[Pre-existing pain as comorbidity in postoperative acute pain service]

Pre-existing or chronic pain is a relevant risk factor for severe postoperative pain. The prevalence of pre-existing and chronic pain in hospital depends on the time definition used and is approximately 44 % and 33%, at 3 or 6 months, respectively. The aim of this study was to determine the prevalence and importance of pre-existing pain in patients treated by a postoperative acute pain service (APS) and to evaluate the requirements for treatment and resources as well as its quality in this context.

This study involved an evaluation of all visits by the APS of the University Hospital in Göttingen over an 8-week period including patient subjective quality assessment on the basis of the quality improvement in postoperative pain therapy (QUIPS) questionnaire. Pre-existing pain (>12 weeks) was assessed by recording patients history of pain by members of the APS. The results from patients with and without pre-existing pain were compared.

A total of 128 patients (38% female, 62% male, aged 15-88 years old, mean age 59.8 ± 14.4 years) were seen by the APS on 633 occasions. Of these patients 91% had been admitted to hospital for surgery (66% for tumor surgery, 8% joint replacement, 9% other joint surgery and 16% other interventions), 50% had acute postoperative pain without pre-existing pain, 50% had had pre-existing pain for at least 12 weeks, 31% had chronic non-cancer pain and 19% pain possibly related to cancer. Patients with pre-existing pain showed no significant differences in the treatment requirements (e.g. adjustment of medication), use of resources (e.g. number of visits to the APS and time spent in hospital) and quality of care (e.g. pain intensity, functional aspects, side effects and complications) in the setting of the APS. However, there was an additional subsequent support by chronic pain and palliative care services.

Pre-existing pain is a common comorbidity in surgery patients treated by the APS. There were no significant differences in treatment requirements and quality of care between the patients. This is in contrast to other studies of postoperative pain management which showed that patients with pre-existing postoperative pain had higher pain intensity. This indicates indirectly that the presence of pre-existing pain should be further evaluated as a potentially useful indication for the support by an APS. However there is an urgent need for further studies to clarify whether this indirect effect can be replicated at other hospitals or in other patient collectives. Also it has to be clarified what benefits pain patients have from this kind of treatment: if they benefit from the APS in general or from the special technique, if there is a long-term effect lasting beyond treatment in the APS or if this group of patients would benefit in general from multiprofessional and non-invasive concepts of acute pain treatment.