Dexmedetomidine improves pulmonary outcomes in thoracic surgery under one-lung ventilation: A meta-analysis

INTRODUCTION

Dexmedetomidine improves intrapulmonary shunt in thoracic surgery and minimizes inflammatory response during one-lung ventilation (OLV). However, it is unclear whether such benefits translate into less postoperative pulmonary complications (PPCs). Our objective was to determine the impact of dexmedetomidine on the incidence of PPCs after thoracic surgery.

METHODS

Major databases were used to identify randomized trials that compared dexmedetomidine versus placebo during thoracic surgery in terms of PPCs. Our primary outcome was atelectasis within 7 days after surgery. Other specific PPCs included hypoxemia, pneumonia, and acute respiratory distress syndrome (ARDS). Secondary outcome included intraoperative respiratory mechanics (respiratory compliance [Cdyn]) and postoperative lung function (forced expiratory volume [FEV1]). Random effects models were used to estimate odds ratios (OR).

RESULTS

Twelve randomized trials, including 365 patients in the dexmedetomidine group and 359 in the placebo group, were analyzed in this meta-analysis. Patients in the dexmedetomidine group were less likely to develop postoperative atelectasis (2.3% vs 6.8%, OR 0.42, 95%CI 0.18-0.95, P = 0.04; low certainty) and hypoxemia (3.4% vs 11.7%, OR 0.26, 95%CI 0.10-0.68, P = 0.01; moderate certainty) compared to the placebo group. The incidence of postoperative pneumonia (3.2% vs 5.8%, OR 0.57, 95%CI 0.25-1.26, P = 0.17; moderate certainty) or ARDS (0.9% vs 3.5%, OR 0.39, 95%CI 0.07-2.08, P = 0.27; moderate certainty) was comparable between groups. Both intraoperative Cdyn and postoperative FEV1 were higher among patients that received dexmedetomidine with a mean difference of 4.42 mL/cmH2O (95%CI 3.13-5.72) and 0.27 L (95%CI 0.12-0.41), respectively.

CONCLUSION

Dexmedetomidine administration during thoracic surgery may potentially reduce the risk of postoperative atelectasis and hypoxemia. However, current evidence is insufficient to demonstrate an effect on pneumonia or ARDS.

Anesthetic Management of a Jehovah's Witness Patient for Coronary Artery Bypass Grafting With Antiphospholipid Antibody Syndrome and Renal Transplant

Anesthesia for cardiac surgical patients with antiphospholipid antibody syndrome (APLS) presents challenges with monitoring anticoagulation during cardiopulmonary bypass. Additionally, this condition is associated with other autoimmune diseases and comorbidities that need to be considered in caring for these patients, and there is minimal evidence for specific strategies during cardiac surgery. Separately, Jehovah's Witness (JW) patients typically do not consent to receiving blood products, presenting an additional challenge for resuscitation during cardiac surgery and especially in the context of APLS. We present our approach to the anesthetic management of a JW patient with systemic lupus erythematosus (SLE) complicated by APLS, thrombocytopenia, and renal failure with history of renal transplant who presented for coronary artery bypass surgery. Management strategies we recommend include administration of antifibrinolytics after heparinization to mitigate bleeding risk and interdisciplinary management with the perfusion, intensive care, surgical, and nephrology teams.

Postoperative Hypoxemia After Dual-Controlled vs Volume-Controlled Ventilation in Lung Surgery

BACKGROUND

One-lung ventilation for thoracic surgery represents a challenge due to the risk for hypoxemia and barotrauma. Dual-controlled ventilation (ie, pressure-regulated volume control [PRVC]) may confer improved lung mechanics compared with conventional ventilation (volume-controlled ventilation [VCV]). Our objective was to determine the association between ventilatory mode and pulmonary outcomes after lung resection surgery.

METHODS

A historical cohort (2016-2021) of patients undergoing lung resection surgery was used to identify cases performed with PRVC ventilation (intervention) vs VCV (conventional). Both groups were matched in a 1:1 fashion using propensity scoring based on preoperative oxygen saturation, chronic obstructive pulmonary disease, intraoperative ventilator settings, and surgical approach. Our primary outcome was postoperative hypoxemia (oxygen saturation <92% requiring supplemental oxygen longer than 2 hours). Secondary outcomes included respiratory failure, pneumonia, atelectasis, acute respiratory distress syndrome, pleural effusion, and reintubation. Associations were reported using adjusted odds ratios (aOR).

RESULTS

Of 2107 eligible patients (PRVC = 1587 vs VCV = 520), a total of 774 matched pairs were analyzed (PRVC = 387 vs VCV = 387). The overall incidence of postoperative hypoxemia was 35.5% (95% CI 32.2%-39.0%). Hypoxemia was less likely among patients managed with low tidal volumes (≤6 mL/kg per ideal body weight, aOR 0.73, 95% CI 0.57-0.92, P = .008). No significant association was observed between ventilator mode and postoperative hypoxemia (33.3% in PRVC vs 37.7% in VCV; aOR 0.93, 95% CI 0.71-1.23, P = .627) or secondary pulmonary complications (3.9% in PRVC vs 3.4% in VCV; aOR 0.96, 95% CI 0.47-1.97, P = .909).

CONCLUSIONS

Dual-controlled ventilation was not associated with improved pulmonary outcomes compared with conventional ventilation in lung resection surgery.

State of the art: Proceedings of the American Association for Thoracic Surgery Enhanced Recovery After Cardiac Surgery Summit

Despite the benefits established for multiple surgical specialties, enhanced recovery after surgery has been underused in cardiac surgery. A cardiac enhanced recovery after surgery summit was convened at the 102nd American Association for Thoracic Surgery annual meeting in May 2022 for experts to convey key enhanced recovery after surgery concepts, best practices, and applicable results for cardiac surgery. Topics included implementation of enhanced recovery after surgery, prehabilitation and nutrition, rigid sternal fixation, goal-directed therapy, and multimodal pain management.

Performance Comparison of Pulmonary Risk Scoring Systems in Lung Resection

OBJECTIVE

To validate and compare the performance of different pulmonary risk scoring systems to predict postoperative pulmonary complications (PPCs) in lung resection surgery.

DESIGN

Retrospective cohort study SETTING: A historic single-center cohort of lung resection surgeries PARTICIPANTS: Adult patients undergoing lung resection surgery under 1-lung ventilation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The accuracy of the following pulmonary risk scoring systems were used to predict pulmonary complications: the ARISCAT (Assess respiratory RIsk in Surgical patients in CATalonia), the LAS VEGAS (Local Assessment of VEntilatory management during General Anesthesia for Surgery), the SPORC (Score for Prediction of Postoperative Respiratory Complications), and a recent thoracic-specific risk score, named CARDOT. Discrimination and calibration were assessed using the concordance (c) index and the intercept of LOESS (locally estimated scatterplot)-smoothed curves, respectively. Additional models were constructed that incorporated predicted postoperative forced expiratory volume (ppoFEV1) into each scoring system. Of the 2,104 patients undergoing lung surgery, 123 developed postoperative pulmonary complications (PPCs; 5.9%). All scoring systems had poor discriminatory power to predict PPCs (ARISCAT c-index 0.60, 95% confidence interval [CI] 0.55-0.65; LAS VEGAS c-index 0.68, 95% CI 0.63-0.73; SPORC c-index 0.63, 95% CI 0.59-0.68; CARDOT c-index 0.64, 95% CI 0.58-0.70), but the inclusion of ppoFEV1 slightly improved the performance of LAS VEGAS (c-index 0.70, 95% CI 0.66-0.75) and CARDOT (c-index 0.68, 95% CI 0.62-0.73). Analysis of calibration showed a slight overestimation when using ARISCAT (intercept -0.28) and LAS VEGAS (intercept -0.27).

CONCLUSIONS

None of the scoring systems appeared to have adequate discriminatory power to predict PPCs among patients undergoing lung resection. An alternative risk score is necessary to better predict patients at risk of PPCs after thoracic surgery.

Efficacy of opioid-sparing analgesia after median sternotomy with continuous bilateral parasternal subpectoral plane blocks

OBJECTIVES

Regional anesthetic techniques, traditionally underutilized in cardiac surgery, may play a role in multimodal analgesia, effectively improving pain control and reducing opioid consumption. We investigated the efficacy of continuous bilateral ultrasound-guided parasternal subpectoral plane blocks following sternotomy.

METHODS

We reviewed all opioid-naïve patients who underwent cardiac surgery via median sternotomy under our enhanced recovery after surgery protocol between May 2018 and March 2020. Patients were grouped based on postoperative pain management strategy-those who received standard Enhanced Recovery After Surgery (ERAS) multimodal analgesia alone (no nerve block group) versus those receiving ERAS multimodal analgesia plus continuous bilateral parasternal subpectoral plane blocks (block group). In the block group, parasternal subpectoral plane catheters were placed under ultrasound-guidance on each side of the sternum with initial 0.25% ropivacaine bolus, followed by continuous 0.125% bupivacaine infusions. Postoperative patient-reported numerical rating scale pain scores and opioid consumption in morphine milligram equivalents were compared through postoperative day 4.

RESULTS

Of 281 patients included in the study, the block group comprised 125 (44%) patients. Although baseline characteristics, type of surgery, and length of stay were similar between groups, average numerical rating scale pain scores and opioid consumption were significantly lower in the block group through postoperative day 4 (all P values < .05). We also observed a 44% reduction in total opioid consumption after surgery in the block group (75.1 vs 133.1 MME; P = .001) and 1 less hospital day requiring opioids (4.2 vs 3 days; P = .001).

CONCLUSIONS

Continuous bilateral parasternal subpectoral plane blocks may further reduce poststernotomy pain and opioid consumption within the context ERAS multimodal analgesia.

MIT Emergency-Vent: An Automated Resuscitator Bag for the COVID-19 Crisis. Annu Int Conf IEEE Eng Med Biol Soc 2021;2021:4998-5004. [PMID: 34892330 DOI: 10.1109/embc46164.2021.9630882]

MIT's Emergency-Vent Project was launched in March 2020 to develop safe guidance and a reference design for a bridge ventilator that could be rapidly produced in a distributed manner worldwide. The system uses a novel servo-based robotic gripper to automate the squeezing of a manual resuscitator bag evenly from both sides to provide ventilation according to clinically specified parameters. In just one month, the team designed and built prototype ventilators, tested them in a series of porcine trials, and collaborated with industry partners to enable mass production. We released the design, including mechanical drawings, design spreadsheets, circuit diagrams, and control code into an open source format and assisted production efforts worldwide.Clinical relevance- This work demonstrated the viability of automating the compression of a manual resuscitator bag, with pressure feedback, to provide bridge ventilation support.

Enhanced Recovery After Cardiac Surgery: A Propensity-Matched Analysis

Enhanced Recovery After Surgery (ERAS) pathways have improved clinical outcomes, cost-effectiveness, and patient satisfaction across multiple non-cardiac surgical specialties. Since the adaptation of ERAS in cardiac surgery is rapidly increasing yet still evolving, herein, we demonstrate early results of our implementation of ERAS cardiac guidelines. We retrospectively reviewed all patients who were managed with our institutional ERAS Cardiac Surgery guidelines between 5/2018 and 6/2019(N = 102). Postoperative primary outcomes (total ventilation times(hours), intensive-care unit(ICU) stay, and postoperative hospital length of stay (LOS)) were compared to 1:1 propensity matched controls from the pre ERAS era between January 2017 and March 2019. A total of 76 propensity-matched pairs were identified. Compared to the matched controls, ERAS patients had significantly shorter median ventilation times(3.5 vs. 5.3 hours, p = .01), ICU stays(median 28 vs 48 hours, p=.005) and postoperative hospital LOS (median 5 vs. 6 days, p = .03). There were no operative mortalities and no significant differences in 30-day readmission rates. There were also no significant differences in post-operative stroke, acute kidney injury, atrial fibrillation, and reoperation rates for bleeding. Two-year survival was also not statistically different between the two cohorts (p = .22). Our initial experience with implementation of ERAS protocols in cardiac surgery appear to demonstrate that these protocols are associated with shorter ventilation times, ICU stay, and hospital LOS without compromising patient outcomes. While these results are promising yet preliminary, further studies are warranted to demonstrate whether ERAS algorithms in cardiac surgery can consistently expedite postoperative recovery and improve outcomes.

Respiratory Considerations Including Airway and Ventilation Issues in Critical Care Obstetric Patients

Critical care management of the obstetric patient can present unique challenges. Parturients who present with respiratory distress can suffer from a multitude of etiologies, and each diagnosis must be pursued as appropriate to the clinical picture. Normal physiologic changes of pregnancy may obscure the presentation and diagnosis, and irrelevant of the cause, pregnancy may complicate the management of hypoxic and hypercarbic respiratory failure in this patient population. In addition to these concerns, both anticipated and unanticipated difficult airway management, including difficulty ventilating and intubating, are more common during pregnancy and may be encountered during endotracheal tube placement.

Cardiorespiratory effects of spontaneous breathing in two different models of experimental lung injury: a randomized controlled trial

Introduction

Acute lung injury (ALI) can result from various insults to the pulmonary tissue. Experimental and clinical data suggest that spontaneous breathing (SB) during pressure-controlled ventilation (PCV) in ALI results in better lung aeration and improved oxygenation. Our objective was to evaluate whether the addition of SB has different effects in two different models of ALI.

Methods

Forty-four pigs were randomly assigned to ALI resulting either from hydrochloric acid aspiration (HCl-ALI) or from increased intra-abdominal pressure plus intravenous oleic acid injections (OA-ALI) and were ventilated in PCV mode either with SB (PCV + SB) or without SB (PCV – SB). Cardiorespiratory variables were measured at baseline after induction of ALI and after 4 hours of treatment (PCV + SB or PCV – SB). Finally, density distributions and end-expiratory lung volume (EELV) were assessed by thoracic spiral computed tomography.

Results

PCV + SB improved arterial partial pressure of oxygen/inspiratory fraction of oxygen (PaO₂/FiO₂) by a reduction in intrapulmonary shunt fraction in HCl-ALI from 27% ± 6% to 23% ± 13% and in OA-ALI from 33% ± 19% to 26% ± 18%, whereas during PCV – SB PaO₂/FiO₂ deteriorated and shunt fraction increased in the HCl group from 28% ± 8% to 37% ± 17% and in the OA group from 32% ± 12% to 47% ± 17% (P < 0.05 for interaction time and treatment, but not ALI type). PCV + SB also resulted in higher EELV (HCl-ALI: 606 ± 171 mL, OA-ALI: 439 ± 90 mL) as compared with PCV – SB (HCl-ALI: 372 ± 130 mL, OA-ALI: 192 ± 51 mL, with P < 0.05 for interaction of time, treatment, and ALI type).

Conclusions

SB improves oxygenation, reduces shunt fraction, and increases EELV in both models of ALI.

The impact of spontaneous breathing during mechanical ventilation

PURPOSE OF REVIEW

In patients with acute respiratory distress syndrome, controlled mechanical ventilation is generally used in the initial phase to ensure adequate alveolar ventilation, arterial oxygenation, and to reduce work of breathing without causing further damage to the lungs. Although introduced as weaning techniques, partial ventilator support modes have become standard techniques for primary mechanical ventilator support. This review evaluates the physiological and clinical effects of persisting spontaneous breathing during ventilator support in patients with acute respiratory distress syndrome.

RECENT FINDINGS

The improvements in pulmonary gas exchange, systemic blood flow and oxygen supply to the tissue which have been observed when spontaneous breathing has been maintained during mechanical ventilation are reflected in the clinical improvement in the patient's condition. Computer tomography observations demonstrated that spontaneous breathing improves gas exchange by redistribution of ventilation and end-expiratory gas to dependent, juxtadiaphragmatic lung regions and thereby promotes alveolar recruitment. Thus, spontaneous breathing during ventilator support counters the undesirable cyclic alveolar collapse in dependent lung regions. In addition, spontaneous breathing during ventilator support may prevent increase in sedation beyond a level of comfort to adapt the patient to mechanical ventilation which decreases duration of mechanical ventilator support, length of stay in the intensive care unit, and overall costs of care giving.

SUMMARY

In view of the recently available data, it can be concluded that maintained spontaneous breathing during mechanical ventilation should not be suppressed even in patients with severe pulmonary functional disorders.

Effects of spontaneous breathing during airway pressure release ventilation on respiratory work and muscle blood flow in experimental lung injury

STUDY OBJECTIVES

To evaluate the effects of spontaneous breathing at ambient airway pressure (Paw) and during airway pressure release ventilation (APRV) on respiratory work and respiratory muscle blood flow (RMBF) in experimental lung injury.

DESIGN

Prospective experimental study.

SETTING

Research laboratory of a university hospital.

SUBJECTS

Twelve hemodynamically stable, analgosedated, and tracheotomized domestic pigs.

MEASUREMENTS

Respiratory work was estimated by the inspiratory pressure time product (PTPinsp) of esophageal pressure, and RMBF was measured with colored microspheres. Lung injury was induced with IV boli of oleic acid. The first set of measurements was performed before induction of lung injury while pigs were breathing spontaneously at ambient Paw, the second after induction of lung injury while breathing spontaneously at ambient Paw, and the third with lung injury and spontaneous breathing with APRV.

RESULTS

After induction of lung injury PTPinsp increased from 138 +/- 14 to 214 +/- 32 cm H2O s/min when pigs breathed spontaneously at ambient Paw (p < 0.05) and returned to 128 +/- 27 cm H2O s/min during APRV. While systemic hemodynamics and blood flow to the psoatic and intercostal muscles did not change, diaphragmatic blood flow increased from 0.34 +/- 0.05 before to 0.54 +/- 0.08 mL/g/min after induction of lung injury and spontaneous breathing at ambient Paw (p < 0.05) and returned to 0.32 +/- 0.05 mL/g/min during APRV (p < 0.05 vs spontaneous breathing at ambient Paw [lung injury]).

CONCLUSION

Respiratory work and RMBF are increased in acute lung injury when subjects breathe spontaneously at ambient Paw. Supporting spontaneous breathing with APRV decreases respiratory work and RMBF to physiologic values.

Proportional assist versus pressure support ventilation in patients with acute respiratory failure: Cardiorespiratory responses to artificially increased ventilatory demand*

OBJECTIVE

To test the hypothesis that in response to increased ventilatory demand, dynamic inspiratory pressure assistance better compensates for increased workload compared with static pressure support ventilation (PSV).

DESIGN

Randomized clinical crossover study.

SETTING

General intensive care u nits of a university hospital.

PATIENTS

Twelve patients with acute respiratory failure.

INTERVENTIONS

Patients received PSV, proportional assist ventilation (PAV), and PAV+ automatic tube compensation (ATC) in random order while maintaining mean inspiratory airway pressure constant. During each setting, ventilatory demand was increased by adding deadspace without ventilator readjustment.

MEASUREMENTS AND MAIN RESULTS

Cardiorespiratory, ventilatory, and work of breathing variables were assessed by routine monitoring plus pneumotachography; airway, esophageal, and abdominal pressure measurements; and nitrogen washout. After deadspace addition, tidal volume and end-expiratory lung volume increased similarly in all ventilatory modalities. Ventilator work, peak inspiratory flow, and maximum airway pressure increased significantly during PAV+ATC when compared with PSV after deadspace addition. However, increase in ventilator work did not result in a smaller increase in patients' work of breathing with elevated ventilatory demand during PAV+ATC (PSV 807 +/- 204 mJ/L, PAV 802 +/- 193 mJ/L, and PAV+ATC 715 +/- 202 mJ/L, p = .11). Increase in patients' work of breathing was mainly caused by a significantly higher resistive workload during PAV and PAV+ATC.

CONCLUSION

In patients with acute respiratory failure, dynamic inspiratory pressure assistance modalities are not superior to PSV with respect to cardiorespiratory function and inspiratory muscles unloading after increasing ventilatory demand. The latter might be explained by higher peak flows resulting in nonlinearly increased resistive workload that was incompletely compensated by PAV+ATC.

Livide Verf�rbung der Hand als unerw�nschtes Ereignis bei axill�rer Plexusan�sthesie

During axillary brachial plexus block for hand surgery, the axillary artery was accidentally punctured. After skin disinfection of the operation site a livid discoloration of the hand appeared. The initial intention of stopping surgery and performing an angiography for clarification of the suspicion of a vessel lesion was dismissed after recording the pulse at the wrist and all fingertips employing a pulsoximeter. Further investigation showed that the livid discoloration of the hand was a product of the interaction of the octenidin solution used for pre-operative hand disinfection with the polyvidone-iodine solution used for surgical skin disinfection. This case report shows that interactions of topically administered pharmaceuticals have to be taken into consideration. Lack of knowledge might lead to unnecessary and unjustified diagnostic procedures which imply additional costs and dangers for the patient.

Measurement of functional residual capacity by nitrogen washout during partial ventilatory support

OBJECTIVE

Evaluation of an open circuit multiple breath nitrogen washout (MBNW) technique for measurement of functional residual capacity (FRC) during partial ventilatory support using corrections for gas viscosity, sampling delay time, and re-inspired nitrogen.

DESIGN

Measurements in a lung model with known reference volume simulating spontaneous breathing and duplicate measurements in patients breathing spontaneously with partial ventilatory support. SETTING. Experimental laboratory and intensive care units of a university hospital.

PATIENTS

Eighteen patients with acute respiratory failure.

INTERVENTIONS

Change of FiO(2) from baseline to 1.0.

MEASUREMENTS AND MAIN RESULTS

FRC was measured by MBNW during spontaneous breathing with continuous positive airway pressure, pressure support ventilation, proportional assist ventilation, automatic tube compensation, and airway pressure release ventilation. In the lung model, repeated measurements at three volumes were done with all partial ventilatory support modalities, and baseline FiO(2 )was varied with one mode and FRC. The mean of differences between MBNW (FRC(MBNW)) and reference was 28 ml (1.6%), and the 2.SD-interval was 84 ml (4.9%) for all modes. Measurements up to a baseline FiO(2) of 0.8 showed differences of 5 ml (-0.3%) and the 2.SD-interval of 38 ml (2.2%) between reference and FRC(MBNW). In 18 patients, 66 duplicate measurements revealed a mean difference of 30 ml (0.9%) with a coefficient of repeatability of 358 ml (13%) independent of ventilatory mode and chronological order.

CONCLUSION

This study suggests that, using corrections for gas viscosity, sampling delay time, and re-inspired nitrogen, FRC can be determined with good repeatability in patients and good accuracy in a lung model during partial ventilatory support.

[Proportional assist ventilation combined with automatic tube compensation. A promising concept of augmented spontaneous breathing?]

The combination of proportional assist ventilation (PAV) and automatic tube compensation (ATC) is a promising concept for partial ventilatory support. In contrast to conventional pressure support ventilation (PSV), PAV+ATC provides dynamic pressure support depending on the patient's initial inspiratory effort. PAV+ATC should selectively unload the respiratory muscles from the additional workload imposed by increased respiratory system resistance and elastance as well as by endotracheal tube resistance. Patients have the ability to modify the tidal volume in response to changes in ventilatory demand, thereby improving patient-ventilator interaction and breathing comfort when compared with PSV. However, since routine measurements of respiratory mechanics during augmented spontaneous breathing are currently unavailable but would be necessary for setting the support level as a function of respiratory system mechanics during PAV, this mode cannot yet be generally recommended for routine clinical use.