The Obesity Paradox in Surgical Intensive Care Unit Patients

Robert Hutagalung MD, Juliana Marques MD, Kathrin Kobylka MD,

Mohamed Zeidan MD PhD, Bjorn Kabisch PhD, Frank Brunkhorst MD, Konrad Reinhart MD, Yasser Sakr MD PhD

From the Department of Anesthesiology and Intensive Care,

FriedrichSchillerUniversityHospital, Jena, Germany

Electronic Supplementary Materiel

Table E1: Baseline characteristics and outcome in patients included in the study and those who were excluded.

Excluded patients / Included patients / p-value
(n =3001) / (n=9937)
Sex, male (%) / 1769 (58.9) / 6407 (64.5) / <.0001
Age, years / 61.2 ± 16.8 / 62.9 ± 14.3 / <0.001
Severity score, mean ± SD
SAPS II / 33.1 ± 17.9 / 39.8 ± 18.5 / <0.001
SOFA / 4.3 ± 3.6 / 6.5 ± 3.8 / <0.001
Surgical procedures (%) / <0.001
Gastrointestinal / 709 (23.6) / 2086 (21.0)
Cardiothoracic / 566 (18.9) / 4650 (46.8)
Neurosurgical / 657 (21.9) / 1262 (12.7)
Trauma / 198 (6.6) / 336 (3.4)
Others / 302 (10.1) / 707 (7.1)
Medical / 569 (19.0) / 896 (9.0)
Comorbid diseases (%)
Diabetes mellitus / 1415 (47.2) / 5334 (53.7) / <0.001
Hypertension / 287 (9.6) / 2498 (25.1) / <0.001
Cirrhosis / 87 (2.9) / 385 (3.9) / 0.013
Cancer / 662 (22.1) / 1839 (18.5) / <0.001
Renal failure / 175 (5.8) / 891 (9.0) / <0.001
Heart failure (NYHA III-IV) / 157 (5.2) / 589 (5.9) / <0.001
ICU mortality (%) / 157 (5.2) / 589 (5.9) / 0.152
Hospital mortality (%) / 306 (10.2) / 1024 (10.3) / 0.889
ICU length of stay, days, median [IQ] / 1 [1-3] / 1 [1-3] / 0.296

NYHA: New York heart association classification, SAPS II, simplified acute physiology score; SOFA, Sequential Organ Failure Assessment.

Table E2: Cox-regression multivariate analysis according to the admission category with in-hospital 60-day mortality as the dependent variable.

Surgical, elective / Surgical, emergency / Medical
HR (95% CI) / P-value / HR (95% CI) / P-value / HR (95% CI) / P
Female / 1.05 (0.85 - 1.29) / 0.652 / 1.12 (0.89 - 1.40) / 0.340 / 1.15 (0.86 - 1.55) / 0.343
Age (per year) / 1.03 (1.02 - 1.04) / < 0.001 / 1.01 (1.004 - 1.02) / 0.004 / 1.01 (1.00 - 1.02) / 0.070
Comorbid disease
Diabetes / 1.15 (0.93 - 1.42) / 0.185 / 1.04 (0.82 - 1.31) / 0.770 / 1.02 (0.76 - 1.37) / 0.887
Hypertension / 1.14 (0.90 - 1.44) / 0.288 / 0.91 (0.67 - 1.25) / 0.570 / 0.56 (0.35 - 0.90) / 0.015
Cirrhosis / 1.71 (1.17 - 2.48) / 0.005 / 1.12 (0.74 - 1.69) / 0.601 / 1.37 (0.93 - 2.03) / 0.116
Cancer / 1.45 (1.12 - 1.87) / 0.004 / 1.36 (1.01 1.84) / 0.045 / 1.29 (0.89 - 1.88) / 0.183
Renal failure / 1.70 (1.33 - 2.18) / < 0.001 / 1.43 (1.10 - 1.84) / 0.007 / 1.48 (1.08 - 2.01) / 0.013
Heart failure / 1.30 (1.01 - 1.68) / 0.042 / 1.60 (1.15 - 2.24) / 0.006 / 0.98 (0.63 - 1.52) / 0.921
Severity scores
SAPSII (per point)* / 1.04 (1.03 - 1.04) / < 0.001 / 1.04 (1.04 - 1.05) / < 0.001 / 1.03 (1.03 - 1.04) / < 0.001
SOFA (per point)* / 1.18 (1.15 - 1.21) / < 0.001 / 1.18 (1.14 - 1.22) / < 0.001 / 1.15 (1.11 - 1.19) / < 0.001
Surgical procedure
Cardiothoracic / Reference / Reference / NA / NA
Gastrointestinal / 1.93 (1.46 - 2.55) / < 0.001 / 1.50 (1.11 - 2.04) / 0.009 / NA / NA
Neurosurgical / 1.53 (1.01 - 2.32) / 0.046 / 1.50 (1.08 - 2.09) / 0.016 / NA / NA
Trauma / 2.64 (1.46 - 4.80) / 0.001 / 0.93 (0.57 - 1.51) / 0.761 / NA / NA
Other / 1.18 (0.79 - 1.75) / 0.418 / 1.61 (1.07 - 2.40) / 0.021 / NA / NA
BMI category
Normal BMI / Reference / Reference / Reference
Underweight / 1.29 (0.68 - 2.47) / 0.435 / 1.60 (0.90 - 2.84) / 0.113 / 1.36 (0.54 - 3.41) / 0.518
Overweight / 0.85 (0.68 - 1.06) / 0.154 / 0.76 (0.59 - 0.98) / 0.038 / 1.16 (0.85 - 1.58) / 0.362
Obese / 0.70 (0.53 - 0.93) / 0.013 / 1.06 (0.78 - 1.43) / 0.712 / 0.80 (0.52 - 1.20) / 0.280
Very obese / 1.54 (0.83 - 2.87) / 0.172 / 1.37 (0.67 - 2.82) / 0.391 / 0.59 (0.22 - 1.64) / 0.316

BMI, Body mass index; CI: confidence interval; HR, hazard ratio; NA, non applicable; SAPS II, simplified acute physiology score; SOFA, Sequential Organ Failure Assessment

* SOFA, was introduced in the model instead of SAPS II (alternately) due to collinearity.

Table E3: Cox-regression multivariate analysis according to the major surgical intervention with in-hospital 60-day mortality as the dependent variable.

Cardiothoracic / Gastrointestinal / Neurosurgical
HR (95% CI) / P-value / HR (95% CI) / P-value / HR (95% CI) / P-value
Female / 1.00 (0.77 - 1.30) / 0.977 / 1.21 (0.94 - 1.56) / 0,135 / 0.76 (0.50 - 1.15) / 0.192
Age (per year) / 1.01 (1.002 - 1.03) / 0.025 / 1.03 (1.01 - 1.04) / < 0.001 / 1.00 (0.98 - 1.01) / 0.726
Comorbid disease
Diabetes / 1.03 (0.79 - 1.35) / 0.808 / 1.10 (0.85 - 1.42) / 0.467 / 1.56 (1.01 - 2.40) / 0.046
Hypertension / 1.24 (0.95 - 1.63) / 0.115 / 1.11 (0.78 - 1.57) / 0.552 / 1.02 (0.57 - 1.80) / 0.954
Cirrhosis / 2.65 (1.55 - 4.54) / < 0.001 / 0.99 (0.67 - 1.46) / 0.960 / 3.3 (1.40 - 7.81) / 0.006
Cancer / 1.95 (1.27 - 3.01) / 0.002 / 1.43 (1.11 - 1.84) / 0.006 / 1.60 (0.88 - 2.91) / 0.121
Renal failure / 2.11 (1.59 - 2.78) / < 0.001 / 1.41 (1.05 - 1.90) / 0.024 / 0.83 (0.41 - 1.67) / 0.598
Heart failure / 1.31 (0.99 - 1.73) / 0.06 / 1.60 (1.07 - 2.39) / 0.021 / 2.09 (0.93 - 4.70) / 0.074
Admission severity scores
SAPSII (per point)* / 1.04 (1.03 - 1.05) / < 0.001 / 1.03 (1.03 - 1.04) / < 0.001 / 1.07 (1.05 - 1.09) / < 0.001
SOFA (per point)* / 1.22 (1.17 - 1.27) / < 0.001 / 1.16 (1.13 - 1.20) / < 0.001 / 1.29 (1.23 - 1.37) / < 0.001
Type of admission
Surgical, elective / Reference / Reference / Reference
Surgical, emergency / 1.43 (1.07 - 1.92) / 0.016 / 1.08 (0.82 - 1.41) / 0.582 / 1.05 (0.64 - 1.72) / 0.848
BMI category
Normal BMI / Reference / Reference / Reference
Underweight / 1.63 (0.65 - 4.09) / 0.294 / 2 (1.11 - 3.61) / 0.021 / 2.93 (0.68 - 12.57) / 0.148
Overweight / 0.86 (0.65 - 1.15) / 0,313 / 0.75 (0.56 -1.00) / 0.051 / 0.96 (0.62 - 1.50) / 0.860
Obese / 0.79 (0.56 - 1.11) / 0.174 / 0.99 (0.71 - 1.39) / 0.975 / 0.82 (0.43 - 1.54) / 0.531
Very obese / 1.46 (0.67 - 3.21) / 0.34 / 1.55 (0.71 - 3.39) / 0.268 / 3.00 (1.06 - 8.48) / 0.039

BMI, Body mass index; CI: confidence interval; HR, hazard ratio; SAPS II, simplified acute physiology score; SOFA, Sequential Organ Failure Assessment

* SOFA, was introduced in the model instead of SAPS II (alternately) due to collinearity.

Figure E1. Histogram representing the distribution of body mass index in the study population

Figure E2: Adjusted hazard ratios for in hospital 60-day mortality (with normal BMI as the reference category) classified according to the admission categoryies;:elective surgeryies (closed circles); emergency surgeryies (closed triangles), and admission due to medical reasons in patients who underwent surgery within 4 weeks prior to ICU admission (crosses).

* p<0.05

Figure E3: Adjusted hazard ratios for in hospital 60-day mortality (with normal BMI as the reference category) classified according to the major surgical intervention:;cardiothoracic surgery (closed circles), gastrointestinal surgery (closed triangles), and neurosurgery (diamonds).

* p<0.05