Classification of A Nonroutine Surgical Event

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Despite efforts to improve perioperative patient safety over the past two decades, medical errors remain a significant cause of morbidity and mortality [1]. Safety improvement research has long been hindered by the weak relationship between healthcare interventions and adverse outcomes like morbidity and mortality [2]. These outcomes are rare in clinical research, limiting statistical power to demonstrate associations [2]. As a result, traditional methods of measuring morbidity and mortality have indicated inconsistent relationships with healthcare interventions [2]. Recently, an alternative to rare outcome measures, known as the “nonroutine event,” has been proposed [2]. 


A nonroutine event is defined as any aspect of clinical care perceived by clinicians or observers as a deviation from optimal care for a patient in a specific clinical scenario [3]. The concept of a nonroutine event includes not only the occurrence or near-occurrence of patient injury but also flawed care processes such as missing or broken equipment, delayed lab tests, insufficient training, and interpersonal communication errors [4,5]. It encompasses incidents that may not be directly linked to patient injury, which previously have been unreliably documented by reporting systems [4]. The nonroutine event reporting system is modeled after safety processes in the nuclear power industry where any deviation from optimal operating procedures is reported and investigated [4]. The foundation of this safety concept is represented by the principle of the “accident triangle” that relates frequent, low-importance events to infrequent, high-importance events such as morbidity and mortality [4]. 


The nonroutine event concept is broader than previous measurements used to assess clinical performance and medical error [2]. Because most nonroutine events do not involve errors by the care provider and few lead to patient injury, nonroutine events allow researchers to study underlying system processes without the negative implications of medical error [2,5].  


Initially, nonroutine events were used to retrospectively analyze workflow disruptions in anesthesia teams [5]. A 2002 study completed by researchers affiliated with the University of California, San Diego investigated the prevalence of nonroutine events in anesthesia care [6]. Anesthesiologists spend roughly 45% of the initial set-up time at the start of a normal workday on drug and fluid tasks, such as obtaining and filling syringes [6]. In observing anesthesiologists complete 68 drug and fluidrelated tasks, the researchers noted several nonroutine events including: difficulty finding anesthesia supplies, providers bumping into or tripping over IV poles or lines, malfunctioning infusion pumps, and blood leaking from IVs [6]. The results of the study suggested that many anesthesia drug and fluid tasks are inefficient, which may promote medical error [6]. 


The observed high incidence of nonroutine events has made it possible to collect prospective data to improve safety systems [6]. Today, nonroutine events are also used to assess the workflow of various surgical teams and team performance in the operating room [5]. A 2019 study completed at Children’s National Hospital in Washington, D.C. investigated the incidence of nonroutine events during pediatric trauma resuscitation [1]. The researchers reviewed 39 resuscitations and identified 337 nonroutine events [1]. The most frequent nonroutine event was failure to stabilize the cervical spine [1]. The results of the study highlighted common errors during pediatric trauma resuscitation that may lead to adverse outcomes [1]. 


Medical errors compromising patient safety and resulting in patient harm remain a significant health burden [1]. The nonroutine event concept provides a system to collect detailed information about types of deviations from optimal care and to show associations with long-term patient outcomes [4]. 




  1. Webman, R., Fritzeen, J., Yang, J., Ye, G., Mullan, P., & Qureshi, F. et al. (2016). Classification and team response to nonroutine events occurring during pediatric trauma resuscitation. Journal of Trauma and Acute Care Surgery, 81(4), 666-673. doi:10.1097/ta.0000000000001196 
  1. Lane-Fall, M., & Bass, E. (2020). “Nonroutine Events” as a Nonroutine Outcome for Perioperative Systems Research. Anesthesiology, 133(1), 8-10. doi:10.1097/aln.0000000000003125 
  1. Wacker, J. (2010). Managing Non-Routine Events in Anesthesia–A Concept to Measure and Improve Anesthesia Quality. Human Factors, 52(2):282-294. doi:10.1177/0018720809359178 
  1. Liberman, J., Slagle, J., Whitney, G., Shotwell, M., Lorinc, A., Porterfield, E., & Weinger, M. (2020). Incidence and Classification of Nonroutine Events during Anesthesia Care. Anesthesiology, 133(1), 41-52. doi:10.1097/aln.0000000000003336 
  1. Law, K. E., Hildebrand, E. A., Hawthorne, H. J., Hallbeck, M. S., Branaghan, R. J., Dowdy, S. C., & Blocker, R. C. (2019). A pilot study of non-routine events in gynecological surgery: Type, impact, and effect. Gynecologic Oncology, 152(2), 298-303. doi:10.1016/j.ygyno.2018.11.035 
  1. Weinger, M. (2002). Human Factors Research in Anesthesia Patient Safety: Techniques to Elucidate Factors Affecting Clinical Task Performance and Decision Making. Journal of The American Medical Informatics Association, 9(90061), 58S-63. doi:10.1197/jamia.m1229 

Retrospective vs. Prospective Cohort Studies

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Cohort design is a type of research design where investigators follow subjects over time, tracking their development through a set of health-related metrics [1]. As opposed to experimental investigations where researchers intervene to alter the conditions of studied populations, cohort studies involve no such intervention [2]. Instead, studies begin with identifying subjects to place them into two groups: exposed and non-exposed populations [3]. Over time, these groups are studied to determine the incidence, prevalence, prognosis, and potential causes of the central condition [3].  


Depending on what investigators hope to study, cohort studies are either prospective or retrospective. In a prospective cohort study, the cohort is selected and measured for various risk factors and exposures before the outcome occurs [2]. An example of a prospective study would be one where investigators seek to measure the likelihood of psoriasis patients experiencing side-effects due to anesthesia. A group of patients with psoriasis would be identified. These people would be tested to ensure that they do not already have conditions that complicate the administration of anesthesia. Then, the researchers would return to these patients over an extended period, tracking whether they have experienced side-effects during procedures since the start of the experiment. 


Conversely, retrospective studies aim to analyze a cohort that has already experienced the given outcome [2]. Experimenters collect all their data from records [1]. They will begin with each patient’s initial exposure and status at baseline and continue to follow up into the future, accumulating further data [1]. One retrospective study tracked the occurrence of pneumonia following the contraction of HIV by 2,628 women [4]. Every six months, the subjects would fill out a survey and provide a blood sample [4].  


Although the aforementioned study was retrospective, it was combined with data from a simultaneous prospective study to create a more complete picture of pneumonia incidence in HIV-positive individuals [4]. Neither prospective nor retrospective studies are infallible, so combining them may allow researchers to sidestep individual shortcomings 


Generally, prospective designs are considered more robust sources of valid evidence, but this is not always the case and can often come at a cost [5]. Prospective studies can provide researchers with accurate data collection that accounts for exposures, endpoints, and confounders [5]. But this high level of detail requires a vast investment of time and money. Follow-up periods are typically long, and investigators must follow-up with a large number of people [5]. Additionally, prospective designs run a greater risk of loss to follow-up, leading to lost data and reduced internal validity [5]. Especially in the context of rare diseases, where populations are already small, prospective studies may prove too inefficient and inappropriate for meaningful observation [5]. 


While retrospective methods offer a more time- and cost-efficient approach to cohort designs, the quality of available data can be a concern in these studies [5]. Because investigators have to work with existing data that may not have taken into account certain risk factors or exposures, these studies are more likely to be affected by confounding variables [2]. Information, recall, and selection biases may also reduce the validity of the results [3].  


Despite each approach’s shortcomings, many of these concerns can be avoided if investigators meticulously design their studies with these shortcomings in mind. Researchers believe that either form of cohort design, if designed carefully and thoroughly, can result in generalizable, accurate results with important implications for the study of medicine [5]. 




[1] M. S. Setia, “Methodology Series Module 1: Cohort Studies,” Indian Journal of Methodology, vol. 61, no. 1, p. 21-25, Jan-Feb 2016. [Online]. Available: 


[2] I. Oliveira, “Cohort studies: prospective and retrospective designs,” Students 4 Best Evidence via Cochrane, March 2019. [Online]. Available: 


[3] X. Wang and M. W. Kattan, “Cohort Studies: Design, Analysis, and Reporting,” Chest Journal, vol. 158, no. 1, p. S72-S78, July 2020. [Online]. Available: 


[4] S. R. Cole et al., “Combined analysis of retrospective and prospective occurrences in cohort studies: HIV-1 serostatus and incident pneumonia,” International Journal of Epidemiology, vol. 35, no. 6, p. 1442-1446, Aug 2006. [Online]. Available: 


[5] A. M. Euser et al., “Cohort Studies: Prospective versus Retrospective,” Nephron Clinical Practice, vol. 113, no. 3, p. c214-c217, Oct 2009. [Online]. Available: 


Managing Spinal Anesthesia-Induced Hypotension in Obstetrics

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Prevention and management of spinal anesthesia-induced hypotension is essential for preventing complications in the perioperative/peripartum period. In 2018, an international consensus statement was published that detailed guidelines for managing hypotension related to spinal anesthesia for cesarean sections. In summary, the publication recommended the following: vasopressors should be used routinely and preemptively, alpha-agonist drugs such as phenylephrine are preferred as first-line agent due to abundance of data on their use, left uterine displacement and colloid preloading or crystalloid co-loading should be routinely performed, and systolic blood pressure goal should be kept within 90% of baseline.


Researchers also recommended that a phenylephrine infusion should be started at 25-50mcg/min just after spinal injection (with a lower dosing recommended for pre-eclamptic patients who exhibit less hypotensive response), and tachycardia and bradycardia should be avoided and treated with fluids or beta-agonist respectively. Significant bradycardia with hypotension may warrant use of ephedrine or an anticholinergic, and circulatory collapse should be promptly treated with epinephrine.2


Of note, when compared to physician-controlled infusions, smart pumps and double-drug infusions may yield better hemodynamics. At least three studies have suggested that norepinephrine, when delivered via smart pump, may improve maternal and fetal physiology, but studies comparing phenylephrine and norepinephrine using standard pumps are lacking.3-5 Such modalities perform optimally when combined with continuous non-invasive blood pressure monitoring, however, patient safety in the case of artifactual measurements needs more study as well. Regarding monitoring, standard ASA monitors are required and non-invasive blood pressures are ideally taken every 1-2 minutes as equipment/resources allow. Regarding resource-poor care areas, it is considered unreasonable to proceed with spinal blockade without vasopressor and anticholinergics readily available. For the novice provider, a fixed-rate vasopressor infusion with concurrent boluses as needed has been found to be an effective alternative to provider-managed titration of the infusion.


Patients with cardiac disease should be receive individualized care (choice of vasopressor, monitors, anesthetic technique, etc.) based on the entire clinical picture, taking into account their baseline physiology and expected changes related to surgery/labor, anesthesia, and delivery. Single-shot spinal blocks in the setting of cardiac disease pose increased risk of hemodynamic instability compared to combined low-dose combined spinal/epidural or epidural-only techniques. This is due to the quick-onset of sympathectomy seen with full-dose spinal anesthesia. Controlled titration of neuraxial blockade is recommended for the majority of these types of cases.


Results of a recently published survey from Ireland indicate that phenylephrine is the most widely used vasopressor currently. A concerning finding is that ~80% of the 15 reporting centers did not routinely maintain heart rate at baseline or use the rate as a surrogate for cardiac output. Following publication of the aforementioned consensus statement, two of the reporting centers changed practice to use phenylephrine primarily. Of note, a significant number of centers reported not using phenylephrine infusions due to fear of precipitating bradycardia and/or low cardiac output. Only 3 centers had a departmental protocol for management of spinal anesthesia-induced hypotension and only 2 changed practice based on the consensus statement, heralding a need for more support, resources, and assessment of the barriers to implementation. Furthermore, some aspects of the guideline can be improved when more evidence becomes available, such as the recommendations on ephedrine for bradycardia, smart infusions, or fluid pre/co-loading.1


Potential advances in the management of spinal hypotension include the search for optimal vasopressors or combinations of drugs; advances in monitoring to allow rapid assessment of risk of hypotension, cardiac output, volume status, etc.; and genetic studies to predict individual responses to vasopressors.




1. ffrench-O’Carroll R, Tan T. National survey of vasopressor practices for management of spinal anaesthesia-induced hypotension during caesarean section. International Journal of Obstetric Anesthesia. 2020.  doi:10.1016/j.ijoa.2020.09.003


2. Kinsella SM, Carvalho B, Dyer RA, et al. International consensus statement on the management of hypotension with vasopressors during caesarean section under spinal anaesthesia. Anaesthesia. 2018;73(1):71-92.  doi:10.1111/anae.14080


3. Ngan Kee WD. Norepinephrine for maintaining blood pressure during spinal anaesthesia for caesarean section: A 12-month review of individual use. International Journal of Obstetric Anesthesia. 2017;30:73-74. doi:10.1016/j.ijoa.2017.01.004


4. Ngan Kee WD, Khaw KS, Tam Y, Ng FF, Lee SW. Performance of a closed-loop feedback computer-controlled infusion system for maintaining blood pressure during spinal anaesthesia for caesarean section: A randomized controlled comparison of norepinephrine versus phenylephrine. Journal of Clinical Monitoring and Computing. 2017;31(3):617-623. doi:10.1007/s10877-016-9883-z


5. Ngan Kee WD, Lee SWY, Ng FF, Tan PE, Khaw KS. Randomized double-blinded comparison of norepinephrine and phenylephrine for maintenance of blood pressure during spinal anesthesia for cesarean delivery. Anesthesiology. 2015;122(4):736-745. doi:10.1097/ALN.0000000000000601

The Effect of Vitamin Levels on Surgery Outcomes

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The importance of vitamins for overall health has long been recognized [1]. Recent studies have found that optimization of vitamin levels prior to surgery is associated with improved surgical outcomes, leading to an increased awareness of the relationship between nutrition and recovery from surgery [1]. 

The influence of vitamin D levels on post-surgical outcomes has recently become a research topic of interest [2]. Vitamin D is a fat-soluble steroid hormone that is important for musculoskeletal health, playing a role in over 300 metabolic pathways [2]. Epidemiological studies have demonstrated that vitamin D is both cardioprotective and neuroprotective [3]. Additionally, it plays a role in innate and acquired immunity [3]. The recommended circulating vitamin D level is >75 nmol/L [4]. Vitamin D deficiency is most commonly caused by inadequate sun exposure and can lead to rickets in children and exacerbated osteopenia, osteoporosis, and fractures in adults [4]. Deficiencies are also associated with an increased risk of cancer, autoimmune diseases, hypertension, and infectious disease [4]. In cases of low vitamin D serum concentrations, vitamin D supplements are effective for maintaining healthy blood concentrations [4]. Higher vitamin D levels are associated with decreased risk of in-hospital mortality and morbidity [3]. 

A 2013 study completed by researchers at the University of Ottawa found that vitamin D deficiency contributes to secondary organ pathophysiology, prolonged stays in the ICU, and worse outcomes in critically ill patients [5]. The researchers focused on children with congenital heart disease (CHD), a high-risk pediatric population [5]. Post-operatively, patients with CHD commonly experience pronounced systemic inflammation, coagulopathy, respiratory failure, electrolyte disturbances, arrhythmia, myocardial dysfunction, kidney failure, and infection [5]. Vitamin D supplementation prior to surgery was determined to be an ideal intervention for improving post-surgical outcomes in children with CHD [5]. 

Similarly, a 2019 study led by researchers at the University of Edinburgh and Trinity College Dublin found strong evidence of an association between lower vitamin D levels and adverse colorectal cancer survival following surgical resection [6]. The results of the study also pointed to a strong genotype-specific effect of vitamin D, with a post-surgical survival association greatest in those with a single nucleotide polymorphism within the VDR gene sequence (rs11568820) [6]. 

The impact of other vitamins on surgical outcomes continues to be explored [7]. It is known that vitamin C is a key requirement for proper wound healing [7]. Sufficient levels of vitamin C are necessary for protocollogen hydroxylase enzyme activity, which produces collagen, the most abundant protein in the body [7]. Vitamin A has also been found to have significant wound-healing activity [7]. Vitamin A is important for proper functioning of the inflammatory response and synthesis of collagen and ground substances [7]. Lastly, vitamin K has been linked to decreased post-operative bleeding [8]. In patients receiving a left ventricular assist device (LVAD), bleeding more than 48 hours post-implant occurred in only 5% of pre-operative vitamin-K treated patients as opposed to 26% of patients not treated with vitamin K [8]. 

Optimization of nutritional state, including vitamin levels, prior to surgery leads to improved surgical outcomes [1]. As the body of literature showing the connection between vitamin levels and surgical outcomes grows, nutritional screening protocols should be considered in the pre-operative evaluation of patients [1]. 




  1. Evans, D., Martindale, R., Kiraly, L., & Jones, C. (2013). Nutrition Optimization Prior to Surgery. Nutrition in Clinical Practice, 29(1), 10-21. doi:10.1177/0884533613517006 
  2. Iglar, P., & Hogan, K. (2015). Vitamin D status and surgical outcomes: a systematic review. Patient Safety in Surgery, 9(1). doi:10.1186/s13037-015-0060-y 
  3. Turan, A., Hesler, B., You, J., Saager, L., Grady, M., & Komatsu, R. et al. (2014). The Association of Serum Vitamin D Concentration with Serious Complications After Noncardiac Surgery. Anesthesia & Analgesia, 119(3), 603-612. doi:10.1213/ane.0000000000000096 
  4. Holick, M., & Chen, T. (2008). Vitamin D deficiency: a worldwide problem with health consequences. The American Journal of Clinical Nutrition, 87(4), 1080S-1086S. doi:10.1093/ajcn/87.4.1080s 
  5. McNally, J., & Menon, K. (2013). Vitamin D deficiency in surgical congenital heart disease: Prevalence and relevance. Translational Pediatrics, 2(3), 99-111. doi:10.3978/j.issn.2224-4336.2013.07.03 
  6. Vaughan-Shaw, P.G., Zgaga, L., Ooi, L. Y., et al. (2019). Low plasma vitamin D is associated with adverse colorectal cancer survival after surgical resection, independent of systemic inflammatory response. BMJ, 69(1), 103-111. doi:10.1136/gutjnl-2018-317922 
  7. Rahm, D. (2004). A guide to perioperative nutrition. Aesthetic Surgery Journal, 24(4), 385-390. doi:10.1016/j.asj.2004.04.001 
  8. Kaplon, R., Gillinov, A., Smedira, N., Kottke-Marchant, K., Wang, I., Goormastic, M., & McCarthy, P. (1999). Vitamin K reduces bleeding in left ventricular assist device recipients. The Journal of Heart and Lung Transplantation, 18(4), 346-350. doi:10.1016/s1053-2498(98)00066-7 

Effects of Obesity on Health: From Anesthesia to Vaccines 

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40% of Americans have a body mass index (BMI) of 30 or more, suggesting that they are obese [1]. Although scientists agree that factors other than BMI may more accurately describe obesity–such as waist circumference, waist-hip ratio, and total body fat–it is undeniable that a large amount of the US population suffers from obesity [2]. Unfortunately, obesity is associated with a higher risk of several health concerns, including diabetes, cardiovascular disease, and complications with anesthesia [1]. Some of these concerns are lesser known but essential for medical practitioners to be aware of when treating their patients.  


Because obesity is associated with several comorbidities, anesthesiologists must be aware of these conditions when sedating obese patients [2]. For instance, there is a negative correlation between obesity and respiratory function; many obese patients have low lung volumes, decreased airway compliances, and diaphragmatic restriction (caused by visceral fat) [2]. Additionally, obesity also puts patients at a higher risk of cardiovascular and obstructive sleep apnea-associated complications [2, 3]. Other studies have found that obesity is independently associated with poorer anesthesia outcomes [4].  It is crucial that anesthesiologists be consulted preoperatively and that a multidisciplinary team plan any major surgeries for obese patients [2]. 


The correlation between obesity and the development of various cancers has also been widely studied. According to a comprehensive 2007 study, obesity is associated with higher incidences of a variety of cancers, including endometrial, kidney, pancreatic, postmenopausal breast, colorectal, and esophageal cancer [5]. Another more recent form of cancer linked to obesity is thyroid cancer: researchers have found that patients with higher BMIs have larger tumors and greater rates of multifocality [6]. Unfortunately, obese people with cancer experience much more difficult recoveries and lower chances of survival [5]. The mechanisms guiding these correlations are not entirely understood, making this a crucial topic to address considering the growing rate of global obesity. 


Most recently, the link between obesity and COVID-19 has been a subject of much discussion. In the past, obese people have been at greater risk of complications from infectious diseases than non-obese populations and less receptive to vaccines [1]. This is due to the greater amount of adipose fat that obese people carry [7]. Excess adipose fat can result in chronic inflammation, which diminishes the efficacy of the specialized inflammation triggered by the immune system and/or vaccines in response to an infection [7]. Adipose fat can also serve as a reservoir for viruses [8]. These observations may help explain the greater rates of COVID-19 infection, hospitalization, and death experienced by obese patients [7]. Even when a vaccine is developed for the novel coronavirus, obese patients will require specialized attention, given these immune inhibitions. 


Ultimately, obesity can result in a variety of health difficulties: cardiovascular problems, respiratory issues, cancers, and infectious diseases. Especially during the pandemic, medical professionals must work to closely monitor their obese patients, both in and out of surgery, to promote the best possible outcomes. 




[1] S. Varney, “America’s Obesity Epidemic Threatens Effectiveness of Any COVID Vaccine,” KHN, August 6, 2020. [Online]. Available: 


[2] S. Sharma and L. Arora, “Anesthesia for the Morbidly Obese Patient,” Anesthesiology Clinics, vol. 38, no. 1, p. 197-212, March 2020. [Online]. Available: 


[3] A. De Jong et al., “How can I manage anaesthesia in obese patients?,“ Anaesthesia Critical Care & Pain Medicine, vol. 39, no. 2, p. 229-238, April 2020. [Online]. Available: 


[4] S. K. Park, H.K. Yoon, and W. H. Kim, “Obesity and spinal anesthesia outcomes,” Anesthesiology Clinics, vol. 33, no. 6, p. 704, December 2019. [Online]. Available: 


[5] M. Patlak and S. J. Nass, The Role of Obesity in Cancer Survival and Recurrence, 1st ed. Washington, D.C., USA: The National Academies Press, 2012, ch. 1, p. 1-4.  


[6] S. Zhao et al., “Association of obesity with the clinicopathological features of thyroid cancer in a large, operative population: A retrospective case-control study.,” Medicine, vol. 98, no. 50, p. e18213, July 2020. [Online]. Available: 


[7] J. V. V. de Siqueira et al., “Impact of obesity on hospitalizations and mortality, due to COVID-19: A systematic review,” Obesity Research & Clinical Practice, vol. 14, no. 5, p. 398-403, July 2020. [Online]. Available: 


[8] M. Banerjee et al., “Obesity and COVID-19: A Fatal Alliance,” Indian Journal of Clinical Biochemistry, vol. 35, no. 4, p. 410-417, July 2020. [Online]. Available: