Hypoxaemia during recovery after surgery for colorectal cancer: a prospective observational study

Abstract

Episodic and ongoing hypoxaemia are well-described after surgery, but, to date, no studies have investigated the occurrence of episodic hypoxaemia following minimally-invasive colorectal surgery performed in an enhanced recovery setting. We aimed to describe the occurrence of postoperative hypoxaemia after minimally-invasive surgery in an enhanced recovery setting, and the association with morphine use, incision site, fluid intake and troponin increase. We performed a prospective observational study of 85 patients undergoing minimally-invasive surgery for colorectal cancer between 25 August 2016 and 17 August 2017. We applied a pulse oximeter with a measurement rate of 1 Hz immediately after surgery either until discharge or until two days after surgery, and recorded the oxygen saturation. We measured troponin I during the first four days after surgery, or until discharge. The median (IQR [range]) length of stay was 3 (2-4 [1-38]) days. Thirty-six percent of patients spent more than 1 h below an oxygen saturation of 90% (4.2% of the day), and with a median (IQR [range]) proportion of 1.3 (0.2-11.1 [0.0-21.4])% of the day spent with an oxygen saturation below 88%. We found no associations between time spent below an oxygen saturation of 88% and morphine use (p = 0.215), fluid intake (p = 0.446), complications (p = 0.808) or extraction site (p = 0.623). Postoperative increases in troponin I were associated both with time spent below an oxygen saturation of 88% (p = 0.026) and hypopnoea episodes (p = 0.003). Even with minimally-invasive surgery and enhanced recovery after surgery, episodic hypoxaemia and hypopnoea episodes are common, but are not associated with morphine use, fluid intake or incision site. Further studies should investigate the relationship between hypoxaemia and troponin increase.

Noninvasive respiratory support in the hypoxaemic peri-operative/periprocedural patient: a joint ESA/ESICM guideline

“…Hypoxaemia is a potential life-threatening yet common complication after surgery. In observational studies, hypoxaemia was reported in 21-55% of patients during the initial 48 postoperative hours [1,2], and was reported even after mini-invasive surgery [3]. Routine use of supplemental oxygen does not prevent hypoxaemic episodes [2].…”

The clinical implication of the association between hypoxaemia and postoperative troponin I

“…The study reported that there were 11 (13.0%) and 4 (4.7%) patients with a troponin I concentration of more than 15 ng.l −1 and 45 ng.l −1 , respectively. The authors also mentioned a cut‐off level of 45 ng.l −1 for ischaemia, therefore, the significance of an elevated level less than 45 ng.l −1 appears questionable.…”

“…Bojesen et al. recently demonstrated significant associations between postoperative increases in troponin I and the time patients spent with an oxygen saturation of 88% or below, and hypopnoea episodes. However, there appeared to be no correlation between the time patients spent with an oxygen saturation below 88% and morphine use, fluid intake, complications or incision site in 85 patients undergoing minimally invasive surgery for colorectal cancers in an enhanced recovery setting.…”

“…Therefore, the reported values may not be referenced to other hospital systems. In addition, of all 85 patients studied , myocardial ischaemia was diagnosed in only one patient who appeared to spend a relatively short time with an oxygen saturation of below 88% (52 s within the first 24 h after surgery) and had relatively few hypopnoea episodes (0.14 episodes.h −1 .night −2 ) and there was no information on their troponin I concentration. Because the clinical significance of the study was mainly to highlight the impact of postoperative hypoxaemia on the risk of acute ischaemic conditions (e.g.…”

The clinical implication of the association between hypoxaemia and postoperative troponin I: a reply

“…We thank Sun et al. for their interest in our paper regarding postoperative hypoxaemia after minimally invasive colorectal cancer surgery . They raise several clinically important questions; whether using an increase in troponin level below the cut‐off of ischaemia is questionable; the appropriate precautions to take to prevent hypoxaemia and steps to take when encountering elevated troponin levels; the association between complications and hypoxaemia; and the association of hypoxaemia with haemoglobin levels, blood loss and obesity.…”