Management of thoracogastric airway fistula after esophagectomy for esophageal cancer: A systematic literature review.

BACKGROUND: Thoracogastric airway fistula (TGAF) is a serious complication of esophagectomy for esophageal cancer. We conducted a systematic review of the appropriate therapeutic options for acquired TGAF. METHODS: We performed a literature search to identify relevant studies from PubMed, EMBASE, and Web of Science using the search terms "gastric airway fistula", "gastrotracheal fistula", "gastrobronchial fistula", "tracheogastric fistula", "bronchogastric fistula", "esophageal cancer", and "esophagectomy". RESULT: Twenty-four studies (89 patients) were selected for analysis. Cough was the main clinical presentation of TGAF. The main bronchus was the most common place for fistulas (53/89), and 29 fistulas occurred in the trachea. Almost 73% (65/89) of patients underwent non-surgical treatment of whom 87.7% (57/65) received initial fistula closure. Twenty-three patients underwent surgery, including 19 (82.6%) with initial closure. The 1-, 2-, 3-, 6-, and 9-month survival rates in patients who underwent surgical repair were 95.65%, 95.65%, 82.61%, 72.73%, and 38.10%, respectively, and the equivalent survival rates in patients with tracheal stent placement were 91.67%, 86.67%, 71.67%, 36.96%, and 13.33%, respectively. CONCLUSION: TGAF should be suspected in patients with persistent cough, especially in a recumbent position or associated with food intake. Individualized treatment should be emphasized based on the general condition of each patient.

Application of combined-type Y-shaped covered metallic stents for the treatment of gastrotracheal fistulas and gastrobronchial fistulas.

OBJECTIVE: To determine the safety and feasibility of combined-type integrated Y-shaped self-expanding covered metallic stents to treat gastrotracheal fistulas (GTFs) and gastrobronchial fistulas (GBFs). METHODS: We retrospectively reviewed the data of 10 patients with postoperative GTFs or GBFs. Depending on the size and location of the fistula and the airway diameter, we custom-designed 2 or 3 stents for each patient. The combined-type stents consisted of a large and a small Y-shaped stent. Under fluoroscopic guidance, the small stent was inserted into the distal part of the involved airway. Then, the large stent was placed at the trachea and carina. The large stent partly overlapped the main body of the small stent. RESULTS: All stents were successfully inserted at the first attempt. Esophageal and airway radiography showed no contrast agent leakage, indicating that the fistula was fully sealed. After the procedure, the patients could resume eating without coughing, and their quality of life improved. Each patient was fully followed up. Six patients died at 3.2 to 8 months of tumors (4 patients), hemoptysis (1 patient), or pulmonary infection (1 patient). In 1 patient, the carinal fistula enlarged 4 months after stenting, and another small Y-shaped stent was inserted to seal the fistula. This patient and the remaining 3 patients are still alive. CONCLUSIONS: Deployment of the combined-type Y-shaped integrated self-expanding covered metallic stent proved to be an effective, safe, and minimally invasive procedure for complex GTFs and GBFs. Our patients tolerated the stents well and had good palliation of their symptoms.

Esophageal bypass using a gastric tube and a cardiostomy for malignant esophagorespiratory fistula.

Esophageal bypass with a gastric tube and a cardiostomy is a method recently devised for malignant esophagorespiratory fistula. This method separates completely the alimentary and respiratory tracts. Four patients underwent these procedures. No operative deaths occurred, nor was there any anastomotic leakage or disruption of the excluded esophagus. The average survival time was 7 months. However, all patients were allowed to consume food orally up to the last moment of life. This bypass procedure is simple and safe to perform, and is thus a feasible treatment choice for patients with such fistulas.

Evolving strategies for the treatment of aortoenteric fistulas.

BACKGROUND: Aortoenteric fistulas (AEFs) are a rare but often fatal cause of gastrointestinal bleeding. Operative repair of AEF has been historically associated with extremely high morbidity and mortality. We reviewed our experience of open surgical and endovascular treatment of AEF to compare outcomes over a contemporaneous time period. METHODS: Over a 9-year period between January 1997 and January 2006, 16 patients (11 men and 5 women) were diagnosed with and treated for AEFs. Seven patients underwent open surgical repair, and nine, with anatomically suitable lesions, underwent endovascular repair. The outcome after treatment of these patients was investigated for survival, perioperative complications, length of hospital stay, and long-term disposition. RESULTS: Three primary and 13 secondary AEFs were treated. The mean time from the initial aortic operation until AEF diagnosis was 5.9 years (range, 0.7-12.2 years) for patients with secondary AEFs. The overall 30-day mortality rate was 18.8%. One intraoperative death and one in-hospital death secondary to multisystem organ failure occurred in patients undergoing open repair. One in-hospital death related to persistent sepsis occurred in the endovascular group. The overall perioperative complication rate was 50.0%. Complications in the open group included sepsis, renal failure, bowel obstruction, and pancreatitis. Complications in the endovascular group were related to persistent sepsis. The mean in-hospital length of stay was significantly longer for patients undergoing open repair compared with endovascular repair (44.0 vs 19.4 days; P = .04). Four (80%) of five patients who were discharged from the hospital in the open group were placed in skilled nursing facilities, and seven (87.5%) of eight patients discharged in the endovascular group returned home. The median overall survival after hospital discharge was 23.1 months. There were no late aneurysm-related deaths or late deaths related to septic complications. CONCLUSIONS: Patients with AEFs have limited overall survival. Endovascular therapy offers an alternative to open surgical repair, seems to be associated with decreased perioperative morbidity and mortality and a shorter in-hospital stay, and allows for acceptable survival given the presence of coexisting medical comorbidities. Furthermore, endovascular repair provides a therapeutic option to control bleeding and allow for continued intervention in a stabilized setting.

[Conservative and surgical treatment of esophago-gastric anastomotic leaks]. / Trattamento delle fistole dell'anastomosi esofago-gastrica.

OBJECTIVE: To evaluate the results of conservative and surgical management of esophago-gastric anastomotic leaks after esophagectomy for carcinoma. MATERIALS AND METHODS: A retrospective analysis of 510 patients subjected to esophagectomy and gastric pull-up with intra-thoracic or cervical anastomosis was performed. RESULTS: Twenty four cases (6.1%) of intra-thoracic anastomotic leaks and 17 (13.9%) cervical leaks were observed and treated. The conservative treatment was adopted in 19 intra-thoracic leakages (79%) and in 10 cervical leakages (59%). The leak-related mortality rate was 16.6% in patients with intra-thoracic leaks and 11.7% in those with cervical leaks. DISCUSSION: The introduction of staplers has dramatically decreased, but not eliminated, the risk of intra-thoracic and cervical anastomotic leaks. In our series the choice of the therapeutic approach was based on clinical and endoscopic findings. Patients with anastomotic dehiscence and gastric graft ischemia required reoperation, whereas conservative treatment was possible in the majority of cases. CONCLUSION: The treatment of esophago-gastric anastomotic leaks must be tailored to the individual patient. Early endoscopy is crucial for recognition of ischemia of the transposed stomach.

Fístulas gastroenterocutáneas posoperatorias: factores que influyen en la mortalidad / Postoperative gastroenterocutaneous fistulas: factors influencing on mortality

La mortalidad en las fístulas gastrointestinales externas posoperatorias ha sido relacionada con varios factores entre los que sobresalen la edad del paciente, el flujo, la localización, el número, la presencia o no de sepsis asociada y la malnutrición. El estudio de estas variables en 110 pacientes con tales fístulas demostró al emplear el modelo de regresión logística, que la posibilidad de muerte fue mayor en los enfermos que presentaron sepsis (p= 0,001), en los que tuvieron un flujo alto (p-0,016) y que aumentó con la edad (p= 0,016). La localización en el yeyuno estuvo cerca de la significación (p= 0,097)(AU)

The mortality in the postoperative external gastrointestinal fistulas has been related to some factors among which the age of the patient, the flow, the localization, the number, the presence or not of associated sepsis and malnutrition stand out. The study of these variables in 110 patients with such fistulas showed by using the logistic regression model that death possibility was higher in the patients that presented sepsis (p = 0.001), in those that had a high flow (p = 0.016), and that it increased with age (p = 0.016). The localization in the jejunum was close to significance (p = 0.097)(AU)

Fístulas gastroenterocutáneas posoperatorias: factores que influyen en la mortalidad / Postoperative gastroenterocutaneous fistulas: factors influencing on mortality

La mortalidad en las fístulas gastrointestinales externas posoperatorias ha sido relacionada con varios factores entre los que sobresalen la edad del paciente, el flujo, la localización, el número, la presencia o no de sepsis asociada y la malnutrición. El estudio de estas variables en 110 pacientes con tales fístulas demostró al emplear el modelo de regresión logística, que la posibilidad de muerte fue mayor en los enfermos que presentaron sepsis (p= 0,001), en los que tuvieron un flujo alto (p-0,016) y que aumentó con la edad (p= 0,016). La localización en el yeyuno estuvo cerca de la significación (p= 0,097(AU)

Fístula enterocutánea: revisión de casos clínicos, Hospital Escuela Antonio Lenín Fonseca, enero de 1997 a diciembre del 20001 / Enterocutaneous fistula a review fo clinical cases, Hospital Escuela Antonio Lenín Fonseca, January of 1997 to december of 2000

Las fístulas enterocutáneas son comunicaciones anormales entre dos órganos huecos y la piel, se clasifican como congénitas y adquiridas, éstas últimas más frecuentes (75-85 porciento). No importa el origen de las fístulas, sino, el marcado desequilibrio hidroelectrólitico que éstos pacientes desarrollan, la malnutrición y la sépsis que son las causa más común de muerte. Con la alimentación parenteral según la literatura, la mortalidad se redujo del 30-50 porciento hasta el 5-10 porciento algunos estudios refieren, junto con la antibioticoterapia y reanimación hidroelectrolitica. En el presente estudio se revisaron los expedientes clínicos de pacientes con diagnósticos de fístulas enterocutáneas en el período de enero de 1997 a diciembre del 2000; encontrando un total de 27 pacientes, quienes permanecieron en promedio de 87 días intrahospitalario (14-160 días) el rango de edad de 31 a 40 años fue el más frecuente predominando el sexo masculino en un relación de 3:1 sobre el sexo femenino, la causa principal del desarrollo de fístula fue el postquirúrgico de causa benigna predominando el esófago y el yeyuno con fístula de bajo gasto primordialmente, lo que se diagnóstico básicamente proclínica; se le realizó tratamiento conservador al 51.85 porciento de los pacientes con medidas generales y sólo a 4 pacientes se les administró alimentación enteral y a 9 alimentación parenteral, la cual fue en forma inocorrecta e inrregular por razones económicas y una minima cantidad de 3 pacientes se les administró somotostatina en dosis suficiente. Las cirugías realizadas fueron resección-anastomosis y derivaciones basicamente. Las complicaciones que se presentaron fueron la D.P.C, Sépsis, D.H.E y abscesos intraabdominales. Fallecieron 9 pacientes lo que equivale a una letalidad de 33.33 porciento cifra que internacionalmente ha descendido con la implementación de la alimentación parenteral sistémica de los pacientes con fístulas enterocutáneas. Por lo que recordamos que se implemente en el cuadro básico de medicamentos del hospital la alimentación parenteral total ya que la base del manejo de los mismo es reducir al mínimo el contenido gastrointestinal y permite el cierre de la fístula sin el deterioro de su etado nutricional y el riesgo de muerte...

[Clinical variants and treatment of gastrointestinal fistulas]. / Klinicheskie varianty svishchei zheludochno-kishechnogo trakta i ikh lechenie.

The experience of 411 patients treatment, aged from 15 to 78 years with gastrointestinal tract fistulas are summarized. Depending on clinico-anatomical picture, fistulas are divided in 5 types. There were 110 (26.8%) patients with fistula type I, 36 (8.7%)--type II, 70 (17.03%)--type III, 29 (7.5%)--type IV, 66 (40.4%)--type V. Treatment policy was developed for each group. Necessity of urgent relaparotomy in patients with fistula type I, early relaparotomy in fistula type II, late relaparotomy and elective operations in fistula types III, IV and V were substantiated. At usage of this treatment 102 (24.8%) from 411 patients died.

[Postoperative fistulas after gastrectomy: risk factors in relation to incidence and mortality]. / Fistole postoperatorie dopo gastrectomia: fattori di rischio in relazione ad incidenza e mortalità.

The relations between incidence and prognosis of postoperative fistulas after gastrectomy and some different variables were analysed in the present retrospective study. Thirteen digestive fistulas of 113 patients (11.9%) submitted to gastrectomy during the period 1989-1994 represent the study population. The incidence of postoperative fistulas was compared to the kind of gastric pathology, to the extension of gastrectomy, to different nutritional (serum haemoglobin, albumin and transferrin level, weight loss) and immunological factors (serum lymphocytes) and, for oncological patients, to the stage of the disease. Incidence was directly related to the extension of gastrectomy, to serum albumin and haemoglobin level, and to weight loss rate. The results were not statistically significant at Kruskal-Wallis and ANOVA tests. No relation was found between incidence of fistulas and serum transferrin level, number of lymphocytes and adoption of early postoperative enteral nutrition. Six patients had spontaneous closure of the fistula with conservative therapy. Seven patients required reoperation because of abdominal sepsis (53.8%). Three patients died (23%). Although spontaneous closure, reoperation and mortality were related to nutritional and immunological state, no examined variables showed a statistically significative relation. The adoption of early postoperative enteral nutrition was not related to the prognosis, unlike the stage of the disease: patients submitted to reoperation had a TNM III or IV stage; dead patients had a TNM IV stage. Treatment of metabolic-nutritional unbalance can prevent anastomotic failure and fistula after gastrectomy and improve the prognosis. The relation between early postoperative enteral nutrition and incidence and prognosis of postoperative fistulas remains unclear.

Nuevo enfoque en el tratamiento de las fístulas enterocutáneas postquirúrgicas / New approach in the treatment of the postoperative enterocutaneous fistulas

Entre 1985 y 1990 se trataron 14 pacientes con 27 fístulas enterocutáneas postcirugía, mediante un sistema original por vacío y compactación(SIVACO). Se basa en el uso de muy bajas presiones atmosféricas, que compacta una masa de fibras poliméricas(TFP) sobre el orificio, ocluyéndolo como una tapa o "pared dique". El sesgo grave de la población está dado por el alto caudal promedio de las fístulas (1500cc/día), una mortalidad esperada del 43% por APACHE II y por ser 7 pacientes con supuraciones peritoneales, 8 con desnutrición severa, 6 con m160s de una fístula y 12 con signos claros de sepsis. Los resultados fueron: el caudal cayó a 67cc/día a las 24 hs. y 0cc/día a los siete días. Este método resolvió las colecciones intraperitoneales sin punciones o cirugía. Siete de los ocho pacientes desnutridos recuperaron más del 55% del peso perdido a los 20 días. De las 27 fístulas tratadas 22 cerraron con este procedimiento y 4 con cirugía. El 93% de los pacientes se alimentaba por vía enteral, deambulaba y se encontraba sin vía venosa central a los 9 días de tratamiento. El tiempo de tratamiento fue de 14 a 365 días. Once enfermos curaron las fístulas entre 14 y 44 días, 2 con fístulas múltiples, algunas de ellas cerradas antes de los 90 días y que se reoperaron al año de las fístulas persistentes, con buen estado general y alta a los 15 y 20 días sin complicaciones. Trece pacientes fueron dados de alta curados. Uno falleció por bronconeumonía. La mortalidad del método fue 0

Nuevo enfoque en el tratamiento de las fístulas enterocutáneas postquirúrgicas / New approach in the treatment of the postoperative enterocutaneous fistulas

Entre 1985 y 1990 se trataron 14 pacientes con 27 fístulas enterocutáneas postcirugía, mediante un sistema original por vacío y compactación(SIVACO). Se basa en el uso de muy bajas presiones atmosféricas, que compacta una masa de fibras poliméricas(TFP) sobre el orificio, ocluyéndolo como una tapa o "pared dique". El sesgo grave de la población está dado por el alto caudal promedio de las fístulas (1500cc/día), una mortalidad esperada del 43% por APACHE II y por ser 7 pacientes con supuraciones peritoneales, 8 con desnutrición severa, 6 con m160s de una fístula y 12 con signos claros de sepsis. Los resultados fueron: el caudal cayó a 67cc/día a las 24 hs. y 0cc/día a los siete días. Este método resolvió las colecciones intraperitoneales sin punciones o cirugía. Siete de los ocho pacientes desnutridos recuperaron más del 55% del peso perdido a los 20 días. De las 27 fístulas tratadas 22 cerraron con este procedimiento y 4 con cirugía. El 93% de los pacientes se alimentaba por vía enteral, deambulaba y se encontraba sin vía venosa central a los 9 días de tratamiento. El tiempo de tratamiento fue de 14 a 365 días. Once enfermos curaron las fístulas entre 14 y 44 días, 2 con fístulas múltiples, algunas de ellas cerradas antes de los 90 días y que se reoperaron al año de las fístulas persistentes, con buen estado general y alta a los 15 y 20 días sin complicaciones. Trece pacientes fueron dados de alta curados. Uno falleció por bronconeumonía. La mortalidad del método fue 0

External fistulas arising from the digestive tract.

External abdominal fistulas that arise from the digestive tract are associated with high mortality and prolonged morbidity in terms of infection, malnutrition, and skin excoriation. Such external fistulas most commonly follow anastomotic leak after gastrointestinal surgery. We identified 58 patients seen over a 5-year period at the University of Louisville Hospitals because of external abdominal fistulas that arose from the stomach (8), duodenum (4), small intestine (26), colon (14), biliary tract (9), and pancreas (7). Fifteen patients had multiple fistulas and 32 had high-output fistulas (greater than 200 mL/day). Closure was achieved in 48 patients, and eight of the 10 patients whose fistulas remained open died. Overall mortality was 19%. Principles of management include control of infection, correction of fluid and electrolyte imbalance, nutritional support, proper wound care, and often operative intervention. Multiple staged operations over many months were particularly important in managing complex wounds with large abdominal wall defects and multiple fistulas. Fistula closure is the ultimate goal, and patience is important to achieve it.

[Methods of treatment of external fistula of gastrointestinal tract]. / Taktika lecheniia naruzhnykh svishchei zheludochno-kishechnogo tracta.

Experience in the treatment of external gastrointestinal fistulas in 1970-1988 consisted of 127 patients with 158 fistulas; 11 patients had a gastric fistula; 14, a duodenal fistula, 42, a fistula of the small intestine; 38, a fistula of the large intestine, and 22 patients had mixed fistulas. Operation for acute appendicitis was the main cause of fistula formation (20.3%). In undeveloped fistulas with considerable and uncontrolled loss of the intestinal contents, treatment consisted in early operation for vital indications for disconnection of the fistula, with preference given to complete bilateral disconnection. In developed fistulas most operations for their closure were carried out through an intraabdominal approach. Total mortality was 25.2%; in most of the fatal cases (90.6%) the fistulas were undeveloped.

Fístulas enterocutáneas: tratamiento quirúrgico / Enterocutaneous fistulas: surgical treatment

Entre 1971 y 1986 se atendió en el Instituto Nacional de Pediatría a 55 niños con diagnóstico de fístulo enterocutánea; la edad de los sujetos iba de tres a 17 años. El 80% de los pacientes fueron enviados de otros hospitales para tratamiento. Los factores desencadenantes más frecuentes fueron: apendicitis perforada, perforación intestinal pos Salmonella, enfermedad isquémica intestinal, vólvulo por Ascaris e invaginación intestinal. En 38 enfermos se diagnóstico fístula de gasto alto y en 17, de gasto bajo. De los 55 pacientes, en 41 se dió tratamiento conservador con dieta elemental, alimentación parenteral, o ambas, y en 30 (73%) se logró cierre espontáneo. En los 14 restantes se requirió intervención quirúrgica y se logró el cierre en 12 (86%). La mortalidad fué de 25% por septisemia y sus complicaciones; los enfermos que murieron tenían fístulas de gasto alto

One hundred and fourteen fistulas of the gastrointestinal tract treated with total parenteral nutrition.

During a period of five years, all patients with fistulas of the gastrointestinal tract who received total parenteral nutrition as a part of the therapy were evaluated retrospectively. One hundred and eight patients with 114 fistulas of the gastrointestinal tract were studied. There were 58 male and 50 female patients. The mean age of the patients was 58 years old. Fifty-one per cent (58) of all fistulas resulted from surgical complications and 30 per cent from inflammatory disease. The most common origin of the fistula was the small intestine (48 per cent), with the large intestine being the next most common origin (26 per cent). Ninety-eight of the fistulas were treated successfully. The mean time for closure from the time of diagnosis was 30.9 days. Sixty-one per cent (69) of all fistulas closed spontaneously, the use of parenteral nutrition resolved 37 per cent (42) and 24 per cent (27) resolved after surgical control of sepsis. Twenty-five per cent (29) of the fistulas required definitive surgical closure. Sixteen patients died prior to resolution of the fistula, 11 deaths were directly related to septic complications of the fistula and one died as a result of hemorrhage of the fistula tract. The direct fistula-related mortality rate was 10.5 per cent. Whereas the mortality rate for fistulas remained stable, spontaneous closure rates continue to improve. This is attributed to improved "para-surgical" care, appropriate nutritional support and early and aggressive control of sepsis. Ninety to 95 per cent of fistulas that spontaneously resolve will do so within four to five weeks. Inflammatory disease of the intestine and radiation induced fistulas continue to respond poorly to medical management.

[Ways of reducing mortality in patients with gastric and small and large intestine fistulas]. / Puti snizheniia letal'nosti bol'nykh zheludochno-tonko-tolstokishechnoi fistuloi.

During 16 years operations were performed on 423 patients with peptic ulcers of anastomoses, in 13 of them the disease was complicated by gastro-intestinal-colonic fistulas. Of 7 patients operated upon during first 11 years four patients died, of 6 patients operated upon during the second period (the last 5 years) there were no lethal outcomes. The less lethality was due to using less traumatic operations and longer preparing the patients for operations.

Gastro-intestinal fistulas: the role of nutritional support.

Over the decades the advent of advanced surgical techniques, antibiotics, management of acid-base and electrolyte disorders, monitoring and support of cardiorespiratory function, have greatly implemented the treatment of patients with gastro-intestinal fistulas, resulting in most series in a mortality of approximately 20%. The apparent clinical benefit of sophisticated parenteral nutrition has not further reduced mortality because in the seventies patients in most series were older, sicker, had more advanced cancer, underwent bigger operations and were more at risk in almost every respect. In recent series mortality is almost exclusively determined by uncontrolled sepsis. It is therefore imperative to control intra-abdominal infection because ongoing sepsis ultimately nullifies the effect of other therapeutic modalities. When infection is controlled however nutritional support may serve several purposes. It may relieve malnourishment. It may decrease gastro-intestinal, biliary and pancreatic secretion allowing fistula output to diminish and sometimes fistulae to heal spontaneously. It may allow a potential future operative field to quiet down. With adequate nutritional support fistulae may heal spontaneously (lateral, no distal obstructions, no adjacent abscesses, good quality bowel). Others may be surgically treated with the patient in good nutritional state and with a favourable local situation. Crohn's fistulae heal spontaneously in a large percentage (80%) but have to be operated after closure because the cause of the fistulae is almost invariably an irreversibly stenosed fibrotic bowel segment so that fistulae may recur after resumption of oral feeding. In unfavourable fistulae (total disruption, adjacent abscesses, bad quality bowel) infection is often difficult to control.(ABSTRACT TRUNCATED AT 250 WORDS)

Review of 404 patients with gastrointestinal fistulas. Impact of parenteral nutrition.

This paper represents an extensive review, spanning 30 years of experience with 404 patients with gastrointestinal fistulas. It includes the first period (1945-1960) during the introduction of antibiotics, the second period (1960-1970) which saw rapid improvements in parasurgical care including, respiratory support, perfection of antibiotics, some introduction of nutritional support and improved monitoring, and the third period which saw the introduction of parenteral nutrition specifically central venous hyperalimentation using hypertonic glucose and amino acids (1970-1975) in the treatment of patients with fistulas. The principal causes for mortality in the historical sense were malnutrition, sepsis and electrolyte imbalance. Mortality among patients with gastrointestinal cutaneous fistulas decreased between the first and second periods from approximately 48 to 15%. Surprisingly, mortality did not decrease further in the "hyperalimentation period" although spontaneous closure of gastrointestinal fistulase increased. The results suggest that the improvement in mortality in patients with gastrointestinal cutaneous fistulas is mostly due to the introduction of improved parasurgical care. It is acknowledged that nutritional support was practiced in the 1960's although this was generally not in the form of hyperalimentation. The addition of hyperalimentation in large scale to the treatment of gastrointestinal cutaneous fistulas has improved spontaneous closure and is a valuable part of the armamentarium. The decrease in mortality however, cannot be attributed to parenteral nutrition.