Patient Safety Incidents and Nursing Workload 1

ABSTRACT Objective: to identify the relationship between the workload of the nursing team and the occurrence of patient safety incidents linked to nursing care in a public hospital in Chile. Method: quantitative, analytical, cross-sectional research through review of medical records. The estimation of workload in Intensive Care Units (ICUs) was performed using the Therapeutic Interventions Scoring System (TISS-28) and for the other services, we used the nurse/patient and nursing assistant/patient ratios. Descriptive univariate and multivariate analysis were performed. For the multivariate analysis we used principal component analysis and Pearson correlation. Results: 879 post-discharge clinical records and the workload of 85 nurses and 157 nursing assistants were analyzed. The overall incident rate was 71.1%. It was found a high positive correlation between variables workload (r = 0.9611 to r = 0.9919) and rate of falls (r = 0.8770). The medication error rates, mechanical containment incidents and self-removal of invasive devices were not correlated with the workload. Conclusions: the workload was high in all units except the intermediate care unit. Only the rate of falls was associated with the workload.


Introduction
In the past 15 years, the concern for patient safety has been a priority, motivating proposals of international health policies, and leading to joint efforts of institutions, health professionals and patients in order to reduce and effectively control the risks originated in the health services.
In Latin America, incidents of patient safety, defined as an event or circumstance that may have or effectively have caused unnecessary harm to patients, including incidents related to medication dispensing, falls, accidents with patients, medical equipment and infections associated with health care (1) , happen in 10% of hospitalized patients (2) . In Chile, studies have reported prevalence ranging between 6.2% and 15.7% of incidents (3)(4) .
The extensive line of research developed worldwide, has identified risk factors associated with patients and health organizations. In the latter are included those related to nursing work environments, such as: leadership, organizational structure of work, academic environment, burnout and workload of the nursing team, among others (5) .
In this area, studies have explored the association between the workload of the nursing team and the quality and safety of care given to the patient, showing an inverse relationship between the nurse/patients ratio and negative effects for patients and nurses.
Among the negative effects for patients: increases in the failure to rescue; increased incidence of urinary tract infection; pneumonia and upper gastrointestinal bleeding; patients' falls and increased mortality(6-8).
Furthermore, research has shown that insufficient nursing staffing cause job dissatisfaction, stress and intention of quitting the job (9)(10)(11) .
It is noteworthy that nursing workload is defined as a product of the average daily number of patients seen, adjusted by the degree of dependence and type of care, the average time of assistance for each patient, according to dependence and type of care delivered (12) . The instrument Therapeutic Intervention Scoring System (TISS-28) has been the most widely used and recognized worldwide tool for measuring nursing workload in the context of critical patients.
The measurement is performed by the procedures performed on the patient and as a result a single TISS-28 point corresponds to 10.6 minutes time of a nurse in direct care (13) .
Despite the relevance at an international level, nursing staffing levels differ widely between hospitals and inpatient units of the same specialty with the same level of dependence of patients (14)(15) .

Results
In the study were detected a total of 625 patient safety incidents with an average of 0.7 incidents per patient. Medication errors accounted for 89.56% (n = 558) of all incidents, followed by self-removal of invasive devices, 5.29% (n = 33), incidents related to containment 3.52% (n = 22) and finally falls representing 1.92% (n = 12).
The overall incident rate was 71.1%. The intermediate care unit had the highest rate with 129.8%, closely followed by the medicine ward with 128.8%. The lowest rates were recorded in oncology with 0%, followed by pediatric and medical-surgical private patients with 12.4% and 12.9% respectively ( Table 1).
The overall medication error rate obtained for the study sample was 0.9%. The highest rate was recorded in the pediatric ward with 1.5%, followed by medicine with 1.4% and the lowest in oncology with 0%.
The overall fall rate was 2.0 per 1,000 days of hospitalization. The service with higher rates of falls was medicine with 3.6 per 1,000 days of hospitalization, followed by medical and surgical institutional with 3      weekends. The workload of nursing assistants was also higher in medicine, surgery and surgical specialties. In these services the ratio nursing assistants/patients ranged from an auxiliary to 6.0 to 7.6 patients on the day shift and an auxiliary to 8.2 to 9.7 patients on the night shift.
These results indicate a higher ratio than stated in some international studies (6,18) ; however, we must consider that the workload estimation used in this study (exception made for the intensive care units) did not consider risk or degree of dependence of patients, a condition that should be taken into account when making comparisons.
The only patient safety incident that showed high correlation with the independent variables analyzed was the fall rate of patients. The high positive correlation observed between the workload of the services studied and the rate of falls, shows a scenario in which the amount of activities to be developed in a large number of patients probably exceeded the ability to respond to the care needs and patient monitoring, and this may explain the frequence of falls. Similar results were obtained by other authors, whose studies also correlated the high workload with inpatient falls (6,19) .
Oncology was the only service that did not recorded incidents of any kind; however, the workload was high in this service. The literature describes prevalence of falls between 15% and 17% (20) and medication error rate of 13.6% for these units (21) .
Psychiatry did not record falls, incidents associated with self-removal of invasive devices or incidents associated with mechanical restraint, despite having a high workload. Literature describes fall rates at 1.5 falls per 1000 days of hospitalization in psychiatric patients (22) and the occurrence of adverse events associated with mechanical restraint that can range from simple injuries to death (23) . Thus, the results obtained by these services could be explained by non-studied variables, or by the