Anaesthesia for Neurosurgery in the Sitting Position: A Practical Approach

Enabling Navigation and Augmented Reality in the Sitting Position in Posterior Fossa Surgery Using Intraoperative Ultrasound

Despite its broad use in cranial and spinal surgery, navigation support and microscope-based augmented reality (AR) have not yet found their way into posterior fossa surgery in the sitting position. While this position offers surgical benefits, navigation accuracy and thereof the use of navigation itself seems limited. Intraoperative ultrasound (iUS) can be applied at any time during surgery, delivering real-time images that can be used for accuracy verification and navigation updates. Within this study, its applicability in the sitting position was assessed. Data from 15 patients with lesions within the posterior fossa who underwent magnetic resonance imaging (MRI)-based navigation-supported surgery in the sitting position were retrospectively analyzed using the standard reference array and new rigid image-based MRI-iUS co-registration. The navigation accuracy was evaluated based on the spatial overlap of the outlined lesions and the distance between the corresponding landmarks in both data sets, respectively. Image-based co-registration significantly improved (p < 0.001) the spatial overlap of the outlined lesion (0.42 ± 0.30 vs. 0.65 ± 0.23) and significantly reduced (p < 0.001) the distance between the corresponding landmarks (8.69 ± 6.23 mm vs. 3.19 ± 2.73 mm), allowing for the sufficient use of navigation and AR support. Navigated iUS can therefore serve as an easy-to-use tool to enable navigation support for posterior fossa surgery in the sitting position.

Suspected systemic gas embolism associated with lung tissue perforation caused by a previously inserted chest drain in a dog

OBJECTIVE

To report a case of systemic gas embolism associated with removal of a chest drain perforating a lung lobe in a dog undergoing sternotomy under general anesthesia and intermittent positive pressure ventilation.

CASE SUMMARY

An 8-year-old Cocker Spaniel underwent an exploratory thoracotomy via median sternotomy for surgical management of pyothorax that was treated conservatively for 7 days prior to referral following bilateral chest drain placement. The surgical procedure consisted of a subphrenic mediastinectomy and pericardiectomy. During surgery, it became apparent that the right drain was perforating the right middle lung lobe. Sudden desaturation and rapid hemodynamic deterioration occurred after the drain was removed. A systemic gas embolism was suspected on the basis of clinical signs and results of an arterial blood gas analysis, and immediate supportive treatment was started with an adequate response. Once the surgical procedure was completed, a clear "mill wheel" sound was audible on cardiac auscultation and point-of-care cardiac ultrasound confirmed the presence of gas bubbles in the cardiac chambers. The dog recovered from anesthesia and was managed in the intensive care unit where arterial blood gas analyses were nearly normal and the dog made a full recovery.

NEW OR UNIQUE INFORMATION PROVIDED

In people, there are reports of fatal air embolism related to the use of chest drains. To our knowledge, this is the first case report in dogs of a systemic gas embolism during open-chest surgery caused by a chest drain perforating a lung lobe. Immediate recognition and aggressive treatment of this life-threatening condition should be provided in order to achieve a favorable outcome.

Posterior Petrous Meningiomas: Surgical Classification and Postoperative Outcomes in a Case Series of 130 Patients Operated via the Retrosigmoid Approach

OBJECTIVE

A standardized definition and classification of primary posterior petrous meningiomas (PPMs) is lacking, with consequent challenges in comparing different case series. This study aimed to provide an anatomical description and classification of PPMs analyzing a homogeneous series of patients operated via the retrosigmoid approach.

METHODS

PPMs originate laterally to the petro-occipital fissure within the venous ring composed of the superior petrosal, sigmoid, inferior petrosal, and cavernous sinuses. We proposed a classification based on tumor site of origin, direction of growth relative to the internal acoustic meatus, and cranial nerves' displacement. Four types of PPMs were defined: retromeatal (type A), meatal (type B), premeatal (type C), and broad-based (type D). We performed a retrospective analysis of 130 consecutive patients with PPMs who underwent surgery as first-line treatment.

RESULTS

The PPM classification predicted clinical presentation, postoperative morbidity, and resection rates. Headache, hydrocephalus, and cerebellar deficits were more common in type A (59.0%, 37.7%, 49.2%) and type D (66.7%, 66.7%, 33.3%). Hypoacusia/anacusia was more common in type B (87.5%), while trigeminal hypoesthesia/anesthesia was more common in type C (85.0%). After surgery, patients with type A and D PPMs were at higher risk to develop cerebellar deficits (11.5%-22.2%), whereas patients with type B and C PPMs presented with hypoacusia/anacusia (12.5%) and trigeminal deficits (10.0%), respectively. The near-total resection rate was higher in type A (91.8%), followed by types B (82.5%), C (80.0%), and D (77.8%) PPMs.

CONCLUSIONS

The PPM surgical classification has an operative and prognostic relevance. In expert hands, the retrosigmoid approach represents a safe and effective approach to remove PPMs.

Intraoperative Dental Injury in a Neurosurgical Patient: Concerns for the Anesthesiologist

Anesthesia-related oropharyngeal injuries are known to occur. Risk factors for intraoperative dental injuries include difficult intubation, use of transesophageal echocardiography (TEE) probe, motor-evoked potential (MEP) monitoring, poor dental hygiene, etc. Our patient was a case of a thalamic cavernoma who underwent craniotomy in a sitting position with the neck flexed along with MEP and TEE monitoring. At the end of the surgery, the lower three incisors were found to be subluxated. The subluxated teeth were stabilized using a 2-0 Ethilon suture in the operation room. Immediate dental consultation was sought postoperatively. Sitting position surgeries with associated neck flexion, simultaneous, advanced monitoring techniques like TEE and MEP, poor dental condition, and the use of hard bite blocks can predispose patients to dental injury. Preoperative dental evaluation and explanation of neuromonitoring-associated injuries can be beneficial.

[Sitting position in neurosurgery: realizing the risks]

The author discusses potential intraoperative complications following neurosurgical interventions in sitting position: venous air embolism and paradoxical air embolism, postural hypotension, pneumocephalus, cervical flexion neuropathy, positional damage to peripheral nerves and others. Naturally, prevention of these complications is also considered, and the most effective approach is surgery in lying position.

Pineal region tumours in the sitting position: how I do it

Background

Pineal region tumours remain challenging neurosurgical pathologies.

Methods

Detailed anatomical knowledge of the posterior incisural space and its variations is critical. An opaque arachnoidal membrane seals the internal cerebral and basal veins, leading to thalamic, basal ganglia, mesencephalic/pontine infarctions if injured. Medium-size tumours can be removed en-bloc with all traction/manipulation applied on the tumour side, virtually without contact of ependymal surfaces of the pulvinars or third ventricle. Sacrifice of the cerebello-mesencephalic fissure vein may be required.

Conclusions

The sitting position offers superior anatomical orientation and remains safe with experienced teams. Meticulous microsurgical techniques and detailed anatomical knowledge are likely to secure safe outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00701-021-04821-3.

Outcomes in single-level posterior cervical spine surgeries performed in the sitting and prone positions

OBJECTIVE

The sitting or semisitting position in neurosurgery allows for several technical advantages, including improved visualization of the surgical field. However, it has also been associated with an increased risk of venous air embolisms and positioning-related complications that limit its commonplace adoption. The authors report a large, single-center series of cervical spine procedures performed with patients in the sitting or prone position in order to assess the perceived risk of intraoperative and postoperative complications associated with the sitting position.

METHODS

Noninstrumented, single-level posterior cervical spine procedures performed with patients in the sitting/semisitting or prone position from 2000 to 2016 at a single institution were reviewed. Institutional abstraction tools (DataMart and Chart Plus) were used to collect data from the medical records. The two positions were compared with regard to preoperative factors, intraoperative variables, and postoperative outcomes. Multivariable logistic regression models were fitted for 30-day readmission, 30-day return to the operating room, and complication rates.

RESULTS

A total of 750 patients (sitting, n = 480; prone, n = 270) were analyzed. The median age was 53 years for those who underwent surgery in the prone position and 50 years for those who underwent surgery in the sitting position (IQRs 45-62 years and 43-60 years, respectively), and 35% of the patients were female. Sitting cases were associated with significantly longer anesthetic times (221 minutes [range 199-252 minutes] vs 205 minutes [range 179-254 minutes]) and operative times (126 minutes [range 101-163 minutes] vs 149 minutes [120-181 minutes]). Cardiorespiratory events in the postanesthesia care unit (PACU) were comparable between the two groups, with the exception of episodes of apnea (2.6% vs 0.6%, p = 0.041) and hypoventilation (4.4% vs 0.8%, p < 0.003), which were more frequent in the prone-position cohort. On multivariable analysis, the effect of the sitting versus the prone position was not significant for 30-day readmission (OR 0.77, 95% CI 0.34-1.71, p = 0.52) or reoperation (OR 0.71, 95% CI 0.31-1.60, p = 0.40). The sitting position was associated with lower odds of developing any complication (OR 0.31, 95% CI 0.16-0.62, p < 0.001).

CONCLUSIONS

Based on the intraoperative and postoperative complications chosen in this study, the sitting position confers a similar safety profile to the prone position. This can be explained by a more anatomic positioning accounting for reduced temporary neurological deficits and reduced PACU-associated hypoventilation noted in this series. Nevertheless, the findings may also reflect institutional familiarity, experience, and mastery of this position type, and outcomes may not reflect practices in general.

Estimation of the head elevation angle that causes clinically important venous air embolism in a semi-sitting position for neurosurgery: a retrospective observational study

Introduction:

The benefits of a sitting position for neurosurgery involving the posterior fossa remain controversial. The main concern is the risk of venous air embolism (VAE). A recent study showed that the rate of VAE was higher when the head was elevated to 45° than when it was elevated to 30°. However, the degree of head elevation that causes clinically important VAE is unclear. The purpose of this study was to estimate the head elevation angle at which the probability of VAE is 50% by using EtCO₂ monitoring to detect of VAE.

Methods:

The anesthesia records of 23 patients who underwent neurosurgery in a sitting position were reviewed retrospectively. Intraoperative ventilation was set to maintain EtCO₂ at approximately 38-42 mmHg. The head elevation angle in each case was determined from a photograph taken by the anesthesiologist or brain surgeon. Nineteen of the 23 cases had photographs available that contained a horizontal reference in the background. Seven cases were treated as VAE during the operation. Six of these cases met the criteria for VAE in this study. Data analysis was performed on a total of 18 patients. The angle between the line connecting the hip joint and the shoulder joint and the horizontal reference was obtained by ImageJ software. Logistic regression was performed using the Python programming language to determine the head elevation angle at which the probability of air embolism was 50%.

Results:

The decision boundary in the logistic regression was 35.7°. This head elevation angle was the boundary where the probability of VAE was 50%.

Conclusion:

The angle of head elevation that caused clinically important VAE was estimated to be 35.7°.

Effects of Crystalloid Preloading (20 ml/kg) on Hemodynamics in Relation to Postural Changes in Patients Undergoing Neurosurgical Procedures in Sitting Position

Background:

Hemodynamic disturbances are common during positioning the patients from supine to sitting for neurosurgical procedures. The reported incidence of hypotension varies from 5% to 32%. The aim of the study was to study the effect of crystalloid preloading on hemodynamic parameters during positioning the patient from supine to sitting position.

Materials and Methods:

In this prospective observational trial, 20 patients were enrolled. Two patients had a patent foramen ovale on transesophageal echocardiography and were excluded from the study. All the patients received 20 ml/kg of crystalloid (Ringer's lactate) before initiation of positioning. Physiological hemodynamic parameters such as heart rate, mean arterial pressure, central venous pressure, cardiac output (CO), stroke volume variation (SVV), cardiac index (CI), stroke volume (SV), and maximum and minimum inferior vena caval diameter (IVCD) were recorded after induction, during positioning at 30°, 60° inclination of the operating table and after the final sitting position.

Results:

Hemodynamic parameters were well maintained during positioning of the patients from supine to sitting position. Crystalloid preloading prevented the hypotension during positioning. There were no significant changes in hemodynamic parameters such as CO, SVR, SVV, CI, and SV. We did not find any correlation with changes in IVCD with changes in CO.

Conclusion:

A volume of 20 ml/kg of crystalloid preloading before positioning the patient from supine to sitting position maintains the hemodynamic stability and avoids the vasopressor requirement.

Neurosurgery in the Sitting Position: A Case Series

Prospective data was collected on 58 patients having neurosurgery in the sitting position in one institution. The incidence of venous air embolism was 43% (25/58), of which the majority were small or moderate in size. There were no episodes of paradoxical air embolism. The incidence of other intraoperative and postoperative complications was low. There was no mortality or serious morbidity. With a proper understanding of the pathophysiology of venous air embolism and the use of sensitive monitoring, anaesthesia for sitting position neurosurgery can be provided safely.

Predictors of ventricular tension pneumocephalus after posterior fossa surgery in the sitting position

BACKGROUND

Ventricular pneumocephalus is a rare but potentially life-threatening complication of cranial surgery in the sitting position.

OBJECTIVE

The objective of the study is to assess the incidence and risk factors of postoperative ventricular pneumocephalus.

METHODS

We performed a retrospective chart review of 307 consecutive patients (147 men, 160 women) treated at our institution by intracranial surgery in the sitting position from January 2010 to October 2014. Ventricular air entrapment with lack of arousal or neurologic deterioration requiring external ventriculostomy (EVD) was defined as ventricular tension pneumocephalus (VTP). Demographic variables were recorded along with radiological and clinical data. The occurrence of pneumocephalus was correlated with patient-related and surgical variables.

RESULTS

VTP was observed in 12 cases (3.9%). These patients had higher intraventricular air volumes (48.5 cm³ (CI 95% [29.06-67.86])) compared to asymptomatic patients (7.4 cm³ (CI 95% [5.43-9.48])). Opening of the fourth ventricle was the most potent predictor of VTP (OR = 34.7, CI 95% [4.4-273.5], p = 0.001). In patients undergoing no additional treatment for pneumocephalus, ventricular air volume declined to an average of 41.7% of the initial postoperative volume on postoperative day 3.

CONCLUSIONS

Entrapment of intracranial and particularly ventricular air requiring emergent EVD occurred in 3.9% cases of intracranial surgery in the sitting position. Especially the opening of the fourth ventricle was associated with the development of VTP, which should warrant particularly diligent postoperative observation of these patients. In cases without neurological symptoms, the rate of spontaneous air resorption is sufficiently high to warrant expectant management.

Mass Transport: Circulatory System with Emphasis on Nonendothermic Species

Mass transport can be generally defined as movement of material matter. The circulatory system then is a biological example given its role in the movement in transporting gases, nutrients, wastes, and chemical signals. Comparative physiology has a long history of providing new insights and advancing our understanding of circulatory mass transport across a wide array of circulatory systems. Here we focus on circulatory function of nonmodel species. Invertebrates possess diverse convection systems; that at the most complex generate pressures and perform at a level comparable to vertebrates. Many invertebrates actively modulate cardiovascular function using neuronal, neurohormonal, and skeletal muscle activity. In vertebrates, our understanding of cardiac morphology, cardiomyocyte function, and contractile protein regulation by Ca2+ highlights a high degree of conservation, but differences between species exist and are coupled to variable environments and body temperatures. Key regulators of vertebrate cardiac function and systemic blood pressure include the autonomic nervous system, hormones, and ventricular filling. Further chemical factors regulating cardiovascular function include adenosine, natriuretic peptides, arginine vasotocin, endothelin 1, bradykinin, histamine, nitric oxide, and hydrogen sulfide, to name but a few. Diverse vascular morphologies and the regulation of blood flow in the coronary and cerebral circulations are also apparent in nonmammalian species. Dynamic adjustments of cardiovascular function are associated with exercise on land, flying at high altitude, prolonged dives by marine mammals, and unique morphology, such as the giraffe. Future studies should address limits of gas exchange and convective transport, the evolution of high arterial pressure across diverse taxa, and the importance of the cardiovascular system adaptations to extreme environments. © 2017 American Physiological Society. Compr Physiol 7:17-66, 2017.

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.

Coagulopathy following venous air embolism: a disastrous consequence -a case report-

Venous air embolism (VAE) is a life-threatening complication of some surgical procedures. Though occurrence of VAE is frequent during neurosurgical procedures, coagulopathy following VAE has not previously been reported. Coagulation abnormalities are more commonly reported associated with fat or amniotic fluid embolism, but rarely with VAE. We present a case of massive VAE in sitting position leading to fatal coagulopathy even after successful resuscitation following the event. Coagulation abnormalities and bleeding can produce catastrophic consequences in neurosurgical patients. This report emphasizes the possibility of this potentially fatal complication in patients who have sustained a massive VAE.

The sitting position during neurosurgical procedures does not influence serum biomarkers of pulmonary parenchymal injury

Background

The sitting position during neurosurgical operations predisposes to air penetration through veins and the movement of the air through the pulmonary circulation. Contact of an air bubble with the endothelium can lead to acute lung injury. The presence of specific pulmonary proteins in the plasma such as surfactant protein D (SP-D) and Clara cell protein (CC16) is a biomarker of damaging processes at the air-blood barrier. The aim of our study was to examine the hypothesis that the level of investigated pulmonary biomarkers in plasma is higher in patients operated on in the sitting position.

Methods

The study included patients undergoing planned neurosurgical operations, who were divided into two groups: the sitting group (40 patients, operated on in the sitting position) and the supine group (24 patients, operated in the supine position). After the operation blood samples were drawn, centrifuged, frozen and stored until analyses were conducted. The determination of the SP-D and CC16 levels was performed using an ELISA test. Air embolism (VAE) was defined as a sudden drop in etCO₂ of more than 2 mmHg and the presence of air bubbles in the aspirated blood from the central cannula. In all patients, the number of hospitalization days in the postoperative period was calculated.

Results

There were no differences in the average levels of SP-D between the groups (the mean in the sitting group was 95.56 ng/mL and the mean in the supine group was 101.21 ng/mL). The average levels of CC16 were similar in both groups as well (6.56ng/mL in the sitting group and 6.79ng/mL in the supine group). There was a statistically significant positive correlation between SP-D and CC16 values in both groups. VAE was diagnosed clinically in 12.5% of cases in the sitting group without a significant increase in SP-D and CC16 levels. On average, patients in both groups were discharged from the hospital within 9 days of surgery.

Conclusion

The sitting position and intraoperative VAE during neurosurgical procedures do not affect the concentration of plasma biomarkers of pulmonary parenchymal injury such as SP-D and CC16.

Micropuncture needles combined with ultrasound guidance for unusual central venous cannulation: desperate times call for desperate measures--a new trick for old anesthesiologists

Central vascular access can be a very challenging task in patients with skeletal deformities such as ankylosing spondylitis, kyphosis, and chin-on-chest deformity. The use of traditional methods of accessing the central venous circulation in these patients can require multiple attempts and may lead to significant complications such as bleeding, pneumothorax, and vascular injury. Ultrasound-guided central venous access has become a very common procedure in the United States and Europe; its efficacy and safety have been demonstrated, and together with the use of micropuncture needles, the technique can facilitate central venous access in complicated cases.

[Surgery in the sitting position : anesthesiological considerations]

Surgical interventions in the sitting position are intended to optimize surgical conditions by reducing bleeding in the operation field and improving the surgical approach. There are, however, some potentially life-threatening risks associated with surgery in the sitting position. Of these risks, air embolism is one of the most serious complications and should be detected immediately in order to initiate specific countermeasures. In addition to standard monitoring procedures, transthoracic Doppler ultrasound and transesophageal echocardiography are valuable methods used to detect the presence of air in the vasculature. If an air embolism becomes apparent, further targeted measures are needed to prevent or aggressively treat the progression of potentially life-threatening consequences.

[Problem/case-based learning compared to lectures for acquiring knowledge of air embolism in continuing medical education]

OBJECTIVE

The efficacy of continuing medical education in anesthesiology has been examined very little. This study compared the efficacy of a lecture on air embolism to that of a class that used a problem/case-based learning approach.

MATERIAL AND METHODS

Prospective, randomized study enrolling 52 experienced anesthesiologists participating in a professional development course. Twenty-six anesthesiologists attended a lecture on air embolism in anesthesia and 25 attended a problem-based class. The objectives were the same for both groups and had been defined previously. The participants' knowledge was evaluated before and after the instruction with tests based on 2 cases dealing with the same knowledge areas: risk factors and symptoms, diagnosis, monitoring, and treatment.

RESULTS

No significant between-group differences were found for any of the knowledge areas before or after the classes. After instruction, participants who listened to the lecture improved their scores for knowledge of monitoring (P = .03) and treatment (P = .001). Participants in the problem-based learning group also improved their scores for knowledge of treatment (P = .003).

CONCLUSIONS

No between-group differences in participants' knowledge outcomes were detected; improvements were minimal. The study design allowed the knowledge acquired to be evaluated objectively.

Positive End-expiratory Pressure Reduces Pneumocephalus in Spinal Intradural Tumor Surgery

We tested the hypothesis that 5 cm H2O of positive end-expiratory pressure (PEEP) reduces the incidence of pneumocephalus in patients who undergo spinal intradural tumor surgery. Fifty-three ASA I to III patients who underwent thoracolumbar intradural tumor surgery between the years 2003 and 2006 were included in this study. All patients received propofol, fentanyl, and cisatracurium for induction of the anesthesia. Maintenance was provided by propofol infusion and, oxygen (50%) and air (50%). Group I (n=28) did not receive PEEP whereas group II (n=25) received PEEP as 5 cm H2O. Cranial computerized tomography was taken at 8 hours after the surgery and cases were evaluated for pneumocephalus using BAB Bs200ProP Image System software. Pneumocephalus areas between 0.03 and 4.24 cm2 were observed in 9 patients, 8 in group I and 1 patient in group II at the 8th postoperative hour, at various localizations. There were no neurologic findings in other patients except for 2 patients in group I who presented with headache and mental status change. Although the cerebrospinal fluid leakage is minimal, N2O is not used and the patients are well hydrated, pneumocephalus with neurologic deficits may occur in patients undergoing microsurgical spinal intradural tumor surgery in prone position. In our study, we showed that using 5 cm H2O PEEP perioperatively reduced the risk of pneumocephalus. However, more cases must be studied to support this hypothesis.

Alternative explanations to the differences of femoral and brachial saline contrast injections for echocardiographic detection of patent foramen ovale

Patent foramen ovale (PFO) of the interatrial septum is a cardiac foetal remnant, which frequent persistence in adulthood has important implications in a variety of clinical conditions. Echographic diagnosis of PFO is based on detection of interatrial shunt by means of contrast microbubbles identification after venous injection of a first-generation echographic contrast agent. Current recommendations propose venous femoral injection of contrast for enhanced echographic detection of PFO instead of venous brachial administration, as femoral injection has been shown to have higher sensitivity for PFO detection. Inferior vena cava inflow directed toward interatrial septum has been considered the explanation for increased sensitivity of femoral delivery of contrast. In the present paper, it is hypothesised that the main determinants of these differences between injection sites are technical factors related to right atrial contrast opacification and proper transient right atrial pressure rise, rather than intraatrial flow streaming. Effects of inferior vena cava inflow stream, although significant during foetal life, would be negligible after birth. Rationale and evidence, basis for further research, and practical implications leading to a simpler and safer routine technique for echographic detection of PFO are presented and discussed.

The role of eustachian valve and patent foramen ovale in sudden death

Sudden unexpected cardiac death is the leading cause of death in industrialized countries. Patent foramen ovale and eustachian valve are two of cardiac diseases and they may be associated with clinical disorders as embolism, stroke, plathypnea-orthodeoxia syndrome, carcinoid heart disease, atrial flutter and endocarditis. The literature for the roles of patent foramen ovale and eustachian valve in the causes of sudden deaths are reviewed.

Precordial Doppler Probe Placement for Optimal Detection of Venous Air Embolism During Craniotomy

Verification of appropriate precordial Doppler probe position over the anterior chest wall is crucial for early detection of venous air embolism. We studied responses to normal saline (NS) and carbon dioxide (CO2) test injections at various probe locations during elective craniotomy. All patients received four IV injections (10 mL of NS and 1 mL of CO2 via central and peripheral venous catheters). Doppler sounds were simultaneously recorded with two separate probes. In Group A, probes were placed in left and right parasternal positions. In Group B, the left probe was intentionally malpositioned as far laterally over the left precordium as was compatible with an audible signal. In Group A (n = 23), a left parasternal Doppler signal was easily obtainable in 23 of 23 patients, versus 18 of 23 patients for the right parasternal probe (P < 0.05). In Group B (n = 17), central CO2 injection yielded a positive right parasternal response rate of 88% compared with 29% over the far left precordium (P < 0.015), where central NS injections yielded a 76% response rate (P < 0.015 versus central CO2 injection). Left parasternal placement is at least as sensitive to clinical venous air embolism events as right parasternal placement. Peripheral saline injection represents a viable alternative (83% response rate). Vigorous central injection of 10 mL of NS however, risks false positive verification of left lateral precordial probe placement.