The relationship between end-expired carbon dioxide tension and severity of venous air embolism during sitting neurosurgical procedures – A contemporary analysis

A human cadaveric model for venous air embolism tool development

Purpose

A human cadaveric model combining standard lung protective mechanical ventilation and modified cardiac bypass techniques was developed to allow investigation into automated modes of detection of venous air emboli (VAE) prior to in vivo human or animal investigations.

Methods

In this study, in order to create an artificial cardiopulmonary circuit in a cadaver that could mimic VAE physiology, the direction of flow was reversed from conventional cardiac bypass. Saline was circulated in isolation through the heart and lungs as opposed to the peripheral organs by placing the venous cannula into the aorta and the arterial cannula into the inferior vena cava with selective ligation of other vessels.

Results

Mechanical ventilation and this reversed cardiac bypass scheme allowed preliminary detection of VAE independently but not in concert in our current simulation scheme due to pulmonary edema in the cadaver. A limited dissection approach was used initially followed by a radical exposure of the great vessels, and both proved feasible in terms of air signal detection. We used electrical impendence as a preliminary tool to validate detection in this cadaveric model however we theorize that it would work for echocardiographic, intravenous ultrasound or other novel modalities as well.

Conclusion

A cadaveric model allows monitoring technology development with reduced use of animal and conventional human testing.

Anesthetic Management of Patients Undergoing Open Suboccipital Surgery

The posterior cranial fossa with its complex anatomy houses key pathways regulating consciousness, autonomic functions, motor and sensory pathways, and cerebellar centers regulating balance and gait. The most common posterior fossa pathologies for which neurosurgical intervention may be necessary include cerebellopontine angle tumors, aneurysms, and metastatic lesions. The posterior cranial fossa can be accessed from variations of the supine, lateral, park-bench, prone, and sitting positions. Notable complications from positioning include venous air embolism, paradoxic air embolism, tension pneumocephalus, nerve injuries, quadriplegia, and macroglossia. An interdisciplinary approach with careful planning, discussion, and clinical management contributes to improved outcomes and reduced complications.

Perioperative Risk of the Sitting Position for Elective Posterior Cervical Spine Surgery: A Retrospective Case Series

BACKGROUND

The sitting cervical position for elective posterior cervical decompression and fusion affords advantages over prone positioning, but remains unpopular due to concerns about venous air embolism (VAE).

OBJECTIVE

To demonstrate the safety and efficacy of sitting cervical surgery in our series and in the literature.

METHODS

To evaluate the incidence of complications, we retrospectively identified all adult patients who underwent elective sitting posterior cervical surgeries at our institution from 2009 to 2014. Using International Classification of Diseases-9 coding, we searched for incidences of air embolism, myocardial infarction, pulmonary embolism, and deep vein thrombosis. Operative time, estimated blood loss, and case type distribution were also recorded. We then calculated the incidence of clinically significant VAE in sitting cervical surgeries.

RESULTS

Between 2009 and 2014, 558 surgeries were performed in the sitting cervical position. No VAE was identified. The average operative time was 1 h 25 min. A total of 30-d perioperative complications among sitting position patients included 3 myocardial infarctions, 1 pulmonary embolism attributed to venous thrombosis, and 2 patients with deep venous thrombosis for a total cardiovascular complication rate of 1.1%. The incidence of clinically significant VAE in the literature is 1.5%.

CONCLUSION

We present the second largest case series to date on the sitting position for cervical surgeries, highlighting its safety and efficacy. This position provides a surgical field with superior visualization, allowing decreased operative time and blood loss. The risk of clinically significant VAE is low. Intraoperative monitoring for these events with less invasive means is safe and effective.

Intraoperative venous air embolism in the non-cardiac surgery-the role of perioperative echocardiography in a case series report

Venous air embolism (VAE) is commonly one of the iatrogenic complications associated with divergent high-risk surgeries. In this case-series report, we presented a series of VAE cases in our institute during the last 6 consecutive years. There were total of nine cases suspected to be VAE according the clinical symptom and signs, of which seven cases were definitively diagnosed VAE using transthoracic echocardiography (TTE). We also reported two presumptive cases of paradoxical VAE during hepatectomy in this case series, furthermore, the cause, complications and hazards secondary to paradoxical VAE were discussed as well. All cases had an uneventful recovery from VAE with the assistance of TTE as well as other therapeutic management of VAE, except one neurosurgical patient died from postoperative hemorrhagic stroke per se. Therefore, VAE or paradoxical air embolism can occur during various non-cardiac operations and the significance of perioperative ultrasound should be emphasized in the treatment of VAE.

Sevoflurane versus PRopofol combined with Remifentanil anesthesia Impact on postoperative Neurologic function in supratentorial Gliomas (SPRING): protocol for a randomized controlled trial

Background

Patients with intracranial tumors are more sensitive to anesthetics than the general population and are therefore more susceptible to postoperative neurologic and neurocognitive dysfunction. Sevoflurane or propofol combined with remifentanil are widely used general anesthetic regimens for craniotomy, with neither regimen shown to be superior to the other in terms of neuroprotective efficacy and anesthesia quality. There is no evidence regarding the variable effects on postoperative neurologic and neurocognitive functional outcome under these two general anesthetic regimens. This trial will compare inhalational sevoflurane or intravenous propofol combined with remifentanil anesthesia in patients with supratentorial gliomas and test the hypothesis that postoperative neurologic function is equally affected between the two regimens.

Methods

This is a prospective, single-center, randomized parallel arm equivalent clinical trial, which is approved by China Ethics Committee of Registering Clinical Trials (ChiECRCT-20,160,051). Patients with supratentorial gliomas diagnosed by magnetic resonance imaging will be eligible for the trial. Written informed consent will be obtained before randomly assigning each subject to either the sevoflurane-remifentanil or propofol-remifentanil group for anesthesia maintenance to achieve an equal-desired depth of anesthesia. Intraoperative intervention and monitoring will follow a standard anesthetic management protocol. All of the physiological parameters and other medications administered during the intervention will be recorded. The primary outcome will be neurologic function change assessed by National Institute of Health Stroke Scale (NIHSS) within 4 h after general anesthesia when observer’s assessment of alertness/sedation (OAA/S) reaches 4. Secondary outcomes will include NIHSS and modified NIHSS change 1 and 2 days after general anesthesia, hemodynamic stability, intraoperative brain relaxation, quality of anesthesia emergence, quality of anesthesia recovery, postoperative cognitive function, postoperative pain, postoperative neurologic complications, as well as perioperative medical expense.

Discussion

This randomized equivalency trial will primarily compare the impacts of sevoflurane-remifentanil and propofol-remifentanil anesthesia on short-term postoperative neurologic function in patients with supratentorial gliomas undergoing craniotomy. The exclusion criteria are strict to ensure that the groups are comparable in all aspects. Repeated and routine neurologic evaluations after operation are always important to evaluate neurosurgical patients’ recovery and any newly presenting complications. The results of this trial would help specifically to interpret anesthetic residual effects on postoperative outcomes, and perhaps would help the anesthesiologist to select the optimal anesthetic regimen to minimize its impact on neurologic function in this specific patient population.

Trial registration

The study was registered and approved by the Chinese Clinical Trial Registry (Chinese Clinical Trial Registry, ChiCTR-IOR-16009177). Principle investigator: Nan Lin (email address: linnan127@gmail.com) and Ruquan Han (email address: hanrq666@aliyun.com) Date of Registration: September 8th, 2016. Country of recruitment: China.