Incidence Of Venous Air Embolism Research Articles

The safety and utility of the semi-sitting position for clipping of posterior circulation aneurysms

BackgroundThe semi-sitting position offers advantages for surgeries in the posterior cranial fossa. However, data on its safety and effectiveness for clipping aneurysms in the posterior cerebral circulation are limited. This retrospective cohort study evaluates the safety and effectiveness of using the semi-sitting position for these surgeries.MethodsWe conducted a retrospective study of 17 patients with posterior cerebral circulation aneurysms who underwent surgical clipping in the semi-sitting position in the Department of Neurosurgery at Hannover Medical School over a 10-year period.ResultsThe mean age at surgery was 62 years (range, 31 to 75). Fourteen patients were admitted with subarachnoid hemorrhage and 3 patients had incidental aneurysmas. Fifteen patients had PICA aneurysms, and two had aneurysms of the vertebral artery and the superior cerebellar artery, respectively. The median diameter of the aneurysms was 5 mm (range 3–17 mm). Intraoperative venous air embolism (VAE) occurred in 4 patients, without affecting the surgical or clinical course. VAE was associated with a mild decrease of EtCO2 levels in 3 patients and in 2 patients a decrease of blood pressure occurred which was managed effectively. Surgical procedures proceeded as planned in all instances. There were no complications secondary to VAE. Two patients died secondary to respiratory problems (not related to VAE), and one patient was lost to follow-up. Eleven of fourteen patients were partially or completely independent (Barthel index between 60 and 100) at a median follow-up duration of 13.5 months (range, 3–103 months).ConclusionThe semi-sitting position is a safe and effective technique for the surgical clipping of aneurysms in the posterior cerebral circulation. The incidence of VAE is comparable to that seen in tumor surgery. However, it is crucial for the surgical and anesthesiological team to be familiar with potential complications and to react immediately in case of an occurrence of VAE.

Gas Pressure From the Endoscope: An Unexplored Contributor to Morbidity and Mortality?

Background It has been shown that the incidence of venous air embolism and venous carbon dioxide (CO2) embolism is high during endoscopic retrograde cholangiopancreatography (ERCP). We examined insufflating gas flow and maximum pressure produced by three types of commonly used endoscopes because we could not readily locate technical data for endoscope gas flow and maximum emitted pressure in the manufacturer's manuals. Methods We tested the Olympus GIF-Q180 used for esophagogastroduodenoscopy, the CF-Q180 used for colonoscopy, and the TJF-Q180 used for ERCP (Olympus America Inc., Center Valley, Pennsylvania). Under three different clinical gas insufflation scenarios, we measured in vitro maximum gas pressure transduced from a closed space created at the endoscope tip in a worst-case scenario analysis. Results We showed that it is readily possible to generate a pressure (>5-30 times normal central venous pressure) in the air space at the tip of all three endoscopes when insufflation is activatedand the gas egress is limited. Conclusions These findings shedadditional light on in vivo occurrences of gas embolism during gastrointestinal endoscopy. We postulate that in addition to using exclusively CO2 as the insufflating gas, the risk of gas embolism can be further diminished by regulating insufflating gas pressure at the tip of endoscopes.

Analysis of risk factors for venous air embolism in the semisitting position and its impact on outcome in a consecutive series of 740 patients.

Routine use of the semisitting position, which offers several advantages, remains a matter of debate. Venous air embolism (VAE) is a potentially serious complication associated with the semisitting position. In this study, the authors aimed to investigate the safety of the semisitting position by analyzing data over a 20-year period. The incidence of VAE and its perioperative management were analyzed retrospectively in a consecutive series of 740 patients who underwent surgery between 1996 and 2016. The occurrence of VAE was defined by detection of bubbles on transthoracic Doppler echocardiography (TTDE) or transesophageal echocardiography (TEE) studies, a decrease of end-tidal CO2 (ETCO2) by 4 mm Hg or more, and/or an unexplained drop in systolic arterial blood pressure (≥ 10 mm Hg). From 1996 until 2013 TTDE was used, and from 2013 on TEE was used. The possible risk factors for VAE and its impact on surgical performance were analyzed. There were 404 women and 336 men with a mean age at surgery of 49 years (range 1-87 years). Surgery was performed for infratentorial lesions in 709 patients (95.8%), supratentorial lesions in 17 (2.3%), and cervical lesions in 14 (1.9%). The most frequent pathology was vestibular schwannoma. TEE had a higher sensitivity than TTDE. While TEE detected VAE in 40.5% of patients, TTDE had a detection rate of 11.8%. Overall, VAE was detected in 119 patients (16.1%) intraoperatively. In all of these patients, VAE was apparent on TTDE or TEE. Of those, 23 patients also had a decrease of ETCO2, 18 had a drop in blood pressure, and 23 had combined decreases in ETCO2 and blood pressure. VAE was detected in 24% of patients during craniotomy before opening the dura mater, in 67% during tumor resection, and in 9% during wound closure. No risk factors were identified for the occurrence of VAE. Two patients had serious complications due to VAE. Surgical performance in vestibular schwannoma surgery was not affected by the presence of VAE. This study shows that the semisitting position is overall safe and that VAE can be managed effectively. Persistent morbidity is very rare. The authors suggest that the semisitting position should continue to have a place in the standard armamentarium of neurological surgery.

Abstract No.: ABS0480: A retrospective study observing outcome following posterior fossa craniotomy in patients with sitting position

Background & Aims:To assess the outcome following posterior fossa craniotomy in sitting position with respect to haemodynamic changes as well as intra and post operative complicationsMethods:The study involved reviewing the case records of 100 adult patients who underwent posterior fossa craniotomy in sitting position under general anaesthesia. In these patients, induction was done with thiopentone sodium 5mg/kg. Neuromuscular blockade was achieved with vecuronium bromide 0.1mg/kg to facilitate intubation. Radial arterial line was inserted preferably in left hand side for invasive blood pressure monitoring. Patients were positioned in sitting position slowly over 20-30 minutes. Vital parameters of the patients were monitored during and after positioning. Patients were observed in ICU for first 48 hours for neurological status, cardiovascular status, respiratory and surgical complications.Results:We found significant haemodynamic changes during and after sitting position which normalised after 2 hours of position. There were no perioperative cardiac events and neurological alteration. The incidence of venous air embolism was 2 % and it was not associated with any postoperative morbidity and mortalityConclusion:Present study concluded that the use of sitting position for patients undergoing posterior fossa surgery is safe.Tumour TypePatients (n=100) Vestibular schwannoma36Meningioma27Epidermoid inclusion cyst20Astrocytoma5Glioma4Haemangioblastoma3Medulloblastoma3Ependymoma2

The semisitting position in pediatric neurosurgery: pearls and pitfalls of a 10-year experience.

The authors sought to investigate the pearls and pitfalls of using the semisitting position in pediatric neurosurgery, with special focus on related morbidity and surgical practicability. All pediatric cases at a single institution were evaluated retrospectively. Those patients who underwent procedures in the semisitting position between December 2010 and December 2020 were included in the final analysis. Results were compared with all children who underwent surgery in the prone position for posterior fossa lesions within the same time frame. A total of 42 posterior fossa surgeries were performed in 38 children in the semisitting position between December 2010 and December 2020. The mean patient age at the time of surgery was 8.9 years (range 13 months-18 years). The data of 24 surgeries performed in the prone position in 22 children during the same time frame were analyzed in comparison. Three children (7.9%) were diagnosed with a persistent foramen ovale preoperatively. The surgery was completed in all cases. The incidence of venous air embolism (VAE) was 11.9%. There was no VAE-related hemodynamic instability, infarction, or death. Endoscopic techniques were applied safely in 14 cases (33.3%). Postoperative pneumocephalus occurred significantly more frequently in patients who had undergone procedures in the semisitting position (p < 0.05), but without the need for intervention. During 1 surgery (2.4%), the patient experienced a postoperative skull fracture and epidural bleeding due to the skull clamp application. Clinical status of the patients immediately after surgery was improved or stable in 33 of the 42 surgeries (78.6%) performed in the semisitting position. With attentive performance and an experienced surgical team, the semisitting position is a safe option for posterior fossa surgery in the pediatric population. With a comparable complication profile, the semisitting position offers excellent anatomical exposure, which is ideal for the application of endoscopic visualization. Careful skull clamp application and appropriate monitoring are highly recommended.

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).

Reducing the incidence of venous air embolism in contrast-enhanced CT angiography using preflushing of the power injector

To evaluate whether preflushing before connecting a power injector to a patient's catheter reduces the incidence of venous air embolism (VAE) in contrast-enhanced computed tomography (CT) angiography (CTA). With the approval from the local ethics committee, consecutive patients were divided randomly into a control group and a preflushing group and underwent CTA from June to November 2017. The control group underwent the conventional injection procedure. In the preflushing group, the injector tubes were flushed at high speed (10 ml/s) with saline before being connected to the patients' indwelling catheters. The locations, number, and sizes of VAE were analysed. The difference in the incidence of VAE between the two groups was compared. A total of 4,900 adults (control/preflushing, 2,190/2,710) were included and 228 (4.65%) patients were found to have 318 VAEs (285 bubbles and 33 gas-liquid plane VAEs). The incidence of VAE in the preflushing group (3.21%) was lower than that in the control group (6.44%); a similar trend was observed for multiple VAEs (p<0.05). VAEs occurred in the following locations from high to low frequency: right atrium>pulmonary artery trunk>superior vena cava>right ventricle>left brachial vein>right brachial vein. There was no significant difference in the location, shape, or diameters (p=0.19) of VAEs between the two groups. The proposed preflushing procedure is simple yet effective in reducing the incidence of VAE by 50.16% in patients with CTA, thus improving safety during power injection.

Association of the incidence of venous air embolism on coronary computed tomography angiography with the intravenous access route preparation process.

Venous air embolism (VAE) can be observed in the right heart system on contrast-enhanced computed tomography (CT), following injection of contrast media with a power injector system. Although most VAEs are mostly asymptomatic, they may result in paradoxical air embolism (PAE).To evaluate whether the incidence of VAE on coronary CT angiography is associated with the process of preparation of the intravenous access route.We retrospectively evaluated 692 coronary CT examinations at 3 institutions. Trained CT nurses placed an intravenous cannula in the forearm. Tubes connected to the cannula were prepared in the following ways: A, using an interposed three-way cock and a 20-mL syringe filled with normal saline to collect air contamination in the tube; B, through direct connection to the power injector system without the interposed 3-way cock; and C, using an interposed three-way cock and a 100-mL normal saline drip infusion bottle system to keep the tube patent. The incidence and location of VAE and preparation of intravenous injection were assessed.The overall incidence of VAE was 55.3% (383/692), most frequently observed in the right atrium (81.5%, 312/383). Its incidence varied significantly across the 3 techniques (A: 21.6% (35/162), B: 63.2% (237/375) and C: 71.6% (111/155); P < .001). No patient demonstrated any symptom associated with VAE.Using a 3-way cock with syringe demonstrated the lowest incidence of VAE on coronary CT angiography. It is thus recommended to reduce potential complication risks related to intravenous contrast media injection.

In Response

In Response We thank White et al1 for their constructive comments regarding our “Incidence of Venous Air Embolism During Endoscopic Retrograde Chol angiopancreatography” study.2 We also use Olympus endoscopes (Olympus, Tokyo, Japan) and Evis Exera lll CLV-190 (Olympus, Tokyo Japan) light source–/gas-regulating units (used only as a light source when CO2 used). We use a Bracco CO2MPACT Endoscopic Insufflator (US Endoscopy, Mentor, OH) for carbon dioxide (CO2) insufflation. The Bracco CO2 insufflator has low, medium, and high settings delivering 2.0, 2.9, and 3.4 L/min, respectively. The Bracco unit has a fixed mechanical pressure relief valve set at 375 mm Hg. We agree with the possibility that different endoscopes and gas-regulating units could deliver varying pressures and affect the incidence of gas embolism. We also concur that the gas pressure delivered through the endoscope using air or CO2 greatly exceeds central venous pressure. While insufflation pressure was not reported in our study, it stands to reason that higher pressures are associated with an increased likelihood of an embolic event. Like White et al1, we now exclusively use CO2 as an insufflation medium during endoscopic retrograde cholangiopancreatography, and to date we have not observed any incidents of a hemodynamically significant embolism. We appreciate the reminder of the steps to manage a significant gas embolism. Rapid recognition and treatment will hopefully prevent (or lessen) serious adverse consequences. Increasing the awareness of the risk of an embolism and having a protocol for prompt management by the entire clinical team involved in gastrointestinal procedures (eg, physicians, anesthesia staff, and nursing staff) will optimize the likelihood of a good outcome. Mark C. Phillips, MD, FASATimothy J. Ness, MD, PhDAyesha S. Bryant, MSPH, MDDepartment of Anesthesiology and Perioperative MedicineUniversity of Alabama at BirminghamBirmingham, Alabama[email protected]

Incidence of Venous Air Embolism During Endoscopic Retrograde Cholangiopancreatography

Known complications of endoscopic retrograde cholangiopancreatography (ERCP) include pancreatitis, bleeding, duodenal perforation, and venous air embolism (VAE). The aim of this study was to determine the incidence of VAE during ERCP and be able to differentiate high-risk versus low-risk ERCP procedures. This is a prospective cohort study consisting of patients who underwent ERCP and were monitored with a precordial Doppler ultrasound (PDU) for VAE. PDU monitoring was digitally recorded and analyzed to confirm the suspected VAE. Demographic and clinical data related to the anesthetic care, endoscopic procedure, and intraoperative hemodynamics were analyzed. A total of 843 ERCP procedures were performed over a 15-month period. The incidence of VAE was 2.4% (20 patients). All VAE's occurred during procedures in which stent placement, sphincterotomy, biopsy, duct dilation, gallstone retrieval, cholangioscopy, or necrosectomy occurred. Ten of 20 (50%) of VAEs were associated with hemodynamic alterations. None occurred if the procedure was only diagnostic or for stent removal. Subanalysis for the type of procedure showed that VAE was statistically more frequent when stents were removed and then replaced or if a cholangioscopy was performed. The high incidence of VAE highlights the need for practitioners to be aware of this potentially serious event. Use of PDU can aid in the detection of VAE during ERCP and should be considered especially during high-risk therapeutic procedures. Detection may allow appropriate interventions before serious adverse events such as cardiovascular collapse occur.

Bubble Trouble: Venous Air Embolism in Endoscopic Retrograde Cholangiopancreatography.

The advent of advanced endoscopy has brought about a new era of diagnostic and therapeutic procedures, which have the potential to address disease in less invasive manner. However, these procedures bring their own set of risks, such as pancreatitis, cholangitis, bleeding, perforation, and sedation risks. In addition, venous air embolism is a potentially catastrophic complication. In this infographic, we review the risk factors and incidence of venous air embolism in endoscopic retrograde cholangiopancreatography and highlight the associated procedures that have the highest degree of associated risk. ERCP indicates endoscopic retrograde cholangiopancreatography; VAE, venous air embolism.

Incidence of venous air embolism and blood gas changes seen in infratentorial surgeries operated in sitting position

Our aim was to find out the rate and timing of venous air embolism (VAE), other complications associated with sitting position and changes on arterial blood gas during and after VAE. We analyzed retrospectively files of 124 patients who underwent posterior fossa surgery in department of Neurosurgery of our institute between January 2004 and April 2014. The incidence of emboli was 76,3% in the first 3 hours of the surgery while it was 38.2% in the first 2 hours in total. VAE was seen in a total of 21 patients (16.9%) and it was detected by a sudden drop of minimum 2mmHg of end-tidal CO2 (EtCO2)(25.38 ± 3.28 mmHg) in all cases (100%). The pH, PaO2 and PaCO2 values of the patients with and without emboli were evaluated pre and post-operatively and no significant difference was found (p>0.05). Precordial doppler ultrasonography is the most sensitive non-invasive monitoring device for accurate detection of even small VAE which are not clinically relevant. The most sensitive technique for detection of VAE is transoesophageal echocardiography but it is expensive, invasive and can cause some serious complications. In our study, emboli were most frequently seen in the 3rd hour of the surgery which coincide with tumor resection, thus proposing anaesthesiologists to be more cautious about VAE and EtCO2 during the tumor resection period.

Complications related to sitting position during Pediatric Neurosurgery: An institutional experience and review of literature.

Sitting position is preferred during posterior fossa surgeries as it provides better anatomical orientation and a clear surgical field. However, its use has been declining due to its propensity to cause life-threatening complications. This study was carried out to analyze the perioperative complications and postoperative course of children who underwent neurosurgery in sitting position. Medical records of 97 children (<18 years) who underwent neurosurgery in sitting position over a period of 12 years, were retrospectively analyzed. Data pertaining to the perioperative course such as demographics, hemodynamic changes, various complications, duration of intensive care unit (ICU) and hospital stay, and neurological status at discharge were recorded. Statistical analysis was done by chi-square and Mann-Whitney test, and a P value <0.05 was considered as significant. The median age of these children was 12 (3-18) years. Hemodynamic instability was observed in 12 (12.3%) children. A total of 38 episodes of venous air embolism (VAE) were encountered in 21 (21.6%) children; nine experienced multiple episodes. VAE was associated with hypotension in five (23.8%) and desaturation in four (19.1%) children. Six children presented with postoperative tension pneumocephalus; three were managed with twist drill burr-hole evacuation. Brainstem handling was the most common indication (42.5%) for the requirement of elective postoperative ventilation. The duration of ICU and hospital stays were comparable among the children who experienced VAE and those who did not (P > 0.05). Neurological status at discharge was also comparable between these two groups (P = 0.83). This study observed a lesser incidence of VAE and associated complications. Tension pneumocephalus was managed successfully without any adverse outcome. Hence, it is believed that with meticulous anesthetic and surgical techniques, sitting position can safely be practiced in children undergoing neurosurgery.

A prospective study observing outcome following posterior fossa craniotomy in patients with sitting position

Aims and Objective: To assess the outcome following posterior fossa craniotomy in sitting position with respect to hemodynamic changes as well as intra and post operative complications. Material and Method: The present study was conducted in150 adult patients undergoing posterior fossa craniotomy in sitting position under general anaesthesia. Induction was done with thiopentone sodium 5mg/kg. Neuromuscular blockade was achieved with vecuronium bromide 0.1mg/kg to facilitate intubation. Radial arterial line was inserted preferably in left hand side for invasive blood pressure monitoring. Sitting position was given to patients slowly over 20-30 minutes. Vital of the patients were monitored during and after giving sitting position. Patients were observed in ICU for first 48 hrs for neurological status, cardiovascular status, respiratory and surgical complications. Results: We found significant hemodynamic changes during and after giving sitting position to the patients which returned back to normal after 2 hrs of position. There were no perioperative cardiac events and neurological alteration. The incidence of venous air embolism was 5.3% and it was not associated with any postoperative morbidity and mortality. Other complications observed were pneumocephalous (0.7%), tongue oedema (2%) and glossopharyngeal nerve palsy (0.7%). Conclusions: Use of sitting position for posterior fossa surgery is safe anesthetic techniques and presents unique challenges for the anesthetist; taking measures to minimize hypotension and postoperative complications.

The role and safety of the sitting position in instrumented cervical surgery

Placing patients who are undergoing neurosurgical procedures to the cervical spine in the sitting position offers significant advantages. These must be counterbalanced against the risk of venous and paradoxical air embolism. This study addresses the role and safety of the sitting position for instrumented cervical surgery. Twenty-five consecutive patients who underwent instrumented cervical surgery in the sitting position were recruited via retrospective analysis. Complications arising from the surgical procedure – specifically venous air embolism – were recorded, as well as pre- and post-operative haemoglobin levels. The incidence of venous air embolism was 0% (97.5% one-sided confidence interval: 0–13.7%). However, five other complications occurred (incidence rate of 20% with a 95% confidence interval of 6.8–40.7%). With appropriate precautions, screening and specific indications, the sitting position can be safely used in more complex instrumented cervical surgery.

POGOSTOST ZRAČNE EMBOLIJE IN POOPERATIVNI ZAPLETI PRI NEVROKIRURŠKIH POSEGIH V SEDEČEM POLOŽAJU Skrajšana verzija naslova: ZRAČNA EMBOLIJA PRI NEVROKIRURŠKIH POSEGIH V SEDEČEM POLOŽAJU

Background: Posterior fossa surgery and cervical spine surgery are at risk for venous air embolism (VAE) occurrence. Mostly air emboli are small and asymptomatic, but invasion of large quantity of air in the circulation is symptomatic and potentially lethal. Transesophageal echocardiography is the most sensitive method for detection of air emboli in the heart, followed by the precordial Doppler probe, end tidal carbon dioxide monitoring (etCO2) and others.Methods: In our 14- years retrospective review we evaluated the incidence of VAE and postoperative complications in patients with posterior fossa surgery or cervical spine surgery. VAE was recognized by using Doppler probe and/or drop of etCO2. If VAE occurred, aspiration of air through the CVC was used to prevent or to minimized VAE occurrence, the surgeon was warned about the incident. VAE treatment was supportive.Results: VAE was recognized in 74 patients. Two patients after head surgery and four patients after neck surgery needed postoperative treatment in intensive care unit and controled mechanical ventilation. In six patients after head surgery and in four patients after neck surgery new neurological symptoms occurred. Two patients after head surgery died due to complications of massive VAE.Conclusions: VAE is rare, but serious complication of neurosurgery in sitting position. Preventive treatment, early detection of VAE, supportive treatment and treatment of cardiovascular complications are necessary for survival of patients with VAE.

Detección de embolismo aéreo venoso y de foramen oval permeable en pacientes neuroquirúrgicos intervenidos en posición de sedestación

Early detection of venous air embolism (VAE) during neurosurgical procedures in sitting position decreases the severity of its complications. our aim was to analyse the detection of VAE and its impact on patients operated in a sitting position, verify air aspiration through a central venous catheter and assess the feasibility of the routine use of transcranial Doppler (TCD) for intraoperative diagnosis of patent foramen ovale (PFO). We performed a prospective study of consecutive neurosurgical procedures performed in the sitting position for 5 years. Precordial Doppler and end-tidal carbon dioxide were the diagnostic methods for VAE. PFO was explored by TCD after anaesthetic induction. 136 patients were operated in the sitting position, 93 craniotomies and 43 cervical spine procedures. Twenty-two patients (16.2%) were diagnosed with VAE (21.5% of craniotomies and 4.7% of spinal surgeries; p=.013). In 59% of cases, air was aspirated through the central venous catheter. There was haemodynamic involvement in 3 patients, impaired oxygenation in 4 and clinically relevant pneumocephalus in 5 of them. Two patients (1.4%) were diagnosed with PFO, but did not present episodes of VAE or paradoxical air embolism. The series analysed confirmed a higher incidence of VAE in craniotomies than in cervical spine surgery in a sitting position. We were able to aspirate air through the central venous catheter in more than half the cases. No patients suffered critical intraoperative complications following our approach. The low incidence of PFO detected with TCD will imply a modification of our protocol performed on anaesthetised patients.

Venous air embolism during vitrectomy: a rare but potentially fatal complication.

Over 4,000 articles have been published on intraoperative venous air embolism (VAE) since it was first described in the 19th century [1]. Although its pathological mechanisms, preventative measures, and treatment methods have been established, it still appears consistently. VAE occurs when the pressure in an open vein is lower than atmospheric pressure. Thus, it is caused when a wound is at a higher level than the heart. The pathophysiological consequences of VAE depend on the velocity and quantity of air entry. Air bubbles flowing into the venous system lodge in the pulmonary circulation and are then diffused to alveoli to be exhaled during expiration. In most patients, a small quantity of air bubbles is tolerable. However, if the amount of air exceeds the pulmonary clearance capacity, increasing pulmonary artery pressure and, thus, increased right ventricular afterload, which may cause cardiac arrest. In particular, in patients with patent foramen ovale, paradoxical air embolism can result in a stroke or coronary occlusion, which may be fatal. General management of VAE includes notifying the operating surgeon, procedure discontinuance, use of 100% oxygen, aspiration of entrained air through a central venous catheter, aggressive intravascular volume infusion, use of a vasopressor, bilateral jugular vein compression, placing the patient in a headdown position and, if necessary, cardiac pulmonary resuscitation (CPR). It is known that VAE occurs most commonly during sitting craniotomy [1]. However, suitable conditions for it can occur whenever a wound is above the level of the heart. In this issue of the Korean Journal of Anesthesiology, Shin et al. [2] report VAE occurring during vitrectomy with airfluid exchange. One patient who was under mechanical ventilation with an oxygen/air mixture suddenly showed findings of cardiac arrest after starting air-fluid exchange. Although the surgical procedure was stopped quickly and CPR was performed, vital signs did not recover and thus percutaneous cardiopulmonary support was applied. Postoperative transesophageal echocardiogram revealed a patent foramen ovale. VAE can occur during various surgical procedures [1] but it is rare in ophthalmic surgery. The first case report was published by anesthesiologists in 2005 [3] and it was then first introduced in an ophthalmology journal in 2010 [4]. In sitting craniotomy, where the incidence of VAE is among the highest, neurosurgeons are well aware of VAE but ophthalmic operating surgeons tend not to be. Highlighting this, an interesting study was recently conducted by ophthalmologists [5]. Four donor eyes unsuitable for tissue donation were used for simulated vitrectomies. This experiment was performed with 23- or 25-gauge cannulas under several intraocular pressures (30-60 mmHg). They measured air flow against atmospheric pressure to be ~350 ml/min under 40 mmHg infusion pressure through a 25-gauge line. Considering that an air volume of 200 ml (35 ml/kg) may be fatal [1], both ophthalmologists and anesthetists should be aware that ocular air fluid exchange is not completely safe and may even be fatal, especially for patients with patent foramen ovale. Fortunately, not all air bubbles flowing in the venous system during vitrectomy surgery are potentially fatal. However, like the case described in this issue of the Korean Journal of Anesthesiology, complications in patients with other risk factors may be fatal. Thus, continuous preoperative and intraoperative attention by operating surgeons and anesthetists is required to prevent it.

The sitting position in neurosurgery: indications, complications and results. a single institution experience of 600 cases

The benefit of the sitting position for surgery of the posterior fossa and cervical spine is still a matter of controversy. In our study we analyzed the outcome after sitting position surgery at our institution. We compared the incidence of venous air embolism (VAE) as recognized with different monitoring techniques and the severity of complications. We retrospectively analyzed 600 patients, who underwent surgery for different posterior fossa and cervical spine pathologies, respectively, in the sitting position at our institution from 1995 to 2011. Intraoperative monitoring for VAE included endtidal CO2 level, Doppler ultrasound or intraoperative transesophageal echocardiography (TEE). We defined VAE as a decrease of the endtidal CO2 levels by more than 4 mm Hg, a characteristic sound in the thoracic Doppler, or any sign of air in the TEE. We found an overall incidence of VAE in 19 % of all patients, whereas the rate of severe complications associated with VAE such as a decline of partial oxygen pressure (pO2) or a drop of blood pressure was only 3.3 % in all patients. Only three out of 600 operations had to be terminated because of non-controllable VAE (0.5 %). There was no mortality resulting from VAE in our series. We also found a difference in the incidence of VAE depending on the monitoring technique. The VAE rate as monitored with TEE was 25.6 % whereas the incidence of VAE in patients monitored with Doppler ultrasound was 9.4 %. The rate of a significant VAE was comparable in both methods 4.8 % vs. 1.2 %. All patients were preoperatively screened for persisting foramen ovale (PFO); 24 patients with clinically confirmed PFO were included in this series. There was no case of paradox air embolism. In our series, VAE was detected in 19 % of all patients in the sitting position. However, in only 0.5 % of cases a termination of the surgical procedure became necessary. In all other cases, the cause of air embolism could be found and eliminated during surgery. TEE was found to be the monitoring technique with the highest sensitivity. In our opinion, the sitting position is a safe positioning technique if TEE monitoring is used.

Venous air embolism from Tisseel use during endoscopic cranial vault remodeling for craniosynostosis repair: a case report

Venous air embolism (VAE) is a potential complication during cranial vault remodeling requiring early detection and prompt therapeutic intervention. The incidence of VAE has been reported to be as high as 82.6% during open craniectomy for craniosynostosis repair. On the other hand, two separate studies reported a much lower incidence of VAE (8% and 2%) during endoscopic strip craniectomy. As surgical advancements progress, minimally invasive neurosurgical procedures are increasing in the pediatric population with reported benefits of decreased blood loss and need for transfusion, shorter hospital stay, decreased cost, lower morbidity, and mortality. In addition, there is a heightened emphasis on achieving hemostasis, which has led to the use of products such as antifibrinolytics and fibrin sealants. We present a case where a VAE causing significant hemodynamic instability (grade III) ensued immediately following aerosolized fibrin sealant application. Exploration of the potential source of VAE pointed to the high pressure and close proximity (between spray device and tissue) during application of the sealant, likely forcing air into the vascular system.