The application of a neural network to predict hypotension and vasopressor requirements non-invasively in obstetric patients having spinal anesthesia for elective cesarean section (C/S).

BACKGROUND: Neural networks are increasingly used to assess physiological processes or pathologies, as well as to predict the increased likelihood of an impending medical crisis, such as hypotension. METHOD: We compared the capabilities of a single hidden layer neural network of 12 nodes to those of a discrete-feature discrimination approach with the goal being to predict the likelihood of a given patient developing significant hypotension under spinal anesthesia when undergoing a Cesarean section (C/S). Physiological input information was derived from a non-invasive blood pressure device (Caretaker [CT]) that utilizes a finger cuff to measure blood pressure and other hemodynamic parameters via pulse contour analysis. Receiver-operator-curve/area-under-curve analyses were used to compare performance. RESULTS: The results presented here suggest that a neural network approach (Area Under Curve [AUC] = 0.89 [p < 0.001]), at least at the implementation level of a clinically relevant prediction algorithm, may be superior to a discrete feature quantification approach (AUC = 0.87 [p < 0.001]), providing implicit access to a plurality of features and combinations thereof. In addition, the expansion of the approach to include the submission of other physiological data signals, such as heart rate variability, to the network can be readily envisioned. CONCLUSION: This pilot study has demonstrated that increased coherence in Arterial Stiffness (AS) variability obtained from the pulse wave analysis of a continuous non-invasive blood pressure device appears to be an effective predictor of hypotension after spinal anesthesia in the obstetrics population undergoing C/S. This allowed us to predict specific dosing thresholds of phenylephrine required to maintain systolic blood pressure above 90 mmHg.

Continuous Non-invasive finger cuff CareTaker® comparable to invasive intra-arterial pressure in patients undergoing major intra-abdominal surgery.

BACKGROUND: Despite increased interest in non-invasive arterial pressure monitoring, the majority of commercially available technologies have failed to satisfy the limits established for the validation of automatic arterial pressure monitoring by the Association for the Advancement of Medical Instrumentation (AAMI). According to the ANSI/AAMI/ISO 81060-2:2013 standards, the group-average accuracy and precision are defined as acceptable if bias is not greater than 5 mmHg and standard deviation is not greater than 8 mmHg. In this study, these standards are used to evaluate the CareTaker® (CT) device, a device measuring continuous non-invasive blood pressure via a pulse contour algorithm called Pulse Decomposition Analysis. METHODS: A convenience sample of 24 patients scheduled for major abdominal surgery were consented to participate in this IRB approved pilot study. Each patient was monitored with a radial arterial catheter and CT using a finger cuff applied to the contralateral thumb. Hemodynamic variables were measured and analyzed from both devices for the first thirty minutes of the surgical procedure including the induction of anesthesia. The mean arterial pressure (MAP), systolic and diastolic blood pressures continuously collected from the arterial catheter and CT were compared. Pearson correlation coefficients were calculated between arterial catheter and CT blood pressure measurements, a Bland-Altman analysis, and polar and 4Q plots were created. RESULTS: The correlation of systolic, diastolic, and mean arterial pressures were 0.92, 0.86, 0.91, respectively (p < 0.0001 for all the comparisons). The Bland-Altman comparison yielded a bias (as measured by overall mean difference) of -0.57, -2.52, 1.01 mmHg for systolic, diastolic, and mean arterial pressures, respectively with a standard deviation of 7.34, 6.47, 5.33 mmHg for systolic, diastolic, and mean arterial pressures, respectively (p < 0.001 for all comparisons). The polar plot indicates little bias between the two methods (90%/95% CI at 31.5°/52°, respectively, overall bias = 1.5°) with only a small percentage of points outside these lines. The 4Q plot indicates good concordance and no bias between the methods. CONCLUSIONS: In this study, blood pressure measured using the non-invasive CT device was shown to correlate well with the arterial catheter measurements. Larger studies are needed to confirm these results in more varied settings. Most patients exhibited very good agreement between methods. Results were well within the limits established for the validation of automatic arterial pressure monitoring by the AAMI.

The number of injections does not influence absorption of bupivacaine after cervical plexus block for carotid endarterectomy.

STUDY OBJECTIVE: To investigate the efficacy and kinetics of bupivacaine when used for deep cervical plexus block (CPB), using either a single-injection or multiple-injections technique. DESIGN: Prospective, randomized, double-blind study. SETTING: Operating room of a university hospital. PATIENTS: Twenty-four adult patients (16 men, 8 women) scheduled for carotid endarterectomy. INTERVENTIONS: Patients were randomly assigned to receive CPB either by a single injection or after 3 injections. Patients in the multiple-injections group received a total dose of 15 mL of 0.5% bupivacaine (5 mL each deposited at C2, C3, and C4 over 2 minutes). Patients in the single-injection group received a single 15-mL injection of 0.5% bupivacaine. After the deep CPB, a superficial CPB was performed with 20 mL of 0.5% bupivacaine in all patients. MEASUREMENTS: An anesthesiologist and a surgeon graded the success of the block. Arterial plasma concentrations of bupivacaine were measured using liquid chromatography-mass spectroscopy. MAIN RESULTS: No significant differences were seen between the 2 groups with respect to the mean peak concentration of bupivacaine (single injection 2314 +/- 1385 ng/mL vs multiple injections 2255 +/- 1105 ng/mL) or time to reach the maximal concentration (time to maximum concentration [single injection 12.1 +/- 7.2 minutes vs multiple injections 12.5 +/- 3.9 minutes]). Furthermore, there were no significant differences in mean block scores between the single-injection and the multiple-injections groups, evaluated either by the anesthesiologists or the surgeon. CONCLUSIONS: The results of this study showed that the absorption of bupivacaine is independent of the number of injections after CPB, and that anesthesia for carotid endarterectomy may be accomplished successfully using either technique.

Simulation-based education with deliberate practice may improve intraoperative handoff skills: a pilot study.

STUDY OBJECTIVE: To examine the results of simulation-based education with deliberate practice on the acquisition of handoff skills by studying resident intraoperative handoff communication performances. DESIGN: Preinvention and postintervention pilot study. SETTING: Simulated operating room of a university-affiliated hospital. MEASUREMENTS: Resident handoff performances during 27 encounters simulating elective surgery were studied. Ten residents (CA-1, CA-2, and CA-3) participated in a one-day simulation-based handoff course. Each resident repeated simulated handoffs to deliberately practice with an intraoperative handoff checklist. One year later, 7 of the 10 residents participated in simulated intraoperative handoffs. All handoffs were videotaped and later scored for accuracy by trained raters. A handoff assessment tool was used to characterize the type and frequency of communication failures. The percentage of handoff errors and omissions were compared before simulation and postsimulation-based education with deliberate practice and at one year following the course. MAIN RESULTS: Initially, the overall communication failure rate, defined as the percentage of handoff omissions plus errors, was 29.7%. After deliberate practice with the intraoperative handoff checklist, the communication failure rate decreased to 16.8%, and decreased further to 13.2% one year after the course. CONCLUSIONS: Simulation-based education using deliberate practice may result in improved intraoperative handoff communication and retention of skills at one year.

Using Simulation Education With Deliberate Practice to Teach Leadership and Resource Management Skills to Senior Resident Code Leaders.

BACKGROUND: Cardiopulmonary arrests are rare, high-stakes events that benefit from using crisis resource management (CRM). Simulation-based education with deliberate practice can promote skill acquisition. OBJECTIVE: We assessed whether using simulation-based education to teach CRM would lead to improved performance, compared to a lecture format. METHODS: We tested third-year internal medicine residents in simulated code scenarios. Participants were randomly assigned to simulation-based education with deliberate practice (SIM) group or lecture (LEC) group. We created a checklist of CRM critical actions (which includes announcing the diagnosis, asking for help/suggestions, and assigning tasks), and reviewed videotaped performances, using a checklist of skills and communications patterns to identify CRM skills and communication efforts. Subjects were tested in simulated code scenarios 6 months after the initial assessment. RESULTS: At baseline, all 52 subjects recognized distress, and 92% (48 of 52) called for help. Seventy-eight percent (41 of 52) did not succeed in resuscitating the simulated patient or demonstrate the CRM skills. After intervention, both groups (n  =  26 per group) improved. All SIM subjects announced the diagnosis compared to 65% LEC subjects (17 of 26, P  =  .01); 77% (20 of 26) SIM and 19% (5 of 26) LEC subjects asked for suggestions (P < .001); and 100% (26 of 26) SIM and 27% (7 of 26) LEC subjects assigned tasks (P < .001). CONCLUSIONS: The SIM intervention resulted in significantly improved team communication and cardiopulmonary arrest management. During debriefing, participants acknowledged the benefit of the SIM sessions.

Case report: vibration response imaging findings following inadvertent esophageal intubation.

PURPOSE: We describe the effect that inadvertent esophageal intubation has on the images and on the vibration distribution of vibration response imaging (VRI). CLINICAL FEATURES: Vibration response imaging (VRI) is a novel, non-invasive, computer-based technology that measures vibration energy of lung sounds during respiration and displays regional intensity, in both visual and graphic format. Vibration response images, obtained prior to tracheal intubation (spontaneous breathing) and during endotracheal ventilation using a controlled mode, resulted in evenly distributed vibrations throughout the patient's lungs. During inadvertent esophageal ventilation, however, the majority of vibrations were detected in the upper regions of the image, compared to those of the lower (60% vs 8%, respectively). During spontaneous breathing and endotracheal ventilation, the midclavicular column of sensors, located over the centre of each lung, detected more vibrations compared to either the medial or the axillary column of sensors. During inadvertent esophageal ventilation, more vibrations were detected by the medial column of sensors (nearest to the midline/esophagus); and fewer were detected by the sensors that were positioned more laterally. CONCLUSION: This report illustrates the potential for a visual image of distribution of lung vibration energy to differentiate endotracheal intubation from inadvertent esophageal intubation.