Evaluation of the diagnostic possibility of hemorrhagic risk in pregnant women with severe preeclampsia by rotational thromboelastography

Full Text

BACKGROUND

A progression in pregnancy is associated with changes in all stages of hemostasis, which aim to prepare a woman for childbirth. The risks of venous thrombotic complications (VTC) in pregnant women are about five times higher than in non-pregnant women [1]. The probability of VTCs is 1.9 cases per 1,000 pregnancies. Notably, women in the first 6 weeks of the postpartum period are more likely to develop VTCs than pregnant women [2].

Pregnancy is associated with physiological changes in the blood coagulation system, which correlate with placentation. These changes in pregnant women lead to an approximately two-fold increase in the coagulation activity of the blood system compared with that in non-pregnant women; this state in pregnant women is called physiological hypercoagulation [3]. In conjunction with other risk factors, VTC is associated with a high risk of miscarriage itself and the development of thrombosis in the mother during the postpartum period. In contrast, although pregnancy is a state of hypercoagulation, pregnant women are at a high risk of massive bleeding, primarily because of premature detachment and previa or ingrowth of the placenta, as well as preeclampsia [4, 5]. Currently, standard clotting assessments are most often used to assess the hemostasis system; these include measurement of activated partial thromboplastin time, prothrombin time, thrombin time, fibrinogen level, and platelet count. These tests were not initially intended to monitor coagulopathies but were developed to detect the deficiency of certain coagulation factors or to monitor the efficiency of anticoagulant therapy [4, 5]. They do not help assess the function of natural anticoagulants, the fibrinolysis system, and the functional activity of platelets. The true potential of the hemostasis system can be determined only by testing all the primary mechanisms of blood coagulation in aggregate. As a result, recently, tests for determining the viscoelastic properties of the forming clot are being increasingly requested [6]. Tests such as rotational thromboelastometry (ROTEM) allow quick assessment of the hemostatic system and help initiate appropriate therapy [7, 8]. ROTEM has shown high efficacy in the treatment of massive blood loss and is included in most clinical guidelines for the care of patients with obstetric bleeding [9, 10].

The study aimed to determine the standard ROTEM parameters in pregnant women with severe preeclampsia.

MATERIALS AND METHODS

We enrolled 30 pregnant women with severe preeclampsia who were being monitored in the intensive care unit of the obstetric department of the D.O. Ott Research Institute of Obstetrics, Gynecology, and Reproductology. The control group comprised 10 patients with physiologically proceeding pregnancy, with delivery scheduled via caesarean section for reasons not related to obstetric complications.

All pregnant women underwent a full clinical and laboratory examination in compliance with the Ministry of Health No. 572n.

The viscoelastic properties of the forming clot were assessed using a ROTEM® Delta device (Germany) using reagent kits (Pentapharm GmbH). Blood samples were obtained before surgery via peripheral vein puncture of the cubital vein and were collected into standard 3.5-ml Vacutainer tubes containing 3.2% sodium citrate. ROTEM analysis was performed within 2 h after receiving the samples. The primary screening tests were performed, and the parameters of whole blood coagulation were assessed during the initiation of thrombogenesis by factors of the extrinsic pathway (recombinant tissue factor), EXTEM test, and intrinsic pathway (contact activation with ellagic acid), INTEM test. Parameters assessed using ROTEM were the following (Figure 1): time of clot formation onset, time of clot formation, clotting dynamics, maximum clot firmness, and A10 and A20 (amplitude of the formed clot after 10 and 20 min, respectively).

 

Figure. ROTEM standard parameters. CT — time of clot formation onset; CFT — clot formation time; alpha angle — coagulation dynamics; MCF — maximum clot firmness; A10 and A20 — amplitude of the formed clot after 10 and 20 min; ML — maximum lysis

 

The plasma component of the hemostasis system was assessed using an automatic coagulometer ACL Elite pro by determining the activated partial thromboplastin time, prothrombin index, prothrombin time, international normalized ratio, and fibrinogen level.

The obtained data were statistically analyzed using Microsoft Excel 2007 and Statistica 10.0 software. The mean and standard deviation were calculated. Correlation analysis was performed using Spearman’s correlation coefficient. Student’s t-test was used to test the statistical significance of differences in mean values.

RESULTS

The age of pregnant women with severe preeclampsia ranged from 19 to 43 years (mean age: 32.8 ± 6.06 years). Examination of the obstetric history of patients revealed early reproductive losses, induced abortions, and a complicated course of previous pregnancies. Two thirds of the women were primiparous. One third of pregnancies occurred with the use of in vitro fertilization. A burdened somatic history was registered in 80% of pregnant women with severe preeclampsia. In addition, 70% of pregnant women had carbohydrate metabolism disorders, which were combined with chronic arterial hypertension in 40% women and chronic pyelonephritis in 9.5% women. Pure preeclampsia was registered in 20% pregnant women.

The main clinical manifestations of severe preeclampsia were arterial hypertension (systolic blood pressure: 158 ± 13.7 mmHg, diastolic blood pressure: 97 ± 6.8 mmHg), proteinuria (1.64 ± 1.9 g/l), and swelling in 90% subjects as well as grade III swelling and negative diuresis in 26% subjects. Neurological symptoms in the form of headaches, less often nausea and vomiting, were noted in 56.7% subjects. Blood testing revealed thrombocytopenia in 30% of subjects. Biochemical analysis revealed a significantly increased activity of lactate dehydrogenase (35%) and hypoproteinemia (77%).

In most patients who were examined, coagulogram indices indicated hypercoagulation. All patients received magnesia therapy at the initial stage according to the current recommendations. Antihypertensive therapy with clonidine was prescribed to 40% of pregnant women, and the remaining 60% received methyldopa in combination with calcium channel blockers. All pregnant women with severe preeclampsia underwent delivery by caesarean section. The delivery term was 26 to 41 weeks (35.8 ± 3.3). The average volume of intraoperative blood loss was 670 ± 108 ml, the average weight of all newborns was 3017.5 ± 867 g, and the Apgar score was 7.2 ± 1 points. Two patients developed a complication of HELLP syndrome. All puerperas were discharged in a satisfactory condition on day 8.2 ± 2.

The comparison group comprised 10 pregnant women who had delivery by caesarean section in a scheduled manner. Their average age was 28.8 ± 3.4 years, and their average delivery term was 38.8 ± 1.8 weeks. The control subjects had an uneventful thrombohemorrhagic history. The indications for scheduled abdominal delivery were a scar on the uterus after a caesarean section (30%), a coxalgic pelvis (10%), a contracted pelvis (30%), vasa previa (10%), and a neurologist’s opinion (20%).

Table 1 shows the average values of coagulogram indices as well as results of clinical blood test in pregnant women with severe preeclampsia and with physiological course of pregnancy. Hypercoagulation were noted both in women with severe preeclampsia (60%) and those with a physiological course of pregnancy (40%). Patients with severe preeclampsia tended to have higher fibrinogen and prothrombin index indices as well as lower activated partial thromboplastin time, but the differences were insignificant.

 

Table 1. Mean and statistical deviation values of coagulogram indices and clinical blood test results of pregnant women with severe preeclampsia and those with physiological course of pregnancy

Indicator	Pregnant women with severe preeclampsia, n = 30	Women with physiological course of pregnancy, n = 10
Clinical blood test values
Leukocytes, ×109/l	9.9 ± 2.9	8.5 ± 2.3
Erythrocytes, ×1012/l	4.07 ± 0.46	3.88 ± 0.3
Hemoglobin, g/l	119.7 ± 11.33	129.5 ± 9.73
Platelets, ×109/l	197.53 ± 60.51	229.6 ± 44.85
Coagulogram
Prothrombin time, s	10.35 ± 0.77	10.55 ± 0.94
Prothrombin index, %	138.90 ± 28.28	129.95 ± 24.25
International normalized ratio	0.92 ± 0.07	0.93 ± 0.08
Fibrinogen, g/l	5.30 ± 0.80	4.29 ± 0.63
Activated partial thromboplastin time (ind.), s	0.89 ± 0.09	0.93 ± 0.07
Thrombin time, s	14.81 ± 1.14	15.93 ± 0.89

 

When interpreting the ROTEM results, reference intervals for pregnant women in III trimester, reported by a study of international colleagues, were used [11]. Table 2 presents the mean and statistical deviation values of the ROTEM test scores. Analysis of 9 (30%) thromboelastograms (TEGs) of pregnant women with severe preeclampsia revealed hypocoagulation, with 3 TEGs each revealing hypocoagulation along the intrinsic coagulation pathway, extrinsic coagulation pathway, and both pathways. Prolonged clotting time and clot formation time indicated decreased dynamics of stable clot formation through activated platelets and fibrin, which most likely could be caused by impaired platelet function, low platelet count, or abnormal fibrin polymerization. In subjects with hypocoagulation along both the intrinsic and extrinsic pathways, there was a tendency to insufficient amplitude and, therefore, the firmness of the forming clot 10 min after the start of the study, which returned to normal level only by the 20^th min of induced coagulation.

 

Table 2. Indicators of clinical and laboratory examination of patients with hypocoagulation

Indicators	Pregnant women with hypocoagulation before surgery, n = 9
Clinical blood test values
Leukocytes, ×109/l	9.06 ± 2.42
Erythrocytes, ×1012/l	4.14 ± 0.3
Hemoglobin, g/l	119.11 ± 10.23
Platelets, ×109/l	188.11 ± 52.24
Coagulogram
Prothrombin time, s	10.11 ± 0.63
Prothrombin index, %	146.78 ± 31.6
International normalized ratio	0.91 ± 0.06
Fibrinogen, g/l	5.16 ± 0.73
Activated partial thromboplastin time (ind.), s	0.86 ± 0.12
Thrombin time, s	14.47 ± 0.83
	EXTEM	INTEM
CT, s	73.8 ± 22.5	247.4 ± 112.3
CFT, s	119.1 ± 53.3	138.3 ± 81.8
Alpha angle, deg.	69.3 ± 8.9	66.7 ± 11.4
A10, mm	53.9 ± 9.5	54.8 ± 10.7
A20, mm	62.7 ± 7.38	64.9 ± 6.4
MCF, mm	66.2 ± 6.1	68.4 ± 6.3

Note. CT — time of clot formation onset; CFT — clot formation time; alpha angle — coagulation dynamics; A10 and A20 — amplitude of the formed clot after 10 and 20 min, respectively; MCF — maximum clot firmness; EXTEM — thrombus formation via extrinsic coagulation pathway factors; INTEM — thrombus formation via intrinsic coagulation pathway factors.

 

In pregnant women with hypocoagulation, delivery occurred from 28 to 38 (35.8 ± 3.07) weeks. Increased intraoperative bleeding was noted in three patients, for which tranexamic acid was intravenously administered. In general, surgeries were technically uneventful. The average blood loss was 660 ± 100 ml. One postpartum woman developed HELLP syndrome on postoperative day 1; the postpartum period was uneventful in rest of the patients. Table 2 presents the indicators of clinical and laboratory examination before surgery.

Two patients with severe preeclampsia developed HEELP syndrome: one developed the syndrome before delivery and another after delivery. Table 3 shows the results of a clinical and laboratory study of these two women. According to TEG performed before surgery, in one pregnant woman with postpartum HELLP syndrome, both EXTEM and INTEM tests revealed signs of hypocoagulation, characterized by increased time of clot formation, insufficiency of clot formation at 10 and 20 mins and reduced maximum clot firmness. Subsequently, this patient underwent fresh frozen plasma transfusion intraoperatively. In the postpartum period, TEG revealed persistent hypocoagulation, with aggravated anemia and thrombocytopenia; therefore, repeated transfusion of both fresh frozen plasma and erythrocyte and platelet suspensions was performed.

 

Table 3. Results of clinical and laboratory studies of pregnant women with early and late HELLP syndrome before delivery and in the postoperative period

Indicators	Before delivery				After delivery
	HELLP syndrome, n = 1		Severe preeclampsia, n = 28		HELLP syndrome, n = 1		Severe preeclampsia, n = 28
Clinical blood test values
Leukocytes, ×109/l	19.6		6.5		12.2		13.8
Erythrocytes, ×1012/l	4.03		4.47		3.23		3.47
Hemoglobin, g/l	115		144		93		117
Platelets, ×109/l	79		121		47		70
Biochemical blood test values
Alanine aminotransferase, U/L	153		9.8		179		13
Aspartate aminotransferase, U/L	161		28.4		250		74
Lactate dehydrogenase, U/L	1063		1280		823.1		2052.4
Total protein, g/l	68		54.47		66.3		53.7
Coagulogram indices
Prothrombin time, s	9		8.9		9.7		9.5
Prothrombin index, %	205		213		156.8		157
International normalized ratio	0.8		0.79		0.86		0.87
Fibrinogen, g/l	5.6		5.89		3.97		2.97
Activated partial thromboplastin time (ind.), s	1.1		1.04		0.88		0.92
Thrombin time, s	15		14.4		17.8		21.7
ROTEM indices
	EXTEM	INTEM	EXTEM	INTEM	EXTEM	INTEM	EXTEM	INTEM
CT, s	57	140	56	198	62	164	47	178
CFT, s	105	94	172	181	108	102	196	202
Alpha angle, deg.	75	73	74	68	70	72	76	70
A10, mm	51	51	41	40	44	46	36	37
A20, mm	59	58	50	57	50	55	44	46
MCF, mm	62	62	56	56	60	59	50	51
Urinary test values
Protein	5.3		0.08		2.88		2.14

Note. CT — time of clot formation onset; alpha angle — coagulation dynamics; MCF — maximum clot firmness; A10 and A20 — amplitude of the formed clot after 10 and 20 mins, respectively; CFT — clot formation time; EXTEM — thrombus formation via extrinsic coagulation pathway factors; INTEM — thrombus formation via intrinsic coagulation pathway factors.

 

A pregnant woman with HELLP syndrome, which developed even before delivery, despite significant changes in laboratory parameters, had no hypocoagulation disorders according to TEG data. As a result, the patient underwent intraoperative transfusion of fresh frozen plasma. In the postoperative period, TEG analysis showed insufficient firmness of the forming clot after 10 and 20 mins at normal maximum clot firmness. On day 2 of the postoperative period, owing to an increase in signs of multiple organ failure, the puerpera was transferred to a multidisciplinary hospital.

Comparative analysis of ROTEM indicators between pregnant women with severe preeclampsia and pregnant women with physiological pregnancy course (Table 4) did not reveal statistically significant differences.

 

Table 4. Mean and statistical deviation values of ROTEM test scores in pregnant women with severe preeclampsia and those with physiological pregnancy course

ROTEM indicators	EXTEM		INTEM
	Severe preeclampsia, n = 30	Physiological pregnancy, n = 10	Severe preeclampsia, n = 30	Physiological pregnancy, n = 10
CT, s	61.37 ± 15.13	57.6 ± 7.46	196.53 ± 71.55	164.50 ± 13.53
CFT, s	84.60 ± 38.22	76.8 ± 11.89	89 ± 55.85	67.80 ± 3.23
Alpha angle, deg.	74.47 ± 6.19	73.7 ± 2.79	73.37 ± 7.92	67.80 ± 12.93
A10, mm	60.03 ± 7.82	67.2 ± 2.99	59.90 ± 8	73.70 ± 5.29
A20, mm	66.87 ± 6.12	61.9 ± 3.54	67.50 ± 5.53	60.50 ± 4.43
MCF, mm	69.47 ± 5.16	69.4 ± 2.37	70.33 ± 5.12	71 ± 3.06

Note. CT — time of clot formation onset; CFT — clot formation time; alpha angle — coagulation dynamics; MCF — maximum clot firmness; A10 and A20 — amplitude of the formed clot after 10 and 20 mins, respectively; EXTEM — thrombus formation via extrinsic coagulation pathway factors; INTEM — thrombus formation via intrinsic coagulation pathway factors.

 

The correlation analysis of the ROTEM indices and coagulation system indices revealed an average direct correlation between platelet count and the amplitude of forming clot after 10 min (0.46; 0.41), 20 min (0.41; 0.43); and the maximum clot firmness (0.45; 0.39) in tests of thrombogenesis initiation by factors of the extrinsic (EXTEM) and intrinsic (INTEM) pathways, as well as the mean inverse correlation (−0.52) between the count of platelets and the time of clot formation in the EXTEM test.

Considering these data, it can be concluded that rotational thromboelastography with the main screening tests EXTEM and INTEM did not have a significant diagnostic value in assessing the risk of hemorrhagic complications in pregnant women with severe preeclampsia.

ADDITIONAL INFORMATION

Conflict of interest. The authors declare no conflict of interest.

Author contributions. E.V. Mozgovaya and I.S. Peretyatko conceptualized and designed the study; I.S. Peretyatko collected and processed the material, performed statistical data processing, and wrote the text; E.V. Mozgovaya edited the text.

About the authors

Ilya S. Peretyatko

The Research Institute of Obstetrics, Gynecology, and Reproductology named after D.O. Ott

Author for correspondence.
Email: doc.pere@yandex.ru

MD

Russian Federation, 3 Mendeleevskaya line, Saint Petersburg, 199034

Elena V. Mozgovaya

The Research Institute of Obstetrics, Gynecology, and Reproductology named after D.O. Ott; Saint Petersburg State University

Email: elmozg@mail.ru
ORCID iD: 0000-0002-6460-6816
SPIN-code: 5622-5674

MD, PhD, DSci (Medicine)

Russian Federation, 3 Mendeleevskaya line, Saint Petersburg, 199034; Saint Petersburg

References

Supplementary files