Objectives: Irvine, Sidani, and McGillis Hall (1998) developed the Nursing Role Effectiveness model to guide the assessment of nurses' contribution to health care. It conceptualizes the contribution nurses make to health care in terms of three primary roles; nurses' independent role, interdependent role, and medical-care related role. The purpose of this study was to empirically test the propositions in the nursing role effectiveness model by examining the impact of nurse staff mix on nurses' interdependent role, and patient outcomes. Nurses' interdependent role is defined as the role functions and activities that nurses share with other health care professionals that contribute to the continuity of patient care and care coordination. The specific objectives of this study were to examine the effect of nurse staff mix on the quality of nurses' communication and care coordination, and the effect of these interdependent role activities on patients' functional health outcomes.
Design: A repeated-measures design was employed to collect data on patient outcomes at hospital admission and within 3 to 5 days, which coincided with hospital discharge.
Population, Sample, Setting, Years: The setting for the study were seventeen tertiary care teaching hospitals in Ontario. The population was adult patients hospitalized with a case mix group classification of pneumonia, chronic obstructive pulmonary disease, colorectal surgery, or major gynecological surgery. Data were collected from a sample of 835 medical and surgical patients, 1085 nurses, and 74 nurse managers. Data collection occurred in 1999-2000.
Variables: The structural variables of interest included the proportion of registered nurse (RN) staffing relative to registered practical nurses (RPNs) and unregulated workers, and the RN/patient ratio. Nurses' interdependent role performance was operationally defined as the quality of communication among nurses and between nurses and other health care professionals, and the effectiveness of care coordination. Patients' functional status was operationally defined as patients' ability to engage in activities of daily living/ self-care.
Methods: Patient's functional status was assessed at admission and within 3 to 5 days by a trained nurse, using the Functional Independence Measure. Cronbach's alpha was 0.87 and 0.88 respectively. Nurses assessed the quality of communication and care coordination using an instrument developed by Shortell and colleagues. Communication was measured along three dimensions reflecting the accuracy, timeliness, and satisfaction with communications. The three dimensions were summed to yield a composite score, with a Cronbach's alpha coefficient of 0.86. The coordination variable consisted of two dimensions; formal means to coordinate care such as the use of care maps (Cronbach's alpha 0.83) and informal coordinating activities, such as team meetings and patient rounds (Cronbach's alpha 0.81). A questionnaire was used to collect data from nurse managers about the nurse-patient ratio and proportion of RN staffing. Structural equation modeling was used to test the hypothesized relationships among the nursing structural variables, nurses' role performance, and patients' functional health outcomes. Patients' capacity for good outcomes was controlled for by including age, gender, medical complexity, and length of stay in the structural model.
Findings: Nurse communication was more effective on units with higher proportions of RN staffing and with lower RN-patient ratios. Formal care coordination was more effective on units with higher proportions of RN staffing. Informal coordination was positively related to high nurse-patient ratios. The three role performance variables were interrelated. Communication was positively related to informal coordination activities but negatively related to formal coordination. Patients achieved higher functional health outcomes on units where nurse communication and informal coordination were effective. Patients' functional health outcome was negatively related to formal care coordination.
Conclusions: The study results offer further validation for the propositions in the nursing role effectiveness model. The proportion of RN staffing and nurse-patient ratio affected the quality of nurses' interdependent role performance, which in turn, affected patients' functional health outcomes at the time of hospital discharge. The role performance variables fully mediated the effect of staffing on patient outcome. A higher mix of professional nurses promoted effective communication among nurses, which had a beneficial effect on the outcomes of care for specific types of medical and surgical patients. The results concerning the coordinating activities of nurses were mixed. Effective informal coordination promoted better patient functional health outcomes whereas formal coordination activities seemed to have a detrimental effect on patient outcomes. Further work is needed to explicate and measure the coordinating functions of nurses.
Implications: The study findings support the conceptualizing of nurses' interdependent role performance as a mediator in the causal relationship between nurse staffing and patient outcomes and as such, advance our understanding of how variables such as nurse staffing affect patient outcome achievement.
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