Glucose in Trauma Tarik Sammour, Arman Kahokehr Stuart Caldwell, Andrew G Hill MIDDLEMORE HOSPITAL Auckland, NZ

Middlemore Trauma Registry Started May 2000 Prospectively collected All admissions > 24h Maintained by nurse specialist and fellow Currently 20,500 entries Records ISS and TRISS scores Firstly some background on Middlemore. It covers a population of 460,000 ppl in S Auckland. Approx 2500 trauma admissions per year (includes minor injuries admitted >24h). Trauma registry started in May 2000 as a prospectively collected database of trauma outcomes. Based on Collector for Windows Data Management System version 3.37, Digital Innovation Inc, Maryland, USA 20500 entries as of April 2008. Collector records ISS (Injury Severity Score) and TRISS (Trauma and Injury Severity Score).

Utility of Trauma Scores Predict mortality Patient disposition (need for ICU?) Counselling patient and family However… Complex to calculate in acute situtation Mainly used in audit and research Many trauma scores have been developed. Main drawback to all of them is difficult to calculate in the hustle and bustle of ED due to complexity and missing values.

Calculating trauma scores 6 body regions Score each from 1 - 6 ISS (Region A)² + (Region B)² + (Region C)² TRISS ISS + (physiological parameters) + age ISS developed in the 70’s by Baker is the most widely used score, and the main one used in our registry. Derived from Abbreviated Injury Severity (AIS) coding, AIS divides the body into 6 regions, Sum of the squares of the AIS severity measure in the three most injured body regions Good score but has some limitations… TRISS current international standard Includes GCS, systolic BP, respiratory rate, and age.

Limitations of current scores ISS Statistical: Ordinal rather than continuous score Score is not monotonous e.g. Kilgo et al. mortality of 43% with ISS 25, and only 14% with an ISS of 27 (a worse score) Clinical: No measure of physiological compromise TRISS (ISS plus physiological parameters) Requires atleast 8, and as many as 10 variables => missing values common ISS is scaled from 1 to 75 but actually only takes 44 distinct values which are not uniformly distributed. Because of this, ISS cannot be treated as a continuous measure but rather as an ordinal scale. Kilgo et al (J Trauma. 2006;60:1002–1009) demonstrated in analysis of over 350,000 trauma patients that ISS scores do not represent monotonically increasing functions of mortality. TRISS More variables = more missing data.

Glucose metabolism in Trauma Blood glucose level increases Overproduction of endogenous glucose Relatively low insulin production Lactate level increases Shift to anaerobic metabolism Reduction in lactic acid elimination Aerobic glycolysis in skeletal muscle secondary to epinephrine stimulated ATPase activity So we hypothesised that and increase in glucose and lactate levels may be an early predictor of mortality.

Question Can we utilise glucose and lactate levels to predict mortality in trauma patients?

Method Trauma registry search Time period: May 2000 – Sept 2006 Inclusion: All adult patients requiring a trauma team call out Exclusions: Diabetics and Burns Data collected Demographics Background medical history Admission glucose and lactate ISS and TRISS scores Mortality

Patients included Male 892 (74.5%) Female 305 (25.5%) Mechanism of Injury Number Road traffic accident 746 Assault 152 Fall 102 Animal Related 7 Work related 38 Sport 18 Self inflicted 60 Unknown 74 Male 892 (74.5%) Female 305 (25.5%) Mortality rate 3.7%

Mechanism Mechanism of Injury Number Road Traffic Accident 746 Assault 152 Fall 102 Self Inflicted 60 Work related 38 Sport 18 Animal related 7 Unknown 74

Data ranges Missing Values Median (Range) Age ISS TRISS Gluc Lact 31 (15 – 90) ISS 9 (1 – 75) 7 TRISS 0.972 (0.001 – 0.997) 201 Gluc 6.9 (3.1 – 31.4) 120 Lact 1.9 (0.5 – 18) 847 Out of 1200 patients There were 200 TRISS values (1/6th) that couldn’t be calculated because of missing data Also, 70% of patients didn’t have a lactate level presumably as it was not clinically indicated.

Results - Glucose Glucose > 11.0 mmol/L defined as elevated Gluc > 11.0 mmol/L => mortality rate 13.4% Gluc < 11.0 mmol/L => mortality rate 1.8% (p < 0.0001). Specificity 93.2% for death. Sensitivity 37.9% for death. Positive predictive value (PPV) was low (13.4%) Negative predictive value (NPV) was high (98.2%) 996 gluc < 11 82 gluc > 11 Approx 100 patients had gluc > 11

Results - Lactate Lactate > 2.0 mmol/L defined as elevated Lact > 2.0 mmol/L => mortality rate 13.0% Lact < 2.0 mmol/L => mortality rate 2.7% (p = 0.0003). Specificity 56.8% for death. Sensitivity 81.0% for death. Positive predictive value (PPV) was low (13.0%) Negative predictive value (NPV) was high (97.4%) 189 Lact < 2 160 Lact > 2 Sens higher and spec lower because sick patients were pre-selected.

Combining gluc and lact Neither elevated Gluc or Lact Both Mortality 2.9% 7.6% 25.5% Specificity of 60.7% Sensitivity of 70.0%

Some aberrant results at v high glucose => combined into one group > 17.

Generally accepted threshold for a good predictive test is 0.8. Glucose level meets the threshold, with a predictive value similar to that of the ISS score. TRISS score is an exceptional predictor deserving of it status as international standard and lactate is somewhat less predictive (although this only included one third of the patients). Gluc 0.845 std error 0.030 => (0.787 – 0.903). Maximal sens and spec at Gluc 8.5 => sens 75.9%, spec 75.8%. Gluc < 8.5 => 1.5% of 802 died, Gluc >= 8.5 => 8.0% of 276 died. ISS 0.854 std error 0.030 => (0.796 – 0.912) TRISS 0.963 std error 0.013 => (0.938 – 0.987) lact 0.716 std error 0.060 => (0.598 – 0.834). Maximal sens and spec at Lact 2.4 => sens 65.4%, spec 63.9%

Conclusions Glucose and lactate can predict mortality in severely injured patients. Venous glucose is a good predictive test and equivalent to the ISS score. It is easier to obtain and more practical to use in the emergency setting. Limitations: Retro review Trauma registry data input is inaccurate Lots of missing lactate data Previous analysis of 450 patients that died or went to ICU – no trauma call in 17%