Semisitting position for cerebello-pontine angle surgery: Analysis of complications and how to avoid it

OBJECTIVE

To analyze the primary complications related to semisitting position in patients undergoing cerebelo-pontine angle surgery.

METHODS

Retrospective data analysis from patients undergoing elective tumoral cerebelo-pontine angle surgery in a semisitting position. The incidence, severity, occurrence moment, treatment, duration, and outcomes of venous air embolism (VAE), pneumocephalus, postural hypotension, and other complications were recorded. Neurointensive care unit (NICU), length of stay (LOS), hospital LOS, and modified Rankin scale scores were calculated six months after surgery.

RESULTS

Fifty patients were operated on. Eleven (22%) presented VAE (mean duration 8±4.5min): five (10%) during tumor resection, and four (8%) during dural opening. Ten (20%) were resolved by covering the surgical bed, air bubbles aspiration, jugular compression, and one (2%) tilted to a steep Trendelenburg position. One (2%) had intraoperative hemodynamic instability. The only variable associated with VAE was meningioma at histopathology OR=4.58, p=0.001. NICU was higher in patients with VAE (5.5±1.06 vs. 1.9±0.20 days, p=0.01). There were no differences in the Rankin scale. All patients presented postoperative pneumocephalus with a good level of consciousness, except one (2%) who required evacuation. Seven patients (14%) showed postural hypotension, three (6%) after positioning, and one (2%) after developing a VAE; all were reversed with usual vasoactive drugs. No other position-related complications or mortality were registered in this series.

CONCLUSIONS

The semisitting position is a safe option with the knowledge, prevention, detection, and early solution of all the possible complications. The development of VAE rarely implies hemodynamic instability or greater disability after surgery. Postoperative pneumocephalus is very common and rarely requires evacuation. Excellent cooperation between anesthesia, nursing, neurophysiology, and neurosurgery teams is essential to manage complications.

Resection of posterior fossa tumors in the semi-sitting position in children younger than 4 years of age

PURPOSE

The semi-sitting position for resection of posterior fossa tumors is a matter of ongoing debate. Here we report about our experience with this approach in children younger than 4 years of age.

METHODS

We retrospectively analyzed data of children younger than 4 years of age operated on in our institution in the semi-sitting position over a 15-year period. Patients were intraoperatively monitored for venous air embolism (VAE) by transthoracic Doppler (TTD) or transesophageal echocardiography (TEE). The severity of VAE was classified according to the Tübingen grading scale. Intraoperative incidents of VAE were recorded and the patients' course was followed postoperatively with a special focus on possible complications.

RESULTS

Twenty-four children (18 boys, 6 girls) were operated on in the semi-sitting position (26 operations). Mean age was 2.2 years (± 1.0), range between 0.4 and 3.9 years. External ventricular drains were inserted in 18 children with hydrocephalus preoperatively. VAE was detected in 6 instances during surgery (6/26 (23.1%)). In 3 patients with grade 1 VAE, no additional treatment was necessary. In one patient with grade 2 VAE, intracardiac air suction via the central venous catheter was performed, and in two patients with grade 4 VAE, additional cathecholamine-infusion was administered. No major intraoperative complications occurred. Postoperative CT images showed pneumocephalus in all children. In two children, small asymptomatic impression skull fractures at the site of the Mayfield pin occurred. Revision surgery was necessary in one child with a suboccipital CSF fistula.

CONCLUSION

The semi-sitting position for resection of tumors in the posterior fossa in children younger than 4 years of age can be safely performed in experienced centers taking special caution to detect and treat potential complications in an interdisciplinary setting.

Massive Air Embolism Following Necrotizing Pancreatitis and COVID-19 Infection-The Role of Postmortem Computed Tomography

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that caused the COVID-19 pandemic raised important questions about workplace exposures to the virus, including postmortem exposures. The complexity of COVID-19 disease and its numerous unanticipated complications made autopsy even more vital in determining the pathophysiology of the disease. Performing traditional autopsy, however, carries risk of exposure. The following report describes an unusual case in which a patient diagnosed with COVID-19 and necrotizing pancreatitis underwent postmortem computed tomography (PMCT) prior to limited traditional autopsy and was unexpectedly found via PMCT to have large and diffuse venous air emboli and a new peripancreatic hematoma. In this case, not only did PMCT play a crucial role in determining the cause of death but also it allowed for a limited autopsy, thereby reducing the exposure to SARS-CoV-2 and associated risk to the autopsy staff and pathologists.

Disseminated intravascular coagulation following air embolism during orthotropic liver transplantation: is this just a coincidence?

BACKGROUND

During orthotopic liver transplantation, venous air embolism may occur due to iatrogenic injury of the inferior vena cava. However, venous air embolism followed by coagulopathy is a rare event. In this case report, we discuss a possible connection between venous air embolism and disseminated intravascular coagulation.

CASE PRESENTATION

A 37-year-old male patient with chronic hepatitis B- and C-induced liver cirrhosis was admitted for orthotopic liver transplantation. During the dissection phase of the surgery, arterial blood pressure, heart rate, saturation and end-tidal carbon dioxide levels suddenly decreased, indicating the occurrence of venous air embolism. After stabilizing the patient's condition, various coagulation issues started developing. Venous air embolism-induced coagulopathy was handled by administering transfusions of various blood products. However, the patient's condition continued to deteriorate leading to a complete asystole.

CONCLUSIONS

This is a rare case of venous air embolism-induced disseminated intravascular coagulation. The real connection remains unclear as disseminated intravascular coagulation for end-stage liver disease patients can be induced by various causes during different stages of liver transplantation. Certainly, both venous air embolism and coagulopathy were significant and led to an unfavorable outcome. Further studies are needed to better understand the possible mechanisms and correlation between these two life-threatening complications.

Finding the bubble: atypical and unusual extrapulmonary air in the chest

OBJECTIVE

To describe the radiologic findings of extrapulmonary air in the chest and to review atypical and unusual causes of extrapulmonary air, emphasizing the importance of the diagnosis in managing these patients.

CONCLUSION

In this article, we review a series of cases collected at our center that manifest with extrapulmonary air in the thorax, paying special attention to atypical and uncommon causes. We discuss the causes of extrapulmonary according to its location: mediastinum (spontaneous pneumomediastinum with pneumorrhachis, tracheal rupture, dehiscence of the bronchial anastomosis after lung transplantation, intramucosal esophageal dissection, Boerhaave syndrome, tracheoesophageal fistula in patients with esophageal tumors, bronchial perforation and esophagorespiratory fistula due to lymph-node rupture, and acute mediastinitis), pericardium (pneumopericardium in patients with lung tumors), cardiovascular (venous air embolism), pleura (bronchopleural fistulas, spontaneous pneumothorax in patients with malignant pleural mesotheliomas and primary lung tumors, and bilateral pneumothorax after unilateral lung biopsy), and thoracic wall (infections, transdiaphragmatic intercostal hernia, and subcutaneous emphysema after lung biopsy).

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.

Automatic detection of venous air embolism using transesophageal echocardiography in patients undergoing neurological surgery in the semi-sitting position: a pilot study

Neurological surgery in the semi-sitting position is linked with a pronounced incidence of venous air embolism (VAE) which can be fatal and therefore requires continuous monitoring. Transesophageal echocardiography (TEE) provides a high sensitivity for the intraoperative detection of VAE; however, continuous monitoring with TEE requires constant vigilance by the anaesthesiologist, which cannot be ensured during the entire surgical procedure. We implemented a fully automatic VAE detection system for TEE based on a statistical model of the TEE images. In the sequence of images, the cyclic heart activity is regarded as a quasi-periodic process, and air bubbles are detected as statistical outliers. The VAE detection system was evaluated by means of receiver operating characteristic (ROC) curves using a data set consisting of 155.14 h of intraoperatively recorded TEE video and a manual classification of periods with visible VAE. Our automatic detection system accomplished an area under the curve (AUC) of 0.945 if all frames with visible VAE were considered as detection target, and an AUC of 0.990 if frames with the least severe optical grade of VAE were excluded from the analysis. Offline-review of the recorded TEE videos showed that short embolic events (≤ 2 min) may be overseen when monitoring TEE video manually. Automatic detection of VAE is feasible and could provide significant support to anaesthesiologists in clinical practice. Our proposed algorithm might possibly even offer a higher sensitivity compared to manual detection. The specificity, however, requires improvement to be acceptable for practical application. Trial Registration: German Clinical Trials Register (DRKS00011607).

Intraoperative Visible Air Bubbling Recorded as a Sign of Massive Venous Air Embolism During Prone Position Surgery for Extensive Ossification of Spinal Ligaments: A Case Report with a Video Clip

BACKGROUND

Venous air embolism (VAE) is a rare but, frequently, fatal complication that can occur during surgery. Several reported studies have shown visible bubbling of air at the surgical site as the first clinical indication of VAE-induced cardiovascular collapse during prone-position spine surgery. However, to the best of our knowledge, video imaging of this phenomenon has not been previously reported.

CASE DESCRIPTION

A 41-year-old man had undergone cervical laminoplasty for ossification of the posterior longitudinal ligament and thoracic laminectomy for ossification of the posterior longitudinal ligament and ossification of the ligamentum flavum in the prone position. The entire surgery was recorded with video imaging. Before cardiac arrest due to the massive VAE, visible air bubbling had been observed at the operated site of the thoracic laminectomy, and this phenomenon had been incidentally recorded with the video. The patient recovered with cardiopulmonary resuscitation and intensive treatment against severe acute respiratory distress syndrome due to pulmonary damage.

CONCLUSIONS

The present case report offers the first video imaging evidence of intraoperative visible air bubbling as a sign of a massive VAE during prone-position spine surgery. To the best of our knowledge, this is also the first report of intraoperative VAE in a patient with extensive ossification of the spinal ligaments.

The use of end-tidal argon to detect venous air embolism: foiled by "fake oxygen!"

Venous air-embolism (VAE) potentially catastrophic complication surgery. Based on previous data using changes in end-tidal nitrogen as an indicator of VAE, we surmised that changes in end-tidal argon (EtAr) may be an indicator of VAE. We sought to determine if a commercial mass-spectrometer (PCT Proline Analyzer 61700-8 Class 85, Ametek, Pittsburgh, PA 15238) could be used to detect changes in EtAr in an invitro model. A Drager Apollo™ (Drager, Lubeck, Germany) anesthesia machine was used to ventilate a dummy lung (2 L bag) with a minute ventilation of 6 L/min in 100% oxygen. The quadrupole mass-spectrometer (sampling at 0.0004 atm-cc/sec) was attached to the end-tidal inlet of the machine. Room air (1-60 mL) was injected into the dummy lung to simulate VAE. A strong baseline ion-current (1.2 × 10^-12 amps) of argon was noted. Due to this contamination we were unable to detect "VAE" events of injected air. Argon represents approximately 0.93% of room air, or about 9300 parts per million (ppm). We detected about 2000 ppm argon in medical-grade oxygen (or 0.2%), limiting our ability to detect changes in EtAr. This is a USP-accepted contaminant, rendering this technology is insensitive for early, rapid detection of VAE. We assumed medical grade oxygen was pure and were surprised to learn otherwise. We want to share this likely largely unknown finding with the medical community.

Venous air embolism in the sitting position in cranial neurosurgery: incidence and severity according to the used monitoring

BACKGROUND

There is an ongoing debate about the sitting position (SP) in neurosurgical patients. The SP provides a number of advantages as well as severe complications such as commonly concerning venous air embolism (VAE). The best monitoring system for the detection of VAE is still controversial.

METHODS

In this retrospective analysis we compared 208 patients. Transesophageal echocardiography (TEE) or transthoracic Doppler (TTD) were used as monitoring devices to detect VAE; 101 cases were monitored with TEE and 107 with TTD.

RESULTS

The overall incidence of VAE was 23% (TTD: 10%; TEE: 37%), but the incidence of clinically relevant VAE (drop in end-tidal carbon dioxide above 3 mmHg) was higher in the TTD group (9 out of 17 VAE, 53%) compared to the TEE group (19 out of 62 VAE, 31%). None of the patients with recorded VAE had clinically significant sequelae.

CONCLUSIONS

In this small sample we found more VAE events in the TEE group, but the incidence of clinically relevant VAE was rare and comparable to other data. There is no consensus in the definition of clinically relevant VAE.

Bubbles in the Heart: A Case of Venous Air Thromboembolism

Introduction

Venous air embolism (VAE) due to central venous catheter (CVC) placement is a rare but preventable complication which is potentially fatal. We describe a case highlighting unique patient characteristics which increase the risk of developing VAE.

Case description

A sixty-year-old gentleman was admitted to the hospital with dyspnea and altered mental status. His comorbidities include cancer of the neck and tongue, currently in remission, and schizophrenia. On presentation, he was found to be in acute respiratory failure, due to pneumonia, and required mechanical ventilation. Following extubation, his CVC was removed from the right internal jugular vein. While ambulating around the unit, he experienced a coughing fit and dizziness. He rapidly developed cardiopulmonary collapse requiring re-intubation and vasopressor support. Chest x-ray demonstrated a radiolucent column along the lateral aspect of the right neck. Due to concern for VAE, an echocardiogram was performed, revealing multiple air-bubbles in the right and left chambers of the heart.

Discussion

Our patient was predisposed to developing VAE due to the extensive radiation induced skin changes, from his cancer treatment, on the neck and upper thorax. This resulted in loss of underlying subcutaneous tissue and decreased skin pliability. He had a large, open puncture wound at the catheter site on his neck, probably resulting in air entry. Anxiety and agitation, due to schizophrenia, made it difficult to maintain our patient in a supine or Trendelenburg position following CVC removal. This case highlights the importance of recognizing patient factors that may increase the risk of VAE.

Comparison of outcomes following complex posterior fossa surgery performed in the sitting versus lateral position

The sitting position during surgery is thought to provide important advantages, yet it remains controversial. We compared surgical and neurological outcomes for patients operated on in the sitting versus lateral position. Technically difficult procedures performed from the years 2001-2008 for complex lesions in the posterior fossa (vestibular schwannomas, other cerebellopontine angle tumors, foramen magnum meningiomas, brainstem cavernomas, pineal region tumors) were included. Outcomes in the two surgical positions were compared for all 243 patients (93 sitting, 38.3%; 150 lateral, 61.7%) and for 130/243 patients with vestibular schwannomas (50 sitting, 38.5%; 80 lateral, 61.5%). Sitting and lateral patient subgroups were clinically comparable. There were no surgical mortalities. The extent of removal and surgical and neurological outcomes were comparable. We found no advantage in surgical or neurological outcomes for use of the sitting or lateral surgical positions in technically difficult posterior fossa procedures. In vestibular schwannoma surgeries facial nerve preservation (House-Brackmann score 1-2) was related to extent of resection but not to surgical position. The choice of operative position should be based on lesion characteristics and the patient's preoperative medical status as well as the experience and preferences of the surgeons performing the procedure.

Simple handling of venous air embolism during abdominal myomectomy

We report a case of venous air embolism during abdominal myomectomy. Although true incidence of venous air embolism is not known, in literature most of reported cases are belongs to sitting position craniotomies. Many of those are subclinical, and diagnostic methods have varying degrees of sensitivity and specificity. At time of suspicion, prevention of any subsequent air emboli is the cornerstone of treatment.

Venous air embolism: an under-recognized and potentially catastrophic complication in orthopaedic surgery

INTRODUCTION

Venous air embolism (VAE) is the entry of air or other medical gases into the central venous system, producing an air embolism to the right heart or pulmonary artery. VAE is a largely iatrogenic complication with potentially devastating sequelae that can occur in a variety of surgical procedures.

METHOD

Within orthopaedics, VAE has been associated with both open and arthroscopic surgeries with the patient in a variety of positions (ie, prone, supine, sitting). These articles, as well as reports of VAE in other surgical settings outside of orthopaedics, are examined.

CONCLUSION

Diagnosis of VAE requires a high index of suspicion, as clinical presentation ranges from completely asymptomatic to fatal cardiopulmonary collapse. The vigilant surgeon should carefully watch for air entry at the operative site and the astute anesthesiologist must closely monitor end-tidal CO2 (ETCO2). Prevention of VAE is of paramount importance, as management is largely supportive and aimed at inhibiting further air ingress.

Neurosurgical procedures in the semisitting position: evaluation of the risk of paradoxical venous air embolism in patients with a patent foramen ovale

OBJECTIVE

To analyze the actual risk for patients with a patent foramen ovale (PFO) to experience a clinically relevant venous air embolism (VAE) during surgery performed in the semisitting position.

METHODS

All procedures were performed between January 2008 and December 2009, under general anesthesia and in the semisitting position. Transesophageal echocardiography (TEE) and capnometry were used intraoperatively to monitor for air bubbles in the venous system.

RESULTS

Of 200 consecutive patients who all were operated on in the semisitting position, 52 patients (26%) had a diagnosis of PFO. Rates of VAE in patients were graded as follows: grade 0 (no air bubbles visible, no air embolism), 23 patients (44.2%); grade I (air bubbles on TEE), 22 patients (42.3%); grade II (air bubbles on TEE with decrease of end-tidal carbon dioxide [ETCO2] ≤ 3 mm Hg), 2 patients (3.8%); grade III, air bubbles on TEE with decrease of ETCO2 >3 mm Hg, 4 patients (7.7%); grade IV, air bubbles on TEE with decrease of ETCO2 >3 mm Hg and decrease of mean arterial pressure ≥ 20% or increase of heart rate ≥ 40% (or both), 1 patient (1.9%); and grade V, VAE causing arrhythmia with hemodynamic instability requiring cardiopulmonary resuscitation, 0 patients (0%). There were no deaths in this series, and no new or unexplained, mild or severe neurologic deficits were caused by a VAE.

CONCLUSIONS

Under standardized anesthesia and neurosurgical protocols, patients with a PFO can be operated on safely in the semisitting position.

Prolonged paradoxical air embolism during intraoperative intestinal endoscopy confirmed by transesophageal echocardiography -A case report-

Venous air embolism (VAE) during intestinal endoscopy is a rare complication. We report a case of cardiovascular collapse due to VAE confirmed by transesophageal echocardiography (TEE) during intraoperative intestinal endoscopy. TEE detected air bubbles in the left ventricle up to 1 hour after the event. When a patient deteriorates during endoscopic procedures, VAE and possible paradoxical air embolism (PAE) should be suspected. This case demonstrates that TEE can play an important role in diagnosing and managing an air embolism in anesthetized patients. In addition, this case demonstrates that PAEs may occur longer than expected after recovery from VAE-induced cardiovascular collapse.