Early Warning System Triggers In Intensive Care Unit After Receiving Intrathecal Morphine: A Retrospective Analysis

Author(s): J.R. Skelly and W.R. Jonker

Background: Neuraxial analgesia, including intrathecal morphine(ITM) administration, provides excellent analgesia in the post-abdominal surgery setting. As a corollary, such patients are commonly admitted to HDU/ICU for post-operative monitoring, and as such, bed availability can curtail its use. Reluctance to ward based postoperative care for this cohort is evident. Ward based postoperative care could benefit post-operative analgesic management.

Methods: We reviewed post-operative vital signs constituting the Irish National Early Warning System (INEWS), for general surgical patients admitted to our ICU after ITM administration, as would be undertaken at ward level. Data analysis for a period between January 2015 and August 2018. Inclusion criteria included: abdominal surgery; preoperative ITM and ICU admission post-operatively. Data for the initial 24 hours of ICU admission were obtained, including: AVPU score; respiratory rate(RR); fraction inspired oxygen(FiO2); arterial oxygen saturation(SpO2); heart rate(HR); systolic blood pressure(sBP). Additional measurements include recorded: ITM dose, age, weight, ASA grade, APACHE II Score, visual analogue pain scale scores, analgesic requirements.

Results: Thirty patients were included. The ITM dose was 548.3±28.2mcg(mean±SD). Mean maximum constituent INEWS Scores were: 1.7±0.2(RR); 1.5±0.2(SpO2); 1.6±0.3(AVPU); 1.1±0.2(HR); 2.0±0.2(sBP) giving a mean maximum total INEWS score of 4.9±0.3. Four subjects scored ≥7. No patient had INEWS de-escalated for supplemental oxygen and as such the addition of 3 NEWS points for oxygen supplementation would be applied to 96.7% (n=29) of patients.

Conclusion: The current study demonstrates that patients receiving these doses of ITM can exhibit high INEWS scores which would trigger escalation as outlined by the INEWS scoring system if located on a level 1 ward.