Supervised Machine-learning Predictive Analytics for Prediction of Postinduction Hypotension.

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Hypotension is a risk factor for adverse perioperative outcomes. Machine-learning methods allow large amounts of data for development of robust predictive analytics. The authors hypothesized that machine-learning methods can provide prediction for the risk of postinduction hypotension. METHODS: Data was extracted from the electronic health record of a single quaternary care center from November 2015 to May 2016 for patients over age 12 that underwent general anesthesia, without procedure exclusions. Multiple supervised machine-learning classification techniques were attempted, with postinduction hypotension (mean arterial pressure less than 55 mmHg within 10 min of induction by any measurement) as primary outcome, and preoperative medications, medical comorbidities, induction medications, and intraoperative vital signs as features. Discrimination was assessed using cross-validated area under the receiver operating characteristic curve. The best performing model was tuned and final performance assessed using split-set validation. RESULTS: Out of 13,323 cases, 1,185 (8.9%) experienced postinduction hypotension. Area under the receiver operating characteristic curve using logistic regression was 0.71 (95% CI, 0.70 to 0.72), support vector machines was 0.63 (95% CI, 0.58 to 0.60), naive Bayes was 0.69 (95% CI, 0.67 to 0.69), k-nearest neighbor was 0.64 (95% CI, 0.63 to 0.65), linear discriminant analysis was 0.72 (95% CI, 0.71 to 0.73), random forest was 0.74 (95% CI, 0.73 to 0.75), neural nets 0.71 (95% CI, 0.69 to 0.71), and gradient boosting machine 0.76 (95% CI, 0.75 to 0.77). Test set area for the gradient boosting machine was 0.74 (95% CI, 0.72 to 0.77). CONCLUSIONS: The success of this technique in predicting postinduction hypotension demonstrates feasibility of machine-learning models for predictive analytics in the field of anesthesiology, with performance dependent on model selection and appropriate tuning.

A retrospective study of opioid prescribing patterns at hospital discharge in surgical patients with obstructive sleep apnea.

PURPOSE: Obstructive sleep apnea (OSA) is a risk factor for complications with postoperative opioid use, and in those patients with known or suspected OSA, minimization of postoperative opioids is recommended. We hypothesize that despite these recommendations, surgical patients with known or suspected OSA are prescribed postoperative opioids at hospital discharge at similar doses to those without OSA. METHODS: This was a retrospective analysis of the electronic health records of surgical patients from 1 November 2016 to 30 April 2017 at a single academic institution. Patients with a known diagnosis of OSA or a STOP-Bang score ≥ 5 were compared with those without OSA for the amount of postoperative discharge opioid medication using multivariable linear regression. RESULTS: Of the 17,671 patients analyzed, 1,692 (9.6%) had known or suspected OSA with 1,450 (86%) of these patients discharged on opioid medications. Of the 15,979 patients without OSA, 12,273 (77%) were discharged on opioid medications. The total median [interquartile range (IQR)] oral morphine equivalents (OME) for all patients was 150 [0-338] mg and for patients with known or suspected OSA was 160 [0-450] mg, an unadjusted comparison showing an 18% difference in OME (95% confidence interval [CI], 3% to 35%; P = 0.02). The analysis, after adjusting for confounders, showed no significant difference in the amount of opioids prescribed to OSA or non-OSA patients (8% difference in total OME; 95% CI, -6% to 25%; P = 0.26). CONCLUSION: This study shows that surgical patients at risk for OSA or confirmed OSA are prescribed opioids at similar rates and doses upon discharge despite guidelines that recommend minimizing opioid use in OSA patients. These findings indicate a need to implement different strategies to reduce the prescription of opioids to patients with OSA.

Preoperative Evaluation Clinic Visit Is Associated with Decreased Risk of In-hospital Postoperative Mortality.

BACKGROUND: As specialists in perioperative medicine, anesthesiologists are well equipped to design and oversee the preoperative patient preparation process; however, the impact of an anesthesiologist-led preoperative evaluation clinic (PEC) on clinical outcomes has yet to be fully elucidated. The authors compared the incidence of in-hospital postoperative mortality in patients who had been evaluated in their institution's PEC before elective surgery to the incidence in patients who had elective surgery without being seen in the PEC. METHODS: A retrospective review of an administrative database was performed. There were 46 deaths from 64,418 patients (0.07%): 22 from 35,535 patients (0.06%) seen in PEC and 24 from 28,883 patients (0.08%) not seen in PEC. After propensity score matching, there were 13,964 patients within each matched set; there were 34 deaths (0.1%). There were 11 deaths from 13,964 (0.08%) patients seen in PEC and 23 deaths from 13,964 (0.16%) patients not seen in PEC. A subanalysis to assess the effect of a PEC visit on deaths as a result of failure to rescue (FTR) was also performed. RESULTS: A visit to PEC was associated with a reduction in mortality (odds ratio, 0.48; 95% CI, 0.22 to 0.96, P = 0.04) by comparison of the matched cohorts. The FTR subanalysis suggested that the proportion of deaths attributable to an unanticipated surgical complication was not significantly different between the two groups (P = 0.141). CONCLUSIONS: An in-person assessment at the PEC was associated with a reduction in in-hospital mortality. It was difficult to draw conclusions about whether a difference exists in the proportion of FTR deaths between the two cohorts due to small sample size.

Despite differences in cytosolic calcium regulation, lidocaine toxicity is similar in adult and neonatal rat dorsal root ganglia in vitro.

BACKGROUND: Neuraxial local anesthetics may have neurological complications thought to be due to neurotoxicity. A primary site of action of local anesthetics is the dorsal root ganglia (DRG) neuron. Physiologic differences have been noted between young and adult DRG neurons; hence, the authors examined whether there were any differences in lidocaine-induced changes in calcium and lidocaine toxicity in neonatal and adult rat DRG neurons. METHODS: DRG neurons were cultured from postnatal day 7 (P7) and adult rats. Lidocaine-induced changes in cytosolic calcium were examined with the calcium indicator Fluo-4. Cells were incubated with varying concentrations of lidocaine and examined for viability using calcein AM and ethidium homodimer-1 staining. Live imaging of caspase-3/7 activation was performed after incubation with lidocaine. RESULTS: The mean KCl-induced calcium transient was greater in P7 neurons (P < 0.05), and lidocaine significantly inhibited KCl-induced calcium responses in both ages (P < 0.05). Frequency distribution histograms of KCl-evoked calcium increases were more heterogeneous in P7 than in adult neurons. With lidocaine, KCl-induced calcium transients in both ages became more homogeneous but remained different between the groups. Interestingly, cell viability was decreased by lidocaine in a dose-dependent manner similarly in both ages. Lidocaine treatment also activated caspase-3/7 in a dose- and time-dependent manner similarly in both ages. CONCLUSIONS: Despite physiological differences in P7 and adult DRG neurons, lidocaine cytotoxicity is similar in P7 and adult DRG neurons in vitro. Differences in lidocaine- and KCl-evoked calcium responses suggest the similarity in lidocaine cytotoxicity involves other actions in addition to lidocaine-evoked effects on cytosolic calcium responses.

Regional anesthesia improves outcome after distal radius fracture fixation over general anesthesia.

OBJECTIVE: To compare the efficacy of anesthetic type on clinical outcomes after operative treatment of distal radius fractures. DESIGN: Retrospective review of prospectively collected data. SETTING: Academic medical center. PATIENTS: One hundred eighty-seven patients with a distal radius fracture (OTA type 23) were identified within a registry of 600 patients. INTERVENTION: Patients with operative distal radius fractures underwent open reduction and internal fixation with a volarly applied plate and screws under regional or general anesthesia. MAIN OUTCOME MEASUREMENTS: Clinical, radiographic, and patient-based functional outcomes were recorded at routine postoperative intervals. Complications were recorded. RESULTS: One hundred eighty-seven patients met inclusion criteria and had a minimum of 1-year follow-up. There were no differences between the groups with regard to patient demographics or fracture types treated. At both 3 and 6 months post surgery, pain was diminished among those patients who received a regional block. Wrist and finger range of motion for patients who received regional versus general anesthesia was improved at all follow-up points. Patients who received regional anesthesia also had higher functional scores as measured by the Disabilities of the Arm, Shoulder and Hand at 3 months (P = 0.04) and 6 months (P = 0.02). CONCLUSION: Patients who are candidates should be offered regional anesthesia when undergoing repair of a displaced distal radius fracture. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Three partial-task simulators for teaching ultrasound-guided regional anesthesia.

Simulation-based training is becoming an accepted tool for educating physicians before direct patient care. As ultrasound-guided regional anesthesia (UGRA) becomes a popular method for performing regional blocks, there is a need for learning the technical skills associated with the technique. Although simulator models do exist for learning UGRA, they either contain food and are therefore perishable or are not anatomically based. We developed 3 sonoanatomically based partial-task simulators for learning UGRA: an upper body torso for learning UGRA interscalene and infraclavicular nerve blocks, a femoral manikin for learning UGRA femoral nerve blocks, and a leg model for learning UGRA sciatic nerve blocks in the subgluteal and popliteal areas.

In vitro antiseptic effects on viability of neuronal and Schwann cells.

BACKGROUND AND OBJECTIVE: Chlorhexidine is recommended by several anesthesiology societies for antisepsis before regional anesthesia, but there is concern it may be neurotoxic. We evaluated the cytotoxicity of chlorhexidine and povidone-iodine in human neuronal and rat Schwann cells. METHODS: Human SH-SY5Y neuroblastoma and rat RSC96 Schwann cells were incubated with serial dilutions of 2% chlorhexidine gluconate and 10% povidone-iodine for 10 minutes, and viability was assessed with the MTT colorimetry assay and a fluorescent assay using calcein and ethidium. Cell morphology during antiseptic incubation was observed under light microscopy. To estimate the amount of antiseptic a needle carries through tissues, tritium radioactivity was measured in an animal injection model. RESULTS: Chlorhexidine at all tested concentrations significantly decreased viability compared with controls in both SH-SY5Y and RSC96 cells (P < 0.001). Povidone-iodine significantly decreased viability for both cells at concentrations of 0.2% or higher (P < 0.001). At the same dilutions of 1:200, 1:150, and 1:100, chlorhexidine was more cytotoxic than povidone-iodine for both cells (P< 0.001). During chlorhexidine treatment, both cell types became rounded and shriveled. Less dramatic changes were observed with povidone-iodine. In the injection model, 1.75% ± 1.29% of the maximum amount of radioactive contamination was carried through tissues. CONCLUSIONS: Chlorhexidine gluconate and povidone-iodine were cytotoxic to SH-SY5Y (neuronal) and RSC96 (Schwann) cells. Chlorhexidine was more potent than povidone-iodine at more dilute concentrations. However, the toxicity of the two was not different at concentrations used clinically. When using either of these agents for antisepsis before regional anesthesia, it is prudent to allow adequate drying time after application.

An unusual preinduction arrhythmia resulting from the presence of a Mahaim fiber.

A potentially life-threatening arrhythmia appeared on the preinduction electrocardiogram of an asymptomatic young woman prior to spine surgery. The patient was evaluated by electrophysiology and had a rare accessory pathway, a Mahaim Fiber.

Ensuring appropriate timing of antimicrobial prophylaxis.

BACKGROUND: Delivery of intravenous antibiotic prophylaxis within one hour prior to surgical incision is considered important in helping to decrease the incidence of surgical site infections, but methods to ensure compliance have not been established. METHODS: All patients at our institution are subjected to a surgical "time-out" protocol to prevent wrong-site surgery. During a seven-week period, all patients undergoing spine surgery, total hip arthroplasty, or total knee arthroplasty had another safety initiative, that of ensuring that prophylactic intravenous antibiotics were administered at least one hour prior to incision, "piggybacked" onto our existing time-out verification checklist. In addition, we compared compliance during the study period with compliance during a three-month period prior to institution of this protocol and compliance for eighteen months after institution of this protocol. RESULTS: The average time (and standard deviation) between the antibiotic administration and the incision was 26 +/- 12 minutes for all patients. The protocol was effective in ensuring antibiotic administration at the optimal time to 316 (99.1%) of the 319 patients. Analysis of a group of forty patients who had undergone total hip or knee replacement during the three months prior to the beginning of the study demonstrated a compliance rate of 65%. The difference between this baseline compliance rate and the rate during the study period was significant (p < 0.0001). The compliance rate was 97% for 160 patients who underwent similar procedures during the eighteen months after completion of the study. Independent audits demonstrated continuation of the significantly better compliance with timing of antibiotic prophylaxis for patients undergoing total hip and knee arthroplasty since the implementation of the protocol in our institution. CONCLUSIONS: Piggybacking of verification of prophylactic antibiotic administration onto the wrong-site-surgery time-out protocol is an effective, cost-free, and easy-to-adopt method to ensure compliance with appropriate timing of prophylactic antibiotics.

Case series: Septa can influence local anesthetic spread during infraclavicular brachial plexus blocks.

PURPOSE: To ultrasonically identify the presence of septae within the neurovascular sheath and to assess their effect on local anesthetic spread when performing infraclavicular brachial plexus blocks. CLINICAL FEATURES: Thirty ASA status I and II patients scheduled for minor hand surgeries were enrolled in the study. Ultrasound guided infraclavicular brachial plexus blocks were performed on 28 patients. The images of the local anesthetic spread and the effect of the septum within the neurovascular sheath were analyzed. Septae were present in four of six patients where unilateral local anesthetic spread was seen. Septae were not visualized in the 22 patients with unrestricted local anesthetic spread after the initial injection. All 28 patients underwent their planned operations successfully with adequate anesthesia. CONCLUSIONS: Our study shows that the presence of septae within the neurovascular sheath may influence the pattern of local anesthetic spread associated with the infraclavicular approach to brachial plexus blocks.

Surface stimulation to determine needle direction and angle when performing an infraclavicular brachial plexus block.

The infraclavicular approach to the brachial plexus is a safe and reliable technique for surgery of the upper extremity. When performing the block, the anesthesiologist must appreciate three variables: needle direction, needle angle to the chest wall, and needle depth. Surface stimulation is an easy technique that can reliably predict both needle direction and needle angle.

Safety and efficacy of the infraclavicular nerve block performed at low current.

It has recently been suggested that peripheral nerve or plexus blocks performed with the use of a nerve stimulator at low currents (<0.5 mA) may result in neurologic damage. We studied the infraclavicular nerve block, performed with the use of a nerve stimulator and an insulated needle, in a prospective evaluation of efficacy and safety. During a one-year period, 248 patients undergoing infraclavicular nerve block were evaluated for block success rate and incidence of neurologic complication. All blocks were performed with the use of a nerve stimulator and an insulated needle at < or =0.3 mA. Success rate was 94%, which increased to 96% with surgical infiltration of local anesthetic. There were no intraoperative or immediate postoperative complications noted. After one week, only one patient had a neurologic complaint, and this was surgically related, referable to surgery performed on the radial nerve. We conclude that infraclavicular nerve blocks performed at low currents (< or =0.3 mA) are safe and effective.

Smallpox in the 21st century.

The viral disease, smallpox, was well known through the end of the 20th Century. Because it has been eradicated from natural populations, the present clinical experience with managing the disease is limited. Similarly, research in the pathophysiology, treatment, and prevention of the disease has recently become a priority. Concerns regarding smallpox as a weapon of bioterrorism have led to the implementation of a new prophylactic vaccine program, a renewal in variola vaccine research, and treatment regimens against variola infection.