Early Determinants of Death Due to Multiple Organ Failure After Noncardiac Surgery in High-Risk...

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American Society of Critical Care Anesthesiologists Section Editor: Michael J. Murray Early Determinants of Death Due to Multiple Organ Failure After Noncardiac Surgery in High-Risk Patients Suzana M. Lobo, MD, PhD,* Ederlon Rezende, MD,† Marcos F. Knibel, MD, PhD,‡ Nilton B. Silva, MD, PhD,§ Jose ´ A. Pa ´ramo, MD, Fla ´vio E. Na ´cul, MD,¶ Ciro L. Mendes, MD,# Murilo Assunc ¸a ˜o, MD,** Rubens C. Costa, MD,†† Cíntia C. Grion, MD, PhD,‡‡ Se ´rgio F. Pinto, MD,§§ Patricia M. Mello, MD, Marcelo O. Maia, MD,¶¶ Pe ´ricles A. Duarte, MD,## Fernando Gutierrez, MD, PhD,†† Joa ˜o M. Silva Junior, MD,*** Marcel R. Lopes, MD,††† Jose ´ A. Cordeiro, PhD,‡‡‡ and Charles Mellot, MD, PhD§§§ BACKGROUND: Prediction of perioperative cardiac complications is important in the medical management of patients undergoing noncardiac surgery. However, these patients frequently die as a consequence of primary or secondary multiple organ failure (MOF), often as a result of sepsis. We investigated the early perioperative risk factors for in-hospital death due to MOF in surgical patients. METHODS: This was a prospective, multicenter, observational cohort study performed in 21 Brazilian intensive care units (ICUs). Adult patients undergoing noncardiac surgery who were admitted to the ICU within 24 hours after operation were evaluated. MOF was characterized by the presence of at least 2 organ failures. To determine the relative risk (RR) of in-hospital death due to MOF, we performed a logistic regression multivariate analysis. RESULTS: A total of 587 patients were included (mean age, 62.4 17 years). ICU and hospital mortality rates were 15% and 20.6%, respectively. The main cause of death was MOF (53%). Peritonitis (RR 4.17, 95% confidence interval [CI] 1.38 –12.6), diabetes (RR 3.63, 95% CI 1.17–11.2), unplanned surgery (RR 3.62, 95% CI 1.18–11.0), age (RR 1.04, 95% CI 1 0.01–1.08), and elevated serum lactate concentrations (RR 1.52, 95% CI 1.14 –2.02), a high central venous pressure (RR 1.12, 95% CI 1.04–1.22), a fast heart rate (RR 3.63, 95% CI 1.17–11.2) and pH (RR 0.04, 95% CI 0.0005– 0.38) on the day of admission were independent predictors of death due to MOF. CONCLUSIONS: MOF is the main cause of death after surgery in high-risk patients. Awareness of the risk factors for death due to MOF may be important in risk stratification and can suggest routes for therapy. (Anesth Analg 2011;112:877–83) A lthough millions of operations are performed annually worldwide, relatively few patients un- dergoing major surgery are deemed high risk and at an increased risk of postoperative complications and death. 1 A large observational study reported that this population accounts for only 12.5% of all surgical procedures, but for 80% of related deaths. 1 Despite the high mortality rates, fewer than 15% of these patients were admitted to the intensive care unit (ICU), 1 showing that individual risk can easily be underestimated and high-risk patients not recognized. In patients with major operative trauma, multiple organ failure (MOF) may be induced by various mechanisms including an aggressive inflammatory response, although the mechanisms by which this occurs are not clear. 2 In- creasing evidence suggests that oxygen requirements in- crease significantly as a result of the injury and metabolic response to trauma. However, very frequently, high-risk patients are unable to spontaneously increase their cardiac output to match this increased oxygen demand. 3 Such patients are therefore more likely to develop oxygen debt and, as a consequence, severe systemic inflammation with death due to ongoing organ dysfunction and nosocomial sepsis. 4 In addition, not infrequently, these patients un- dergo surgery for peritonitis and therefore already have sepsis when submitted to surgery. Several attempts have been made to help identify pa- tients at risk of complications and death after surgery. Studies have identified predictors of morbidity and mor- tality after colon, esophageal, and gastric surgery, and after pulmonary resection. 5–7 Other studies have evaluated pre- dictors of postoperative cardiac complications in noncar- diac surgical patients. 8 –11 High-risk surgical patients admitted to the ICU frequently die as a consequence of primary or secondary MOF, the latter of which is fre- quently a result of sepsis. 12,13 Predictors of death due to MOF have never been investigated in high-risk surgical patients. Therefore, we investigated the early perioperative risk factors for in-hospital death due to MOF in a popula- tion of surgical patients admitted to the ICU. Author affiliations are provided at the end of the article. Accepted for publication February 25, 2010. Supported by Centro de Estudos e Pesquisa em Medicina Intensiva, Hospital de Base, Sa ˜o Jose ´ do Rio Preto, Brazil. The authors report no conflicts of interest. Address correspondence and reprint requests to Dr. Suzana Margareth Lobo, Faculdade de Medicina de Sa ˜o Jose ´ do Rio Preto, Servic ¸o de Terapia Intensiva do Hospital de Base e Laborato ´ rio de Sepse, Avenida Brigadeiro Faria Lima, 5544 CEP 15090-000 Sa ˜o Jose do Rio Preto, SP, Brazil. Address e-mail to [email protected]. Copyright © 2011 International Anesthesia Research Society DOI: 10.1213/ANE.0b013e3181e2bf8e April 2011 Volume 112 Number 4 www.anesthesia-analgesia.org 877

Transcript of Early Determinants of Death Due to Multiple Organ Failure After Noncardiac Surgery in High-Risk...

American Society of Critical Care Anesthesiologists

Section Editor: Michael J. Murray

Early Determinants of Death Due to Multiple OrganFailure After Noncardiac Surgery in High-Risk PatientsSuzana M. Lobo, MD, PhD,* Ederlon Rezende, MD,† Marcos F. Knibel, MD, PhD,‡Nilton B. Silva, MD, PhD,§ Jose A. Paramo, MD,� Flavio E. Nacul, MD,¶ Ciro L. Mendes, MD,#Murilo Assuncao, MD,** Rubens C. Costa, MD,†† Cíntia C. Grion, MD, PhD,‡‡Sergio F. Pinto, MD,§§ Patricia M. Mello, MD,�� Marcelo O. Maia, MD,¶¶ Pericles A. Duarte, MD,##Fernando Gutierrez, MD, PhD,†† Joao M. Silva Junior, MD,*** Marcel R. Lopes, MD,†††Jose A. Cordeiro, PhD,‡‡‡ and Charles Mellot, MD, PhD§§§

BACKGROUND: Prediction of perioperative cardiac complications is important in the medicalmanagement of patients undergoing noncardiac surgery. However, these patients frequently die asa consequence of primary or secondary multiple organ failure (MOF), often as a result of sepsis. Weinvestigated the early perioperative risk factors for in-hospital death due to MOF in surgical patients.METHODS: This was a prospective, multicenter, observational cohort study performed in 21Brazilian intensive care units (ICUs). Adult patients undergoing noncardiac surgery who wereadmitted to the ICU within 24 hours after operation were evaluated. MOF was characterized bythe presence of at least 2 organ failures. To determine the relative risk (RR) of in-hospital deathdue to MOF, we performed a logistic regression multivariate analysis.RESULTS: A total of 587 patients were included (mean age, 62.4 � 17 years). ICU and hospitalmortality rates were 15% and 20.6%, respectively. The main cause of death was MOF (53%).Peritonitis (RR 4.17, 95% confidence interval [CI] 1.38–12.6), diabetes (RR 3.63, 95% CI1.17–11.2), unplanned surgery (RR 3.62, 95% CI 1.18–11.0), age (RR 1.04, 95% CI 10.01–1.08), and elevated serum lactate concentrations (RR 1.52, 95% CI 1.14–2.02), a highcentral venous pressure (RR 1.12, 95% CI 1.04–1.22), a fast heart rate (RR 3.63, 95% CI1.17–11.2) and pH (RR 0.04, 95% CI 0.0005–0.38) on the day of admission were independentpredictors of death due to MOF.CONCLUSIONS: MOF is the main cause of death after surgery in high-risk patients. Awarenessof the risk factors for death due to MOF may be important in risk stratification and can suggestroutes for therapy. (Anesth Analg 2011;112:877–83)

Although millions of operations are performedannually worldwide, relatively few patients un-dergoing major surgery are deemed high risk

and at an increased risk of postoperative complicationsand death.1 A large observational study reported thatthis population accounts for only 12.5% of all surgicalprocedures, but for �80% of related deaths.1 Despite thehigh mortality rates, fewer than 15% of these patientswere admitted to the intensive care unit (ICU),1 showingthat individual risk can easily be underestimated andhigh-risk patients not recognized.

In patients with major operative trauma, multiple organfailure (MOF) may be induced by various mechanismsincluding an aggressive inflammatory response, although

the mechanisms by which this occurs are not clear.2 In-creasing evidence suggests that oxygen requirements in-crease significantly as a result of the injury and metabolicresponse to trauma. However, very frequently, high-riskpatients are unable to spontaneously increase their cardiacoutput to match this increased oxygen demand.3 Suchpatients are therefore more likely to develop oxygen debtand, as a consequence, severe systemic inflammation withdeath due to ongoing organ dysfunction and nosocomialsepsis.4 In addition, not infrequently, these patients un-dergo surgery for peritonitis and therefore already havesepsis when submitted to surgery.

Several attempts have been made to help identify pa-tients at risk of complications and death after surgery.Studies have identified predictors of morbidity and mor-tality after colon, esophageal, and gastric surgery, and afterpulmonary resection.5–7 Other studies have evaluated pre-dictors of postoperative cardiac complications in noncar-diac surgical patients.8–11 High-risk surgical patientsadmitted to the ICU frequently die as a consequence ofprimary or secondary MOF, the latter of which is fre-quently a result of sepsis.12,13 Predictors of death due toMOF have never been investigated in high-risk surgicalpatients. Therefore, we investigated the early perioperativerisk factors for in-hospital death due to MOF in a popula-tion of surgical patients admitted to the ICU.

Author affiliations are provided at the end of the article.

Accepted for publication February 25, 2010.

Supported by Centro de Estudos e Pesquisa em Medicina Intensiva, Hospitalde Base, Sao Jose do Rio Preto, Brazil.

The authors report no conflicts of interest.

Address correspondence and reprint requests to Dr. Suzana MargarethLobo, Faculdade de Medicina de Sao Jose do Rio Preto, Servico de TerapiaIntensiva do Hospital de Base e Laboratorio de Sepse, Avenida BrigadeiroFaria Lima, 5544 CEP 15090-000 Sao Jose do Rio Preto, SP, Brazil. Addresse-mail to [email protected].

Copyright © 2011 International Anesthesia Research SocietyDOI: 10.1213/ANE.0b013e3181e2bf8e

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METHODSData were extracted from a prospective multicenterobservational cohort study, the SCORIS study, per-formed from April 1 to June 31, 2006, to which 21Brazilian ICUs from 18 institutions (8 public and 10private hospitals) contributed. The SCORIS study wasdesigned to evaluate the epidemiology and clinical out-comes of surgical ICU patients and to develop a model topredict the outcome of such patients in Brazilian ICUs.The IRB from the coordinator center waived the need forinformed consent because of the observational nature ofthe study. Institutional recruitment for participation wasby open invitation from the study steering committee.

Adult patients (834 cases) undergoing noncardiac sur-gery and admitted to a participating ICU within 24 hoursafter operation were evaluated for inclusion. Patients un-dergoing trauma, neurological, gynecologic, obstetric, orpalliative surgery were excluded.

Data were collected on age, gender, smoking habits,alcohol abuse, nutritional status, diabetes, renal function,chronic obstructive pulmonary disease, and presence ofmalignant disease.

Patients taking oral antidiabetic medications or insulinwere considered to have a diagnosis of diabetes. Cardiopa-thy was defined as the presence of moderate or severecardiomegaly, turgescent jugular veins, and use of digital,diuretics, antiangina, and antihypertensive drugs. Lowfunctional capacity was defined as inability to climb 2flights of stairs on subjective evaluation. Electrocardio-graphic abnormalities included nonsinus rhythms, frequentventricular extrasystoles (�5/min), Q waves, or ST-T seg-ment abnormalities. For the diagnosis of angina, the Cana-dian Cardiovascular Society classification system was used.A diagnosis of acute myocardial infarction required thepresence of typical electrocardiographic alterations to-gether with elevated cardiac enzymes and/or segmentalwall motion abnormalities on echocardiography. Otherclinical predictors of increased perioperative cardiovascu-lar risk were defined according to the American College ofCardiology/American Heart Association guidelines. All datawere entered on an electronic case report file (Comunicare®)and the variables were cross-checked by 2 of the authors.

The following procedures were considered major surgery:laparotomy, enterectomy, cholecystectomy with choledocho-stomy, major amputation, vascular and aortic procedures,rectal abdominoperineal resection, pancreatectomy, esopha-gectomy, and hepatectomy. Unplanned surgery comprisedadmissions after urgent (within 48 hours of referral) oremergent (immediately after referral/consultation) surgery.The Physiological and Operative Severity Score for the Enu-meration of Mortality and Morbidity (POSSUM), the AcutePhysiology and Chronic Health Disease Classification SystemII (APACHE II) score, the Multiple Organ Dysfunction Systemscore, and the Sequential Organ Failure Assessment scorewere calculated.14–17 Peritonitis was classified according tothe findings noted at laparotomy as either serum fluid asso-ciated with an infection site or the presence of collected ordiffuse purulent discharge in the abdominal cavity.14 Severebleeding was defined as an estimated blood loss �500 mLduring surgery. For vital signs, laboratory tests, and centralvenous pressure (CVP) measurements, the most abnormal

values collected over the first 24 hours of ICU stay wereregistered.

Sepsis syndromes were defined according to the consen-sus conference definitions.18 Early- and late-onset sepsiswere defined as a diagnosis of sepsis made within 72 hoursof ICU admission or thereafter, respectively.

Causes of death were classified as follows: MOF, char-acterized by the presence of at least 2 organ failurescontributing to death; refractory cardiovascular failure,characterized as uncontrollable hypotension despite high-dose vasopressors determining death; coagulation failure,characterized as need for massive transfusion, and hemor-rhagic shock after surgery; sudden death (unexpectedcardiac arrest); and unknown cause.

Data were analyzed using SPSS 13.0 for Windows (SPSS,Inc., Chicago, IL). Continuous variables are presented asmean � SD and/or median (range), and categorical vari-ables are reported as absolute numbers (percentages). Non-parametric tests of comparison were used for variablesevaluated as not normally distributed. Difference testingbetween groups was performed using the 2-tailed t test, �2

test, Wilcoxon test, analysis of variance, and Fisher exacttest as appropriate. Bonferroni adjustment was used formultiple comparisons. We considered P � 0.05 as statisti-cally significant.

We performed a logistic regression multivariate analysiswith in-hospital death due to MOF as the dependent factor.Variables considered for the regression analysis includedage, gender, comorbid diseases, the type of admission(planned or unplanned), the type of surgery (nonmajor ormajor), malnutrition, alcoholism, maximal heart rate (HR),lowest hemoglobin concentration and highest urea concen-tration before operation, severe bleeding during surgery(estimated blood loss �500 mL), arrhythmia during opera-tion, peritonitis, postoperative measurements of minimaland maximal CVP, minimal axillary temperature, totalleukocyte count, hemoglobin concentration, serum lactateconcentration, pH, and total platelet count. Colinearitybetween variables was excluded before modeling. Covari-ates were selected and entered in the model if they attaineda P � 0.2 on a univariate basis.

POSSUM scores with respective estimated mortalityrates were calculated. Discrimination for the severity scoreswas assessed by area under receiver operating characteris-tic (ROC) curves.

RESULTSCharacteristics of the Study GroupsA total of 587 consecutive patients were admitted to theparticipating ICUs during the study period (55% male; meanage � 62.4 � 17 years). A total of 247 patients were excluded(127 for neurosurgery; 35 palliative surgery; 6 gynecologicsurgery; 32 trauma; 34 lost to follow-up; 8 were younger than18 years; and 5 had no indication for ICU admission).

The characteristics of the study groups are shown inTable 1. Cardiopathy (35.4%), cancer (32%), and diabetes(20%) were the most prevalent comorbid conditions. Sixty-six percent of the patients were admitted after majorsurgery and 32% after unplanned surgery. The most com-mon type of surgery was gastrointestinal surgery (44%)followed by vascular procedures (23%).

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A total of 135 patients (23%) had sepsis during their ICUstay; 64% of these died in the hospital. One hundred forty-onepatients (24.0%) had peritonitis of whom 66 (46.8%) devel-oped sepsis, with 50 cases of early-onset sepsis (37%).

The ICU mortality rate was 15%. Overall hospital mor-tality rates were 16.7% at 30 days, 20.6% at 60 days, and20.6% at 90 days. The causes of death in the ICU were MOF(53%), sudden death (14.9%), refractory shock (6.8%),bleeding (2.5%), and unknown (22.8%).

Of the patients who died, 94% had significant medicalcomorbidities at the time of surgery (3.4 � 2.2), 66% hadundergone urgent surgery, 70% were older than 60years, and 46% older than 70 years. In addition, 35% hadlow functional capacity, 28% malnutrition, and 26%hemodynamic instability before surgery. Serum lactateconcentrations, HR, and CVP values were higher and pHlower on the first day of ICU admission in nonsurvivors(Table 2).

Table 1. Characteristics of the Study Group on Admission to the ICU, Occurrence of Sepsis, and ICU andHospital Lengths of Stay in Survivors and Nonsurvivors

Survivors Death due to MOF Death due to other causesNo. of patients 466 64 57Age (y), mean � SD 61.1 � 17.2 66.7 � 16.4* 67.5 � 12.0*Gender (male %) 255 (54.7) 36 (56.2) 31 (54.4)Comorbidities (%)

Cardiopathy 164 (35.2) 25 (39.0) 19 (33.3)Cancer 154 (33.0) 20 (31.2) 14 (24.5)Diabetes 84 (18.0) 24 (37.5)† 12 (21.0)Smoking (active in the last year) 92 (19.7) 13 (20.3) 13 (22.8)Low functional capacity 70 (15.0) 26 (40.6)†‡ 16 (21)Electrocardiographic abnormalities 12 (21.0) 12 (18.7) 12 (21.0)COPD 68 (14.6) 9 (14.1) 10 (17.5)Malnutrition 52 (11.1) 20 (31.2)† 14 (24.5)*Uncontrolled arterial hypertension 41 (8.8) 1 (1.5) 5 (8.8)Previous acute myocardial infarction 45 (9.6) 3 (4.7) 4 (7.0)Heart failure 25 (5.3) 11 (17.2)* 7 (12.2)*Alcoholism 24 (5.1) 5 (7.8) 10 (17.5)†Hemodynamic instability before surgery 8 (1.7) 21 (32.8)† 10 (17.5)†Previous cerebral vascular accident 24 (5.1) 6 (9.4) 7 (12.2)Liver failure 22 (4.7) 8 (12.5) 2 (3.5)Angina 11 (2.4) 2 (3.2) 5 (8.8)Chronic renal failure (need for RRT) 6 (1.3) 4 (6.3) 1 (6.1)

Surgery within 24 h (%)Unplanned surgery 107 (22.9) 45 (70.3)† 33 (57.9)†Major surgery 287 (61.6) 55 (85.9) 47 (82.4)Gastrointestinal surgery 82 (17.6) 16 (25.0)‡ 2 (3.5)Peritonitis 214 (45.9) 24 (53.1) 23 (40.3)Vascular surgery 116 (24.9) 13 (20.3) 8 (14.0)Exploratory laparotomy 17 (3.6) 25 (39.0)† 24 (42.1)†Orthopedic surgery 37 (7.9) 0 (0) 1 (1.7)Others 37 (7.9) 10 (15.6) 22 (38.6)†

Severity scores on admission, mean � SDMODS 3.1 � 2.7 6.0 � 3.1* 6.0 � 3.7*SOFA 4.2 � 3.5 8.1 � 4.5* 7.5 � 4.3*APACHE II 13.3 � 5.8 19.9 � 6.9*‡ 17.1 � 6.0*POSSUM 33.4 � 8.8 47.3 � 11* 44.2 � 12*

OutcomesEarly-onset sepsis (%) 17 (3.6) 22 (34.3)* 11 (19.3)*Late-onset sepsis (%) 30 (6.4) 26 (40.6)* 26 (45.6)*ICU LOS (d), median (IQ) 2 (1–3) 9 (3–15)* 7 (2–16)*Hospital LOS (d), median (IQ) 8 (4–18) 16.5 (8–29) 19 (11.5–46.5)*

ICU � intensive care unit; MOF � multiple organ failure; COPD � chronic obstructive pulmonary disease; RRT � renal replacement therapy; MODS � MultipleOrgan Dysfunction System; SOFA � Sequential Organ Failure Assessment; APACHE II � Acute Physiology and Chronic Health Disease Classification System II;POSSUM � Physiological and Operative Severity Score for the Enumeration of Mortality and Morbidity; LOS � length of stay; IQ � interquartile range.* P � 0.05 vs survivors.† P � 0.001 vs survivors.‡ P � 0.05 vs death due to other causes.

Table 2. Indices of Cardiorespiratory Dysfunctionand Tissue Hypoperfusion in Survivorsand Nonsurvivors

SurvivorsDeath due

to MOFDeath due toother causes

No. of patients 466 64 57pH 7.31 � 0.08 7.20 � 0.13*† 7.27 � 0.09*Serum lactate (mEq/L) 2.4 � 2.1 4.0 � 2.4* 3.4 � 1.9*Heart rate (beats/min) 97 � 19 121 � 24* 118 � 24*Maximal CVP (mm Hg) 10.2 � 7.5 18.2 � 7.7*† 14.5 � 8.2Minimal CVP (mm Hg) 6.4 � 5.4 11.2 � 6.7* 9.8 � 5.7*

MOF � multiple organ failure; CVP � central venous pressure.Data are mean � SD.* P � 0.05 vs survivors.† P � 0.05 vs death due to other causes.

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Characteristics and Outcomes of the PatientsWho Died Due to MOFDeath was due to MOF in 64 patients (53%) (Table 1).Patients who died due to MOF were more severely ill onICU admission (APACHE II, 19.9 � 6.9 vs 17.1 � 6.0, P �0.05) and more frequently died in the ICU (98.4% vs 43.8%,P � 0.05) than patients who died due to other causes. Lowfunctional capacity (41% vs 21%) and gastrointestinal sur-gery (25% vs 3.5%) were significantly more frequent inpatients who died due to MOF than in patients who dieddue to other causes (P � 0.05 for both). In contrast,alcoholism and other types of surgery were more frequentlyassociated with deaths due to other causes (Table 1). Early

onset sepsis was more prevalent in patients who died dueto MOF (34.3%) compared with patients who died of othercauses (19.3%) but the difference was not statisticallysignificant (P � 0.09).

On the day of ICU admission, the maximal CVP wassignificantly higher (18.2 � 7.7 vs 14.5 � 8.2 mm Hg, P �0.01) and the pH significantly lower (7.20 � 0.13 vs 7.27 �0.09, P � 0.05) in patients who died due to MOF than inpatients who died of other causes (Table 2).

The variables identified as independent predictors ofdeath due to MOF were age, unplanned surgery, diabetes,peritonitis, and, on the first day of ICU admission, highCVP (mm Hg), increased HR, increased serum lactateconcentrations (mEq/L), and pH (Fig. 1).

Comparison Between the Outcomes of thePatients to That Predicted by theSeverity ScoresThe POSSUM score gave a standardized mortality ratio of1.2 (degrees of freedom � 0.02, P � 0.001). The area underthe ROC curve for hospital mortality was 0.80 (95% confi-dence interval 0.775–0.840) for the POSSUM score. Theareas under the ROC curves for hospital mortality forAPACHE II, Multiple Organ Dysfunction System, andSequential Organ Failure Assessment scores were 0.808,0.802, and 0.805, respectively (Fig. 2).

DISCUSSIONDespite the large amount of resources directed at evaluat-ing the risk of perioperative cardiovascular complications,our results indicate that MOF is the main cause of death inhigh-risk surgical patients, deemed to be the cause of death

Figure 1. Relative risk (95% confidence interval) of death due to multiple organ failure. MOF � multiple organ failure; RR � relative risk; CI �confidence interval.

Figure 2. Receiver operating characteristic curves for the severityscores. APACHE II � Acute Physiology and Chronic Health DiseaseClassification System II; MODS � Multiple Organ Dysfunction Sys-tem; POSSUM � Physiological and Operative Severity Score for theEnumeration of Mortality and Morbidity; SOFA � Sequential OrganFailure Assessment.

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in 53% of our patients. MOF has recently been shown to bethe main cause of morbidity and mortality in patientsadmitted to ICUs, and has been calculated to account for upto 80% of ICU deaths.19

In an Australasian study, MOF was the cause of death in20.3% of patients admitted to the ICU with severe nonin-fectious systemic inflammatory response syndrome and in69% of patients with severe sepsis.20 In a large prospectivestudy performed in a population of mainly surgical criti-cally ill patients, acute or chronic MOF prevailed as thecause of death in the ICU.13 In a study on macroscopicpostmortem findings in surgical intensive care patientswith sepsis, the main causes of death as reported in thepatient history were refractory MOF in 51.5%.21

The multivariable analysis confirmed that tachycardia,high CVP and serum lactate levels, and pH on the day ofadmission to the ICU are early predictors of death due toMOF. Moreover, we found that unplanned surgery, perito-nitis, older age, and the presence of diabetes significantlyincreased the risk of death due to MOF.

Tachycardia, lactic acidosis, or acidosis due to othercauses, such as hyperchloremic acidosis, are common oc-currences after major surgery. These factors are undoubt-edly related to traumatic and long operations, with anenhanced systemic inflammatory response, inadequate re-suscitation, and tissue hypoperfusion. Our findings areconsistent with numerous studies that have demonstratedan association between organ hypoperfusion and indices oftissue trauma and organ dysfunction.22,23 Likewise, studiesin surgical ICU patients, and in patients with infection,sepsis, and shock have reported worse outcomes related tohigher serum lactate concentrations.24–28 Prolonged lactateclearance is related to increased mortality after surgery,and lactate nonclearance during resuscitation was a strongindependent predictor of in-hospital death in patients withsevere sepsis.29–31

Importantly, we found a 12% increase in the risk ofdeath due to MOF for each unit increase in CVP. Tradition-ally, cardiac filling pressures have been used to assessvolume status in critically ill patients. The observationaldesign of our study does not allow us to conclude whetherelevated CVP levels represented excessive intravascularvolume, poor cardiovascular reserve, or both. Moreover, inmore complex cases, the presence of external or intrinsicpositive end-expiratory pressure, abdominal hypertension,compromised left ventricular compliance, which is fre-quently decreased in ICU patients with sepsis, ischemic orhypertrophic cardiopathy, can increase CVP measurementseven in the presence of hypovolemia. Nevertheless, severalstudies have associated a positive fluid balance with com-plications and death in ICU patients.32

MOF development in patients imposes a heavy burdenon staff and resources, and patients have long ICU lengthsof stay and high costs. Awareness of early risk factors forMOF would be valuable if changes in clinical managementcould be prompted by potentially avoidable predictors ofpoor outcome. Several important clinical trials have docu-mented that early aggressive resuscitation using well-defined protocols, such as goal-directed therapy (GDT),improves outcomes and is cost effective.33–40 These studies

have used therapeutic strategies aimed at boosting cardio-respiratory function and maintaining end-organ perfusionthrough a more individualized and targeted fluid therapyand reported reductions in the length of ICU and hospitalstay, a faster recovery of gastrointestinal function, and areduction in mortality when GDT was performed in higherrisk surgical patients.41

The mortality rate in our study was higher than thatpredicted by the POSSUM score. All scoring systems thatwe evaluated had the same capacity of predicting hospitalmortality in this population of surgical patients admitted tothe ICU postoperatively. Unfortunately, in our country,early GDT, best known in this set of patients as optimiza-tion of oxygen delivery, is still not widely used in clinicalpractice despite the growing body of evidence. As a conse-quence of our findings and the high mortality observed inthis population of surgical patients, we recommend se-quential measurements of serum lactate, pH, and CVP to beused in the context of well-defined protocols of optimiza-tion of oxygen delivery to guide adjustments of IV fluidadministration and use of dobutamine to maintain a maxi-mal stroke volume in the perioperative period.34–39

Age has been reported to be independently associatedwith MOF in medical patients and in heterogeneous popu-lations of critically ill patients, with death in patients withsystemic inflammatory response syndrome and MOF, andwith post-ICU mortality in surgical ICU patients.12,20,42,43

Serum glucose levels were tested in the logistic regressionmodel but were not retained; however, a history of diabeteswas a strong predictor increasing the odds of MOF by 3.63.Diabetes mellitus is a chronic, systemic debilitating condi-tion that affects many organ functions, increases the likeli-hood and extent of coronary artery disease, and increasesthe likelihood of infections. Other studies have shown thatglucose levels and glucose variability, rather than diabetes,were important factors associated with organ dysfunc-tion.44,45 Hyperglycemia was independently associatedwith organ failure and death in critically ill children.46

Unplanned surgery increased the odds of death due toMOF by almost 4-fold. Indeed, in a prospective, observa-tional, Australian study, performed in 1125 subjects under-going surgery in a tertiary teaching hospital, unplannedICU admission increased the risk of death by 4-fold.47

Other studies have shown emergency surgery to be animportant predictor of mortality in older patients.48

Peritonitis was an independent predictor of death due toMOF. A total of 141 patients (24.0%) had peritonitis, of whom18.4% developed sepsis within 48 hours of ICU admission.When sepsis progresses to sepsis-associated organ failure andhypotension, mortality increases from 27% to �50% in pa-tients with septic shock.49 Severe sepsis occurred in 23% of thepatients in our cohort of high-risk surgical patients, with ahospital mortality rate of 64%. The nosocomial sepsis that is sotypical of the later course of such patients in the ICU can occuras a consequence of organ dysfunction, prolonging their stayand increasing the risk of infection.

This study is limited by the relatively small number ofpatients and ICUs. However, although the size of the studywas relatively modest, its selected study group is more likelyto represent real surgical practice. Despite the large size of ourcountry, all regions were represented. Our cohort was a

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population of high-risk surgical patients as demonstrated bythe frequent prevalence of comorbid diseases and unplannedsurgery, high degrees of physiologic derangement as shownby the high POSSUM and APACHE II scores, and thecorrespondingly high mortality rates. Bed shortages in Brazil-ian hospital ICUs may be the cause of the admission of higherrisk cases than in some other countries.

In conclusion, the vast majority of deaths in this high-risk population of surgical patients were due to MOF. Weidentified several routinely available variables as strongpredictors of the development of a fatal outcome due toMOF in our high-risk surgical ICU patients.

AUTHOR AFFILIATIONSFrom the *Intensive care Unit, Hospital de Base and SaoJose do Rio Preto Medical School; †Intensive Care Unit,Hospital do Servidor Publico Estadual Francisco Morato deOliveira, Sao Paulo; ‡Intensive Care Unit, Hospital SaoLucas and Hospital Cardiotrauma Ipanema, Rio de Janeiro;§Intensive Care Unit, Hospital Moinhos de Vento, PortoAlegre; �Intensive Care Unit, Clínica Sorocaba, Rio deJaneiro; ¶Intensive Care Unit, Clínica Sao Vicente, Rio deJaneiro; #Adult Intensive Care Unit, Hospital Universitarioda Universidade Federal da Paraíba, Joao Pessoa; **Depart-ment of Anesthesiology, Pain and Intensive Care, Univer-sidade Federal de Sao Paulo, Sao Paulo; ††Intensive CareUnit, Hospital Pro-Cardíaco, Rio de Janeiro; ‡‡IntensiveCare Department, Universidade Estadual de Londrina,Londrina; §§Intensive Care Unit, Hospital Universitario daUniversidade Federal do Mato Grosso do Sul, CampoGrande; ��Universidade Estadual do Piauí, Teresina; ¶¶In-tensive Care Unit, Hospital Santa Luzia, Brasília; ##MedicalSchool, Universidade Estadual do Oeste do Parana, Cas-cavel; ***Hospital do Servidor Publico Estadual FranciscoMorato de Oliveira, Sao Paulo; †††Intensive Care Unit,Santa Casa de Misericordia, Passos; ‡‡‡Medical School ofSao Jose do Rio Preto, Sao Jose do Rio Preto, Brazil; and§§§Department of Intensive Care, Erasme Hospital, FreeUniversity of Brussels, Brussels, Belgium.

AUTHOR CONTRIBUTIONSSML and ER helped in study design and manuscriptpreparation; MFK, NBS, JAP, CLM, FEN, MA, RCC, CCG,SFP, PMM, MOM, PAD, FG, and MRL helped in conduct ofstudy; JMS helped in data analysis and conduct of study;and JAC and CM helped in data analysis.

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