Esophageal Motility during General Anesthesia Laryngeal Mask Airway Versus Endotracheal Tube / 대한마취과학회지

BACKGROUND: To know whether the laryngeal mask airway (LMA) triggers a pharyngo-esophago- gastric reflex during general anesthesia, we compared the esophageal motility of patients with an LMA or endotracheal tube (ETT) in place. METHODS: Fifty patients (ASA I or II) scheduled for elective orthopedic surgery with general anesthesia were randomly allocated into LMA (n = 30) or ETT (n = 20) groups. The esophageal manometric inputs were recorded continuously using an ambulatory esophageal manometric recorder and divided into five perioperative phases (preanaesthesia, induction, operation, LMA or ETT rejection, and arousal phase). RESULTS: The peristaltic percent and number of contractions per minute were significantly decreased during induction, operation, LMA or ETT rejection and arousal phases compared with preanesthetic phases in both the LMA and ETT groups. However, there were no significant group differences in any corresponding perioperative phases. CONCLUSIONS: We suggest that during general anesthesia the use of a LMA does not provoke significantly different esophageal peristalsis compared with an ETT. Thus, the LMA is unlikely to potentiate gastric regurgitation and reflux during general anesthesia by stimulating the pharyngo-esophago-gastric reflex.

Inhibitory Effects of Propofol Mixed with Lidocaine on Fentanyl Induced Cough Reflex / 대한마취과학회지

BACKGROUND: Propofol and lidocaine have been purported to attenuate bronchoconstriction induced by fentanyl administration during induction of anesthesia. The purpose of the present study was to study the synergic bronchodilation effect of propofol mixed with lidocaine. METHODS: Two hundred and thirty four patients were randomly allocated to five groups: Group 1 (n = 60, normal saline 0.25 ml/kg followed by fentanyl 3ng/kg), Group 2 (n = 30, propofol 2 mg/kg mixed with normal saline 0.05 ml/kg followed by normal saline 0.06 ml/kg), Group 3 (n = 50, propofol 2 mg/kg mixed with normal saline 0.05 ml/kg followed by fentanyl 3ng/kg), Group 4 (n = 33, propofol 2 mg/kg mixed with lidocaine 1 mg/kg followed by normal saline 0.06 ml/kg) and Group 5 (n = 61, propofol 2 mg/kg mixed with lidocaine 1 mg/kg followed by fentanyl 3ng/kg). All patients were injected with fentanyl or normal saline two minutes after administration of propofol premixed with lidocaine or normal saline, respectively. We checked the cough reflex, injection pain, oxygen desaturation and chest wall rigidity. RESULTS: There was a significant difference in the incidence of cough reflex between group 1 and 3 or 5. The incidience of group 5 was significantly lower than in group 3. CONCLUSIONS: This study suggests that a propofol-lidocaine mixture should be considered when patients require bronchodilation during induction of anesthesia.

Morphine Protects Peroxynitrite-induced Cell Death in Primary Rat Neonatal Astrocytes / 대한마취과학회지

BACKGROUND: Astrocytes, representing a major non-neuronal cell population in the central nervous system (CNS), contain opioid receptors and are actively involved in several brain functions. This study is designed to evaluate the effects by which morphine contributes to cytotoxicity of nitric oxide (NO) species including NO and peroxynitrite (ONOO(-)) in primary astrocytes isolated from the cerebral cortexes of 1 - 2 day Sprague-Dawley rats. METHODS: The cultured cells were pretreated with morphine and exposed to 3-morpholinosydnonimine (SIN-1) which simultaneously generates NO and superoxide, thus possibly forming peroxynitrite. The cell damage was assessed by using an MTT (methylthizol-2-yl-2, 5-diphenyl, tetrazolium bromide) assay. Morphological nuclear changes of the cells after exposure to SIN-1 for 24 hours was evaluated by using 4', 6-diamidino-2-phenylindole (DAPI) staining. RESULTS: Morphine significantly protected primary rat astrocytes in a dose-dependent manner from the death mediated by sodium nitroprusside (SNP), a donor of nitric oxide, and SIN-1. Moreover, it was found that naloxone antagonized the protective effect of morphine on SIN-1-induced cell death, revealed as apoptosis by the occurrence of morphological nuclear changes characteristic of apoptosis. Morphine also inhibited the nuclear condensation of SIN-1-treated cells, however the action of morphine was antagonized by pretreatment of naloxone. The protective role of morphine on SIN-1-induced cytotoxicity was inhibited by DL-Buthionine-[S, R]-sulfoximine (BSO). Furthermore, the effects of morphine on SIN-1-induced cytotoxicity were blocked by pretreatment of Gi protein inhibitor, pertussis toxin, and phosphoinositide 3-kinase (PI3 kinase) inhibitors, Wortmannin and LY294002. CONCLUSIONS: These results suggest that morphine may protect primary rat astrocytes from NO species via the signaling cascades involving G-protein and PI3-kinase, and possibly regulates the anti-oxidant, glutathione (GSH).

Effects of Morphine on Free Radical-induced Apoptosis of Human Neuroblastoma SH-SY5Y Cells / 대한마취과학회지

BACKGROUND: The effect of opioids on nitric oxide (NO)- and peroxynitrite-induced neuronal cell death is largely unknown. In the present study, we examined the effect of morphine on NO- and peroxynitrite-induced cell death using a human neuroblastoma SH-SY5Y cell line, which abundantly expresses micro, delta, kappa-opioid receptors. METHODS: The cultured cells were pretreated with morphine and exposed to 3-morpholinosydnonimine (SIN-1) that simultaneously generates NO and superoxide, thus possibly forming peroxynitrite. The cell damage was assessed by using MTT assay and crystal violet staining. Morphological nuclear changes and enzymatic evidences of apoptosis of the cells after exposure to SIN-1 for 24 hours were evaluated by using 4', 6-diamidino-2-phenylindole (DAPI) staining and the measurement of pro-apoptotic protease (caspase-3) activity, respectively. Levels of reduced glutathion (GSH) were measured by monochloronimane (MCB) assay. RESULTS: Pretreatment of SH-SY5Y with morphine significantly inhibited the apoptotic cell death. Morphine also inhibited SIN-1-induced caspase-3 (pro-apoptotic protease) activity in a dose-dependent manner. However, naloxone (20 microM) could not antagonize completely the effect of morphine in SIN- 1-induced cell death. Pre-administered GSH and N-acetylcysteine (NAC) have been found to protect SIN-induced apoptosis, and the neuroblastoma cells treated with morphine had significantly elevated the levels of GSH. CONCLUSIONS: The present study shows that morphine protects the human neuroblastoma cell line SH- SY5Y from peroxynitrite-induced apoptotic cell death through elevated GSH levels. The protective actionof morphine seems to be associated with inhibition of the apoptotic pathway. However, it is suggested that morphine protects the cells possibly via other unknown mechanisms in addition to the activation of opioid receptors.

Receptor Activation is Not the Main Rescue Mechanism of Morphine in Peroxynitrite-Induced Death of Human Neuroblastoma SH-SY5Y Cells / 대한마취과학회지

BACKGROUND: In the present study, we examined the effect of morphine on NO- and peroxynitrite-induced cell death using a human neuroblastoma SH-SY5Y cell line which abundantly expresses micro, delta and K-opioid receptors. METHODS: The cultured cells were pretreated with morphine (100 micrometer) and exposed to 3-morpholinosydnonimine (SIN-1, 1mM). Agarose gel electrophoresis of DNA was done with the extracts from SH-SY5Y cells. The cells were treated with selective ligands for opioid receptor subtypes and with PI3-kinase inhibitors. Cell damage was assessed by using an MTT assay. Spectrophotometric absorption spectra were measured from the mixture of morphine (100 micrometer) plus peroxynitrite (1 mM) at room temperature. RESULTS: SIN-1 treated cells showed the occurrence of a specific form of chromosomal DNA fragmentation which pretreatment with morphine inhibited. The selective ligands for opioid receptor subtypes, [D-Ala2, N-Me-Phe4, Gly-ol5]enkephalin (DAMGO, micro-opioid receptor agonist), [D-Pen2,5] enkephalin (DPDPE, delta-opioid receptor agonist) and U-69593 (K-opioid receptor agonist) at a concentration of 10 micrometer did not prevent the cell death induced by SIN-1. Naloxone (20 micrometer) hardly antagonized the effect of morphine in SIN-1-induced cell death. The PI3-kinase inhibitors Wortmannin and LY294002 did not inhibit the action of morphine on apoptotic cell death. In the measurements of spectrophotometric absorption spectra, the peak of the absorbance of the mixture of morphine plus peroxynitrite at 295 300 nm disappeared three minutes after mixing. CONCLUSIONS: The present study showed that morphine protected the human neuroblastoma cell line,SH-SY5Y, from peroxynitrite-induced apoptotic cell death. However, it is suggested that the protective action of morphine is not via the activation of opioid receptors and/or the PI3-kinase pathway but possibly via direct chemical reaction.

Effects of Verapamil Combined with Esmolol on Blood Pressure and Heart Rates during Tracheal Intubation / 대한마취과학회지

BACKGROUND: Antihypertensive agents such as verapamil and esmolol are well known for their effects of hemodynamic stabilization on tracheal intubation. However, our previous study, Verapamil and esmolol did not attenuate heart rate and blood pressure. The aim of the present study was to evaluate the efficacy of combined administration of these drugs for controlling hemodynamic responses to tracheal intubation. METHODS: Forty-eight patients, ASA physical status I or II, were randomly assigned to one of four groups (n = 12 each):normal saline (control), verapamil 0.1 mg/kg, esmolol 1 mg/kg, and verapamil 0.05 mg/kg mixed with esmolol 0.5 mg/kg. Anesthesia was induced with thiopental 5 mg/kg intravenously, and then saline, verapamil, esmolol or the mixed drugs were administered as an intravenous bolus, and immediately followed by succinylcholine 1.5 mg/kg. Tracheal intubation was performed 90 s after intravenous injection of experimental drugs. Systolic and diastolic blood pressure and heart rate were measured before induction and every minute for 5 minutes after tracheal intubation. RESULTS: There was a significant attenuation in systolic blood pressure after tracheal intubation in the verapamil and mixed groups compared to the control and esmolol groups. Heart rates were significantly lower in the esmolol and mixed groups than in the verapamil groups after tracheal intubation. CONCLUSIONS: Combined administration of Verapamil 0.05 mg/kg with esmolol 0.5 mg/kg attenuated increases in blood pressure and heart rate after tracheal intubation.

Comparison of Verapamil and Esmolol for Controlling the Blood Pressure and Heart Rate to Tracheal Intubation According to the Different Anesthetic Induction Agents / 대한마취과학회지

BACKGROUND: Antihypertensive agents such as verapamil and esmolol are well known for their effects of hemodynamic stabilization on tracheal intubation. But hemodynamic discrepancies in these agents may result from different techniques of anesthetic induction. The aim of the present study was to compare and evaluate their efficacy in controlling hemodynamic responses to tracheal intubation under the different anesthetic induction agents. METHODS: Seventy-two patients, ASA physical status I or II, were randomly assigned to one of six groups (n = 12 each): a Thiopental-Saline (T-S) group and a Propofol-Saline (P-S) group in saline 10 ml; a Thiopental-Verapamil (T-V) group and a Propofol-Verapamil (P-V) group in verapamil 0.1 mg/kg; a Thiopental-Esmolol (T-E) group and a Propofol-Esmolol (P-E) group in esmolol 1 mg/kg according to the induction agents, thiopental or propofol. Anesthesia was induced with thiopental 5 mg/kg or propofol 2 mg/kg intravenous, respectively. Next, saline, verapamil and esmolol were administered as a bolus, and were immediately followed by succinylcholine 1.5 mg/kg. Tracheal intubation was carried out 60 s and 90 s after the intravenous injections of verapamil and esmolol, respectively. Systolic and diastolic blood pressure and heart rate were measured before induction and every minute for 5 minutes after tracheal intubation. RESULTS: There was a significant attenuation in systolic and diastolic arterial pressure after tracheal intubation in the verapamil groups compared to the esmolol groups. Heart rates were significantly lower in the esmolol groups than in the verapamil groups after tracheal intubation. CONCLUSIONS: Verapamil 0.1 mg/kg and esmolol 1 mg/kg attenuated increases in blood pressure and heart rate after tracheal intubation. The different anesthetic induction agents did not influence the hemodynamic effects of verapamil and esmolol on tracheal intubation.

Comparison of Verapamil and Esmolol for Controlling the Blood Pressure and Heart Rate to Tracheal Intubation According to the Different Anesthetic Induction Agents / 대한마취과학회지

BACKGROUND: Antihypertensive agents such as verapamil and esmolol are well known for their effects of hemodynamic stabilization on tracheal intubation. But hemodynamic discrepancies in these agents may result from different techniques of anesthetic induction. The aim of the present study was to compare and evaluate their efficacy in controlling hemodynamic responses to tracheal intubation under the different anesthetic induction agents. METHODS: Seventy-two patients, ASA physical status I or II, were randomly assigned to one of six groups (n = 12 each): a Thiopental-Saline (T-S) group and a Propofol-Saline (P-S) group in saline 10 ml; a Thiopental-Verapamil (T-V) group and a Propofol-Verapamil (P-V) group in verapamil 0.1 mg/kg; a Thiopental-Esmolol (T-E) group and a Propofol-Esmolol (P-E) group in esmolol 1 mg/kg according to the induction agents, thiopental or propofol. Anesthesia was induced with thiopental 5 mg/kg or propofol 2 mg/kg intravenous, respectively. Next, saline, verapamil and esmolol were administered as a bolus, and were immediately followed by succinylcholine 1.5 mg/kg. Tracheal intubation was carried out 60 s and 90 s after the intravenous injections of verapamil and esmolol, respectively. Systolic and diastolic blood pressure and heart rate were measured before induction and every minute for 5 minutes after tracheal intubation. RESULTS: There was a significant attenuation in systolic and diastolic arterial pressure after tracheal intubation in the verapamil groups compared to the esmolol groups. Heart rates were significantly lower in the esmolol groups than in the verapamil groups after tracheal intubation. CONCLUSIONS: Verapamil 0.1 mg/kg and esmolol 1 mg/kg attenuated increases in blood pressure and heart rate after tracheal intubation. The different anesthetic induction agents did not influence the hemodynamic effects of verapamil and esmolol on tracheal intubation.

Influence of Contrast Media on Alcoholic Sympathectomy / 대한마취과학회지

BACKGROUND: There have been unexpected cases of failed alcoholic sympathectomy, even though satisfactory effects had been obtained in test blocks with a mixture of contrast media and local anesthetics. It was plausible to suspect the contrast media as a cause of the failure of alcoholic sympathectomy. So, the purpose of this study was to evaluate whether the contrast media can hinder the action of alcohol in alcoholic sympathectomy or not. METHODS: In Sprague - Dawley rats (200 300g), thoracic paravertebral sympathetic chains were exposed and planned regimens were injected in these regions. The rats were divided randomly into seven groups, group C (control group), group D (administration of dye just after exposure), group D-A30 (administration of dye just after exposure, administration of alcohol 30 min. after dye), group A30 (administration of alcohol 30 min. after exposure), group D-A0 (administration of dye just after exposure, administration of alcohol just after dye), group D-A60 (administration of dye just after exposure, administration of alcohol 60 min. after dye) and group D-A90 (administration of dye just after exposure, administration of alcohol 90 min. after dye). Degrees of cytoplasmic contraction were evaluated in the ganglion cells of each member of the experimental groups. RESULTS: The contraction ratios of cytoplasms in group D-A30 and A30 were greater than that of group C and D. The contraction ratios of cytoplasm in group D-A60 and D-A90 were greater than those of group D-A0 and D-A30. CONCLUSIONS: According to our results, the contrast media seems to hinder the action of alcohol in alcoholic sympathectomy.

The Risk of Aspiration in Laryngeal Mask Airway: Laryngeal Mask Airway vs Endotracheal Tube

BACKGROUND: There were several studies for the incidence of gastroesophageal reflux associated with the laryngeal mask airway(LMA), but the results of those studies were much different much different from one another. The aim of this study was to compare the incidence of gastroesophageal reflux and regurgitation of gastric contents between the LMA and the endotracheal tube(ETT). METHOD: Ninety patients scheduled for elective orthopedic surgery with a standardized general anesthetic technique were randomly allocated to receive either a LMA(n-49) or a ETT(n=41) for airway management. The esophageal manometry was carried out for the exclusion of esophageal motility disorders and the 24-hour ambulatory pH metry was done from one day before the operation. A methylene blue(50mg) capsule was swallowed just before the induction and the simultaneous recordings of pH were maintained during anesthesia. At the end of anesthesia, the episodes of regurgitation of gastric contents above hypopharynx were analyzed by the pharyngeal blue staining and the pH metric data were analyzed for the detection of gastroesophageal relux episodes during anesthesia. RESULTS: There was no significant difference in the incidence of gastroesophageal relux(pH< or =4) between two groups; only two patients in LMA and three patients in ETT had reflux episodes during the removal or arousal phase. There was no episode of the pharyngeal blue staining in both group. All of the gastroesophageal reflux patients in both group developed a cough or straining during those phases. There was no clinical evidence of aspiration of gastric contents in both group. CONCLUSION: In comparison with ETT, use of LMA does not appear to increase the incidence of gastroesophageal reflux and regurgitation above hypophryngeal level in positive pressure ventilating patients during long surgical procedures. Therefore, the risk of aspiration in LMA will not be much more than ETT.

Is Palmar Skin Temperature a Indicator for the Success of Thoracic Sympathectomy in Hyperhidrosis Patients? / 대한마취과학회지

BACKGREOUND: The sympathetic investigations during thoracic sympathectomy are essential to an adequate sympathectomy that will lead to sufficient and lasting relief of palmar hyperhidrosis. The measurement of palmar skin temperature has been used as an indicator of success of transcutaneous chemical thoracic sympathectomy. We measured intraoperative palmar skin temperature to know whether it can be used as a same purpose in the endoscopic thoracic sympathectomy under general anesthsia. METHODS: Fifteen patients (18 to 25 years old) with palmar hyperhidrosis underwent endoscopic thoracic sympathectomy under general anesthesia. The palmar skin temperature was measured with a skin probe of a thermometer applied on the both index finger tips. The palmar skin temperature was monitored continuously from the beginning of anesthesia to the complete arousal. RESULTS: The palmar skin temperature increased significantly by about 3 degrees C just after induction. There was no significant difference in the palmar skin temperature between just before sympathectomy and soon after sympathectomy during the endoscopic thoracic sympathectomy. CONCLUSIONS: Intraoperative measurement of palmar skin temperature can not indicate a definite sympathectic denervation during the endoscopic thoracic sympathectomy under general anesthesia.

The Suitable Time for the Removal of Laryngeal Mask Airway / 대한마취과학회지

BACKGROUND: There were several studies for the incidence of gastroesophageal reflux associated with the laryngeal mask airway (LMA), but the results of those studies were much different from one another. This conflicting results may be due to the time of the removal of LMA, which has been usually after the arousal (when the patient can open the mouth on command). So, the authors investigated the incidence of the gastroesophageal reflux and the regurgitation of gastric contents above the upper esophageal sphincter associated with the difference of the time of the removal of LMA. METHODS: Sixty three patients scheduled for elective orthopedic surgery with a standardized general anesthetic technique were allocated randomly to Group A (n=34, LMA was removed when the rejection signs such as struggle, restlessness, swallowing and cough came out.) or Group B (n=29, LMA was removed after arousal). For the detection of reflux and regurgitation episodes during anesthesia, a pH monitoring probe was positioned in the lower esophagus and a methylene blue (50 mg) gelatine capsule was swallowed just before induction. At the end of anesthesia, the episodes of reflux and regurgitation of gastric contents were analyzed according to the pharyngeal blue staining or pH< or = 4. RESULTS: The incidence of reflux (pH< or = 4) from the time of the rejection signs to the removal of LMA and the total incidence of reflux in Group B were significantly higher than that of Group A. No patient in both group showed pharyngeal staining of methylene blue. There was no clinical evidence of aspiration of gastric contents in either group. CONCLUSION: Maintenance of LMA until the patient can open the mouth on command seems to increase the incidence of the gastroesophageal reflux.

The Incidence of Regurgitation above Upper Esophageal Sphincter: Laryngeal Mask Airway vs Endotracheal Tube / 대한마취과학회지

BACKGROUND: From a clinical perspective, the regurgitation of the gastric contents above the upper esophageal sphincter has greater clinical relevance than gastroesophageal reflux. The authors investigated the incidence of regurgitation of gastric contents above the upper esophageal sphincter associated with the laryngeal mask airway(LMA) and the endotracheal tube(ETT) by methylene blue(50mg) gelatine capsule and pH probe in positive pressure ventilated patients during long surgical procedures . METHODS: Sixty patients scheduled for elective orthopedic surgery with a standardized general anesthetic technique were randomly allocated to receive either a LMA(n=34) or a ETT(n=26) for airway management. For the detection of regurgitation episodes during anesthesia, a pH monitoring probe was positioned in the hypopharynx 30 minutes before induction and a methylene blue capsule was swallowed just before induction. At the end of anesthesia, the episodes of regurgitation of gastric contents above upper esophageal sphincter were analyzed according to the pharyngeal blue staining or pH< or =4. RESULTS: There were no episodes of regurgitation of gastric contents(pH< or =4 or/and methylene blue staining) above the upper esophageal sphincter detected during the course of measurement. There was no clinical evidence of aspiration in either group. CONCLUSIONS: In comparison with ETT, the use of LMA does not appear to result in increased incidence of regurgitation of gastric contents above upper esophageal sphincter in positive pressure ventilated patients during long surgical procedures.

The Incidence of Gastroesophageal Reflux: Laryngeal Mask Airway vs Endotracheal Tube / 대한마취과학회지

BACKGROUND: There were several studies for the incidence of gastroesophageal reflux associated with the laryngeal mask airway(LMA), but the results of those studies were much different from one another. The authors of this study measured the intraesophageal pH at 5cm above lower esophageal sphincter(LES) to compare the incidence of gastroesophageal reflux associated with the LMA and the endotracheal tube(ETT) in positive pressure ventilated patients during long surgical procedures. METHOD: Ninety patients scheduled for elective orthopedic surgery with a standardized general anesthetic technique were randomly allocated to receive either a LMA(n=49) or a ETT(n=41) for airway management. The esophageal manometry was carried out for the exclusion of esophageal motility disorders and a probe with a pH electrode was passed nasally into the esophagus and positioned at 5 cm above LES one day before the operation. After that, recordings of pH for the diagnosis of gastroesophageal reflux disorder and for the detection of reflux episodes during and immediate after anesthesia were performed. RESULTS: There was no significant difference in the incidence of reflux(pH< or =4) between groups; only two patients in LMA and three patients in ETT had reflux episodes in the removal or arousal phase. All of them had experiences such as a coughing or straining during those phases. There was no clinical evidence of aspiration of gastric contents in either group. CONCLUSION: In comparison with ETT, use of LMA does not appear to result in increased incidence of reflux in positive pressure ventilated patients during long surgical procedures.

Tracheal Tube Cuff Inflation in Oropharynx : An Useful Method in Blind Nasotracheal Intubation / 대한마취과학회지

We designed a study to determine if the tracheal tube cuff inflation in the oropharynx improves the success rate of blind nasotracheal intubation in normal, paralyzed patients because of lacking of controlled study about it. In prospective, randomized fashion, 100 ASA I or II patients undergoing elective oral surgery were studied. The trachea was intubated once keeping the tracheal tube cuff deflated throughout the maneuver and once using the technique of tracheal tube cuff inflation in the oropbarynx. A maximum of two attempts was allowed for each technique. If the first attempt was failed, the second attempt was tried with an addition of application of thyroid cartilage compression in each technique. Witb the tracheal tube cuff inflated, the success rate was significantly higher than the cuff-deflated technique(p<0.05). A application of thyroid cartilage compression increased the success rate of the blind nasotracheal intubation in each technique, but it was more useful in the cuff inflation technique(p<0.05). Time taken to intubate the trachea was longer in the cuff inflation technique. We suggest that, in normal paralyzed patients, the tracheal tube cuff inflation in the oropharynx increases the success rate of blind nasotracheal intubation.

Subcutaneous Emphysema During Laparoscopic Cholecystectomy in Difficultly Intubated Patient / 대한마취과학회지

Subcutaneous emphysema can occur as the result of trauma, surgical procedure and anesthetic complication. As increasing numbers of laparoscopic procedures are performed, increasing numbers of complications directly related to laparoscopy will occur. A case is presented of subcutaneous emphysema without pneumothorax or pneumomediastinum during laparoscopic cholecystectomy in difficultly intubated patient. The cause is suspected of inadvertent subcutaneous insufflation of carbon dioxide during the initial Verres needle puncture for the establishment of pneumoperitoneum. Etiology and evaluation of subcutaneous emphysema possibly associated with this case are reviewed.