Cerebral Carbon Dioxide Embolism During Laparoscopic Cholecystectomy

Laparoscopic cholecystectomy has become the procedure of choice in the treatment of symptomatic cholecystolithiasis. Low morbidity and low incidence of serious complications have confirmed the advantages of laparoscopic surgery. The increasing popularity of minimal invasive techniques in gynecologic and general surgery is leading to a higher incidence of rare complications [1]. The major problems during laparoscopic surgery are related to the cardiopulmonary effects of gas insufflation, venous gas embolism, pneumoperitoneum, systemic carbon dioxide resorption, extraperitoneal gas insufflation, and unintentional injury to intraabdominal structures [2]. We describe a well documented case of venous embolism followed by cerebral arterial carbon dioxide embolism. Case Report A 58-yr-old woman was admitted to our hospital with a history and signs consistent with the diagnosis of a chronic calculous cholecystitis. Medical history and clinical examination revealed no relevant abnormal signs, with the exception of slightly increased liver enzymes. The patient was scheduled for laparoscopic cholecystectomy. After induction of anesthesia and tracheal intubation, controlled mechanical ventilation was initiated using a circle system with carbon dioxide absorber. Usual monitoring was used. For teaching purposes, a transcranial Doppler probe was used to monitor left medial cerebral artery blood flow. Because of a clinical Phase III investigating program, somatosensory evoked potentials of the median nerve were additionally monitored. Anesthesia was maintained with 50% oxygen and sevoflurane in air. Instillation of pneumoperitoneum was difficult and high pressures were noticed. Approximately 20 min after starting the operation, end-tidal carbon dioxide suddenly decreased from 29 to approximately 16 mm Hg. Disconnection from the ventilator was excluded and auscultation of the chest revealed no abnormality. Soon after this, systolic arterial pressure decreased to 65 mm Hg and heart rate increased from 65 to 96 bpm. Surgery was stopped and epinephrine 5 micro gram was given intravenously. Some minutes later, arterial blood pressure returned to baseline and the operation was continued. Still later, high-intensity transcranial signals were suddenly noticed in the transcranial ultrasound signal Figure 1. This sign of an arterial air embolism lasted for approximately 4 min. Simultaneously recorded somatosensory evoked potentials showed a significant reduction in amplitude. To prevent possible cerebral damage, corticosteroids and mannitol were given intravenously. The right radial artery was cannulated for blood gas analyses.Figure 1: Sonograms from the middle cerebral artery, obtained using a pulsed 2-Mhz ultrasound Doppler velocimeter (TC2-64 Transcranial Doppler; EME, Uberlingen, Germany). Time is displayed on the abscissae, frequency on the ordinates, and darkness of the trace is proportional to signal amplitude, with a dynamic range of 24 dB. A, Before skin incision, at end-tidal carbon dioxide tension 37 mm Hg. B, Numerous high-intensity cerebral signals, 15 min after circulatory depression caused by carbon dioxide embolism (arrows).Soon after the operation, the patient was tracheally extubated and transferred to the intensive care unit. Postoperative ultrasound examination of the patient demonstrated a possible small atrial septal defect at the superior septal wall Figure 2. Neurologic examination showed no signs of dysfunction. The patient was discharged from the intensive care unit the day after surgery.Figure 2: Postoperatively performed transesophageal ultrasound examination using a biplane 5-Mhz probe (77021A ultrasound system; Hewlett-Packard, Andover, MA) affording two- and four-chamber long-axis views of the heart, indicating a small atrial septal defect (arrow).Discussion Carbon dioxide embolism occurs most frequently in the initial phase of laparoscopic procedures. Intravascular gas insufflation after inadvertent puncture of intra- or extraabdominal blood vessels, accidental insertion of a trocar into the liver before laparoscopic cholecystectomy, and direct transuterine gas are causes of carbon dioxide embolism [3-5]. Because of the initially high pressures during initiating pneumoperitoneum, extraabdominal carbon dioxide insufflation was suspected and, indeed, was followed by carbon dioxide embolism. Clinical signs of gas embolism are determined by the volume of gas and its rate of entry into the blood circulation. A bolus gas embolism is followed by a massive decrease in cardiac output and right heart failure caused by "gas-lock" in the right atrium, whereas slow embolism with small bubbles, as seen in neurosurgery, may result in pulmonary hypertension by trapping in the pulmonary circulation [6]. This case showed that even cerebral embolism in case of an atrial septal defect, for example, or open foramen ovale (seen in 15%-20% of patients) may occur [7]. Also this case demonstrates that gas embolic complications can occur at any time during operation as a consequence of an open venous, or even arterial, vessel and a pressure gradient between a cavity and the circulatory system [6,8]. Minimal invasive surgery requires an increased duration of pneumoperitoneum and is associated with a higher degree of micro- and macrovascular injury, which may increase the risk of serious complications. The fast recovery of systemic circulation after minimal drug therapy indicates that the amount of gas embolism could not have been too large. Cerebral embolism without neurologic sequelae could be a result of the physical properties of carbon dioxide. This gas is highly soluble in blood, so that only large amounts of cerebral embolization might be harmful. In clinical practice, cerebral monitoring in laparoscopic surgery is not performed, so that the incidence of cerebral gas embolization might be higher than reported. Although serious complications associated with the use of CO2 gas are rare, the anesthesiologist should be aware of it. Modern monitoring methods, which provide the ability to detect gas embolism and a protocol for the emergency management, should be available to ensure a successful outcome.