Neurosurgery in the Sitting Position: A Case Series

Medulloblastomas in Pediatric and Adults

Medulloblastoma is the primary malignant embryonic tumor of the cerebellum and the most common malignant tumor of childhood, accounting up to 25% of all CNS tumors in children, but is extremely rare in adults. Despite the fact that medulloblastomas are one of the most malignant human tumors, it is worthy to note that a great breakthrough has been achieved in our understanding of oncogenesis and the development of real methods of treatment. The main objective of surgical treatment is a maximum resection of tumor with minimal impairment of neurological functions, in order to reduce the volume, remove tumor tissue, get the biopsy, and restore the cerebrospinal fluid flow. The progress of surgical techniques (using a microscope, ultrasound suction), anesthesiology, and intensive care has significantly decreased surgical mortality and increased radicality of tumor removal. Postoperative mortality is less than one percent in most studies, while neurological complications have been reported between 5-10%. Radiotherapy is the main method of treatment in patients older than 3 years, which dramatically improved the recurrence-free survival. Nevertheless, the radiation therapy without systemic chemotherapy leads to a high risk of systemic metastases. After the role of chemotherapy was statistically proven, investigations of the optimal combination of different chemotherapy regimens continued around the world. Currently, 80% of patients can already be cured, however, the quality of life of patients in the long-term period remains quite low, which depends on many factors including endocrinological, cognitive, neurological, and otoneurologic aspects. Thus, the main strategic goal of the development of neuro-oncology is to reduce the doses of radiation therapy to the CNS and the main task of international research is to optimize existing protocols and develop fundamentally new ones based on molecular genetic research in order to improve the quality of life.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

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.

Vascular air embolism: A silent hazard to patient safety

PURPOSE

To narratively review published information on prevention, detection, pathophysiology, and appropriate treatment of vascular air embolism (VAE).

MATERIALS AND METHODS

MEDLINE, SCOPUS, Cochrane Central Register and Google Scholar databases were searched for data published through October 2016. The Manufacturer and User Facility Device Experience (MAUDE) database was queried for "air embolism" reports (years 2011-2016).

RESULTS

VAE may be introduced through disruption in the integrity of the venous circulation that occurs during insertion, maintenance, or removal of intravenous or central venous catheters. VAE impacts pulmonary circulation, respiratory and cardiac function, systemic inflammation and coagulation, often with serious or fatal consequences. When VAE enters arterial circulation, air emboli affect cerebral blood flow and the central nervous system. New medical devices remove air from intravenous infusions. Early recognition and treatment reduce the clinical sequelae of VAE. An organized team approach to treatment including clinical simulation can facilitate preparedness for VAE. The MAUDE database included 416 injuries and 95 fatalities from VAE. Data from the American Society of Anesthesiologists Closed Claims Project showed 100% of claims for VAE resulted in a median payment of $325,000.

CONCLUSIONS

VAE is an important and underappreciated complication of surgery, anesthesia and medical procedures.

Carbon dioxide field flooding reduces the hemodynamic effects of venous air embolism occurring in the sitting position

PURPOSE

Although the utility of the sitting position is undisputed for biomechanical and ergonomic reasons, it has been debated in recent years for its risks, particularly venous air embolism (VAE). In order to reduce the hemodynamic effect of VAE, we changed the composition of the surgical field air partially replacing nitrogen with carbon dioxide (CO2) that better dissolves in human tissues.

METHODS

First, we tested our method on a test dummy in the sitting position. Infrared CO2 sensors were placed close to the wound opening and on the facial mask of the surgeon. An oxygen sensor was connected to a computer for data recording (ALTAIR(®), MSA Safety). This model showed that 10 L/min CO2 flow provides efficient air displacement, maintaining safety for the surgeon. We reproduced the above-described surgical field environment in ten consecutive cases of posterior fossa surgery performed in the sitting position. A homogeneous group of ten patients operated in the sitting position with standard setting environment was used for control. We intraoperatively monitored VAE with trans-esophageal echocardiography (TEE), end-tidal CO2 (ETCO2), CO2 arterial pressure (PaCO2), and hemodynamic changes.

RESULTS

Although the percentage of VAE was 70% in both groups, hemodynamic effects occurred in 10% of cases in the study group and in 40% of cases in the control group.

CONCLUSIONS

Our preliminary study shows that a CO2-enriched sitting position surgical microenvironment significantly reduces the hemodynamic effects of VAE, more likely because arterial CO2 emboli are more soluble and consequently much better tolerated than air emboli.

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.

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.

Acute management of vascular air embolism

Vascular air embolism (VAE) is known since early nineteenth century. It is the entrainment of air or gas from operative field or other communications into the venous or arterial vasculature. Exact incidence of VAE is difficult to estimate. High risk surgeries for VAE are sitting position and posterior fossa neurosurgeries, cesarean section, laparoscopic, orthopedic, surgeries invasive procedures, pulmonary overpressure syndrome, and decompression syndrome. Risk factors for VAE are operative site 5 cm above the heart, creation of pressure gradient which will facilitate entry of air into the circulation, orogenital sex during pregnancy, rapid ascent in scuba (self contained underwater breathing apparatus) divers and barotrauma or chest trauma. Large bolus of air can lead to right ventricular air lock and immediate fatality. In up to 35% patient, the foramen ovale is patent which can cause paradoxical arterial air embolism. VAE affects cardiovascular, pulmonary and central nervous system. High index of clinical suspicion is must to diagnose VAE. The transesophgeal echocardiography is the most sensitive device which will detect smallest amount of air in the circulation. Treatment of VAE is to prevent further entrainment of air, reduce the volume of air entrained and haemodynamic support. Mortality of VAE ranges from 48 to 80%. VAE can be prevented significantly by proper positioning during surgery, optimal hydration, avoiding use of nitrous oxide, meticulous care during insertion, removal of central venous catheter, proper guidance, and training of scuba divers.

TEE monitoring for RA-horizontal paradoxical arterial air embolism during sitting-position surgery

A 36-year-old woman suffered meningioma in her right cerebellopontine angle. Air embolisms often complicate sitting-position surgeries. Because TEE guides the localization of central venous catheters and promptly locates air embolisms promptly enough for effective treatment, TEE is an effective monitoring method for sitting-position surgeries.

Acute management of vascular air embolism

Vascular air embolism (VAE) is known since early nineteenth century. It is the entrainment of air or gas from operative field or other communications into the venous or arterial vasculature. Exact incidence of VAE is difficult to estimate. High risk surgeries for VAE are sitting position and posterior fossa neurosurgeries, cesarean section, laparoscopic, orthopedic, surgeries invasive procedures, pulmonary overpressure syndrome, and decompression syndrome. Risk factors for VAE are operative site 5 cm above the heart, creation of pressure gradient which will facilitate entry of air into the circulation, orogenital sex during pregnancy, rapid ascent in scuba (self contained underwater breathing apparatus) divers and barotrauma or chest trauma. Large bolus of air can lead to right ventricular air lock and immediate fatality. In up to 35% patient, the foramen ovale is patent which can cause paradoxical arterial air embolism. VAE affects cardiovascular, pulmonary and central nervous system. High index of clinical suspicion is must to diagnose VAE. The transesophgeal echocardiography is the most sensitive device which will detect smallest amount of air in the circulation. Treatment of VAE is to prevent further entrainment of air, reduce the volume of air entrained and haemodynamic support. Mortality of VAE ranges from 48 to 80%. VAE can be prevented significantly by proper positioning during surgery, optimal hydration, avoiding use of nitrous oxide, meticulous care during insertion, removal of central venous catheter, proper guidance, and training of scuba divers.

Neurosurgical operations with the patient in sitting position: analysis of risk factors using transcranial Doppler sonography

BACKGROUND

One major risk factor of the sitting position for neurosurgery is air embolism, especially in patients with persistent foramen ovale (PFO). The first aim of this prospective study was to evaluate a bedside method for detecting PFO using transcranial Doppler sonography (TCD) with contrast medium. A second aim was to address intraoperative monitoring, patient positioning and the occurrence and clinical relevance of air embolism.

METHODS

Ninety patients with a mean age of 56.5 yr (range 14-81 yr) undergoing surgery in sitting position were investigated by TCD with contrast agent to detect functional PFO, that is PFO that can be provoked with a Valsalva manoeuvre. In patients in whom TCD was not possible, transcranial duplex sonography, duplex sonography of the carotid artery at the neck or transoesophageal ECG was performed.

RESULTS

In 26 patients PFO was detected. Thirteen of them presented a persistent PFO with high-intensity transient signal in both middle cerebral arteries without Valsalva manoeuvre. The intraoperative positioning in these patients was adapted to the risk for a paradoxical air embolism, although, after surgical recommendations, three patients with a persistent PFO underwent surgery in sitting position. Intraoperative air embolisms were seen in 8 of 80 patients in sitting or semi-sitting position with air aspirable through the central venous catheter.

CONCLUSION

To address the risk of a paradoxical air embolism, especially in patients undergoing surgery in sitting position, preoperative detection of PFO is advisable. If surgery is performed in seated PFO patients, additional monitoring and special care are warranted.