Association Between Body Size and Response to Hydromorphone in ED

Pain is the most common complaint for patients presenting to the emergency department (ED). Inadequate pain relief is also a common problem in ED. Patients' pain perceptions and responses to intravenous opioids vary widely and are influenced by multiple factors. The objective of the current study is to examine the association between total body weight, BMI (body mass index) and clinical response to a fixed dose of intravenous hydromorphone.

Pain is the most common complaint for patients presenting to the emergency department (ED). Morphine and hydromorphone are the two most commonly administrated intravenous opioid analgesics. However, a large inter-individual variation in the response to morphine or hydromorphone has been observed and a significant number of patients do not have satisfactory pain relief after receiving commonly administered doses of these two medications. Current studies have focused on investigating optimal strategies of intravenous opioid use for moderate and severe pain in the ED.

Contrary to the commonly recommended total body weight (TBW) based dosing strategy, a recent publication did not demonstrate a linear relationship between TBW and clinical response to morphine.

The ultimate goal of the research is to identify optimal methods of dosing opioids to alleviate pain in ED patients. The objective of this study is to examine the association between two measures of body size/body composition and response to a standard dose of hydromorphone. The null hypothesis is that there is no association between the measures of body size/composition and response to 1 mg hydromorphone, and thus no difference between the associations. If a strong association exists between TBW or BMI and pain response, it will lend support for the importance of taking body size or composition into account when making decisions about hydromorphone dosing in the ED. It will lay the groundwork for future studies of analgesic dosing. This is of particular importance given the increasing prevalence of obesity in the US and other developed nations.

Specific Aims:

1. To test the association between analgesic response to a standard dose of hydromorphone and total body weight in ED patients with acute pain requiring intravenous opioid analgesia.
2. To test the association between analgesic response to a standard dose of hydromorphone and BMI.
3. To compare the associations between analgesic response to a standard dose of hydromorphone and the two measures of body size/composition, BMI and TBW.
4. To assess whether the associations between response to hydromorphone and these measures of body size/composition are confounded or modified by gender, age, ethnicity and certain genetic polymorphisms.

The results of the current study will suggest whether body size or composition play a role in the clinical response to hydromorphone and may lay the groundwork for further studies to determine whether dosing should be modified to take these characteristics into account either continuously, e.g. 0.015 mg/kg hydromorphone or categorically (increasing doses by category of BMI).

Eligibility Criteria:
Inclusion Criteria:

* English or Spanish speaking
* Age 18 - 65 years old
* Acute pain (less than 7 days in duration)
* Pain with sufficient severity to warrant use of intravenous opioids in the judgment of ED attending physician

Exclusion Criteria:

* Allergy to hydromorphone
* Systolic blood pressure \< 90 mm Hg
* Room air oxygen saturation by pulse oximetry \< 95% at baseline without supplemental oxygen
* Alcohol or other drug intoxication as judged by the attending physician
* Suspicion of drug seeking by ED physician
* Use of opioids within the past 24 hours
* Use of a monoamine oxidase inhibitor
* Concurrent use of benzodiazepines
* Presence of a chronic pain syndrome (such as sickle cell disease, peripheral neuropathy, diabetic neuropathy, or fibromyalgia)
* History of COPD, sleep apnea, renal failure, liver disease
* Pregnancy or breast feeding
* Prior entry of patient in the study
* Inability or unwillingness to provide informed consent