Hazard [Health Devices May-Jun 1996;25(5-6):214-5]

Problem

ECRI investigated a case of suspected gas embolism associated with carbon dioxide (CO₂) insufflation. During a hysteroscopy (performed with the patient under intravenous sedation), the patient gasped for air almost immediately upon uterine insufflation. Also, heart sounds suggesting intracardiac gas were heard. The procedure was halted, and the patient recovered without further complication.

Based on the clinical signs, the medical staff suspected that the patient's condition was caused by a CO₂ embolism that originated in the uterus. However, our investigation revealed that the embolized gas was probably air—not CO₂. The air may have been introduced into the patient from the dead space in the tubing set used to connect the insufflator to the hysteroscope. This tubing set was not purged before insufflation began.

Symptomatic gas embolism can occur when undissolved gas (e.g., air, CO₂) accumulates in the heart and/or pulmonary arteries. This gas can compromise the circulation of blood through the lungs, causing serious injury or death.

Gas embolism is of particular concern when using insufflators because these devices introduce gas into the body at pressures that can exceed vascular pressure. For example, during hysteroscopic insufflation, insufflators designed to deliver gas at pressures up to 150 mm Hg (a pressure of 100 mm Hg is usually sufficient to distend the uterus for hysteroscopic observation) and flow rates up to 100 mL/min are typically used. If open vessels (primarily veins) are pre-existing or caused by cervical dilation or distention of the uterus, the pressure can force gas into the uterine vessels, where the blood flow can eventually carry any undissolved gas to the heart.

To minimize the risks of undissolved gas traveling to the heart when insufflating various body cavities, a highly soluble gas—CO₂—is used in most cases. Using an animal model, Corson et al. (1988) examined the safety of using this gas as a uterine insufflant. CO₂ was infused at flow rates up to 90 mL/min directly into the femoral vein of several female sheep for prolonged periods. Although some hemodynamic changes occurred at the higher flows used, the sheep tolerated the direct continuous infusion of CO₂. This study showed that, because of the high solubility of this gas in blood (54 mL/dL), CO₂ bubbles entering from uterine vessels were sufficiently dissolved during transit from the pelvic region before reaching the heart. (For additional discussion of gynecologic gas embolism, see References.)

In the incident we investigated, symptomatic gas embolism resulting from CO₂ insufflation of the uterus seemed unlikely based on the findings described in Corson et al. (1988). Thus, we examined whether air could have caused the patient's gas embolism symptoms. Air is much less soluble than CO₂, and it is considered inappropriate as an insufflation gas for most procedures.

The reporting hospital informed us that insufflator flow was initiated only after the hysteroscope was connected to the insufflator and the scope was inserted in the patient's uterus. Thus, air present in the dead space in the tubing set used to connect the insufflator to the hysteroscope could have been introduced into the patient. Our tests revealed that the tubing used had a dead-space volume of 45 mL. Because only about 50 mL of gas had been delivered at the time the procedure was stopped, we determined that the uterus was most likely insufflated with air contained in the unpurged tubing set.

Another possibility, although less likely, is that the air embolism was passively introduced. ECRI has received two reports of passive air embolism during insertion of hysteroscopic instrumentation. In these cases, the placement of the patients in the Trendelenburg position was a contributing factor. When the patient is tilted so that her pelvis is raised higher than her heart, the blood pressure in the pelvic veins may fall below atmospheric pressure and permit air to move into those veins. Thus, air embolism can occur during hysteroscopy even when the uterus has not been pressurized by an insufflator.

Regardless of the cause in the reported incident, the potential for inadvertent insufflation with dead-space air, possibly resulting in air embolism, certainly exists with hysteroscopic, as well as other, insufflators. For example, the use of Verres needles for peritoneal access and subsequent gas instillation in preparation for laparoscopy could permit infusion of gas directly into blood vessels if the needle tip is accidentally placed within a vessel.

1. Alert clinicians who set up and use CO₂ insufflators to the risk of inadvertent air insufflation caused by the failure to purge dead-space air from the insufflation system before insufflating the patient.
2. Placard insufflators as follows: Warning! Air embolism hazard. ( If the insufflator does not have sufficient space for the placard, consider placing this warning on the endoscopy cart.)
3. Immediately before delivering gas to the patient, purge air from tubing sets and instruments with CO₂. Allow 50 mL (cc) volume for each 6 ft (2 m) of 3/8 inch (10 mm) tubing.
4. When possible, avoid placing the patient in the Trendelenburg position for hysteroscopic examination.

Corson SL, Brooks PG, Soderstrom RM. Gynecologic endoscopic gas embolism. Fertility and Sterility 1996 Mar;65(3):529-33.

Corson SL, Hoffman JJ, Jackowski J, et al. Cardiopulmonary effects of direct venous CO₂ insufflation in ewes: A model for hysteroscopy. J Reprod Med 1988 May;33(5):440-4.

UMDNS Terms

• Insufflators, Hysteroscopic [16-848]
• Insufflators, Laparoscopic [16-849]

Device factor: Design/labeling error

User error: Incorrect clinical use

Support system failure: Failure to train and/or credential

Embolism (gaseous)