As erythrocyte and estrogens interact so closely and erythrocytes can indicate the healthiness of an individual, it is essential to investigate the effects of natural estrogens as well as synthetic estrogens on these cells. Whole blood samples were used for thromboelastography (TEG), light microscopy (LM), and scanning electron microscopy (SEM) investigation. Viscoelastic investigation with TEG revealed that estrogens affected the rate of clot formation without any significant effect on the strength or stability of the clot. Axial ratio analysis with LM showed a statistically significant increase in number of erythrocytes with decreased roundness. Morphological analysis with SEM confirmed the change in erythrocyte shape and revealed both ultrastructural membrane changes and erythrocyte interactions. As erythrocyte shape and membrane flexibility correlates to physiological functioning of these cells in circulation, these changes, indicative of possible eryptosis brought on by estrogens, when experienced by individuals with an underlying inflammatory or hematological illness, could impair erythrocyte functioning and even result in obstructions in circulation. In conclusion, we suggest that whole blood analysis with viscoelastic and morphological techniques could be used as assessment of the hematological healthiness of individuals using estrogens.

Recent evidence suggests that Ca supplements increase the risk of cardiovascular events, but the mechanism(s) by which this occurs is uncertain. In a study primarily assessing the effects of various Ca supplements on blood Ca levels, we also investigated the effects of Ca supplements on blood pressure and their acute effects on blood coagulation. We randomised 100 post-menopausal women to 1 g/d of Ca or a placebo containing no Ca. Blood pressure was measured at baseline and every 2 h up to 8 h after their first dose and after 3 months of supplementation. Blood coagulation was measured by thromboelastography (TEG) in a subgroup of participants (n 40) up to 8 h only. Blood pressure declined over 8 h in both the groups, consistent with its normal diurnal rhythm. The reduction in systolic blood pressure was smaller in the Ca group compared with the control group by >5 mmHg between 2 and 6 h (P≤0·02), and the reduction in diastolic blood pressure was smaller at 2 h (between-groups difference 4·5 mmHg, P=0·004). Blood coagulability, assessed by TEG, increased from baseline over 8 h in the calcium citrate and control groups. At 4 h, the increase in the coagulation index was greater in the calcium citrate group compared with the control group (P=0·03), which appeared to be due to a greater reduction in the time to clot initiation. These data suggest that Ca supplements may acutely influence blood pressure and blood coagulation. Further investigation of this possibility is required.

Summary

Background and objective: The reasons for coagulopathy may be multiple and the identification of the underlying cause is often difficult. Recently, we identified two patients showing characteristics of heparin overdose during surgery. We hypothesised that filling a Shaldon dialysis catheter with heparin prior to closure, so-called heparin lock, might have triggered this coagulation disorder. Therefore, the aim of this in vitro study was to show whether this procedure can lead to an iatrogenic administration of heparin. Methods: A Shaldon catheter (GamCath®; Joka Kathetertechnik, Hechingen, Germany) was hung up in a container filled with NaCl solution 0.9% 5 mL and a heparin lock was simulated. Instead of using heparin solution we injected 1 mL of a KCl solution (1 mol L−1) into the Shaldon catheter, because the measurement of the potassium concentration is faster and more reliable than that of heparin. Ten measurements were taken after fast (0.5 s) and slow (3 s) injection speeds. Results: Although the catheter volume is specified as 1.07 mL, an amount up to 0.51 mL KCl solution on average was detectable in the solution after locking the catheter with 1 mL KCl solution. Conclusions: Following a heparin lock a considerable amount of the injected solution is accidentally administered to the patient. Only 49.1% of the injected volume may remain in the Shaldon catheter. This could lead to an increased risk of coagulopathy.

Summary

Background and objective: Different types of polymer surfaces affect the activation of platelets and coagulation pathway containers depending on their surface qualities. Importantly, this could produce variability of coagulation results obtained with thrombelastographical analysis. We assessed the effects of blood storage on thrombelastograph, TEG®, variables using polypropylene and polycarbonate containers. Methods: An in vitro experiment was performed, with eight volunteers in each limb. Fresh whole blood was stored in polypropylene or polycarbonate tubes prior to TEG® analysis, to assess the role of these plastics in the TEG® results obtained. Results: The polycarbonate tubes displayed slower onset of coagulation and greater variability of data for all four basic TEG variables (r-time, k-time, α-angle and maximum amplitude, P < 0.05). Polycarbonate results fell outside manufacturer reference ranges. Conclusions: It is likely that this is due to the altered surface properties and charge effects of the containers affecting proteins and platelets differently. Caution should be used in choosing which containers are used for storage of fresh blood prior to coagulation assessment, as variable results will follow where different types of plastic containers are employed.

Summary

Background and objective: Arterial catheters are routinely used to sample blood for clotting studies in most cardiothoracic intensive care units. The clotting profile in surgical bleeding after cardiac surgery influences further management. Aspiration and discard of a certain amount of blood from the line, prior to sampling, are assumed to clear heparin contamination. We have investigated this assumption through analysis of the clotting profile by simultaneous arterial line and peripheral venous samples.

Methods: The morning following cardiac surgery, simultaneous arterial line and peripheral venous blood samples were taken for activated plasma thromboplastin time (APTT) ratio and international normalized ratio (INR) in 49 randomly selected patients. Also, a thromboelastogram analysis (TEG) (n = 7) was made. A survey of 22 UK cardiothoracic intensive care units was carried out to determine the practice for the withdrawal of blood for clotting studies.

Results: The median arterial APTT ratio value was 1.32 ± 0.52 as compared to the median peripheral APTT ratio value which was 1.1 ± 0.24 (P < 0.001). INR values were statistically similar by both routes. Heparin contamination was confirmed by TEG which revealed that the R-value for arterial catheter blood samples without heparinase in the cup was higher (406.00 ± 64.44 s) compared with the value for arterial samples with heparinase in the cup (318.28 ± 47.26 s, P < 0.05). The survey of 22 UK cardiothoracic intensive care units showed that heparinized arterial lines were by far the commonest ports used for blood withdrawal for the measurement of APTT ratio results.

Conclusions: Samples withdrawn from heparinized arterial lines cannot be relied upon for APTT ratio results.

Amide local anaesthetics inhibit platelet function. We hypothesized that residual anaesthetic in the epidural space could decrease efficacy of an epidural blood patch in preventing postdural puncture headache. Levobupivacaine has recently been approved for epidural anaesthesia. Its effects on coagulation have not previously been studied. The aim of this study was to determine the effects of levobupivacaine on clotting using thromboelastography. Ten ASA Class I volunteers were studied. Venous blood samples were analysed using a Haemoscope 2000D TEG analyser. Whole blood, a 50% saline control and two levobupivacaine solutions (2.5 mg mL−1 and 2.5 μg mL−1 in blood) were compared. The former reproduces that produced in the epidural space by blood (20 mL for an epidural blood patch) and levobupivacaine 0.5% (20 mL). The latter approximates plasma concentrations following epidural injection of levobupivacaine 0.5% (20 mL). P < 0.05 was considered significant. Maximum amplitude (MA), a measure of clot strength, is decreased by levobupivacaine 2.5 mg mL−1. Levobupivacaine 2.5 mg mL−1 decreases clot strength and may reduce efficacy of a prophylactic epidural blood patch.

A retrospective survey was undertaken of 142 adults who had undergone cardiac surgery with cardiopulmonary bypass. According to the manufacturer's instructions for thromboelastography, patients were identified as showing evidence of fibrinolysis if after coming off bypass the Ly30 index was ≥7.5%. In the 20 fibrinolytic patients, fibrinolysis was readily corrected by tranexamic acid but these patients needed more colloid and more vasopressor support than the non-fibrinolytic patients. There were three deaths, all in the fibrinolytic patients. It is possible that fibrinolysis is a marker for onset of systemic inflammation syndrome. It is recommended that, until the association between fibrinolysis and worse outcome is investigated further, patients showing fibrinolysis early after cardiopulmonary bypass should not be discharged too soon from intensive care.

The interaction of aprotinin with normal coagulation was studied in blood samples obtained from 10 healthy subjects. Each sample was simultaneously tested in four different preparations : NaCl-treated blood: 0.03 mL 0.9% NaCl in 0.33 mL blood; aprotinin treated blood : 0.33 mL blood+aprotinin in 0.03 mL in aliquots to obtain a final blood concentration of respectively 50 KIU mL−1; 100 KIU mL−1 and 200 KIU mL−1. The coagulation process was analysed by thromboelastography. R-time, reflecting intrinsic coagulation, increased in a dose dependent manner between NaCl-treated and aprotinin-treated blood. These findings suggest a dose dependent impairment of intrinsic coagulation by aprotinin.

Forty-eight patients scheduled for elective cardiac surgery were randomly assigned to receive aprotinin in the following doses: 0.2 mg kg−1 (group A), 0.7 mg kg−1 (group B), 1 mg kg−1 (group C) and 1.4 mg kg−1 (group D). Clot formation was analysed by thromboelastography immediately after induction of anaesthesia and again 30 min after administration of aprotinin. Rate of clot formation was assessed using R (reaction time = rate of initial fibrin formation), K (clot formation time = rate of fibrin build-up and cross linking) and angle of clot formation (denoting speed at which solid clot forms). Strength of the clot was assessed by maximal amplitude of clot formation (MA)and % lysis after 30 and 60 min. Significant reduction of R and K times and increase in angle of clot formation was observed in groups A and B. This effect was not apparent in the other groups. In group D, an increase in R time was noted. These findings indicate a dose dependent effect of aprotinin on rate of clot formation with an earlier clot formation at low doses.