Reprogramming of Tumor-reactive Tumor-infiltrating Lymphocytes to Human-induced Pluripotent Stem Cells

Tumor-infiltrating lymphocytes (TIL) that can recognize and kill tumor cells have curative potential in subsets of patients treated with adoptive cell transfer (ACT). However, lack of TIL therapeutic efficacy in many patients may be due in large part to a paucity of tumor-reactive T cells in TIL and the exhausted and terminally differentiated status of those tumor-reactive T cells. We sought to reprogram exhausted TIL that possess T-cell receptors (TCR) specific for tumor antigens into induced pluripotent stem cells (iPSC) to rejuvenate them for more potent ACT. We first attempted to reprogram tumor neoantigen-specific TIL by αCD3 Ab prestimulation which resulted in failure of establishing tumor-reactive TIL-iPSCs, instead, T cell-derived iPSCs from bystander T cells were established. To selectively activate and enrich tumor-reactive T cells from the heterogenous TIL population, CD8⁺ PD-1⁺ 4-1BB⁺ TIL population were isolated after coculture with autologous tumor cells, followed by direct reprogramming into iPSCs. TCR sequencing analysis of the resulting iPSC clones revealed that reprogrammed TIL-iPSCs encoded TCRs that were identical to the pre-identified tumor-reactive TCRs found in minimally cultured TIL. Moreover, reprogrammed TIL-iPSCs contained rare tumor antigen-specific TCRs, which were not detectable by TCR sequencing of the starting cell population. Thus, reprogramming of PD-1⁺ 4-1BB⁺ TIL after coculture with autologous tumor cells selectively generates tumor antigen-specific TIL-iPSCs, and is a distinctive method to enrich and identify tumor antigen-specific TCRs of low frequency from TIL.

SIGNIFICANCE

Reprogramming of TIL into iPSC holds great promise for the future treatment of cancer due to their rejuvenated nature and the retention of tumor-specific TCRs. One limitation is the lack of selective and efficient methods for reprogramming tumor-specific T cells from polyclonal TIL. Here we addressed this limitation and present a method to efficiently reprogram TIL into iPSC colonies carrying diverse tumor antigen reactive TCR recombination.

Self-organized yolk sac-like organoids allow for scalable generation of multipotent hematopoietic progenitor cells from induced pluripotent stem cells

Although the differentiation of human induced pluripotent stem cells (hiPSCs) into various types of blood cells has been well established, approaches for clinical-scale production of multipotent hematopoietic progenitor cells (HPCs) remain challenging. We found that hiPSCs cocultured with stromal cells as spheroids (hematopoietic spheroids [Hp-spheroids]) can grow in a stirred bioreactor and develop into yolk sac-like organoids without the addition of exogenous factors. Hp-spheroid-induced organoids recapitulated a yolk sac-characteristic cellular complement and structures as well as the functional ability to generate HPCs with lympho-myeloid potential. Moreover, sequential hemato-vascular ontogenesis could also be observed during organoid formation. We demonstrated that organoid-induced HPCs can be differentiated into erythroid cells, macrophages, and T lymphocytes with current maturation protocols. Notably, the Hp-spheroid system can be performed in an autologous and xeno-free manner, thereby improving the feasibility of bulk production of hiPSC-derived HPCs in clinical, therapeutic contexts.

Carbon Dioxide Embolism Resulting From Liver Laceration During Peritoneal Optical Trocar Entry

Venous air emboli have been reported to occur in numerous settings, including trauma, various surgical procedures, both laparoscopic and radiologically, and even idiopathically. In this case study, a liver laceration was made during a robot-assisted left colectomy and colostomy in a 69-year-old female resulting in air embolism during insufflation. A drop in end-tidal CO₂ was noted and the patient went into immediate cardiac arrest. Adequate pressure was applied and over-suturing of the liver laceration was made with reverse Trendelenburg positioning during the administration of cardiopulmonary resuscitation (CPR) for approximately one minute. The patient completed an open hemicolectomy the following day and made a complete recovery. Preventative and intraoperative measures to prevent further recurrences of venous air emboli are discussed.

Pancreatic insufficiency following pancreatectomy: Does underlying tumor syndrome confer a greater risk?

BACKGROUND

The risk of postoperative pancreatic exocrine insufficiency (PPEI) is unknown in patients with multiple endocrine neoplasia type I (MEN1) and von Hippel-Lindau (VHL) who require resection of pancreatic neuroendocrine tumors (PNETs).

METHODS

A retrospective review of patients who underwent resection of PNETs at the National Institutes of Health from 2007 to 2019 was performed.

RESULTS

Our cohort included 82 patients (VHL n = 25, MEN1 n = 20, sporadic n = 37), 6 of whom developed PPEI. While VHL compared to all non-VHL patients (p = 0.046), non-functional PNETs (p = 0.050), and pancreaticoduodenectomy (PD) (p=<0.001) were associated with higher rates of PPEI on univariate analysis, only PD was found to be an independent predictor of PPEI on multivariate analysis (OR 14.43, 95% CI 1.43-145.8, p = 0.024).

CONCLUSIONS

The rate of PPEI in patients with hereditary tumor syndromes was similar to that of sporadic PNETs. PD was independently associated with PPEI, and this increased risk should be included in preoperative counseling.

Twenty-five-Year Follow-up of a Prospective Randomized Trial Comparing Preoperative Versus Postoperative FLAC/Granulocyte Colony-Stimulating Factor Chemotherapy for Stage II Breast Cancer

BACKGROUND

Preoperative chemotherapy is important in the management of women with breast cancer, with the ability to downstage the breast primary tumor and axillary lymph nodes. Long-term studies are needed to identify late toxicities, recurrence patterns, and equivalency with postoperative chemotherapy for recurrence-free survival (RFS) and overall survival (OS).

PATIENTS AND METHODS

We conducted a single-institution prospective randomized control trial comparing preoperative or postoperative fluorouracil, leucovorin calcium, doxorubicin, and cyclophosphamides/granulocyte colony-stimulating factor chemotherapy for women with untreated clinical stage II (T1N1, T2N0, and T2N1) breast cancer. Long-term follow-up was conducted to define toxicities, recurrence patterns and RFS and OS.

RESULTS

Fifty-three women with clinical stage II breast cancer were randomized, 26 patients to receive preoperative chemotherapy and 27 to receive postoperative chemotherapy. Long-term follow-up, with a median of 25.3 years, was obtained. Local or systemic recurrence occurred in 8 women in the preoperative group and in 10 women in the postoperative group, and recurrences were predominantly within 10 years of treatment. Late toxicities included local upper extremity paresthesia's, upper extremity edema and congestive heart failure in 1 patient each. Analysis revealed no difference in RFS (20-year RFS probabilities; preoperative: 61.3%, postoperative: 54.7%, P=0.42), or in OS between the 2 treatment groups (20-year probabilities, preoperative: 64.6%, postoperative: 62.2%, P=0.44). Twenty-five of 53 patients (47%) were alive and without disease at this follow-up.

CONCLUSION

Twenty-five-year follow-up for this prospective randomized trial confirms the equivalency of preoperative versus postoperative chemotherapy with fluorouracil, leucovorin calcium, doxorubicin, and cyclophosphamides/granulocyte colony-stimulating factor for stage II breast cancer for both RFS and OS.

Intrahepatic cholangiocarcinoma as a rare secondary malignancy after allogeneic hematopoietic stem cell transplantation for childhood acute lymphoblastic leukemia: A case report

Secondary malignancies are a significant cause of non-relapse mortality in patients who undergo allogeneic HCT. However, secondary liver cancer is rare, and ICC following HCT has never been reported in the literature. Secondary solid cancers typically have a long latency period, and cholangiocarcinoma is classically a malignancy occurring in older individuals. Here, we report the first case of secondary ICC, which presented just 3 years after HCT in a young adult with a history of childhood ALL. A 26-year-old male with history of precursor B-cell ALL presented with asymptomatic elevated liver function tests 3 years after HCT. Laboratories were indicative of biliary obstruction. ERCP showed focal biliary stricturing of the common and left hepatic ducts. MRCP revealed left intrahepatic duct dilatation, suggestive of intrahepatic obstructing mass. Additional workup lead to a clinical diagnosis of ICC. The patient underwent left hepatectomy with extrahepatic bile duct resection and portal lymphadenectomy. Surgical pathology was consistent with moderately differentiated cholangiocarcinoma. Our case illustrates a rare SMN following HCT for ALL. It is the first case report of ICC occurring as a secondary cancer in this patient population. Although cholangiocarcinoma is characteristically diagnosed in the older population, it must remain on the differential for biliary obstruction in post-HCT patients.

Stage and disease-free interval help select patients for surgical management of locally recurrent and metastatic adrenocortical carcinoma

BACKGROUND AND OBJECTIVES

Chemotherapeutic options for patients with recurrent/metastatic adrenocortical carcinoma (ACC) are limited, leading to consideration for surgical management. We sought to determine characteristics associated with an unequivocal survival benefit amongst patients undergoing re-resection or metastasectomy.

METHODS

Patients who underwent surgery for recurrent/metastatic ACC were identified and stratified into two groups: those with postoperative survival comparable with what has been reported with chemotherapy alone (<12 months) and those surviving twice that duration (>24 months). Those who survived between 12 and 24 months were excluded, as the objective was to characterize patients who most distinctly benefited from resection. Clinicopathologic and treatment variables were evaluated for associations with survival.

RESULTS

Forty-three patients survived more than 24 months and 15 patients died less than 12 months after reoperation. Tumor stage (odds ratio [OR], 0.66; 95% confidence interval [CI], 0.45-0.96) and disease-free interval (DFI; OR, 3.23; 95% CI, 1.68-6.22) were associated with prolonged survival. Tumor size, hormonal status, resection margin, and treatment with chemotherapy, radiation, and mitotane were not associated with prolonged survival. Patients who survived more than 24 months underwent more procedures for subsequent recurrences (median 4 vs 2; P < .001).

CONCLUSION

Stage and DFI can help select optimal candidates for resection of recurrent/metastatic ACC. Patients selected for surgical management should be informed of the likelihood of requiring multiple interventions.

Antigen Experienced T Cells from Peripheral Blood Recognize p53 Neoantigens

PURPOSE

The purpose of this study was to evaluate antigen experienced T cells in peripheral blood lymphocytes (PBL) for responses to p53 neoantigens.

EXPERIMENTAL DESIGN

PBLs from patients with a mutated TP53 tumor were sorted for antigen-experienced T cells and in vitro stimulation (IVS) was performed with p53 neoantigens. The IVS cultures were stimulated with antigen-presenting cells expressing p53 neoantigens, enriched for 41BB/OX40 and grown with rapid expansion protocol.

RESULTS

T-cell responses were not observed in the PBLs of 4 patients who did not have tumor-infiltrating lymphocyte (TIL) responses to mutated TP53. In contrast, 5 patients with TIL responses to mutated TP53 also had similar T-cell responses in their PBLs, indicating that the PBLs and TILs were congruent in p53 neoantigen reactivity. CD4⁺ and CD8⁺ T cells were specific for p53^R175H, p53^Y220C, or p53^R248W neoantigens, including a 78% reactive T-cell culture against p53^R175H and HLA-A*02:01. Tracking TCRB clonotypes (clonality, top ranked, and TP53 mutation-specific) supported the enrichment of p53 neoantigen-reactive T cells from PBLs. The same T-cell receptor (TCR) from the TIL was found in the IVS cultures in three cases and multiple unique TCRs were found in another patient. TP53 mutation-specific T cells also recognized tumor cell lines bearing the appropriate human leukocyte antigen restriction element and TP53 mutation, indicating these T cells could recognize processed and presented p53 neoantigens.

CONCLUSIONS

PBL was a noninvasive source of T cells targeting TP53 mutations for cell therapy and can provide a window into intratumoral p53 neoantigen immune responses.See related commentary by Olivera et al., p. 1203.

Resection and chemotherapy is the optimal treatment approach for patients with clinically node positive intrahepatic cholangiocarcinoma

BACKGROUND

Clinically lymph node positive (cLNP) intrahepatic cholangiocarcinoma (ICC) carries a poor prognosis, without clear management guidelines for the practicing clinician. We sought to evaluate current practice patterns for cLNP ICC, including associations with survival.

METHODS

The National Cancer Database was queried for patients with cLNP ICC, without extrahepatic metastases.

RESULTS

We identified 1023 patients with cLNP ICC, 77%% (n = 784) of whom received chemotherapy alone. Resection was undertaken in 23% (n = 239) of patients and was most commonly utilized in combination with chemotherapy (n = 150). Median survival for all patients was 13.6 months. Patients undergoing resection in combination with chemotherapy were associated with an improved survival (22.5 months) as compared to those patients receiving chemotherapy alone (11.9 months) or resection alone (12.4 months) (p < 0.01). Finally, we compared the survival of patients with cLNP ICC with that of patients with pathologically proved lymph node positive (pLNP) ICC, all of whom were treated with resection with chemotherapy, and found no difference in survival (22.5 months-19.3 months, p = 0.99, respectively).

CONCLUSIONS

While the decision to pursue resection for ICC is multifactorial and patient specific, the presence of clinically positive LNs should not represent a contraindication.

Using Human Induced Pluripotent Stem Cells for the Generation of Tumor Antigen-specific T Cells

The generation and expansion of functional T cells in vitro can lead to a broad range of clinical applications. One such use is for the treatment of patients with advanced cancer. Adoptive T cell transfer (ACT) of highly enriched tumor antigen-specific T cells has been shown to cause durable regression of metastatic cancer in some patients. However, during expansion, these cells may become exhausted or senescent, limiting their effector function and persistence in vivo. Induced pluripotent stem cell (iPSC) technology may overcome these obstacles by leading to in vitro generation of large numbers of less differentiated tumor antigen-specific T cells. Human iPSC (hiPSC) have the capacity to differentiate into any type of somatic cell, including lymphocytes, which retain the original T cell receptor (TCR) genomic rearrangement when a T cell is used as a starting cell. Therefore, reprogramming of human tumor antigen-specific T cells to hiPSC followed by redifferentiation to T cell lineage has the potential to produce rejuvenated tumor antigen-specific T cells. Described here is a method for generating tumor antigen-specific CD8αβ⁺ single positive (SP) T cells from hiPSC using OP9/DLL1 co-culture system. This method is a powerful tool for in vitro T cell lineage generation and will facilitate the development of in vitro derived T cells for use in regenerative medicine and cell-based therapies.

Surgical Resection of Pheochromocytomas and Paragangliomas is Associated with Lower Cholesterol Levels

BACKGROUND

Catecholamine excess in patients with pheochromocytomas or paragangliomas (PPGLs) can lead to hypertension, diabetes and hyperlipidemia. The aim was to investigate the prevalence of hyperlipidemia and the effect of surgical resection.

METHODS

One hundred and thirty-two patients with PPGLs underwent an operation at the National Institutes of Health from 2009 to 2016, of which 54 patients met the inclusion criteria. Clinical demographics, BMI, genetic mutations, tumor size, perioperative catecholamine levels and perioperative lipid panels were retrospectively reviewed. Spearman correlation between catecholamines and lipid levels was evaluated. Paired Wilcoxon and paired t test were used to analyze differences in pre- and postoperative lipid levels.

RESULTS

Preoperatively, 51 patients (94.4%) had elevated catecholamines, thirteen (24.1%) had elevated total cholesterol (TC) (>200 mg/dL), nine (16.6%) had elevated LDL (>130 mg/dL) and ten (18.5%) had elevated triglycerides (>150 mg/dL). Serum and urinary metanephrine levels were positively associated with TC (r = 0.2792, p = 0.0372 and r = 0.4146, p = 0.0031, respectively) and LDL levels (r = 0.2977, p = 0.0259 and r = 0.4434, p = 0.0014, respectively). Mean TC decreased from 176.4 to 166.3 mg/dL (p = 0.0064) and mean HDL decreased from 56.7 to 53.2 mg/dL (p = 0.0253) after PPGL resection (median 3.1 months (range 1.3-50.2) between lipid panels). Most patients with elevated TC (76.9%) had improvement with mean TC decreasing from 225 to 200.2 mg/dL (p = 0.0230). Of patients with elevated LDL, 66.7% had improvement with mean LDL decreasing from 149 to 131.1 mg/dL (p = 0.0313).

CONCLUSIONS

The prevalence of hyperlipidemia in patients with PPGLs is 46%. Future prospective studies are needed to determine whether surgical resection improves TC and/or LDL levels.

Generation of Tumor Antigen-Specific iPSC-Derived Thymic Emigrants Using a 3D Thymic Culture System

Induced pluripotent stem cell (iPSC)-derived T cells may provide future therapies for cancer patients, but those generated by current methods, such as the OP9/DLL1 system, have shown abnormalities that pose major barriers for clinical translation. Our data indicate that these iPSC-derived CD8 single-positive T cells are more like CD4⁺CD8⁺ double-positive T cells than mature naive T cells because they display phenotypic markers of developmental arrest and an innate-like phenotype after stimulation. We developed a 3D thymic culture system to avoid these aberrant developmental fates, generating a homogeneous subset of CD8αβ⁺ antigen-specific T cells, designated iPSC-derived thymic emigrants (iTEs). iTEs exhibit phenotypic and functional similarities to naive T cells both in vitro and in vivo, including the capacity for expansion, memory formation, and tumor suppression. These data illustrate the limitations of current methods and provide a tool to develop the next generation of iPSC-based antigen-specific immunotherapies.

A Three-dimensional Thymic Culture System to Generate Murine Induced Pluripotent Stem Cell-derived Tumor Antigen-specific Thymic Emigrants

The inheritance of pre-rearranged T cell receptors (TCRs) and their epigenetic rejuvenation make induced pluripotent stem cell (iPSC)-derived T cells a promising source for adoptive T cell therapy (ACT). However, classical in vitro methods for producing regenerated T cells from iPSC result in either innate-like or terminally differentiated T cells, which are phenotypically and functionally distinct from naïve T cells. Recently, a novel three-dimensional (3D) thymic culture system was developed to generate a homogenous subset of CD8αβ⁺ antigen-specific T cells with a naïve T cell-like functional phenotype, including the capacity for proliferation, memory formation, and tumor suppression in vivo. This protocol avoids aberrant developmental fates, allowing for the generation of clinically relevant iPSC-derived T cells, designated as iPSC-derived thymic emigrants (iTE), while also providing a potent tool to elucidate the subsequent functions necessary for T cell maturation after thymic selection.

MicroRNA-210 May Be a Preoperative Biomarker of Malignant Pheochromocytomas and Paragangliomas

BACKGROUND

Currently, no reliable predictive clinical or laboratory tests exist that can accurately distinguish between benign and malignant pheochromocytomas or paragangliomas (PPGLs). The aim of this study was to investigate if serum microRNA-210 (miR-210) levels could be a marker of malignancy in patients with PPGLs.

METHODS

Preoperative serum from patients with PPGLs was collected on the day of surgery. Clinical demographics, germline mutation status, primary tumor size, postoperative biochemical response, and the development of malignant disease were prospectively collected. Total microRNA was extracted from preoperative serum samples, and miR-210 levels were measured by quantitative real-time reverse transcription-polymerase chain reaction and normalized to miR-16. Prognostic variables were compared using univariable and multivariable analyses.

RESULTS

Of the 35 patients, 10 (29%) were diagnosed with malignant PPGLs and 25 patients (71%) were diagnosed with benign PPGLs (median follow-up 72.5 mo). Sixty-nine percent of patients had a pheochromocytoma (n = 24/35) compared with 31% of patients with paraganglioma (n = 11/35). The most common germline mutation was succinate dehydrogenase complex subunit B (SDHB) (n = 10). On univariable analysis, lower serum miR-210 expression level (2.3 ± 0.5 versus 3.1 ± 1.2, P = 0.013) and larger primary tumor size (6.7 ± 5.0 cm versus 4.1 ± 2.3 cm, P = 0.043) were significantly associated with malignant disease. No significant prognostic variables were found on multivariable analysis.

CONCLUSIONS

In this pilot study, low serum miR-210 expression levels and large primary tumors were identified to be markers of PPGL malignancy on univariable analysis. Given the initial encouraging results in a small cohort, further investigation is warranted to determine if serum miR-210 levels are prognostic.

Tumor Size and Presence of Metastatic Disease at Diagnosis are Associated with Disease-Specific Survival in Parathyroid Carcinoma

BACKGROUND

The incidence of parathyroid carcinoma is reported to be rising. There is minimal data on prognostic variables associated with cancer-specific survival. The objectives of this study were to evaluate the trends in incidence and assess prognostic factors.

METHODS

A retrospective review of the SEER database between 1973 and 2014 was performed, identifying 520 patients with parathyroid carcinoma. Population-adjusted incidence rates were calculated in 4-year intervals. A Cochrane-Armitage test was performed to analyze changes in trend in incidence, tumor size, and extent of disease. Age, year of diagnosis, race, gender, extent of disease, surgical resection, treatment with radiation, tumor size, and lymph node status were assessed using Mantel-Cox log rank test. Multivariate analysis was performed by Cox regression analysis.

RESULTS

The incidence of parathyroid carcinoma has been increasing since 1974 from 2 to 11 cases per 10 million people but has since stabilized at 11 cases per 10 million people since 2001. The increasing incidence was attributed to locoregional disease and tumor size < 3 cm. The presence of metastatic disease [hazard ratio (HR) 111.4, 95% confidence interval (CI) 20.6-601.8, p < 0.0001) and tumor size > 3 cm (HR 5.6, 95% CI 1.5-21.2, p = 0.011] were associated with worse cancer-specific survival by univariate and multivariate analyses.

CONCLUSIONS

The incidence of parathyroid carcinoma has remained stable over the past decade. Tumor size < 3 cm and regional disease have increased in incidence. Patients with metastatic disease and tumors > 3 cm have worse cancer-specific survival. These findings can be incorporated in the development of a staging system for parathyroid carcinoma.

Patient simulation for training basic and advanced clinical skills

INTRODUCTION

Patient simulators are increasingly used in the education and training of healthcare professionals. This paper describes the history of human patient simulator development, the features of contemporary simulators, the acquisition of basic and advanced clinical skills using patient simulators, and the benefits, cost, limitations and effectiveness of this innovative learning modality.

SIMULATOR DEVELOPMENT

The development of human patient simulators began in the late 1960s, and accelerated in the late 1980s and early 1990s. Several simulator systems are now professionally manufactured, commercially available, and used at hundreds of medical centres, universities and colleges in the USA and throughout the world. Contemporary patient simulators have many clinical features, and look and respond to interventions with ever-increasing degrees of realism because sophisticated physiological and pharmacological models automatically control many features.

SIMULATOR USE IN MEDICAL EDUCATION

Simulators are used to teach basic skills, such as respiratory physiology and cardiovascular haemodynamics, and advanced clinical skills, e.g. management of difficult airways, tension pneumothorax, pulmonary embolism and shock.

BENEFITS, COSTS AND LIMITATIONS

The simulation laboratory offers distinct educational advantages, especially for learning how to recognise and to treat rare, complex, clinical problems. Costs of simulator-based educational programmes include facility, equipment and personnel. Current limitations include clinical realism of the patient manikin and faculty development.

Minocycline: stain devil?

Minocycline is the treatment of choice for acne vulgaris, the most common form of inflammatory acne, despite the increase in awareness of rare but significant side-effects. This paper discusses the undesirable side-effect of minocycline staining in permanent teeth.

Educational simulation of the electroencephalogram (EEG)

We describe a model for simulating a spontaneous electroencephalogram (EEG) and for simulating the effects of anesthesia on the EEG, to allow anesthesiologists and EEG technicians to learn and practice intraoperative EEG monitoring. For this purpose, we developed a linear model to manipulate the amplitude of the activity in each of the traditional EEG frequency bands. Burst suppression patterns are simulated by manipulating an overall gain. To demonstrate the model feasibility, model parameters for thiopental and isoflurane were estimated guided by published data on the EEG effects of these anesthetic drugs. Using these estimates, EEG time signals were simulated for isoflurane at various partial pressures, and for bolus intravenous doses of thiopental. Comparison with actual recorded EEG signals showed that the changes produced by isoflurane and thiopental in the simulated signals are very similar to the changes in the actual signals, which was confirmed by two clinicians with experience and routine practice in intraoperative EEG monitoring.

Influence of pulse oximetry and capnography on time to diagnosis of critical incidents in anesthesia: a pilot study using a full-scale patient simulator

OBJECTIVE

Many studies (outcome, epidemiological) have tested the hypothesis that pulse oximetry and capnography affect the outcome of anesthetic care. Uncontrollable variables in clinical studies make it difficult to generate statistically conclusive data. In the present study, we eliminated the variability among patients and operative procedures by using a full-scale patient simulator. We tested the hypothesis that pulse oximetry and capnography shorten the time to diagnosis of critical incidents.

METHODS

A simulator was programmed to represent a patient undergoing medullary nailing of a fractured femur under general anesthesia and suffering either malignant hyperthermia, a pneumothorax, a pulmonary embolism or an anoxic oxygen supply. One hundred thirteen anesthesiologists were randomly assigned to one of two groups of equal size, one with access to pulse oximetry and capnography data and the other without. Each anesthesiologist was further randomized to one of the four critical incidents. Each anesthetic procedure was videotaped. The time to correct diagnosis was measured and analyzed.

RESULTS

Based on analysis of 91 of the subjects, time to diagnosis was significantly shorter (median of 432 s vs. >480 s) for the anoxic oxygen supply scenario (p = 0.019) with pulse oximetry and capnography than without. No statistical difference in time to diagnosis was obtained between groups for the other three critical incidents.

CONCLUSIONS

Simulation may offer new approaches to the study of monitoring technology. However, the limitations of current simulators and the resources required to perform simulator-based research are impediments to wide-spread use of this tool.

Pharmacokinetic-pharmacodynamic model for educational simulations

Pharmacokinetic-pharmacodynamic (PK-PD) models play an important role in educational simulations. The parameters of PK-PD models described in the scientific literature are obtained from studies in which the drug concentrations and the drug-effect data are measured simultaneously. Simultaneous PK-PD studies cannot be expected to incorporate all possible combinations of drugs and patient physiology that are desired for educational simulations. To solve this problem, we elaborate on the traditional simultaneous PK-PD model, creating a new model that accepts parameter data from different, more readily available, nonsimultaneous pharmacologic studies. These data are incorporated in the model using a novel estimation procedure for the parameters kc0 and EC50. A sensitivity analysis of the parameter estimation procedure confirms that the time of peak effect following a bolus and the dose-response curve are accurately reflected by the new model. It also demonstrates how inconsistencies among the different parameter sets affect simulation of the recovery phase. The model is extended to incorporate any monotonic parametric or nonparametric dose-response curve. For the neuromuscular relaxant vecuronium, we demonstrate that data from different pharmacologic studies are available, and that the described estimation procedure leads to parameter estimates that are within the standard deviations of the parameters determined in a simultaneous PK-PD study.

TWITCHER: a device to stimulate thumb twitch response to ulnar nerve stimulation

OBJECTIVE

To design and fabricate a device to simulate evoked thumb adduction in response to ulnar nerve stimulation.

METHODS

We implemented a computer-controlled, motorized thumb (TWITCHER) that responds to ulnar nerve stimulation by an unmodified peripheral nerve stimulator. Clinically realistic response patterns are generated for both depolarizing and non-depolarizing muscle relaxants and three modes of stimulation (single twitch, train-of-four, tetanus).

RESULTS

The device has been used in a full-scale patient simulator for the last six years.

DISCUSSION

TWITCHER has been well received by participants in simulation exercises including the use of neuromuscular blocking drugs.

Logistics of conducting a large number of individual sessions with a full-scale patient simulator at a scientific meeting

OBJECTIVE

To design and implement the logistics of accommodating a large number of participants in individual, hands-on sessions on a full-scale patient simulator during a major scientific meeting or continuing medical education course.

METHODS

We used our method during the 11th World Congress of Anaesthesiologists in Sydney, Australia to facilitate studying the impact of pulse oximetry and capnography on the time taken by anesthesiologists to correctly identify critical incidents on a full-scale patient simulator. Each study participant spent 15 minutes in 4 sections of the study area: the anesthesia and monitoring equipment briefing room, the simulator briefing room, the simulation room and the debriefing room.

RESULTS

There were 113 participants during five days (15 during instructor training and 25, 23, 24 and 26 on subsequent exhibit days). We were oversubscribed daily. However, there were 9 no-shows during the 4 days of the study, which generated a participant absence rate of 9.2%. The average number of participants over the 4 days of the study was 24.5 per day compared to our capacity of 27 per day. The feedback we obtained from the participants about the simulation experience and the format of the exercise was positive and enthusiastic.

CONCLUSIONS

We have developed a practical and viable method that can be adapted for use at scientific meetings and courses, which improves accessibility of individual, hands-on sessions on full-scale patient simulators to a larger audience than previously attainable. Our method is applicable for continuing medical education courses as well as research purposes in the form of prospective studies during scientific meetings and courses.

Modeling obstetric cardiovascular physiology on a full-scale patient simulator

To our knowledge, this is the first attempt at adapting an existing cardiovascular model to simulate the hemodynamics of a particular patient population. Despite attempts to define the physiologic alterations in advance, we discovered there were critical parameters not completely defined in the literature. These were discovered through the iterative process of testing, comparing resulting vital signs with targets, and literature review. A list of the parameters that should be sought for future modeling efforts is provided (Table 3), but this list is by no means exhaustive. As further work is performed in this area, additional independent and essential parameters will be identified (pressure characteristics of valvular anomalies, for example). To define a physiology that is less well described in the literature, empirical alterations and best-guess estimates of parameter changes will be required with significantly more iterations. Finally, we have described only modeling of cardiovascular physiology, modeling the respiratory system will require a similar process.

Comparison of tests for detecting leaks in the low-pressure system of anesthesia gas machines

Small leaks in the low-pressure system (LPS) of the anesthesia gas machine can cause hypoxia or patient awareness. We sought to determine the relative sensitivities of the various tests recommended for detecting LPS leaks before anesthesia. Special adapters were fashioned to create leaks of six different sizes in the LPS that were equivalent to the following: a single 25-, 22-, 20-, or 15-gauge needle, two 15-gauge needles, or a 2.5-mm endotracheal tube connector. With each leak condition, five different leak tests were performed on three each of the following machines: Ohmeda Modulus I, Ohmeda Modulus II-Plus, and North American Dräger Narkomed (2A, 3 and 4), for a total of 54 leaks to be detected for each leak test (3 x 3 x 6). The number of leaks detected with each test was compared by Fisher's exact test, P < 0.05 being considered significant. Only the negative pressure leak test detected all 54 leaks, a significant difference from the positive pressure test, which detected the least number of leaks, 28 (P < 0.05). Some leak tests are more suitable for specific anesthesia machines. Adoption of the negative pressure test as a universal LPS leak test may prevent the risks associated with using the wrong test for the particular anesthesia machine: hypoxic gas or patient awareness.

Duration of carbon dioxide absorption by soda lime at low rates of fresh gas flow

STUDY OBJECTIVE

To determine the impact of a low fresh gas flow rate on the duration of carbon dioxide (CO2) absorption by soda lime.

DESIGN

Nonclinical, experimental.

SETTING

Experimental laboratory.

METHODS

In vitro test with Sodasorb and a semiclosed breathing circle ventilating a test lung with a CO2 inflow of 250 ml per minute. Fresh gas flow rates of 0.25, 0.5, 1, 2, and 4 L/min were studied.

MEASUREMENTS AND MAIN RESULTS

CO2 was measured at the breathing circuit test lung interface with a mainstream capnometer. Duration of CO2 absorption was determined as the time for the inspired CO2 tension (PICO2) to increase from 0 mm to 7 mm of mercury. The times of this interval were recorded four times for each fresh gas flow rate and compared by analysis of variance; p less than 0.05 was considered significant. Time to soda lime failure was significantly longer at 2 L/min than at 1 L/min fresh gas flow and at 1 L/min than at 0.25 L/min fresh gas flow.

CONCLUSION

Because soda lime color indicators are unreliable, when a semiclosed breathing circle is used at a low rate of fresh gas flow without CO2 monitoring, the CO2 absorbent must be replaced more frequently.