial procedures. Most of the evidence supporting this assumption has been produced in the context of an expert sonographer performing the ultrasound assessment, and it remains unknown whether this technique is useful when used by multiple individual operators. OBJECTIVE To invesstigate the impact of preprocedural spinal ultrasound on the ease of insertion of labour epidurals by a group of trainees. We hypothesised that the ultrasound-assisted technique would improve the ease of insertion when compared with the conventional palpation technique. DESIGN A randomised controlled trial. SETTING Academic hospital in Toronto, Canada. PARTICIPANTS AND INTERVENTION A group of 17 second-year anaesthesia residents and five anaesthesia fellows underwent a training programme in ultrasound assessment of the spine. Parturients with easily palpable lumbar spines were randomised to either ultrasound or palpation group. Residents and fellows performed both the assessment (ultrasound or palpation) and the epidural procedure. MAIN OUTCOME MEASURES Primary outcome: ease of insertion of epidural catheter composed of the time taken to insert the epidural catheter, number of interspace levels attempted and number of needle passes. Secondary outcomes: total procedural time (assessment and insertion); first pass success rate; number of attempts required to thread the epidural catheter; failure of epidural analgesia; and patient satisfaction. RESULTS We analysed 128 epidural catheter insertions (residents 84, fellows 44). There was no difference in median (interquartile range, IQR) epidural insertion time between the ultrasound and palpation groups [174 (120 to 241) versus 180 (130 to 322.5) s, respectively; P = 0.14]. The number of interspace levels attempted and needle passes were also similar in both groups. The total procedural time was longer in the ultrasound group. CONCLUSION The use of preprocedural spinal ultrasound by a cohort of anaesthesia trainees did not improve the ease of insertion of labour epidural catheters in patients with easily palpable lumbar spines, as compared with the traditional palpation technique based on anatomical landmarks. TRIAL REGISTRATION ClinicalTrials.gov identifier: NCT00996905.

Ultrasound estimates for midline epidural punctures in the obese parturient: paramedian sagittal oblique is comparable to transverse median plane.

BACKGROUND:Spinal ultrasound (US) in the transverse median (TM) plane underestimates the distance to the epidural space in obese pregnant women, most likely because of compression of the subcutaneous tissue during the assessment, often required to compensate for poor visibility. We tested whether scanning in the paramedian sagittal oblique (PSO) plane compared with the TM plane resulted in a more precise estimate of the actual skin-epidural space measurement in this population. METHODS:We recruited obese (World Health Organization classes I, II, and III) pregnant women at term requesting labor epidural analgesia or combined spinal-epidural anesthesia for cesarean delivery. US imaging was performed with a 5-2 MHz curved array probe to identify the insertion point and to estimate the distance from the skin to the epidural space (US-estimated depth, UD) in the PSO and TM planes. The measurements were performed with the least possible compression of the subcutaneous tissue by the US probe. All punctures were performed via the midline approach. An anesthesiologist performed the epidural/combined spinal-epidural procedure at the predetermined insertion point, and marked the actual needle distance from the skin to the epidural space (needle depth, ND). Bland-Altman analysis was used to determine the differences and 95% limits of agreement between US depth and ND. RESULTS:We studied 60 women. The mean (SD) body mass index was 39.6 (7.9) kg/m2 (range 30.4–66.2 kg/m2). The US estimate in the PSO and TM planes, and the actual ND were 6.5 (1.2) cm, 6.5 (1.1) cm, and 6.6 (1.3) cm, respectively. The Bland-Altman analysis showed a mean difference of 0.05 cm and 95% limits of agreement of ±1 cm. The quality of imaging was rated as good in the PSO and TM planes in 86.7% and 68.3%, respectively (P = 0.028). CONCLUSION:The estimates of the US-determined distance to the epidural space in the PSO are comparable to those in the TM plane. The ability to use both estimates interchangeably for midline punctures may prove useful in patients presenting with poor visibility in the TM plane.

The utility of ultrasound imaging in predicting ease of performance of spinal anesthesia in an orthopedic patient population.

Background and Objectives Ultrasonography of the spine improves technical performance of spinal anesthesia, but what is unclear is whether it can predict difficulty. We tested the hypothesis that a good ultrasound view at a given intervertebral level is associated with absence of technical difficulty. Methods We performed preprocedural ultrasound of the L1-S1 intervertebral spaces in 100 patients undergoing orthopedic surgery. Visibility of the ligamentum flavum–dura mater and the posterior longitudinal ligament was evaluated using paramedian sagittal oblique and transverse midline (TM) views. Views were classified as good if both of these structures were visible on ultrasound. An operator, blinded to the ultrasound scan, performed surface landmark–guided spinal anesthesia using a midline approach. Absence of technical difficulty was defined as successful dural puncture within 2 skin punctures or 10 needle passes. Results A good TM view had the best diagnostic accuracy; if this view was obtained, absence of technical difficulty with dural puncture at that level was highly likely (positive predictive value, 85%). Dural puncture could still be feasible despite the absence of a good TM view, as reflected by a negative predictive value of 30%. This was attributed to the limitations of ultrasound imaging in this patient population, as well as the low overall prevalence of difficult dural puncture. Parasagittal oblique views did not have significant diagnostic utility for a midline needle approach. Conclusions Ultrasound can be useful in predicting the absence of technical difficulty in performing dural puncture and thus in selecting the optimal intervertebral level for spinal anesthesia.