Storylines for unprecedented heatwaves based on ensemble boosting.

Recent temperature extremes have shattered previously observed records, reaching intensities that were inconceivable before the events. Could the possibility of an event with such unprecedented intensity as the 2021 Pacific Northwest heatwave have been foreseen, based on climate model information available before the event? Could the scientific community have quantified its potential intensity based on the current generation of climate models? Here, we demonstrate how an ensemble boosting approach can be used to generate physically plausible storylines of a heatwave hotter than observed in the Pacific Northwest. We also show that heatwaves of much greater intensities than ever observed are possible in other locations like the Greater Chicago and Paris regions. In order to establish confidence in storylines of 'black swan'-type events, different lines of evidence need to be combined along with process understanding to make this information robust and actionable for stakeholders.

Endotracheal Tube Kinking in the Prone Position during Pediatric Neurosurgery: A Case Report.

BACKGROUND: The prone position presents several concerns for the pediatric anesthesiologist, such as prevention of pressure related injuries, avoidance of undetected line infiltration, proper airway securement to inhibit unanticipated extubation, and limited access to the patient in critical events. However, the possibility of endotracheal tube kinking in pediatric patients is rarely discussed in the multitude of concerns about prone procedures. Here, we present a case report detailing the anesthetic management of a patient that experienced endotracheal tube kinking in the prone position during a posterior fossa mass resection. Our conclusion is that pediatric anesthesiologists must be cognizant of the possibility of endotracheal tube kinking in patients who are undergoing procedures in the prone position with significant neck flexion. We recommend using either an appropriately sized reinforced endotracheal tube or a nasotracheal intubation to decrease the potential of intraoperative tube kinking.

Congenital Central Hypoventilation Syndrome: Optimizing Care with a Multidisciplinary Approach.

Congenital central hypoventilation syndrome (CCHS) is a rare genetic disorder affecting respiratory control and autonomic nervous system function caused by variants in the paired-like homeobox 2B (PHOX2B) gene. Although most patients are diagnosed in the newborn period, an increasing number of patients are presenting later in childhood, adolescence, and adulthood. Despite hypoxemia and hypercapnia, patients do not manifest clinical features of respiratory distress during sleep and wakefulness. CCHS is a lifelong disorder. Patients require assisted ventilation throughout their life delivered by positive pressure ventilation via tracheostomy, noninvasive positive pressure ventilation, and/or diaphragm pacing. At different ages, patients may prefer to change their modality of assisted ventilation. This requires an individualized and coordinated multidisciplinary approach. Additional clinical features of CCHS that may present at different ages and require periodic evaluations or interventions include Hirschsprung's disease, gastrointestinal dysmotility, neural crest tumors, cardiac arrhythmias, and neurodevelopmental delays. Despite an established PHOX2B genotype and phenotype correlation, patients have variable and heterogeneous clinical manifestations requiring the formulation of an individualized plan of care based on collaboration between the pulmonologist, otolaryngologist, cardiologist, anesthesiologist, gastroenterologist, sleep medicine physician, geneticist, surgeon, oncologist, and respiratory therapist. A comprehensive multidisciplinary approach may optimize care and improve patient outcomes. With advances in CCHS management strategies, there is prolongation of survival necessitating high-quality multidisciplinary care for adults with CCHS.

Comparison of different dosage regimes of epsilon aminocaproic acid on blood loss in children undergoing craniosynostosis surgery.

BACKGROUND: Open cranial vault reconstruction is frequently performed for craniosynostosis. These procedures often involve high volume blood loss that requires blood transfusion. Antifibrinolytics have been shown to decrease blood loss during these procedures but the optimal dose that maximizes benefits is not known. AIMS: The primary aim was to evaluate the differences in calculated blood loss between a high infusion rate (40 mg/kg/h) and a low infusion rate (≤30 mg/kg/h) of epsilon aminocaproic acid after a 100 mg/kg loading dose. Secondary aims were to determine if a high infusion rate of epsilon aminocaproic acid was associated with decreased packed red cell transfusion volume and to determine the factors associated with blood loss. METHODS: This was a retrospective study of children who underwent open cranial vault reconstruction. Using an electronic medical record, we identified patients that fit the inclusion criteria. Demographic, laboratory, transfusion, and perioperative data were collected and statistical analysis was performed. RESULTS: Fifty-three patients were included into the study with twenty-three receiving higher infusion rate (40 mg/kg/h) epsilon aminocaproic acid. There was a 14.3 mL/kg (95% CI 6.6-23.9) decrease in calculated blood loss in the high-dose cohort. CONCLUSION: An EACA bolus of 100 mg/kg followed by an infusion of 40 mg/kg was associated with a lower calculated blood loss compared to the group who received 100 mg/kg EACA and ≤ 30 mg/kg infusion.

Bimodal analgesia vs fentanyl in pediatric patients undergoing bilateral myringotomy and tympanostomy tube placement: a propensity matched cohort study.

STUDY OBJECTIVE: Bilateral myringotomy and tympanostomy tube placement (BMT) is one of the most frequently performed pediatric outpatient procedures with 667,000 children receiving tympanostomy tubes annually. Because of this high volume, discovering the ideal analgesic regimen may lead to decreased overall postanesthesia care unit (PACU) costs while increasing patient and parent satisfaction. The purpose of this study is to determine if there is any benefit in supplementing intranasal (IN) fentanyl with intramuscular (IM) ketorolac with regard to immediate recovery characteristics. DESIGN: Retrospective, cohort study. SETTING: University-affiliated teaching hospital. PATIENTS: One thousand one hundred forty American Society of Anesthesiologists physical status 1 and 2 pediatric patients scheduled for BMT. INTERVENTIONS: No interventions were performed. MEASUREMENTS: A propensity matched cohort of pediatric patients who underwent BMT at Vanderbilt Children's Hospital from 2011 to 2014 was analyzed. The authors compared PACU recovery time, rescue analgesic administration, maximal PACU pain scores, and maximal PACU agitation scores between subgroups of patients given either IN fentanyl and IM ketorolac or IN fentanyl alone intraoperatively. MAIN RESULTS: After adjusting for patient demographics and fentanyl dose, the fentanyl/ketorolac group received rescue analgesics 4.7% (95% confidence interval [CI], 2.0%-7.5%) less often, displayed moderate to severe pain 4.7% (95% CI, 1.5%-8.0%) less often, and experienced emergence agitation 3.6% (95% CI, 1.5%-5.8%) less often than patients in the fentanyl-only group. This corresponded to a relative risk reduction of 127%, 76%, and 200%, respectively. CONCLUSIONS: Based on our retrospective analysis, adding IM ketorolac to IN fentanyl may be beneficial to pediatric patients undergoing BMT. However, these results should be confirmed with a prospective, double-blinded, randomized study.

Use of blood-sparing surgical techniques and transfusion algorithms: association with decreased blood administration in children undergoing primary open craniosynostosis repair.

OBJECT Craniofacial reconstruction surgery (CFR) is often associated with significant blood loss, coagulopathy, and perioperative blood transfusion. Due to transfusion risks, many different approaches have been used to decrease allogeneic blood transfusion for these patients during the perioperative period. Protocols have decreased blood administration during the perioperative period for many types of surgeries. The object of this study was to determine if a protocol involving blood-sparing surgical techniques and a transfusion algorithm decreased intraoperative blood transfusion and blood loss. METHODS A protocol using transfusion algorithms and implementation of blood-sparing surgical techniques for CFR was implemented at Vanderbilt University on January 1, 2013. Following Institutional Review Board approval, blood loss and transfusion data were gathered retrospectively on all children undergoing primary open CFR, using the protocol, for the calendar year 2013. This postprotocol cohort was compared with a preprotocol cohort, which consisted of all children undergoing primary open CFR during the previous calendar year, 2012. RESULTS There were 41 patients in the preprotocol and 39 in the postprotocol cohort. There was no statistical difference between the demographics of the 2 groups. When compared with the preprotocol cohort, intraoperative packed red blood cell transfusion volume decreased from 36.9 ± 21.2 ml/kg to 19.2 ± 10.9 ml/kg (p = 0.0001), whereas fresh-frozen plasma transfusion decreased from 26.8 ± 25.4 ml/kg to 1.5 ± 5.7 ml/kg (p < 0.0001) following implementation of the protocol. Furthermore, estimated blood loss decreased from 64.2 ± 32.4 ml/kg to 52.3 ± 33.3 ml/kg (p = 0.015). Use of fresh-frozen plasma in the postoperative period also decreased when compared with the period before implementation of the protocol. There was no significant difference in morbidity and mortality between the 2 groups. CONCLUSIONS The results of this study suggested that using a multidisciplinary protocol consisting of transfusion algorithms and implementation of blood-sparing surgical techniques during major CFR in pediatric patients is associated with reduced intraoperative administration of blood product, without shifting the transfusion burden to the postoperative period.

Intraoperative optimization to decrease postoperative PRBC transfusion in children undergoing craniofacial reconstruction.

BACKGROUND: Craniofacial reconstructive surgery for craniosynostosis is associated with large blood loss and intraoperative transfusion. This blood loss may continue through the initial postoperative period, potentially resulting in transfusion postoperatively. The purpose of this study is to determine if there is an association between any modifiable intraoperative factors and postoperative blood transfusion in this patient population. METHODS: A cohort of 55 pediatric patients who underwent primary craniofacial reconstruction at Vanderbilt Children's Hospital from January 1, 2013 to April 31, 2014 was analyzed. The authors analyzed 20 different demographic and perioperative variables for statistical associations with postoperative PRBC transfusion using multiple logistic regression with optimal models being selected by Bayesian model averaging. RESULTS: The optimal regression model only included initial PACU Hct as a predictor and showed a significant association between this variable and postoperative PRBC transfusion (odds ratio 0.69, 95% CI 0.55-0.87, P = 0.0016). Based on the average decrease in postoperative hematocrit (Hct) and the postoperative transfusion trigger, an initial PACU Hct threshold of 30 was calculated. In our patient sample, an initial PACU Hct above 30 was associated with a 50% decrease in the absolute risk of receiving a PRBC transfusion postoperatively. CONCLUSIONS: Based on this retrospective analysis, it may be justifiable to transfuse residual volume from previously exposed intraoperative PRBCs to a Hct above 30 to decrease the likelihood of subsequent blood transfusions from different donors in the postoperative period.

Elective change of surgeon during the OR day has an operationally negligible impact on turnover time.

STUDY OBJECTIVE: To compare turnover times for a series of elective cases with surgeons following themselves with turnover times for a series of previously scheduled elective procedures for which the succeeding surgeon differed from the preceding surgeon. DESIGN: Retrospective cohort study. SETTING: University-affiliated teaching hospital. MEASUREMENTS: The operating room (OR) statistical database was accessed to gather 32 months of turnover data from a large academic institution. Turnover time data for the same-surgeon and surgeon-swap groups were batched by month to minimize autocorrelation and achieve data normalization. Two-way analysis of variance (ANOVA) using the monthly batched data was performed with surgeon swapping and changes in procedure category as variables of turnover time. Similar analyses were performed using individual surgical services, hourly time intervals during the surgical day, and turnover frequency per OR as additional covariates to surgeon swapping. MAIN RESULTS: The mean (95% confidence interval [CI]) same-surgeon turnover time was 43.6 (43.2 - 44.0) minutes versus 51.0 (50.5 - 51.6) minutes for a planned surgeon swap (P < 0.0001). This resulted in a difference (95% CI) of 7.4 (6.8 - 8.1) minutes. The exact increase in turnover time was dependent on surgical service, change in subsequent procedure type, time of day when the turnover occurred, and turnover frequency. CONCLUSIONS: The investigated institution averages 2.5 cases per OR per day. The cumulative additional turnover time (far less than one hour per OR per day) for switching surgeons definitely does not allow the addition of another elective procedure if the difference could be eliminated. A flexible scheduling policy allowing surgeon swapping rather than requiring full blocks incurs minimal additional staffed time during the OR day while allowing the schedule to be filled with available elective cases.

Numerical and experimental simulation of the effect of long bone fracture healing stages on ultrasound transmission across an idealized fracture.

The effect of various stages of fracture healing on the amplitude of 200 kHz ultrasonic waves propagating along cortical bone plates and across an idealized fracture has been modeled numerically and experimentally. A simple, water-filled, transverse fracture was used to simulate the inflammatory stage. Next, a symmetric external callus was added to represent the repair stage, while a callus of reducing size was used to simulate the remodeling stage. The variation in the first arrival signal amplitude across the fracture site was calculated and compared with data for an intact plate in order to calculate the fracture transmission loss (FTL) in decibels. The inclusion of the callus reduced the fracture loss. The most significant changes were calculated to occur from the initial inflammatory phase to the formation of a callus (with the FTL reducing from 6.3 to between 5.5 and 3.5 dB, depending on the properties of the callus) and in the remodeling phase where, after a 50% reduction in the size of the callus, the FTL reduced to between 2.0 and 1.3 dB. Qualitatively, the experimental results follow the model predictions. The change in signal amplitude with callus geometry and elastic properties could potentially be used to monitor the healing process.

Modelling the effects of different fracture geometries and healing stages on ultrasound signal loss across a long bone fracture.

The effect on the signal amplitude of ultrasonic waves propagating along cortical bone plates was modelled using a 2D Finite Difference code. Different healing stages, represented by modified fracture geometries were introduced to the plate model. A simple transverse and oblique fracture filled with water was introduced to simulate the inflammatory stage. Subsequently, a symmetric external callus surrounding a transverse fracture was modelled to represent an advanced stage of healing. In comparison to the baseline (intact plate) data, a large net loss in signal amplitude was produced for the simple transverse and oblique cases. Changing the geometry to an external callus with different mechanical properties caused the net loss in signal amplitude to reduce significantly. This relative change in signal amplitude as the geometry and mechanical properties of the fracture site change could potentially be used to monitor the healing process.

Empirical angle-dependent Biot and MBA models for acoustic anisotropy in cancellous bone.

The Biot and the modified Biot-Attenborough (MBA) models have been found useful to understand ultrasonic wave propagation in cancellous bone. However, neither of the models, as previously applied to cancellous bone, allows for the angular dependence of acoustic properties with direction. The present study aims to account for the acoustic anisotropy in cancellous bone, by introducing empirical angle-dependent input parameters, as defined for a highly oriented structure, into the Biot and the MBA models. The anisotropy of the angle-dependent Biot model is attributed to the variation in the elastic moduli of the skeletal frame with respect to the trabecular alignment. The angle-dependent MBA model employs a simple empirical way of using the parametric fit for the fast and the slow wave speeds. The angle-dependent models were used to predict both the fast and slow wave velocities as a function of propagation angle with respect to the trabecular alignment of cancellous bone. The predictions were compared with those of the Schoenberg model for anisotropy in cancellous bone and in vitro experimental measurements from the literature. The angle-dependent models successfully predicted the angular dependence of phase velocity of the fast wave with direction. The root-mean-square errors of the measured versus predicted fast wave velocities were 79.2 m s(-1) (angle-dependent Biot model) and 36.1 m s(-1) (angle-dependent MBA model). They also predicted the fact that the slow wave is nearly independent of propagation angle for angles about 50 degrees , but consistently underestimated the slow wave velocity with the root-mean-square errors of 187.2 m s(-1) (angle-dependent Biot model) and 240.8 m s(-1) (angle-dependent MBA model). The study indicates that the angle-dependent models reasonably replicate the acoustic anisotropy in cancellous bone.

An in vitro study of ultrasound signal loss across simple fractures in cortical bone mimics and bovine cortical bone samples.

Measurements have been performed on Sawbones and bovine cortical bone samples at 200 kHz using an axial transmission technique to investigate the factors that determine how ultrasonic waves propagate across a simulated fracture. The peak amplitude of the first arrival signal (FAS) was studied. Results taken from intact specimens were compared with those produced when a simple transverse fracture was introduced. These fracture simulation experiments were found to be consistent with Finite Difference modelling of the experimental conditions. The peak amplitude showed a characteristic variation across the fracture caused by interference between reradiated and scattered/diffracted waves at the fracture site and a net Fracture Transmission Loss (FTL). For small fracture gaps, the change in amplitude was sensitive to the presence of the fracture. This sensitivity suggests that this parameter could be a good quantitative indicator for the fracture healing process assuming the relative change in this parameter brought about by healing is measurable.

Ultrasonic propagation in cortical bone mimics.

Understanding the velocity and attenuation characteristics of ultrasonic waves in cortical bone and bone mimics is important for studies of osteoporosis and fractures. Three complementary approaches have been used to help understand the ultrasound propagation in cortical bone and bone mimics immersed in water, which is used to simulate the surrounding tissue in vivo. The approaches used were Lamb wave propagation analysis, experimental measurement and two-dimensional (2D) finite difference modelling. First, the water loading effects on the free plate Lamb modes in acrylic and human cortical bone plates were examined. This theoretical study revealed that both the S0 and S1 mode velocity curves are significantly changed in acrylic: mode jumping occurs between the S0 and S1 dispersion curves. However, in human cortical bone plates, only the S1 mode curve is significantly altered by water loading, with the S0 mode exhibiting a small deviation from the unloaded curve. The Lamb wave theory predictions for velocity and attenuation were then tested experimentally on acrylic plates using an axial transmission technique. Finally, 2D finite difference numerical simulations of the experimental measurements were performed. The predictions from Lamb wave theory do not correspond to the measured and simulated first arrival signal (FAS) velocity and attenuation results for acrylic and human cortical bone plates obtained using the axial transmission technique, except in very thin plates.

Energy and phase velocity considerations required for attenuation and velocity measurements of anisotropic composites.

Viscoelastic fibre-reinforced composite materials have a number of possible advantages for use in underwater acoustic applications. In order to exploit these materials it is important to be able to measure their complex stiffness matrix in order to determine their acoustic response. Ultrasonic transmission measurements on parallel-sided samples, employing broadband pulsed transducers at 2.25 MHz and an immersion method, have been used to determine the viscoelastic properties of a glass-reinforced composite with uniaxially aligned fibres. The composite measured was constructed from Cytecfiberite's CYCOM 919 E-glass. The theory of acoustic propagation in anisotropic materials shows that the direction of energy propagation is, in general, different from that given by Snell's Law. At 15 degrees incidence, Snell's Law implies a refracted angle of 40 +/- 2 degrees, whereas the energy direction is observed to be 70 +/- 2 degrees. Despite this, the experimental data indicates that the position of the receiving transducer has relatively little effect on the apparent phase velocity measured. The phase velocities measured at positions determined from the refracted angle and energy direction are 3647 and 3652 +/- 50 m s(-1), respectively. However, the amplitude of the received signal, and hence estimate of attenuation, is highly sensitive to the receiver position. This indicates that the acoustic Poynting vector must be considered in order to precisely determine the correct position of the receiving transducer for attenuation measurements. The beam displacement for a 17.6 mm sample at 15 degrees incidence is 9.5 and 40 mm by Snell's Law and Poynting's Theorem, respectively. Measured beam displacements have been compared with predictions derived from material stiffness coefficients. These considerations are important in recovering the complex stiffness matrix.

Comparison of finite element and heated disc models of tissue heating by ultrasound.

This paper compares different techniques used to model the heating caused by ultrasound (US) in a phantom containing a layer of bone mimic covered by agar gel. Results from finite element (FE) models are compared with those from two techniques based on the point-source solution to the bioheat transfer equation (BHTE): one in which the bone mimic is considered to be an absorbing disc of infinitesimal thickness and the other in which the region through which the US travels is considered to be a volume heat source. The FE results are also compared with experimental measurements. The results from the models differed by up to 40% compared with those from the FE model. Furthermore, for the intensity distribution considered, which corresponds to that in the focal zone of a single-element transducer, the top hat distribution predicts a temperature rise 1.8 times greater than that for a more realistic one based on measured values.