Israel Medical Association Journal

Background: Interpretation of blood gases is essential for the correct practice of medicine. Normal ranges for arterial blood gases (ABG) have not been extensively studied in the older population. Also, venous blood gases and venous-arterial pCO₂ gradient have not been studied in this population, even though they signify the majority of hospitalized patients.

Objectives: To determine the normal range for ABG and the bias limits of agreement for arterial-venous difference in the elderly population.

Methods: We recruited 130 elderly patients (> 70 years) and obtained blood gas measurements from venous and arterial blood. Patients were divided into four categories: healthy patients, patients with stable chronic pulmonary disease, hospitalized patients with acute respiratory illness, and hospitalized patients without respiratory disease. Samples were analyzed in a point of care analyzer.

Results: Mean PaCO₂ was 36.9 ± 4.2 mmHg for the healthy control group, 37.0 ± 4.8 mmHg in the stable chronic respiratory group, 37.0 ± 5.0 mmHg in the non-respiratory hospitalization group, and 42.3 ± 11.4 mmHg for the respiratory hospitalization group, Kruskall-Wallis, P <0.0025. Mean bias between venous and arterial CO₂ was +10.0 mmHg with 95% limits of agreement between 2.7 mmHg and -22.8 mmHg.

Conclusions: In elderly patients, the range of PaCO₂ measurements was similar to the accepted normal range in clinical practice. Venous-arterial PCO₂ gradient had high bias and wide limits of agreement, similar to previously published studies.

Background: Carbon dioxide is the most widely used gas to establish pneumoperitoneum during laparoscopic surgery. Gastrointestinal trauma may occur during the peritoneal insufflation or during the operative phase itself. Early diagnosis of these injuries is critical.

Objectives: To assess changes in end-tidal carbon dioxide (E_TCO₂) following gastric perforation during pneumoperitoneum in the rat.

Methods: Wistar rats were anesthetized, tracheotomized and mechanically ventilated with fixed minute volume. Each animal underwent a 1 cm abdominal longitudinal incision. A 0.3 x 0.3 cm cross-incision of the stomach was performed in the perforation group but not in the controls (n=10/group), and the abdomen was closed in both groups. After stabilization, CO₂-induced pneumoperitoneum was established at 0, 5, 8 and 12 mmHg for 20 min periods consecutively, each followed by complete pressure relief for 5 minutes.

Results: Ventilatory pressure increased in both groups when pneumoperitoneal pressure ≥ 5 mmHg was applied, but more so in the perforated stomach group (P = 0.003). E_TCO₂ increased in both groups during the experiment, but less so in the perforated group (P = 0.04). It then returned to near baseline values during pressure annulation in all perforated animals but only in the 0 and 5 mmHg periods in the controls.

Conclusions: When subjected to pneumoperitoneum, E_TCO₂ was lower in rats with a perforated stomach than in those with an intact stomach. An abrupt decrease in E_TCO₂ during laparoscopy may signal gastric perforation.