Abstract
Opioids are respiratory depressants and heroin/opioid overdose is a major contributor to the excess mortality of heroin addicts. The individual and situational variability of respiratory depression caused by intravenous heroin is poorly understood. This study used advanced respiratory monitoring to follow the time course and severity of acute opioid-induced respiratory depression. 10 patients (9/10 with chronic airflow obstruction) undergoing supervised injectable opioid treatment for heroin addiction received their usual prescribed dose of injectable opioid (diamorphine or methadone) (IOT), and their usual prescribed dose of oral opioid (methadone or sustained release oral morphine) after 30 minutes. The main outcome measures were pulse oximetry (SpO2%), end-tidal CO2% (ETCO2%) and neural respiratory drive (NRD) (quantified using parasternal intercostal muscle electromyography). Significant respiratory depression was defined as absence of inspiratory airflow >10s, SpO2% < 90% for >10s and ETCO2% per breath >6.5%. Increases in ETCO2% indicated significant respiratory depression following IOT in 8/10 patients at 30 minutes. In contrast, SpO2% indicated significant respiratory depression in only 4/10 patients, with small absolute changes in SpO2% at 30 minutes. A decline in NRD from baseline to 30 minutes post IOT was also observed, but was not statistically significant. Baseline NRD and opioid-induced drop in SpO2% were inversely related. We conclude that significant acute respiratory depression is commonly induced by opioid drugs prescribed to treat opioid addiction. Hypoventilation is reliably detected by capnography, but not by SpO2% alone. Chronic suppression of NRD in the presence of underlying lung disease may be a risk factor for acute opioid-induced respiratory depression.
Highlights
Heroin/opiate overdose is a major cause of death amongst young adults
One participant had previously been diagnosed with chronic obstructive pulmonary disease (COPD) and had been prescribed inhaled short-acting beta-2-agonists
Oxygen desaturation was mostly periodic, but the average SpO2% was significantly lower at 15 minutes post injectable opioid (baseline SpO2 96.5 (95.1 to 99.2)% to 95.3 (90.9 to 98.4)% at 15 minutes, p = 0.03)
Summary
Heroin/opiate overdose is a major cause of death amongst young adults. As the World Health Organization [1] observes: “Opioids are potent respiratory depressants, and overdose is a leading cause of death among people who use them. An estimated 69,000 people die from opioid overdose each year.”. Opiates loom large in statistics on drug-related deaths. With the recent establishment of supervised injectable heroin maintenance clinics (see description in Lancet 2010 [7] and recent meta-analysis [8]), an opportunity exists to study physiological responses to intravenous and intramuscular administration of extremely high dose diamorphine (e.g. 50–200mg) in a clinical context, but with the addition of comprehensive monitoring of acute changes in respiratory function
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