F1000Research F1000Research 2046-1402 F1000 Research Limited London, UK 10.12688/f1000research.52287.1 Systematic Review Articles Factors related to loss of appetite in postoperative cardiac surgery patients: A systematic review

[version 1; peer review: 2 approved with reservations]

 Prasankok Channarong Conceptualization Data Curation Formal Analysis Investigation Methodology Project Administration Resources Software Validation Visualization Writing – Original Draft Preparation Writing – Review & Editing https://orcid.org/0000-0001-7815-012X 1 Banharak Samoraphop Conceptualization Data Curation Formal Analysis Funding Acquisition Investigation Methodology Project Administration Resources Software Supervision Validation Visualization Writing – Original Draft Preparation Writing – Review & Editing https://orcid.org/0000-0001-8315-0263 a 2 Nursing Department, Queen Sirikit Heart Center of the Northeast, Khon Kaen University, Khon Kaen, Thailand, 40002, Thailand Gerontological Nursing Department, Faculty of Nursing, Khon Kaen University, Khon Kaen, Thailand, 40002, Thailand sbanharak@kku.ac.th

No competing interests were disclosed.

 6 5 2021 2021 10 350 27 4 2021 Copyright: © 2021 Prasankok C and Banharak S 2021 This is an open access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Background: Postoperative cardiac surgery patients often experience appetite loss. Although nutritional status is known to be associated with time of recovery, functional status, and length of stay, less is known about factors related to patient’s loss of appetite after cardiac surgery. This review aimed to identify and understand factors related to loss of appetite in postoperative cardiac surgery patients, systematic review with narrative summary design was applied. Data sources including CINAHL, SCOPUS, PubMed, ProQuest, ScienceDirect, ThaiLIS, ThaiJo, and E-Thesis were searched without restriction on publication year through August 2020.

Methods: We conducted the review following the Joanna Briggs Institute methodology, using the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) checklist to categorize methodological quality and the PRISMA flow diagram to record the studies’ factors.

Results: Six studies reported one or more of 16 factors related to loss of appetite: older age, sex (female), illiteracy, history of chronic disease, not knowing someone in health field, pain score ≥ 7, pain medications containing codeine, constipation, depression, heart-lung machine ≥ 120 minutes, preoperative serum creatinine levels ≥ 179 µmol/L, emergency surgery, perfusion pressure ≤ 40 mmHg, low cardiac output syndrome, mechanical ventilation ≥ 96 hours, and a New York Heart Association class III and IV.

Conclusion: The small number of publications restrict our conclusions. Future research should focus on multiple factors related to appetite loss in postoperative cardiac surgery patients. Additional research will provide a foundation for evidence-based interventions to reduce appetite loss and improve patient nutritional status after cardiac surgery. Nurses and other health professionals should assess postoperative cardiac surgery patients for the presence of the 16 significant factors. To promote patients’ nutritional status, there should be evidence-based practice guidelines on the management of postoperative symptoms such as pain management, treatment of constipation, and reduction of emotional stress and depression.

Protocol registration: PROSPERO Registration Number CRD42021234615

 anorexia cardiac surgery heart surgery loss of appetite poor appetite systematic review Khon Kaen University RGS64-003 FM64-003 This work was financially supported by the Research and Training Center of Enhancing Quality of Life of Working Age People, Faculty of Nursing, Khon Kaen University (Grant Number RGS64-003) and Research and Graduate Studies, Khon Kaen University (Grant Number FM64-003). Appreciation is extended to these research and training centers for making our research possible. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Introduction

Heart disease is one of the leading causes of death in both developed and developing countries 1 . Although treatment depends on severity and types of heart disease, first line approaches include lifestyle changes involving nutrition, exercise, and medication. As patients’ symptoms worsen or complications increase, cardiac surgery often becomes the next treatment of choice 1 .

There are various types of cardiac surgery. These include coronary artery bypass graft, valve replacement and repair, great vessel surgery, and septum repair for those with congenital heart disease. Most of these surgeries require the use of the heart-lung machine as a cardiopulmonary bypass to take over the function of the heart and lungs during surgery to help surgeons repair a diseased heart’s malfunctioning. Because there have been adverse effects from using the heart-lung machine on the various body systems, an off-pump coronary artery bypass technique was developed as an alternative 2 . Nevertheless, the cardiopulmonary bypass remains widely used during open heart surgery. Prevention and management of possible deleterious effects from its use require ongoing assessment.

 Background

Alterations in postoperative physiological/psychological functioning contribute to loss of appetite. Surgery and the use of the heart-lung machine cause injuries in tissues and peripheral nerves that can lead to a nociceptive and inflammatory response, causing prostaglandins, bradykinins, and substance P to become increased that produces physical pain 3 . Postoperative pain and the use of the heart-lung machine are stressors that produce a physiological response such as the systemic inflammatory response syndrome 3 . The syndrome is a disturbance in the balance of the coagulation system that decreases the production of platelets and fibrinogen with increases in prothrombin time, leading to a higher risk of postoperative bleeding 4 . The immune system responds by decreasing the polymorphonuclear neutrophils and also macrophages in the lungs, which heighten the risk of infections, including pneumonia 5 . Cardiac surgery also intensifies catabolism and insulin resistance, resulting in higher blood sugar levels in both patients with and without a history of diabetes 6 . These factors directly and indirectly disturb the postoperative physiological/psychological interconnections to produce a loss of appetite and a nutritional imbalance 7 .

Food consumption behaviors change when patients consume small volumes of food, coupled with physical decline, less body movement/mobility, depression, and postoperative stress. Ścisło et al. (2019) found that after the cardiac surgery, 50% of patients had loss of appetite with an increased risk of poor nutrition, 35.4% had postoperative complications, and 10% had a decreased body mass index (BMI) 8 . The study affirmed that a decrease in BMI after surgery is associated with postoperative complications 9 . Chermesh et al. (2014) found similarly that poor nutritional status increases the severity and number of complications in postoperative patients 10 . Ringaitienė et al. (2016) reported that recovery is delayed in patients who have a loss of appetite and consume less food, causing longer hospitalizations 11 . Based on clinical experiences in caring for patients who had undergone cardiac surgery, we observed that some patients had decreased appetite, difficulty eating, ate less or had early satiety, and suffered bouts of nausea and vomiting. We further observed that these same postoperative cardiac surgical patients tended to have a late recovery, longer duration of hospitalization, and poorer prognosis than others without the symptoms. To the best of our knowledge, we found no literature that summarized and explained our observations. Therefore, the purpose of this systematic review of the literature was to contribute to a body of knowledge by focusing on all known factors related to loss of appetite in postoperative cardiac surgery patients. Understanding these factors will provide a foundation that is necessary to support nursing practice of cardiac surgical patients and inform future researchers what further aspects of loss of appetite need to be studied.

 Purpose

The purpose of this review was to systematically identify and understand the collective factors related to loss of appetite in postoperative cardiac surgery patients as found in published research.

 Methods Design

We followed the systematic review process with narrative summary as prescribed by the Joanna Briggs Institute (JBI) methodology by formulating the review question, defining the inclusion and exclusion criteria, developing the search strategy, locating and selecting studies, assessing their quality, extracting data, and analyzing and interpreting the results 12 . Moreover, the protocol for systematic review was registered at PROSPERO on February 1, 2021 and registration number was CRD42021234615.

 Search methods

We searched CINAHL, SCOPUS, PubMed, ProQuest, ScienceDirect, ThaiLIS, ThaiJo, and E-Thesis databases and used snowballing through reference lists of defined studies. The search for both English and Thai published papers was made without restriction on publication year through August 2020. The search strategy used the keywords “cardiac surgery” OR “open-heart surgery” AND “poor appetite” OR “loss of appetite” OR “decreased appetite” OR “change in appetite” OR “anorexia.” The selection of studies was made based on the following inclusion criteria: (a) research in humans related to cardiac surgery; (b) results about factors related to loss of appetite in postoperative cardiac surgery patients; (c) patients aged 18 years and older; and (d) published in the English or Thai language.

 Search outcomes

There were 5,774 original studies from the databases and two from hand searches. The winnowing process began with deduplication, which left 3,320 studies. Only 74 studies had full-text availability, of which 68 were excluded because they did not fully meet the inclusion criteria. As a result, six empirical research articles remained for appraisal. Figure 1 displays the PRISMA flow diagram of the information flow during the review process.

Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) Flowchart of the Review Process. Quality appraisal

We individually reviewed the six selected articles using the standardized critical appraisal instrument from the JBI for analytical cross-sectional studies 13 . The studies were required to meet a positive response (i.e., “yes”) on a minimum of four of the eight questions on the critical appraisal tool. Methodological quality was grouped into the four categories of very low, low, moderate, and high quality.

Data abstraction

On the JBI data extraction form (Aromataris & Munn, 2018) 12 , we recorded the studies’ authors, study designs, settings, participants, levels of evidence certainty and methodological quality, types of surgery, times of outcomes measuring, and factors related to loss of appetite. Prior to starting the review, we practiced article screening, data extraction, and quality assessment with two other researchers who independently verified that the process and results we had undertaken were accurate. If there were incongruent opinions during the actual review process, we reached consensus in mutual discussion.

 Synthesis

Extraction of quantitative data to conduct meta-analysis was not possible due to the heterogeneity of the study population, different types of cardiac surgery, outcome measures, and data analysis across the studies. The findings have been presented and discussed in tabular and narrative form to aid the data presentation.

Results

Six research articles met the inclusion criteria 14– 19 . They were all descriptive studies. Five had a moderate level of quality, and one had a high level of quality ( Table 1 & Table 2). Two studies were published before the year 2000 16, 17 , and four were published on or after 2000 14, 15, 18, 19 . Patients in five studies had undergone coronary artery bypass graft surgery 14, 16– 19 ; patients in three studies had undergone valve surgery 15, 16, 19 ; and patients in one study had both a septum repair for congenital heart disease and a repair of the aorta 19 . The surgeries reported in five studies required cardiopulmonary bypass 14– 16, 18, 19 , whereas one study did not specify its use 17 . Although five studies addressed patients postoperatively and after-discharge 14– 18 , one study described the preoperative, operative, and postoperative phases 19 ( Table 3).

The results of critical appraisal for the selected six analytical cross-sectional studies.
Critical Appraisal Checklist for Analytical Cross-sectional Studies (Joanna Briggs Institute) 13
Studies Were the criteria for inclusion in the sample clearly defined? Were the study subjects and the setting described in detail? Was the exposure measured in a valid and reliable way? Were objective, standard criteria used for measurement of the condition? Were confounding factors identified? Were strategies to deal with confounding factors stated? Were the outcomes measured in a valid and reliable way? Was appropriate statistical analysis used? scoring Overall appraisal (include)
Grap et al., 1996 16 √ √ √ √ - - √ √ 6/8 √
King & Parrinello, 1988 17 √ √ √ √ - - √ √ 6/8 √
Corrêa & Cruz, 2000 15 √ √ √ √ √ √ √ √ 8/8 √
Miller & Grindel, 2004 18 √ √ √ √ - - √ √ 6/8 √
Zhang et al., 2009 19 √ √ √ √ - - √ √ 6/8 √
Ammouri et al., 2016 14 √ √ √ √ - - √ √ 6/8 √
Grading results of the six selected studies from the quality assessment of the evidence by GRADE guideline <sup> <xref ref-type="bibr" rid="ref-13">13</xref> </sup>.
Quality Assessment of the Evidence by GRADE Guideline
No. a Risk of bias (confounding factors, missing data, adherence measurement) b Precision (statistical certainty, amount of information on a certain factor how precisely an object of study is measured) c Directness (extent to which the people, interventions, and outcome measures are similar to those of interest, confident results come from the direct evidence) d Consistency (relevant measurement application where several items that propose to measure the same general construct produce similar scores, no overlapping and missing, statistical significance) Certainty of evidence
Low Unclear High Precise Imprecise Direct Indirect Consistent Inconsistent
Grap et al., 1996 16 √ √ √ √ Moderate
King & Parrinello, 1988 17 √ √ √ √ Moderate
Corrêa & Cruz, 2000 15 √ √ √ √ High
Miller & Grindel, 2004 18 √ √ √ √ Moderate
Zhang et al., 2009 19 √ √ √ √ Moderate
Ammouri et al., 2016 14 √ √ √ √ Moderate

a = Risk of bias; b = Precision; c = Directness; d = Consistency

GRADE Working Group Grades of Evidence for certainty of evidence

High: The research provides a very good indication of the likely effect. The likelihood that the effect will be substantially different is low.

Moderate: The research provides a good indication of the likely effect. The likelihood that the effect will be substantially different is moderate.

Low: The research provides some indication of the likely effect. The likelihood that it will be substantially different (a large enough difference that it might have an effect on a decision) is high.

Very low: The research does not provide a reliable indication of the likely effect. The likelihood that the effect will be substantially different (a large enough difference that it might have an effect on a decision) is very high.

 A summary of the reviewed studies and factors related to poor appetite in postoperative cardiac surgery patients.
Authors Study Design Setting Participants Level, Certainty of Evidence and Methodological Quality † Types of Surgery Time of Outcomes Measured Factors Related to Loss of Appetite
Grap et al., 1996 16 Observational analytical study without a control group A large university medical center 34 Level 3.e ⊕⊕⊕◯ Moderate a (6/8) Coronary artery bypass graft surgery/None After discharge -  Constipation -  A pain medication containing codeine
King & Parrinello, 1988 17 Observational analytical study without a control group Two medical school hospitals 122 Level 3.e ⊕⊕⊕◯ Moderate a (6/8) Coronary artery bypass graft surgery and valve surgery/ Cardio-pulmonary bypass surgery After discharge -  Depression was correlated with poor appetite at 2 nd and 6 th weeks after discharge.
Corrêa & Cruz, 2000 15 Observational analytical study: cohort study Not available 80 Level 3.c ⊕⊕⊕⊕ High (8/8) Heart Surgery/Cardio- pulmonary bypass surgery Postoperative -  Pain score ≥7 was related to loss of appetite after surgery
Miller & Grindel, 2004 18 Observational analytical study without a control group University hospital 102 Level 3.e ⊕⊕⊕◯ Moderate a (6/8) Coronary artery bypass graft surgery/Cardio-pulmonary bypass surgery Postoperative -  Age ≥ 65 years was related to loss of appetite at 6 th week after surgery
Zhang et al., 2009 19 Observational analytical study: Case-controlled study Hospital 412 (206 for study group and 206 for control group) Level 3.d ⊕⊕⊕◯ Moderate a (6/8) Coronary artery bypass graft surgery, repair of congenital heart disease, valve replacement, aortic operation/Cardio-pulmonary bypass surgery Pre/Under/ Postoperative -  Sex (non-significant) -  Cardioplegia: Cold crystal, warm blood, cold blood (non-significant) -  Cardiopulmonary bypass time > 120 minutes -  Preoperative serum creatinine ≥ 179 µmol/L -  Emergency surgery -  Perfusion Pressure ≤ 40mmHg -  Low cardiac output syndrome -  On ventilator ≥ 96 hours -  Age ≥ 61 years -  Heart failure NYHA Class III & IV
Ammouri et al., 2016 14 Observational analytical study without a control group Two teaching hospitals and three private hospitals 100 Level 3.e ⊕⊕⊕◯ Moderate a (6/8) Coronary artery bypass graft surgery/Cardio-pulmonary bypass surgery Postoperative -  Age ≥ 60 years -  Female -  Illiteracy -  Chronic disease (e.g. diabetes, hypertension, dyslipidemia) -  Not knowing somebody in health field
Joanna Briggs Institute levels of evidence Level 3.c - Observational analytical study: Cohort study with control group Level 3.d - Observational analytical study: Case-controlled study Level 3.e - Observational analytical study: Observational study without a control group
GRADE Working Group Grades of Evidence for certainty of evidence High: The research provides a very good indication of the likely effect. The likelihood that the effect will be substantially different is low. Moderate: The research provides a good indication of the likely effect. The likelihood that the effect will be substantially different is moderate. Low: The research provides some indication of the likely effect. The likelihood that it will be substantially different (a large enough difference that it might have an effect on a decision) is high. Very low: The research does not provide a reliable indication of the likely effect. The likelihood that the effect will be substantially different (a large enough difference that it might have an effect on a decision) is very high.
Explanations a. Risk of bias (low, unclear, high) b. Consistency (consistency, inconsistency, unknown/non applicable) c. Directness (direct, indirect) d. Precision (precise, imprecise)

†The scores of Methodological Quality of the Studies are shown in fractions based on Joanna Briggs Institute and the Mixed Methods Appraisal Tools.

⊕◯◯◯ = Very low quality; ⊕⊕◯◯ = Low quality; ⊕⊕⊕◯ = Moderate quality; ⊕⊕⊕⊕ = High quality

There were 16 factors identified in the six studies related to loss of appetite and they were divided into three phases. The preoperative factors were (a) age ≥ 60 years old; (b) sex (female); (c) history of a chronic disease, such as diabetes, hypertension, hyperlipidemia; (d) illiteracy; (e) not knowing someone in the health field; and (f) preoperative serum creatinine level ≥ 179 µmol/L. The operative factors were (a) emergency surgery; (b) using the heart-lung machine ≥ 120 minutes; (c) perfusion pressure ≤ 40 mmHg; and (d) low cardiac output syndrome. Finally, the postoperative factors were (a) using mechanical ventilation ≥ 96 hours; (b) moderate or higher pain score (≥ 7 points); (c) using pain medications containing codeine; (d) constipation; (e) depression; and (f) New York Heart Association (NYHA) class III and IV. Nevertheless, the study of Zang et al. (2009) 19 reported specifically that the patient’s sex and types of cardioplegia solutions had no impact on loss of appetite in postoperative cardiac surgery patients ( Table 3).

 Discussion

We found that there were 16 factors related to loss of appetite in cardiac surgery patients. They were present in the preoperative, operative, or postoperative/discharge phases.

Preoperative phase

The aging process in itself can produce a loss of appetite due to a decrease in taste and smell, resulting in discontent with eating and a poor appetite 20 . Older people (≥ 60 years) experience a decrease in ghrelin or a hunger hormone, an increase in leptin and insulin, and changes in the gastrointestinal system and inflammatory process, such as an increase in interleukin 1 (IL-1) and 6 (IL-6) and tumor necrosis factor alpha (TNF-α) 21 that contribute to a loss of appetite. Older females, with low estrogen levels transitioning through menopause or post menopause can also have a loss of appetite 20 . Whether males or females are more likely to have a loss of appetite with cardiac surgery, however, needs further study, since Zang et al. (2009) found there was no statistical difference between the two 19 . Chronic disease, such as diabetes or hypertension, can lead to an inflammatory process and an increase in interleukin and tumor necrosis factor alpha, which are known to be related to appetite 22, 23 . Moreover, increased blood sugar and high blood pressure can produce physiological stress. Both may directly and indirectly cause loss of appetite by pathophysiological and psychological pathways 7 .

Illiterate patients and those who do not know someone in the health field tend to experience loss of appetite. They may be less knowledgeable and unsure of self-care activities or uncomfortable and inexperienced in seeking help with their health and nutrition problems. Cebeci and Celik (2008) and Choocherd et al. (2016) also found that low health literacy was related to nutritional problems in coronary artery bypass graft surgery patients 24, 25 . High preoperative serum creatinine also affects loss of appetite, but indirectly 24, 25 . A decline in glomerular filtration is associated with reduced food intake 26– 28 . Although hospitals are not traditionally known for tasty cuisine, prolonged lengths of stay in an intensive care unit can produce depression that may lead to a lack of appetite 26, 29, 30 .

Operative phase

During the use of the heart-lung machine, chemical substances are produced by a systemic inflammatory response named proinflammatory cytokine 31 . This substance includes interleukin (IL), tumor necrosis factor alpha (TNF-α), interferon gamma (IFNγ) and granulocyte-macrophage colony stimulating factor (GM-CSF). Higher levels of chemical substances are strongly related to loss of appetite. These chemical substances also become substantially increased in patients with cancer, affecting appetite. After the heart-lung machine is disconnected, the substances can remain at high levels for 48 hours after surgery 32 . Not only does the heart-lung machine produce a systemic inflammatory response, but the digestive system is interrupted. Prolonged use of the heart-lung machine can lead to weariness and loss of appetite after cardiac surgery 32 .

Low cardiac output syndrome, low perfusion pressure, and emergency surgery may indirectly affect loss of appetite. These three factors correlate with extended stays in the intensive care unit, total lengths of hospitalization, and prolonged intubation times 26, 28 . Low cardiac output and low perfusion pressure place patients at risk of acute kidney injury that can lead to high serum creatinine; and emergency cardiac surgery causes more postoperative complications in patients than planned surgery 26, 27, 33 . These three conditions may collectively bring about stress and depression, leading to loss of appetite 26, 29, 30, 34 .

Postoperative phase

Prolonged mechanical ventilation requires suctioning patients’ endotracheal tubes to clear the airway, leading to post-extubation fatigue and loss of appetite. It is a significant factor affecting patients’ appetite levels after their endotracheal tubes are removed. Longer periods of postoperative mechanical ventilation are also influenced by higher levels of preoperative creatinine, low cardiac output, and psychological depression, further contributing to loss of appetite 35 . Depression itself is a source of appetite loss by the hypoactivation of the brain’s insular regions, especially mid-insular cortex that supports the body’s physiological control of eating 36 . Depressed patients have an increase in their hypothalamic-pituitary-adrenal drive that can cause high levels of cortisol, which is associated with decreased appetite and hypoactivation of food-motivation neurocircuitry 30, 34, 37 . The interactivity and interaction among these regions, however, contribute to individual differences in patients with depression-related appetite changes 36 .

After open heart surgery, patients experience pain and discomfort during routine postoperative care, such as deep breathing and coughing to expand the lungs and clear secretions, using an incentive spirometer, moving/turning in bed coupled with early ambulation, and undergoing physical therapy with possible rehabilitation activities. Pain decreases the movement and mobility of patients, so the stomach and intestine are relatively less functional 38 . Patients can feel anxious, insecure, and uncertain about the disease and success of the surgery, causing them to have emotional stress. These complicated reactions are intercorrelated and can affect the appetite directly and indirectly. As a result, these patients may experience a decrease in appetite with a distorted perception of smell and gustatory dysfunction, leading to a lower consumption of food 39 .

Pain that occurs immediately after cardiac surgery is called acute pain, whereas pain after hospital discharge is chronic pain. Both can stimulate the inflammatory process, which causes the release of cytokine, especially IL-6 40, 41 . Interleukine-6 is related to loss of appetite. Because the release of cytokine leads to the pain cycle, postoperative patients require analgesics, usually with codeine 42, 43 . Medications containing codeine coupled with less physical movement and stomach/intestinal dysfunction may cause constipation. Constipation affects loss of appetite because patients feel that food remains in the gastrointestinal system, which produces abdominal discomfort 38, 44 .

Patients with NYHA Class III & IV heart failure may have a loss of appetite due to hypervolemia, especially if there is congestion in the lungs, liver, and intestine 45 . Congestion directly affects the function of the respiratory and gastrointestinal systems, producing dyspnea, fatigue, and inactivity, all related to loss of appetite. Liver and intestinal congestion leads to gastrointestinal hypomotility of the stomach and intestine 46 . This may cause abdominal distension and discomfort, thus inhibiting patient activities would stimulate appetite. In addition, medications that treat and control heart failure, such as digoxin and simvastatin, not only impact appetite indirectly by affecting the function of the gastrointestinal system but also decrease appetite directly 46, 47 .

Five out of the six studies had a moderate level of methodological quality 14, 16– 19 . The researchers did not report their confounding factors, missing data, or how they managed the statistical challenges. Only one study (Corrêa & Cruz, 2000) reported controlling for two confounding factors that may have affected loss of appetite (i.e. level of pain and onset of having pain) 15 . Pain is both a rapidly (state variable) and slowly (trait variable) changing factor 48, 49 . A state variable can change in a short time period and at a specific moment, whereas a trait variable takes much longer to change. Corrêa and Cruz (2000) divided the samples into several groups based on the level and onset of pain and compared the differences of loss of appetite between each group to identify more clearly the factors related to loss of appetite 15 . Because only one of the six studies demonstrated high methodological quality by controlling for confounding factors, we cannot make firm conclusions on the overall results of the systematic review 12 .

Some of the 16 factors we report are not exclusive to postoperative cardiac surgery patients. Other types of surgery can produce changes in eating behaviors, food intake, loss of appetite, and malnutrition in postoperative patients. Factors may include older age 50, 51 ; sex (female) 50– 52 ; type of illness or chronic disease, such as type 2 diabetes mellitus 50, 52 ; medications 50 ; length of hospital stay 50 ; and psychological factors, such as stress, depression, psychopathology, and well-being 53 . In addition to those reported for general surgery patients, our systematic review expanded knowledge of other specific factors related to loss of appetite in postoperative cardiac surgery patients.

Strengths and limitations

We searched extensively the published literature in eight national and international databases, restricting the studies to those in English or Thai. Out of a large potential number of studies, only six met the specific criterion related to loss of appetite in postoperative cardiac surgery patients 14– 19 . None of the studies had loss of appetite as a primary research objective. Methodological problems in some studies could have been strengthened by having larger sample sizes, reporting how missing data were handled, and mentioning how confounding factors were controlled 14, 16– 19 . In the studies with a larger sample size, subgroup analysis on individual factors could have brought better understanding of their influence on loss of appetite 19 . None of the six studies used an experimental research design and long-term evaluation.

Conclusions and implication

This systematic review 54 provides initial knowledge for the development of nursing interventions based on the factors related to loss of appetite in postoperative cardiac surgery patients. Clinical assessment by nurses and other health professionals should include whether patients were on the heart-lung machine ≥ 120 minutes, had emergency surgery, reported having a low cardiac output syndrome, or required mechanical ventilation ≥ 96 hours. To promote patient’s nutritional status, there should be evidence-based practice guidelines on the management of postoperative symptoms related to loss of appetite. These would include pain management, treatment of constipation, and reduction of emotional stress and depression. Additional information on self-care should be given to patients and families before hospital discharge to relieve their stress and depression, enhance knowledge of nutrition to promote healing, and prevent loss of appetite. However, nurses and health professionals should first assess health literacy to ensure that patients and families adequately understand the discharge instructions. Discharge planning should provide instruction on how to support self-care ability and reduce post-discharge problems, especially guidance in nutrition after coronary artery bypass graft surgery. A multidisciplinary approach, including physician, nurse, dietitian/nutritionist, and pharmacist, should be considered as part of the holistic care given to postoperative cardiac surgery patients because loss of appetite can result from multiple factors that lead to poor nutrition and inhibit healing.

Future research should focus on the identified factors related to appetite loss in postoperative cardiac surgery patients. The use of multiple research methods and longitudinal studies will provide a foundation for evidence-based interventions to reduce loss of appetite and improve nutritional status for patients after cardiac surgery.

 Data availability Underlying data

All data underlying the results are available as part of the article and no additional source data are required.

 Reporting guidelines

Figshare: PRISMA checklist for ‘Factors related to loss of appetite in postoperative cardiac surgery patients: A systematic review’, https://doi.org/10.6084/m9.figshare.14473188 54

Data are available under the terms of the Creative Commons Zero “No rights reserved” data waiver (CC0 1.0 Public domain dedication).

 Acknowledgements

We are very thankful to those who contributed to this systematic review for their collaboration and support. Special appreciation is extended to Dr. Andrew C. Mills for reviewing early drafts.

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Appetite. 2020;150:104575. 31875518 10.1016/j.appet.2019.104575 Figshare: PRISMA checklist for ‘Factors related to loss of appetite in postoperative cardiac surgery patients: A systematic review’. http://www.doi.org/10.6084/m9.figshare.14473188 10.5256/f1000research.55541.r289513 Reviewer response for version 1 Ogawa Masato 1 Referee Department of Rehabilitation Science, Osaka Health Science University, Osaka, Japan

Competing interests: No competing interests were disclosed.

 26 6 2024 Copyright: © 2024 Ogawa M 2024 This is an open access peer review report distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. recommendation approve-with-reservations

This manuscript is a well-organized systematic review summarizing loss of appetite in cardiac surgery patients, providing clinically valuable information. Furthermore, loss of appetite, and subsequent malnutrition, are highly likely to affect patient prognosis, making this an extremely important report. The methodology, synthesis, and presentation of results in this systematic review adhere to guidelines and are appropriate.

I have one point to raise:

Table 3 summarizes the included studies, but how was loss of appetite, the focus of this review, diagnosed? There is no clinical consensus on how to diagnose loss of appetite, and summarizing the diagnostic criteria used in previous studies would be very helpful. Please add this information to Table 3.

Are the rationale for, and objectives of, the Systematic Review clearly stated?

Yes

Is the statistical analysis and its interpretation appropriate?

Yes

If this is a Living Systematic Review, is the ‘living’ method appropriate and is the search schedule clearly defined and justified? (‘Living Systematic Review’ or a variation of this term should be included in the title.)

Not applicable

Are sufficient details of the methods and analysis provided to allow replication by others?

Partly

Are the conclusions drawn adequately supported by the results presented in the review?

Yes

Reviewer Expertise:

Nutrition

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.

Banharak Samoraphop Faculty of Nursing, Khon Kaen University, Thailand

Competing interests: No competing interests were disclosed.

 28 6 2024

Thank you so much for your excellent suggestion. We are also concerned about the diagnosis or criteria to define loss of appetite. We have provided this information in the data extraction table when extracting data, and we can add it to Table 3 by adding one more column. The criteria or diagnosis for loss of appetite in the six included studies were defined by using the symptoms inventory or scale such as the Gastrointestinal Symptom Frequency and Symptom Distress Scale, The Self-Reporting Occurrences of Symptoms, the Cardiac Surgery Symptom Inventory, and the Cardiac Symptoms Survey. These will be added to Table 3 for the revised version.

 10.5256/f1000research.55541.r92460 Reviewer response for version 1 Ji Bingyang 1 Referee https://orcid.org/0000-0002-1410-6901 Department of Cardiopulmonary Bypass, State Key Laboratory of Cardiovascular Medicine, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences, Beijing, China

Competing interests: No competing interests were disclosed.

 13 9 2021 Copyright: © 2021 Ji B 2021 This is an open access peer review report distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. recommendation approve-with-reservations

The authors systematically reviewed the factors related to appetite loss after cardiac surgery, which is a quite interesting topic. I have several suggestions:

The INTRODUCTION section introduced background knowledge of cardiac surgery. I think the authors should discuss less about it and merge this part with the BACKGROUND section.

I have some concerns on the methods of systematic review. The authors listed PRISM flowchart, some important data were not reported. After excluding duplications, 3246 articles were excluded because they were not published in English/Thai, did not report heart surgery patients or other reasons. The authors should better report the exact number of patients excluded in every step. This may allow replication by other researchers.

Table 2 reported Quality Assessment of the Evidence by GRADE Guideline, and all six articles were of high or moderate quality. I suggest the authors reported more details on assessing the article. It's better to not just report whether it is precise, but report the details of how you decide it's precise.

I recommend the authors to ask for language editing, as some syntax errors existed. e.g. Page 6, Paragraph 4, Line 6, 'Pain is both a rapidly (state variable) and slowly (trait variable) changing factor. '

Are the rationale for, and objectives of, the Systematic Review clearly stated?

Partly

Is the statistical analysis and its interpretation appropriate?

Yes

Are sufficient details of the methods and analysis provided to allow replication by others?

Partly

Are the conclusions drawn adequately supported by the results presented in the review?

Yes

Reviewer Expertise:

The blood conservation and organ protection during cardiopulmonay bypass. Improving the prognosis of extracorporeal life support.

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.

Banharak Samoraphop Faculty of Nursing, Khon Kaen University, Thailand

Competing interests: Non-Financial Competing Interests

 28 9 2021

The INTRODUCTION section introduced background knowledge of cardiac surgery. I think the authors should discuss less about it and merge this part with the BACKGROUND section.

Response: Thank you for suggestion. The introduction and Background to an academic paper are different things and both are essential. The Introduction comes first and is a relatively short section of the manuscript which sets the study we are reporting in its widest context.  However, the Background is the place to begin to focus on what, specifically, we investigated. In other words, the INTRODUCTION is the overview, however, BACKGROUND is more scope and focus of what is the phenomenon of this study. For these reasons, we would like to separate and keep these two parts if possible.

I have some concerns on the methods of systematic review. The authors listed PRISM flowchart, some important data were not reported. After excluding duplications, 3246 articles were excluded because they were not published in English/Thai, did not report heart surgery patients or other reasons. The authors should better report the exact number of patients excluded in every step. This may allow replication by other researchers.

Response: We would like to say thanks for this useful comment and agree with this suggestion. We can add more detail about how many articles were excluded for each reason. There were 347 for not published in English/Thai; 1,245 not heart surgery patients; 109 animal study; and 1,545 not research article.

Table 2 reported Quality Assessment of the Evidence by GRADE Guideline, and all six articles were of high or moderate quality. I suggest the authors reported more details on assessing the article. It's better to not just report whether it is precise, but report the details of how you decide it's precise.

Response: Thank you so much for useful suggestion. We have followed the GRADE Guideline from Joanna Briggs Institute and provide the standard reported table of GRADE following "Quality Assessment of the Evidence by GRADE Guideline." However, we can add more detail about the reason for giving score for risk of bias, precision, directness, and consistency at the Table 2. 

Unclear = The researchers did not indicate or reported how they designed for controlling confounding factors and dealing with missing data

Precise =  The researchers described how to measure their primary and secondary outcomes and used appropriate statistic for their data analysis

Direct = The researchers demonstrated they measured primary and secondary outcomes in intervention and control groups in the same way

Consistent =  The researchers demonstrated they measured primary and secondary outcomes in intervention and control groups in the same construct and measurement

I recommend the authors to ask for language editing, as some syntax errors existed. e.g. Page 6, Paragraph 4, Line 6, 'Pain is both a rapidly (state variable) and slowly (trait variable) changing factor.”

Response: Thank you so much for suggestion. We have edited this sentence as "Pain is both a rapid (state variable) and slow (trait variable) changing factor." Moreover, this manuscript will be proved again by the English native speaker before publishing the final version.