Adverse events in the ICU: building and sustaining an organizational culture of patient safety

More than two decades ago, the Institute of Medicine highlighted the need to create safer health care systems. Medical errors were found to be the eighth most common cause of hospital mortality in the US according to this report (1). Errors leading to adverse outcomes are prone to occur in patient care environments that provide multifaceted care, employing life-support systems including ICUs, emergency departments, and operation theaters (2). The patient population involved have complex underlying disease processes with limited physiological reserves, and often require multiple interventions, making them particularly vulnerable to errors (1). Adverse events or critical incidents have been variously defined. They represent unintended events consequent to failure of healthcare management, including human, organizational or equipment error that lead to actual patient harm or have the potential to cause harm (3). 

Incidence of adverse events 

There is wide variation in the incidence of adverse events in ICUs, with some studies reporting such events in up to 20–31% of admissions (4,5). The high variability of adverse events reported may be due to differences in study settings, the presence of inherent safety systems, and a culture of transparency that may encourage reporting. However, adverse events are known to occur more commonly in high-acuity settings compared to other areas of the hospital where the level of care is less labor-intensive (6). 

Are errors that lead to adverse events and potential patient harm, especially in vulnerable areas of healthcare, preventable? Does reporting adverse events improve patient safety? 

Types of adverse events 

Several studies have evaluated the nature and types of adverse events and their impact on patient outcomes in critically ill patients. A prospective observational study analyzed adverse events in the multidisciplinary and coronary care ICUs of a tertiary academic hospital (7). Patients were followed up until transfer from the ICU, discharge, or death. Data regarding the patients and the staff involved were anonymized. An adverse event was defined as any injury that occurred due to medical management. The study reported 120 adverse events in 1490 patient days (80.5 per 1000 patient-days). Of these, 104 were classified as severe or significant and 16 as life-threatening or fatal. The most common adverse events were respiratory (19%), nosocomial infections (15%), cardiovascular (12%), or skin and soft tissue-related (9%). Fifty-six adverse events (47%), were drug-related; among these 19 (33.9%) were considered preventable. Serious medical errors, defined as errors that caused harm or had the potential to do so were observed on 223 occasions (149.7 per 1000 patient-days). Of these, 24 (11%) were deemed to be potentially life-threatening. Among the serious medical errors, 78% were drug-related. This study revealed that serious medical errors that result in patient harm or have the potential to do so are common among critically ill patients. Most of the errors emanated from failure to perform a plan of action as intended. 

A retrospective cohort study evaluated adverse events in 49,447 admissions to 30 ICUs over a 3-year period (8). Among these patients, 25.4% of ICU admissions experienced at least one documented adverse event (45.3 per 1000 hospital-days). The most common adverse events included respiratory-related complications (9.5 per 100 admissions) and nosocomial infections (8.8 per 100 admissions). Other reported events related to surgery, hemorrhagic incidents, delirium, complications related to fluid management, drug-related events, and decubitus ulcers. Less common adverse events included anesthesia-related, endocrine, and metabolic complications. 

Harris et al. assessed the impact of a new card-based system on patient safety event reports in three ICUs in the US. In this before-after study, the introduction of the new reporting system led to a significantly higher number of reports compared to the pre-existing web-based system of reporting. The authors analyzed the types of errors reported under the card-based system. The most common errors (33.6%) related to the conduct, administration, or interpretation of diagnostic tests, therapeutic interventions not related to the administration of medication, and procedure-related adverse events. These were collectively termed events related to “test, treatment, and procedure”. The second most common type of error was related to the administration of medication (28.9%). Other adverse events reported included laboratory events, complications related to intravenous lines, equipment errors, delays and errors involving blood product administration, events related to patient behavior and psychiatric management, surgical complications, and falls (9). 

Molina et al. analyzed adverse events over a 1-year period in a 12-bedded ICU from a university hospital in Colombia. A total of 48 patients experienced 178 adverse events during the study period. The most common adverse events noted included pressure ulcers, equipment-related complications, skin and soft tissue injuries, hypotensive episodes due to drug error, nosocomial pneumonias, hemorrhage related to surgical procedures, respiratory system-related events, and surgical site infections. Most of the adverse events were considered preventable. 

Does the type of adverse events differ between medical compared to surgical ICUs? Sinopoli et al. compared characteristics and outcomes from adverse events between medical and surgical ICUs in a prospective observational study conducted over a 2-year study period (10). The incidence of adverse events was relatively higher among surgical patients. The authors observed no significant difference between the characteristics of adverse events reported between medical and surgical patients. A significant difference between the two groups of patients was noted only in three of 11 domains. Events related to device or equipment, lines, tubes, or drains were more common in surgical patients; however, events related to computerized clinician order entry were more common among medical patients. Physical injury occurred in 15%, while prolonged ICU stay was observed in 10% of patients. Less than 2% of cases resulted in a fatal outcome. 

Chacko et al. evaluated the type and frequency of critical incidents in a multidisciplinary ICU in India. During the 33-month study period, 280 adverse events were reported among 1918 patients admitted to the ICU, with a frequency of 3.4 incidents per 100 patient-days. Airway-related incidents were the most common (32.8%), followed by line-related (21.8) and drug-related (15%) incidents (2).

Outcomes related to adverse events 

Adverse events commonly occur in the ICU setting; the frequency of events may be substantially higher considering the likelihood of underreporting. It is important to evaluate the outcomes of patients who experience adverse events. 

Cantor et al. retrospectively studied adult patients who were admitted to the ICU at The Ottawa Hospital in Canada over a 5-year period (11). Adverse events occurred in 6,070/17,173 (35.4%) patients admitted during the study period. The in-hospital mortality rate was significantly higher in patients who experienced adverse events compared to those who did not (26.2% vs. 18.4%, P < .001).  After control of variables including age, gender, and comorbidity score by multivariable logistic regression, adverse events resulted in a 13% higher hospital mortality (adjusted OR = 1.13, 95% CI: 1.04–1.22). Furthermore, the duration of stay in ICU and hospital was also significantly longer in patients who experienced adverse events. 

Baker et al. studied adverse events in 20 acute care hospitals in Canada, including community and teaching hospitals (12). Adverse events were noted in 7.5 per 100 hospital admissions [95% confidence interval (CI) 5.7–9.3]. On review of 858 case records, 1133 adverse events were noted. Death, disability at discharge, or prolonged stay in hospital was observed in 401 (46.7%) of cases. Overall, 255 case records revealed one or more adverse events that were considered to have resulted from medical management and were likely to be preventable. Most adverse events did not lead to physical impairment or disability. Permanent disability was noted in 15/289 (5.2%) adverse events, while 46 (15.9%) resulted in death. Based on the judgment of physician reviewers, the 255 patients who experienced adverse events required 1521 extra days in hospital due to these events. 

An Italian study analyzed adverse events from four ICUs of an academic hospital over a 4-year period (13). The adverse events rate was 1.7/100 ICU admissions with 2.86 incidents/1000 ICU days. The most common adverse events were related to medication or intravenous fluids (21.9%) and resources and organizational management (21.9%). This was followed by malfunction of equipment (8.1%), events related to clinical processes or procedures (11.3%), and documentation error (8.8%). Medication errors commonly arose from incorrect dosing, route of administration, infusion rates, and administration of wrong medication.   

Adverse outcomes following critical incidents were also uncommon in the study by Chacko et al; 88.6% of incidents did not lead to harm. Some degree of harm occurred in 11.4% of incidents; a minor physiological change occurred in 6.4%, and a major physiological change in 3.6% of incidents. Four deaths were attributed to critical incidents, all associated with airway-related incidents (2).

Are adverse events preventable?

Although there is increased awareness of the importance of reporting in recent years, the incidence of adverse events appears to be largely unchanged. This is perhaps due to increased reporting arising from an improved safety culture; however, there is plenty of room to reduce harm from adverse events in critically ill patients. The key to improved patient safety would be to address lacunae in organizational systems that lead to errors. Long shifts without adequate breaks in between may contribute to lapses resulting from overwork. Interns who worked 24-hour shifts or longer were more likely to commit serious errors compared to shorter shifts (14). Diagnostic and medication errors were particularly likely during long work shifts. The study suggested that shortening the duration of shifts may enable the reduction of serious errors in the ICU. 

A conceptual model aimed to improve physician compliance with five evidence-based recommendations during central venous catheter insertion (15). These included handwashing, use of barrier precautions, skin preparation with chlorhexidine, avoidance of the femoral vein, and expeditious removal of unnecessary catheters. This multi-pronged strategy resulted in significantly fewer catheter-related bloodstream infections during an 18-month period. A lower incidence of such infections could result in reduced morbidity and cost of care. Forster et al. identified 56 adverse events in a study including 207 patients. One in five adverse events was considered preventable. The preventable adverse events related to nosocomial infections (35%), therapeutic errors (22%), and procedure-related complications (26%). Surgical complications were least likely to be preventable. An optimal strategy should focus on identifying preventable errors and the incorporation of system-based measures aimed to reduce such errors. A safer ICU environment calls for exploring the trigger for adverse events, regular system reviews, and revision of processes that culminated in, or contributed to adverse events. The impact of system modifications must also be monitored to ensure efficacy and improved patient safety. 

Key points

  • Adverse events commonly occur in the ICU setting. The underlying severity of illness, with the requirement for multi-faceted support systems, make critically ill patients particularly vulnerable to treatment-related errors
  • Commonly reported adverse events in critically ill patients include those related to airway management, drug errors, intravenous fluid administration, procedure-related errors, and nosocomial infections
  • Although deleterious clinical outcomes are uncommon, adverse events have been associated with an increase in hospital mortality and length of stay 
  • A significant proportion of adverse events may be preventable. Corrective measures should be aimed at establishing system-based strategies that enhance patient safety. The onus must be on the prevention of a recurrence of adverse events and not on apportioning blame
  • Identification of adverse events is the first important step towards creating a safe patient environment. Emphasis must be laid on a transparent system that encourages reporting without the fear of punishment or reprimand. An anonymized system that does not require details of the patient or staff involved may facilitate reporting of adverse events
  • Human errors may be triggered by distractions, haste, fatigue, and working under stressful situations, while staff inexperience aggravates the possibility of error. Adequate training is of crucial importance in the management of critically ill patients, who are particularly prone to adverse consequences, given their limited physiological reserves  
  • It is also important to identify and follow up on “near-misses”, as they offer valuable experience to learn from and act towards improving patient safety 


1.         Institute of Medicine (US) Committee on Quality of Health Care in America. To Err is Human: Building a Safer Health System [Internet]. Kohn LT, Corrigan JM, Donaldson MS, editors. Washington (DC): National Academies Press (US); 2000 [cited 2022 May 29]. Available from:

2.         Chacko J, Raju HR, Singh MK, Mishra RC. Critical Incidents in a Multidisciplinary Intensive Care Unit. Anaesth Intensive Care. 2007 Jun;35(3):382–6. 

3.         Pagnamenta A, Rabito G, Arosio A, Perren A, Malacrida R, Barazzoni F, et al. Adverse event reporting in adult intensive care units and the impact of a multifaceted intervention on drug-related adverse events. Ann Intensive Care. 2012 Dec;2(1):47. 

4.         Bracco D, Favre JB, Bissonnette B, Wasserfallen JB, Revelly JP, Ravussin P, et al. Human errors in a multidisciplinary intensive care unit: a 1-year prospective study. Intensive Care Med. 2001 Jan;27(1):137–45. 

5.         Osmon S, Harris CB, Dunagan WC, Prentice D, Fraser VJ, Kollef MH. Reporting of medical errors: an intensive care unit experience. Crit Care Med. 2004 Mar;32(3):727–33. 

6.         Sauro KM, Machan M, Whalen-Browne L, Owen V, Wu G, Stelfox HT. Evolving Factors in Hospital Safety: A Systematic Review and Meta-Analysis of Hospital Adverse Events. J Patient Saf. 2021 Dec 1;17(8):e1285–95. 

7.         Rothschild JM, Landrigan CP, Cronin JW, Kaushal R, Lockley SW, Burdick E, et al. The Critical Care Safety Study: The incidence and nature of adverse events and serious medical errors in intensive care*: Critical Care Medicine. 2005 Aug;33(8):1694–700. 

8.         Sauro KM, Soo A, Quan H, Stelfox HT. Adverse Events Among Hospitalized Critically Ill Patients: A Retrospective Cohort Study. Medical Care. 2020 Jan;58(1):38–44. 

9.         Harris CB, Krauss MJ, Coopersmith CM, Avidan M, Nast PA, Kollef MH, et al. Patient safety event reporting in critical care: A study of three intensive care units*: Critical Care Medicine. 2007 Apr;35(4):1068–76. 

10.       Sinopoli DJ, Needham DM, Thompson DA, Holzmueller CG, Dorman T, Lubomski LH, et al. Intensive care unit safety incidents for medical versus surgical patients: A prospective multicenter study. Journal of Critical Care. 2007 Sep;22(3):177–83.

11.       Cantor N, Durr KM, McNeill K, Thompson LH, Fernando SM, Tanuseputro P, et al. Increased Mortality and Costs Associated with Adverse Events in Intensive Care Unit Patients. J Intensive Care Med. 2022 Mar 3;088506662210849. 

12.       Baker GR. The Canadian Adverse Events Study: the incidence of adverse events among hospital patients in Canada. Canadian Medical Association Journal. 2004 May 25;170(11):1678–86. 

13.       Danielis M, Bellomo F, Farneti F, Palese A. Critical incidents rates and types in Italian Intensive Care Units: A five-year analysis. Intensive and Critical Care Nursing. 2021 Feb;62:102950. 

14.       Landrigan CP, Rothschild JM, Cronin JW, Kaushal R, Burdick E, Katz JT, et al. Effect of reducing interns’ work hours on serious medical errors in intensive care units. N Engl J Med. 2004 Oct 28;351(18):1838–48. 

15.       Pronovost PJ, Goeschel CA, Colantuoni E, Watson S, Lubomski LH, Berenholtz SM, et al. Sustaining reductions in catheter related bloodstream infections in Michigan intensive care units: observational study. BMJ. 2010 Feb 4;340:c309. 

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