An adversarial learning approach to generate pressure support ventilation waveforms for asynchrony detection.

BACKGROUND AND OBJECTIVE: Mechanical ventilation is a life-saving treatment for critically-ill patients. During treatment, patient-ventilator asynchrony (PVA) can occur, which can lead to pulmonary damage, complications, and higher mortality. While traditional detection methods for PVAs rely on visual inspection by clinicians, in recent years, machine learning models are being developed to detect PVAs automatically. However, training these models requires large labeled datasets, which are difficult to obtain, as labeling is a labour-intensive and time-consuming task, requiring clinical expertise. Simulating the lung-ventilator interactions has been proposed to obtain large labeled datasets to train machine learning classifiers. However, the obtained data lacks the influence of different hardware, of servo-controlled algorithms, and different sources of noise. Here, we propose VentGAN, an adversarial learning approach to improve simulated data by learning the ventilator fingerprints from unlabeled clinical data. METHODS: In VentGAN, the loss functions are designed to add characteristics of clinical waveforms to the generated results, while preserving the labels of the simulated waveforms. To validate VentGAN, we compare the performance for detection and classification of PVAs when training a previously developed machine learning algorithm with the original simulated data and with the data generated by VentGAN. Testing is performed on independent clinical data labeled by experts. The McNemar test is applied to evaluate statistical differences in the obtained classification accuracy. RESULTS: VentGAN significantly improves the classification accuracy for late cycling, early cycling and normal breaths (p< 0.01); no significant difference in accuracy was observed for delayed inspirations (p = 0.2), while the accuracy decreased for ineffective efforts (p< 0.01). CONCLUSIONS: Generation of realistic synthetic data with labels by the proposed framework is feasible and represents a promising avenue for improving training of machine learning models.

Pain management after pneumothorax surgery: intercostal nerve block or thoracic epidural analgesia.

OBJECTIVES: In patients undergoing video-assisted thoracoscopic surgery for pneumothorax, the benefits and risks of single-shot intercostal nerve block as loco-regional analgesia are not well known. We retrospectively compared the effectiveness of intercostal nerve blocks as a viable alternative to thoracic epidural analgesia (TEA) regarding pain control and enhanced recovery. METHODS: A retrospective multicentre analysis with single-centre propensity score matching was performed in patients undergoing video-assisted thoracoscopic surgery for pneumothorax receiving either TEA or intercostal nerve block. The primary outcome was a proportion of pain scores ≥4 (scale 0-10) until postoperative day (POD) 3. Secondary outcomes included variation in pain over time, additional opioid use, length of stay, mobility, complications and recurrence rate. RESULTS: In 218 patients, TEA was compared to intercostal nerve block and showed no difference in the proportion of pain scores ≥4 {14.3% [interquartile range (IQR) 0.0-33.3] vs 11.1% (IQR 0.0-27.3) respectively, P = 0.24}, more frequently needed additional opioids on the day of surgery (18% vs 48%) and first POD (20% vs 42%), had a shorter length of stay (4.0 days [IQR 3.0-7.0] vs 3.0 days [IQR 2.8-4.0]) and were significantly more mobile until POD 3, while having similar recurrences. Intercostal nerve block had higher pain scores early in the course whereas TEA had higher late (rebound) pain scores. CONCLUSIONS: In a multimodal analgesic setting with additional opioids, intercostal nerve block shows comparable moments of unacceptable pain from POD 0-3 compared to TEA and is linked to improved mobility. Results require randomized confirmation.

Acute pain management after thoracoscopic lung resection: a systematic review and explorative meta-analysis.

OBJECTIVES: Pain after thoracoscopic surgery may increase the incidence of postoperative complications and impair recovery. Guidelines lack consensus regarding postoperative analgesia. We performed a systematic review and meta-analysis to determine the mean pain scores of different analgesic techniques (thoracic epidural analgesia, continuous or single-shot unilateral regional analgesia and only systemic analgesia) after thoracoscopic anatomical lung resection. METHODS: Medline, Embase and Cochrane databases were searched until 1 October 2022. Patients undergoing at least >70% anatomical resections through thoracoscopy reporting postoperative pain scores were included. Due to a high inter-study variability an explorative meta-analysis next to an analytic meta-analysis was performed. The quality of evidence has been evaluated using the Grading of Recommendations Assessment, Development and Evaluation system. RESULTS: A total of 51 studies comprising 5573 patients were included. Mean 24, 48 and 72 h pain scores with 95% confidence interval on a 0-10 scale were calculated. Length of hospital stay, postoperative nausea and vomiting, additional opioids and the use of rescue analgesia were analysed as secondary outcomes. A common-effect size was estimated with an extreme high heterogeneity for which pooling of the studies was not appropriate. An exploratory meta-analysis demonstrated acceptable mean pain scores of Numeric Rating Scale <4 for all analgesic techniques. CONCLUSIONS: This extensive literature review and attempt to pool mean pain scores for meta-analysis demonstrates that unilateral regional analgesia is gaining popularity over thoracic epidural analgesia in thoracoscopic anatomical lung resection, despite great heterogeneity and limitations of current studies precluding such recommendations. PROSPERO REGISTRATION: ID number 205311.

Evaluation of the accuracy of established patient inspiratory effort estimation methods during mechanical support ventilation.

There is a clinical need for monitoring inspiratory effort to prevent lung- and diaphragm injury in patients who receive supportive mechanical ventilation in an Intensive Care Unit. Different pressure-based techniques are available to estimate this inspiratory effort at the bedside, but the accuracy of their effort estimation is uncertain since they are all based on a simplified linear model of the respiratory system, which omits gas compressibility of air, and the viscoelasticity and nonlinearities of the respiratory system. The aim of this in-silico study was to provide an overview of the pressure-based estimation techniques and to evaluate their accuracy using a more sophisticated model of the respiratory system and ventilator. The influence of the following parameters on the accuracy of the pressure-based estimation techniques was evaluated using the in-silico model: 1) the patient's respiratory mechanics 2) PEEP and the inspiratory pressure of the ventilator 3) gas compressibility of air 4) viscoelasticity of the respiratory system 5) the strength of the inspiratory effort. The best-performing technique in terms of accuracy was the whole breath occlusion. The average error and maximum error were the lowest for all patient archetypes. We found that the error was related to the expansion of gas in the breathing set and lungs and respiratory compliance. However, concerns exist that other factors not included in the model, such as a changed muscle-force relation during an occlusion, might influence the true accuracy. The estimation techniques based on the esophageal pressure showed an error related to the viscoelastic element in the model which leads to a higher error than the occlusion. The error of the esophageal pressure-based techniques is therefore highly dependent on the pathology of the patient and the settings of the ventilator and might change over time while a patient recovers or becomes more ill.

Telemonitoring for perioperative care of outpatient bariatric surgery: Preference-based randomized clinical trial.

IMPORTANCE: Implementation of bariatric surgery on an outpatient basis is hampered by concerns about timely detection of postoperative complications. Telemonitoring could enhance detection and support transition to an outpatient recovery pathway. OBJECTIVE: This study aimed to evaluate non-inferiority and feasibility of an outpatient recovery pathway after bariatric surgery, supported by remote monitoring compared to standard care. DESIGN: Preference-based non-inferiority randomized trial. SETTING: Center for obesity and metabolic surgery, Catharina hospital Eindhoven, the Netherlands. PARTICIPANTS: Adult patients scheduled for primary gastric bypass or sleeve gastrectomy. INTERVENTIONS: Same-day discharge with one week ongoing Remote Monitoring (RM) of vital parameters or Standard Care (SC) with discharge on postoperative day one. MAIN OUTCOMES: Primary outcome was a thirty-day composite Textbook Outcome score encompassing mortality, mild and severe complications, readmission and prolonged length-of-stay. Non-inferiority of same-day discharge and remote monitoring was accepted below the selected margin of 7% upper limit of confidence interval. Secondary outcomes included admission duration, post-discharge opioid use and patients' satisfaction. RESULTS: Textbook Outcome was achieved in 94% (n = 102) in RM versus 98% (n = 100) in SC (RR 2.9; 95% CI, 0.60-14.23, p = 0.22). The non-inferiority margin was exceeded which is a statistically inconclusive result. Both Textbook Outcome measures were above Dutch average (5% RM and 9% SC). Same-day discharge reduced hospitalization days by 61% (p<0.001) and by 58% with re-admission days included (p<0.001). Post-discharge opioid use and satisfaction scores were equal (p = 0.82 and p = 0.86). CONCLUSION: In conclusion, outpatient bariatric surgery supported with telemonitoring is clinically comparable to standard overnight bariatrics in terms of textbook-outcome. Both approaches reached primary endpoint results above Dutch average. However, statistically the outpatient surgery protocol was neither inferior, nor non-inferior to the standard pathway. Additionally, offering same-day discharge reduces the total hospitalization days while maintaining patient satisfaction and safety.

Optimal postoperative pain management after VATS lung resection by thoracic epidural analgesia, continuous paravertebral block or single-shot intercostal nerve block (OPtriAL): study protocol of a three-arm multicentre randomised controlled trial.

BACKGROUND: Adequate pain control after video-assisted thoracoscopic surgery (VATS) for lung resection is important to improve postoperative mobilisation, recovery, and to prevent pulmonary complications. So far, no consensus exists on optimal postoperative pain management after VATS anatomic lung resection. Thoracic epidural analgesia (TEA) is the reference standard for postoperative pain management following VATS. Although the analgesic effect of TEA is clear, it is associated with patient immobilisation, bladder dysfunction and hypotension which may result in delayed recovery and longer hospitalisation. These disadvantages of TEA initiated the development of unilateral regional techniques for pain management. The most frequently used techniques are continuous paravertebral block (PVB) and single-shot intercostal nerve block (ICNB). We hypothesize that using either PVB or ICNB is non-inferior to TEA regarding postoperative pain and superior regarding quality of recovery (QoR). Signifying faster postoperative mobilisation, reduced morbidity and shorter hospitalisation, these techniques may therefore reduce health care costs and improve patient satisfaction. METHODS: This multi-centre randomised study is a three-arm clinical trial comparing PVB, ICNB and TEA in a 1:1:1 ratio for pain (non-inferiority) and QoR (superiority) in 450 adult patients undergoing VATS anatomic lung resection. Patients will not be eligible for inclusion in case of contraindications for TEA, PVB or ICNB, chronic opioid use or if the lung surgeon estimates a high probability that the operation will be performed by thoracotomy. PRIMARY OUTCOMES: (1) the proportion of pain scores ≥ 4 as assessed by the numerical rating scale (NRS) measured during postoperative days (POD) 0-2; and (2) the QoR measured with the QoR-15 questionnaire on POD 1 and 2. Secondary outcome measures are cumulative use of opioids and analgesics, postoperative complications, hospitalisation, patient satisfaction and degree of mobility. DISCUSSION: The results of this trial will impact international guidelines with respect to perioperative care optimization after anatomic lung resection performed through VATS, and will determine the most cost-effective pain strategy and may reduce variability in postoperative pain management. Trial registration The trial is registered at the Netherlands Trial Register (NTR) on February 1st, 2021 (NL9243). The NTR is no longer available since June 24th, 2022 and therefore a revised protocol has been registered at ClinicalTrials.gov on August 5th, 2022 (NCT05491239). PROTOCOL VERSION: version 3 (date 06-05-2022), ethical approval through an amendment (see ethical proof in the Study protocol proof).

A model-based approach to generating annotated pressure support waveforms.

Large numbers of asynchronies during pressure support ventilation cause discomfort and higher work of breathing in the patient, and are associated with an increased mortality. There is a need for real-time decision support to detect asynchronies and assist the clinician towards lung-protective ventilation. Machine learning techniques have been proposed to detect asynchronies, but they require large datasets with sufficient data diversity, sample size, and quality for training purposes. In this work, we propose a method for generating a large, realistic and labeled, synthetic dataset for training and validating machine learning algorithms to detect a wide variety of asynchrony types. We take a model-based approach in which we adapt a non-linear lung-airway model for use in a diverse patient group and add a first-order ventilator model to generate labeled pressure, flow, and volume waveforms of pressure support ventilation. The model was able to reproduce basic measured lung mechanics parameters. Experienced clinicians were not able to differentiate between the simulated waveforms and clinical data (P = 0.44 by Fisher's exact test). The detection performance of the machine learning trained on clinical data gave an overall comparable true positive rate on clinical data and on simulated data (an overall true positive rate of 94.3% and positive predictive value of 93.5% on simulated data and a true positive rate of 98% and positive predictive value of 98% on clinical data). Our findings demonstrate that it is possible to generate labeled pressure and flow waveforms with different types of asynchronies.

A Model-based Approach to Generating Annotated Pressure Support Waveforms.

During pressure support ventilation, every breath is triggered by the patient. Mismatches between the patient and the ventilator are called asynchronies. It has been reported that large numbers of asynchronies may be harmful and may lead to increased mortality. Automatic asynchrony detection and classification, with subsequent feedback to clinicians, will improve lung ventilation and, possibly, patient outcome. Machine learning techniques have been used to detect asynchronies. However, large, diverse and high-quality training and verification data sets are needed. In this work, we propose a model for generating a large, realistic, labeled, synthetic dataset for training and testing machine learning algorithms to detect a wide variety of asynchrony types. Next to a morphological evaluation of the obtained waveforms, validation of the proposed model includes a test with a machine learning algorithm trained on clinical data.

Continuous erector spinae plane block versus thoracic epidural analgesia in video-assisted thoracic surgery: a study protocol for a prospective randomized open label non-inferiority trial.

BACKGROUND: Thoracic epidural analgesia is considered the gold standard for pain relief in video-assisted thoracoscopic surgery. This neuraxial technique blocks pain sensation by injecting a local anesthetic agent in the epidural space near the spinal cord to block spinal nerve roots. Recently, the erector spinae plane block has been introduced as a practical alternative to the thoracic epidural. This interfascial regional anesthesia technique interrupts pain sensation by injecting a local anesthetic agent in between the muscular layers of the thoracic wall. Several case series and three RCTs described it as an effective pain management technique in video-assisted thoracoscopic surgery (Scimia et al., Reg Anesth Pain Med 42:537, 2017; Adhikary et al., Indian J Anaesth 62:75-8, 2018; Kim, A randomized controlled trial comparing continuous erector spinae plane block with thoracic epidural analgesia for postoperative pain management in video-assisted thoracic surgery, n.d.; Yao et al., J Clin Anesth 63:109783, 2020; Ciftci et al., J Cardiothorac Vasc Anesth 34:444-9, 2020). The objective of this study is to test the hypothesis that a continuous erector spinae plane block incorporated into an opioid-based systemic multimodal analgesia regimen is non-inferior in terms of the quality of postoperative recovery compared to continuous thoracic epidural local anesthetic-opioid analgesia in patients undergoing elective unilateral video-assisted thoracoscopic surgery. METHODS: This is a prospective randomized open label non-inferiority trial. A total of 90 adult patients undergoing video-assisted thoracoscopic surgery will be randomized 1:1 to receive pain treatment with either (1) continuous erector spinae plane block plus intravenous patient-controlled analgesia with piritramide (study group) or (2) continuous thoracic epidural analgesia with a local anesthetic-opioid infusate (control group). All patients will receive additional systemic multimodal analgesia with paracetamol and non-steroidal anti-inflammatory drugs. The primary endpoint is the quality of recovery as measured by the Quality of Recovery-15 score. Secondary endpoints are postoperative pain as Numerical Rating Score scores, length of hospital stay, failure of analgesic technique, postoperative morphine-equivalent consumption, itching, nausea and vomiting, total operative time, complications related to surgery, perioperative hypotension, complications related to pain treatment, duration of bladder catheterization, and time of first assisted mobilization > 20 m and of mobilization to sitting in a chair. DISCUSSION: This randomized controlled trial aims to confirm whether continuous erector spinae plane block plus patient-controlled opioid analgesia can equal the analgesic effect of a thoracic epidural local anesthetic-opioid infusion in patients undergoing video-assisted thoracoscopic surgery. TRIAL REGISTRATION: Netherlands Trial Register NL6433 . Registered on 1 March 2018. This trial was prospectively registered.

Differences in identification of patients' deterioration may hamper the success of clinical escalation protocols.

BACKGROUND: Timely and consistent recognition of a 'clinical crisis', a life threatening condition that demands immediate intervention, is essential to reduce 'failure to rescue' rates in general wards. AIM: To determine how different clinical caregivers define a 'clinical crisis' and how they respond to it. DESIGN: An international survey. METHODS: Clinicians working on general wards, intensive care units or emergency departments in the Netherlands, the United Kingdom and Denmark were asked to review ten scenarios based on common real-life cases. Then they were asked to grade the urgency and severity of the scenario, their degree of concern, their estimate for the risk for death and indicate their preferred action for escalation. The primary outcome was the scenarios with a National Early Warning Score (NEWS) ≥7 considered to be a 'clinical crisis'. Secondary outcomes included how often a rapid response system (RRS) was activated, and if this was influenced by the participant's professional role or experience. The data from all participants in all three countries was pooled for analysis. RESULTS: A total of 150 clinicians participated in the survey. The highest percentage of clinicians that considered one of the three scenarios with a NEWS ≥7 as a 'clinical crisis' was 52%, while a RRS was activated by <50% of participants. Professional roles and job experience only had a minor influence on the recognition of a 'clinical crisis' and how it should be responded to. CONCLUSION: This international survey indicates that clinicians differ on what they consider to be a 'clinical crisis' and on how it should be managed. Even in cases with a markedly abnormal physiology (i.e. NEWS ≥7) many clinicians do not consider immediate activation of a RRS is required.

Cardiac structure and function before and after bariatric surgery: a clinical overview.

Obesity, defined as a body mass index of ≥30 kg/m2 , is the most common chronic metabolic disease worldwide and its prevalence has been strongly increasing. Obesity has deleterious effects on cardiac function. The purpose of this review is to evaluate the effects of obesity and excessive weight loss due to bariatric surgery on cardiac function, structural changes and haemodynamic responses of both the left and right ventricle.

The Hemodynamic Effects of Different Pacing Modalities After Cardiopulmonary Bypass in Patients With Reduced Left Ventricular Function.

OBJECTIVES: Patients with decreased left ventricular function undergoing cardiac surgery have a greater chance of difficult weaning from cardiopulmonary bypass and a poorer clinical outcome. Directly after weaning, interventricular dyssynchrony, paradoxical septal motion, and even temporary bundle-branch block might be observed. In this study, the authors measured arterial dP/dtmax, mean arterial pressure (MAP), and cardiac index using transpulmonary thermodilution, pulse contour analysis, and femoral artery catheter and compared the effects between right ventricular (A-RV) and biventricular (A-BiV) pacing on these parameters. DESIGN: Prospective study. SETTING: Single-center study. PARTICIPANTS: The study comprised 17 patients with a normal or prolonged QRS duration and a left ventricular ejection fraction ≤35% who underwent coronary artery bypass grafting with or without valve replacement. INTERVENTIONS: Temporary pacing wires were placed on the right atrium and both ventricles. Different pacing modalities were used in a standardized order. MEASUREMENTS AND MAIN RESULTS: A-BiV pacing compared with A-RV pacing demonstrated higher arterial dP/dtmax values (846 ± 646 mmHg/s v 800 ± 587 mmHg/s, p = 0.023) and higher MAP values (77 ± 19 mmHg v 71 ± 18 mmHg, p = 0.036). CONCLUSION: In patients with preoperative decreased left ventricular function undergoing coronary artery bypass grafting, A-BiV pacing improve the arterial dP/dtmax and MAP in patients with both normal and prolonged QRS duration compared with standard A-RV pacing. In addition, arterial dP/dtmax and MAP can be used to evaluate the effect of intraoperative pacing. In contrast to previous studies using more invasive techniques, transpulmonary thermodilution is easy to apply in the perioperative clinical setting.

Intelligent dynamic clinical checklists improved checklist compliance in the intensive care unit.

BACKGROUND: Checklists can reduce medical errors. However, the effectiveness of checklists is hampered by lack of acceptance and compliance. Recently, a new type of checklist with dynamic properties has been created to provide more specific checklist items for each individual patient. Our purpose in this simulation-based study was to investigate a newly developed intelligent dynamic clinical checklist (DCC) for the intensive care unit (ICU) ward round. METHODS: Eligible clinicians were invited to participate as volunteers. Highest achievable scores were established for six typical ICU scenarios to determine which items must be checked. The participants compared the DCC with the local standard of care. The primary outcomes were the caregiver satisfaction score and the percentages of checked items overall and of critical items requiring a direct intervention. RESULTS: In total, 20 participants were included, who performed 116 scenarios. The median percentage of checked items was 100.0% with the DCC and 73.6% for the scenarios completed with local standard of care ( P <0.001). Critical items remained unchecked in 23.1% of the scenarios performed with local standard of care and 0.0% of the scenarios where the DCC was available ( P <0.001). The mean satisfaction score of the DCC was 4.13 out of 5. CONCLUSIONS: This simulation study indicates that an intelligent DCC significantly increases compliance with best practice by reducing the percentage of unchecked items during ICU ward rounds, while the user satisfaction rate remains high. Real-life clinical research is required to evaluate this new type of checklist further.

Use of failure-to-rescue to identify international variation in postoperative care in low-, middle- and high-income countries: a 7-day cohort study of elective surgery.

BACKGROUND: The incidence and impact of postoperative complications are poorly described. Failure-to-rescue, the rate of death following complications, is an important quality measure for perioperative care but has not been investigated across multiple health care systems. METHODS: We analysed data collected during the International Surgical Outcomes Study, an international 7-day cohort study of adults undergoing elective inpatient surgery. Hospitals were ranked by quintiles according to surgical procedural volume (Q1 lowest to Q5 highest). For each quintile we assessed in-hospital complications rates, mortality, and failure-to-rescue. We repeated this analysis ranking hospitals by risk-adjusted complication rates (Q1 lowest to Q5 highest). RESULTS: A total of 44 814 patients from 474 hospitals in 27 low-, middle-, and high-income countries were available for analysis. Of these, 7508 (17%) developed one or more postoperative complication, with 207 deaths in hospital (0.5%), giving an overall failure-to-rescue rate of 2.8%. When hospitals were ranked in quintiles by procedural volume, we identified a three-fold variation in mortality (Q1: 0.6% vs Q5: 0.2%) and a two-fold variation in failure-to-rescue (Q1: 3.6% vs Q5: 1.7%). Ranking hospitals in quintiles by risk-adjusted complication rate further confirmed the presence of important variations in failure-to-rescue, indicating differences between hospitals in the risk of death among patients after they develop complications. CONCLUSIONS: Comparison of failure-to-rescue rates across health care systems suggests the presence of preventable postoperative deaths. Using such metrics, developing nations could benefit from a data-driven approach to quality improvement, which has proved effective in high-income countries.

Unilateral Vocal Cord Paralysis following Insertion of a Supreme Laryngeal Mask in a Patient with Sjögren's Syndrome.

Since its introduction in 1988 by Dr. Archie Brain, the laryngeal mask airway (LMA) is being used with increasing frequency. Its ease of use has made it a very popular device in airway management and compared to endotracheal intubation it is less invasive. The use of LMA was on the rise, so has been the incidence of its related complications. We report severe unilateral vocal cord paralysis following the use of the supreme laryngeal mask (sLMA) in a patient with Sjögren's syndrome. In addition, we propose possible mechanisms of injury, review the existing case reports, and discuss our findings.

Evaluation of a new double-lumen endobronchial tube with an integrated camera (VivaSight-DL(™) ): a prospective multicentre observational study.

The VivaSight-DL(™) is a new single-use double-lumen endobronchial tube with an integrated camera. We studied this device in 151 consecutive patients scheduled for elective thoracic surgery in four different hospitals. Endobronchial intubation was successful in 148 patients (98%) (95% CI 94-99%). Median (IQR [range]) endobronchial intubation time was 59 (47-82 [17-932]) s and lung isolation was successfully achieved in 147 (99%) patients (95% CI 96-99%). A fibreoptic bronchoscope was required to assist endobronchial tube placement in 19 (13%) patients (95% CI 8-19%). Sore throat was reported by 37 (25%) patients (95% CI 18-33%), but no major complications were observed. We have reported the successful use of the VivaSight double-lumen tube for endobronchial intubation in a multicentre observational trial.

Pulmonary blood volume measured by contrast enhanced ultrasound: a comparison with transpulmonary thermodilution.

BACKGROUND: Blood volume quantification is essential for haemodynamic evaluation guiding fluid management in anaesthesia and intensive care practice. Ultrasound contrast agent (UCA)-dilution measured by contrast enhanced ultrasound (CEUS) can provide the UCA mean transit time (MTT) between the right and left heart, enabling the assessment of the intrathoracic blood volume (ITBV(UCA)). The purpose of the present study was to investigate the agreement between UCA-dilution using CEUS and transpulmonary thermodilution (TPTD) in vitro and in vivo. METHODS: In an in vitro setup, with variable flows and volumes, we injected a double indicator, ice-cold saline with SonoVue(®), and performed volume measurements using transesophageal echo and thermodilution by PiCCO(®). In a pilot study, we assigned 17 patients undergoing elective cardiac surgery for pulmonary blood volume (PBV) measurement using TPTD by PiCCO(®) and ITBV by UCA-dilution. Correlation coefficients and Bland-Altman analysis were performed for all volume measurements. RESULTS: In vitro, 73 experimental MTT's were obtained using PiCCO(®) and UCA-dilution. The volumes by PiCCO(®) and UCA-dilution correlated with true volumes; r(s)=0.96 (95% CI, 0.93-0.97; P<0.0001) and r(s)=0.97 (95% CI, 0.95-0.98; P<0.0001), respectively. The bias of PBV by PiCCO(®) and ITBV(UCA) were -380 ml and -42 ml, respectively. In 16 patients, 86 measurements were performed. The correlation between PBV by PiCCO(®) and ITBV(UCA) was r(s)=0.69 (95% CI 0.55-0.79; P<0.0001). Bland-Altman analysis revealed a bias of -323 ml. CONCLUSIONS: ITBV assessment with CEUS seems a promising technique for blood volume measurement, which is minimally-invasive and bedside applicable. CLINICAL TRIAL REGISTRATION: ISRCTN90330260.

Anaesthetic management during open and percutaneous irreversible electroporation.

BACKGROUND: Irreversible electroporation (IRE) is a novel tumour ablation technique involving repetitive application of electrical energy around a tumour. The use of pulsed electrical gradients carries a risk of cardiac arrhythmias, severe muscle contractions, and seizures. We aimed to identify IRE-related risks and the appropriate precautions for anaesthetic management. METHODS: All patients who were treated with IRE were prospectively included. Exclusion criteria were arrhythmias, congestive heart failure, active coronary artery disease, and epilepsy. All procedures were performed under general anaesthesia with complete muscle relaxation during ECG-synchronized pulsing. Adverse events, cardiovascular effects, blood samples, cerebral activity, and post-procedural pain were analysed. RESULTS: Twenty-eight patients underwent 30 IRE sessions for tumours in the liver, pancreas, kidney, and lesser pelvis. No major adverse events occurred during IRE. Median systolic and diastolic blood pressure increased by 44 mm Hg (range -7 to 108 mm Hg) and 19 mm Hg (range 1-50 mm Hg), respectively. Two transient minor cardiac arrhythmias without haemodynamic consequences were observed. Muscle contractions were mild and IRE caused no reactive brain activity on a simplified EEG. Pain in the first 24 h after percutaneous IRE was generally mild, but higher pain scores were reported after pancreatic treatment (mean VAS score 3; range 0-9). CONCLUSIONS: Side-effects during IRE on tumours in the liver, pancreas, kidney, and lesser pelvis seem mild and manageable when current recommendations for anaesthesia management, including deep muscle relaxation and ECG synchronized pulsing, are followed. Electrical pulses do not seem to cause reactive cerebral activity and evidence for pre-existing atrial fibrillation as an absolute contra-indication for IRE is questionable.