Setting
The study was done at the Oslo Accident and Emergency Outpatient Clinic (OAEOC) in Oslo, Norway. The OAEOC is a primary care emergency outpatient clinic, serving the entire city at all hours. There are about 200,000 consultations a year. The majority of patients treated for acute poisoning by substances of abuse in Oslo, are treated at the OAEOC [
20]. These patients are assessed according to a systematic observation procedure, and the median observation time is four hours [
19]. Oslo is the capital city of Norway (population 613,285 as per 1 January 2012 [
21]).
Inclusion
We included all patients 12 years and older treated at the OAEOC for an acute poisoning by substances of abuse. Patients were included by the doctor treating them. Substances of abuse were defined as any potential substance of abuse including alcohol, prescription drugs, illegal drugs, and others. Patients were included consecutively during one year, from 1 October 2011 to 30 September 2012. Patients treated for multiple conditions were included if the poisoning in itself caused need for treatment or observation. Among 2733 eligible cases, 174 did not have a Norwegian national identity number and were excluded. In 216 cases the patient declined to participate. In the end, 2343 cases in 1731 patients were included.
Data collection and classification
For all included cases, a registration form was completed by the doctor treating the patient. Any information missing in the form was collected, if available, from the electronic medical records. Information on deaths from 1 October 2011 to 31 December 2012 was retrieved from the National Cause of Death Register, using the patients’ unique Norwegian national identity number.
For each case, we registered age, gender, main toxic agent, homelessness, suicidal intention, previous history of severe mental illness, time of presentation, time of discharge, and whether the patient self-discharged during treatment. Diagnoses of main toxic agents were made by the doctor treating the patient. Main toxic agent was defined as the agent assessed to be most toxic among the agents taken, assumed doses considered. The diagnoses were based on all information available then and there. Subsequently, main toxic agents were grouped by us as ethanol, opioids, stimulants, gamma-hydroxybutyrate (GHB), benzodiazepines, and others. Suicidal intention was registered according to the assessment of the doctor treating the patient. Previous history of severe mental illness was assessed and registered by the doctor treating the patient based on information from local medical records, from the patient and/or the patient’s companions. Severe mental illness encompassed psychosis, bipolar disorder and severe personality disorders. Homelessness was defined as being registered without a permanent address in the National Registry, which was accessed via the electronic medical records. Self-discharge was defined as leaving without being seen by a doctor, disappearing during treatment or leaving against medical advice. For patients disappearing during treatment, time of discharge was defined as the time when they were registered as missing from the clinic in the electronic medical records.
By using the patient’s unique Norwegian national identity number, we could identify patients presenting more than once during the inclusion period. The collected information was collated for each patient. Main toxic agent for a patient with more than one presentation was defined as the main toxic agent most frequently diagnosed in that patient’s poisoning episodes. In case of even frequencies, we used the toxic agent we considered most serious, in the following order: opioids, stimulants, GHB, benzodiazepines, ethanol, others.
Outcome measures
The main outcome measures were short-time mortality, defined as death during the inclusion period or the following three months; repeated poisoning once during the inclusion period; and repeated poisoning several times during the inclusion period. We looked for associations between self-discharge and these outcomes. Furthermore, we described characteristics of the self-discharging patients.