Post on 26-Jan-2019
1
Intraoperative changes in platelet function in relation to moderate
haemorrhage
Authors: Jonathan J Hetherington, Aberdeen Royal Infirmary, NHS Grampian,
Isobel Ford, School of Medicine & Dentistry, University of Aberdeen
G Patrick Ashcroft, School of Medicine & Dentistry, University of Aberdeen
Jan O Jansen, Aberdeen Royal Infirmary, Aberdeen & Health Services
Research Unit, University of Aberdeen, Aberdeen, Scotland
Corresponding Author: Dr J Hetherington
Address: Anaesthetics Dept, Aberdeen Royal Infirmary, Aberdeen, Scotland AB25 2ZN
Email: jonathan.hetherington@nhs.net
2
AbstractBackground: Haemorrhage is associated with haemostatic dysfunction. Previous studies
have focused on coagulation factors, but platelet function plays an equally important role.
The time course of alterations in platelet function in relation to injurious stimuli is not known.
Aim: To evaluate short-term, intra-operative changes in platelet function, by whole blood
impedance aggregometry in patients undergoing hip arthroplasty. The primary outcome was
platelet aggregation in response to adenosine diphosphate (ADP) stimulation. We also
evaluated other agonists, and the feasibility of conducting platelet aggregometry
measurement in the operating theatre.
Methods: Patients undergoing primary cemented hip arthroplasty had six peri-operative
arterial blood samples analysed at pre-set stages of the operation, using the Multiplate®
Impedance Aggregometer. Four agonists were used: ADP, TRAP, Collagen and Arachidonic
Acid.
Results: There was a statistically significant change (p<0.05, ANOVA) in platelet response
to ADP over the course of the operations. The trend demonstrated an initial decrease in
responsiveness, followed by increased platelet responsiveness in the later stages. Other
agonists (TRAP, COL, ASPItest) demonstrated similar pattern of changes. Of 360 tests
conducted, 12 (3.3%) had to be re-run due to poor intra-assay variability. Satisfactory values
were obtained on the second attempt in all 12 samples.
Conclusion: Platelet function, as measured by impedance aggregometry, changes in response
to a surgical stimulus involving blood loss. The clinical significance of these changes, and the
potential of manipulating them for therapeutic purposes, remains to be elucidated.
3
Word count: 231 Keywords: Keywords: Haemorrhage, platelet aggregation, platelet function
tests, surgery
UKCRN Number: 13815
4
IntroductionChanges to the coagulability of blood in response to stimuli such as haemorrhage, trauma,
and surgery, are well recognised. Post-operatively, or following minor injury, patients are
more likely to develop thromboembolic complications, due to increased coagulability (1).
Conversely, haemorrhage-associated haemostatic dysfunction is now increasingly recognised.
(2,3)Error: Reference source not foundInitial efforts to elucidate the underlying mechanisms
for this change have focused on the roles of activated Protein C and hyperfibrinolysis (4,5).
Error: Reference source not foundPlatelet function has received less attention, although
recent studies have demonstrated an association between acute traumatic coagulopathy and
platelet aggregability, (6) and platelets are regarded as an integral part of the coagulation
system.
The assessment of platelet function is difficult, accounting for the paucity of studies in this
area. Flow cytometry and light transmission aggregometry are the techniques of choice in the
research laboratory, but require considerable operator training and experience. These methods
are also labour-intensive and time-consuming, making the rapid analysis of sequential
samples in a clinical or emergency setting difficult. Over the last decade, impedance
aggregometry has emerged as a more user-friendly alternative. Initially developed to
demonstrate platelet inhibition in cardiovascular patients receiving antiplatelet therapy, this
technique – whereby the rate of aggregation of platelets between electrodes is measured –
shows promise in the assessment of intrinsic platelet dysfunction.
Through the utilisation of a number of agonists to induce platelet aggregation an assessment
of platelet function can be made. Adenosine diphosphate (ADP) in particular has a substantial
contribution to the propagation of platelet activation at the site of injury (7) and the clinical
5
effectiveness of antiplatelet agents acting at the P2Y12 receptor in reducing thromboembolic
phenomena highlights the clinical importance of this pathway (8).
In summary, there is evidence that platelet function is affected by tissue trauma and
haemorrhage (6,9), and that these changes are associated with poor outcome(9,10)(6). There
is also some evidence that platelet function may change earlier and more rapidly than was
previously assumed (11). However, for technical reasons these changes are difficult to
demonstrate.
We hypothesised that some of the changes in platelet function noted in injured patients may
also take place in response to planned surgery associated with blood loss, reflecting decreased
platelet responsiveness secondary to trauma and haemorrhage. The aim of this study was to
elucidate short-term changes in platelet function, as measured by stimulated impedance
aggregometry, in response to moderate blood loss, during the course of an elective operation.
6
MethodsThis was a prospective observational study. The study protocol was approved by the North of
Scotland Research Ethics Service (reference NS/12/0095). We identified patients scheduled
to undergo primary cemented hip arthroplasty at the pre-operative assessment clinic between
January 1st 2013 and July 31st 2013. Patients with a known platelet or coagulation disorder or
diabetes, and those taking warfarin were excluded. Study information was distributed to
patients in advance, and written consent obtained following a period of consideration of at
least seven days. Patients receiving antiplatelet drugs had their medication withheld as per the
routine practice of the operating surgeon (3-10 days prior to commencement of surgery).
On arrival in the anaesthetic room, baseline physiological parameters were recorded, and a
radial arterial cannula inserted under local anaesthetic, to facilitate intra-operative sampling.
Patients were then anaesthetised and underwent surgery. Blood samples were taken at six
time points during the perioperative period: Pre-operatively before administration of the
anaesthetic; on commencement of the skin incision; on removal of the femoral head; on
reaming of the femoral canal; on cementing of the femoral component of the prosthesis; and
following skin closure. Samples for full blood count and platelet function were drawn at each
time point via a Vacutainer system into tubes containing EDTA (3ml), citrate (2.7ml) and
hirudin (3ml) anticoagulants respectively. A single additional sample for measurement of
clottable fibrinogen was taken pre-operatively in the anaesthetic room. Platelet samples were
analysed immediately using the Multiplate® Impedance Aggregometer (Roche Diagnostics
International Ltd, Rotkreuz, Switzerland). 0.3 mL of whole blood was diluted in an equal
volume of warmed isotonic sodium chloride solution and incubated for 3 minutes at 37˚C
with continuous stirring by a magnetised chip in a customised test cell. Each cell contains two
sets of 3mm silver-coated copper wires, across which electrical resistance is measured.
7
Platelet adhesion to the electrodes is detected as increasing electrical impedance. Platelet
function was assessed using four agonists – ADPtest® (6.5M adenosine diphosphate, ADP),
TRAPtest® (32µM thrombin receptor activating peptide TRAP-6), COLtest® (3.2µg/mL
collagen), and ASPItest® (0.5mM Arachidonic Acid) (all final concentrations), all obtained
from Roche Diagnostics Ltd, Sussex, UK – in order to assess different pathways of platelet
activation. Agonist responses were reported as area under the aggregation curve in units
(AUC) during a 6-minute measurement period.
Full blood counts were analysed on a Siemens Advia 2120i by the hospital’s haematology
laboratory. Citrate samples taken pre-operatively were centrifuged at 2000 x g for 15 min on
completion of the operation, plasma separated and frozen at below -70oC, and batch-analysed
for clottable fibrinogen using a semi-automated Clauss method with reagents from Helena
Biosciences (Tyne And Wear, UK).
Estimated total blood loss was calculated using routine clinical methodology (swab weights,
suction loss and direct measurable losses). Data was collected on regular medication use,
drugs given intraoperatively, comorbidity and anaesthetic technique employed.
The primary outcome measure was ADP-induced platelet aggregation. Secondary outcomes
included aggregation in response to thrombin receptor activating peptide, arachidonic acid,
and collagen, as well as the feasibility of conducting repeated intraoperative impedance
aggregometry, measured in terms of the number of patients recruited (as a proportion of those
eligible), and the proportion in whom a complete set of results was obtained. Statistical
analyses were performed using SPSS Statistical Software Version 21 (IBM, Chicago, IL,
USA). Changes in platelet activity over time were assessed by analysis of variance using
repeated measures ANOVA. Descriptive statistics were performed on clinical, platelet and
8
biochemical parameters. Correlation between the primary measure of ADP-stimulated
platelet aggregation and blood loss was investigated using Spearman’s rank correlation.
As this was a pilot study, we did not perform a sample size calculation. However previous
work by our group showed a statistically significant difference (p<0.05) in pre vs. post-op
platelet activation measures in 10 hip surgery patients (% platelets expressing P-Selectin: pre
1.0 (0.29-3.47); immediately post-op 0.53 (0.13-2.27); median (IQR)). We therefore believe
a group of 20 patients will be adequate to detect a significant difference and to provide data
to inform further studies.
9
ResultsRecruitment
In all, 53 eligible patients were identified at the pre-assessment clinic. The recruitment
process can be seen in the flowchart in figure 1.
Demographics and medication
The baseline characteristics of the study population are shown in table 1. The median age was
69 years (range 56-78 years), with nine males and six females. Four patients had previously
received anti-platelet therapy with aspirin, which had been discontinued at 3, 5, 7 and 10 days
before surgery. None had been taking thienopyridines.
All patients were undergoing hip replacement for osteoarthritis of the hip. One patient had
concurrent rheumatoid arthritis, which was documented to be well controlled on
methotrexate.
The first patient received their operation in March 2013 with the final study patient
completing surgery in late August 2013. All patients received spinal anaesthesia, but one
required conversion to a general anaesthetic prior to commencement of surgery. Median
operation time was 2h1min (range 1h15min to 2h49min) with a median blood loss of 555
(range 200-1000) mL. Tranexamic acid was used intra-operatively in 11 patients and was
administered at a median of 20 min before the completion of the operation (range 8 min post-
operatively to 87 min prior to completion of operation).
Feasibility of platelet testing
Each patient had 24 Multiplate® assays performed in total. Of the 360 tests, 12 (3.3%) were
re-run due to poor intra-assay variability (difference from mean values >15%, as calculated
by Multiplate® software) and satisfactory values were obtained in all on the second
10
measurement with a median variability of 7 AUC (range 5-28). Median time to commencing
assay analysis from sampling was 5 min (range 1-31min), the longest times being as a result
of two patients’ operations occurring simultaneously (all other patients’ analyses were
completed within 13min of sampling).
Platelet Responsiveness
The results of platelet aggregation and blood counts are shown in tables 2 and 3. There was a
statistically significant change in platelet responsiveness to ADP over time (p=0.012,
repeated measures ANOVA) (figure 1). There was a trend towards increased responsiveness
to ADP at the two final time points: cementing of the femoral head and immediately after
skin closure, when compared with the preoperative baseline. Platelet aggregation with the
other agonists, TRAP, collagen and arachidonic acid, followed a similar pattern (figure 2 a-
d).
The platelet count and haemoglobin fell over the course of the operation and white cell count
increased (see Table 3). Median plasma fibrinogen pre-operatively was 3.81 (Range 3.08 –
5.52) g/L.
There was a statistically significant inverse correlation between platelet responsiveness to
ADP at the pre-operative baseline and total blood loss during the operation (r=-0.624 p=0.04,
figure 3).
11
DiscussionThe results of this study demonstrate a statistically significant change in platelet aggregation
during elective primary cemented hip arthroplasty. Although statistical analysis was only
performed on one pathway of platelet function (ADP) – as a result of small sample size and
concerns over multiple testing – platelet aggregation by all four agonists followed a similar
pattern, showing alterations in platelet responsiveness across multiple pathways at the same
time points trending towards increased platelet responsiveness towards the end of surgery.
These findings are at variance with those reported in patients suffering from acute traumatic
coagulopathy (9,12), but this difference may be accounted for by the magnitude and type of
the insult. The maximal blood loss in the present study was only 1000ml, and given the
nature of the surgery, this deficit is unlikely to have been associated with hypoperfusion,
which is recognised as a key driver of haemorrhage-related coagulopathy. The changes in
platelet responsiveness may be in keeping with a hypercoagulable state, representing an
initial and effective adaptation to trauma, which has previously been demonstrated in less
severely injured(2) and postoperative patients (13).
The small number of patients included in this pilot precludes a statistical analysis of the
temporal changes in aggregability. The initial apparent decrease may relate to the
administration of anaesthesia, instrumentation, and perhaps a neuroendocrine response. All
patients received spinal anaesthesia, had venous and arterial cannulae inserted, and received
sedative medication in preparation for the operative period; with the exception of one patient
who required conversion to GA following an ineffective spinal. The administration of spinal
anaesthesia is known to cause haemodynamic effects which may influence platelet function
(14). The effect of sedative anaesthetic agents on platelet function is unclear. Anaesthetic
doses of propofol have been reported to have either no effect (15) or to decrease platelet
12
aggregation (16), but at considerably higher doses than those administered in the present
study.
The trend in platelet aggregation response in the later stages of the operations, towards
increased aggregability, could be related to increasing systemic inflammation, reflected in an
apparent increase in white cell count over the course of the operation, perhaps exacerbated by
the cementing of the femoral components. Microcirculatory changes in response to cementing
are well recognised, but previous work showed no significant difference in activation of the
coagulation cascade between cemented and uncemented hemi-arthroplasty (17). More
recently, platelet activation in response to reaming/cementing of intramedullary nails was
found in animal studies (18).
Pre-operative plasma fibrinogen levels in patients in the present study were noted to be at the
upper end of normal range, perhaps representing the underlying inflammatory osteoarthritic
process (19), although the significance of this is uncertain. The widespread effects of
inflammatory conditions on Mean Platelet Volume (MPV) and platelet activation have been
recently reported (20). In long term conditions (e.g. MI and stroke), thrombopoiesis
determines long term changes of MPV, yet the activation of the sympathetic system and
release of platelets from the spleen may underlie rapid shifts in MPV values in response to
stress(20). This rapid increase of MPV due to the release of large platelets from the spleen is
more likely in the presence of an underlying prothrombotic condition (21) and this may have
been apparent in our patient population.
The effect of platelet count is said to be minimal within the normal range but a few
investigators have found a positive correlation with impedance aggregometry (22). Thus a
fall in platelet count during surgery would if anything be expected to influence a downward
trend in aggregation results, whereas we found the opposite.
13
Interestingly, our results indicated a statistically significant inverse correlation between
platelet responsiveness to ADP at the pre-operative baseline and total blood loss during the
operation (Fig 3). There was no significant correlation between blood loss and post-operative
platelet aggregability. Some previous studies, conducted in cardiac surgery patients, have also
reported an association between pre-operative ADP-test and blood loss or requirement for
platelet concentrates (22-24). Most of the patients in the previous studies were taking aspirin
(23) or thienopyridines (22) at the time of the study, or had stopped in the few days
previously, which would influence the correlation between platelet aggregation and blood
loss. The current study is the first to show such a correlation in non-cardiac patients. The
patients in the current study were non-coagulopathic and importantly, those who were taking
aspirin had stopped taking it at least 3 days previously, and 2 for at least 7 days. The clinical
significance of this association is unclear but the finding merits further investigation.
Intraoperative platelet function testing was feasible, although requiring a dedicated member
of staff. Data were obtained for 15 out of the 17 patients who gave consent and who
underwent the planned surgery. Difficulty of arterial access or change in surgical planning
prevented data collection in two subjects. Valid results were obtained for all 15 patients for
whom data were collected, with a very small requirement for repeat testing. On average,
platelet function measurement was completed within 11 minutes of sampling. Jambor et al
(25) showed that valid results are obtained between 0 and 60 minutes after sampling, with no
significant change to aggregation over these times. For the purpose of this study, the
equipment was located in the operating theatre, with no discernible impact on the conduct of
the operation, demonstrating the potential for the implementation of the device in this
environment. Although the investigation of patients undergoing elective surgery is more
straightforward, because the injurious stimulus is similar in type and magnitude, and the
14
degree of blood loss more predictable, the use of the analyser in patients with more severe
haemorrhage, analogous to the use of a thromboelastograph, is feasible.
This study has limitations, the most obvious being the sample size. The study recruited 28.3%
of patients identified as eligible for the study. It is likely that patients’ refusal to consent to
take part was related to the prospect of additional invasive monitoring in the conduct of the
protocol, or patients reluctant to expose themselves to perceived additional risk/pain
associated with the insertion of an arterial line. However, in order to facilitate repeat testing
within a short time period, the insertion an arterial cannula was essential in the conduct of the
study. Most previous studies have presented data from venous samples, but work by Kafian et
al revealed similar results are obtained when sampling from both arterial and venous points
(26).
Despite these limitations, this study adds to the literature supporting the utilisation of platelet
function testing in the clinical environment. The use of the Multiplate® system within the
operating theatre is feasible and allows multiple rapid measures of platelet function to be
collected.
To our knowledge, this is the first study to demonstrate dynamic changes in platelet function,
over a short time period, in response to a surgical stimulus. The clinical significance of these
changes, and the potential of manipulating them for therapeutic purposes, remains to be
elucidated, although implications for the peri-operative management of patients in response
to aberrant platelet function may be substantial and should form the basis of further study, in
both elective and emergency surgery.
ACKNOWLEDGEMENTS
15
The authors are extremely grateful for the expert assistance and contributions of Dr Neil Scott
(Medical Statistician, University of Aberdeen), Win Culley (Research Nurse, Woodend
Hospital), Dr Karen Cranfield (Consultant Anaesthetist), and Ms Sharon Wood, (Research
Technician, Rowett Institute of Nutrition and Health) for fibrinogen measurement.
DECLARATIONS OF INTEREST
None
FUNDING
The study was funded by TENOVUS Scotland (G12/14). Jan Jansen is in receipt of salary
support through the NHS Research Scotland (NRS) fellowship scheme.
DISCLAIMER
The Health Services Research Unit receives funding from the Chief Scientist Office of the
Scottish Government Health and Social Care Directorates. The opinions expressed in this
article are those of the authors alone.
AUTHORS CONTRIBUTION
J.H. J.J.: Hypothesis and study design; J.H.: patient recruitment, data collection and analysis,
wrote first draft of paper; J.J., I.F., G.PA.: Data interpretation, co-writing and revision of
manuscript
16
References:
(1) Bombeli T, Spahn DR. Updates in perioperative coagulation: physiology and management of thromboembolism and haemorrhage. British Journal of Anaesthesia 2004 August 01;93(2):275-287.
(2) Brohi K, Singh J, Heron M, Coats T. Acute traumatic coagulopathy. J Trauma 2003 Jun;54(6):1127-1130.
(3) MacLeod JB, Lynn M, McKenney MG, Cohn SM, Murtha M. Early coagulopathy predicts mortality in trauma. J Trauma 2003 Jul;55(1):39-44.
(4) Brohi K, Cohen MJ, Ganter MT, Matthay MA, Mackersie RC, Pittet JF. Acute traumatic coagulopathy: initiated by hypoperfusion: modulated through the protein C pathway? Ann Surg 2007 May;245(5):812-818.
(5) Brohi K, Cohen MJ, Ganter MT, Schultz MJ, Levi M, Mackersie RC, et al. Acute coagulopathy of trauma: hypoperfusion induces systemic anticoagulation and hyperfibrinolysis. J Trauma 2008 May;64(5):1211-7; discussion 1217.
(6) Hess JR, Brohi K, Dutton RP, Hauser CJ, Holcomb JB, Kluger Y, et al. The coagulopathy of trauma: a review of mechanisms. J Trauma 2008 Oct;65(4):748-754.
(7) Woulfe D, Yang J, Brass L. ADP and platelets: the end of the beginning. J Clin Invest 2001 Jun;107(12):1503-1505.
(8) Yusuf S, Bijsterveld N, Moons A. Effects of clopidogrel in addition to aspirin in patients with acute coronary syndromes without ST-segment elevation: the Clopidogrel in Unstable Angina to Prevent recurrent Events Trial Investigators. N Engl J Med 2001;345(7):494-502.
(9) Solomon C, Traintinger S, Ziegler B, Hanke A, Rahe-Meyer N, Voelckel W, et al. Platelet function following trauma. A multiple electrode aggregometry study. Thromb Haemost 2011 Aug;106(2):322-330.
(10) Kutcher ME, Redick BJ, McCreery RC, Crane IM, Greenberg MD, Cachola LM, et al. Characterization of platelet dysfunction after trauma. J Trauma Acute Care Surg 2012 Jul;73(1):13-19.
(11) Jansen JO, Luke D, Davies E, Spencer P, Kirkman E, Midwinter MJ. Temporal changes in ROTEM(R)-measured coagulability of citrated blood samples from coagulopathic trauma patients. Injury 2013 Jan;44(1):36-39.
(12) Platelet function in trauma measured by multiple electrode aggregometry. ISTH; 2011.
17
(13) Payen JF, Baruch M, Horvilleur E, Richard M, Gariod T, Polack B. Changes in specific markers of haemostasis during reduction mammoplasty. Br J Anaesth 1998 Apr;80(4):464-466.
(14) Jackson SP, Nesbitt WS, Westein E. Dynamics of platelet thrombus formation. J Thromb Haemost 2009 Jul;7 Suppl 1:17-20.
(15) Dordoni PL, Frassanito L, Bruno MF, Proietti R, de Cristofaro R, Ciabattoni G, et al. In vivo and in vitro effects of different anaesthetics on platelet function. Br J Haematol 2004 Apr;125(1):79-82.
(16) De La Cruz JP, Paez MV, Carmona JA, De La Cuesta FS. Antiplatelet effect of the anaesthetic drug propofol: influence of red blood cells and leucocytes. Br J Pharmacol 1999 Dec;128(7):1538-1544.
(17) Bredbacka S, Andreen M, Blomback M, Wykman A. Activation of cascade systems by hip arthroplasty. No difference between fixation with and without cement. Acta Orthop Scand 1987 Jun;58(3):231-235.
(18) Blankstein M, Byrick RJ, Nakane M, Bang AK, Freedman J, Garvey MB, et al. A preliminary study of platelet activation after embolization of marrow contents. J Orthop Trauma 2012 Nov;26(11):e214-20.
(19) Sokolove J, Lepus CM. Role of inflammation in the pathogenesis of osteoarthritis: latest findings and interpretations. Ther Adv Musculoskelet Dis 2013 Apr;5(2):77-94.
(20) Gasparyan AY, Ayvazyan L, Mikhailidis DP, Kitas GD. Mean platelet volume: a link between thrombosis and inflammation? Curr Pharm Des 2011;17(1):47-58.
(21) Yilmaz MB, Saricam E, Biyikoglu SF, Guray Y, Guray U, Sasmaz H, et al. Mean platelet volume and exercise stress test. J Thromb Thrombolysis 2004 Apr;17(2):115-120.
(22) Ranucci M, Baryshnikova E, Soro G, Ballotta A, De Benedetti D, Conti D, et al. Multiple electrode whole-blood aggregometry and bleeding in cardiac surgery patients receiving thienopyridines. Ann Thorac Surg 2011 Jan;91(1):123-129.
(23) Emeklibas N, Kammerer I, Bach J, Sack FU, Hellstern P. Preoperative hemostasis and its association with bleeding and blood component transfusion requirements in cardiopulmonary bypass surgery. Transfusion 2013 Jun;53(6):1226-1234.
(24) Rahe-Meyer N, Winterhalter M, Boden A, Froemke C, Piepenbrock S, Calatzis A, et al. Platelet concentrates transfusion in cardiac surgery and platelet function assessment by multiple electrode aggregometry. Acta Anaesthesiol Scand 2009 Feb;53(2):168-175.
(25) Jambor C, Weber CF, Gerhardt K, Dietrich W, Spannagl M, Heindl B, et al. Whole blood multiple electrode aggregometry is a reliable point-of-care test of aspirin-induced platelet dysfunction. Anesth Analg 2009 Jul;109(1):25-31.
18
(26) Kafian S, Mobarrez F, Kalani M, Wallen H, Samad BA. Comparison of venous and arterial blood sampling for the assessment of platelet aggregation with whole blood impedance aggregometry. Scand J Clin Lab Invest 2011 Dec;71(8):637-640.
19
Legends
Fig 1 Study Recruitment Process.
Fig 2. Platelet aggregation in whole blood by MEA (multi-electrode aggregometry) using Multiplate ® analyser, with four agonists. n=15 patients at 6 time points before and during hip replacement operation: Sample 1. Pre-operatively before anaesthetic; 2. On commencement of the skin incision; 3. At removal of the femoral head; 4. Reaming of the femoral canal; 5. Cementing of the femoral component of the prosthesis; and 6. Immediately following skin closure. Results presented as AUC (area under the aggregation curve), means with standard deviation.Panel
(a) ADP-test (Adenosine diphosphate 6.5M), ANOVA p=0.012(b) ASPI-test (0.5mM arachidonic acid)(c) TRAP-test (32M thrombin receptor activating peptide)(d) Coll-test (3.2g/mL collagen)
Fig 3: Correlation of ADP-stimulated platelet aggregation (Multiplate ADP-test) at pre-operative time point with total blood loss. n= 12 patients for whom blood loss data was available. Spearman’s Rank correlation coefficient r=-0.624, p=0.04
1
FIGURE 1: Study recruitment process
2 Patients
1 No arterial access, 1 change of surgical plan
15 Patients
Data collected
14 Patients
3 Unavailable, 11 surgery dates unsuitable for testing
17 Patients
Formally consented
22 Patients
Declined Study involvement
51 Patients
Identified
31 Patients
Initial consent given
15 Patients
Final Study Group
1
Legends
Fig 1 Study Recruitment Process.
Fig 2. Platelet aggregation in whole blood by MEA (multi-electrode aggregometry) using Multiplate ® analyser, with four agonists. n=15 patients at 6 time points before and during hip replacement operation: Sample 1. Pre-operatively before anaesthetic; 2. On commencement of the skin incision; 3. At removal of the femoral head; 4. Reaming of the femoral canal; 5. Cementing of the femoral component of the prosthesis; and 6. Immediately following skin closure. Results presented as AUC (area under the aggregation curve), means with standard deviation.Panel
(e) ADP-test (Adenosine diphosphate 6.5M), ANOVA p=0.012
(f) ASPI-test (0.5mM arachidonic acid)(g) TRAP-test (32M thrombin receptor activating peptide)(h) Coll-test (3.2g/mL collagen)
Fig 3: Correlation of ADP-stimulated platelet aggregation (Multiplate ADP-test) at pre-operative time point with total blood loss. n= 12 patients for whom blood loss data was available. Spearman’s Rank correlation coefficient r=-0.624, p=0.04
4
TABLE 1: Baseline characteristics of study population
Age, median (range) 69 (56-78)
Gender, male: female, n 9:6
ASA grade, n
ASA 1 1
ASA 2 12
ASA 3 2
Antiplatelet drug use, n 4
Pre-operative vital signs, median (range)
Systolic blood pressure (mmHg) 150 (109-199)
Heart rate (bpm) 82 (62-97)
Temperature (°C) 37.2 (36.7-37.6)
O2 saturation 97 (92-100)
Type of anaesthetic, n
Spinal 14
Spinal + general 1
Tranexamic acid use, n 11
Laterality, left: right, n 6:9
Blood loss, ml, median (range) 555 (200-1000)ASA – American Society of Anaethesiologists grade
5
TABLE 2: Platelet aggregation, as area under curve (AUC) mean and standard deviation, by
time point
Time Point Agonist
ADP TRAP COL ASPI
Pre-op 80 (17.06) 152 (23.48) 73 (16.29) 82 (26.37)
Knife to skin 76 (21.62) 136 (26.23) 69 (18.64) 72 (33.44)
Femoral Head Removal 78 (24.76) 143 (23.71) 72 (17.05) 73 (34.74)
Femoral Reaming 79 (21.20) 141 (25.13) 75 (20.80) 72 (36.16)
Femoral Cementing 80 (25.22) 152 (48.60) 79 (22.07) 75 (41.72)
Post-op 90 (24.02) 179 (36.18) 91 (29.01) 87 (42.33)
[Mean (SD)]
ADP – Adenosine Diphosphate; TRAP – Thrombin Receptor Activating Peptide; COL – Collagen; ASPI – Arachidonic acid
6
TABLE 3: Haematological parameters, mean and standard deviation, by time point
Time Point Hb (g/l) Plts (x109/l) WCC(x109/l)
Pre-op 139.7 (10.54) 283 (71.6) 6.3 (1.23)
Commencement 131.7 (10.77) 264 (67.5) 4.9 (1.28)
Femoral Head Removal 129.3 (10.43) 264 (59.1) 4.8 (1.11)
Femoral Reaming 126.1 (11.41) 260 (60.0) 5.0 (1.71)
Femoral Cementing 123.6 (12.88) 255 (63.3) 5.7 (2.23)
Post-op 121.3 (13.52) 255 (51.7) 7.5 (2.60)
Mean (SD)
Hb – Haemoglobin; Plts –Platelet count; WCC – White Cell Count