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RESEARCH

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valuation of Taste Sensitivity in Patientsndergoing Coronary Artery Bypass Grafturgery

ARY KEITH, PhD, RD; ROSE MOKBEL, RN; MARIO SAN EMETERIO; JACQUELIN SONG, MSc, RD; LEE ERRETT, MD

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BSTRACTatients report changes in their perception of food tastes

ollowing cardiac surgery. This study was designed toxplore changes in taste sensitivity following coronaryrtery bypass graft (CABG) surgery. Detection and rec-gnition thresholds for sweet (sucrose), salty (sodiumhloride), sour (citric acid), and bitter (quinine hydrochlo-ide) were determined using the multiple forced-choicescending concentration series method at baseline (pre-urgical), discharge, 5 weeks, and 16 weeks post-CABG.emographic and gastrointestinal data were also ob-

ained. Mixed-model analyses for repeated measuresere performed using the baseline scores as reference.hirty-three patients (mean age�61.8�8 years), con-ented to participate in the study between January 2003nd January 2006, with 13 completing all visits. Detec-ion and recognition thresholds for sweet were signifi-antly lower at discharge compared with baseline (1.7�.2 vs 2.43�1.4 and 5.1�1.8 vs 5.5�1.3, respectively;�0.05). This difference remained significant 4 monthsfter surgery. Detection and recognition thresholds foralt also declined with time, with significant differencest 4 months post-surgery (2.3�2.0 vs 1.8�1.5; P�0.001nd 5.3�1.3 vs 4.2�2.2; P�0.05, respectively). The samerends were noted for the detection of sour and the rec-

. Keith is coordinator of nutrition and dietetic educa-ion, Supply Chain and Support Services, St Michael’sospital, Toronto, Ontario, Canada; she is also an associ-te scientist, Keenan Research Center, Li Ka Shing Knowl-dge Institute, Toronto, Ontario, Canada; and an assistantrofessor, Department of Nutritional Sciences, Universityf Toronto, Toronto, Ontario, Canada. R. Mokbel is a re-earch coordinator, J. Song is a clinical dietitian, and. Errett is chief of cardiovascular and thoracic surgery,ll in the Heart Program, St Michael’s Hospital, To-onto, Ontario, Canada. M. San Emeterio is a researcholunteer, Supply Chain and Support Services, St Mi-hael’s Hospital, Toronto, Ontario, Canada.

Address correspondence to: Mary Keith, PhD, RD, Stichael’s Hospital, 6th Floor Cardinal Carter Wing, 30ond St, Toronto, Ontario, M5B 1W8 Canada. E-mail:eithm@smh.toronto.on.caManuscript accepted: November 3, 2009.Copyright © 2010 by the American Dietetic

ssociation.0002-8223/$36.00

qdoi: 10.1016/j.jada.2010.04.005

072 Journal of the AMERICAN DIETETIC ASSOCIATION

gnition of bitter. Patients undergoing CABG demon-trated stable or improved taste sensitivity during theecovery period. Further studies aimed at clarifying theelationships between the biological state, taste sensitiv-ty, reported taste changes, and food intake will help tolarify the clinical impact of taste changes and subse-uently to guide clinical nutrition care.Am Diet Assoc. 2010;110:1072-1077.

ccording to the American Heart Association, approx-imately 450,000 coronary artery bypass graft(CABG) procedures are completed annually in the

nited States. Clinicians working in postsurgical pro-rams report that patients commonly experience changesn taste and that these changes are a considerable sourcef distress both within and outside of the hospital setting.hanges in taste sensitivity might not only influence foodhoices, but can also negatively impact food intake duringtime of recovery and healing. Furthermore, changes in

ood intake and, subsequently, nutritional status, havehe potential to negatively impact wound healing, speedf rehabilitation, and, ultimately, length of hospitaliza-ion.

Recent studies support that gastrointestinal symp-oms, including lack of taste, occur in a considerableroportion of postsurgical patients (1). Ball and Grap (1)eported that nausea was found to be the most distressingymptom (reported by 29%), and poor appetite was theost frequently reported symptom, reported by 60% of

ostsurgical patients. In a follow-up study, the Gastroin-estinal Symptom and Distress Scale was administered to22 postcardiac surgery patients at 2 and 6 weeks post-urgery (2). Approximately 37% of patients reported lackf taste, 36% reported symptoms of nausea, and 58%eported lack of appetite in the hospital (2). Two weeksost-surgery, 15% continued to report nausea, 42% re-orted loss of appetite, and 36% reported lack of taste (2).t week 6 post-surgery, lack of taste and loss of appetiteere both reported by 19% of patients, and nausea was

till reported by 10% of patients (2). These findings sug-est that gastrointestinal complications are a consider-ble problem in the postsurgical period and can be theesult of anesthesia, drugs, or the need for mechanicalentilation (2).Although alterations in taste perception after cardiac

urgery have been documented both clinically and in theiterature, to date, any examination of changes in tastecuity has been limited to administration of subjective

uestionnaires (often conducted by phone) emphasizing

© 2010 by the American Dietetic Association

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ymptoms and has not included specific objective mea-urements of taste change (1-3). Therefore, questions re-ain about the types of changes in taste sensitivity that

an occur following cardiac surgery, as well as their rela-ionship with food intake and nutritional status. Theurpose of this study was to assess short- and long-termaste alterations among post-CABG patients by examin-ng their detection and recognition thresholds for the fourey types of taste. This study was not designed to deter-ine whether undergoing cardiac surgery resulted in

ifferent changes in comparison with other surgical pro-edures. It was hypothesized that following surgery, par-icularly before discharge, patients would require higheroncentrations of each stimuli (higher detection and rec-gnition thresholds) in order to both recognize and iden-ify it. Understanding the nature of the taste changedhould assist clinicians in guiding patients in the selec-ion of more appealing and acceptable food choices toaintain or improve nutritional status in the postopera-

ive period.

ETHODSesign and Proceduresonsecutive adult patients (older than 18 years of age)ndergoing first-time, elective CABG surgery were ap-roached for participation in the study during the periodanuary 2003 to January 2006. Patients were excludedrom participating if they were unable or unwilling torovide consent, were undergoing concomitant proce-ures (valve replacement�CABG), had undergone che-otherapy or radiation to the head or neck, or had aistory of chronic liver or renal failure. Participants weresked to undergo taste detection and recognition thresh-ld measurements at four points in time; ie, baselinepresurgical), before discharge (day 4 or 5 post-surgery), 5routine postsurgical visit), and 16 weeks post-surgery.aseline measures of taste sensitivity were made in con-

unction with the routine preadmission facility visit,hich usually occurred 2 to 3 weeks before surgery. At

his time, demographic data and a medical history werebtained. A detailed inventory of all medications wasaintained throughout the study. Intra- and postopera-

ive data were also collected. The Gastrointestinal Symp-om Frequency and Symptom Distress Scale was admin-stered at all visits (3). Finally, each participant wassked to rate their nausea and appetite using a 10-cmisual analog scale. Participants made a mark on the0-cm line at the distance from each anchor point thatest described their current state. Anchor points for ap-etite were poor to very good and never to always forausea.Before taste testing, participants were instructed to not

at or drink for at least 1 hour. In addition, spicy foodsere to be avoided for the 24 hours before testing andarticipants were asked to refrain from smoking theorning of the taste testing. Participants requiring den-

ures removed them for the testing. Taste testing startedy each participant rinsing their mouth with deionizedater. All taste testing was completed between 9 and 11

M in one of the cardiac surgery examination rooms.

hese rooms are relatively quiet and have minimal visual c

nd olfactory stimulation because the division of cardio-ascular surgery is relatively isolated from the rest of theospital. Discharge taste testing was completed in theardiovascular surgery patient lounge in the absence ofther patients or visitors. The testing procedure usedultiple forced-choice presentation with an ascending

eries (4). Briefly, three cups were presented in a preran-omized order—two contained 10 mL deionized waternd one contained 10 mL test solution. Participantsested the cups from left to right taking all the solutionnto the mouth, swishing it around then expectorating it.ubjects were instructed not to guess which cup held theest solution before beginning the taste testing. Subjectsere then asked to identify the cup containing the test

olution. The mouth was rinsed with deionized waterefore offering the next series to avoid carry-over effects.est solutions were offered starting with the lowest con-entration and moving toward the highest (1 to 10) untilhe presence of a taste was identified correctly twice inuccession. The detection threshold was then defined ashe lowest cup number at which the participant was firstble to identify the presence of the test solution. Theubjects’ taste recognition threshold was defined as theowest cup number (the lowest concentration) at whichhe subject correctly identified or described the test stim-lus (ie, sweet, sour, etc). Taste thresholds were identi-ed for four tastants; ie, sucrose (sweet), sodium chloridesalty), citric acid (sour), and quinine hydrochloride (bit-er). The concentration gradients used for each of theastes were based on those previously used in the litera-ure (sucrose 1.25�10�3 to 6.4�10�1 mol/L; sodium chlo-ide 1.25�10�3 to 6.4�10�1 mol/L; citric acid 4.88�10�5

o 2.5�10�2 mol/L; quinine hydrochloride 3.11�10�7 to.6�10�4 mol/L) (5). Initially, three series were obtainedor each taste, with each series presented in randomrder; however, at discharge (postoperative day 4 or 5),ost patients could only tolerate two series. Data for each

f the series were averaged.This study was approved by the St Michael’s Hospital

esearch Ethics Board and each participant providedritten informed consent.

tatistical Analysisemographic data, medical history, and gastrointestinal

ymptom frequencies are presented as counts and per-entages for categorical variables and for continuous vari-bles as means and standard deviations. The frequenciesf responses reporting gastrointestinal symptoms asometimes/rarely and often/always were combined, indi-ating symptoms were present. Frequencies of gastroin-estinal symptoms were compared overall as well as be-ween baseline and discharge using Fisher’s exact �2 test.ean detection and recognition thresholds were com-

ared to baseline at each follow-up point using the mixed-odel analyses for repeated measures. The mean values

rom all available information, not just from those 13espondents who completed all testing sessions, were in-luded in the mixed model to examine changes in out-omes over time. Furthermore, a series of Wilcoxon and tests indicated that those 13 respondents who completedll testing sessions did not differ significantly from thoseith incomplete data in terms of most of the key out-

omes at baseline. All P values were two-sided, and sig-

July 2010 ● Journal of the AMERICAN DIETETIC ASSOCIATION 1073

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ificance was set at a value of 0.05. Statistical analysesere performed using SAS Version 9 (2000, SAS Institute

nc, Cary, NC).

ESULTStudy Participantshirty-three subjects with a mean age of 61.8�8.1

range�41 to 75) years underwent baseline taste-sensi-ivity testing, 22 participants completed postsurgicalesting, and 13 participants returned for their 4-monthollow-up visit. Characteristics of the study participantsre found in the Table. Fifty-eight percent of participantsurrently smoked or had smoked in the past, 36% wereiabetic, 82% had hypertension, and 78% had hypercho-esterolemia.

urgical Outcomeshe majority of participants required three bypass grafts,ith a mean time on cardiopulmonary bypass of 77.7�4.2 minutes (data not shown). No participants died orad a stroke following bypass graft surgery and the mean

ength of hospital stay was 6.5�2.5 days.ppetite, Nausea, and Gastrointestinal Symptoms. Visual ana-og scores revealed that 55% of participants experienced aecline in appetite and 27% experienced an increase inausea in the immediate postoperative period (data nothown). Following discharge, participants reported signifi-antly reduced levels of nausea at both the 5-week and-month follow-up visits (P�0.05). Appetite steadily in-reased following hospital discharge and was not substan-ially different than baseline at 16 weeks post-surgery.ata from the gastrointestinal symptom frequency and

everity scores revealed that 41% of patients experiencedroblems with poor appetite, 18% with lack of taste, and

Table. Baseline characteristics of patients consenting to partici-pate in a study of taste changes following coronary artery bypassgraft surgery

Characteristics

No. of subjects 33Age (y), mean�standard deviation 61.8 � 8.1Previous myocardial infarction, n (%) 11 (33.3)Previous PTCA,a n (%) 3 (9.1)Previous angiography, n (%) 29 (87.9)Valvular disease, n (%) 2 (6.1)Cigarette smoker,b n (%) 19 (57.6)Hypertension, n (%) 27 (81.8)Family history, n (%) 16 (48.5)Diabetic, n (%) 12 (36.4)Hypercholesterolemia/triglycerides, n (%) 25 (75.8)Peripheral vascular disease, n (%) 2 (6.1)Transient ischemic attack, n (%) 1 (3)Respiratory disease, n (%) 9 (27.3)Renal disease, n (%) 4 (12.1)

aPTCA�percutaneous transluminal coronary angioplasty.bIncludes present and past smokers, only two participants were current smokers.

2% with nausea while in the hospital (data not shown). f

074 July 2010 Volume 110 Number 7

roblems with appetite occurred considerably more oftenuring hospitalization in comparison with before surgerydata not shown). Finally, two patients (5%) continued toeport problems with poor appetite 16 weeks after bypassraft surgery.aste Detection and Recognition Thresholds. Detection andecognition thresholds for the four tastes are found in theigure, panels A-D. For bitter, the concentration at whichitter was detected declined over time and no significantifferences were observed. Recognition of the bitter tasteccurred earlier and at a significantly lower concentra-ion (P�0.01) after surgery when compared with base-ine. For salty taste, both detection and recognitionhresholds declined with time, both reaching statisticalignificance at 16 weeks post-surgery (P�0.05). For theweet taste, both detection and recognition occurred at aower concentration following surgery (discharge), whichas statistically significant (P�0.05). Furthermore, sweet-etection thresholds continued to decline with signifi-ance achieved at the 16-week follow-up visit (P�0.05).inally, although both detection and recognition thresh-lds for sour were relatively preserved throughout thetudy, they did decline in the late postoperative period,chieving significance 16 weeks post-surgery (Figure,anel D; P�0.01).

ISCUSSIONontrary to the proposed hypothesis, this study failed toemonstrate impaired taste acuity, defined as increasedhresholds for the recognition or detection of stimuli inither the immediate or longer postoperative period. Inact, as a general trend, tastes were both detected andecognized at lower concentrations (lower thresholds) inoth the immediate (at discharge—postoperative day 4 or) and longer-term (16-week) period.CABG surgery is a highly invasive procedure requiring

he placement of an endotracheal tube for mechanicalentilation. In addition to placement of this tube, postop-rative care involves a battery of medications, each ofhich can contribute to changes in taste sensitivity. Cli-icians have identified changes in taste as a source ofistress for both hospitalized and recovering patients.herefore, the aim of this study was to explore how car-iac surgery influenced taste sensitivity. Understandinghe nature of any changes in taste represents the firsttep in defining its importance on nutritional intake,tatus, and rehabilitation. This study was not designed toetermine whether changes in taste associated with car-iac surgery were different in comparison with otherypes of surgical procedures. As a result, the findings ofhis study cannot be attributed to cardiac surgery per se,s they may have been influenced by many other factors.One factor that may have influenced the perception and

dentification of taste changes is the biological state of thendividual. Early studies by Moskowitz and colleagues (6)uggest that the biological states of satiety and hungeran affect taste preferences. Hormonal levels, circulatingevels of blood glucose, time of day, and obesity have alleen related to changes in taste acuity (7-10). Zverev (11)valuated the impact of caloric restriction on taste acuity.ecognition thresholds for both sucrose and salt were

ound to be considerably lower during caloric deprivation

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n comparison with during caloric loading. These datauggest that fasting individuals may experience height-ned taste sensitivity. In the context of this study, post-

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urgical patients are initially provided with minimalourishment, then progress from clear fluids to a full dietithin a couple of days. Therefore, one might speculate

hat the increasing awareness and hunger of these pa-ients may have contributed to the observed increases inaste acuity observed during this period. Furthermore,he heightened taste sensitivity to sweet observed in thisopulation may impact the acceptability of most oral nu-ritional supplements, which are typically quite sweet.owever, not all studies have found a consistent effect of

asting on changes in taste acuity and, subsequently,urther studies should be conducted to clarify the role ofhe biological state (both hormonal and hunger) on bothaste acuity and patient food preferences (12).

Although not previously studied in patients undergoingardiac surgery, changes in taste perception have previ-usly been evaluated in several different clinical condi-ions, including patients with head injuries, renal dis-ase, eating disorders, cancer, and cachexia, and in theged (13-16). Elderly patients have been shown to havelevated recognition thresholds for all tastes, with someex differences (17,18). Patients with cancer have beeneported to have changes in taste that have been relatedo subsequent development of anorexia (14). Loweredaste thresholds for bitter (urea) have been demonstratedn this population and have been related to the presencef meat aversion (14). Therefore, it is possible that spe-ific increases in taste acuity may translate into alterederceptions of food taste. As a result, it will be importantor future studies to link changes in specific taste acuitieso reported alterations in the perceived taste of wholeoods, as well as to alterations in dietary intake. Specifichanges in the perception of food taste may lead to foodvoidance and, subsequently, reduced intake. Changes inood intake together with reduced appetite and increasedausea may, over the long-term, place the patient atutritional risk.There are some important limitations of this study.

hanges in taste acuity were determined in a group ofatients undergoing cardiac surgery only and did notnclude patients undergoing other surgical procedures orormal controls. Therefore, comments can only be maden what was observed in this population and not extrap-lated to other surgical procedures. Furthermore, theurpose of this study was to, as a first step, definehanges in taste associated with cardiac surgery and,

igure. Taste detection and recognition thresholds in patients under-oing coronary artery bypass graft surgery measured before surgery, atischarge, and 5 and 16 weeks postoperatively.(A-D) Mean detectionnd recognition thresholds for each of the four basic tastes, ie, sweetA), sour (B), bitter (C), and salt (D). (A) Bitter detection and recognitionhresholds declined at discharge, although only the recognition wasignificant (P�0.05). (B) Salt. Both recognition and detection thresholdsor the salt taste were significantly reduced at the 16-week postoper-tive time point (P�0.05). (C) Detection and recognition thresholds forhe sweet taste declined significantly at the discharge time point fromaseline (P�0.05). Detection thresholds remained significantly lower at6 weeks (P�0.05). (D) Sour detection and recognition thresholdsemained relatively stable throughout the study with a significant

ecline in detection thresholds at 16 weeks (P�0.01).

July 2010 ● Journal of the AMERICAN DIETETIC ASSOCIATION 1075

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herefore, no attempt was made to collect information onhanges in food perceptions or dietary intake. Now thathe nature of these changes in taste is defined, it will bemportant for future studies to link changes in taste tohanges in food preference, nutrient intake, and, subse-uently, nutritional risk. Measurement of taste acuitysing the current methodology requires that each seriessweet, sour, salty, and bitter) be offered three times (4).urthermore, with each taste offered, there are 2 cups ofeionized water that also need to be tasted. This can lead toome patients consuming �150 pill cups of liquid, leading toonsiderable fatigue and time commitment. Therefore, al-hough scientifically sound, in clinical practice the numberf series had to be limited to two repetitions in order toeduce dropouts. In addition, in the immediately postop-rative period (discharge time point), there were manyatients who found the idea of doing the taste testingnappealing and many dropped out of the study or de-lined to do the testing at this point. These postoperativeropouts may have biased the data because it might behat those were the patients experiencing the most post-perative discomfort, nausea, and pain and, subse-uently, may have also been experiencing more changesn taste. In addition to the dropouts at discharge, somearticipants refused to come back for testing at the 16-eek time point, limiting the number who completed the

tudy to 22. This is one of the difficulties associated withhe conduct of clinical studies that involve travel to anrban center for appointments. Dropout rates were min-

mized by designing three of four study visits to occur inonjunction with other hospital appointments. In addi-ion, to maximize available data, statistical methodolo-ies that allowed for missing data and included all avail-ble data points were utilized. Furthermore, reportedhresholds may be lower, as only an ascending seriesrotocol was used and not a combination of ascending andescending series. Also, finding an ideal setting for theompletion of postoperative taste testing was difficult.atients had limited mobility and often these tests wereompleted in the patients’ room and may be influenced byheir surroundings. However, every effort was made toake the testing area comfortable and free from distrac-

ions. In addition, it is possible that changes in medica-ion use during the study may have influenced the results17). Furthermore, the study participants ranged widelyn age and, therefore, variation in detection and recogni-ion thresholds may reflect individual and age-relatedifferences in taste acuity, even at baseline. However, bysing each individual as their own control individual,hanges in taste can be tracked against their baselineaste acuity. Furthermore, the literature suggests thatnly a single taste bud is needed to respond to all fourastes (17). Finally, approximately half of the partici-ants were either former or current smokers. There isome evidence, albeit controversial, that smoking willnfluence taste acuity, especially for the perception ofweet (19). However, because only two participants wereurrently smoking at the time of enrollment into thetudy, and the statistical analysis used baseline tasteata for reference, any confounding effect of smoking

ould be minimized.

076 July 2010 Volume 110 Number 7

ONCLUSIONhanges in the perception of food taste have been re-orted to be a source of distress for patients and can limitood intake during a critical time for healing. Contrary tohe hypothesis, these data suggest improved taste acuityreduced detection and recognition thresholds) for severalastes in both the immediate and longer-term postopera-ive period following cardiac surgery. Improved taste acu-ty might reflect changes in hormonal and/or biologicalesponse to food deprivation as a result of the surgicalrocess. Subsequently, clinicians working with postcar-iac surgery patients should be aware that changes inaste acuity can influence both the perceived “taste” ofood and patient food preferences. Clinicians might alsoeed to be creative in the provision of adequate nutritionupport in this population, as heightened taste sensitivityo sweet may limit the use of currently available enteralutrition supplements. Negative taste experiences mayesult in a reduction in food intake in some patients,otentially compromising nutritional status, wound heal-ng, speed of rehabilitation, and length of stay in hospital.egistered dietitians should, therefore, play an impor-

ant role in both the preoperative education of patientsbout potential changes in taste that can occur afterardiac surgery, as well as assisting patients postopera-ively in the identification of taste changes in order toelp them to select and procure nutritionally rich, accept-ble foods both while in hospital and following discharge.dentification, assessment, and evaluation of tastehanges, together with patient education, may help toessen the anxiety associated with perceived changes inaste. Future studies should investigate the relationshipsetween changes in taste acuity and biological statelength of postoperative fasting and suboptimal intake),s well as changes in food preferences reported by pa-ients. The use of a control group or patients undergoingther surgical procedures would help to delineatehether changes in taste are unique to cardiac surgeryatients or whether they can be generalized to all surgi-al patients. Furthermore, longitudinal studies investi-ating the association between changes in taste usingoth ascending and descending series methodologies andood intake will build upon current findings and will bemportant to assess the impact of taste changes on nutri-ional status over the long term in these patients. Nega-ive changes in food intake during the recovery periodave the potential to impair wound healing, delay reha-ilitation, and increase length of hospitalization. Thisnd future studies will assist clinicians in the provision ofptimal postoperative care to patients who have under-one cardiac surgery.

TATEMENT OF POTENTIAL CONFLICT OF INTEREST:o potential conflict of interest was reported by the au-

hors.FUNDING/SUPPORT: Funded by a research grant

rom the Canadian Foundation for Dietetic Research.

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6. Small DM, Zatorre RJ, Jones-Gotman M. Changes in taste intensityperception following anterior temporal lobe removal in humans. ChemSenses. 2001;26:425-432.

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