A standardized protocol for the prevention of clinically relevant venous air embolism during neurosurgical interventions in the semisitting position

[Supracerebellar transtentorial approach to tumors of the posterior portions of the medial temporal region]

OBJECTIVE

Despite the advances in microsurgery, the choice of the most adequate approach to the posterior part of the medial temporal region (MTR) remains a very controversial issue. The supracerebellar transtentorial approach (STA) is considered as the most preferable one, since it provides the optimal balance between retraction, incision, and resection of the brain tissue. Here, we present our consecutive series of 20 patients who underwent STA surgery.

MATERIAL AND METHODS

Twenty patients with glial tumors affecting the posterior MTR underwent STA surgery between 2006 and 2014. The mean age of the patients was 20 years. Benign tumors were predominant (18 out of 20 cases).

RESULTS

Resection of the posterior and middle MTRs was conducted in 16 cases. The anterior MTR was accessed through STA in 1 patient only; in 2 patients, STA was combined with the infraoccipital approach. Cerebellar edema occurred in 4 patients, with hemiparesis persisting in one of the cases for 1 year after surgery. Of 8 patients with drug resistant epilepsy, the Engel class 1 or 2 outcome was achieved in 6 cases within 1 year after surgery.

CONCLUSION

STA provides an excellent surgical route to the posterior and middle MTR portions; however, the anterior MTR portions cannot be reached safely. The operative risks of STA increase as the surgeon proceeds with resection of the anterior MTR portions. Anterior MTR structures can be removed using a combination of the supracerebellar and infraoccipital transtentorial approaches or two-stage resection.

Intrajugular balloon catheter reduces air embolism in vitro and in vivo

Background

Neurosurgical procedures requiring a sitting position may put the patient at risk of a potentially life-threatening air embolism. Transient manual jugular venous compression limits further air entry in this situation. This study presents an alternative technique aimed at reducing the risk of air embolism.

Methods

In an in vitro model, an intrajugular balloon catheter was inserted to demonstrate that this device prevents air embolism. In an in vivo study, this device was bilaterally placed into jugular vessels in pigs. Using an ultrasound technique, blood flow was monitored and jugular venous pressure was recorded before and during cuff inflation. Air was applied proximally to the inflated cuffs to test the hypothesis that this novel device blocks air passage.

Results

In vitro, the intrajugular balloon catheter reliably prevented further air entry (n=10). Additionally, accumulated air could be aspirated from an orifice of the catheter (n=10). In vivo, inflation of the catheter balloon completely obstructed venous blood flow (n=8). Bilateral inflation of the cuff significantly increased the proximal jugular venous pressure from 9.8 (2.4) mm Hg to 14.5 (2.5) mm Hg (n=8, P<0.05). Under conditions mimicking an air embolism, air passage across the inflated cuffs was prevented and 78 (20%) (n=6) of the air dose could be aspirated by the proximal orifice of the catheter.

Conclusions

These findings may serve as a starting point for the development of intrajugular balloon catheters designed to reduce the risk of air embolism in patients undergoing neurosurgery in a sitting position.

Major neurovascular complications of clavicle fracture surgery

Clavicle fracture fixation is becoming an increasingly common operation, with good clinical outcomes and a low rate of significant complications. However, there are several reports of rare but potentially life or limb threatening, neurovascular complications. Arterial injuries are usually pseudoaneurysms associated with prominent screws. These may be clinically silent for several years before presenting as subcritical upper limb ischaemia. Venous injuries are a result of tearing of the vessel wall by fracture manipulation, drills or implants. This produces intra-operative haemorrhage and potentially air embolism, which can be fatal if not rapidly recognized and managed. Brachial plexopathy is the result of traction on adherent plexus or impingement by fracture fragments or callus. It presents as severe arm pain and paralysis immediately postoperatively. Neurovascular injuries can be avoided by a combination of pre-operative planning, communication with anaesthetic staff and strategic surgical technique. The plane of the surgical exposure, release of the soft tissues, drill direction and depth and screw length are all important factors.

Venous air embolism (VAE) associated with stereotactic biopsies

BACKGROUND

Venous air embolism (VAE) is a serious potential complication of neurosurgical procedures. Stereotactic biopsies can also cause VAE; therefore, we evaluated VAE patients to call attention to the risk of VAE associated with stereotactic biopsies.

METHODS

In this report, symptomatic VAE was defined as paroxysmal coughing with associated symptoms. Air in the dural sinus, cortical vein and/or pterygoid plexus on postoperative computed tomography (CT) scans was considered to be a radiographic VAE.

RESULTS

Three patients developed symptomatic VAE following 36 stereotactic biopsies, and the incidence of symptomatic VAE was 8.3 % (3/36). There were five patients with evidence of radiographic VAE on postoperative CT scans, with an incidence of 13.8 % (5/36). A high angle of the head seemed to be associated with VAE, allowing air to flow into the central venous system.

CONCLUSIONS

The present report emphasizes that VAE should be recognized as an important adverse effect of stereotactic biopsies because VAE occasionally requires additional treatment and/or termination of surgery. Surgeons must be aware of the possibility of VAE, especially when it is necessary to position the patient's head at a high angle.

Patent foramen ovale closure prior to surgery in the sitting position

Previously, patent foramen ovale (PFO) was an absolute contraindication to surgery in the sitting position. We report two patients with PFO who underwent surgery in the sitting position after percutaneous PFO closure. To our knowledge this is the first report of this technique.

The infratentorial supracerebellar approach in surgery of lesions of the pineal region

Background:

Surgery of pineal region lesions is considered a challenging task, due to the particular relationship of lesions in this location with neural and vascular structures. Few series with a significant experience of dealing with these patients have been reported.

Methods:

We review our experience using infratentorial supracerebellar approach in the surgery of pineal region, regarding the extension of the removal, postoperative morbidity, and discussing details of the surgical technique. In all cases, a supracerebellar infratentorial approach was used in the semi sitting position.

Results:

A total of 32 patients were operated in the past 20 years (3 germinomas, 3 teratoma, 3 pineocitoma, 2 pineal tumor of intermediate differentiation, 6 pineoblastomas, 6 low grade astrocytoma, 2 glioblastoma, 2 metastasis, 1 ependymoma, 1 epidermoid tumor, 1 cavernoma, and 2 arachnoid cyst). Total removal was achieved in 15 cases and subtotal extensive removal in 7 patients. In the remaining cases, only partial removal was possible, due to the involved pathological types. There was no surgical mortality and no cases of cerebellar venous infarction. Morbidity consisted of transient ocular movement disturbance in 14 patients, transient ataxia in 3 patients, and 1 case of local cerebrospinal fluid (CSF) fistula with meningitis that required surgical treatment.

Conclusion:

Supracerebellar infratentorial is a safe approach to lesions in the pineal region, and total or extensive subtotal removal is possible in most cases, with acceptable morbidity.

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.

Stroke volume-directed administration of hydroxyethyl starch or Ringer's acetate in sitting position during craniotomy

BACKGROUND

To determine the volumes required for stable haemodynamics and possible effects on the coagulation, we studied stroke volume (SV)-directed administration of hydroxyethyl starch (HES 130 kDa/0.4) and Ringer's acetate (RAC) in neurosurgical patients operated on in a sitting position.

METHODS

Thirty craniotomy patients were randomised to receive either HES or RAC. Before positioning, SV, measured by arterial pressure waveform analysis, was maximised by boluses of fluid until SV did not increase more than 10%. SV was maintained by repeated administration of fluid. RAC 3 ml/kg/h was infused in both groups during surgery.

RESULTS

Comparable haemodynamics were achieved with the mean [standard deviation (SD)] cumulative doses of HES or RAC 271 (47) or 264 (50) ml (P = 0.699) before the sitting position. Mean (SD) doses of HES or RAC at 30 min after the positioning were 343 (94) or 450 (156) ml (P = 0.036), and at the end of surgery 464 (284) or 707 (425) ml, respectively (P = 0.087). The intraoperative fluid balance was more positive in the RAC than in the HES group [P = 0.044, 95% confidence interval (CI) -978 to -14]. Cardiac and stroke volume indexes [CI and stroke volume index (SVI)] increased in the HES group (P < 0.05) but not in the RAC group [non significant (N.S.)]. Neither coagulation profile nor blood loss differed between the groups.

CONCLUSION

Fluid filling with HES boluses resulted in a positive response in CI and SVI during the sitting position. The 34% smaller volume of HES than crystalloid and less positive fluid balance in the HES group might be important in craniotomy patients with decreased brain compliance.

Catastrophic venous air embolism during craniotomy in the supine position: the bleeding pattern as a warning sign?

Venous air embolism is a serious complication during a neurosurgical procedure. Here is a case of a massive venous air embolism causing cardiac arrest in the supine position surgery. Identifying the alternative inflation and collapse of the sinus and taking emergency measures to avoid catastrophic result are important.

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.

A streamlined protocol for the use of the semi-sitting position in neurosurgery: a report on 48 consecutive procedures

The semi-sitting position has lost favor among neurosurgeons partly due to unproven assumptions of increased complications. Many complications have been associated with this position; the most feared: venous air embolism and paradoxical air embolism. We report on this retrospective study of the outcome over 4 years of 48 neurosurgical patients operated on consecutively using a standardized protocol: 41 (85%) in the semi-sitting position, and seven (15%) in the prone position. Procedures included: tumor resection (34), posterior fossa decompression (12), cyst resection (1) and resection of arteriovenous malformation (1). Pre-operative workup was standardized. Vigilant intra-operative observation was done by an experienced neuroanesthetist. Pertinent data was extracted from surgical records. Of the 48 patients, 10 (20.8%) were found to have a patent foramen ovale (PFO) on trans-esophageal echocardiography. Of these, four (40%) patients underwent procedures in the semi-sitting position while six (60%) did not. A clinically significant venous air embolism (VAE) was detected during 2 of the 41 semi-sitting procedures (4.9%). Neither patient suffered any obvious sequelae. No other morbidity was encountered associated with surgical position. Our study suggests that a model similar to ours is effective in preventing major complications associated with the semi-sitting position. The semi-sitting position is a safe, practical position that should be considered in appropriate cases. The fear of dreadful complications seems unwarranted.

Hemodynamic monitoring in the intensive care unit

Patients in the intensive care unit are often critically ill with inadequate tissue perfusion and oxygenation. This inadequate delivery of substrates at the cellular level is a common definition of shock. Hemodynamic monitoring is the observation of cardiovascular physiology. The purpose of hemodynamic monitoring is to identify abnormal physiology and intervene before complications, including organ failure and death, occur. The most common types of invasive hemodynamic monitors are central venous catheters, pulmonary artery catheters, and arterial pulse-wave analysis. Ultrasonography is a noninvasive alternative being used in intensive care units for hemodynamic measurements and assessments.

The paramedian supracerebellar-transtentorial approach to the entire length of the mediobasal temporal region: an anatomical and clinical study

Object

The exploration of lesions in the mediobasal temporal region (MTR) has challenged generations of neurosurgeons to achieve an appropriate approach. To address this challenge, the extensive use of the paramedian supracerebellar-transtentorial (PST) approach to expose the entire length of the MTR, as well as the fusiform gyrus, was investigated.

Methods

The authors studied the microsurgical aspects of the PST approach in 20 cadaver brains and 5 cadaver heads under the operating microscope. They evaluated the features, advantages, difficulties, and limitations of the PST approach and refined the surgical technique. They then used the PST approach in 15 patients with large intrinsic MTR tumors (6 patients), tumor in the posterior fusiform gyrus with mediobasal temporal epilepsy (MTE) (1 patient), cavernous malformations in the posterior MTR including the fusiform gyrus (2 patients), or intractable MTE with hippocampal sclerosis (6 patients) from December 2007 to May 2010. Patients ranged in age from 11 to 63 years (mean 35.2 years), and in 9 patients (60%) the lesion was located on the left side.

Results

In all patients with neuroepithelial tumors or cavernous malformations, the lesions were completely and safely resected. In all patients with intractable MTE with hippocampal sclerosis, the anterior two-thirds of the parahippocampal gyrus and hippocampus, as well as the amygdala, were removed selectively through the PST approach. There was no surgical morbidity or mortality in this series. Three patients (20%) with high-grade neuroepithelial tumors underwent postoperative radiotherapy and chemotherapy but needed a second surgery for recurrence during the follow-up period. In all patients with MTE, antiepileptic medication could be decreased to a single drug at lower doses, and no seizure activity has occurred until this point.

Conclusions

The PST approach provides the surgeon precise anatomical orientation when exposing the entire length of the MTR, as well as the fusiform gyrus, for removing any lesion. This is a novel technique especially for removing tumors involving the entire MTR in a single session without damaging neighboring neural or vascular structures. This approach can also be a viable alternative for selective removal of the parahippocampal gyrus, hippocampus, and amygdala in patients with MTE due to hippocampal sclerosis.

[Questionnaire on the anaesthesiology treatment of patients subjected to posterior fossa neurosurgery]

OBJECTIVES

To find out, by means of a questionnaire, the procedures used by Spanish anaesthetists in peri-operative management of patients subjected to neurosurgery of the posterior cranial fossa.

MATERIAL AND METHODS

A closed-question type questionnaire was sent to Anaesthesiology Departments with a Neurosurgery Department on the participation of anaesthetists in the peri-operative treatment of patients subjected posterior fossa surgery.

RESULTS

The questionnaire was completed by 42 (57.5%) of the 73 national public hospitals with a Neurosurgery Department. The posterior fossa surgery was performed in the sitting position in 36 hospitals, although it was less frequently used than the lateral decubitus or prone decubitus position. There was little specific neurological monitoring, as well as little use of precordial and/or transcranial Doppler for detecting vascular air embolism. Nitrous oxide was used in less than 10% of the centres, and 15% avoided neuromuscular block when neurophysiological monitoring was used during the surgery. Cardiovascular problems were mentioned as being the most frequent in 29% of the centres, while in the post-operative period the most common complications were, cranial nerve déficit, airway oedema (23%), and post-operative vomiting (47%).

CONCLUSIONS

The results obtained from the questionnaire showed that the sitting position was less used than the prone position in posterior fossa surgery, and that neurophysiological monitoring is during surgery is hardly used.

Venous air embolism during semi-sitting craniotomy evokes thrombocytopenia

Venous air embolism activates platelets in vitro and can evoke platelet dysfunction in swine. We tested the hypothesis that venous air embolism during semi-sitting craniotomy induces thrombocytopenia in humans. We analysed the charts of 799 patients who had an elective craniotomy in the semi-sitting position between 1990 and June 2009. Venous air embolism occurred in 52 patients (6.5%) and was associated with a decrease in mean (SD) in platelet count from 270 (75) × 10⁹ l⁻¹ to 194 (62) × 10⁹ l⁻¹ (p < 0.001). In age-matched controls without venous air embolism mean (SD) platelet count did not change (254 (82) × 10⁹ l⁻¹ vs. 250 (97) × 10⁹ l⁻¹ (NS). While mean (SD) haematocrit fell slightly in both groups (venous air embolism: 0.40 (0.05) to 0.32 (0.04), p <0.001; no venous air embolism: 0.41 (0.04) to 0.35 (0.05), p < 0.001), normalising platelet count to haematocrit did not alter the results.

Venous air embolism: an unusual complication of atlantoaxial arthrodesis: case report

STUDY DESIGN

A unique case of a patient with intraoperative venous air embolism (VAE) during atlantoaxial arthrodesis has been discussed.

OBJECTIVE

To describe an uncommon complication of atlantoaxial arthrodesis, VAE.

SUMMARY OF BACKGROUND DATA

Although several techniques for atlantoaxial arthrodesis have proven effective, lateral mass or pedicle screw constructs have been shown to have superior strength with acceptable morbidity. Placement of lateral mass or pedicle screws into the C1 or C2 vertebrae requires consideration of relevant local anatomy, including vascular and nervous structures. We present a rare complication of surgery in this anatomic distribution, VAE. To the authors' knowledge, there has been no similar report described.

METHODS

A previously healthy 38-year-old man was found to have os odontoideum with atlantoaxial instability; arthrodesis was thus planned, with C1 lateral mass and C2 pedicle screws. Intraoperatively, during dissection of the C1-C2 joint capsule, the patient experienced a precipitous drop in blood pressure, end-tidal CO2, and oxygen saturation. Shortly thereafter, the patient was noted to be asystolic.

RESULT

With suspicion for air embolus, the surgical field was flooded with irrigant, the incision closed with haste, and the patient rolled to the supine position. Cardiopulmonary resuscitation was initiated with return of pulse within minutes. A transesophageal echocardiogram was performed approximately 15 minutes after the onset of suspected air embolus, revealing increased atrial pressures consistent with VAE. Following echocardiogram, the patient was returned to prone position for completion of arthrodesis. Remaining surgery and arousal were uneventful.

CONCLUSION

This is the first report of intraoperative VAE occurring with atlantoaxial arthrodesis. Enlarged venous anastomoses present at the atlantoaxial junction should be taken into consideration during surgical dissection, and the potential danger of VAE with atlantoaxial arthrodesis should be understood. With aggressive intraoperative treatment, this patient suffered no long-term complications.

The combination of semi-sitting position and intraoperative MRI--first report on feasibility

INTRODUCTION

Intraoperative MRI (iMRI) has been established as a routine imaging modality with a remarkable impact on specific neurosurgical procedures. The technological advancement continuously extends the spectrum of iMRI, leading to an increasing number of installations. Yet, procedures in which a semi-sitting position would be advantageous were beyond the reach of iMRI.

MATERIALS AND METHODS

We performed an iMRI-guided surgical procedure in a patient with a cystic lesion of the inferior parieto-occipital lobe while the patient was placed in a semi-sitting position, employing a mobile 0.15-T intraoperative MRI system. For that purpose, we adapted a standard OR table according to the needs of iMRI.

FINDINGS

Patient positioning could be accomplished easily. For intraoperative scanning, the OR table was tilted backwards so as to position the patient's head in the magnet's aperture. Obtained images were used for neuronavigated cyst evacuation via burr hole trephination after repositioning the OR table. Subsequent intraoperative imaging documented collapse of the cyst at the end of the procedure. There were no adverse effects resulting from the combination of semi-sitting position and iMRI guidance.

CONCLUSION

This report demonstrates for the first time that the combination of iMRI and the semi-sitting position is feasible and that this procedure bears specific benefits. Issues such as brain shift due to table tilting warrant further investigations in order to expand this technique to posterior fossa craniotomies.