The Effects of Erector Spinae Plane Block and other anaesthetic techniques on Quality of Recovery and Prognostic Biomarkers in cancer and non-cancer patients undergoing major thoracic surgery

The goals of Anaesthesia have traditionally been described as the triad of hypnosis, analgesia and muscle relaxation. While these are still largely applicable today the speciality of anaesthesia has evolved and arguably, we could add 2 further goals: improving the Quality of Recovery of our patients and optimising anaesthetic technique to reduce the risk of cancer recurrence. First described in 2016, the Erector Spinae Plane Block (ESP) is a relatively new form of regional anaesthesia. Despite a lack of high quality evidence its use has become popular in patients undergoing a wide variety of surgeries in the thoracic region. This thesis aims to investigate the impact of ESP on quality of recovery in cancer and non- cancer patients undergoing major thoracic surgery. In practice ESP is rarely employed as the sole means of anaesthesia and is normally used as an adjunct alongside other anaesthetic techniques such as volatile anaesthesia or total intravenous anaesthesia (TIVA). Both volatile and TIVA have been shown to influence biomarkers associated with cancer recurrence in vitro and in vivo. This thesis also aims to examine the influence of anaesthetic technique on biomarkers of cancer recurrence in patients undergoing thoracic surgery. The ESP block demonstrated a statistically significant improvement in Quality of Recovery among patients undergoing both cancer and non- cancer thoracic surgery. Further, a reduced length of stay and lower incidence of post operative complications were also seen among patients who received an ESP block. We postulate that these results were due to the superior level of analgesia achieved as demonstrated by the smaller area under the curve of pain score versus time in the ESP group. Anaesthetic technique influenced the expression of Citrullinated H3 (Cit H3), a biomarker of Netosis in patients undergoing major cancer surgery. Netosis is the process by which Neutrophils release web like DNA structures, termed Neutrophil Extracellular Traps (Nets) from inside the cell. Nets and their associated proteins have been implicated in cancer recurrence. A combination of Propofol and Lidocaine demonstrated the greatest decrease in Cit H3 while also suppressing the biomarkers MMP-3 and MPO which are equally associated with cancer recurrence.
Overall, these results are clinically relevant for patients undergoing thoracic surgery for cancer and non- cancer operations. This thesis addresses important concepts in the disciplines of onco-anaesthesia and perioperative outcomes and provides a sound basis for further clinical trials to investigate the impact of anaesthetic technique on quality of recovery and cancer recurrence.