title: A risk stratification algorithm using non-invasive respiratory volume monitoring to improve safety when using post-operative opioids in the PACU.
abstract: Late detection of respiratory depression in non-intubated patients compromises patient safety. SpO2is a lagging indicator of respiratory depression and EtCO2has proven to be unreliable in non-intubated patients. A decline in minute ventilation (MV) is the earliest sign of respiratory depression. A non-invasive respiratory volume monitor (RVM) that provides accurate, continuous MV measurements enables clinicians to predict and quantify respiratory compromise. For this observational study, practitioners were blinded to the RVM measurements and pain management followed the usual routine. Patients were stratified by their MV on PACU admission and classified as "At-Risk" or "Not-At-Risk," with progression to "Low MV" status following opioids assessed for each category. The purpose was to determine if stratifying based on MV on PACU arrival could identify patients at higher risk for respiratory depression. Ability to identify in advance patients at higher risk for respiratory depression following standard opioid dosing would drive changes in pain management and improve patient care. RVM and opioid administration data from 150 PACU patients following elective joint-replacement surgery were collected in an observational study. "Predicted" MV (MVPRED) and "Percent Predicted" (MVMEASURED/MVPRED× 100 %) were calculated for each patient using standard formulas. Prior to opioid administration, patients were classified as either "Not-At-Risk" (MV ≥ 80 % MVPRED) or "At-Risk" (MV < 80 % MVPRED). "Low MV" was defined as MV < 40 % MVPRED. Post-operative apnea (POA) was defined as ≥5 ten-second apneas per hour of PACU stay. We compared the incidences of Low MV following a single opioid dose, POA, and Low MV at discharge for both groups. In the PACU, 74/150 patients received opioids. Within 15 min of opioid administration, 32 % (24/74) developed Low MV. The risk-stratification algorithm identified 22/24 patients (92 % sensitivity). Only 46 % of them had POA, and the majority had Low MV without POA. At discharge, 29/150 patients had Low MV and those receiving opioids were 50 % more likely to display Low MV (23 vs. 16 %). The RVM can identify patients at-risk for opioid-induced respiratory depression and/or experiencing POA. Monitoring of MV can guide opioid-dosing regimens and may increase patient safety across the continuum of care.
authors.affiliation: John A. Burns School of Medicine, University of Hawaii, 1356 Lusitana Street, Room 606A, Honolulu, HI, 96813, USA. christopher.voscopoulos@gmail.com.
authors.forename: Christopher
authors.initials: C
authors.lastname: Voscopoulos
authors.affiliation: John A. Burns School of Medicine, University of Hawaii, 651 Ilalo St, Honolulu, HI, 96813, USA.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Theos
authors.affiliation: University of Texas Southwestern Medical School, 1801 Inwood Rd, Dallas, TX, 75235, USA.
authors.forename: H A
authors.initials: HA
authors.lastname: Tillmann Hein
authors.affiliation: Harvard Medical School, Massachusetts General Hospital, 55 Fruit Street, Boston, MA, 02114, USA.
authors.forename: Edward
authors.initials: E
authors.lastname: George
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000701:Analgesics, Opioid / Q000009:adverse effects* / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D009020:Morphine / Q000009:adverse effects / Q000627:therapeutic use; D010100:Oxygen / Q000737:chemistry; D010351:Patient Discharge; D061214:Patient Safety; D011182:Postoperative Care / Q000379:methods*; D011184:Postoperative Period; D015203:Reproducibility of Results; D012119:Respiration; D012131:Respiratory Insufficiency / Q000139:chemically induced*; D018570:Risk Assessment / Q000379:methods*; D055815:Young Adult
chemical_list: D000701:Analgesics, Opioid; D009020:Morphine; D010100:Oxygen
keywords: Minute ventilation; Opioids; Patient safety; Respiratory monitoring; Risk-stratification