Extravascular Lung Water Measured Using Single Transpulmonary Thermodilution Reflects Perioperative Pulmonary Edema Induced by Esophagectomy

MONITORING OF PULMONARY EDEMA USING ULTRASOUND RADIOFREQUENCY SIGNAL

ABSTRACT

Objectives: Excessive accumulation of extravascular lung water impairs respiratory gas exchange and results in respiratory distress. Real-time radiofrequency signals of ultrasound can continuously and quantitatively monitor excessive lung water. This study aims to evaluate the availability of continuous real-time quantitative pulmonary edema monitoring using ultrasound radiofrequency signals and compare it with Pa o2 (partial pressure of arterial oxygen)/F io2 (fraction of inspired oxygen) (PF) ratio, conventional lung ultrasound, and the Hounsfield unit of chest computed tomography. Methods: Male Yorkshire pigs (40.5 ± 0.5 kg) were anesthetized and mechanically ventilated. A balanced crystalloid was administered to induce hydrostatic pulmonary edema. Three different infusion rates of 2, 4, and 6 mL/kg per minute were tested to determine the infusion rate for the appropriate swine model. The chest computed tomography and ultrasonography with radiofrequency signals were taken every 5 min during the full inspiration. The ultrasonography scans with radiofrequency signals were measured at the intercostal space where the line crossing the two armpits and the right anterior axillary line intersected. Results: The infusion rate of fluid for the pulmonary edema model was determined to be 6 mL/kg per minute, and a total of four pigs were tested at an injection rate of 6 mL/kg. The adjusted R2 values of regression analysis between the radiofrequency signal and computer tomography Hounsfield score were 0.990, 0.993, 0.988, and 0.993 (all P values <0.05). All radiofrequency signal changes preceded changes in PF ratio or lung ultrasound changes. The area under the receiver operating characteristic curve of the radiofrequency signal for predicting PF ratio <300 was 0.88 (95% confidence interval, 0.82-0.93). Conclusion: We evaluated ultrasound radiofrequency signals to assess pulmonary edema in a swine model that can worsen gradually and showed that quantitative ultrasound radiofrequency signal analysis could assess pulmonary edema and its progression before PF ratio or lung ultrasound changes.

Extravascular lung water monitoring for thoracic and lung transplant surgeries

PURPOSE OF REVIEW

Excessive accumulation of extravascular lung water (EVLW) resulting in pulmonary edema is the most feared complication following thoracic surgery and lung transplant. ICUs have long relied on chest radiography to monitor pulmonary status postoperatively but the increasing recognition of the limitations of bedside plain films has fueled development of newer technologies, which offer earlier detection, quantitative assessments, and can aide in preoperative screening of surgical candidates. In this review, we focus on the emergence of transpulmonary thermodilution (TPTD) and lung ultrasound with a focus on the clinical integration of these modalities into current intraoperative and critical care practices.

RECENT FINDINGS

Recent studies demonstrate transpulmonary thermodilution and lung ultrasound provide greater sensitivity and earlier detection of lung water accumulation and are useful to guide clinical management. Assessments from these techniques have predictive value of postoperative outcome. Further, EVLW assessment shows promise as a preoperative screening tool in lung transplant patients.

SUMMARY

Monitoring EVLW in the perioperative period offers clinicians a powerful tool to guide fluid therapy and manage pulmonary edema. Both TPTD and lung ultrasound have unique attributes in the care of thoracic surgery and lung transplant patients.

Effect of tidal volume on extravascular lung water content during one-lung ventilation for video-assisted thoracoscopic surgery: a randomised, controlled trial

BACKGROUND

The use of low tidal volume during one-lung ventilation (OLV) has been shown to attenuate the incidence of acute lung injury after thoracic surgery.

OBJECTIVE

To test the effect of tidal volume during OLV for video-assisted thoracoscopic surgery on the extravascular lung water content index (EVLWI).

DESIGN

A randomised, double-blind, controlled study.

SETTING

Single university hospital.

PARTICIPANTS

Thirty-nine patients scheduled for elective video-assisted thoracoscopic surgery.

INTERVENTIONS

Patients were randomly assigned to one of three groups (n = 13 per group) to ventilate the dependent lung with a tidal volume of 4, 6 or 8 ml  kg(-1) predicted body weight with I:E ratio of 1:2.5 and PEEP of 5 cm H2O.

MAIN OUTCOME MEASURES

The primary outcomes were perioperative changes in EVLWI and EVLWI to intrathoracic blood volume index (ITBVI) ratio. Secondary outcomes included haemodynamics, oxygenation indices, incidences of postoperative acute lung injury, atelectasis, pneumonia, morbidity and 30-day mortality.

RESULTS

A tidal volume of 4 compared with 6 and 8 ml  kg(-1) after 45 min of OLV resulted in an EVLWI of 4.1 [95% confidence interval (CI) 3.5 to 4.7] compared with 7.7 (95% CI 6.7 to 8.6) and 8.6 (95% CI 7.5 to 9.7) ml  kg(-1), respectively (P < 0.003). EVLWI/ITBVI ratios were 0.57 (95% CI 0.46 to 0.68) compared with 0.90 (95% CI 0.75 to 1.05) and 1.00 (95% CI 0.80 to 1.21), respectively (P < 0.05). The incidences of postoperative acute lung injury, atelectasis, pneumonia, morbidity, hospitalisation and 30-day mortality were similar in the three groups.

CONCLUSION

The use of a tidal volume of 4 ml kg during OLV was associated with less lung water content than with larger tidal volumes of 6 to 8 ml kg(-1), although no patient developed acute lung injury. Further studies are required to address the usefulness of EVLWI as a marker for the development of postoperative acute lung injury after the use of a low tidal volume during OLV in patients undergoing pulmonary resection.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT01762709.

Update on minimally invasive hemodynamic monitoring in thoracic anesthesia

PURPOSE OF REVIEW

Advanced hemodynamic monitoring is indispensable for adequate management of patients undergoing major surgery. This article will summarize minimally invasive hemodynamic monitoring technologies and their potential use in thoracic anesthesia.

RECENT FINDINGS

According to their inherent principle, currently available technologies can be classified into four groups: bioimpedance and bioreactance, applied Fick's principle, pulse wave analysis and Doppler. All devices measure stroke volume and cardiac output. Functional hemodynamic variables and volumetric parameters have been integrated in some devices. Two major indications can be identified: the 'hemodynamically unstable' patient and the patient 'at risk' for hemodynamic instability. Although there is evidence for the first indication, pre-emptive hemodynamic therapy or perioperative hemodynamic optimization for the patient 'at risk' is still an issue of ongoing debate. There is a growing body of evidence that this approach can positively influence patients' outcome with less postoperative complications in selected patient groups.

SUMMARY

Many different minimally invasive hemodynamic monitoring devices have been developed and clinically introduced in the last years. They offer the advantage of being less invasive and easier to use. However, these techniques have several limitations and data are scarce in patients undergoing thoracic anesthesia, preventing their widespread use so far.

Perioperative fluid management for pulmonary resection surgery and esophagectomy

Perioperative fluid management is of significant importance during pulmonary resection surgery and esophagectomy. Excessive fluid administration has been consistently shown as a risk factor for lung injury after thoracic procedures. Probable causes of this serious complication include fluid overload, lung lymphatics and pulmonary endothelial damage. Along with new insights regarding the Starling equation and the absence of a third space, current evidence supports a restrictive fluid regimen for patients undergoing pulmonary resection surgery and esophagectomy. Multiple minimally invasive hemodyamic monitoring devices, including pulse pressure/stroke volume variation, esophageal Doppler, and extravascular lung water measurement, were evaluated for optimizing perioperative fluid therapy. Further research regarding the prevention, diagnosis, and treatment of acute lung injury after pulmonary resection and esophagectomy is required.

Goal-directed fluid therapy using stroke volume variation does not result in pulmonary fluid overload in thoracic surgery requiring one-lung ventilation

Background. Goal-directed fluid therapy (GDT) guided by functional parameters of preload, such as stroke volume variation (SVV), seems to optimize hemodynamics and possibly improves clinical outcome. However, this strategy is believed to be rather fluid aggressive, and, furthermore, during surgery requiring thoracotomy, the ability of SVV to predict volume responsiveness has raised some controversy. So far it is not known whether GDT is associated with pulmonary fluid overload and a deleterious reduction in pulmonary function in thoracic surgery requiring one-lung-ventilation (OLV). Therefore, we assessed the perioperative course of extravascular lung water index (EVLWI) and p_aO₂/F_iO₂-ratio during and after thoracic surgery requiring lateral thoracotomy and OLV to evaluate the hypothesis that fluid therapy guided by SVV results in pulmonary fluid overload. Methods. A total of 27 patients (group T) were enrolled in this prospective study with 11 patients undergoing lung surgery (group L) and 16 patients undergoing esophagectomy (group E). Goal-directed fluid management was guided by SVV (SVV < 10%). Measurements were performed directly after induction of anesthesia (baseline—BL), 15 minutes after implementation OLV (OLVimpl15), and 15 minutes after termination of OLV (OLVterm15). In addition, postoperative measurements were performed at 6 (6postop), 12 (12postop), and 24 (24postop) hours after surgery. EVLWI was measured at all predefined steps. The p_aO₂/F_iO₂-ratio was determined at each point during mechanical ventilation (group L: BL-OLVterm15; group E: BL-24postop). Results. In all patients (group T), there was no significant change (P > 0.05) in EVLWI during the observation period (BL: 7.8 ± 2.5, 24postop: 8.1 ± 2.4 mL/kg). A subgroup analysis for group L and group E also did not reveal significant changes of EVLWI. The p_aO₂/F_iO₂-ratio decreased significantly during the observation period (group L: BL: 462 ± 140, OLVterm15: 338 ± 112 mmHg; group E: BL: 389 ± 101, 24postop: 303 ± 74 mmHg) but remained >300 mmHg except during OLV. Conclusions. SVV-guided fluid management in thoracic surgery requiring lateral thoracotomy and one-lung ventilation does not result in pulmonary fluid overload. Although oxygenation was reduced, pulmonary function remained within a clinically acceptable range.

CMV reactivation caused by methylprednisolone therapy for ARDS after esophagectomy

Background

Cytomegalovirus (CMV) infection is endemic worldwide. Although CMV reactivation often becomes a serious problem in immunocompromised patients, the prevalence of CMV reactivation caused by methylprednisolone therapy for ARDS after esophagectomy has yet to be determined.

Method

Among 175 consecutive patients with thoracic squamous cell esophageal cancer who underwent esophagectomy with extensive lymph node dissection at Akita University Hospital between 2007 and 2010, 11 patients (6.3 %) diagnosed with ARDS during the acute phase of esophagectomy were enrolled and treated with steroid pulse therapy, high-dose (15–20 mg/kg/day) administration and tapering in this retrospective study.

Results

Seven of the 11 patients (63.6 %) were diagnosed with CMV reactivation based on CMV antigenemia assayed 19.1 days after the start of methylprednisolone administration and were treated with ganciclovir for 39.6 days. Six of the 7 patients (85.7 %) diagnosed with CMV reactivation were administered a total methylprednisolone dose of more than 4,000 mg. Though there was no significant difference between patients with and without CMV reactivation, there was a tendency that patients with CMV reactivation showed a lower minimum number of lymphocytes during the acute phase of esophagectomy (p = 0.051, Student’s t test, average 223.3 and 298.0/μl, respectively).

Conclusion

Though the number of study patients is small, the prevalence of CMV reactivation caused by high-dose methylprednisolone therapy for ARDS after esophagectomy is remarkably high. This result strikes a note of warning concerning the management of these patients and suggests the importance of screenings for CMV reactivation so as to make an accurate diagnosis and initiate treatment in a timely manner.

[Hemodynamic monitoring in one-lung ventilation]

One-lung ventilation causes adverse effects in pulmonary gas exchange and cardiocirculatory function. These adverse effects become particularly important for patients with underlying cardiopulmonary comorbidities. Alterations in pulmonary gas exchange have been investigated in several experimental and clinical trials. However, the hemodynamic consequences of one-lung ventilation are to a great extent unknown. Furthermore, no conclusive recommendations exist as to which kind of hemodynamic monitoring should be preferred in the situation of one-lung ventilation. Many issues regarding hemodynamic monitoring in one-lung ventilation remain unacknowledged. This article will review the current literature on hemodynamic monitoring in one-lung ventilation in order to derive recommendations for the application of hemodynamic monitoring in this specific peri-operative situation.

Respiratory complications after oesophageal surgery

PURPOSE OF REVIEW

The most frequent complications of oesophageal surgery are respiratory and these are associated with increased critical care stay, hospital stay and mortality. This review focuses on the risk factors associated with the development of respiratory complications after oesophageal surgery.

RECENT FINDINGS

An acceptable operative mortality, increased and improved quality of life can be gained in appropriately selected patients. When induction therapy is scheduled, smoking cessation is advised. The preoperative treatment of airway pathogens can reduce postoperative complications and this may be particularly relevant in patients who have received induction chemoradiotherapy. Nonrandomized studies suggest that thoracic epidural analgesia improves outcome. Minimally invasive surgery is increasingly used and appears safe but direct comparisons to open surgery in terms of respiratory complications are awaited. Few randomized studies are available to guide anaesthetic management but anaesthetists should aim to avoid hypoxaemia, hypotension, aspiration and limit blood and fluid administration. Postoperative aspiration is common and steps to reduce it are recommended.

SUMMARY

The multifactorial nature of respiratory complications after oesophageal surgery may mean that a number of interventions are needed to have a detectable influence on outcome, much like a care bundle strategy.

The effect of duration of surgery on fluid balance during abdominal surgery: a mathematical model

BACKGROUND

There is controversy regarding which fluid management regimen provides the best postoperative outcome. Interstitial fluid accumulation may adversely affect postoperative outcome, but the effect of surgical duration on fluid balance is unknown. In this study, we used a mathematical model to describe fluid distribution.

METHODS

Previously published data from bioimpedance analysis in patients undergoing abdominal surgery were used to calculate changes to interstitial volume (DeltaV(IT), percent change relative to baseline) in uninjured and injured tissues. Ratios of DeltaV(IT) in uninjured and injured tissues at the end of surgery to total fluid volume infused during surgery (V(INF), mL/kg) were compared between surgeries of duration <3 h (n = 5) and > or = 3 h (n = 25). Critical values for change in plasma volume (DeltaV(PL), percent change relative to baseline) and DeltaV(IT), which give rise to adverse outcome, were calculated from previously published data on the physiological effects of IV fluid administration in healthy volunteers. Finally, simulated abdominal surgery in a 70 kg man for 1-8 h was used to determine the effect of crystalloid infusion rate between 2 and 30 mL x kg(-1) x h(-1) on DeltaV(PL) and DeltaV(IT). Fluid infusion rates that maintained DeltaV(PL) and DeltaV(IT) in uninjured tissue within critical values were then computationally determined as a function of duration of surgery.

RESULTS

Bioimpedance data showed that the differences in DeltaV(IT)/V(INF) ratios between uninjured and injured tissues were significant only for surgical duration > or = 3 h (0.30 +/- 0.17% x kg/mL vs 1.55 +/- 0.73% x kg/mL, P < 0.0001). Differences of DeltaV(IT)/V(INF) ratios between surgical durations <3 and > or = 3 h were found only for injured tissue (0.45 +/- 0.35% x kg/mL vs 1.55 +/- 0.73% x kg/mL, P = 0.003). The range of fluid infusion rates required to maintain DeltaV(PL) and DeltaV(IT) within the critical values (>-15% and <20%, respectively) was wide for short-duration surgery (2-18.5 mL x kg(-1) x h(-1) for a 2 h-surgery), whereas it was narrow for long-duration surgery (5-8 mL x kg(-1) x h(-1) for a 6 h-surgery).

CONCLUSIONS

Based on our model, it should be possible to increase the fluid infusion rate without significant interstitial edema for abdominal surgery of <3 h duration. However, our model predicts that restrictive fluid management should be used in abdominal surgery of >6 h duration to avoid excessive interstitial edema.