This study summarized the short- and mid-term outcomes of 20 patients with NOMI who underwent emergency surgery; we found that 50% patients did not survive. Low HCO3- and high lactate levels may be preoperative risk factors for mortality. Six of these patients died in the early postoperative period within 30 days after surgery because of septic shock; however, the remaining four patients died because of septic shock or were unable to continue HD despite surviving the acute postoperative period. These results suggest that patients on HD, even if they avoid early postoperative death, have a high risk of postoperative mortality because they are unable to continue HD. The indications for surgery in patients with these risk factors should be carefully evaluated.
The concept of NOMI includes acute mesenteric ischemia (AMI), occlusive mesenteric arterial ischemia (OMI), and mesenteric venous thrombosis (MVT) [11]; NOMI was found to occur in 20–30% AMI cases in previous reports [5, 12]. According to previous reports, physiological findings of NOMI include elevations in aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine phosphorus kinase (CPK), and lactate dehydrogenase (LDH), as well as lactic acidosis and metabolic acidosis without an elevated inflammatory response [13]; however, these indicate a generalized poor general condition of the patient and lack of specific clinical physiological findings. Although the pathogenic mechanism of NOMI has not been elucidated, it is believed to be caused by endogenous vasopressin and angiotensin secreted to maintain the blood supply to vital organs when systemic perfusion is reduced due to heart failure, shock, or dehydration, resulting in decreased intestinal blood flow [14–16].
Several prognostic factors for NOMI have been reported. Kvarstein et al. reported a base excess decrease with increasing lactate and H⁺ in arterial blood gas analysis and discovered an increase in arteriovenous lactate in a major area of the gut and a decrease in arteriovenous lactate in skeletal muscle due to supply dependency [17]. In the present study, we observed a similar increase in lactate, reflecting intestinal ischemia, and a decrease in HCO3- due to associated metabolic acidosis. The mortality rate increased with the lactate level; this reflects extensive or irreversible ischemia of the intestinal tract and systemic ischemia involving other organs, which may be a high-risk factor for postoperative mortality. Recently, Suzuki et al. stated that the mean BP (< 68.2 mmHg) and base excess ( < − 4.95 mmol/dL) were poor prognostic factors [7]. In this study, a low mean BP was not found to be a significant risk factor for postoperative mortality because of the small sample size; however, a trend was observed.
Furthermore, we noted that patients with HD had postoperative mortality outcomes, especially after the acute postoperative phase. We divided the HD and non-HD patients and examined mortality based on whether the necrotic intestine was confined to the colon or colonized in the small bowel in HD patients and lactate levels in non-HD patients (Fig. 2). All five patients on HD who showed necrosis of the small intestine with or without the colon, rather than necrosis of the colon alone, had a fatal outcome, suggesting that the distribution of the necrotic intestine (i.e., when the necrosis extends into the small intestine) is a prognostic factor in patients on HD. In non-HD patients, when 6.5 mmol/L was used as the cut-off for lactate, four and nine patients showed lactate levels of > 6.5 mmol/L and < 6.5 mmol/L, respectively. All patients with lactate > 6.5 mmol/L had a mortality outcome, while all those with lactate < 6.5 mmol/L were discharged alive.
This study has several limitations. First, it was a single-center retrospective study with a small number of cases. Therefore, a few biases and confounding factors could not be eliminated, and the statistical power was insufficient. Second, only surgical cases were collected; thus, cases where surgery was not performed after diagnosis were not included, resulting in underestimation of mortality. Third, patients treated with drugs such as intravenous papaverine hydrochloride without any surgery were not analyzed.