Participants
Over the three-year period between 20/1/14 to 30/12/16, 4495 patients met the trauma call criteria and 1539 patients had ROTEM FIBTEM performed. One patient’s data was removed due to implausible ROTEM results and 13 patients did not have an A10 value recorded. This left 1525 patients for the primary analysis (Fig1).
Of the 1525 patients used for primary analysis, 1124 (73.70%) were male. All continuous variables displayed non-normal distributions. Median age was 37 years (interquartile range [IQR] 25 - 54). Blunt trauma comprised the main mechanism of injury, present in 1391 (91.21%) cases. 474 patients (31.08%) were classified as major trauma (ISS ≥ 12) and 123 (8.07%) received packed red cell transfusions in the first 24 hours from arrival. Further descriptive statistics can be found in Table 1.
In the whole cohort, median (IQR) FIBTEM A5 values were 13 (10 – 16) mm and A10 values 14 (11 – 18) mm; laboratory-measured Clauss fibrinogen was 2.9 (2.5 – 3.4) g/l. ROTEM values for the subgroups are displayed in Table 2.
|
N or Median
|
% or IQR
|
Total
|
1525
|
100
|
Age
|
37
|
25 – 54
|
Male
|
1124
|
73.70%
|
Female
|
401
|
26.30%
|
ISS
|
5
|
1 - 14
|
ISS ≥ 12
|
474
|
31.08%
|
Died < 24 hr
|
12
|
0.79%
|
Mechanism
|
|
Blunt
|
1391
|
91.21%
|
Penetrating
|
119
|
7.80%
|
Burns
|
12
|
0.79%
|
Immersion
|
3
|
0.20%
|
PRBC transfusion in 24 hr
|
123
|
8.07%
|
Massive transfusion (≥ 10 units PRC)
|
14
|
0.92%
|
Initial Blood Results
|
|
|
INR
|
1.0
|
1.0 - 1.1
|
INR > 1.3
|
47
|
3.08%
|
pH
|
7.36
|
7.32 - 7.39
|
pH < 7.30
|
197
|
12.9%
|
Base excess (mmol/l)
|
0.0
|
-1.8 - 1.4
|
Base excess < -2.0 mmol/l
|
262
|
17.2%
|
Lactate (mmol/l)
|
1.7
|
1.2 - 2.6
|
Lactate > 2.5 mmol/l
|
307
|
20.1%
|
Table 1: Descriptive statistics of cohort. Values given as a count with percentage of total or as median (interquartile range). IQR (interquartile range), ISS (injury severity score), PRC (packed red cell), INR (international normalised ratio)
|
n
|
A5 median (IQR) mm
|
A10 median (IQR) mm
|
Clauss Fibrinogen median (IQR) g/l
|
Whole cohort
|
1525
|
13 (10 - 16)
|
14 (11 - 18)
|
2.9 (2.5 - 3.4)
|
No PRC
|
1402
|
13 (10 - 16)
|
14 (12 - 18)
|
3.0 (2.6 - 3.5)
|
1 - 3 PRC
|
65
|
14 (10 - 19)
|
14 (11 - 21)
|
2.8 (2.3 - 3.3)
|
4 - 9 PRC
|
44
|
10 (6.8 - 13)
|
10.5 (7.8 - 13.3)
|
2.0 (1.5 - 2.6)
|
≥ 10 PRC
|
14
|
8.5 (5.3 - 12)
|
9.5 (6.3 - 14)
|
2.5 (1.2 - 2.9)
|
ISS 0 - 8
|
846
|
13 (10 - 16)
|
14 (11 - 18)
|
2.9 (2.5 - 3.5)
|
ISS 9 - 11
|
206
|
13 (10 - 16)
|
14 (11 - 17)
|
3.0 (2.5 - 3.4)
|
ISS ≥ 12
|
473
|
13 (10 - 16)
|
14 (11 - 18)
|
2.9 (2.3 - 3.4)
|
Table 2: ROTEM FIBTEM and laboratory-measured Clauss Fibrinogen for the whole cohort and for sub-groups. Sub-groups by packed red cell transfusion quantity in the first 24 hours and by ISS. A5 (amplitude at 5 minutes), IQR (interquartile range), A10 (amplitude at 10 minutes), PRC (packed red cell units transfused in 24 hr), ISS (injury severity score)
Primary Outcomes
In the whole cohort A5 and A10 values had an ICC of 0.972 (95% CI 0.969 – 0.975). ICC values above 0.90 are considered to represent an excellent level of agreement [19].
ICCs reflecting excellent agreement levels were also observed in all sub-groups when broken down by numbers of PRC transfused in 24 hours or ISS (Table 3). Within the massive transfusion group (n = 15) the A5-A10 ICC was 0.987 (0.962 – 0.996). In patients with major trauma (n = 473) the A5 A10 ICC was 0.972 (0.966 – 0.976).
Bland-Altman plots were also constructed to indicate agreement and plots for the whole cohort and the subgroups of massive haemorrhage and major trauma (Figure 2).
|
|
|
95% Confidence Intervals
|
|
n
|
ICC
|
Lower CI
|
Upper CI
|
Whole cohort
|
1525
|
0.972
|
0.969
|
0.975
|
No transfusion
|
1402
|
0.970
|
0.966
|
0.973
|
1 - 3 PRCs
|
64
|
0.984
|
0.974
|
0.990
|
4 - 9 PRCs
|
44
|
0.992
|
0.985
|
0.995
|
≥ 10 PRCs
|
15
|
0.988
|
0.963
|
0.996
|
ISS 0 - 9
|
846
|
0.973
|
0.969
|
0.976
|
ISS 9 - 11
|
206
|
0.969
|
0.959
|
0.976
|
ISS ≥ 12
|
473
|
0.972
|
0.966
|
0.976
|
Table 3: Intraclass correlation values and confidence intervals for A5 A10 comparison in sub-groups split by quantity of packed red cell transfusions in the first 24 hours and by Injury Severity Score. ICC (intraclass correlation), CI (95% confidence interval), PRC (packed red cells), ISS (Injury Severity Score)
Secondary Outcomes
From the whole cohort Bland-Altman plot the calculated bias (mean difference) between A10 and A5 values was observed to be 1.49 mm (95% CI 1.43 -1.56 mm) indicating the average A10 value was 1.49 mm greater than its counterpart A5 value.
295 (19.34%) patients met the original local ROTEM threshold (A10 < 11 mm) for fibrinogen replacement. 424 (27.80%) patients met the current ROTEM threshold (A5 < 11 mm) for fibrinogen replacement (see Additional File 1). A minority of patients in both groups actually received fibrinogen replacement (indicating that they had met the second clinical criterion of active bleeding): 45 (2.95% of total) and 51 (3.34% of total) patients respectively.
The calculated new trial threshold for A5 (after subtracting the bias from the original A10 threshold of < 11 mm) was A5 < 10 mm (rounded to the nearest integer due to the precision of the ROTEM machine readouts). Using this new threshold 294 (19.28%) patients would have met the ROTEM criterion for fibrinogen replacement. Numbers of patients meeting these criteria are displayed in Table 4.
|
Current Threshold
|
Original Threshold
|
New Threshold
|
|
A5 < 11 mm
|
A10 < 11 mm
|
A5 < 10 mm
|
Met ROTEM threshold
|
424 (27.80%)
|
295 (19.34%)
|
294 (19.28%)
|
Fibrinogen replaced
|
51 (3.34%)
|
45 (2.95%)
|
47 (3.08%)
|
Fibrinogen not replaced
|
373 (24.46%)
|
250 (16.39%)
|
247 (16.20%)
|
Table 4: Summary of numbers of patients from the whole cohort who would have met different ROTEM FIBTEM fibrinogen replacement thresholds and which of those patients actually received fibrinogen replacement. Current local guidelines recommend fibrinogen replacement when A5 < 11 mm AND there is a clinical assessment of significant bleeding.