I could get some articles on this topic.You may examine the instruments used in them.
Sir MY, Dundar B, Barker Steege LM, Pasupathy KS. Nurse-patient assignment models considering patient acuity metrics and nurses' perceived workload. J Biomed Inform. 2015 Jun;55:237-48. doi: 10.1016/j.jbi.2015.04.005
Alam S, de Oliveira Cruz V, Zapata T. Assessment of staffing needs for physicians and nurses at Upazila health complexes in Bangladesh using WHO workload indicators of staffing need (WISN) method. BMJ Open. 2020 Feb 13;10(2):e035183. doi: 10.1136/bmjopen-2019-035183
Barrios S, Catoni MI, Arechabala MC, Palma E, Ibacache Y, Richard J. Carga laboral de las enfermeras en Unidades de Hemodiálisis Crónica según dependencia y riesgo de los pacientes [Nurses' workload in hemodialysis units]. Rev Med Chil. 2017 Jul;145(7):888-895. Spanish. doi: 10.4067/s0034-98872017000700888
Neill D, Davis GC. Development of a Subjective Workload Assessment for Nurses: A Human Factors Approach. J Nurs Meas. 2015;23(3):452-73. doi: 10.1891/1061-3749.23.3.452
Sansoni J, De Caro W, Marucci AR, Sorrentino M, Mayner L, Lancia L. Nurses' Job satisfaction: an Italian study. Ann Ig. 2016 Jan-Feb;28(1):58-69. doi: 10.7416/ai.2016.2085.
besides the research already mentioned by Bhogaraju Anand and Dhani Shanker Chaubey you might want to look at the burnout syndrome, which is closely related to (high) workload of nurses. Maybe, your research questions allow you to dig into this topic as well. There is a lot of research in Nursing journals, such as:
Article Burnout and its correlates among nursing staff: Questionnaire survey
Article Predicting nurse burnout from demands and resources in three...
Further, there is a scale measuring components of the burnout syndrome (called the Granada Burnout Questionnaire):
Article Psychometric properties and scales of the Granada Burnout Qu...
Here are some of them: - "Nursing Stress Scale" (NSS), by Gray-Toft and Anderson; - "Occupational Stress Questionnaire for Health Professionals", by Reig and Caruana.