High Amounts of SARS-CoV-2 Precede Sickness Among Asymptomatic Health Care Workers.

BACKGROUND: Whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) positivity among asymptomatic subjects reflects past or future disease may be difficult to ascertain. METHODS: We tested 9449 employees at Karolinska University Hospital, Stockholm, Sweden for SARS-CoV-2 RNA and antibodies, linked the results to sick leave records, and determined associations with past or future sick leave using multinomial logistic regression. RESULTS: Subjects with high amounts of SARS-CoV-2 virus, indicated by polymerase chain reaction (PCR) cycle threshold (Ct) value, had the highest risk for sick leave in the 2 weeks after testing (odds ratio [OR], 11.97; 95% confidence interval [CI], 6.29-22.80) whereas subjects with low amounts of virus had the highest risk for sick leave in the 3 weeks before testing (OR, 6.31; 95% CI, 4.38-9.08). Only 2.5% of employees were SARS-CoV-2 positive while 10.5% were positive by serology and 1.2% were positive in both tests. Serology-positive subjects were not at excess risk for future sick leave (OR, 1.06; 95% CI, .71-1.57). CONCLUSIONS: High amounts of SARS-CoV-2 virus, as determined using PCR Ct values, was associated with development of sickness in the next few weeks. Results support the concept that PCR Ct may be informative when testing for SARS-CoV-2. Clinical Trials Registration. NCT04411576.

Risk of SARS-CoV-2 exposure among hospital healthcare workers in relation to patient contact and type of care.

AIM: We aimed to assess prevalence of IgG antibodies to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and factors associated with seropositivity in a large cohort of healthcare workers (HCWs). METHODS: From 11 May until 11 June 2020, 3981 HCWs at a large Swedish emergency care hospital provided serum samples and questionnaire data. Presence of IgG antibodies to SARS-CoV-2 was measured as an indicator of SARS-CoV-2 exposure. RESULTS: The total seroprevalence was 18% and increased during the study period. Among the seropositive HCWs, 11% had been entirely asymptomatic. Participants who worked with COVID-19 patients had higher odds for seropositivity: adjusted odds ratio 1.96 (95% confidence intervals 1.59-2.42). HCWs from three of the departments managing COVID-19 patients had significantly higher seroprevalences, whereas the prevalence among HCWs from the intensive care unit (also managing COVID-19 patients) was significantly lower. CONCLUSIONS: HCWs in contact with SARS-CoV-2 infected patients had a variable, but on average higher, likelihood for SARS-CoV-2 infections.

Socioeconomic position is associated with surgical treatment of open fractures of the lower limb: results from a Swedish population-based study.

Background and purpose - High-energy trauma to the lower limbs can result in open fractures, treated by reconstructive surgery or amputation. We examined whether socioeconomic position is associated with choice of primary treatment.Patients and methods - We performed a nationwide population-based study using the Swedish National Patient Register to identify all adult patients who between 1998 and 2013 underwent reconstruction or amputation after an open fracture below the knee. Information on socioeconomic position was collected from Statistics Sweden.Results - Of 275 individuals undergoing surgery after an open fracture below the knee during the study period, the 1st surgery was reconstructive in 58% of the patients and amputation in 42%. The chance of having an initial reconstruction was lower for women than for men (OR 0.5, 95% CI 0.3-0.9), lower with age (OR 0.97, CI 0.96-0.99), and lower for individuals without employment compared with individuals in employment (OR 0.3, CI 0.2-0.5). Primary treatment was in women associated with family composition, whereas in men it was associated with level of education.Interpretation - Choice of primary treatment after open fracture in the lower limb is affected by socioeconomic position including sex, age, employment, family composition, level of education, and income.

Management of the Midface in the Transgender Patient.

Management of the midface has a central role to achieve harmony in the transgender patient requesting facial feminization surgery. The relative projection of separate areas of the craniofacial skeleton largely determines the appearance of the facial framework. In this article the authors describe the management of the midface; bony remodeling and soft tissue aspects, in the transgender patient.

Infection with high proportion of multidrug-resistant bacteria in conflict-related injuries is associated with poor outcomes and excess resource consumption: a cohort study of Syrian patients treated in Jordan.

BACKGROUND: Armed conflicts are a major contributor to injury and death globally. Conflict-related injuries are associated with a high risk of wound infection, but it is unknown to what extent infection directly relates to sustainment of life and restoration of function. The aim of this study was to investigate the outcome and resource consumption among civilians receiving acute surgical treatment due to conflict-related injuries. Patients with and without wound infections were compared. METHODS: We performed a cohort study using routinely collected data from 457 consecutive Syrian civilians that received surgical treatment for acute conflict-related injuries during 2014-2016 at a Jordanian hospital supported by Médecins Sans Frontières. We defined wound infection as clinical signs of infection verified by a positive culture. We used logistic regression models to evaluate infection-related differences in outcome and resource consumption. RESULTS: Wound infection was verified in 49/457 (11%) patients. Multidrug-resistance (MDR) was detected in 36/49 (73%) of patients with infection. Among patients with infection, 11/49 (22%) were amputated, compared to 37/408 (9%) without infection, crude relative risk = 2.62 (95% confidence interval 1.42-4.81). Infected patients needed 12 surgeries on average, compared to five in non-infected patients (p < .00001). Mean length of stay was 77 days for patients with infection, and 35 days for patients without infection (p = .000001). CONCLUSIONS: Among Syrian civilians, infected conflict-related wounds had a high prevalence of MDR bacteria. Wound infection was associated with poor outcomes and high resource consumption. These results could guide the development of antibiotic protocols and adaptations of surgical management to improve care for wound infections in conflict-related injuries. TRIAL REGISTRATION: ClinicalTrials.gov ( NCT02744144 ). Registered April 13, 2016. Retrospectively registered.

Predicting past and future SARS-CoV-2-related sick leave using discrete time Markov modelling.

BACKGROUND: Prediction of SARS-CoV-2-induced sick leave among healthcare workers (HCWs) is essential for being able to plan the healthcare response to the epidemic. METHODS: During first wave of the SARS-Cov-2 epidemic (April 23rd to June 24th, 2020), the HCWs in the greater Stockholm region in Sweden were invited to a study of past or present SARS-CoV-2 infection. We develop a discrete time Markov model using a cohort of 9449 healthcare workers (HCWs) who had complete data on SARS-CoV-2 RNA and antibodies as well as sick leave data for the calendar year 2020. The one-week and standardized longer term transition probabilities of sick leave and the ratios of the standardized probabilities for the baseline covariate distribution were compared with the referent period (an independent period when there were no SARS-CoV-2 infections) in relation to PCR results, serology results and gender. RESULTS: The one-week probabilities of transitioning from healthy to partial sick leave or full sick leave during the outbreak as compared to after the outbreak were highest for healthy HCWs testing positive for large amounts of virus (ratio: 3.69, (95% confidence interval, CI: 2.44-5.59) and 6.67 (95% CI: 1.58-28.13), respectively). The proportion of all sick leaves attributed to COVID-19 during outbreak was at most 55% (95% CI: 50%-59%). CONCLUSIONS: A robust Markov model enabled use of simple SARS-CoV-2 testing data for quantifying past and future COVID-related sick leave among HCWs, which can serve as a basis for planning of healthcare during outbreaks.

Implant Attributes or Patient Characteristics? Factors Affecting Outcome after Breast Augmentation in Transgender Women.

Implant-based breast augmentation is a valuable tool for treatment of gender dysphoria in transgender women. The aim was to assess whether implant attributes, plane selection, and patient characteristics had an impact on the surgical outcome, and to compare these parameters between transgender and cisgender breast augmentations. Methods: A cohort of transgender women who underwent breast augmentation at our department during 2009-2018 were retrospectively studied. The cohort was also compared with a cohort of 12,884 mainly cisgender women registered in the Swedish breast implant registry (BRIMP) during 2014-2019. Results: A total of 143 transgender individuals were included, with a median follow-up of 5.7 years. Complications occurred in 20 patients (14.0%), four patients (2.8%) underwent acute reoperation, and 20 patients (14.0%) had secondary corrections. No differences were seen in complication rates when comparing prepectoral with subpectoral placement (15.1% versus 12.9%; P = 0.81); size, less than 400 mL versus greater than or equal to 400 mL (14.7% versus 13.3%; P = 0.81), or the shape of the implants, round versus anatomic (10.7% versus 22.2%; P = 0.10). In comparison with the cohort from BRIMP, the transgender cohort had more round implants (72.0% versus 60.7%; P < 0.01), larger implants (44.1% had volumes of 400-599 mL, compared with 25.4%; P < 0.0001), and more prepectoral placement (51.0% versus 7.3%; P < 0.0001). The risk of reoperation less than 30 days was 1.2% in BRIMP and 2.8% in the transgender cohort (P = 0.08). Conclusions: In transgender women, implants are often larger, round, and placed prepectoral' compared with cisgender women. Despite these differences, complication rates were equivalent. Implant attributes, surgical techniques, and patient characteristics were not independently associated with the rate of complications.

Improved Surgical Outcome with Double Incision and Free Nipple Graft in Gender Confirmation Mastectomy.

BACKGROUND: Mastectomy and chest-wall contouring is the most common gender confirmation surgery. With increasing prevalence of transgender individuals, there is a demand for better surgical outcomes and aesthetic results. Our aim was to evaluate surgical techniques used and assess modifications in gender confirmation mastectomies at Karolinska University hospital in Stockholm, Sweden. METHODS: A retrospective cohort study was performed on 464 patients undergoing gender confirmation mastectomies in our department between 2009 and 2018. Patient demographics, psychiatric comorbidity, surgical method, and outcome were analyzed. Follow-up was at least one year. RESULTS: The most frequently used surgical technique for gender confirmation mastectomies was double incision with free nipple graft (243 patients, 52.4%), followed by periareolar incision (113 patients, 24.4%) and semicircular incision (67 patients, 14.4%). The double incision technique and periareolar technique were associated with 18.9% and 28.3% complications, 3.3% and 12.4% acute reoperations, 28.4% and 65.5% secondary revisions, respectively. The double incision technique increased from being used in 17.8% of all mastectomies during 2009-2013 to 62.9% during 2014-2018, while periareolar incision decreased from 43.0% to 18.5%. CONCLUSIONS: The current study describes a successful transition of surgical technique from periareolar incision to double incision with free nipple graft in gender confirmation mastectomy, leading to significant improvements in the overall outcome with fewer complications, less acute reoperations and less secondary corrections. Hence, we consider the double incision with free nipple graft technique to be the favored technique in the vast majority of cases in female-to-male chest wall contouring.

Potential SARS-CoV-2 infectiousness among asymptomatic healthcare workers.

A majority of SARS-CoV-2 infections are transmitted from a minority of infected subjects, some of which may be symptomatic or pre-symptomatic. We aimed to quantify potential infectiousness among asymptomatic healthcare workers (HCWs) in relation to prior or later symptomatic disease. We previously (at the onset of the SARS-CoV-2 epidemic) performed a cohort study of SARS-CoV-2 infections among 27,000 healthcare workers (HCWs) at work in the capital region of Sweden. We performed both SARS-CoV-2 RT-PCR and serology. Furthermore, the cohort was comprehensively followed for sick leave, both before and after sampling. In the present report, we used the cohort database to quantify potential infectiousness among HCWs at work. Those who had sick leave either before or after sampling were classified as post-symptomatic or pre-symptomatic, whereas the virus-positive subjects with no sick leave were considered asymptomatic. About 0.2% (19/9449) of HCW at work were potentially infectious and pre-symptomatic (later had disease) and 0.17% (16/9449) were potentially infectious and asymptomatic (never had sick leave either before nor after sampling). Thus, 33% and 28% of all the 57 potentially infectious subjects were pre-symptomatic or asymptomatic, respectively. When a questionnaire was administered to HCWs with past infection, only 10,5% of HCWs had had no indication at all of having had SARS-CoV-2 infection ("truly asymptomatic"). Our findings provide a unique quantification of the different groups of asymptomatic, potentially infectious HCWs.

Risk for SARS-CoV-2 infection in healthcare workers outside hospitals: A real-life immuno-virological study during the first wave of the COVID-19 epidemic.

OBJECTIVES: Most COVID-19 related infections and deaths may occur in healthcare outside hospitals. Here we explored SARS-CoV-2 infections among healthcare workers (HCWs) in this setting. DESIGN: All healthcare providers in Stockholm, Sweden were asked to recruit HCWs at work for a study of past or present SARS-CoV-2 infections among HCWs. Study participants This study reports the results from 839 HCWs, mostly employees of primary care centers, sampled in June 2020. RESULTS: SARS-CoV-2 seropositivity was found among 12% (100/839) of HCWs, ranging from 0% to 29% between care units. Seropositivity decreased by age and was highest among HCWs <40 years of age. Within this age group there was 19% (23/120) seropositivity among women and 11% (15/138) among men (p<0.02). Current infection, as measured using PCR, was found in only 1% and the typical testing pattern of pre-symptomatic potential "superspreaders" found in only 2/839 subjects. CONCLUSIONS: Previous SARS-CoV-2 infections were common among younger HCWs in this setting. Pre-symptomatic infection was uncommon, in line with the strong variability in SARS-CoV-2 exposure between units. Prioritizing infection prevention and control including sufficient and adequate personal protective equipment, and vaccination for all HCWs are important to prevent nosocomial infections and infections as occupational injuries during an ongoing pandemic.

Differences in risk for SARS-CoV-2 infection among healthcare workers.

Healthcare workers (HCWs) are a risk group for SARS-CoV-2 infection, but which healthcare work that conveys risk and to what extent such risk can be prevented is not clear. Starting on April 24th, 2020, all employees at work (n = 15,300) at the Karolinska University Hospital, Stockholm, Sweden were invited and 92% consented to participate in a SARS-CoV-2 cohort study. Complete SARS-CoV-2 serology was available for n = 12,928 employees and seroprevalences were analyzed by age, sex, profession, patient contact, and hospital department. Relative risks were estimated to examine the association between type of hospital department as a proxy for different working environment exposure and risk for seropositivity, adjusting for age, sex, sampling week, and profession. Wards that were primarily responsible for COVID-19 patients were at increased risk (adjusted OR 1.95 (95% CI 1.65-2.32) with the notable exception of the infectious diseases and intensive care units (adjusted OR 0.86 (95% CI 0.66-1.13)), that were not at increased risk despite being highly exposed. Several units with similar types of work varied greatly in seroprevalences. Among the professions examined, nurse assistants had the highest risk (adjusted OR 1.62 (95% CI 1.38-1.90)). Although healthcare workers, in particular nurse assistants, who attend to COVID-19 patients are a risk group for SARS-CoV-2 infection, several units caring for COVID-19 patients had no excess risk. Large variations in seroprevalences among similar units suggest that healthcare work-related risk of SARS-CoV-2 infection may be preventable.

Antibodies to SARS-CoV-2 and risk of past or future sick leave.

The extent that antibodies to SARS-CoV-2 may protect against future virus-associated disease is unknown. We invited all employees (n = 15,300) at work at the Karolinska University Hospital, Stockholm, Sweden to participate in a study examining SARS-Cov-2 antibodies in relation to registered sick leave. For consenting 12,928 healthy hospital employees antibodies to SARS-CoV-2 could be determined and compared to participant sick leave records. Subjects with viral serum antibodies were not at excess risk for future sick leave (adjusted odds ratio (OR) controlling for age and sex: 0.85 [95% confidence interval (CI) (0.85 (0.43-1.68)]. By contrast, subjects with antibodies had an excess risk for sick leave in the weeks prior to testing [adjusted OR in multivariate analysis: 3.34 (2.98-3.74)]. Thus, presence of viral antibodies marks past disease and protection against excess risk of future disease. Knowledge of whether exposed subjects have had disease in the past or are at risk for future disease is essential for planning of control measures.Trial registration: First registered on 02/06/20, ClinicalTrials.gov NCT04411576.

Negative pressure wound therapy versus standard treatment in patients with acute conflict-related extremity wounds: a pragmatic, multisite, randomised controlled trial.

BACKGROUND: In armed conflict, injuries among civilians are usually complex and commonly affect the extremities. Negative pressure wound therapy (NPWT) is an alternative to standard treatment of acute conflict-related extremity wounds. We aimed to compare the safety and effectiveness of NPWT with that of standard treatment. METHODS: In this pragmatic, randomised, controlled superiority trial done at two civilian hospitals in Jordan and Iraq, we recruited patients aged 18 years or older, presenting with a conflict-related extremity wound within 72 h after injury. Participants were assigned (1:1) to receive either NPWT or standard treatment. We used a predefined, computer-generated randomisation list with three block sizes. Participants and their treating physicians were not masked to treatment allocation. The primary endpoint was wound closure by day 5. The coprimary endpoint was net clinical benefit, defined as a composite of wound closure by day 5 and freedom from any bleeding, wound infection, sepsis, or amputation of the index limb. Analysis was by intention to treat. The trial is registered with ClinicalTrials.gov, number NCT02444598, and is closed to accrual. FINDINGS: Between June 9, 2015, and Oct 24, 2018, 174 patients were randomly assigned to either the NPWT group (n=88) or the standard treatment group (n=86). Five patients in the NPWT group and four in the standard treatment group were excluded from the intention-to-treat analysis. By day 5, 41 (49%) of 83 participants in the NPWT group and 49 (60%) of 82 participants in the standard treatment group had closed wounds, with an absolute difference of 10 percentage points (95% CI -5 to 25, p=0·212; risk ratio [RR] 0·83, 95% CI 0·62 to 1·09). Net clinical benefit was seen in 33 (41%) of 81 participants in the NPWT group and 34 (44%) of 78 participants in the standard treatment group, with an absolute difference of 3 percentage points (95% CI -12 to 18, p=0·750; RR 0·93, 95% CI 0·65 to 1·35). There was one in-hospital death in the standard treatment group and none in the NPWT group. The proportion of participants with sepsis, bleeding leading to blood transfusion, and limb amputation did not differ between groups. INTERPRETATION: NPWT did not yield superior clinical outcomes compared with standard treatment for acute conflict-related extremity wounds. The results of this study not only question the use of NPWT, but also question the tendency for new and costly treatments to be introduced into resource-limited conflict settings without supporting evidence for their effectiveness. This study shows that high-quality, randomised trials in challenging settings are possible, and our findings support the call for further research that will generate context-specific evidence. FUNDING: The Stockholm County Council, the Swedish National Board of Health and Welfare, and Médecins Sans Frontières.

Midfacial Bony Remodeling.

Craniofacial procedures to the midface in conjunction with work to the upper face and skull, and if needed the lower jaw, are a permanent and effective way to achieve feminization of the face in transgender patients. Although the surgery is more complex than other procedures, it should be considered for select patients. Further improvement of cosmesis may be considered a separate surgical entity and is not limited in scope or time by having undergone midface osteotomies. When carefully planned, bony surgery to the midface is safe and results in long-term predictive results and a favorable appearance as the patient ages."

Patient-Specific Titanium-Reinforced Calcium Phosphate Implant for the Repair and Healing of Complex Cranial Defects.

BACKGROUND: The reconstruction of complex cranial defects is challenging and is associated with a high complication rate. The development of a patient-specific, titanium-reinforced, calcium phosphate-based (CaP-Ti) implant with bone regenerative properties has previously been described in 2 case studies with the hypothesis that the implant may improve clinical outcome. OBJECTIVE: To identify whether the introduction of CaP-Ti implant has the potential to improve clinical outcome. METHODS: A retrospective review of all patients having undergone CaP-Ti cranioplasty was conducted. Comprehensive clinical data were collected from the hospital computer database and patient records. Bone formation and osseointegration were analyzed in a single retrieval specimen. RESULTS: Fifty patients, with 52 cranial defects, met the inclusion criteria. The patient cohort displayed a previous failure rate of 64% (32/50) with autologous bone, alloplastic materials, or both. At a median follow-up time of 25 months, the explantation rate due to either early postoperative infection or persistent wound dehiscence was 1.9% (1/53) or 3.8% (2/53), respectively. Surgical intervention with local wound revision was required in 2 patients without the need of implant removal. One patient had a brain tumor recurrence, and the implant was explanted 31 months after implantation. Histologic examination showed that the entire implant was partly yet evenly transformed into vascularized compact bone. CONCLUSION: In the present study the CaP-Ti implant appears to have improved the clinical outcomes in a cohort of patients with a high rate of previous cranioplasty failures. The bone regenerative effect may in particular have an impact on the long-term success rate of the implant.

Negative-Pressure Wound Therapy Versus Standard Treatment of Adult Patients With Conflict-Related Extremity Wounds: Protocol for a Randomized Controlled Trial.

BACKGROUND: In armed conflict, injuries commonly affect the extremities and contamination with foreign material often increases the risk of infection. The use of negative-pressure wound therapy has been described in the treatment of acute conflict-related wounds, but reports are retrospective and with limited follow-up. OBJECTIVE: The objective of this study is to investigate the effectiveness and safety of negative-pressure wound therapy use in the treatment of patients with conflict-related extremity wounds. METHODS: This is a multisite, superiority, pragmatic randomized controlled trial. We are considering for inclusion patients 18 years of age and older who are presenting with a conflict-related extremity wound within 72 hours after injury. Patients are block randomly assigned to either negative-pressure wound therapy or standard treatment in a 1:1 ratio. The primary end point is wound closure by day 5. Secondary end points include length of stay, wound infection, sepsis, wound complications, death, and health-related quality of life. We will explore economic outcomes, including direct health care costs and cost effectiveness, in a substudy. Data are collected at baseline and at each dressing change, and participants are followed for up to 3 months. We will base the primary statistical analysis on intention-to-treat. RESULTS: The trial is ongoing. Patient enrollment started in June 2015. We expect to publish findings from the trial by the end of 2019. CONCLUSIONS: To the best of our knowledge, there has been no randomized trial of negative-pressure wound therapy in this context. We expect that our findings will increase the knowledge to establish best-treatment strategies. TRIAL REGISTRATION: ClinicalTrials.gov NCT02444598; http://clinicaltrials.gov/ct2/show/NCT02444598 (Archived by WebCite at http://www.webcitation.org/72hjI2XNX). INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/12334.

Bioceramic Implant Induces Bone Healing of Cranial Defects.

Autologous bone or inert alloplastic materials used in cranial reconstructions are techniques that are associated with resorption, infection, and implant exposure. As an alternative, a calcium phosphate-based implant was developed and previously shown to potentially stimulate bone growth. We here uncover evidence of induced bone formation in 2 patients. Histological examination 9 months postoperatively showed multinuclear cells in the central defect zone and bone ingrowth in the bone-implant border zone. An increased expression of bone-associated markers was detected. The other patient was investigated 50 months postoperatively. Histological examination revealed ceramic materials covered by vascularized compact bone. The bone regenerative effect induced by the implant may potentially improve long-term clinical outcome compared with conventional techniques, which needs to be verified in a clinical study.

Effects of a formalized collaboration between plastic and orthopedic surgeons in severe extremity trauma patients; a retrospective study.

BACKGROUND: Severe trauma to the extremities often includes a combination of fractures and soft tissue injuries. Several publications support that the patient outcome is better when skeletal stabilization is followed by early soft-tissue coverage. In an effort to optimize the treatment of these patients, we established a formalized collaboration in 2008 between the Departments of reconstructive plastic surgery and orthopedics at the Karolinska University Hospital. METHODS: A retrospective review was conducted for all patients who had suffered severe extremity trauma and received either a free or a pedicled flap for extremity reconstruction. We compared the management of patients 0-4 years before and 0-4 years after the collaboration started especially with respect to; choice of flap, time to flap coverage, number of operations/revisions, total in-hospital stay. RESULTS: After initiation of the collaboration, the number of flaps increased from 13 flaps (5 free and 8 pedicled) to 44 flaps (21 free and 23 pedicled). Fewer postoperative revisions was seen, as well as shorter in-hospital stay. CONCLUSIONS: The present study highlights the importance of formalized collaboration between orthopedic and plastic surgeons in severe extremity trauma patients. The concept of an interdisciplinary approach has led to an increased number of trauma patients referred for plastic surgical consultation, an increased number of flaps, fewer postoperative revisions and shorter hospital stay.

Erg channel is critical in controlling cell volume during cell cycle in embryonic stem cells.

The cell cycle progression in mouse embryonic stem cells (mESCs) is controlled by ion fluxes that alter cell volume [1]. This suggests that ion fluxes might control dynamic changes in morphology over the cell cycle, such as rounding up of the cell at mitosis. However, specific channels regulating such dynamic changes and the possible interactions with actomyosin complex have not been clearly identified. Following RNAseq transcriptome analysis of cell cycle sorted mESCs, we found that expression of the K(+) ion channel Erg1 peaked in G1 cell cycle phase, which was confirmed by immunostaining. Inhibition of Erg channel activity caused loss of G1 phase cells via non-apoptotic cell death. Cells first lost the ability of membrane blebbing, a typical feature of cultured embryonic stem cells. Continued Erg inhibition further increased cell volume and the cell eventually ruptured. In addition, atomic force measurements on live cells revealed a decreased cortical stiffness after treatment, suggesting alterations in actomyosin organization. When the intracellular osmotic pressure was experimentally decreased by hypertonic solution or block of K(+) ion import via the Na, K-ATPase, cell viability was restored and cells acquired normal volume and blebbing activity. Our results suggest that Erg channels have a critical function in K(+) ion homeostasis of mESCs over the cell cycle, and that cell death following Erg inhibition is a consequence of the inability to regulate cell volume.