Major elective abdominal surgery acutely impairs lower limb muscle pyruvate dehydrogenase complex activity and mitochondrial function

The effects of major abdominal surgery on skeletal muscle mitochondrial respiration in relation to systemic redox status and cardiopulmonary fitness

More complex surgeries are being performed in increasingly sicker patients, resulting in a greater burden of postoperative morbidity. Delineating the metabolic and bioenergetic changes that occur in response to surgical stress may further our understanding about how humans respond to injury and aid the identification of resilient and frail phenotypes. Skeletal muscle biopsies were taken from patients undergoing hepato-pancreatico-biliary surgery at the beginning and end of the procedure to measure mitochondrial respiration and thiol status. Blood samples were taken at the same timepoints to measure markers of inflammation and systemic redox state. A sub-group of patients underwent cardiopulmonary exercise testing prior to surgery, and were assigned to two groups according to their oxygen consumption at anaerobic threshold (≤10 and >10 mL/kg/min) to determine whether redox phenotype was related to cardiorespiratory fitness. No change in mitochondrial oxidative phosphorylation capacity was detected. However, a 26.7% increase in LEAK (uncoupled) respiration was seen after surgery (P = 0.03). Free skeletal muscle cysteine also increased 27.0% (P = 0.003), while S-glutathionylation and other sulfur and nitrogen-based metabolite concentrations remained unchanged. The increase in LEAK was 200% greater in fit patients (P = 0.004). Baseline plasma inflammatory markers, including TNF-⍺ and IL-6 were greater in unfit patients, 96.6% (P = 0.04) and 111.0% (P = 0.02) respectively, with a 58.7% lower skeletal muscle nitrite compared to fit patients. These data suggest that oxidative phosphorylation is preserved during the acute intraoperative period. Increase in free cysteine may demonstrate the muscle's response to surgical stress to maintain redox balance. The differences in tissue metabolism between fitness groups suggests underlying metabolic phenotypes of frail and resilient patients. For example, increased LEAK in fitter patients may indicate mitochondrial adaptation to stress. Higher baseline measurements of inflammation and lower tissue nitrite in unfit patients, may reflect a state of frailty and susceptibility to postoperative demise.

Nascent to novel methods to evaluate malnutrition and frailty in the surgical patient

Preoperative nutrition status is an important determinant of surgical outcomes, yet malnutrition assessment is not integrated into all surgical pathways. Given its importance and the high prevalence of malnutrition in patients undergoing surgical procedures, preoperative nutrition screening, assessment, and intervention are needed to improve postoperative outcomes. This narrative review discusses novel methods to assess malnutrition and frailty in the surgical patient. The Global Leadership Initiative for Malnutrition (GLIM) criteria are increasingly used in surgical settings although further spread and implementation are strongly encouraged to help standardize the diagnosis of malnutrition. The use of body composition (ie, reduced muscle mass) as a phenotypic criterion in GLIM may lead to a greater number of patients identified as having malnutrition, which may otherwise be undetected if screened by other diagnostic tools. Skeletal muscle loss is a defining criterion of malnutrition and frailty. Novel direct and indirect approaches to assess muscle mass in clinical settings may facilitate the identification of patients with or at risk for malnutrition. Selected imaging techniques have the additional advantage of identifying myosteatosis (an independent predictor of morbidity and mortality for surgical patients). Feasible pathways for screening and assessing frailty exist and may determine the cost/benefit of surgery, long-term independence and productivity, and the value of undertaking targeted interventions. Finally, the evaluation of nutrition risk and status is essential to predict and mitigate surgical outcomes. Nascent to novel approaches are the future of objectively identifying patients at perioperative nutrition risk and guiding therapy toward optimal perioperative standards of care.

Prehabilitation: high-quality evidence is still required

Prehabilitation comprises multidisciplinary healthcare interventions, including exercise, nutritional optimisation, and psychological preparation, which aim to dampen the metabolic response to surgery, shorten the period of recovery, reduce complications, and improve the quality of recovery and quality of life. This editorial evaluates the potential benefits and limitations of and barriers to prehabilitation in surgical patients. The results of several randomised clinical trials and meta-analyses on prehabilitation show differing results, and the strength of the evidence is relatively weak. Heterogeneity in patient populations, interventions, and outcome measures, with a wide range for compliance, contribute to this variation. Evidence could be strengthened by the conduct of large-scale, appropriately powered multicentre trials that have unequivocal clinically relevant and patient-centric endpoints. Studies on prehabilitation should concentrate on recruiting patients who are frail and at high risk. Interventions should be multimodal and exercise regimens should be tailored to each patient's ability with longitudinal measurements of impact.

Pyruvate as a Potential Beneficial Anion in Resuscitation Fluids

There have been ongoing debates about resuscitation fluids because each of the current fluids has its own disadvantages. The debates essentially reflect an embarrassing clinical status quo that all fluids are not quite ideal in most clinical settings. Therefore, a novel fluid that overcomes the limitations of most fluids is necessary for most patients, particularly diabetic and older patients. Pyruvate is a natural potent antioxidant/nitrosative and anti-inflammatory agent. Exogenous pyruvate as an alkalizer can increase cellular hypoxia and anoxia tolerance with the preservation of classic glycolytic pathways and the reactivation of pyruvate dehydrogenase activity to promote oxidative metabolism and reverse the Warburg effect, robustly preventing and treating hypoxic lactic acidosis, which is one of the fatal complications in critically ill patients. In animal studies and clinical reports, pyruvate has been shown to play a protective role in multi-organ functions, especially the heart, brain, kidney, and intestine, demonstrating a great potential to improve patient survival. Pyruvate-enriched fluids including crystalloids and colloids and oral rehydration solution (ORS) may be ideal due to the unique beneficial properties of pyruvate relative to anions in contemporary existing fluids, such as acetate, bicarbonate, chloride, citrate, lactate, and even malate. Preclinical studies have demonstrated that pyruvate-enriched saline is superior to 0.9% sodium chloride. Moreover, pyruvate-enriched Ringer’s solution is advantageous over lactated Ringer’s solution. Furthermore, pyruvate as a carrier in colloids, such as hydroxyethyl starch 130/0.4, is more beneficial than its commercial counterparts. Similarly, pyruvate-enriched ORS is more favorable than WHO-ORS in organ protection and shock resuscitation. It is critical that pay attention first to improving abnormal saline with pyruvate for ICU patients. Many clinical trials with a high dose of intravenous or oral pyruvate were conducted over the past half century, and results indicated its effectiveness and safety in humans. The long-term instability of pyruvate aqueous solutions and para-pyruvate cytotoxicity is not a barrier to the pharmaceutical manufacturing of pyruvate-enriched fluids for ICU patients. Clinical trials with sodium pyruvate-enriched solutions are urgently warranted.

Unresolved issues in perioperative nutrition: A narrative review

Surgical patients are at an increased risk of negative outcomes if they are malnourished or at risk of malnutrition preoperatively. Optimisation of nutritional status should be a focus throughout the perioperative continuum to promote improved surgical outcomes. Enhanced Recovery after Surgery (ERAS) protocols are increasingly applied in the surgical setting but are not yet widespread. This narrative review focused on areas of perioperative nutrition that are perceived as controversial or are lacking in agreement. A search for available literature was conducted on 1 March 2022 and relevant high-quality articles published since 2015 were considered for inclusion. Most malnutrition screening tools are not specific to the surgical population except for the Perioperative Nutrition Screen (PONS) although more large-scale initiatives are needed to improve the prevalence of preoperative nutrition screening. Poor muscle health is common in patients with malnutrition and further exacerbates negative health outcomes indicating that prevention, detection and treatment is of high importance in this population. Although a lack of consensus remains for who should receive preoperative nutritional therapy, evidence suggests a positive impact on muscle health. Additionally, postoperative nutritional support benefits surgical outcomes, with some patients requiring enteral and/or parenteral feeding routes and showing benefit from immunonutrition. The importance of nutrition extends beyond the time in hospital and should remain a priority post-discharge. The impact of individual or personalised nutrition based on select patient characteristics remains to be further investigated. Overall, the importance of perioperative nutrition is evident in the literature despite select ongoing areas of contention.