Extracorporeal Membrane Oxygenation Physiological Factors Influence Pulse Oximetry and Arterial Oxygen Saturation Discrepancies

BACKGROUND

Cannulation strategy, vasopressors, and hemolysis are important physiological factors that influence hemodynamics in extracorporeal membrane oxygenation (ECMO). We hypothesized these factors influence the discrepancy between oxygen saturation measured by pulse oximetry (Spo2) and arterial blood gas (Sao2) in patients on ECMO.

METHODS

We retrospectively analyzed adults (aged ≥18 years) on venoarterial or venovenous ECMO at a tertiary academic ECMO center. Spo2-Sao2 pairs with oxygen saturation ≥70% and measured within 10 minutes were included. Occult hypoxemia was defined as Sao2 ≤88% with a time-matched Spo2 ≥92%. Adjusted linear mixed-effects modeling was used to assess the Spo2-Sao2 discrepancy with preselected demographics and time-matched laboratory variables. Vasopressor use was quantified by vasopressor dose equivalences.

RESULTS

Of 139 venoarterial-ECMO and 88 venovenous-ECMO patients, we examined 20,053 Spo2-Sao2 pairs. The Spo2-Sao2 discrepancy was greater in venovenous-ECMO (1.15%) vs venoarterial-ECMO (-0.35%, P < .001). Overall, 81 patients (35%) experienced occult hypoxemia during ECMO. Occult hypoxemia was more common in venovenous-ECMO (65%) than in venoarterial-ECMO (17%, P < .001). In linear mixed-effects modeling, Spo2 underestimated Sao2 by 9.48% in central vs peripheral venoarterial-ECMO (95% CI, -17.1% to -1.79%; P = .02). Higher vasopressor dose equivalences significantly worsened the Spo2-Sao2 discrepancy (P < .001). In linear mixed-effects modeling, Spo2 overestimated Sao2 by 25.43% in single lumen-cannulated vs double lumen-cannulated venovenous-ECMO (95% CI, 5.27%-45.6%; P = .03). Higher vasopressor dose equivalences and lactate dehydrogenase levels significantly worsened the Spo2-Sao2 discrepancy (P < .001).

CONCLUSIONS

Venovenous-ECMO patients are at higher risk for occult hypoxemia compared with venoarterial-ECMO. A higher vasopressor requirement and different cannulation strategies (central venoarterial-ECMO; single-lumen venovenous-ECMO) were significant factors for clinically significant Spo2-Sao2 discrepancy in both ECMO modes.

Risk Factors and Early Outcomes for Gastrointestinal Complications in Patients Undergoing Open Surgery for Type A Aortic Dissection

BACKGROUND

Gastrointestinal complications need to be paid more attention, especially in critically ill patients. The purpose of this study was to identify the risk factors and short-term outcomes of gastrointestinal complications after open surgery for type A aortic dissection.

METHODS

A retrospective single-institutional study including patients who underwent open surgery for type A aortic dissection during 2012-2020 was conducted. Univariate analysis and logistic regression analysis were used to identify risk factors associated with gastrointestinal complications. The related clinical outcomes were compared between the patients with and without gastrointestinal complications.

RESULTS

Among the 2746 patients, 150 developed gastrointestinal complications. The development of gastrointestinal complications contributed to the higher rate of mortality (P = .008), longer stay in the intensive care unit (P < .001), and longer hospital stay (P < .001). Logistic regression analysis showed that age (odds ratio [OR] 1.020; 95% confidence interval [CI] 1.005-1.057; P = .011), American Society of Anesthesiologists classification greater than grade III (OR 1.724; 95%CI 1.179-2.521, P = .005), pre-induction mean arterial pressure (OR 0.978; 95%CI 0.965-0.990, P = .001), aortic cross-clamp time (OR 1.012; 95%CI 1.005-1.019, P = .001), cardiopulmonary bypass time (OR 1.007; 95%CI 1.002-1.011, P = .002), and intraoperative transfusion of red blood cells (OR 1.214; 95%CI 1.122-1.314, P = .001) were independent risk factors for gastrointestinal complications.

CONCLUSIONS

The incidence of gastrointestinal complications after open surgery for type A aortic dissection was 5.5%, resulting in increased mortality and prolonged hospital stay. It is necessary to take suitable strategies to reduce the incidence of gastrointestinal complications.

Causal determinants of postoperative length of stay in cardiac surgery using causal graphical learning

OBJECTIVE

We aimed to learn the causal determinants of postoperative length of stay in cardiac surgery patients undergoing isolated coronary artery bypass grafting or aortic valve replacement surgery.

METHODS

For patients undergoing isolated coronary artery bypass grafting or isolated aortic valve replacement surgeries between 2011 and 2016, we used causal graphical modeling on electronic health record data. The Fast Causal Inference (FCI) algorithm from the Tetrad software was used on data to estimate a Partial Ancestral Graph (PAG) depicting direct and indirect causes of postoperative length of stay, given background clinical knowledge. Then, we used the latent variable intervention-calculus when the directed acyclic graph is absent (LV-IDA) algorithm to estimate strengths of causal effects of interest. Finally, we ran a linear regression for postoperative length of stay to contrast statistical associations with what was learned by our causal analysis.

RESULTS

In our cohort of 2610 patients, the mean postoperative length of stay was 219 hours compared with the Society of Thoracic Surgeons 2016 national mean postoperative length of stay of approximately 168 hours. Most variables that clinicians believe to be predictors of postoperative length of stay were found to be causes, but some were direct (eg, age, diabetes, hematocrit, total operating time, and postoperative complications), and others were indirect (including gender, race, and operating surgeon). The strongest average causal effects on postoperative length of stay were exhibited by preoperative dialysis (209 hours); neuro-, pulmonary-, and infection-related postoperative complications (315 hours, 89 hours, and 131 hours, respectively); reintubation (61 hours); extubation in operating room (-47 hours); and total operating room duration (48 hours). Linear regression coefficients diverged from causal effects in magnitude (eg, dialysis) and direction (eg, crossclamp time).

CONCLUSIONS

By using retrospective electronic health record data and background clinical knowledge, causal graphical modeling retrieved direct and indirect causes of postoperative length of stay and their relative strengths. These insights will be useful in designing clinical protocols and targeting improvements in patient management.

The Effectiveness of Early Enteral Nutrition on Clinical Outcomes in Critically Ill Sepsis Patients: A Systematic Review

The optimal timing of enteral nutrition (EN) in sepsis patients is controversial among societal guidelines. We aimed to evaluate the evidence of early EN's impact on critically ill sepsis patients' clinical outcomes. We searched the MEDLINE, Embase, CINAHL, Cochrane Library, ClinicalTrials.gov, and ICTRP databases on 10 March 2023. We included studies published after 2004 that compared early EN versus delayed EN in sepsis patients. We included randomized controlled trials (RCTs), non-RCTs, cohort studies, and case-control studies. Forest plots were used to summarize risk ratios (RRs), including mortality and mean difference (MD) of continuous variables such as intensive care unit (ICU) length of stay and ventilator-free days. We identified 11 eligible studies with sample sizes ranging from 31 to 2410. The RR of short-term mortality from three RCTs was insignificant, and the MD of ICU length of stay from two RCTs was -2.91 and -1.00 days (95% confidence interval [CI], -5.53 to -0.29 and -1.68 to -0.32). Although the RR of intestinal-related complications from one RCT was 3.82 (95% CI, 1.43 to 10.19), indicating a significantly higher risk for the early EN group than the control group, intestinal-related complications of EN reported in five studies were inconclusive. This systematic review did not find significant benefits of early EN on mortality in sepsis patients. Evidence, however, is weak due to inconsistent definitions, heterogeneity, risk of bias, and poor methodology in the existing studies.

When is enteral nutrition indicated?

Enteral nutrition (EN) is a vital component of nutrition around the world. EN allows for delivery of nutrients to those who cannot maintain adequate nutrition by oral intake alone. Common questions regarding EN are when to initiate and in what scenarios it is safe. The answers to these questions are often complex and require an evidence-based approach. The Board of Directors of the American Society for Parenteral and Enteral Nutrition (ASPEN) established an Enteral Nutrition Committtee to address the important questions surrounding the indications for EN. Consensus recommendations were established based on eight extremely clinically relevant questions regarding EN indications as deemed by the Enteral Nutrition Committee. These consensus recommendations may act as a guide for clinicians and stakeholders on difficult questions pertaining to indications for EN. This paper was approved by the ASPEN Board of Directors.

Improving nutrition practices for postoperative high-risk heart transplant and ventricular assist device implant patients in circulatory compromise: A quality improvement pre- and post-protocol intervention outcome study

BACKGROUND

Patients undergoing heart transplant (HT) and ventricular assist device (VAD) implant may experience intra- and postoperative complications requiring high-dose vasopressor agents and/or mechanical circulatory support. These complications increase the risk of nonocclusive bowel ischemia (NOBI) and inadequate enteral nutrition (EN) delivery, and guidance for this high-risk patient population is limited. To optimize nutrition support practices in this patient population at our institution, we created the High-Risk Nutrition Support Protocol (HRNSP) to improve nutrient delivery and promote safer EN practices in the setting of NOBI risk factors after HT and VAD implant.

METHODS

We developed and implemented a nutrition support protocol as a quality improvement (QI) initiative. Data were obtained before (n = 62) and after (n = 52) protocol initiation. We compared nutrition and clinical outcomes between the pre- and post-intervention groups.

RESULTS

Fewer calorie deficits (P < 0.001), fewer protein deficits (P < 0.001), a greater proportion of calorie/protein needs met (P < 0.001), zero NOBI cases (0%), and decreased intensive care unit (ICU) length of stay (LOS) (P = 0.005) were observed with 100% (n = 52 of 54) HRNSP implementation success. Increased use of parenteral nutrition did not increase central line-associated bloodstream infections (P = 0.46). There was no difference in hospital LOS (P = 0.44) or 90-day and 1-year mortality (P = 0.56, P = 0.35).

CONCLUSION

This single-center, QI pre- and post-protocol intervention outcome study suggests that implementing and adhering to a nutrition support protocol for VAD implant/HT patients with hemodynamic complications increases nutrient delivery and is associated with reduced ICU LOS and NOBI.

Early enteral nutrition and factors related to in-hospital mortality in people on extracorporeal membrane oxygenation

OBJECTIVES

There are concerns about adverse events related to early enteral nutrition (EN) in people receiving extracorporeal membrane oxygenation (ECMO). This was a retrospective study evaluating. This nutritional support of people receiving ECMO, factors that may confer benefits in outcomes.

METHODS

60 adults on ECMO who survived for more than 48 h were enrolled in the study. We evaluated energy and protein intake and the associations of the timing, adequacy, and route of nutrition with in-hospital mortality.

RESULTS

Thirty-three participants (55%) were successfully weaned off ECMO, and 30 (50%) survived. EN was initiated on day 2 of ECMO (interquartile range, 1-3), and the mean energy intake on day 7 of ECMO was 94.1% ± 41.8% of the energy requirement. Although early EN significantly decreased in-hospital mortality (hazard ratio, 0.413; 95% confidence interval, 0.174-0.984; P = 0.046), neither adequate energy intake (hazard ratio, 0.982; 95% confidence interval, 0.292-3.301; P = 0.977) nor EN-dominant nutritional support (hazard ratio, 0.394; 95% confidence interval, 0.138-1.128; P = 0.083) in the first week influenced survival.

CONCLUSIONS

Although adequate nutritional support and EN-dominant nutritional support were not associated with changes in outcome, early EN was associated with reduced in-hospital mortality. Therefore, even when EN is not the dominant route of nutritional support, early EN may be recommended for better outcomes in people on ECMO.

Nutrition Support After Cardiac Surgery: Lessons Learned From a Prospective Study

The importance of postoperative nutrition support (NS) has been poorly recognized in cardiac surgery. In this population, we aim to describe the delivery of NS, factors affecting calorie/protein delivery and NS-associated morbidity. From January 2015 to January 2017, we prospectively observed all cardiac surgery patients at a single institution who could not take nutrition orally, requiring postoperative NS, either enteral or parenteral, for the duration of NS up to 14 days. We compared outcomes to patients without NS and examined NS indications, factors affecting its delivery and its associated complications. Nine percent of patients (232/2603) required NS for a total of 1938 NS-days. The most common indication was mechanical ventilation. NS met 69% of daily caloric needs. On days when tube feeds (TFs) were held (mean of 13 hours), this decreased to 43%, compared to 96% when TFs were not held (P < 0.001). The most common reason for holding TFs was procedures. When TFs were supplemented with parenteral nutrition (TFs + PN), 86% of daily caloric needs were met. Even on days when TFs were held, this only dropped to 77% (TFs + PN), compared to 36% (TFs-only). By multivariable logistic regression, elemental and semielemental formulas, TF volume, and postpyloric feeds increased the risk of diarrhea, occurring in 28% of patients and 18% of TF-days. In cardiac surgery patients given postoperative NS, mortality and morbidity were an order of magnitude higher than those able to be fed orally. Enteral feeding delivered approximately two-thirds of needs, but PN supplementation dramatically improved this. Diarrhea was common, associated with the postpyloric route, increasing TF volume, and nonintact formula.