Adverse Events Following Intrrathecal Drug Device Implementation
Introduction: Intrathecal drug delivery systems (IDDS) may be placed for treatment of intractable malignant and nonmalignant chronic pain. It can be utilized for patients receiving inadequate analgesia or experiencing limiting side effects with traditional drug delivery. Although intrathecal drug delivery systems have the benefit of decreasing untoward side effects of systemic opioids and improving patient's pain and functioning, they can be associated with other risks. Complications associated with implantation include surgical, pharmacological and physiological effects, with the key safety issue being respiratory depression. Previous literature found nine deaths associated with implantation or replacement of IDDS, proposed to be secondary to respiratory depression (Coffey 2009). Multiple expert panels have recommended hospital inpatient monitoring for minimum of 24 hours during initiation of IDDS therapy. ASA practice guidelines recommend monitoring adequacy of ventilation, oxygenation, and consciousness, with readily available opioid reversal (Prager 2013). This study retrospectively reviewed IDDS placements and revisions at a single tertiary medical center for adverse events during mandated hospital stay.
Materials and Methods: After IRB approval, records of 68 patients who underwent IDDS placement or revision with intrathecal regimens including opioids from 2010-2013 were reviewed. Summary of demographic and clinical characteristics of the study sample was performed for continuous variables as mean (standard deviation) or median (interquartile range) as appropriate, in the setting of skewed data and for categorical variables as frequency percentages. Adverse events including rapid response calls, codes, and ICU transfers were evaluated.
Results: Sixty-eight patients underwent IDDS placement or revision for pain, the majority for malignancy related pain (n=50; 73.5%). In all cases, Synchromed intrathecal pumps (Medtronic Inc., Minneapolis, MN, USA) were implanted. All patients were monitored for a minimum of 24 hours following implantation. No adverse events were detected secondary to opioid overdose or respiratory depression. Adverse events occurred in four patients (5.9%), all with malignancy. These events included cardiac events in two patients, respiratory event in one patient, and seizure in one patient. In all cases, transfer to an intensive care unit occurred promptly and appropriate treatment was provided.
Discussion: IDDS provide improved analgesia for refractory-pain, as well as patients intolerant of systemic side effects from parenteral or intravenous opioids. The implantation and introduction of intrathecal opioid propose a significant risk, including respiratory depression and opioid overdose. Although zero patients in our review demonstrated respiratory depression, adverse events were recorded in four patients' hospital stays. These are likely reflective of the significant comorbidities of these patients, including ongoing malignancy. Although our patient population may be high risk in the setting of malignancy compared to patients with non-malignant pain, a significant risk exists following placement of this device.
Adverse events following placement of IDDS are infrequent, yet vigilance remains key. Mitigation of these adverse events that are recognized early by hospital staff may be promptly managed to avoid significant morbidity and mortality. We recommend all patients receiving IDDS be monitored for at least 24 hours during initiation of opioid therapy to prevent significant adverse outcomes, in alignment with guidelines of current expert panels.