Standardised Frailty Indicator as Predictor for Postoperative Delirium after Vascular Surgery: A Prospective Cohort Study

Transcription

1 Eur J Vsc Endovsc Surg (2011) 42, 824e830 Stndrdised Frilty Indictor s Predictor for Postopertive Delirium fter Vsculr Surgery: A Prospective Cohort Study R.A. Pol, B.L. vn Leeuwen, L. Visser, G.J. Izks b, J.J.A.M. vn den Dungen, I.F.J. Tielliu, C.J. Zeebregts, * Deprtment of Surgery, University Medicl Center Groningen, University of Groningen, Groningen, The Netherlnds b University Center of Geritric Medicine, University Medicl Center Groningen, University of Groningen, Groningen, The Netherlnds Submitted 18 Februry 2011; ccepted 7 July 2011 Avilble online 31 July 2011 KEYWORDS Postopertive delirium; Vsculr surgery; Risk fctor; Frilty; Groningen Frilty Indictor Abstrct Objectives: To determine whether the Groningen Frilty Indictor (GFI) hs positive predictive vlue for postopertive delirium (POD) fter vsculr surgery. Methods: Between Mrch nd August 2010, 142 consecutive vsculr surgery ptients were prospectively evluted. Preopertively, the GFI ws obtined nd postopertively ptients were screened with the Delirium Observtion Scle (DOS). Ptients with DOS-score 3 points were ssessed by geritricin. Delirium ws defined by the DSM-IV-TR criteri. Primry outcome vrible ws the incidence of POD. Secondry outcome vribles were ny surgicl compliction nd hospitl length of sty (HLOS) (>7 dys). Results: Ten ptients (7%) developed POD. The highest incidence of POD ws found fter ortic surgery (17%) nd mputtion procedures (40%). Incresed comorbidities (p Z 0.006), GFI score (p Z 0.03), renl insufficiency (p Z 0.04), elevted C-rective protein (p Z 0.008), high Americn Society of Anesthesiologists score (p Z 0.05), DOS-score of 3 points (p Z 0.001), post-opertive intensive cre unit dmittnce (p Z 0.01) nd HLOS 7 dys (p Z 0.005) were risk fctors for POD. The GFI score ws not ssocited with prolonged HLOS. A men number of 2 1(rnge0e5) complictions were registered. The receiver opertor chrcteristics (ROC) re under the curve for the GFI ws Conclusions: The GFI cn be helpful in the erly identifiction of POD fter vsculr surgery in select group of high-risk ptients. ª 2011 Europen Society for Vsculr Surgery. Published by Elsevier Ltd. All rights reserved. * Corresponding uthor. C.J. Zeebregts, Deprtment of Surgery, Division of Vsculr Surgery, University Medicl Center Groningen, P.O. Box , 9700 RB Groningen, The Netherlnds. Tel.: þ ; fx: þ E-mil ddress: czeebregts@hotmil.com (C.J. Zeebregts) /$36 ª 2011 Europen Society for Vsculr Surgery. Published by Elsevier Ltd. All rights reserved. doi: /j.ejvs

2 Frilty Indictor s Predictor for Delirium 825 Postopertive delirium (POD) is common nd serious compliction fter surgery. It is defined s n cute disorder of ttention nd cognition nd is chrcterised by fluctuting symptoms of inttention, disturbnce of consciousness nd disorgnised thinking. 1 Not only does it ffect pproximtely 11e24% of elderly ptients on hospitl dmission, it is lso ssocited with longer hospitlistion nd institutionlistion, higher medicl costs, persistent functionl decline nd even deth. 1e7 With the elderly popultion incresing t n unprecedented rte, the number of surgicl procedures in the elderly will increse in the future. Therefore, the incidence of POD is lso likely to increse, unless preventive strtegies re developed. The first crucil step in delirium prevention is the identifiction of those ptients most t risk for POD. From vrious studies focussing on POD mong surgicl ptients, it is known tht vsculr surgery ptients, especilly fter ortic surgery, re t highest risk for developing POD. 1 This seems primrily determined by both dvnced ge nd the tendency to hve multiple comorbidities, including cerebrovsculr disese. Notwithstnding this incresed incidence, very few studies focus on risk fctors nd delirium prevention mong vsculr surgery ptients nd n ccurte pre-screening tool is currently lcking. 8e12 At the University Medicl Center Groningen, the Groningen Frilty Indictor (GFI) hd been developed to identify ptients t risk for POD nd other dverse outcomes. 13 The GFI is simple questionnire consisting of 15 items which re clssified into eight seprte groups, consistent with the domins of functioning (Tble 1). A score of four or more indictes higher risk for frilty nd possible delirium. Although the GFI hs been primrily designed for oncogeritric surgicl ptients nd hs lredy been vlidted in vrious publictions nd mong different ptient groups, including trumtology, pulmonology, oncology nd internl medicine ptients, to dte the GFI hs not been tested mong vsculr surgery ptients. 14e19 The purpose of this prospective cohort study ws to determine whether the GFI hs positive predictive vlue for POD nd other surgicl complictions in vsculr surgery ptients nd could potentilly be used s screening tool to identify ptients t high risk for POD. Mterils nd Methods Between Mrch nd August 2010, totl of 142 consecutive vsculr surgery ptients were prospectively evluted. All vsculr surgery ptients dmitted nd/or operted in n elective setting, regrdless of ge or co-morbidity, were included. All ptients were exmined both pre- nd postopertively. Preopertively, the GFI ws obtined t the surgicl outptient clinic by specilly trined nurses. During dmission, ll ptients were observed by nurses trined for this study during three shifts. When POD ws highly suspected, the wrd doctor ws informed nd further ssessment ws done by using the delirium observtion screening scle (DOS). The DOS consists of 13 items tht cn be rted s bsent or present nd describes typicl behviourl ptterns relted to delirium. 20,21 Three or more points were considered indictive of delirium. When delirium ws present or suspected, geritricin ws consulted nd the dignosis ws confirmed bsed on the DSM-IV-TR criteri. 22 Medicl co-morbidity ws quntified using the Chrlson comorbidity index (CCI). 23 As such, ech medicl condition ws ssigned weighted score, rnge 0e19. Bsed on these comorbidities, the CCI predicts the 1-yer mortlity. Aprt from the GFI nd DOS, routine clinicl dt were recorded pre-, intr- nd postopertively. The following predictors were investigted: preopertive predictors such s ge nd sex, Americn Society of Anesthesiologists score (ASA), hemoglobin level, impired renl function (glomerulr filtrtion rte (GFR) <60 ml min m 2 ), C-rective protein (CRP), nd leucocyte count; intr-opertive predictors such s estimted blood loss, type of surgicl procedure nd type of nesthesi; nd post-opertive predictors nd outcomes such s intensive cre unit (ICU) dmittnce, hospitl length of sty (HLOS), psychoctive drug dministrtion (in cse of POD) nd ll medicl complictions tht occurred during hospitlistion. Surgicl complictions nd deths were identified nd clssified ccording to system proposed by Clvien nd ssocites. 24,25 The ClvieneDindo clssifiction of surgicl complictions is vlidted system tht correltes with both the complexity of the procedure s well s HLOS. Complictions re grded from 1 to 6 nd rnge from minor complictions without the need for intervention (1) to the deth of ptient (6). The primry outcome vrible ws the incidence of POD. Secondry outcome vribles were ny (post-opertive) surgicl compliction nd HLOS (>7 dys). This study ws pproved by the Institutionl Review Bord. All ptients gve informed consent. Sttisticl Anlyses Differences between ctegoricl vribles tht were possibly relted to the development of POD were tested with Person s c 2 test (two vribles). Differences between numericl vribles were tested with Student s two-tiled test (normlly distributed continuous vribles) or, if pproprite, MnneWhitney U test (skewed continuous vribles). Skewed continuous vribles re shown s medin (interqurtile rnge). Vribles ssocited with outcome POD nd sttisticlly significnt with univrite nlysis were entered into multivrite logistic regression nlysis using simultneous forced entry model (Enter method). We used probbility for stepwise entry of p < 0.05 nd probbility of removl of p < The GFI ws plotted in receiver opertor chrcteristics (ROC) curve. Two-til P-vlues were used throughout nd significnce ws set t p < Dt re presented s mens stndrd devition, unless stted otherwise. All sttisticl nlyses were done with the Sttisticl Pckge for the Socil Sciences (SPSS , SPSS, Chicgo, IL, USA, 2007). Results A totl of 142 ptients were included in the study nd further nlyzed. The men ge of the totl cohort ws yers (21e87). There ws n unequl distribution in sex with 100 men (70%) nd 42 women (30%). Ptient chrcteristics nd demogrphic dt re shown in Tble 2.

3 826 R.A. Pol et l. Tble 1 The Groningen Frilty Indictor (GFI). Mobility Cn the ptient perform this tsk without ny help? (using tools like wlking sticks, wheelchirs or wlker is regrded s independent) 1. Go shopping Wlk round outside (round the house or to neighbours) Dressing nd undressing Toilet visit 0 1 Vision 5. Does the ptient experience problems in dily life by poor vision? 1 0 Hering 6. Does the ptient experience problems in dily life by poor hering? 1 0 Nutrition 7. Hs the ptient involuntrily lost weight (6 kg) in the pst 6 months 1 0 (or 3 kg in one month) Co-morbidity 8. Does the ptient currently use four or more different types of mediction? 1 0 Yes No Sometimes Cognition 9. Does the ptient currently hs complints bout his memory (or hs history of dementi) Psychosocil 10. Does the ptient sometimes experience emptiness round him? Does the ptient sometimes miss people round him? Does the ptient sometimes feel bndoned? Hs the ptient recently felt sd or depressed? Hs the ptient recently felt nervous or nxious? Physicl fitness 15. Which grde would the ptient give its physicl fitness (0e10, rnging from very bd to good) 0e6 Z 17e10 Z Totl score GFI A score of four or more indictes higher risk for frilty nd possibly delirium. YES NO Ten ptients (7%) developed POD. The highest incidences were found fter open ortic surgery (30%) nd mputtion procedures (40%). Types of surgery with concomitnt POD incidences re shown in Tble 3. Groningen Frilty Indictor s predictor for POD A totl of 50 ptients (35%) scored GFI of 4 points. The predictive vlue of the GFI ws ssessed with univrite nlyses. A GFI score 4 points ws significntly relted with the development of POD (p Z 0.03). The ROC curve for GFI s predictor for delirium is shown in Fig. 1. The re under the curve ws 0.70 with the GFI set t 4 s indictive of n incresed risk for POD (sensitivity 50%, specificity 78%). With the GFI cut-off point djusted to 6 points, the re under the curve incresed to 0.89 (sensitivity 50%, specificity 86%). GFI s predictor for post-opertive complictions nd HLOS Complictions were recorded using the ClvieneDindo clssifiction. A totl of 33 complictions were registered (rnge 0e5). Grdes 1 nd 2 were most frequently recorded (Tble 1). The GFI score ws not predictive fctor for the development of complictions (p Z 0.83). Also, the number of complictions were not significntly relted to the development of POD (p Z 0.37). The GFI score ws not ssocited with prolonged HLOS with men HLOS for GFI <4 of dys vs dys for GFI 4 (p Z 0.71). Additionl predictive fctors for POD Univrite nlysis yielded vrious fctors tht were ssocited with the development of POD. These fctors included the number of comorbidities (p Z 0.006), impired renl function (glomerulr filtrtion rte (GFR) <60 ml min m 2 )(p Z 0.04), elevted C-rective protein (CRP) (p Z 0.008), high Americn Society of Anesthesiologists (ASA) score (p Z 0.05) nd DOS-score of 3 points (p Z <0.005). In terms of outcome prmeters, both post-opertive ICU dmittnce (p Z 0.01) nd HLOS 7 dys (p Z 0.005) were ssocited with the development of POD (Tble 4). Although ge lone ppered to hve no significnt reltion to POD, high ge (>65 yers) did ccount for >75% of ll complictions. Multivrite logistic regression nlyses on the fctors significntly ssocited

4 Frilty Indictor s Predictor for Delirium 827 Tble 2 Ptient chrcteristics nd demogrphic dt. Prmeter Number or men SD (Percentge or rnge) Number (%) 142 (100) Age (yers) (21e87) Gender Men 100 (70) Women 42 (30) Delirium 10 (7.0) GFI 4 b 50 (35.2) Comorbidities (CCI) c 5 2(1e14) Blood loss (ml) (0e3500) Impired renl function d 16 (11) Pre-opertive hemoglobin (4.7e11.1) (mmol/l) C-rective protein 5(5e13) (mg/dl) (medin, IQR) e ASA f (1e4) ICU dmittnce 23 (16) (no of ptients) Hospitl length of sty 5.6 4(1e30) (dys) Complictions g (rnge 0e5) b Stndrd devition. Groningen Frilty Indictor, score of four or more indictes higher risk for frilty nd possibly delirium. c Chrlson comorbidity index, weighed index which mesures the burden of comorbidities nd predicts 1-yer mortlity (rnge 0e19 indicting respectively no comorbidities to considerble comorbidities). d Defined s glomerulr filtrtion rte (GFR) <60 ml/ min 1.73 m 2. e CRP level >5 mg/dl s mesured preopertively. f Americn Society of Anesthesiologists score (ssesses the fitness of ptients prior to surgery, 1 Z norml helthy ptient nd 5 Z moribund ptient who is not expected to survive without the opertion). g According to the ClvieneDindo clssifiction of surgicl complictions Complictions re grded from 1 to 6 nd rnge from minor complictions without the need for intervention (1) to the deth of ptient (6). with POD in univrite nlyses identified no independent risk fctors for POD. However, there ws trend towrds sttisticl significnce for the GFI (OR 1.9, 95% CI 0.98e3.77) (Tble 5). Tble 3 Types of surgicl procedures with concomitnt postopertive delirium incidences. Type of procedure Number of ptients (%) Delirium present (%) Open ortic surgery 18 (12.7) 3 (30) Endovsculr procedures 30 (21.1) 2 (20) Peripherl bypss surgery 39 (27.5) 0 Arteriovenous shunt surgery 2 (1.4) 0 Percutneous interventions 27 (19.0) 0 Amputtion surgery 10 (7.0) 4 (40.0) Miscellneous 16 (11.3) 1 (10) Totl 142 (100) 10 (100) Figure 1 Receiver opertor chrcteristics (ROC) curve for the GFI s predictor for delirium in 142 ptients undergoing elective vsculr procedures. The re under the curve is 0.70 with the GFI set t 4 s indictive of n incresed risk for POD (sensitivity 50%, specificity 78%). With GFI cut-off point of 6 points, the re under the curve incresed to 0.89 (sensitivity 50%, specificity 86%). Fctors nd outcome prmeters significntly ssocited with DOS-score of 3 points were the number of comorbidities (p Z 0.04) nd incresed CRP levels (p Z 0.01) nd n extended HLOS 7 dys (p Z 0.02) (Tble 6). Discussion This study shows the predictive vlue of the GFI in the development of POD fter elective vsculr surgery in heterogeneous ptient popultion. Although mny studies hve identified risk fctors for delirium, this study provides the physicin with the bility to be informed bout the risk very erly in the tretment process. By strting preventive tretments or ggressive ssessment during hospitlistion in ptients with GFI 4 points, we believe tht this could reduce the incidence of POD nd perhps, ultimtely, HLOS. In this context, both the British Geritric Society nd Dutch Professionl Guideline hve set up useful clinicl guidelines to prevent nd tret delirium which could be converted to clinicl rodmp nd dded to the clinicl chrt of these high-risk ptients. 26,27 A Cochrne dtbse systemtic review on delirium prevention hs lredy proven tht both ctive geritric consulttion nd low dose hloperidol mediction in high-risk post-opertive ptients my reduce the degree nd durtion of POD. 28 In ddition to the GFI score, pre-existing comorbidities, n elevted CRP nd ICU dmittnce were ssocited with n incresed risk for POD in univrite nlysis. These fctors hve been reported previously s risk fctors for POD nd confirm tht our studied cohort corresponds with similr studies on POD. 2,7,11,29,30 Contrry to the literture, ge ws not predictor for POD in the current study but this my be the result of the limited number of ptients in the studied cohort. There re severl drwbcks in this study tht need to be ddressed. We found n unexpected nd reltively low delirium incidence despite incresed wreness nd DOS ssessment. In the current literture, POD incidences fter elective vsculr surgery vry from 23% to 39%. 8e12 The

5 828 R.A. Pol et l. Tble 4 Vrible Univrite nlysis with prevlence nd medin vlues of risk fctors for the development of postopertive delirium. Predictor Delirium present Delirium bsent P vilble (100%) Age (men SD) Femle gender (10.0%) 41 (31.1%) Comorbidities (CCI) b Hemoglobine (mg/ml) Impired renl function c (33.3%) 13 (10.3%) 0.04 C-rective protein, medin 65 5 (5e9) 149 (52e219) (IQR) Leukocyte count ASA-score >2 d (90%) 79 (59%) 0.05 Blood loss (ml), medin (IQR) (13e3250) 63 (0e188) 0.15 Hospitl length of sty, medin (6e15) 4 (3e7) (IQR) ICU-dmittnce (44%) 19 (14.1%) 0.02 DOS-score >3 e 46 4 (100%) 1 (2.4%) <0.005 GFI score, medin (IQR) f (2.5e7.5) 3 (1e4) 0.03 Results reported s number. IQR Z interqurtile rnge. p-vlues 0.05 were considered sttisticlly significnt. b Chrlson comorbidity index, weighed index which mesures the burden of comorbidities nd predicts 1-yer mortlity (rnge 0e19 indicting respectively no comorbidities to considerble comorbidities). c Defined s glomerulr filtrtion rte (GFR) <60 ml/min 1.73 m 2. d Americn Society of Anesthesiologists (ssesses the fitness of ptients prior to surgery, 1 Z norml helthy ptient nd 5 Z moribund ptient who is not expected to survive without the opertion). e Delirium Observtion Screening scle. Consists of 13 items, 3 points were considered indictive for delirium. f Groningen Frilty Indictor, score of 4 indictes higher risk for frilty nd possibly delirium. reported rte in our study my be low s result of the incresed wreness of signs of POD mongst the nursing stff in the prticipting wrds. It is known effect tht incresing wreness of signs of delirium decreses the incidence of full-blown POD. It is, however, not n uncommon finding tht delirium incidence is low in specific prevlence studies. In lrge prospective cohort study by Mrcntonio et l., postopertive delirium occurred in only 117/1341 (9%) ptients older thn 50 yers, which confirms tht the incidence does not entirely depend on group size. 31 Although we know from severl studies focussing on delirium prevention tht high ge is risk fctor for POD, we included ll ge groups who underwent elective vsculr surgery to relibly estimte the vlue of the GFI in this cohort of ptients. We feel this ws justified choice s the vsculr ptient in itself is friler thn generl surgicl ptients nd thus possibly more prone to develop POD. This Tble 5 Multivrite nlysis of risk fctors for the development of postopertive delirium. Vrible Odds rtio 95% Confidence intervl P GFI-score e Comorbidities (CCI) e C-rective protein e Chrlson comorbidity index, weighed index which mesures the burden of comorbidities nd predicts 1-yer mortlity (rnge 0e19 indicting respectively no comorbidities to considerble comorbidities). hs led to diverse ptient popultion with men ge of (rnge 21e87). Even though the GFI score ws not predictor for post-opertive complictions, high ge (>65 yers) did ccount for >75% of ll complictions. Furthermore, lthough the GFI seems to provide good estimte of the risk for POD, it is probbly not relible in younger (<65 yers) ptient group. In multivrite nlyses the problem of underfitting occurred in our model. For credible risk estimte, rtio of 10 events per independent vrible is suggested. Becuse of the unexpected low POD incidence in our study, this rtio could unfortuntely not be met in the current model. This mens tht the outcome for individul vribles my not be trustworthy. 32 Consequently, lthough trend towrds sttisticl significnce ws suggested, neither the GFI nor the other independent risk fctors reched significnt outcome in the multivrite model. We would hve strongly preferred tht ll ptients hd undergone proper DOS ssessment. Unfortuntely, becuse of logisticl problems, we hd to choose the current lterntive with DOS ssessment only in cses when suspicion for POD ws high. This my hve led to n underestimtion of delirium incidence by missing clinicl subtypes such s hypoctive delirium or the unclssified type which ccount for respectively 29% nd 7% of delirium subtypes. 3 Despite the predictive vlue of the GFI score, the re under the curve ws only 0.70 with the GFI score set t 4 but incresed to 0.89 fter djusting the GFI cutoff point to 6 points. Wheres score of 4 ws chosen for fril ptients in generl, this cut-off score ws determined by previous publictions. 14e19 This is the first study in which

6 Frilty Indictor s Predictor for Delirium 829 Tble 6 Vrible Univrite nlysis with prevlence nd medin vlues of risk fctors for n incresed DOS-score. Predictor vilble (100%) DOS-score <3 DOS-score 3 P b Age Femle gender (100%) 0 (0%) Comorbidities (CCI) c Hemoglobine (mg/ml) Impired renl function d (71.4%) 2 (28.6%) C-rective protein, 65 5 (5e11.75) 98 (44e182) 0.01 medin (IQR) Leukocyte count ASA-score >2 e (78.1%) 4 (12.9%) Blood loss (ml), medin (0e500) 300 (162e1900) (IQR) Hospitl length of sty, (4e7) 8 (7e22) medin (IQR) ICU-dmittnce (75%) 2 (25%) GFI score, medin (IQR) f (2e4.5) 3 (1e8.5) Results reported s number. IQR Z interqurtile rnge. Delirium Observtion Screening scle. Consists of 13 items, 3 points were considered indictive for delirium. b p-vlues 0.05 were considered sttisticlly significnt. c Chrlson comorbidity index, weighed index which mesures the burden of comorbidities nd predicts 1-yer mortlity (rnge 0e19 indicting respectively no comorbidities to considerble comorbidities). d Defined s glomerulr filtrtion rte (GFR) <60 ml/min 1.73 m 2. e Americn Society of Anesthesiologists (ssesses the fitness of ptients prior to surgery, 1 Z norml helthy ptient nd 5 Z moribund ptient who is not expected to survive without the opertion.). f Groningen Frilty Indictor, score of 4 indictes higher risk for frilty nd possibly delirium. the GFI score ws tested in vsculr surgery ptients. Within the GFI questionnire, points re given which re consistent with the domins of functioning. Vsculr surgery ptients re generlly considered group with limited mobility nd therefore get points wrded which re not directly relted to frilty. It, therefore, my very well be possible tht the cut-off score should be djusted in this ptient group. But more likely is tht the GFI in its current form my not pply to the entire cohort of ptients undergoing vsculr surgery. In order to determine its true vlue in POD risk ssessment fter vsculr surgery, n djusted score must be used in this specific cohort. In subsequent study, modified score shll be used which will be pplied to the group t highest risk for POD (ge 65 yers, ortic surgery nd mputtion procedures). In conclusion, this prospective study shows tht the GFI, with its limittions, cn be helpful in the erly identifiction of select group of high-risk ptients with respect to the development of delirium fter vsculr surgery. Despite rnge of publictions on pre- nd post-opertive risk fctors for POD, preopertive tool for risk ssessment is not yet t hnd. By using the GFI to identify these ptients during the preopertive outptient evlution, pproprite preventive rrngements, such s preopertive geritric consulttion, cn be implemented. In this wy HLOS, medicl costs nd further institutionlistion (due to functionl loss, loss of independence nd the inbility to return to their homes) cn potentilly be reduced. However, the pplicbility within the entire cohort of vsculr surgery ptients cn be further improved bsed on this implementtion study. Conflict of Interest/Funding The uthors declre no conflict of interest or finncil support. References 1 Dsgupt M, Dumbrell AC. Preopertive risk ssessment for delirium fter noncrdic surgery: systemtic review. JAm Geritr Soc 2006;54:1578e89. 2 Brown TM, Boyle MF. Delirium ABC of psychologicl medicine. BMJ 2002;325:644e7. 3 Sxen S, Lwley D. Delirium in elderly; clinicl review. Postgrd Med J 2009;85:405e13. 4 Frnco K, Litker D, Locl J, Bronson D. The cost of delirium in the surgicl ptient. Psychosomtics 2001;42:68e73. 5 Bickel H, Grdinger R, Kochs E, Forstl H. High risk of cognitive nd functionl decline fter postopertive delirium. Dement Geritr Cogn Disord 2008;26:26e31. 6 Minden SL, Crbone LA, Brsky A, Borus JF, Fife A, Fricchione GL, et l. Predictors nd outcome of delirium. Gen Hosp Psychitry 2005;27:209e14. 7 Robinson TN, Reburn CD, Trn ZV, Angles EM, Brenner LA, Moss M. Postopertive delirium in the elderly. Risk fctors nd outcome. Ann Surg 2009;249:173e8. 8 Bohner H, Schneider F, Stierstorfer A, Weiss U, Gbriel A, Friedrichs R, et l. Postopertive delirium following vsculr surgery. Anesthesist 2000;49:427e33. 9 Ssjim Y, Ssjim T, Uchid H, Kwi S, Hg M, Aksk N, et l. Postopertive delirium in ptients with chronic lower limb ischemi: wht re the specific mrkers? Eur J Vsc Endovsc Surg 2000;20:132e7.

7 830 R.A. Pol et l. 10 Schneider F, Bohner H, Hbel U, Slloum JB, Stierstorfer A, Hummel TC, et l. Risk fctors for postopertive delirium in vsculr surgery. Gen Hosp Psychitry 2002;24:28e Böhner H, Hummel T, Hbel U, Miller C, Reinbott S, Yng Q, et l. Predicting delirium fter vsculr surgery. A model bsed on pre- nd intropertive dt. Ann Surg 2003;238:149e Blsundrm B, Holmes J. Delirium in vsculr surgery. Eur J Vsc Endovsc Surg 2007;34:131e4. 13 Steverink N, Slets JPJ, Schuurmns H, Vn Lis M. Mesuring frilty: developing nd testing the GFI (Groningen Frilty Indictor). Gerontologist 2001;41: Schuurmns H, Steverink N, Lindenberg S, Frieswijk N, Slets JPJ. Old or fril: wht tells us more? J Gerontol A Biol Sci Med Sci 2004;59:962e5. 15 Metzelthin SF, Dniels R, vn Rossum E, de Witte L, vn den Heuvel WJ, Kempen GI. The psychometric properties of three self-report screening instruments for identifying fril older people in the community. BMC Public Helth 2010;10: Kellen E, Bulens P, Deckx L, Schouten H, vn Dijk M, Verdonck I, et l. Identifying n ccurte pre-screening tool in geritric oncology. Crit Rev Oncol Hemtol 2010;75:243e8. 17 Andel RM, Dijkstr A, Slets JPJ, Sndermn R. Prevlence of frilty on clinicl wrds: description nd implictions. Int J Nurs Prct 2010;16:14e9. 18 Aldriks AA, Mrtense E, Le Cessie S, Gilty EJ, Verln HA, vn der Geest LG, et l. Predictive vlue of geritric ssessment for ptients older thn 70 yers, treted with chemotherpy. Crit Rev Oncol Hemtol; 2010 Aug 13 [Epub hed of print]. 19 Slets JPJ. Vulnerbility in the elderly: frilty. Med Clin North Am 2006;90:593e vn Gemert LA, Schuurmn MJ. The Neechm Confusion Scle nd the Delirium Observtion Screening Scle: cpcity to discriminte nd ese of use in clinicl prctice. BMC Nurs 2007;6:3. 21 Scheffer AC, vn Munster BC, Schuurmns MJ, de Rooij SE. Assessing severity of delirium by the delirium observtion screening scle. Int J Geritr Psychitry 2011;26:284e Kpln nd Sdock s synopsis of psychitry. Behviorl sciences/clinicl psychitry. 8th ed. Mrylnd: Willims & Wilkins; pp. 320e8. 23 De Groot V, Beckermn H, Lnkhorst GJ, Bouter LM. How to mesure comorbidity: criticl review of vilble methods. J Clin Epidemiol 2003;56:221e9. 24 Dindo D, Demrtines N, Clvien PA. Clssifiction of surgicl complictions. A new proposl with evlution in cohort of 6336 ptients nd results of survey. Ann Surg 2004;240: 205e Clvien PA, Brkun J, de Oliveir ML, Vuthey JN, Dindo D, Schulick RD, et l. The Clvien-Dindo clssifiction of surgicl complictions. Five-yer experience. Ann Surg 2009;250: 187e British Geritric Society. Clinicl guidelines for the prevention, dignosis nd mngement of delirium in older people in hospitl, clinicl_1-2_fulldelirium.htm; Jnury Dutch Assocition for Psychitry. Guidelines delirium: G3Tb8bZjkqp8M63HtZ9fdUIXgS9g8-mE5U&showZ1. 28 Siddiqi N, Stockdle R, Britton AM, Holmes J. Interventions for preventing delirium in hospitlised ptients. Cochrne Dtbse Syst Rev 2007;18. CD Litker D, Locl J, Frnco K, Bronson D, Tnnous Z. Preopertive risk fctors for postopertive delirium. Gen Hosp Psychitry 2001;23:84e9. 30 Koebrugge B, Koek HL, vn Wensen RJA, Dutzenberg PLJ, Bossch K. Delirium fter bdominl surgery t surgicl wrd with high stndrd of delirium cre: incidence, risk fctors nd outcomes. Dig Surg 2009;26:63e8. 31 Mrcntonio ER, Goldmn L, Orv EJ, Cook EF, Lee TH. The ssocition of intropertive fctors with the development of postopertive delirium. Am J Med 1998;105:380e4. 32 Concto J, Feinstein AR, Holford TR. The risk of determining risk with multivrible models. Ann Intern Med 1993;118: 201e10.