Vital signs and nurses' choices of titrated dosages of intravenous morphine for relieving pain following cardiac surgery

Postoperative pain, if unrelieved, will impede patients' recovery. A theoretical model of factors which influence nurses' choices of titrated dosages of intravenous (TV) morphine was constructed for this study. This study aimed to examine whether or not a patient's vital signs would influence nurses' choices of titrated dosages of IV morphine for relieving pain following cardiac surgery. A survey design with a vignette and questionnaire method was used to collect data. The vignette developed by McCaffery & Ferrell was modified and adapted for this study. It described the pain reports and vital signs of two patients on postoperative day 1 following cardiac surgery. Convenience sampling was used to seek voluntary participation from 29 registered nurses working in the cardio-thoracic intensive care unit of a private hospital in Sydney, Australia. A protocol of the unit allowed nurses to titrate IV morphine against the pain of patients following cardiac surgery. The results showed that the pain assessment of the two patients in the vignette documented by the nurses were not consistent. The titrated dosages (a bolus dosage and a maintenance dosage) chosen by the nurses for the patient with slightly elevated vital signs differed significantly from the titrated dosages chosen by the same group of nurses for another patient with vital signs at the lower end of the stable range (t = 3.33, d.f. = 25, P < 0.01 for a bolus dosage and t = 3.73, d.f. = 25, P < 0.01 for a maintenance dosage). Different risk factors were stated by the nurses in titrating the bolus and maintenance dosages of IV morphine. The importance of accepting patients' verbal reports of pain as well as the provision of optimal dosages of TV morphine for pain relief is highlighted. A disadvantage of using a vignette and questions method is that the patients' clinical status is somewhat unreal. Further studies, however, were also recommended.