Opioid use at admittance increases need for intrahospital specialized pain service: Evidence from a registry-based study in four Norwegian university hospitals

1 Introduction

Acute Pain Services (APS) were established in many countries during the 1990s [1]. Multi-modal analgesia was the leading concept with the aim of minimizing the side effects, reduce acute pain, and improve mobilization and recovery following surgery or acute illness [2,3]. This advancement was accompanied by implementation of new techniques like epidurals, peripheral local anesthetic blocks, and patient-controlled analgesia in both day surgery and surgical wards [4,5]. Multimodal analgesia is also a pivotal component of enhanced recovery after surgery [6].

This improved APS was well received, but it quickly became apparent that the individual need for analgesia varied significantly after identical surgery [7,8]. Moreover, painful trajectories were commonly observed across surgical and non-surgical wards, with considerable differences noted among individuals with similar conditions [9]. Recognizing this inter-individual variation in pain-trajectories, a new service emerged, commonly referred to as “transitional pain unit” (TPU) [10,11]. In these units, individuals at risk for poor trajectories are identified early and referred to the TPU either upon hospital admittance or upon identification of a poor trajectory [10]. These units serve to facilitate the transition from the operating room and wards back to normal life, while ensuring a safe tapering of opioids, particularly for risk patients [12].

Concurrently, persistent pain following surgery and medical diseases has been in focus, and it has been established that persistent pain is a major problem affecting a large proportion of hospitalized patients [13–15]. Important risk factors for persistent pain include previous opioid use, previous and ongoing pain conditions, and psychological distress [16,17]. The opioid use has received particular interest in light of the “opioid crisis” in the United States.

Despite documented benefits of TPU [11,12], gaps remain in understanding risk factors for prolonged opioid use and development of persistent pain. While clinical trials have stringent inclusion and exclusion criteria, registries include a broader spectrum of typical patients, providing additional insights on patients’ characteristics [18]. Hence, the Norwegian National Registry for Advanced Acute Pain Services [19] (AAPS), also known as SmerteReg, was established to improve knowledge and pain treatment further. This registry now collects comprehensive data from patients in several major hospitals in Norway.

Given the link between previous opioid use and adverse outcomes such as persistent pain, poorer recovery [20], and prolonged opioid use [21] shown in clinical trials, we aimed with this study to analyze opioid use patterns and characteristics of opioid users referred to AAPS, comparing them with non-opioid users in the registry-based population of SmerteReg.

2 Methods

3 Results

4 Discussion

In this registry-based study, we found that as much as 64% of the patients referred to AAPS used opioids at admittance. The opioid using patients were more frequently female and older compared to non-opioid using patients. Furthermore, the opioid using patients reported sleep problems before admittance three times more frequently than non-opioid using patients.

In this study, we report for the first time the characteristics of patients referred to reinforced APS registered in the Norwegian National Registry for AAPS (SmerteReg) [19], from four large university hospitals. The included patients were heterogenous regarding what diagnosis and what procedures they underwent during hospitalization, but they all shared being referred to the AAPS from the wards and experiencing particularly difficult pain where standard pain treatment was insufficient.

The impact of pre-admission opioid use has recently come into interest, and, to our knowledge, this is the first time it is reported that almost 2 of 3 patients (64%) referred to the AAPS were using an opioid at admittance. The precise number of opioid users at admittance among all hospitalized patients in the four hospitals encompassed is not known. However, most certainly, this number would be significantly lower than the observed 64% in the study population and we estimate it to be within the range of 10–20% of admitted patients. This estimation is based on findings from a recent investigation utilizing data from the Norwegian Prescription Database. Here, it was found that 9% of men and 12% of women had received an ambulatory prescription of an opioid during the last year [27]. Another study from Sweden found that 61,000 of 290,000 (21%) patients undergoing major surgery had received a prescription of an opioid at least once during 180 days prior to the surgery [28]. Thus, it may possibly be that patients using an opioid before and at admittance have a significant increased risk of not experiencing sufficient analgesic effect of standard care at the wards and therefore will need specialized acute pain care by AAPS.

Preoperative use of opioids has been shown to be a significant risk factor for extended opioid dependency and subsequent postoperative complications [29–31]. Our findings may confirm this association between prior opioid exposure and prolonged postoperative opioid usage. Our registry data show that all patients received opioid therapy throughout their hospitalization; however, the duration and extent of opioid utilization following discharge remain undisclosed for the examined period up to 2020. Starting in 2021, SmerteReg has integrated a patient questionnaire addressing opioid usage 4 weeks post-discharge, facilitating further exploration of perioperative opioid use in forthcoming investigations.

It has previously been shown that women report more pain after surgery than men, also when the surgery is identical [8]. This is in line with the findings of the current study where women were referred to the AAPS slightly more frequently than men. Accordingly, there were significantly more women in the group using opioids when admitted to hospital compared to the group not using opioids at admittance. Sex differences between groups of opioid users and non-opioid users has previously been shown in the United States where prescriptions of opioids from 2015 to 2018 was more frequent among women than men, with an increasing difference in age [32]. Also, women in an American outpatient setting were more likely to be given opioid prescriptions than men [33]. There are similar findings in Norway, as mentioned above, showing that 9% of men and 12% of women had received an ambulatory prescription of an opioid during the last year [27].

Patients admitted while using opioids reported sleep problems prior to admittance three times more frequently than those not using opioids. While it is known that patients seeking help for opioid dependence disorders frequently report sleep problems, this study is, to our knowledge, the first to report such findings in a population of hospitalized patients referred to AAPS. It prompts speculation about whether these reported sleep problems were caused by opioid use itself or by other factors, such as sleep problems being an under-communicated reason for receiving outpatient opioids or a combination of factors. Interestingly, during their hospital stay, all patients in this study were treated with opioids, and both groups reported similar degrees of sleep problems after admission, suggesting that acute illness, pain level, or the opioids themselves may affect sleep. However, other factors, including being hospitalized, are also likely contributors to reported sleep problems [34].

5 Strengths and limitations

The study benefited from comprehensive data collection, utilizing SmerteReg data, which allowed for a broad spectrum of patient characteristics and treatment outcomes to be analyzed. By incorporating PROMs such as pain scores, anxiety, depression, and sleep problems, the study provided a holistic understanding of factors influencing opioid use and pain management.

The study had several limitations. The finding that unique patients with two or more tracks are overrepresented in the opioid using group could influence the described results. However, the main finding that opioid use at admittance is a predictor for needing specialized pain treatment still stands, since 55% of those with only one track are opioid users which are significantly higher than the general population. For the patients with two or more tracks this prediction is even stronger. Furthermore, when analyzing the data for the 670 patients with only one track, the results showed the same tendency as for the whole study population (1,068 tracks).

Furthermore, listwise deletion of patient tracks with missing values may have introduced bias, potentially affecting the generalizability of the results. Additionally, the study focused exclusively on data from Norwegian university hospitals, limiting the generalizability of findings to other healthcare settings or countries with different healthcare systems. The data collected were partly based on patients’ memory, which may be subject to recall bias or inaccuracies in documentation. Furthermore, the lack of long-term follow-up beyond the hospital stay limited the understanding of long-term effects and opioid-related risks post-discharge.

In this study, we analyzed anonymous, retrospective registry data. This implies that the complete electronic patient record data for each patient cannot be obtained. Thus, data concerning, e.g., specific opioid used, indication for APS admittance, or type of surgery the patients underwent is missing in the analysis. Not being able to include the exact type of opioid used as well as the specific cause of hospital admission and surgery, limits the interpretation of our data. We strongly suggest collecting detailed data on preoperative opioid use including drug, dose, administration, indication, and length of treatment for future studies. Such data may, at least partly, explain both immediate and long-term postoperative trajectory regarding pain and opioid use, and potentially the risk for persistent postsurgical pain.

6 Conclusions

This study sheds light on the characteristics of patients referred to reinforced APS, offering valuable insights into the prevalence of opioid use, demographic factors, and associated clinical implications. Notably, we observed a high prevalence of opioid use among patients referred to AAPS, with as much as 64% of patients using opioids at admittance. Sleep problems before admittance were associated with opioid use, suggesting the importance of addressing sleep disturbances in pain management protocols.