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Biomedical subjects

C M Samama

Publications and source records attributed to C M Samama.

At least 37 records · Page 2Linked to original sources

Hemostatic changes in patients receiving hydroxyethyl starch: the influence of ABO blood group.

Hydroxyethyl starches (HES) interfere with coagulation because of their molecular structure and the amount infused during surgery. Coagulation defects include platelet dysfunction and a decrease of the VIII/von Willebrand factor complex (VIII/vWF). We examined the effects of 6% HES 200/0.6 on hemostasis by using an in vitro platelet function analyzer, the usual coagulation tests, the VIII/vWF complex assessment, and TEG analysis in patients undergoing abdominal surgery. The influence of the blood group was investigated. HES infusion induced primary hemostasis alterations, assessed by a prolonged platelet function analyzer closure time in the presence of epinephrine and adenosine diphosphate, which was not correlated with the platelet count. The decrease in VIII/vWF complex was proportional to the volume of infused HES (20 and 30 mL/kg) and was more pronounced in patients of the O blood group. The preoperative hypercoagulability status assessed by TEG analysis was reversed 24 h after HES infusion. In conclusion, 6% HES 200/0.6 induced immediate hemostasis alterations. Patients of the O blood group were likely to develop a von Willebrand-like syndrome after HES infusion. We conclude that intraoperative use of 6% HES 200/0.6 should be restricted in patients of the O blood group undergoing surgical procedures with high risk for bleeding.

ABO Blood-Group System↗

Perioperative activation of hemostasis in vascular surgery patients.

BACKGROUND: Perioperative activation of hemostasis could play an important role in the occurrence of postoperative cardiac events. The authors conducted a prospective study to assess platelet function, coagulation, and fibrinolysis status during and after infrarenal aortic surgery. METHODS: Seventeen patients were studied. Excluded were patients with preoperative coagulopathies or liver disease, or cardiac or renal insufficiency; patients receiving anticoagulant treatment, antiplatelet agents, nonsteroidal antiinflammatory agents, fresh frozen plasma, or platelet concentrates; and patients undergoing reoperation and septic patients. Blood samples were drawn before induction (T1), 1 h after incision (T2), 1 h after extubation (T3), 24 h postoperatively (T4), 48 h postoperatively (T5), and at day 7 (T6). The following tests were performed: platelet count, platelet aggregation, platelet flow cytometry for CD62 and CD63, usual coagulation tests, thrombin--antithrombin complexes, plasminogen activator inhibitor 1. RESULTS: A significant increase of adenosine diphosphate--induced platelet aggregation was observed postoperatively at T4 and T5. This was not associated with a change of flow cytometry profile. No increase of thrombin--antithrombin complex levels was observed. A higher fibrinogen rate was detected at T5 and T6. Greater amounts of plasminogen activator inhibitor 1 were detected at T3 and T4. Thus, thrombin generation was limited and fibrinolysis was impaired postoperatively. Platelets were not activated in the postoperative period, as shown by flow cytometry, but were prone to be activated, as shown by aggregation studies. CONCLUSION: The association of more easily activated platelets with a higher fibrinogen rate and a temporary shut down of fibrinolysis during the early postoperative period may indicate an increased thrombotic risk in patients undergoing major vascular surgery.

Aged↗

Residual curarization in the recovery room after vecuronium.

We have investigated residual block after anaesthesia which included the use of the neuromuscular blocking agent vecuronium but no anticholinesterase, in 568 consecutive patients on admission to the recovery room. The ulnar nerve was stimulated submaximally using TOF stimulation (30 mA). Postoperative residual curarization was defined as a TOF ratio < 0.7. Of the 568 patients, 239 (42%) had a TOF < 0.7 in the recovery room. These patients had received a larger cumulative dose of vecuronium than patients who had full recovery (mean 7.7 (SD 3.6) mg vs 6.2 (2.7) mg; P < 0.05) and a shorter time had elapsed since the last vecuronium dose (117 (70) min vs 131 (80) min; P < 0.05). Of 435 patients whose trachea was extubated, 145 (33%) exhibited inadequate recovery from neuromuscular block. Six of these had one or no response to TOF stimulation and were reintubated. In the remaining 139 patients, neuromuscular block was successfully antagonized. Only 20 patients (3.5%) remembered TOF stimulation when questioned 2 h later in the recovery room, and discomfort associated with it was assessed using a visual analogue scale before discharge. We conclude that it is necessary to antagonize residual block produced by vecuronium.

Adolescent↗

Role of the hematocrit in a rabbit model of arterial thrombosis and bleeding.

BACKGROUND: A decrease in hematocrit lengthens bleeding time. The authors studied the role of hematocrit variations in an experimental model of arterial thrombosis and bleeding. METHODS: The Folts model was used in 24 rabbits. After anesthesia was induced and common monitors were positioned, the right common carotid artery was exposed and a 60% stenosis was induced. A compression injury of the artery was then produced, which triggered a series of cyclic episodes of thrombosis and clot lysis (cyclic flow reductions [CFRs]). After counting the number of CFRs that occurred in 20 min (CFR1), the animals were assigned randomly to one of three groups (n = 8 in each group): control, hemodilution with rabbit homologous platelet-rich plasma, and hemodilution with gelatin solution and then reinfusion of the shed blood. The effect of hemodilution with replacement by platelet-rich plasma or by colloid was observed by recording the number of CFRs during another 20-min period (CFR2). A third period of observation (CFR3) followed shed blood reinfusion in the gelatin solution group. Ear immersion bleeding time was recorded after each CFR period. RESULTS: In the two experimental groups, the decrease in hematocrit (from 36 +/- 3% to 23 +/- 2% and from 38 +/- 3% to 23 +/- 2%, respectively; mean +/- SD) abolished CFRs (from a median of 4 to 0 and 7 to 0, respectively) and significantly lengthened bleeding time (from 76 +/- 24 s to 114 +/- 36 s and from 84 +/- 37 s to 127 +/- 29 s, respectively). Blood reinfusion in the group that received the gelatin solution caused CFR to reappear (CFR3 = 4). CONCLUSIONS: Decreases in hematocrit reduced the cyclic arterial thrombosis rate and increased the bleeding time in the rabbits in this study. Hematocrit normalization caused thrombosis to reappear.

Animals↗

[The good use of drugs derived from blood].

Rational use of blood-derived products should only be viewed in close collaboration with haemostasis laboratory teams, pharmacists and transfusion centers. The crucial role of a detailed clinical interview can never be emphasized enough. The use of blood-derived products or the elaboration of new therapeutic strategies should always be mentioned in a written protocol. These procedures clearly belong to quality control implementation. The patient as well as the surgical team should always be aware of haemostasis procedures.

Blood↗

Ketorolac and enoxaparin affect arterial thrombosis and bleeding in the rabbit.

BACKGROUND: Nonsteroidal anti-inflammatory drugs (NSAIDs) may interfere with hemostasis during the perioperative period, and the combination of NSAID and enoxaparin could increase this effect. The aim of this prospective, blinded experimental study was to assess these effects using a model of arterial thrombosis and bleeding in the rabbit. METHODS: After anesthesia was induced and monitors placed, the common carotid arteries were exposed, and 60% stenosis of the right common carotid artery was produced. Twenty minutes later, a compression injury of the artery was produced that triggered a series of cyclic episodes of thrombosis and clot lysis. This was manifested as cyclic flow reductions (CFR; measured with an electromagnetic flow meter). After the first flow reduction was noted, the rabbits were immediately and randomly assigned to one of four groups (n = 10 each) that received intravenous infusions: control, ketorolac (2 mg/kg), enoxaparin (0.5 mg/kg), and ketorolac plus enoxaparin (2 mg/kg and 0.5 mg/kg, respectively). The number of CFRs that occurred in the subsequent 20-min period was used as a measure of treatment effect. The contralateral common carotid artery was exposed, and both stenosis and injury were produced. The ability of the administered drug to prevent thrombosis was assessed as the number of CFRs that occurred during the first 20-min period after vessel injury. In addition, both before and after group assignment and drug injection, bleeding times were noted and a platelet aggregation test was performed. Laparotomy was followed by a spleen section, and the extent of the wound and the amount of splenic bleeding were measured. RESULTS: The treatment effect was indicated by the median number of CFRs, which was 5.5 in the control group, 1 in the ketorolac group, 2 in the enoxaparin group, and 0 in the ketorolac + enoxaparin group. The prevention effect was indicated by the median number of CFRs, which was 4 in the control group, 0 in the ketorolac group, 2 in the enoxaparin group, and 0.5 in the ketorolac + enoxaparin group. Bleeding time was significantly lengthened in the enoxaparin and in the ketorolac + enoxaparin groups. Splenic and wound bleeding was greater in the ketorolac group. Platelet aggregation was completely inhibited in the ketorolac and the ketorolac + enoxaparin groups. CONCLUSIONS: Ketorolac had an important antithrombotic activity. The association of enoxaparin with ketorolac seemed to lengthen the bleeding time observed with ketorolac.

Animals↗

[Management of a suspicion of heparin-induced thrombopenia].

UNLABELLED: A COMPLEX SITUATION: During the acute phase of heparin-induced thrombocytopenia, the question must be raised as to whether an antithrombotic therapy is to be continued using a compound other than heparin. Later the risk of reintroducing heparin again can be discussed. THERAPEUTIC PROPOSITIONS: Excepting vena cava interruption, surgical revascularization and thrombolysis, possible therapeutic propositions can be divided into two categories; anticoagulants and related compounds (hirudin); and oral anticoagulants (anti-vitamin K) and antiplatelet agents (aspirin for example). Low molecular-weight heparin cannot be recommended in 1998 in patients with heparin-induced thrombocytopenia due to standard heparin. IN PRACTICE: Unfractionated heparin or low-molecular weight heparin must be stopped immediately. The hematology laboratory should be consulted. It must be remembered that prevention, based on a careful assessment of the benefit/risk ratio when initiating heparin therapy, is essential.

Anticoagulants↗

Low molecular weight heparin associated with spinal anaesthesia and gradual compression stockings in total hip replacement surgery. Arar Study Group.

The benefit/risk ratio of administering heparin during spinal anaesthesia in patients undergoing total hip replacement (THR) has not been studied widely. We conducted a prospective, randomized, double-blind study to compare low molecular weight heparin (LMWH) for 10 days and placebo in patients undergoing THR performed under spinal anaesthesia associated with gradual compression stockings. Efficacy was assessed by systematic bilateral ascending venography on day 10 +/- 2 in a sequential analysis. Among the 170 patients enrolled, data were available in 153 patients. In the LMWH group (n = 78) the total incidence of deep vein thrombosis (DVT) was 14.1% compared with 37.3% in the placebo group (n = 75) (P = 0.0016). No gross neurological sequelae were observed during the study. This study showed that the addition of LMWH in patients undergoing THR under spinal anaesthesia and wearing gradual compression stockings significantly decreased the incidence of venogram-proved DVT.

Adult↗

Are low-molecular-weight heparins useful for the prophylaxis and treatment of arterial thrombi?

The pharmacologic specificity of low-molecular-weight heparins (LMWHs) has enabled multiple attractive developments in the prophylaxis and treatment of arterial thrombosis. Their high antithrombotic potency associated with a potentially lower induced bleeding risk, the lack of platelet interaction, the prevention of myointimal hyperplasia, and the lower incidence of heparin-induced thrombocytopenia, are major advantages. New studies in cardiology and vascular surgery demonstrate a high efficacy for LMWHs associated with a low risk.

Anticoagulants↗

[Should we give up combining spinal anesthesia and anticoagulants?].

The risk of lumbar haematoma potentially increased by the association of regional anaesthesia and anticoagulant treatment has been widely debated. Few data are available in order to estimate the level of this risk, which is probably very low. However, even if it is now clear that regional anaesthesia is not potent enough to prevent postoperative deep vein thrombosis (DVT), a partial decrease in the DVT rate between 30 and 40% has been observed. Furthermore, no randomized double blind study has established the usefulness of the preoperative injection of heparin. Accordingly, when it is possible, it is best to avoid the preoperative injection and to start heparin treatment postoperatively. This solution is safe and effective.

Anesthesia, Spinal↗

Function of von Willebrand factor after crossed bone marrow transplantation between normal and von Willebrand disease pigs: effect on arterial thrombosis in chimeras.

von Willebrand factor (vWF) is essential for the induction of occlusive thrombosis in stenosed and injured pig arteries and for normal hemostasis. To separate the relative contribution of plasma and platelet vWF to arterial thrombosis, we produced chimeric normal and von Willebrand disease pigs by crossed bone marrow transplantation; von Willebrand disease (vWD) pigs were engrafted with normal pig bone marrow and normal pigs were engrafted with vWD bone marrow. Thrombosis developed in the chimeric normal pigs that showed normal levels of plasma vWF and an absence of platelet vWF; but no thrombosis occurred in the chimeric vWD pigs that demonstrated normal platelet vWF and an absence of plasma vWF. The ear bleeding times of the chimeric pigs were partially corrected by endogenous plasma vWF but not by platelet vWF. Our animal model demonstrated that vWF in the plasma compartment is essential for the development of arterial thrombosis and that it also contributes to the maintenance of bleeding time and hemostasis.

Animals↗

[Comparison of the effects of ketorolac and aspirin on hemostasis in the rabbit].

OBJECTIVE: Comparison of ketorolac with aspirin and placebo for the antithrombotic activity using the Folts' model of experimental arterial thrombosis and the perioperative blood loss. STUDY DESIGN: Experimental randomized blinded study anaesthetized, tracheotomized and mechanically ventilated. Carotid blood flow variations were detected by a probe directly inserted around the artery and monitored by an electromagnetic flowmeter. A segment of the exposed carotid artery was de-endothelialized by gently squeezing the artery with a needle holder forceps, and an external constrictor was placed around it (stenosis 60%), to induce cyclic flow reductions (CFR). During 20 min, CFR rate was assessed. Animals were then randomized in 3 groups of 9: ketorolac (K) 1 mg.kg-1, aspirin (A) 10 mg.kg-1 or saline (S), injected intravenously (peripheral ear vein). After drug administration, CFR rate was assessed over 20 min, to determine the potential antithrombotic activity of the drug (curative phase). Thereafter, the opposite carotid artery was injured and stenosed and the occurrence of CFR was assessed over 20 min (preventive phase). The amount of blood loss of a xipho-pubic laparotomy with a spleen section was also measured 30 min after drug administration. RESULTS: In all untreated animals, CFRs developed with a mean rate of 4 cycles/20 min. Aspirin completely abolished CFR during the curative phase in all rabbits, except in one. No effect was observed during this phase with ketorolac or saline. During the preventive phase, a partial inhibition of CFRs was induced by ketorolac and aspirin. Peri-operative bleeding was not increased significantly by ketorolac or aspirin. Postinjection bleeding-time did not differ between the three groups. CONCLUSIONS: Ketorolac (1mg.kg-1) has not a strong antithrombotic activity. Ketorolac and aspirin do not increase peri-operative blood loss, and therefore do not seem to strongly interfere with haemostasis in the rabbit.

Animals↗

Low-molecular-weight heparin vs. unfractionated heparin in femorodistal reconstructive surgery: a multicenter open randomized study. Enoxart Study Group.

Several clinical trials have been conducted to study the role of low-molecular-weight heparin (LMWH) in the prevention and treatment of venous thrombosis. In contrast, there have been few studies investigating LMWH in the prophylaxis in arterial thrombosis. After informed consent and institutional approval were obtained, 201 consecutive patients scheduled for femorodistal reconstructive surgery under general anesthesia were enrolled in an open randomized multicenter (n = 14) study (from November 1990 to November 1992). Immediately before arterial cross-clamping, patients were given an intravenous bolus of either enoxaparin (ENX), 75 anti-Xa IU/kg (n = 100), or unfractionated heparin (UFH), 50 IU kg (n = 101). Meanwhile the saphenous vein or a prosthetic graft was flushed with ENX (25,000 anti-Xa IU) or UFH (25,000 IU) in 250 ml of saline solution. Subsequent treatment consisted of subcutaneous administration of ENX, 75 anti-Xa IU/kg, or UFH, 150 IU kg, beginning 8 hours after the intravenous injection and then every 12 hours thereafter for 10 days. The primary end point was graft patency on day 10 +/- 2 after surgery as assessed clinically and/or by arteriography on day 10 +/- 2 and/or during reintervention or autopsy. Analysis of patients on an intention-to-treat basis (patients who received at least on injection of ENX or UFH and who had at least one end-point evaluation) showed that graft thrombosis occurred in 30 of 199 cases: eight (8%) in the ENX group and 22 (22%) in the UFH group (p = 0.009). Among the 131 patients who were evaluated by arteriography before day 12, twelve (9.1%) had graft thrombosis: four (6%) in the ENX group and eight (12.5%) in the UFH group (NS). There were no significant differences between the two groups in terms of safety--that is, there were 12 major hemorrhages in each group, and during the follow-up period five patients in the ENX group died compared to nine in the UFH group (NS). These results indicate that ENX is as safe as but more effective than UFH when used for the prevention of early graft thrombosis in patients undergoing femorodistal reconstructive surgery.

Adult↗

Inhibition of platelet aggregation by inhaled nitric oxide in patients with acute respiratory distress syndrome.

BACKGROUND: Nitric oxide inhibits platelet adhesion and aggregation in vitro. The aim of this prospective study was to assess the platelet antiaggregating activity of nitric oxide administered to patients with acute respiratory distress syndrome (ARDS) at increasing concentrations. METHODS: In six critically ill patients (mean age 37 +/- 16 yr) with ARDS (lung injury severity score > or = 2.2), the lungs were mechanically ventilated with inhaled nitric oxide (1, 3, 10, 30, and 100 ppm) randomly administered. Patients with cardiac dysrhythmias, septic shock, an underlying hemostasis disorder (constitutive or acquired), a platelet count less than 100 Giga/l, or a decreased platelet aggregation and those treated with antiplatelet or anticoagulant agents were excluded. Platelet aggregation was measured without nitric oxide and at each nitric oxide concentration in platelet-rich plasma issued from radial artery. Ivy bleeding time using a horizontal incision was simultaneously performed. RESULTS: After nitric oxide, a non-dose-dependent but statistically significant decrease in ex vivo platelet aggregation induced by three aggregating agents was observed: adenosine diphosphate = -56 +/- 18%, collagen = -37 +/- 18%, and ristocetin = -45 +/- 18% (P < 0.05). In each individual, Ivy bleeding time remained within normal values measured in healthy volunteers, and variations after nitric oxide did not correlate with changes in platelet aggregation. Simultaneously, arterial oxygenation improved significantly and pulmonary artery pressure decreased significantly. CONCLUSIONS: In patients with ARDS and without preexisting coagulation disorders, the beneficial effects of inhaled nitric oxide on arterial oxygenation and pulmonary circulation are associated with a significant inhibition of platelet aggregation. This antithrombotic effect is not associated with a significant prolongation of the bleeding time.

Acute Disease↗

[Traumatic emergencies and hemostasis].

The occurrence of bleeding in trauma patients is a life-threatening problem which can be explained by different mechanisms. The infusion of cristalloids, colloids, packed red blood cells, or even fresh frozen plasma is very rarely responsible for bleeding but it can contribute to dilute the patient's platelet pool, and especially dilutional thrombocytopenia is the first cause of bleeding after massive transfusion. Blood coagulation factor activity is decreased after a massive fluid infusion is performed but it has to reach a dramatically low plasma level in order to induce troubles. It has to be emphasized that colloids and especially dextrans can impair the patient's haemostasis by interfering the same way with the factor VIII-von Willebrand complex and fibrin formation. Gelatins do not interfere with platelets or with the coagulation system. A third mechanism that can explain the strong link between haemostasis and haemodilution is the haemostatic role of red cells. It has been shown in experimental models that red cells play a definite function in promoting platelet accretion on the damaged vessel surface. Higher values of haematocrit (Ht) are responsible for a better platelet adhesion On the opposite, platelet adhesion decreases when low values of Ht (< 20%) are reached. Hypothermia can also impair platelet function and worsen the bleeding. A simplified monitoring of haemostasis can be proposed with platelet count, whole blood coagulation clotting time, immediately available activated partial thromboplastin time and prothrombin time with bedside portable monitors and thromboelastography. Haematocrit and body temperature have to be monitored as well.

Blood Coagulation Disorders↗

Dipyridamole-thallium scintigraphy and gated radionuclide angiography to assess cardiac risk before abdominal aortic surgery.

BACKGROUND: Because many patients with atherosclerotic disease of the abdominal aorta also have coronary artery disease, assessment of cardiac risk before abdominal aortic surgery has received much attention. Our prospective study was designed to identify predictors of cardiac risk in consecutive patients evaluated preoperatively with dipyridamole-thallium single-photon-emission computed tomography (SPECT) to assess myocardial perfusion and radionuclide angiography to measure left ventricular ejection fraction. METHODS: Clinical and scintigraphic data were collected prospectively during hospitalization in 457 consecutive patients undergoing elective abdominal aortic surgery. Adverse cardiac outcomes were predicted with multivariate analyses. RESULTS: Eighty-six patients (19 percent) had one or more of the following postoperative complications: prolonged myocardial ischemia (61 patients), myocardial infarction (22), congestive heart failure (20), and severe ventricular tachyarrhythmia (2). Twenty patients died postoperatively (4.4 percent), half of them from cardiac causes. Information about myocardial perfusion obtained from dipyridamole-thallium SPECT did not accurately predict adverse cardiac outcomes. The best correlates of cardiac complications were definite clinical evidence of coronary artery disease (odds ratio, 2.6; 95 percent confidence interval, 1.6 to 4.3) and age greater than 65 years (odds ratio, 2.3; 95 percent confidence interval, 1.4 to 3.6). Measurement of the ejection fraction was useful only in the prediction of left ventricular failure. Age greater than 65 years was the only predictor of death (odds ratio, 26.4; 95 percent confidence interval, 3.5 to 200.0). CONCLUSIONS: The presence of definite clinical evidence of coronary artery disease and older age were the most important preoperative predictors of an adverse cardiac outcome after abdominal aortic surgery. These results suggest that the routine use of dipyridamole-thallium SPECT and radionuclide angiography for screening before abdominal aortic surgery may not be justified.

Aged↗

Aprotinin to decrease bleeding and intraoperative blood transfusion requirements during descending thoracic and thoracoabdominal aortic aneurysmectomy using cardiopulmonary bypass.

The purpose of this retrospective study was to assess the efficacy of aprotinin, an antifibrinolytic agent, in reducing bleeding and blood transfusion requirements in patients undergoing descending thoracic or thoracoabdominal aortic aneurysmectomy using cardiopulmonary bypass (CPB). Sixty-nine consecutive patients underwent thoracic or thoracoabdominal aneurysmectomy using CPB in a 2-year period. None of the 29 patients operated on in 1990 (group 1) received aprotinin, whereas all 40 patients operated on in 1991 (group 2) were placed on a high-dose regimen of aprotinin. There were no significant differences between the two groups. Administration of aprotinin was associated with a decrease in CPB time (p = 0.02), surgical duration (p = 0.05) and intraoperative blood loss (p = 0.008) as well as a reduction in intraoperative packed red cells (p = 0.01), Cell-Saver units (p = 0.05), fresh-frozen plasma units (p = 0.002), and platelet concentrate (p = 0.01) requirements. These data suggest that aprotinin is effective in reducing bleeding and blood transfusion requirements during descending thoracic or thoracoabdominal aortic aneurysmectomy using CPB.

Adult↗

Intraoperative measurement of activated partial thromboplastin time and prothrombin time with a new compact monitor.

A prospective study was conducted to evaluate a new compact portable coagulation monitor (Ciba-Corning Biotrack 512 Monitor), which enables the clinician to perform instantaneous activated partial thromboplastin time (APTT) and prothrombin time (PT). 126 patients scheduled for heparinized and nonheparinized vascular surgery, and gynaecological surgery, were included. A drop of capillary or venous whole blood was applied in disposable cartridges to successively perform APTT and PT, and the results of the tests were compared with conventional laboratory methods, performed in two different laboratories (Lab. A and B). Comparisons between Lab. A. and Lab. B. enables determination of the bias, precision, and percent of outliers (patients whose values differed more than 20%) in conventional methods. The reference value was defined as the mean of Lab. A. and Lab. B. values. For PT, there were no statistical differences between the capillary and venous samples performed with the portable monitor, and the reference value, for the bias, the precision and the proportion of outliers. For APTT, there were no statistical differences between the capillary and venous samples performed with the portable monitor, and the reference value, for the bias and the precision. The percent of outliers, however, was significantly greater with the venous sample of the compact monitor than with the reference (48 versus 22%), and even if it did not reach the statistical significance (P = 0.07) it was also higher with the capillary sample performed with the Ciba Monitor than with the reference (33%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗