Intracardiac transvenous echocardiography is superior to both precordial Doppler and transesophageal echocardiography techniques for detecting venous air embolism and catheter-guided air aspiration

Dynamic Lateral Semisitting Position for Supracerebellar Approaches: Technical Note and Case Series

BACKGROUND

It has always been a matter of debate which position is ideal for the supracerebellar approach. The risk of venous air embolism (VAE) is the major deterrent for surgeons and anesthesiologists, despite the fact that sitting and semisitting positions are commonly used in these operations.

OBJECTIVE

To demonstrate a reduction on the risk of VAE and tension pneumocephalus throughout the operation period while taking advantages of the semisitting position.

METHODS

In this study, 11 patients with various diagnoses were operated in our department using the supracerebellar approach in the dynamic lateral semisitting position. We used end-tidal carbon dioxide and arterial blood pressure monitoring to detect venous air embolism.

RESULTS

None of the patients had clinically significant VAE in this study. No tension pneumocephalus or major complications were observed. All the patients were extubated safely after surgery.

CONCLUSION

The ideal position, with which to apply the supracerebellar approach, is still a challenge. In our study, we presented an alternative position that has advantages of the sitting and semisitting positions with a lower risk of venous air embolism.

Nontrombotic Pulmonary Embolism: Different Etiology, Same Significant Consequences

Nontrombotic pulmonary embolism represents the embolization of different types of materials (cells, organisms, gas, foreign material) into pulmonary circulation. The disease is uncommon, and clinical presentation together with laboratory findings are nonspecific. Its pathology is usually misdiagnosed based on imaging findings as pulmonary thromboembolism, but the correct diagnosis is essential because different therapeutic approaches are required. In this context, knowledge of the risk factors associated with nontrombotic pulmonary embolism and specific clinical symptoms is fundamental. Our objective was to discuss the specific features of the most common etiologies of nontrombotic pulmonary embolism, gas, fat, amniotic fluid, sepsis and tumors, to provide assistance for a rapid and correct diagnosis. Because the most common etiologies are iatrogenic, knowledge of the risk factors could be an important tool for prevention or rapid treatment if the disease develops during different procedures. The diagnosis of nontrombotic pulmonary embolisms represent a laborious challenge, and endeavors should be made to prevent development and increase awareness of this disease.

Before the Knife: A Detailed Step-by-Step Description of an Optimized Semi-Sitting Position in Posterior Fossa Surgery

BACKGROUND

In an ample armamentarium in neurosurgery, the semi-sitting position has produced debate regarding its benefits and risks. Although the position is apparently intuitive, many have abandoned its use since its initial inception, because of reported complexity and potential complications, leading to impracticality. However, through standardization, it has been shown not only to be safe but to carry with it many advantages, including less risk of secondary neurovascular injuries and better visualization of the surgical field. As with any surgical technical nuance, the semi-sitting position has advantages and disadvantages that must be weighed before the decision is made to adopt it or not, not only in a case-by-case scenario but also from a departmental standpoint. As we attempt to show, the advantages from a standardized approach for the semi-sitting position in experienced institutions may be more than sufficient to significantly outweigh the disadvantages, making it the preferable option for most, although not all, posterior fossa surgical interventions.

METHODS

In the present study, we aim to elaborate a straightforward narrative of the steps before incision, in an attempt to simplify the complexity of the position, alleviating its disadvantages and exponentially concentrating on its benefits. In nearly 100 steps, we carefully describe the points that culminate with the skin incision, initiating the intraoperative part of the procedure. Each step, therefore, is detailed in full, not in an effort to create a strict manual of the semi-sitting position but rather to facilitate understanding and put the technique into effect in a real-life scenario, thus simplifying what some depict as complex and time consuming.

CONCLUSIONS

Although several of the steps described are also relevant and integral parts of other surgical positioning, we intend to create a protocol, in a stepwise fashion, to allow facilitated following, to be easily implemented in departments with different levels of experience. The steps comprise nursing care through to electrophysiologic and anesthesiologic approaches, along with neurosurgical cooperation, making it a team approach, not only to avoid position-related complications but also to optimize preoperative standardization, constructing a safe, efficient, and patient-centered scenario, to set the best possible stage for the next step: the intraoperative part of the intervention.

Transesophageal Echocardiography-Guided Aspiration of Venous Air Embolism During Liver Transplantation: A Case Report

Transesophageal echocardiography can be useful not only in diagnosing venous air embolism but also in guiding aspiration of air from the pulmonary artery. A 59-year-old man with a history of cirrhosis underwent combined kidney and liver transplantations. He developed acute hypotension after the native liver was removed due to a massive venous air embolism via a retained transjugular intrahepatic portosystemic shunt catheter. Transesophageal echocardiography revealed air in the pulmonary artery resulting in outflow obstruction. Under echocardiographic guidance, the pulmonary arterial catheter was withdrawn to the air pocket and aspirated, resulting in improved hemodynamics and successful completion of transplantations.

The semisitting position: analysis of the risks and surgical outcomes in a contemporary series of 425 adult patients undergoing cranial surgery

OBJECTIVE

The objective of this study was to analyze the incidence of the primary complications related to positioning or surgery and their impact on neurological outcome in a consecutive series of patients undergoing elective surgery in the semisitting position.

METHODS

The authors prospectively collected and retrospectively analyzed data from adult patients undergoing elective surgery in the semisitting position for a cranial disease. Patients were managed perioperatively according to a standard institutional protocol, a standardized stepwise positioning, and surgical maneuvers to decrease the risk of venous air embolism (VAE) and other complications. Intraoperative and postoperative complications were recorded. Neurointensive care unit (NICU) length of stay (LOS) and hospital LOS were the intermediate endpoints. Neurological outcome was the primary endpoint as determined by the modified Rankin scale (mRS) score at 6 months after surgery.

RESULTS

Four hundred twenty-five patients were included in the analysis. VAE occurred in 90 cases (21%) and it made no significant statistical difference in NICU LOS, hospital LOS, and neurological outcome. No complication was directly related to the semisitting position, although 46 patients (11%) experienced at least 1 surgery-related complication and NICU LOS and hospital LOS were significantly prolonged in this group. Neurological outcome was significantly worse for patients with complications (p < 0.0001).

CONCLUSIONS

Even in the presence of intraoperative VAE, the semisitting position was not related to an increased risk of postoperative deficits and can represent a safe additional option for the benefit of specific surgical and patient needs.

Evaluation of Arteriovenous Shunting in Patients With End-Stage Liver Disease: Potential Role of Early Right Heart Catheterization

BACKGROUND

In patients with end-stage liver disease (ESLD), the presence of hypoxemia suggests the presence of intrapulmonary oxygen shunting (IPS) and/or transatrial shunting. Early identification of each is imperative to avoid potentially fatal peritransplantation complications and appropriately prioritize patients for liver transplantation (LT). The aim of this work was to compare the sensitivity of transthoracic echocardiography (TTE) and right heart catheterization (RHC) with intracardiac echocardiography (ICE) for identifying the etiologies of resting hypoxemia in patients with ESLD being evaluated for LT.

METHODS

Records of 28 patients with ESLD and resting hypoxemia who underwent TTE with bubble study and RHC/ICE were reviewed. Patients with a patent foramen ovale (PFO) were compared with non-PFO patients to determine diagnostic accuracy of TTE with bubble study versus RHC/ICE.

RESULTS

TTE with bubble study diagnosed PFO, IPS, and pulmonary hypertension (PH), respectively, with sensitivities of 46%, 41%, and 25% and specificities of 46%, 45%, and 80% compared with RHC/ICE. Although IPS detected by RHC/ICE was more common in patients without a PFO (92%), 5 patients with a PFO (33%) also had IPS (P = .002). Isolated PH was detected exclusively in patients with a PFO (5/15; 33%).

CONCLUSIONS

TTE with bubble study is neither sensitive nor specific to exclude a PFO in patients with ESLD. RHC/ICE is a safe and accurate diagnostic/interventional modality in this group of patients and is useful to diagnose other comorbidities, such as IPS and PH, that may coexist and contribute to resting hypoxemia.

Will transoesophageal echocardiography become a standard tool for anesthetists to assess haemodynamic status during non-cardiac surgeries? Case report and literature review

A 53-year-old male, with no history of cardiovascular diseases, underwent elective extended right hemihepatectomy for large metastatic tumor. Approximately 2 hours after the start of procedure sudden onset of severe hypotension associated with profound desaturation and significant fall in end-tidal carbon dioxide pressure was noted. Transoesophageal echocardiography was performed and massive air embolism was confirmed. Patient was turned into Trendelenburg position, inspired oxygen was increased to 100% and positive end-expiratiory pressure turned up to 10 cm H₂0. Patient was further resuscitated with iv fluids, blood products and vasopressors under surveillance of transoesophageal echocardiography. In this report we present a case in which intraoperative use of transoesophageal echocardiography by trained anaesthetist helped to immediately identify the cause of sudden hypotension and hypoxaemia. Transoesophageal echocardiographywas also a valuable tool for direct monitoring of efficacy of instituted treatment.

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.

Venous air embolism induces both platelet dysfunction and thrombocytopenia

BACKGROUND

In vitro, air bubbles can induce platelet activation and platelet to air bubble binding. We therefore tested in vivo the hypothesis that venous air embolism (VAE) induces (1) platelet dysfunction and (2) thrombocytopenia.

METHODS

Adult swine (60.8+/-3.9 kg; n=8) were anaesthetized, mechanically ventilated, and placed in a semi-upright position. Air boli (0.5-80 ml) were injected randomly via an ear vein, and arterial blood was sampled after cumulative air dosages of 0, 80, 160, and 240 ml. Coagulation was assessed by impedance aggregometry, rotational thrombelastometry, whole blood count, plasmatic coagulation variables, and fibrinogen, d-dimer, protein C, and antithrombin plasma concentrations, respectively.

RESULTS

VAE induced a 47% decrease in platelet count (303 vs. 160 nl(-1); P<0.001) over the dose range assessed, with haematocrit being unaltered. Furthermore, VAE-impaired platelet aggregation induced by adenosine diphosphate, arachidonic acid, collagen, and the thromboxan analogue U46619 over the dose range assessed independent of thrombocytopenia. (P<0.05 vs. baseline). In contrast, rotational thrombelastometry alone was quite insensitive in detecting VAE-induced coagulation changes, showing only at near lethal air dosages a prolonged clot formation time following activation with tissue factor, contact activator, and during spontaneous coagulation (P<0.05 vs. baseline).

CONCLUSIONS

VAE induces both a dose-dependent decrease in platelet count and a marked decrease in platelet aggregation, independent of thrombocytopenia (P<0.05 vs. baseline).