Evaluation of the relationship between the STOP-Bang score with oxygen reserve index and difficult airway: a prospective observational study

BACKGROUND

Patients diagnosed with Obstructive Sleep Apnea (OSA) syndrome have a tendency towards hypoventilation, hypoxia, and hypercarbia in the perioperative period. This study hypothesized that the Oxygen Reserve Index (ORi) could predict possible hypoxia and determine difficult airways in patients at risk for OSA, as determined by the STOP-Bang questionnaire.

METHODS

This prospective study included adult patients undergoing elective surgery under general anesthesia with endotracheal intubation, divided into two groups: low risk (0-2 points) and high risk (3-8 points) based on their STOP-Bang questionnaire results. The primary outcome measure was the highest ORi value reached during preoxygenation and the time to reach this value. Data were recorded at four time points: before preoxygenation (T1), end of preoxygenation (T2), end of mask ventilation (T3), and end of intubation (T4), as well as partial oxygen pressure values in T1, T2, and T4. The secondary outcome measures were the grading scale for mask ventilation, Cormack-Lehane score, tonsil dimensions, use of a stylet, and application of the burp maneuver during intubation.

RESULTS

In the high-risk group, preoperative peripheral oxygen saturation values, the highest ORi value reached in preoxygenation, and ORi values at T3 and T4 times were lower, and the time to reach the highest ORi value was longer (p < 0.05).

CONCLUSION

Using ORi in patients with OSA may be useful in evaluating oxygenation, and since difficult airway is more common, ORi monitoring will better manage possible hypoxic conditions.

The Impact of CoronaVac Vaccination on 28-day Mortality Rate of Critically Ill Patients with COVID-19 in Türkiye

Background

Vaccines against coronavirus disease-19 (COVID-19) have been effective in preventing symptomatic diseases, hospitalizations, and intensive care unit (ICU) admissions. However, data regarding the effectiveness of COVID-19 vaccines in reducing mortality among critically ill patients with COVID-19 remains unclear.

Aims

To determine the vaccination status and investigate the impact of the COVID-19 vaccine on the 28-day mortality in critically ill patients with COVID-19.

Study Design

Multicenter prospective observational clinical study.

Methods

This study was conducted in 60 hospitals with ICUs managing critically ill patients with COVID-19. Patients aged ≥ 18 years with confirmed COVID-19 who were admitted to the ICU were included. The present study had two phases. The first phase was designed as a one-day point prevalence study, and demographic and clinical findings were evaluated. In the second phase, the 28-day mortality was evaluated.

Results

As of August 11, 2021, 921 patients were enrolled in the study. The mean age of the patients was 65.42 ± 16.74 years, and 48.6% (n = 448) were female. Among the critically ill patients with COVID-19, 52.6% (n = 484) were unvaccinated, 7.7% (n = 71) were incompletely vaccinated, and 39.8% (n = 366) were fully vaccinated. A subgroup analysis of 817 patients who were unvaccinated (n = 484) or who had received two doses of the CoronaVac vaccine (n = 333) was performed. The 28-day mortality rate was 56.8% (n = 275) and 57.4% (n = 191) in the unvaccinated and two-dose CoronaVac groups, respectively. The 28-day mortality was associated with age, hypertension, the number of comorbidities, type of respiratory support, and APACHE II and sequential organ failure assessment scores (p < 0.05). The odds ratio for the 28-day mortality among those who had received two doses of CoronaVac was 0.591 (95% confidence interval: 0.413-0.848) (p = 0.004).

Conclusion

Vaccination with at least two doses of CoronaVac within six months significantly decreased mortality in vaccinated patients than in unvaccinated patients.

Effects of Supraglottic Airway Devices on Hemodynamic Response and Optic Nerve Sheath Diameter: Proseal LMA, LMA Supreme, and I-gel LMA

Background and Objectives: Supraglottic airway devices (SADs) are known to be useful in eliminating the drawbacks of laryngoscopy and tracheal intubation, especially ocular pressure and stress responses. The ultrasonographic measurement of optic nerve sheath diameter (ONSD) reflects increases in intracranial pressure (ICP). In our study, we aimed to compare the effects of SADs on hemodynamic response and ONSD. Materials and Methods: Our prospective study included 90 ASA I-II patients over the age of 18 who did not have a history of difficult intubation or ophthalmic pathology. The patients were randomly divided into three groups based on the laryngeal mask airway (LMA) devices used: ProSeal LMA (pLMA, n = 30), LMA Supreme (sLMA, n = 30), and I-gel (n = 30). The bilateral ONSD measurements and hemodynamic data of the patients who underwent standard anesthesia induction and monitoring were recorded before induction (T0) and 1 min (T1), 5 min (T5), and 10 min (T10) after SAD placement. Results: At all measurement times, the hemodynamic responses and ONSD values of the groups were similar. In all three groups, intergroup hemodynamic changes at T0 and T1 were similar and higher than those at other times of measurement (p < 0.001). The ONSD values of all groups increased at T1, and they tended to return to baseline values afterward (p < 0.001). Conclusions: We concluded that all three SADs could be used safely because they preserved both hemodynamic stability and ONSD changes in their placement processes, and they did not cause elevations in ONSD to an extent that would lead to increased ICP.

Investigation of preoxygenation methods in cesarean surgeries with the oxygen reserve index

OBJECTIVES

To investigate preoxygenation methods that were carried out for 3 minutes (min) at tidal volume and 30 seconds (s) with the 4 deep vital capacity technique using the Oxygen Reserve Index (ORI) among pregnant women.

METHODS

This prospective study was carried out between December 2020 and 2021. The patients were randomly divided into 2 groups with the provision of preoxygenation using 100% O2 at a rate of 10 L.min-1 for 3 min at normal tidal volume (Group 1) and 30 s with the 4 deep vital capacity technique (Group 2). For the pregnant women who underwent routine anesthesia induction, hemodynamic parameters before preoxygenation, as well as their fraction of inspired O2 (FiO2), fraction of expired O2 (FeO2), and ORI values were recorded after preoxygenation and 0, 3 and 7 minutes after intubation (T1, T2, T3, and T4).

RESULTS

The study was completed with 66 patients. FiO2 values were found to be low in T1 (p=0.012) in Group 1, and high in FeO2 values in T1 and T2 (p=0.025 and 0.009) in Group 2, while no significant differences were found at other times (p>0.05). Oxygen Reserve Index values did not show a significant difference in comparisons between groups, but ORI values of Group 1 after intubation were significantly lower than those measured after preoxygenation in in-group comparisons (p<0.001). According to the results of the correlation analyses between the mean ORI values and their mean FeO2 and FiO2 values, there were weak and positive statistically significant relationships at T3 and T4 (p<0.05).

CONCLUSION

As we obtained greater FiO2 and FeO2 values in preoxygenation with the 30 s 4 deep vital capacity method, and because this method did not cause a significant decrease in the post-intubation ORI values, we believe that the usage of this method in cesarean section surgeries may be appropriate.

The effects of ultrasound-guided serratus anterior plane block on intraoperative opioid consumption and hemodynamic stability during breast surgery: A randomized controlled study

AIM

To determine effect of ultrasound-guided serratus anterior plane block (SAPB) on intraoperative opioid consumption in patients undergoing oncoplastic breast surgery under general anesthesia.

METHODS

This study was conducted as a prospective, randomized controlled trial. Forty-four patients enrolled, aged 18 to 75 years with American Society of Anesthesiologists physical status I to III, undergoing elective oncoplastic breast surgery. Patients were randomly allocated to receive SAPB with 20 mL of 0.25% bupivacaine + general anesthesia (group SAPB) or only general anesthesia (group control). The primary outcome was assessing the effect of SAPB on intraoperative remifentanil consumption. Patients were assessed for emergence time, hemodynamic parameters, doses of rescue drugs used to control hemodynamic parameters, and duration of stay in the recovery room.

RESULTS

Preoperative SAPB with 0.25% bupivacaine reduced intraoperative opioid consumption (851.2 ± 423.5 vs 1409.7 ± 756.1 µg, P = .019). Emergence time was significantly shorter in group SAPB (6.19 ± 1.90 minutes) compared to group control (9.50 ± 2.39 minutes; P < .001). There were no significant differences in the doses of rescue drugs used for systolic blood pressure and heart rate between the groups.

CONCLUSIONS

Preoperative SAPB with bupivacaine reduced intraoperative opioid consumption and shortened emergence time and duration of stay in the recovery unit, and hemodynamic stability was maintained without block-related complications.

Effects of continuous erector spinae plane block on postoperative pain in video-assisted thoracoscopic surgery: a randomized controlled study

BACKGROUND

The aim of this prospective, randomized, controlled study was to evaluate the analgesic effect of ultrasonography (USG) guided continuous erector spinae plane block (ESPB) for postoperative analgesia in video-assisted thoracoscopic surgery (VATS).

METHODS

Eighty American Society of Anesthesiologists (ASA) physical status I-III patients aged 18-75 and who were to undergo VATS were included in this study. Randomization was performed in 2 groups, continuous ESPB (ESPB Group) and no intervention (Control Group). 20 mL of 0.25% bupivacaine was administered for the block. Immediately after surgery, the patient received continuous infusion of 0.125% bupivacaine at 4 mL h^-1 via the catheter inserted for the block. Patients in both groups received tramadol via an intravenous patient-controlled analgesia device. Tramadol and meperidine consumption, visual analog scale pain scores and opioid-related side effects were recorded at 0, 1, 4, 8, 12, 24, 36, and 48 h postoperatively.

RESULTS

The use of continuous ESPB in VATS significantly decreased the amount of tramadol used in the first 48 h postoperatively (P < 0.001). There was a statistically significant difference in the number of meperidine rescue analgesia administered between the ESPB and Control Groups (P < 0.001). While the incidences of nausea and itching were higher in Control Group, there were no differences in terms of the other side effects between the groups.

CONCLUSIONS

This study shows that USG-guided continuous ESPB provides adequate analgesia following VATS as part of multimodal analgesia. Continuous ESPB significantly reduced opioid consumption and opioid-related side effects compared to those in the Control Group.

The effect of PECS-1 block on postoperative pain in total implantable venous access port catheter (TIVAP) insertion

BACKGROUND

The aim of this prospective, randomized, controlled study was to evaluate the analgesic effect of US-guided Pectoral (PECS) I blocks on postoperative analgesia after TIVAP insertion.

METHODS

A hundred-twenty patients were included in this study. The patients were divided into two groups: Group PECS and Group INF (infiltration). A total 0.4 mL kg^-1 0.25% bupivacaine was injected to below the middle of the clavicle in the interfascial space between the pectoralis major and minor muscles for PECS-1. The skin and deep tissue infiltration of the anterior chest wall was performed with 0.4 mL kg^-1 0.25% bupivacaine for INF group. Tramadol and paracetamol consumption, visual analog scale pain scores were recorded at 0, 1, 4, 12, and 24 h postoperatively.

RESULTS

The use of the PECS in TIVAP significantly decreased the amount of paracetamol used in the first 24 h postoperatively (p < 0.001). There was a statistically significant difference in the number of tramadol rescue analgesia administered between the groups (p < 0.001) There was no significant difference between the groups in terms of the VAS scores at 0 and 24 h. However, VAS scores at 1, 4, and 12 h were found to be significantly lower in patients who underwent PECS than in those who received infiltration anesthesia (p < 0.001).

CONCLUSIONS

This study shows that US-guided PECS-1 provides adequate analgesia following TIVAP insertion as part of multimodal analgesia. The PECS-1 significantly reduced opioid consumption.

The effect of laryngoscope types on hemodynamic response and optic nerve sheath diameter. McCoy, Macintosh, and C-MAC video-laryngoscope

OBJECTIVES

This study aims to investigate the effect of McCoy, Macintosh laryngoscope, and C-MAC video-laryngoscopes on optic nerve sheath diameter (ONSD) and hemodynamic responses to laryngoscopy and intubation.

METHODS

This prospective randomized study was conducted in Zonguldak Bülent Ecevit University Hospital, Zonguldak, Turkey, between July 2019 and January 2020. Informed written consent was obtained from all patients. Patients with previous intracranial/ocular surgery or glaucoma were excluded from the study. The patients were randomized to use McCoy, Macintosh, and C-MAC (30 per group). Intubations were performed by the same person. Mean arterial pressure, heart rate (HR), and ONSD were recorded before the induction and repeated in 1, 3, 5, and 10 minutes after the intubation.

RESULTS

The effects of laryngoscopy and intubation on hemodynamic responses and ONSD were similar between groups (p greater than 0.05). While the comparison within groups showed ONSD increase in McCoy group and HR and ONSD increase in the Macintosh group compared to baseline 1 min after the intubation, no change was observed in hemodynamic responses and ONSD measurements in the C-MAC® group (p greater than 0.05).

CONCLUSIONS

In this study, there was no significant difference between the groups in terms of ONSD and hemodynamic responses to laryngoscopy and intubation. It was observed that there were no significant changes in ONSD values just in C-MAC® video-laryngoscope group. Therefore, intubations with C-MAC® video-laryngoscope are thought to be more appropriate for patients with an increase in intracranial pressure.

Neuroprotective effects of Quercetin on radiation-induced brain injury in rats

Extensive research has been focused on radiation-induced brain injury. Animal and human studies have shown that flavonoids have remarkable toxicological profiles. This study aims to investigate the neuroprotective effects of quercetin in an experimental radiation-induced brain injury. A total of 32 adult male Wistar-Albino rats were randomly divided into four groups (control, quercetin, radiation, and radiation+quercetin groups, with eight rats in each group). Doses (50 mg/kg) of quercetin were administered to the animals in the quercetin and radiation+quercetin groups; radiation and radiation+quercetin groups were exposed to a dose of 20 Gy to the cranium region. Tissue samples, and biochemical levels of tissue injury markers in the four groups were compared. In all measured parameters of oxidative stress, administration of quercetin significantly demonstrated favorable effects. Both plasma and tissue levels of malondialdehyde and total antioxidant status significantly changed in favor of antioxidant activity. Histopathological evaluation of the tissues also demonstrated a significant decrease in cellular degeneration and infiltration parameters after quercetin administration. Quercetin demonstrated significant neuroprotection after radiation-induced brain injury. Further studies of neurological outcomes under different experimental settings are required in order to achieve conclusive results.

Pseudocholinesterase levels in patients under electroconvulsive therapy

Objectives:

In this study, we aimed to retrospectively assess the correlation of pseudocholinesterase (PChE) levels with age, gender, body weight and diagnosed psychiatric diseases in electroconvulsive therapy (ECT) cases.

Methods:

This retrospective study was conducted at Bülent Ecevit University Hospital, Zonguldak, Turkey, between 2007 and 2011. In the study, 193 ECT case files were retrospectively scanned to evaluate PChE values before ECT and other file information.

Results:

There was no difference between gender in terms of PChE levels. Correlation analysis determined a weakly positive correlation between age (p=0.013; correlation coefficient [cc]: 0.178) and body weight (p<0.001; cc: 0.273) and PChE levels. No correlation was found between age, gender, weight or psychiatric diagnosis, and PChE levels.

Conclusion:

Neuromuscular blockage is a significant factor that increases patient safety, while increasing the efficacy of ECT. In choosing muscle relaxant agents, both patient factors and the pharmacological properties of the neuromuscular blocker should be considered. We think that in situations with delayed recovery of ECT cases without identified PChE levels, low PChE levels must be considered.

Accuracy of pleth variability index compared with inferior vena cava diameter to predict fluid responsiveness in mechanically ventilated patients

In the intensive care unit (ICU), stable hemodynamics are very important. Hemodynamic intervention is often effective against multiple organ failure, such as in tissue hypoxia and shock. The administration of intravenous fluids is the first step in regulating tissue perfusion.The main objective of this study is to compare the performance between 2 methods namely pleth variability index (PVI) and IVC distensibily index (dIVC).In this study, the hemodynamic measurements were performed before and after passive leg raising (PLR). Measurements were obtained, including, PVI, dIVC, and cardiac index (CI). Both CI and dIVC measurements were evaluated by transesophageal probe and convex probe respectively. The dIVC measurements were taken using M-mode, 2 cm from junction between the right atrium and the inferior vena cava. The PVI was measured by Masimo Radical-7 monitor, Masimo.A total of 72 patients were included. The dIVC at a threshold value of >23.8% provided 80% sensitivity and 87.5% specificity to predict fluid responsiveness and was statistically significant (P < .001), with an AUC 0.928 (0.842-0.975). The PVI at a threshold value of >14% provided 95% sensitivity and 81.2% specificity to predict fluid responsiveness and was statistically significant (P < .001), with an AUC 0.939 (0.857-0.982).Both PVI and dIVC can be used as a noninvasive method that can be easily applied at the bedside in determining fluid responsiveness in all patients with mechanical ventilation in intensive care.

Effects of insulin+glucose pretreatment on bupivacaine cardiotoxicity in rats

A mistaken overdose of bupivacaine into systemic circulation may cause severe cardiovascular side effects. The aim of this study was to assess the effects of pretreatment with combined intra venous lipid emulsion (ILE) and high-dose insulin therapy against cardiotoxicity caused by bupivacaine intoxication. The rats were divided into the following three groups: Group B received a saline pretreatment plus a bupivacaine, group L received ILE pretreatment plus a bupivacaine, and in group I, insulin with glucose was infused intravenously, plus ILE pretreatment plus a bupivacaine. The electrocardiogram tracing, invasive arterial pressure, and heart rate (HR) of rats were monitored continuously. Arterial blood gas analysis was performed in all groups. Arterial blood gas analysis revealed that the baseline pH, PaO₂, and PaCO₂ values were similar between groups ( p > 0.05). Widening of Q, R, and S wave complex was found 46.8 ± 16.7, 92.0 ± 5.80, and 106.5 ± 17.9 s after initiation of bupivacaine infusion in groups B, L, and I, respectively. Time elapsed until 25% reduction of HR 127.3 ± 17.7, 248.4 ± 34.1, and 260.1 ± 51.3 s for groups B, L, and I, and 25% reduction of mean arterial pressure 107.6 ± 14.1, 253.2 ± 36.3, and 292 ± 57.7 s for groups B, L, and I, respectively. Arrhythmia was observed after 142.2 ± 27.5, 180.7 ± 17.8, and 190.7 ± 19.2 s for groups B, L, and I, respectively. Finally, asystole occurred after 560.1 ± 76.4, 782.4 ± 63.0, and 882.5 ± 105.1 s for groups B, L, and I, respectively. This finding indicates that the survival time of rats administered pretreatment with ILE plus insulin+glucose and those given ILE was observed to be longer.

Anesthesia methods used by anesthetic specialists for circumcision cases. National survey study for Turkey

Objectives:

To examine the anesthesiologist’s choice for anesthesia techniques and drugs in circumcision and determine the preoperative examination, intraoperative monitoring techniques, postoperative analgesia methods, and common complications among anesthesiologists working in Turkey.

Methods:

This cross-sectional study was conducted at Bulent Ecevit University Hospital, Zonguldak, Turkey, between May and July 2012. Survey data were obtained via survey forms through electronic data over the web. The questionnaire consists of 20 questions. These questions included demographic data, methods of anesthesia for circumcision, postoperative analgesia methods, and monitoring methods.

Results:

The data were obtained from 206 anesthesiologists who agreed to participate in the survey. Circumcision was performed most frequently in the age group of 3-6 years old. It was found that 47% of routine preoperative laboratory tests were coagulation parameters and complete blood count tests. The most common method of anesthesia was laryngeal mask. The frequency of administration of regional anesthesia was 37.4%, and caudal block was more preferable. Bupivacaine as a local anesthetic in regional anesthesia and midazolam and ketamine were the most preferred agents in sedoanalgesia. During regional anesthesia, ultrasound was most often used by anesthesiologists (31.6%).

Conclusion:

Ambulatory anesthesia protocols, which are also needed in circumcision, can be improved with international recommendation, and these protocols could be conformed as sociocultural structure in societies. This study should be regarded as a preliminary study to attract attention on anesthesia techniques in circumcision.

The effect of sugammadex on postoperative cognitive function and recovery

BACKGROUND AND OBJECTIVE

Sugammadex is the first selective relaxant binding agent. When compared with neostigmine, following sugammadex administration patients wake earlier and have shorter recovery times. In this study, we hypothesized that fast and clear awakening in patients undergoing general anesthesia has positive effects on cognitive functions in the early period after operation.

METHODS

Approved by the local ethical committee, 128 patients were enrolled in this randomized, prospective, controlled, double-blind study. Patients were allocated to either Sugammadex group (Group S) or the Neostigmine group (Group N). The primary outcome of the study was early postoperative cognitive recovery as measured by the Montreal Cognitive Assessment (MoCA) and Mini Mental State Examination (MMSE). After baseline assessment 12-24h before the operation. After the operation, when the Modified Aldrete Recovery Score was ≥9 the MMSE and 1h later the MoCA tests were repeated.

RESULTS

Although there was a reduction in MoCA and MMSE scores in both Group S and Group N between preoperative and postoperative scores, there was no statistically significant difference in the slopes (p>0.05). The time to reach TOF 0.9 was 2.19min in Group S and 6.47min in Group N (p<0.0001). Recovery time was 8.26min in Group S and 16.93min in Group N (p<0.0001).

CONCLUSION

We showed that the surgical procedure and/or accompanying anesthetic procedure may cause a temporary or permanent regression in cognitive function in the early postoperative period. However, better cognitive performance could not be proved in the Sugammadex compared to the Neostigmine.

[The effect of sugammadex on postoperative cognitive function and recovery]

BACKGROUND AND OBJECTIVE

Sugammadex is the first selective relaxant binding agent. When compared with neostigmine, following sugammadex administration patients wake earlier and have shorter recovery times. In this study, we hypothesized that fast and clear awakening in patients undergoing general anesthesia has positive effects on cognitive functions in the early period after operation.

METHODS

Approved by the local ethical committee, 128 patients were enrolled in this randomized, prospective, controlled, double-blind study. Patients were allocated to either Sugammadex group (Group S) or the Neostigmine group (Group N). The primary outcome of the study was early postoperative cognitive recovery as measured by the Montreal Cognitive Assessment (MoCA) and Mini Mental State Examination (MMSE). After baseline assessment 12-24h before the operation. After the operation, when the Modified Aldrete Recovery Score was ≥9 the MMSE and 1h later the MoCA tests were repeated.

RESULTS

Although there was a reduction in MoCA and MMSE scores in both Group S and Group N between preoperative and postoperative scores, there was no statistically significant difference in the slopes (p>0.05). The time to reach TOF 0.9 was 2.19min in Group S and 6.47min in Group N (p<0.0001). Recovery time was 8.26min in Group S and 16.93min in Group N (p<0.0001).

CONCLUSION

We showed that the surgical procedure and/or accompanying anesthetic procedure may cause a temporary or permanent regression in cognitive function in the early postoperative period. However, better cognitive performance could not be proved in the Sugammadex compared to the Neostigmine.

Postdural puncture subdural hematoma or postdural puncture headache?: two cases report

Spinal anesthesia is widely used for many obstetric, gynecological, orthopedic, and urological operations. Subdural hematomas may occur after trauma and are associated with high morbidity and mortality rates. Postdural puncture headache (PDPH) is a benign condition and the most frequent complication of spinal anesthesia. The high rate of headache after spinal anesthesia may mask or delay the diagnosis of subdural hematoma. The true incidence of postdural puncture subdural hematoma (PDPSH) is unknown because most affected patients are probably managed without investigation. Therefore, the true incidence of PDPSH may be greater than suggested by previous reports. The differentiation of headache associated with subdural hematoma from PDPH is crucial. We herein report two cases of bilateral subdural hematoma after epidural anesthesia and emphasize the importance of suspicion for PDPSH and careful evaluation of patients with headache after spinal anesthesia.

Effect of Sialic Acid on Platelet Cryopreservation

Sialic acid is a molecule which is responsible for the net negative surface charge of platelets. We investigated the effect of sialic acid on fresh and cryopreserved platelets. Platelet samples were obtained by platelet apheresis from 8 healthy donors. Platelet suspensions with different sialic acid concentrations (0, 1, 2 and 4 mg/mL) were studied for ADP and ristocetin induced platelet aggregation, basal and ADP induced P-selectin and glycoprotein- Ib/IX expression. Then platelet samples were cryopreserved in 5% DMSO with or without 4 mg/mL sialic acid. After thawing, P-selectin expression was compared with the control group. Six samples were also washed after thawing and P-selectin expression was again compared to unwashed samples. Sialic acid suppressed ADP induced platelet aggregation and P-selectin expression in a dose dependent manner. In cryopreserved samples, P-selectin expression of 4 mg/mL sialic acid containing group was found significantly higher than the control group (p< 0.001). In cryopreserved control group, P-selectin expression of thawedwashed group was significantly higher than thawed-unwashed group (p< 0.05). Our results indicate that sialic acid is not a good cryoprotective agent. Washing procedure after thawing to eliminate DMSO causes significant platelet activation.