Intrathecal Morphine Usage in Hepatobiliary Surgery Dr David Cosgrave Dr Era Soukhin Dr Anand Puttapa Dr Niamh Conlon

Patient Cohort  Patients undergoing major open laparotomy  Almost all for hepatopancreaticobiliary procedure  ASA 1 – 3  71 patients with complete data on respiratory rate  Main aim to identify rate of complications  Aim to assess doses of intrathecal morphine administered

Data Gathered  76 patients  5 excluded due to incomplete data  71 remaining for analysis  Data collected from 7 Jan 2014 to 10 March 2015

Demographics  Age range 29 – 86 years old  ASA Scores  1/279% (56 patients)  321% (21 Patients)  No ASA 4/5 patients  Patients were predominantly in normal weight ranges  Mean weight 78kg  Minimum 43kg / Maximum 122kg

Types of surgery  Liver resection 58% (41 Patients)  Pancreatectomy 32% (23 patients)  Other 7%(5 patients)  Unknown 3%(2 patients)

Dose ranges for IT Opioid  Dose calculations are based on actual body weight  Dose calculation / recording with ITM is unreliable  Intrathecal Morphine  Mean dose 8mcg/kg  Minimum dose5mcg/kg  Maximum dose15mcg/kg  Intrathecal Fentanyl  No of patients 22 (of 71)  15 – 25mcg  No change in IT morphine if IT fentanyl administered

Non IT analgesia  Intravenous Analgesia  IV fentanyl almost exclusively used  Ketamine used as co-induction agent in some patients  Not analysed due to small numbers  Minimum dose 0mcg (? Recording Error)  Maximum dose 600mcg  Mean dose 355mcg  Abdominal Wall blocks  63 patients had adominal wall blocks performed preop  62 TAP + Rectus sheath blocks  1 TAP alone  61 Patients had wound catheter inserted by surgeons

Outcomes  Respiratory Depression…  Definition of respiratory depression???  SVUH acute pain service defines it as RR < 8  ASA Consensus Document - Respiratory rate < 10 – 12 or O2 sats < 90-92% ….

Respiratory depression  Respiratory rate < 8  Rate 14%  Respiratory rate < 10  Rate 25%  Adverse events related to respiratory depression?  0 Reintubations  2 patients (3%) required naloxone  No correlation with dose of IT morphine / IT fentanyl / IV fentanyl  No Correlation with dose of IV fentanyl  No correlation with age

Pruritus  Occurred in 17 Pts (24%)  1 patient missing data  16 of the 17 were treated with chlorpheniramine as per standard practice- ? Something to consider changing  1 with ondansetron  ?Possible correlation with IT Fentanyl administration  20% incidence of pruritus in No IT fentanyl group  32% incidence in IT fentanyl group  NOTE small numbers  ? Due to overall dose equivalent of opioid  ?Possible correlation with Total IV Fentanyl  Mean IV fentanyl in Pruritus group 373mcg vs 348 in no pruritus group

PONV  Occurred in 30 pts (42%)  19 patients required 1 agent  10 patients required 2 agents  1 patient required 3 agents  Despite 2 agent prophylaxis and relatively low opioid intraop  No correlation between intraop PONV prophylaxis and nausea incidence + number of agents required to treat  ? weak correlation with total IV fentanyl?  Mean IV fentanyl usage 338mcg in PONV group vs 375mcg in no PONV group

Rescue analgesia  No rescue analgesia required in 34 cases (46%)  In those requiring rescue analgesia fentanyl most commonly used  Mean dose 105mcg (over a period of 12 – 16 hours)  No difference between groups based on dose of IT morphine, IT fentanyl, IV fentanyl  No difference between groups dependent on abdominal wall blocks / wound catheters.  Note this audit only refers to the time until morning after surgery, which is within the duration of action of action of IT morphine, which was administered to all patients

Discussion  Dose of IT morphine based on actual body weight  Should dosing be based on ideal body weight  Should dosing be based on height to avoid another calculation  What is the ideal dose  Limited studies available mcg ITM Combined with PCA mcg ITM with bupivacaine / fentanyl reduces intratop opioid but not post op pain 3. ITM 500mcg with 15mcg IT fentanyl reduced pain post op 4. ITM mcg reduced pain and PCA consumption in the first postoperative day  Only one published dose finding study comparing doses of ITM in major laparotomy for cancer  1mg better than 0.2 or 0.5mg for analgesia in first 48 hours

Respiratory depression  Risk is real if patient’s are not adequately monitored  In our department no patient has required re-intubation in the last 2 years  Doses of 5-15mcg/kg are safe IF the patient is cared for in a HDU / PACU setting for the first post-operative night  The lack of a standardised definition of respiratory depression remains an issue

Other Adverse Events  Pruritus and PONV are very common  Standard management of pruritus in our centre could be improved  International evidence would suggest that antihistamines merely sedate these patients but don’t treat the pruritus  Naloxone or very small boluses of propofol have been shown effective in treating refractory nausea and vomitting in this population

The next step  RCT of intrathecal morphine at a standardised dose  Employing a preventative strategy for respiratory depression  Utilising new advanced monitoring for respiratory depression  Aim:  Potentially show a safe way for these patients to be transferred to ward level care  Potentially add to data on the definition of respiratory depression