Opioid intoxication and overdose: Clinical sciences

Opioid intoxication and overdose are terms used to describe the physiological and psychological changes that result from an excessive dose of opioids. Now, opioids include heroin and powerful pain relievers like morphine, fentanyl, and oxycodone. Opioids can be taken through multiple routes, including ingestion, inhalation, intravenous injection, as well as by transdermal patch.

Once in the body, they bind to major opioid receptors, which are found in organs such as the brain, heart, blood vessels, and gastrointestinal tract, causing effects such as euphoria or dysphoria; miosis, or constricted pupils; bradycardia and hypotension; and decreased bowel motility leading to constipation. Sometimes, opioid use can result in opioid overdose, which can lead to severe respiratory depression, significant sedation, coma, and even death.

Now, if you suspect opioid intoxication or overdose, you should first perform an ABCDE assessment to determine if your patient is unstable or stable.

If unstable, stabilize the airway, breathing, and circulation. Often, you might need to intubate, since unstable patients typically present with respiratory depression or apnea and require mechanical ventilation. Next, provide supplemental oxygen, obtain IV access, and, if needed, administer fluids for volume resuscitation. Finally, don’t forget to put your patient on continuous vital sign monitoring, such as heart rate, blood pressure, and oxygen saturation.

Next, obtain a focused history and physical examination, as well as point-of-care glucose at bedside. The history and physical are critical in these patients, so, if your patient is comatose or intubated, you should gather information from witnesses, friends, family members, or emergency personnel!

History might reveal opioid use or a previous diagnosis of substance use disorder. On the other hand, the physical exam typically shows signs of respiratory depression, such as severely decreased respiratory rate, apnea and shallow breathing; while oxygen saturation is usually below 90% due to severe respiratory depression; and some patients may also present with hypotension.

Next, these patients often have severely altered mental status. They are typically unconscious or they might even experience seizures. And, don’t forget to examine the patient’s eyes because a patient with opioid intoxication or overdose will have miotic, pinpoint pupils that do not respond to changes in light! Also, check bowel sounds, which are typically decreased, and look for evidence of substance use, such as needle marks.

Finally, get a point-of-care glucose measurement to rule out hypoglycemia, which can often mimic some symptoms of opioid overdose. Patients with opioid intoxication or overdose typically have normal glucose levels.

Now, here’s a clinical pearl to keep in mind! Labs are typically not needed to diagnose acute opioid intoxication or overdose. However, if you do order them, you might notice findings that support the diagnosis, such as elevated creatine phosphokinase, or CPK, from rhabdomyolysis due to immobility or hypoxia. Moreover, rhabdomyolysis can lead to acute kidney injury, and if this is the case, you might also see elevated BUN and creatinine levels. Additionally, it’s recommended to obtain a urine and blood toxicology screen in all patients that you suspect are having some type of overdose, as there could also be additional agents compounding the presentation. These tests should not delay treatment if suspicion is high.

All of these findings are highly suggestive of opioid overdose, so you should immediately administer intravenous naloxone.

This is a short-acting opioid antagonist that competes with opioids at the opioid receptors, and naloxone's binding affinity is highest to the mu opioid receptors specifically. Administer naloxone slowly every 2 to 3 minutes and assess the patient’s response. Continue naloxone until the patient is awake and has a spontaneous respiratory rate of at least 12 or more breaths per minute.

If the maximal dose of naloxone does not cause any improvement, then consider an alternate diagnosis. On the flip side, if your patient’s respiratory function is improving, you can make the diagnosis of opioid overdose. Keep in mind that your patient will start breathing spontaneously before they become fully alert!