This retrospective analytic survey was conducted at K S Hegde Hospital, Deralakatte, Mangalore; from June 2015 to June 2017. After obtaining Ethical Committee Approval (INST.EC/EC/107/2017-2018), a analysis of the medical records of all patients over 18 years of age who underwent coronary artery bypass grafting was performed. The data was divided into two groups: SCM group and PCT group depending on the primary analgesia the patient received. As per the hospital protocol, SCM (0.1 mg/kg) is administered via indwelling 22G IV cannula inserted in subcutaneous plane of left forearm.

Inclusion criteria: Patients belonging to ASA PS I, II and III, patients above 18 years of age and those posted for coronary artery bypass grafting were included in the study.

Exclusion criteria: Patients with incomplete or illegible medical records and those with intraoperative complications (requiring intra-arterial balloon pump postoperatively) were excluded from the study.

The following perioperative data were extracted from the medical record: demographic data and anaesthesia. The following postoperative pain related data were extracted from the medical records: (i) Dose of additional analgesia(IV fentanyl/ IV tramadol) over 24 h, (ii) Hemodynamic parameters at 0, 6, 12 and 24 h, (iii) Side effects such as nausea, vomiting, pruritis, and respiratory depression (Oxygen saturation <90%). The additional data included: Duration of CICU stay.

The normality of data was first examined by the Shapiro Wilk’s test. The two groups were compared using Student’s t-test for normally distributed continuous data or non-parametric test if the data were not normally distributed. Categorical data were compared by Fisher’s-exact test. The p-values <0.05 were considered statistically significant.

There was no statistically significant difference in the demographic profile and haemodynamic variables of the two groups [Table/Fig-1]. It was observed that SCM group required less additional fentanyl and less additional tramadol compared to PCT group which was statistically significant with p-value of <0.001 [Table/Fig-2]. It was also noted that there was a statistically significant side effects observed in PCT group compared to that of SCM group with p-value of <0.001 [Table/Fig-2]. Additional parameter noted was duration of CICU stay which was longer in group PCT compared to SCM group with a p-value of 0.001 [Table/Fig-3].

This study was conducted to note if intermittent SCM was helpful in postoperative pain management following CABG. The comparison of demographic and haemodynamic variables revealed no significant differences between the two groups. It was found that requirement of additional analgesia was less in SCM group with lesser side effects and shorter duration of CICU stay compared to that of PCT group and these differences were statistically significant with p-value of <0.001.

A recent review on the efficacy of different modes of analgesia in postoperative pain management and early mobilisation in postoperative cardiac surgical patients concluded that the use of PCA with opioids in conjunction with local subcutaneous anaesthetic continuous infusions is effective for longer duration and this approach has scope of becoming the cornerstone for pain management post-cardiac surgery in ICUs [4].

Similar results were observed by Machida M et al., [5]. As they concluded that continuous SCM group required less analgesia and had fewer side effects with improved patient satisfaction. Another study [6] compared effects of continuous SCM, continuous Epidural Morphine, and Diclofenac Sodium as pre-emptive analgesia for postoperative pain; concluded that continuous SCM is an attractive method for postoperative analgesia with technical ease, brought some analgesic effects with a low rate of complications.

The studies evaluating the use of SCM as postoperative analgesia following cardiac and non-cardiac surgeries concluded that SCM is a safer alternative with minimal complications [7-9].

The subcutaneous injection is not the preferred route of administration in patients with hypotension postoperatively as this reduces the subcutaneous perfusion there by affecting the drug absorption.

As there is limited data available in literature regarding postoperative uses of SCM, this demands further studies to understand its scope as postoperative analgesia as well as preemptive analgesia. However, this study helps in clarifying another clinically relevant research question, of comparing SCM with intravenous analgesia. Intermittent SCM can be effectively administered for postoperative analgesia following CABG with similar haemodynamic stability and minimal side effects and shorter duration of CICU stay as compared to intermittent intravenous analgesia.