The association between intraoperative low driving pressure ventilation and perioperative healthcare-associated costs: A retrospective multicenter cohort study.

STUDY OBJECTIVE: A low dynamic driving pressure during mechanical ventilation for general anesthesia has been associated with a lower risk of postoperative respiratory complications (PRC), a key driver of healthcare costs. It is, however, unclear whether maintaining low driving pressure is clinically relevant to measure and contain costs. We hypothesized that a lower dynamic driving pressure is associated with lower costs. DESIGN: Multicenter retrospective cohort study. SETTING: Two academic healthcare networks in New York and Massachusetts, USA. PATIENTS: 46,715 adult surgical patients undergoing general anesthesia for non-ambulatory (inpatient and same-day admission) surgery between 2016 and 2021. INTERVENTIONS: The primary exposure was the median intraoperative dynamic driving pressure. MEASUREMENTS: The primary outcome was direct perioperative healthcare-associated costs, which were matched with data from the Healthcare Cost and Utilization Project-National Inpatient Sample (HCUP-NIS) to report absolute differences in total costs in United States Dollars (US$). We assessed effect modification by patients' baseline risk of PRC (score for prediction of postoperative respiratory complications [SPORC] ≥ 7) and effect mediation by rates of PRC (including post-extubation saturation < 90%, re-intubation or non-invasive ventilation within 7 days) and other major complications. MAIN RESULTS: The median intraoperative dynamic driving pressure was 17.2cmH2O (IQR 14.0-21.3cmH2O). In adjusted analyses, every 5cmH2O reduction in dynamic driving pressure was associated with a decrease of -0.7% in direct perioperative healthcare-associated costs (95%CI -1.3 to -0.1%; p = 0.020). When a dynamic driving pressure below 15cmH2O was maintained, -US$340 lower total perioperative healthcare-associated costs were observed (95%CI -US$546 to -US$132; p = 0.001). This association was limited to patients at high baseline risk of PRC (n = 4059; -US$1755;97.5%CI -US$2495 to -US$986; p < 0.001), where lower risks of PRC and other major complications mediated 10.7% and 7.2% of this association (p < 0.001 and p = 0.015, respectively). CONCLUSIONS: Intraoperative mechanical ventilation targeting low dynamic driving pressures could be a relevant measure to reduce perioperative healthcare-associated costs in high-risk patients.

Role of anticoagulation therapy in modifying stroke risk associated with new-onset atrial fibrillation after non-cardiac surgery.

The role of antithrombotic therapy in the prevention of ischemic stroke after non-cardiac surgery is unclear. In this study, we tested the hypothesis that the association of new-onset postoperative atrial fibrillation (POAF) on ischemic stroke can be mitigated by postoperative oral anticoagulation therapy. Of 251,837 adult patients (155,111 female (61.6%) and 96,726 male (38.4%)) who underwent non-cardiac surgical procedures at two sites, POAF was detected in 4,538 (1.8%) patients. The occurrence of POAF was associated with increased 1-year ischemic stroke risk (3.6% versus 2.3%; adjusted risk ratio (RRadj) = 1.60 (95% confidence interval (CI): 1.37-1.87), P < 0.001). In patients with POAF, the risk of developing stroke attributable to POAF was 1.81 (95% CI: 1.44-2.28; P < 0.001) without oral anticoagulation, whereas, in patients treated with anticoagulation, no significant association was observed between POAF and stroke (RRadj = 1.04 (95% CI: 0.71-1.51), P = 0.847, P for interaction = 0.013). Furthermore, we derived and validated a computational model for the prediction of POAF after non-cardiac surgery based on demographics, comorbidities and procedural risk. These findings suggest that POAF is predictable and associated with an increased risk of postoperative ischemic stroke in patients who do not receive postoperative anticoagulation.

Association of reintubation and hospital costs and its modification by postoperative surveillance: A multicenter retrospective cohort study.

OBJECTIVE: We estimated hospital costs associated with postoperative reintubation and tested the hypothesis that prolonged surveillance in the post-anesthesia care unit (PACU) modifies the hospital costs of reintubation. DESIGN: Retrospective observational research study. SETTING: Two tertiary care academic healthcare networks in the Bronx, New York and Boston, Massachusetts, USA. PATIENTS: 68,125 adult non-cardiac surgical patients undergoing general anesthesia between 2016 and 2021. INTERVENTIONS: The exposure variable was unplanned reintubation within 7 days of surgery. MEASUREMENTS: The primary outcome was direct hospital costs associated with patient care related activities. We used a multivariable generalized linear model based on log-transformed costs data, adjusting for pre- and intraoperative confounders. We matched our data with data from the Healthcare Cost and Utilization Project-National Inpatient Sample (HCUP-NIS). In the key secondary analysis, we examined if prolonged postoperative surveillance, defined as PACU utilization (≥4 h) modifies the association between reintubation and costs of care. MAIN RESULTS: 1759 (2.6%) of patients were re-intubated within 7 days after surgery. Reintubation was associated with higher direct hospital costs (adjusted model estimate 2.05; 95% CI: 2.00-2.10) relative to no reintubation. In the HCUP-NIS matched cohort, the adjusted absolute difference (ADadj) in costs amounted to US$ 18,837 (95% CI: 17,921-19,777). The association was modified by the duration of PACU surveillance (p-for-interaction <0.001). In patients with a shorter PACU length of stay, reintubation occurred later (median of 2 days; IQR 1, 5) versus 1 days (IQR 0, 2; p < .001), and was associated with magnified effects on hospital costs compared to patients who stayed in the PACU longer (ADadj of US$ 23,444, 95% CI: 21,217-25,799 versus ADadj of US$ 17,615, 95% CI: 16,350-18,926; p < .001). CONCLUSION: Postoperative reintubation is associated with 2-fold higher hospital costs. Prolonged surveillance in the recovery room mitigated this effect. The cost-saving effect of longer PACU length of stay was likely driven by earlier reintubation in patients who needed this intervention.

Development of an automated, general-purpose prediction tool for postoperative respiratory failure using machine learning: A retrospective cohort study.

STUDY OBJECTIVE: Postoperative respiratory failure is a major surgical complication and key quality metric. Existing prediction tools underperform, are limited to specific populations, and necessitate manual calculation. This limits their implementation. We aimed to create an improved, machine learning powered prediction tool with ideal characteristics for automated calculation. DESIGN, SETTING, AND PATIENTS: We retrospectively reviewed 101,455 anesthetic procedures from 1/2018 to 6/2021. The primary outcome was the Standardized Endpoints in Perioperative Medicine consensus definition for postoperative respiratory failure. Secondary outcomes were respiratory quality metrics from the National Surgery Quality Improvement Sample, Society of Thoracic Surgeons, and CMS. We abstracted from the electronic health record 26 procedural and physiologic variables previously identified as respiratory failure risk factors. We randomly split the cohort and used the Random Forest method to predict the composite outcome in the training cohort. We coined this the RESPIRE model and measured its accuracy in the validation cohort using area under the receiver operating curve (AUROC) analysis, among other measures, and compared this with ARISCAT and SPORC-1, two leading prediction tools. We compared performance in a validation cohort using score cut-offs determined in a separate test cohort. MAIN RESULTS: The RESPIRE model exhibited superior accuracy with an AUROC of 0.93 (95% CI, 0.92-0.95) compared to 0.82 for both ARISCAT and SPORC-1 (P-for-difference < 0.0001 for both). At comparable 80-90% sensitivities, RESPIRE had higher positive predictive value (11%, 95% CI: 10-12%) and lower false positive rate (12%, 95% CI: 12-13%) compared to 4% and 37% for both ARISCAT and SPORC-1. The RESPIRE model also better predicted the established quality metrics for postoperative respiratory failure. CONCLUSIONS: We developed a general-purpose, machine learning powered prediction tool with superior performance for research and quality-based definitions of postoperative respiratory failure.

Adaptation and restructuring of an academic anesthesiology department during the COVID-19 pandemic in New York City: Challenges and lessons learned.

The novel SARS-CoV-2 pandemic starting in 2019 profoundly changed the world, and thousands of residents of New York City were affected, leading to one of the most acute surges in regional hospital capacity. As the largest academic medical center in the Bronx, Montefiore Medical Center was immediately impacted, and the entire hospital was mobilized to address the needs of its community. In this article, we describe our experiences as a large academic anesthesiology department during this pandemic. Our goals were to maximize our staff's expertise, maintain our commitment to wellness and safety, and preserve the quality of patient care. Lessons learned include the importance of critical care training presence and leadership, the challenges of converting an ambulatory surgery center to an intensive care unit (ICU), and the management of effective communication. Lastly, we provide suggestions for institutions facing an acute surge, or subsequent waves of COVID-19, based on a single center's experiences.

Increased incidence of post-operative respiratory failure in patients with pre-operative SARS-CoV-2 infection.

OBJECTIVE: While studies have reported increased post-operative pulmonary complications with SARS-CoV-2 infection, many are limited by use of historical controls or focus on less severe respiratory complications. We characterized the association between pre-operative SARS-CoV-2 infection and post-operative respiratory failure (PORF). DESIGN AND SETTING: This was a single center retrospective cohort study in New York City between March 14-June 14, 2020. PATIENTS: Exclusion criteria were age < 18-years, obstetric procedures, absence of SARS-CoV-2 PCR testing, and pre-operative respiratory failure. A total of 778 patients met criteria, of which 87 had SARS-CoV-2. MEASUREMENTS: The primary outcome, PORF, included inability to extubate for ≥24 h or unplanned re-intubation within 5 days. Multiple exposures were measured including SARS-CoV-2 infection 4 weeks before or 5 days after surgery. Multivariable logistic regression was performed to adjust for pre-operative hypoxemia, oxygen use, and pneumonia as well as tachycardia, gender, Charlson Comorbidity Index (CCI), Surgical Mortality Probability Model (S-MPM) index, and peri-operative blood transfusion. MAIN RESULTS: SARS-CoV patients had higher CCI (P = 0.007) and S-MPM scores (P = 0.02). The incidence of PORF was 16% versus 7% in uninfected comparators (P = 0.001). Amongst infected individuals, 39% exhibited symptoms of COVID-19 and PORF was more common in these patients compared to asymptomatic individuals (26% vs. 9%, P = 0.04). Adjusted analysis revealed increased odds of PORF with infection (OR 2.8, 95% CI 1.2-6.2). This persisted even when adjusting for probable mediators such as pre-operative hypoxemia. Infected patients also demonstrated increased adjusted odds of 30-day mortality (OR 3.5, 95% CI 1.4-9.1). CONCLUSIONS: Detection of SARS-CoV-2 infection within 4 weeks before or 5 days after surgery is associated with increased odds of 5-day PORF and 30-day mortality. This supports delaying elective surgery, but questions remain regarding the applicability of this recommendation for asymptomatic patients needing urgent or semi-urgent procedures such as oncologic surgery.

Carotid artery structure and hemodynamics and their association with adverse vascular events in left ventricular assist device patients.

Left ventricular assist devices (LVADs) are associated with major vascular complications including stroke and gastrointestinal bleeding (GIB). These adverse vascular events may be the result of widespread vascular dysfunction resulting from pre-LVAD abnormalities or continuous flow during LVAD therapy. We hypothesized that pre-existing large artery atherosclerosis and/or abnormal blood flow as measured in carotid arteries using ultrasonography are associated with a post-implantation composite adverse outcome including stroke, GIB, or death. We retrospectively studied 141 adult HeartMate II patients who had carotid ultrasound duplex exams performed before and/or after LVAD surgery. Structural parameters examined included plaque burden and stenosis. Hemodynamic parameters included peak-systolic, end-diastolic, and mean velocity as well as pulsatility index. We examined the association of these measures with the composite outcome as well as individual subcomponents such as stroke. After adjusting for established risk factors, the composite adverse outcome was associated with pre-operative moderate-to-severe carotid plaque (OR 5.08, 95% CI 1.67-15.52) as well as pre-operative internal carotid artery stenosis (OR 9.02, 95% CI 1.06-76.56). In contrast, altered hemodynamics during LVAD support were not associated with the composite outcome. Our findings suggest that pre-existing atherosclerosis possibly in combination with LVAD hemodynamics may be an important contributor to adverse vascular events during mechanical support. This encourages greater awareness of carotid morphology pre-operatively and further study of the interaction between hemodynamics, pulsatility, and structural arterial disease during LVAD support.

Activation of guanylate cyclase-C attenuates stretch responses and sensitization of mouse colorectal afferents.

Irritable bowel syndrome (IBS) is characterized by altered bowel habits, persistent pain and discomfort, and typically colorectal hypersensitivity. Linaclotide, a peripherally restricted 14 aa peptide approved for the treatment of IBS with constipation, relieves constipation and reduces IBS-associated pain in these patients presumably by activation of guanylate cyclase-C (GC-C), which stimulates production and release of cyclic guanosine monophosphate (cGMP) from intestinal epithelial cells. We investigated whether activation of GC-C by the endogenous agonist uroguanylin or the primary downstream effector of that activation, cGMP, directly modulates responses and sensitization of mechanosensitive colorectal primary afferents. The distal 2 cm of mouse colorectum with attached pelvic nerve was harvested and pinned flat mucosal side up for in vitro single-fiber recordings, and the encoding properties of mechanosensitive afferents (serosal, mucosal, muscular, and muscular-mucosal; M/M) to probing and circumferential stretch studied. Both cGMP (10-300 µM) and uroguanylin (1-1000 nM) applied directly to colorectal receptive endings significantly reduced responses of muscular and M/M afferents to stretch; serosal and mucosal afferents were not affected. Sensitized responses (i.e., increased responses to stretch) of muscular and M/M afferents were reversed by cGMP, returning responses to stretch to control. Blocking the transport of cGMP from colorectal epithelia by probenecid, a mechanism validated by studies in cultured intestinal T84 cells, abolished the inhibitory effect of uroguanylin on M/M afferents. These results suggest that GC-C agonists like linaclotide alleviate colorectal pain and hypersensitivity by dampening stretch-sensitive afferent mechanosensitivity and normalizing afferent sensitization.