Intravenous sodium bicarbonate verifies intravenous position of catheters in ventilated children

Background: Vascular access in children carries a significant risk of accidental extravasation of IV fluids and medications with the potential for tissue injury. In this prospective controlled study we assessed the diagnostic utility of using IV diluted sodium bicarbonate to confirm placement of IV catheters in ventilated children. Diluted sodium bicarbonate was created using undiluted standard 8.4% (1 mEq/mL) sodium bicarbonate mixed in a 1:3 and 1:5 ratio with sterile water to achieve a final diluted concentration of 2.1% (0. 25 mEq/mL) and 1.05% (0.125 mEq/mL) sodium bicarbonate, respectively. Methods: In 18 ASA I-II mechanically ventilated children ages 1 to 8 years, the effects of 1 mL/kg of dilute 2.1%, 1.05% sodium bicarbonate, or 0.9% normal saline, injected in a randomized order, were analyzed. All children had oxygen saturation, arterial blood pressure, electrocardiograph, and end-tidal carbon dioxide (ETCO₂) monitoring. In addition, venous blood samples were taken before injection and 10 minutes after the final injection for analysis of venous blood pH and electrolytes. Results: In children, IV diluted 2.1% sodium bicarbonate resulted in significantly increased ETCO₂ (mean of 32.8 ± 3.4 mm Hg to 39.0 ± 3.5 mm Hg, P < 0.001), a mean increase of 6.2 mm Hg (95% prediction interval: 4.3 to 8.1 mm Hg) within 3 breaths. Intravenous diluted 1.05% sodium bicarbonate caused a less pronounced but still significant increase in ETCO₂ (33.4 ± 3.8 mm Hg to 36.3 ± 3.4 mm Hg, P < 0.001), a mean increase of 2.9 mm Hg (95% prediction interval: 1.8 to 4.1 mm Hg) within 3 breaths. Normal saline did not result in any significant changes, with a mean increase of 0.06 mm Hg (95% prediction interval: -1.3 to 1.4 mm Hg). Both concentrations of sodium bicarbonate were easily differentiated from normal saline injection by blinded anesthesiologists observing the change in ETCO₂ values immediately after injection. Analysis of pre- and postinjection venous pH, bicarbonate, and sodium levels could not detect clinically significant changes. A small but statistically significant increase in venous bicarbonate was noted. Conclusion: The injection of 2.1% sodium bicarbonate in mechanically ventilated ASA I-II children identified intravascular placement and patency of an IV catheter by an increase in the exhaled CO₂ concentration. The injections did not have any clinically significant effects on blood pH, bicarbonate, or sodium concentration.