Nutrition and lung function in the critically ill patient

Metabolic Support in Acute Respiratory Distress Syndrome: A Narrative Review

Nutritional support for acute respiratory distress syndrome (ARDS) patients shares metabolic notions common to other critically ill conditions. Nevertheless, it generates specific concern regarding the primary limitation of oxygen supply and the complications of carbon dioxide elimination, as well as the significant metabolic alterations due to the body's response to illness. In the present narrative review, after briefly summarizing the pathophysiology of critical illness stress response and patients' metabolic requirements, we focus on describing the characteristics of metabolic and artificial nutrition in patients with acute respiratory failure. In patients with ARDS, several aspects of metabolism assume special importance. The physiological effects of substrate metabolism are described for this setting, particularly regarding energy consumption, diet-induced thermogenesis, and the price of their clearance, transformation, and storage. Moreover, we review the possible direct effects of macronutrients on lung tissue viability during ARDS. Finally, we summarize the noteworthy characteristics of metabolic control in critically ill patients with ARDS and offer a suggestion as to the ideal methods of metabolic support for this problem.

Markers of respiratory function response to high-carbohydrate and high-fat intake in patients with lung diseases: a systematic review with meta-analysis of randomized clinical trials

BACKGROUND

Macronutrients can differently affect respiratory function markers such as VO₂ , VCO₂ , PaO₂ , PaCO₂ and respiratory quotients (RQ), but systematic appraisal of the evidence on randomized clinical trials (RCTs) is lacking.

OBJECTIVE

To compare the response of respiratory function markers to high-carbohydrate and high-fat intake in patients with lung diseases.

METHODS

Systematic review conducted according to Cochrane Collaboration recommendations, reported following PRISMA 2020. PubMed, EMBASE, Scopus, and Cochrane CENTRAL were searched up to July/2021. Two reviewers selected the RCTs and extracted the data. Risk of bias and the certainty of evidence were assessed by RoB 2 and GRADE, respectively. Statistical and graphical data guided the publication bias investigation. Meta-analyses were conducted.

RESULTS

We included 14 RCTs (362 participants), four of which were parallel. Most studies included patients with COPD. High-fat intake decreased VCO₂ [MD = -35.89(95%CI -45.24; -26.21) ml/min; I²=0%], VO₂ [MD= -29.30(95% CI -40.94, -17.66) ml/min; I² = 0%], PaCO₂ [MD = -4.62(95%CI -7.67; -1.58) mmHg; I²=84%], and RQ [MD = -0.08(95%CI -0.09; -0.06); I² = 0%] in the subset of parallel RCTs. In crossover RCTs, there was generally no evidence of effect except for a greater decrease in RQ [MD = -0.09(95%CI -0.12; -0.02); I² = 96%] in favor of high fat intake.

CONCLUSION

High-fat intake resulted in greater reductions ​​of VCO₂ , VO₂ , PaCO₂ , and RQ in adult patients with lung diseases. The certainty of the evidence is very low/ low, and it precludes a specific recommendation on macronutrients contribution to energy intake of these patients. This article is protected by copyright. All rights reserved.

Assessment of Metabolic and Nutritional Imbalance in Mechanically Ventilated Multiple Trauma Patients: From Molecular to Clinical Outcomes

The critically ill polytrauma patient is characterized by a series of metabolic changes induced by inflammation, oxidative stress, sepsis, and primary trauma, as well as associated secondary injuries associated. Metabolic and nutritional dysfunction in the critically ill patient is a complex series of imbalances of biochemical and genetic pathways, as well as the interconnection between them. Therefore, the equation changes in comparison to other critical patients or to healthy individuals, in which cases, mathematical equations can be successfully used to predict the energy requirements. Recent studies have shown that indirect calorimetry is one of the most accurate methods for determining the energy requirements in intubated and mechanically ventilated patients. Current research is oriented towards an individualized therapy depending on the energy consumption (kcal/day) of each patient that also takes into account the clinical dynamics. By using indirect calorimetry, one can measure, in real time, both oxygen consumption and carbon dioxide production. Energy requirements (kcal/day) and the respiratory quotient (RQ) can be determined in real time by integrating these dynamic parameters into electronic algorithms. In this manner, nutritional therapy becomes personalized and caters to the patients’ individual needs, helping patients receive the energy substrates they need at each clinically specific time of treatment.

Caloric intake and the fat-to-carbohydrate ratio in hypercapnic acute respiratory failure: Post-hoc analysis of the PermiT trial

BACKGROUND

The effect of moderate caloric enteral intake in critically ill patients with hypercapnic acute respiratory failure (HCARF) is unclear. We studied the impact of permissive underfeeding (PUF) compared with standard feeding (SF) on various HCARF outcomes.

MATERIALS AND METHODS

The PermiT trial randomized 894 patients to either PUF (40-60% caloric requirement) or SF (70-100% requirement) with similar protein intake and found no difference in mortality, mechanical ventilation (MV) duration and ventilator-free days. In this post-hoc study, we restricted analysis to mechanically-ventilated patients with HCARF (PaCO₂ >45 mmHg on the first two study days) and assessed the impact of trial interventions and fat-to-carbohydrate ratio on outcomes.

RESULTS

One-hundred-twenty patients had HCARF (59 PUF and 61 SF, age 53.7 ± 17.8 years, body mass index 31.1 ± 11.2 kg/m², Acute Physiology and Chronic Health Evaluation II score 21.7 ± 7.1 and day-1 PaCO₂ 61 ± 16 mmHg). Caloric intake was 815 ± 270 kcal/day in PUF group and 1289 ± 407 kcal/day in SF group. The two groups had similar PaCO₂ levels during ICU stay. The 90-day mortality (33.9% versus 35.6%, p = 0.85), MV duration (10.7 ± 6.8 versus 11.1 ± 8.1 days, p = 0.56) and ventilator-free days (52.9 ± 38.6 versus 51.2 ± 38.0 days, p = 0.80) were also similar in PUF and SF groups, respectively. Ventilator-free days and 90-day mortality were similar when the fat-to-carbohydrate ratio was < or ≥ the median value (0.73) in all patients and in PUF and SF groups.

CONCLUSIONS

In patients with HCARF, SF and PUF were associated with similar PaCO₂, MV duration, ventilator-free days and mortality. Fat-to-carbohydrate ratio was not associated with mortality or ventilator-free days.

TRIAL REGISTRATION

ISRCTN Registry: ISRCTN68144998.

Cilostazol administration with combination enteral and parenteral nutrition therapy remarkably improves outcome after subarachnoid hemorrhage

OBJECTIVE

In order to prevent cerebral vasospasm (VS) following aneurysmal subarachnoid hemorrhage (SAH), we introduced combined enteral nutrition (EN) and parenteral nutrition (PN) with oral cilostazol administration to the postoperative patient after SAH and investigated the effect on VS.

METHODS

After aneurysmal SAH, 130 postoperative patients were enrolled in this study between April 2008 and March 2012. The patients enrolled before April 2010 were treated by conventional therapy (control group). The patients enrolled after April 2010 were administrated cilostazol 200 mg/day and received EN and PN simultaneously (combined group).

RESULTS

The combined group consisted of 62 patients and the control group of 68 patients. Angiographic VS occurred in 33.9 % (n = 21) of the combined group and in 51.5 % (n = 35) of the control group (p = 0.051, Fisher exact test). The incidence of symptomatic VS was significantly lower in the combined group (p = 0.001). The incidence of new cerebral infarctions was also significantly lower in the combined group (p = 0.0006). Clinical outcome at discharge was also significantly better in the combined group than in control group (p = 0.031).

CONCLUSIONS

Cilostazol administration with combination EN and PN is remarkably effective in preventing cerebral VS after aneurysmal SAH.

Bench-to-bedside review: carbon dioxide

Carbon dioxide is a waste product of aerobic cellular respiration in all aerobic life forms. PaCO2 represents the balance between the carbon dioxide produced and that eliminated. Hypocapnia remains a common - and generally underappreciated - component of many disease states, including early asthma, high-altitude pulmonary edema, and acute lung injury. Induction of hypocapnia remains a common, if controversial, practice in both adults and children with acute brain injury. In contrast, hypercapnia has traditionally been avoided in order to keep parameters normal. More recently, advances in our understanding of the role of excessive tidal volume has prompted clinicians to use ventilation strategies that result in hypercapnia. Consequently, hypercapnia has become increasingly prevalent in the critically ill patient. Hypercapnia may play a beneficial role in the pathogenesis of inflammation and tissue injury, but may hinder the host response to sepsis and reduce repair. In contrast, hypocapnia may be a pathogenic entity in the setting of critical illness. The present paper reviews the current clinical status of low and high PaCO2 in the critically ill patient, discusses the insights gained to date from studies of carbon dioxide, identifies key concerns regarding hypocapnia and hypercapnia, and considers the potential clinical implications for the management of patients with acute lung injury.

Tight glycemic control does not affect asymmetric-dimethylarginine in septic patients

OBJECTIVE

We investigated whether preventing hyperglycemia in septic patients affected the plasma concentration of asymmetric-dimethylarginine and if this was associated with clinical benefit.

DESIGN

A prospective, multicenter, randomized, controlled, clinical study.

SETTING

Intensive care units (ICU) in three university hospitals.

PATIENTS

A total of 72 patients admitted for severe sepsis or septic shock, who stayed at least 3 days in the ICU. At admission the patients were assigned to receive either tight or conventional glycemic control.

INTERVENTIONS

Determination of circulating levels of asymmetric-dimethylarginine, arginine, interleukin-6, C-reactive-protein and tumor-necrosis-factor-alpha.

MEASUREMENTS AND RESULTS

Blood was sampled at admission (no differences between groups), and on the 3rd, 6th, 9th, and 12th (T12) days. Sequential organ failure assessment was scored at each sampling time. All the data were analyzed on an intention-to-treat basis. The control and treatment groups received the same energy intake, glycemia (110.4 +/- 17.3 vs. 163.0 +/- 28.9 mg/dL, P < 0.001) and insulin (P = 0.02) supply differed. No differences were found in high plasma levels of asymmetric-dimethylarginine (P = 0.812) at any time during the ICU stay. The clinical course, as indicated by markers of inflammation, average and maximum organ failure score, ICU stay and ICU and 90-day mortality, was the same.

CONCLUSIONS

Intensive insulin treatment, while achieving glucose control, did not reduce asymmetric-dimethylarginine in high-risk septic patients fed with no more than 25 kcal/kg per day to limit ventilatory demand and to simplify glucose control.

DESCRIPTOR

45 (SIRS/sepsis: clinical studies).

Is it now time to promote mixed enteral and parenteral nutrition for the critically ill patient?

BACKGROUND

Intensive care outcome measured by morbidity and mortality is altered in the severely malnourished ICU patient, and nutritional support of the critically ill is accepted as a standard of care. Current recommendations suggest starting enteral feeding as soon as possible whenever the gastrointestinal tract is functioning. The disadvantage of enteral support is that inadequate energy and protein intake can occur. The present commentary focuses on some recent findings regarding the nutritional support of critically ill patients and proposes to promote mixed nutrition support by enteral nutrition (EN), and by parenteral nutrition (PN) whenever EN is insufficient.

RECENT FINDINGS

An increasing nutrition deficit during a long ICU stay is associated with increased morbidity (increased infection rate or impaired wound healing). Evidence shows that EN can result in underfeeding and that nutrition goals are reached only after 5-7 days. Contrary to former beliefs, recent meta-analyses of studies in the ICU showed that PN is not related to excess mortality but may even be associated with improved survival.

CONCLUSIONS

Optimising the increased substrate requirement for the critically ill by initiating timely nutrition support and ensuring tight glycaemic control with insulin is now considered central for improved intensive care outcomes. Supplemental PN combined with EN could be an effective alternative to achieve 100% of energy and protein targets at day 4, when EN alone fails to achieve goals greater than 60% by day 3. Whether such combined nutrition support provides additional benefit on overall outcome has to be ascertained in further studies.

Nutrition given to critically ill patients during high level/complex care (on Italian ICUs)

BACKGROUND & AIMS

Within a prospective study on costs in 45 Italian intensive units we reviewed nutrition support practice given during critical illness.

METHODS

From June to October 1999, patients with an ICU stay longer than 47 h were studied. Nutrition (i.e. fasting, parenteral, enteral and mixed) and calorie supply by the enteral route were monitored during the first consecutive days (up to seven) of invasive support of organ failure (high-care).

RESULTS

388 patients received high-care for at least 1 day, 200 patients had seven consecutive high-care-days. Some form of nutrition was given in 90.7% of patients, 9.3% were never fed (25.8% of the cardiac patients). Parenteral nutrition was given in 13.9% of patients (78.9% of the abdominal surgery patients), 39.7% received only enteral nutrition, and 36.4% received mixed nutrition. Finally, 77.1% of the patients received nutrient by gut. Nutrition was given in 78.5% of 2115 collected days, 44.1% of the first high-care-days and 93.5% of the 7th days were positive for nutrition. Enteral calorie load on the first day was similar for enteral and mixed nutrition (range 8-14 kcal/kg), it was higher for exclusive enteral nutrition between the 4th and the 7th day (15-19 vs. 11-14 kcal/kg). It differed according to diagnosis group.

CONCLUSIONS

In Italian ICUs, in complex critically ill patients, nutrition is consistently given in critical illness, gut is widely used except in abdominal surgery patients.