In intensive care units (ICUs), serum lactate and methemoglobin (metHb) levels are considered significant biomarkers for predicting mortality in critically ill patients. This study investigates the relationship between lactate and metHb levels in blood gas analyses at admission and 24 h later, as well as their association with mortality in ICU patients. The study was conducted retrospectively between March and December 2022 at Adıyaman Training and Research Hospital, evaluating 114 patients, with statistical analyses performed on the collected data. The results indicated a statistically significant decrease in lactate levels between admission and 24 h after (p = 0.004). However, no significant change was found in metHb levels (p > 0.05). Lactate clearance was significantly lower in deceased patients compared to survivors (p = 0.037), whereas metHb clearance showed no statistically significant association with mortality. Lactate is highlighted as a key indicator of tissue hypoxia and plays a critical role in managing critically ill patients. Elevated lactate levels are associated with impaired oxygenation and worse prognoses. The literature consistently supports the association between high lactate levels and increased mortality in conditions such as sepsis and hemorrhagic shock. Similarly, this study confirms the prognostic value of lactate, particularly in the early phases of ICU admission. In contrast, metHb levels were not found to significantly impact mortality. Although some studies suggest a potential role of metHb as a biomarker for oxidative stress in inflammatory diseases, this relationship was not supported by the current findings. In conclusion, serum lactate levels serve as a crucial tool for mortality prediction and patient management in ICUs, while metHb levels have limited prognostic value. These findings suggest that greater emphasis should be placed on lactate monitoring in the management of critically ill patients.

Appendix perforation is one of the many causes of secondary peritonitis. In this report, a case of peritonitis caused by Shigella sonnei in a 7-year-old child was presented. A 7-year-old male patient was presented with tenderness in the right lower quadrant and positive rebound tenderness test on physical examination. Abdominal ultrasonography and computed tomography revealed appendicular colitis and intraabdominal free fluid. The patient underwent surgery, during which perforation of appendix was noted. During the post-operative period, peritonitis developed. S. sonnei was isolated from peritoneal fluid secondary to perforation of appendix. Association of S. sonnei and appendicitis along with secondary peritonitis should be kept in mind when treating patients with abdominal pain and gastroenteritis. Key words: Appendicitis, peritonitis, Shigella sonnei.