Causes of Hemodynamic Instability during Surgery

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Each year, an estimated 230 million surgical operations are performed around the world. The influence of hemodynamic instability (or shock) during surgery on patient mortality and morbidity in is a very important clinical issue (1). There are four major categories of hemodynamic instability/shock: hypovolemic, distributive, cardiogenic, and obstructive. Hypovolemic shock is due to intravascular volume loss, distributive shock is caused by inadequate perfusion of the body’s vital organs, cardiogenic shock is secondary to decreased intrinsic cardiac function, and obstructive shock arises from a blockage of systemic blood circulation (2). Two surgical procedures that are associated with a greater chance of intraoperative hemodynamic instability are pheochromocytoma removal and carotid artery stenting. Although surgery techniques and anesthetic care have progressed considerably in recent years, hemodynamic instability (HI) is still a common complication of the aforementioned procedures, and can also happen in other clinical situations, though rare. Thus, identifying significant risk factors for hemodynamic instability in patients is important for safe and effective perioperative care by anesthesiologists and surgeons.

A pheochromocytoma is a rare neuroendocrine tumor that originates from chromaffin cells of the adrenal medulla, with an incidence of approximately 0.3-0.5 cases per 100,000 person-years. Often, pheochromocytomas synthesize and secrete excessive amounts of catecholamines (norepinephrine, epinephrine and dopamine), which can cause hypertension, tachycardia, palpitations, and various organ complications. The main treatment strategy for pheochromocytoma is surgery (adrenalectomy). However, manipulation of the adrenal gland can trigger acute life-threatening intraoperative catecholamine release and a subsequent hypertensive crisis. According to current guidelines, patients with pheochromocytoma should undergo preoperative medical treatment consisting of α- and β-adrenergic blockers to prevent perioperative cardiovascular complications (3). In 2018, Jiang et al. conducted a study to identify risk factors for hemodynamic instability during surgery for pheochromocytoma in patients at a single institution in China (3). In this study, it was found that tumor diameter > 50 mm was an independent risk factor for intraoperative HI. Previous studies have shown that larger tumors tend to secrete greater amounts of catecholamines, which would naturally lead to an increase of intraoperative HI. The study also showed that diabetes/hyperglycemia was also a significant predictor of HI. Autonomic neuropathy and HI are known complications of uncontrolled diabetes. This existing predisposition to HI is exacerbated by the catecholamine surge produced during pheochromocytoma removal (3).

Carotid artery stenting (CAS) is an alternative to carotid endarterectomy (CEA) to treat carotid artery disease, with proven safety and efficacy in multiple trials due to its less invasive nature compared to CEA. According to the current guidelines, CAS is preferred for patients with contraindications against CEA (i.e. age >80, severe cardiac disease, previous radical neck surgery or radiotherapy) (4). Hemodynamic instability is also considered a common complication in surgery patients after CAS. In a 2019 study, Rubio et. al found that lesions involving the carotid bifurcation and the presence of hypertension requiring 2 or more antihypertensive medications were independent risk factors for perioperative HI (4). Stimulation

of the carotid sinus baroreceptors by balloon dilation and stent deployment at or near the carotid bifurcation can lead to increased vagal tone and parasympathetic, consequently causing hypotension and/or bradycardia. On a related note, the association between the presence of severe hypertension and perioperative HI suggests that patients with more refractory hypertension requiring multiple medications may be at increased risk for reflex hypotension following CAS. Future studies are required to investigate whether withholding some or all antihypertensive medications in patients on multiple medications reduces the risk of perioperative HI (4).



1. Abebe MM, Arefayne NR, Temesgen MM, Admass BA. Incidence and predictive factors associated with hemodynamic instability among adult surgical patients in the post-anesthesia care unit, 2021: A prospective follow up study. Ann Med Surg (Lond). 2022;74:103321. Published 2022 Jan 29. doi:10.1016/j.amsu.2022.103321

2. Standl T, Annecke T, Cascorbi I, Heller AR, Sabashnikov A, Teske W. The Nomenclature, Definition and Distinction of Types of Shock. Dtsch Arztebl Int. 2018;115(45):757-768. doi:10.3238/arztebl.2018.0757

3. Jiang M, Ding H, Liang Y, et al. Preoperative risk factors for haemodynamic instability during pheochromocytoma surgery in Chinese patients. Clin Endocrinol (Oxf). 2018;88(3):498-505. doi:10.1111/cen.13544

4. Rubio G, Karwowski JK, DeAmorim H, Goldstein LJ, Bornak A. Predicting Factors Associated with Postoperative Hypotension following Carotid Artery Stenting. Ann Vasc Surg. 2019;54:193-199. doi:10.1016/j.avsg.2018.06.005

Risk Factors for Intraoperative Hypotension

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Intraoperative hypotension (IOH) is a common complication during surgical procedures under anesthesia [2]. IOH can lead to adverse outcomes, including organ dysfunction, increased morbidity, and longer hospital stays. Studies have shown IOH during noncardiac surgery is associated with an increased risk of 30-day major adverse cardiac or cerebrovascular events [1]. The definition of IOH has long been debated, but a recent systematic review found that when mean arterial pressure (MAP) falls under 80 mmHg for greater than 10 minutes, end-organ injury can occur [3]. Identifying and understanding the associated risk factors for IOH is crucial for preventing and managing intraoperative hypotension effectively.  

The choice of anesthetic agents and techniques can significantly influence the risk of intraoperative hypotension. Certain drugs, such as volatile anesthetics, induction agents, and opioids, can cause dose-dependent hypotension [4]. Additionally, regional anesthesia techniques, such as epidurals and spinal blocks, which cause a sympathetic blockade, can lead to IOH. Anesthesiologists should carefully select anesthetic agents and techniques, considering the patient’s overall health, surgical requirements, and risk factors for hypotension. Some of these risk factors include older aged patients who may be more susceptible to IOH due to decreased cardiovascular reserve and altered baroreceptor function. Furthermore, those with comorbidities like hypertension, diabetes, and cardiovascular diseases are at higher risk for IOH. Certain medications, such as beta-blockers, alpha-2 agonists, and angiotensin-converting enzyme inhibitors, can impact blood pressure regulation intraoperatively, and careful monitoring of patients on these agents is warranted [5].  

Intraoperative hypotension must be treated based upon the underlying etiology. Thus, determining the underlying cause of hypotension is essential in management [4]. One important step in management is assessment of volume status for hypovolemia, whether due to preoperative fasting, blood loss, or inadequate fluid replacement. The duration of surgery and type of surgery are also variables that can affect hemodynamics. Longer surgeries and those involving significant blood loss such as vascular or orthopedic surgeries are associated with a higher risk of intraoperative hypotension. Prolonged exposure to anesthetic agents and mechanical ventilation causing high intrathoracic pressure can also affect hemodynamics during surgery [5]. Additionally, the position a patient is in during surgery can affect venous return and cardiac output. The use of advanced monitoring techniques, such as arterial line and cardiac output monitoring, can help detect IOH early [5]. Continuous monitoring allows for prompt adjustments and interventions, fluid administration, or use of first-line vasopressors like ephedrine, phenylephrine, and norepinephrine [4].  

Overall, intraoperative hypotension is a common and potentially serious complication during surgery. Identifying and mitigating risk factors is crucial for ensuring patient safety and positive outcomes. An individualized approach that includes optimizing preoperative conditions, selecting appropriate anesthetic agents, and vigilant monitoring during surgery is essential in minimizing the risk of IOH and optimizing perioperative care.  



  1. Bijker JB, van Klei WA, Kappen TH, van Wolfswinkel L, Moons KG, Kalkman CJ. Incidence of intraoperative hypotension as a function of the chosen definition: literature definitions applied to a retrospective cohort using automated data collection. Anesthesiology. 2007;107:213–220 
  2. Gregory, Anne MD, MSc, FRCPC*; Stapelfeldt, Wolf H. MD‚Ć; Khanna, Ashish K. MD, FCCP, FCCM‚Ä°,¬ß; Smischney, Nathan J. MD, MSc‚Äñ; Boero, Isabel J. MD, MS; Chen, Qinyu MS; Stevens, Mitali PharmD, BCPS#; Shaw, Andrew D. MB, FRCPC*,**. Intraoperative Hypotension Is Associated With Adverse Clinical Outcomes After Noncardiac Surgery. Anesthesia & Analgesia 132(6):p 1654-1665, June 2021.  
  3. Wesselink EM, Kappen TH, Torn HM, Slooter AJC, van Klei WA. Intraoperative hypotension and the risk of postoperative adverse outcomes: a systematic review. Br J Anaesth. 2018;121:706–721. 
  4. Lonjaret L, Lairez O, Minville V, Geeraerts T. Optimal perioperative management of arterial blood pressure. Integr Blood Press Control. 2014 Sep 12;7:49-59. doi: 10.2147/IBPC.S45292. PMID: 25278775; PMCID: PMC4178624. 
  5. Kouz K, Hoppe P, Briesenick L, Saugel B. Intraoperative hypotension: Pathophysiology, clinical relevance, and therapeutic approaches. Indian J Anaesth. 2020 Feb;64(2):90-96. doi: 10.4103/ija.IJA_939_19. Epub 2020 Feb 4. PMID: 32139925; PMCID: PMC7017666 

Wildfires and Health

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Although wildfires have occurred naturally for thousands of years, the intensity and frequency of these catastrophic events have increased in recent years due to climate change and human activities (1). In 2021 alone, over 60,000 wildfires burned more than 7 million acres, representing a 223% increase since 1983 (2). Additionally, human activities cause more than 85% of wildfires, resulting in billions of dollars of damage every year in the United States (2). These catastrophic natural disasters damage property and wildlife, but wildfire also pose significant short-term and long-term threats to human health.  

Immediate health consequences from wildfires stem from the exposure to flames and smoke. First, although wildfires are typically less fatal than home fires, exposure to wildfire flames can cause burns, injuries, and suffocation, which resulted in the deaths of 2,400 Americans between 1998 and 2017 (3). More often, however, the short-term health outcomes from wildfires arise from the exposure to smoke, which affects millions of Americans every year (4). Wildfire smoke contains a dangerous combination of carbon dioxide, carbon monoxide, hazardous air pollutants (HAP), and, crucially, particulate matter that is released into the air during the burning of vegetation (5). Wildfires produce a lot of small particulate matter, such as PM2.5, which is particles composed of various chemical compounds that measure less than 2.5 micrometers in diameter, that is particularly harmful (6). The microscopic size of the particles allows them to travel through air and become trapped deep in human lungs (6). Thus, exposure to particle pollution from wildfire smoke can cause the immediate manifestation of respiratory symptoms, including coughing, respiratory tract irritation, difficulty breathing, asthma exacerbations, reduced lung function, and bronchitis (6).  

Acute respiratory symptoms can persist for days following exposure and can spiral into serious conditions (6). The severity and longevity of health outcomes depends on the length of exposure to wildfire smoke and the vulnerability of the affected individuals (7). Children, elderly adults, and individuals with chronic conditions are most likely to suffer severe symptoms, hospitalizations, and, in some cases, death (7). Following the onset of acute respiratory symptoms, the damage to the inflammatory and respiratory systems caused by particle pollution can lead to serious conditions, including heart attack, heart failure, and stroke, especially in individuals with developing lungs, respiratory conditions, or cardiovascular disease (6). Additionally, conditions such as chronic obstructive pulmonary disease (COPD) and asthma can be exacerbated, leading to long-term lung damage and increased risk of respiratory infections (6).  

Years after the smoke has cleared and the flames have been extinguished, many wildfire survivors suffer from long-term health consequences (6). Although researchers have traditionally focused on the acute effects of wildfire exposure, some studies have documented chronic symptoms, especially in firefighters and residents of areas prone to wildfires. Two studies of wildfire survivors showed an increase in chronic bronchitis in both children and adults (8, 9); additionally, one study showed an increased risk of heart attack (9). Increased risk of cancer may also arise from wildfire exposure, though some studies have not found significant associations (10). Additionally, mental health conditions appear to plague survivors, with self-reported symptoms of post-traumatic stress disorder (PTSD), depression, and anxiety worsening in survivors compared to their pre-wildfire baseline (11). While the long-term effects of wildfires must be further investigated, research shows significant impacts to every aspect of human health. 

In the future, wildfires are expected to increase in severity and lethality due to climate change and human activities (1). The number of individuals exposed to PM2.5 in wildfire smoke is expected to rise, resulting in more cases of acute respiratory distress and, potentially, long-term consequences from particle pollution (4). Vulnerable individuals and residents of areas prone to wildfires remain at the highest risk for severe health consequences, though anyone exposed to wildfire flames and smoke can suffer both short-term and long-term outcomes. Despite this dire outlook, wildfires and their consequences may be decreased by cutting greenhouse gas emissions, improving wildfire management, and educating the public on safe practices and wildfire prevention (6).  




1: United States Environmental Protection Agency. 2022. Climate change indicators: wildfires. EPA. URL:,have%20increased%20since%20the%201980s.  

2: Martin, S. 2023. 2023 US wildfire statistics. Bankrate. URL:  

3: World Health Organization. 2023. Wildfires. WHO. URL:  

4: Milman, O. 2023. ‘Dramatic’ rise in wildfire smoke triggers decline in US air quality for millions. The Guardian. URL:  

5: Reid, C., Brauer, M., Johnston, F., Jerrett, M., Balmes, J., and Elliott, C. 2016. Critical review of health impacts of wildfire smoke exposure. Environmental Health Perspectives, vol. 124. DOI: 10.1289/ehp.1409277.  

6: Grant, E. and Runkle, J. 2022. Long-term health effects of wildfire exposure: a scoping review. The Journal of Climate Change and Health, vol. 6. DOI: 10.1016/j.2021.100110.  

7: United States Environmental Protection Agency. 2022. Which populations experience greater risks of adverse health effects resulting from wildfire smoke exposure? EPA. URL:  

8: Matz, C., Egyed, M., Xi, G., Racine, J., Pavlovic, R., Rittmaster, R., Henderson, S., and Stieb, D. 2020. Health impact of PM2.5 from wildfire smoke in Canada. Science of the Total Environment, vol. 725. DOI: 10.1016/j.scitotenv.2020.138506. 

9: Neumann, J., Amend, M., Anenberg, S., Kinney, P., Sarofim, M., Martinich, J., Lukens, J., Xu, J., and Roman, H. 2021. Estimating the PM2.5-related premature mortality and morbidity associated with future wildfire emissions in the western US. Environmental Research Letters, vol. 16. DOI: 10.1088/1748-9326/abe82b. 

10: O’Dell, K., Hornbrook, R., Permar, W., Levin, E., Garofalo, L., Apel, E., Blake, N., Jarnot, A., Pothier, M., Farmer, D., Hu, L., Campos, T., Ford, B., Pierce, J., and Fischer, E. 2020. Hazardous air pollutants in fresh and aged western US wildfire smoke and implications for long-term exposure. Environmental Science and Technology, vol. 54. DOI: 10.1021/acs.est.0c04497. 

11: Agyapong, V., Ritchie, A., Brown, M., Noble, S., Mankowski, M., Denga, E., Nwaka, B., Akinjise, I., Corbett, S., Moosavi, S., Chue, P., Silverstone, P., and Greensha, A. 2020. Long-term mental health effects of a devastating wildfire are amplified by sociodemographic and clinical antecedents in elementary and high school staff. Frontiers in Psychiatry, vol. 11. DOI: 10.3389/fpsyt.2020.00448. 




Encryption for Cybersecurity in Healthcare

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The security of healthcare data remains a challenge in institutions across the U.S. A recent Stanford University report estimates a 48% growth in medical data each year 1, from which stolen records can be sold for as much as $1,000 each on the black market 2. It is estimated that 50 million Americans had their sensitive health data breached in 2021 alone 3. There are many ways to protect healthcare information. This article will focus on encryption as a method for cybersecurity in the healthcare space. 

Cryptography is an indispensable tool used to protect information in any organization, enabling secure transmission over the Internet. Data encryption in healthcare specifically refers to the conversion of sensitive and confidential patient data into a coded language that can only be accessed by authorized individuals with a decryption key, improving cybersecurity. In this context, both artificial intelligence and quantum technology are transforming the health sector in regard to cybersecurity 4.  

Healthcare cloud computing, which is increasingly the norm, presents with a unique set of challenges. According to a recent meta-analytic review, data security, availability, and integrity, as well as information confidentiality and network security remain major challenges inherent to cloud security in healthcare 5 

However, data encryption, authentication, and classification represent powerful cybersecurity solutions that are important for healthcare data. Data encryption in particular can be applied to store and retrieve data from the cloud in order to ensure secure communication.  

It remains difficult for healthcare providers and their business associates to balance delivering quality care and keeping information systems accessible to providers with protecting patient privacy and meeting the strict regulatory requirements set forth by the U.S.’ Health Insurance Portability and Accountability Act (HIPAA) or the European Union’s General Data Protection Regulation (GDPR), among other regulations. 

In light of increasing regulatory requirements for healthcare data protection, healthcare organizations that take a proactive approach to implementing best practices for healthcare cybersecurity are best equipped for continued compliance and at lower risk of suffering costly data breaches. Best practices include but are not limited to educating healthcare staff, implementing data usage controls, restricting access to data and applications, securing mobile devices, and encrypting data. Alongside data encryption and other measures though, it remains equally important to conduct regular risk assessments, use off-site data backups, and regularly test the compliance of business associates 6. 

Most recently, in the spring of 2023, Vaultree, a major player in cybersecurity, announced a leap forward in healthcare data protection, introducing its industry-first fully functional data-in-use encryption solution to the sector 7. Combined with a software development kit and an encrypted chat tool, this technology aims to provide full-scale protection of sensitive patient data, even in the event of a breach, without compromising operational efficiency. 

Additional research and development remains to be carried out in the field of cybersecurity on encryption and beyond for healthcare data in order to optimize patient privacy and well-being. Further areas of development are sure to include, among other technologies, quantum computing as it relates to data encryption 8 



  1. Harnessing the Power of Data in Health.
  2. Patient medical records sell for $1K on dark web. Available at: (Accessed: 24th June 2023)
  3. Health data breaches swell in 2021 amid hacking surge, POLITICO analysis finds – POLITICO. Available at: (Accessed: 24th June 2023)
  4. Jayanthi, P. & Iyyanki, M. Cryptography in the Healthcare Sector With Modernized Cyber Security. in (2020). doi:10.4018/978-1-7998-2253-0.ch008
  5. Mehrtak, M. et al. Security challenges and solutions using healthcare cloud computing. Journal of Medicine and Life (2021). doi:10.25122/jml-2021-0100
  6. Healthcare Cybersecurity: Tips for Securing Private Health Data. Available at: (Accessed: 24th June 2023)
  7. Vaultree Sets a New Benchmark in Healthcare Cybersecurity with Industry-First, Fully Functional Data-In-Use Encryption Solution | Business Wire. Available at: (Accessed: 24th June 2023)
  8. Quantum Cryptography and the Health Sector. (2022).


Viscoelastic Testing in Anesthesia and Surgery

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Hemorrhage remains a major contributor to morbidity and mortality during the perioperative period. The swift diagnosis and treatment of coagulopathy is critical to the care of severely bleeding patients. Current methods for diagnosing coagulopathy, however, remain limited by long laboratory runtimes, a lack of information on specific abnormalities of the coagulation cascade, minimal in vivo applicability, and little ability to guide the transfusion of blood products. Viscoelastic testing may allow providers to gather data related to bleeding and coagulopathy before a patient undergoes anesthesia and surgery. 

Viscoelastic testing offers a promising solution to many of these challenges 1, helping with the care of severely bleeding patients in the context of major surgery, major trauma, or postpartum hemorrhage 2. In the perioperative period, two assays are most frequently used: kaolin thromboelastography (TEG)-based, and tissue factor–activated rotational thromboelastometry (ROTEM)-based viscoelastic monitoring. The three main goals of such viscoelastic testing assays are to predict bleeding, assess platelet function, and allow for perioperative testing to reduce transfusion 3. They thus provide a nuanced view of the elements of the coagulation system, allowing for the rapid administration of targeted therapy 3. Specifically, these assays can help guide basic decisions regarding the treatment of perioperative coagulopathy, including when the clinician should transfuse platelets, administer fibrinogen concentrate, or administer plasmatic coagulation factors 2 

However, it is critical to note that standard TEG/ROTEM assays are neither sensitive nor specific enough to adequately detect platelet inhibition, the effects of direct oral anticoagulants, or inherited bleeding disorders, such as cases of hemophilia or von Willebrand disease. Diagnoses of these specific conditions are better made preoperatively as part of a routine diagnostic workup 4.   

While viscoelastic testing remains a relatively novel method to assess coagulation status, evidence for its use appears favorable in reducing blood product transfusions, especially in cardiac surgery patients 1. Indeed, reviews of the literature, which is primarily focused on cardiac surgery patients, have demonstrated that transfusions of packed red blood cells, plasma, and platelets are all decreased in patients whose transfusions were guided by viscoelastic testing rather than by clinical assessment or conventional laboratory tests. More recent research has further confirmed that implementing transfusion algorithms based on the results of viscoelastic point-of-care coagulation testing can reduce transfusions and lead to improved patient outcomes 2.  Finally, meta-analytic data have corroborated that the use of viscoelastic testing in cardiac surgery patients can effectively minimize allogenic blood products exposure, dampen postoperative bleeding at 12 and 24 hours postoperatively, and reduce the need for redo surgery unrelated to surgical bleeding 5 

Overall mortality rates have also been shown to be lower in viscoelastic testing groups, while viscoelastic testing also appears to be cost-effective from a clinical standpoint 1.  

However, while results are promising, there remains a dearth of systematic, larger scale trials. Viscoelastic testing remains a relatively novel method, and further improvement and clinical validation of these broadly used basic assays in different surgery contexts are needed 2. 



  1. Shen, L., Tabaie, S. & Ivascu, N. Viscoelastic testing inside and beyond the operating room. J. Thorac. Dis. 9, S299–S308 (2017). doi: 10.21037/jtd.2017.03.85.
  2. Erdoes, G., Koster, A. & Levy, J. H. Viscoelastic Coagulation Testing: Use and Current Limitations in Perioperative Decision-making. Anesthesiology 135, 342–349 (2021). doi: 10.1097/ALN.0000000000003814.
  3. Agarwal, S. & Abdelmotieleb, M. Viscoelastic testing in cardiac surgery. Transfusion 60 Suppl 6, S52–S60 (2020). doi: 10.1111/trf.16075.
  4. Koscielny, J. et al. A practical concept for preoperative identification of patients with impaired primary hemostasis. Clin. Appl. Thromb. (2004). doi:10.1177/107602960401000301
  5. Meco, M. et al. Viscoelastic Blood Tests Use in Adult Cardiac Surgery: Meta-Analysis, Meta-Regression, and Trial Sequential Analysis. J. Cardiothorac. Vasc. Anesth. 34, 119–127 (2020). doi: 10.1053/j.jvca.2019.06.030.