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Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.54 no.3 Campinas May/June 2004
Gastric emptying after oral contrast for abdominal tomography. Report of six cases*
Vaciamiento gástrico después de la administración oral de contraste en tomografía computadorizada del abdomen: Descripción de seis casos
Fernando Antonio Nogueira da Cruz Martins, M.D.I; José Luiz Gomes do Amaral, TSA, M.D.II
pelo Setor de Tomografia Computadorizada da EPM UNIFESP, Hospital São Paulo
IIProfessor Titular da Disciplina de Anestesiologia, Dor e Terapia Intensiva da EPM UNIFESP, Hospital São Paulo
BACKGROUND AND OBJECTIVES: Pulmonary injury
due to gastric contents aspiration is a complication related to airway protective
reflexes loss. Tomography imaging with digestive tract contrast requires special
care for children below five years of age requiring general anesthesia or sedation
to assure immobility during the procedure. General anesthesia induction or sedation
after contrast ingestion may pose substantial risk for gastric contents bronchoaspiration,
so contrast administration by gastric tube is often used after tracheal intubation,
since time elapsed for emptying gastric contrast is unknown. This practice means
increased anesthesia duration and leads to issues about the possibility of gastric
emptying in less than one hour. Six patients submitted to abdominal tomography
were evaluated concerning gastric emptying by tomographic slices in stomach
topography to establish whether residual liquid contents remain in that organ
after contrast administration.
CASES REPORT: Participated in this study 6 children undergoing abdominal tomography. Two conscious children presented expressive gastric liquid residual 50 and 45 minutes, respectively, after oral contrast ingestion. Four anesthetized children have also presented gastric liquid residual 40-50 minutes after contrast administration through gastric tube. In two of them remarkable gastric liquid content remained even after stomach aspiration.
CONCLUSIONS: In all studied cases, forty to fifty minutes were not enough for gastric emptying after contrast administration and even stomach aspiration trough gastric tube has resulted in significant residual liquid.
Key Words: ANESTHESIA, Pediatric; COMPLICATIONS: bronchoaspiration; FASTING; THERAPY AND DIAGNOSTIC PROCEDURES: computer tomography
JUSTIFICATIVA Y OBJETIVOS: La lesión
pulmonar secundaria a la aspiración del contenido gástrico es complicación
asociada a la pérdida de los reflejos protectores de las vías aéreas.
En este contexto, la realización de exámenes tomográficos que
incluyan la contrastación del tracto digestivo, exige particular atención
en niños menores de cinco años, que necesitan anestesia general o
sedación, para asegurar inmovilidad durante el procedimiento. La inducción
de la anestesia o sedación después de ingestión de la solución
de contraste puede traer riesgo substancial para la broncoaspiración del
contenido gástrico. Esto hace con que se opte por administrar el contraste
por sonda gástrica después de la intubación traqueal, una vez
que no se conoce el tiempo de vaciamiento gástrico después de utilización
de solución contrastante. Esta conducta representa aumento del tiempo de
anestesia, lo que resulta en constante cuestionamiento sobre la posibilidad
de vaciamiento del contenido gástrico en tiempo inferior a una hora. Seis
casos de pacientes sometidos a tomografía de abdomen fueron evaluados cuanto
al vaciamiento gástrico por medio de la realización de cortes tomográficos
en la topografía del estomago, con el objetivo de determinar la presencia
o ausencia del contenido residual líquido en ese órgano, después
de la administración de la solución de contraste.
RELATO DE LOS CASOS: Fueron evaluados seis niños sometidos a tomografía contrastada del abdomen. Dos, no anestesiados, presentaron expresivo residuo líquido gástrico pasados 50 y 45 minutos, respectivamente, de la ingestión de contraste. Cuatro, sometidos a anestesia general, también presentaron residuo líquido gástrico pasados 40 a 50 minutos de la administración de contraste vía sonda oro/nasogástrica. En dos de ellos persistió apreciable residuo líquido en el estomago, igualmente después de la aspiración del contenido por la sonda.
CONCLUSIONES: En los casos observados, el tiempo de 40 a 50 minutos fue insuficiente para el vaciamiento del estomago después de la administración de solución contratante e igualmente la succión del contenido por sonda nasogástrica resultó en permanencia de significante volumen residual líquido.
Pulmonary injury secondary to gastric contents aspiration is a relevant complication associated to airways protective reflexes loss determined by general anesthesia 1. Among factors contributing to this event there are gastric content volume and characteristics, such as pH, presence of particles, colonization, etc. In adults, gastric contents equal to or above 25 mL 2 in pH equal to or below 2.5 3 is a critical situation, although predictive values for aspiration are questionable and do not take into consideration other factors contributing for aspiration pathogenesis and prevention 4.
Pregnancy, stress 5, emergency procedures 6, age extremes 7, obesity 8, trauma, pain, drugs (especially opioids), among others, are followed by gastric emptying delay and increased stomach acid secretion, being risk factors for aspiration.
The incidence of gastric contents aspiration is estimated in 0.8 to 4.7 cases in 10 thousand anesthesias, being 4.3 times more frequent in emergency procedures 5,6,8,9.
It is a complication expected during to anesthetic induction and tracheal intubation associated to airway instrumentation and protective reflexes loss. However, approximately 50% of postoperative aspirations are recorded 9.
Clinical expression (cough, wheezing, hypoxemia or radiological consolidation) is not present in the next two hours after the event in 64% of cases 10.
Such considerations lead to preoperative fasting adapted to different clinical situations and age brackets. The American Association of Anesthesiologists (ASA) 11 recommends clear fluids fasting of at least 2 hours. Water, coffee (plain), tea, soft drinks and fruit juice without pulp are considered clear fluids, among others. Light meals with toasts, tea or coffee (plain) are allowed up to 6 hours before the procedure. For breast milk it is suggested at least 4 hours fasting and for pediatric formulas at least 6 hours. Non-human milk is not included among clear fluids because it results in solid residues. At least 6 hours fasting is recommended between non-human milk ingestion and the procedure. Solid foods, especially meat and fatty matters require prolonged fasting. These foods are forbidden on surgery day. Patients to be operated on in the morning (after 6:00 a.m.) are oriented to fast as from 10:00 p.m. of previous day that is a fasting period of at least 8 hours. Minor amounts of water to ingest preanesthetic medication or other oral drugs have no inconvenient and are allowed 11.
Tomographic images with contrast ingestion require special attention. From the available alternatives, there is the possibility of administering contrast orally or through gastric tube, as a function of patient's cooperation for ingestion and immobility during the procedure.
In younger children (in general below 5 years of age), general anesthesia or sedation is needed to assure immobility during the procedure. Anesthesia or sedation induction after contrast ingestion may pose substantial risk for gastric contents aspiration and this leads to the option of administering contrast by gastric tube after tracheal intubation in previously anesthetized patients since gastric contents emptying time after contrast ingestion is not known. This method represents considerable increase in anesthesia duration and has led to continuous questioning about the possibility of gastric content emptying in less than one hour. This report aimed at describing 6 cases of children submitted to abdominal tomography who were evaluated in terms of gastric emptying through tomographic slices of stomach topography. We have tried to determine the presence or absence of liquid contents in this organ 40 to 50 minutes after contrast ingestion.
Participated in this study 6 children submitted to abdominal tomography after contrast ingestion.
Contrast was meglumine ioxithalamate, made up of triiodate acid (ioxithalamic acid), meglumine, trihydrated monosodic phosphate and sodium calcium edetate. Its iodine content is 300 mg.mL-1 with 66% concentration and osmolality of 1650 mOsm.kg-1 of water (information obtained from substance's package insert).
According to the protocol of the Image Diagnostic Department, Hospital São Paulo, EPM/UNIFESP, oral contrast volume for abdominal tomography is 30 mL.kg-1 of patient's weight, with 3% contrast in 5% glucose solution, juice or water, in equal fractions at 10-minute intervals and time elapsed between beginning of ingestion and tomography is 2 hours. Images start immediately after the last fraction ingestion.
In anesthetized patients, contrast is administered after general anesthesia induction and tracheal intubation, via nasograstric tube positioned by the anesthesiologist. Images start 20 minutes after contrast infusion.
Female patient, 6 years old, with clinical history of abdominal pain for 4 days, vomiting and fever and suspicion of psoitis. Patient was not anesthetized because she was cooperative in ingesting contrast and staying immobile during the procedure. Tomographic slices of stomach topography have shown the presence of liquid gastric contents 50 minutes after ingesting the last contrast fraction (Figure 1).
Male patient, 8 years old, submitted to tomography for late postoperative control of renal tumor resection. Patient was not anesthetized because he was cooperative in ingesting contrast and staying immobile during the procedure. Tomographic slices of stomach topography have shown the presence of liquid gastric content, 45 minutes after ingesting the last contrast fraction (Figure 2).
Male patient, 1 year old and clinical history of Budd-Chiary syndrome and ascites, was submitted to general anesthesia with tracheal intubation before contrast administration via nasograstric tube (in 5% glucose solution). Tomographic slices of stomach topography have shown the presence of liquid gastric contents (Figure 3) 45 minutes after contrast administration (total of 250 mL). Before tracheal extubation, gastric contents were emptied through the nasogastric tube and 125 mL of total administered volume were recovered.
Male patient, 1 month old, with polycystic kidneys, submitted to general anesthesia and tracheal intubation before contrast administration via nasogastric tube (in 5% glucose solution). Tomographic slices of stomach topography have shown the presence of liquid gastric contents (Figure 4) 40 minutes after contrast administration (total of 125 mL). Before tracheal extubation, gastric contents were emptied through the nasogastric tube and 30 ml of total administered volume were recovered.
Male patient, 2 years old and history of liquor cyst distal to ventriculoperitoneal shunt, submitted to general anesthesia and tracheal intubation before contrast administration via nasogastric tube (in 5% glucose solution). Tomographic slices of stomach topography have shown the presence of liquid gastric contents (Figure 5A) 40 minutes after contrast administration (total of 400 mL). Before tracheal extubation, gastric contents were emptied through the nasogastric tube and 200 mL of total administered volume were recovered. New tomographic slices were obtained immediately after emptying and has shown stomach contents emptying, however with considerable liquid residue remaining in the organ (Figure 5B).
Female patient, 3 years old, submitted to contrasted tomography for postoperative control of adrenal neuroblastoma. General anesthesia and tracheal intubation were performed before contrast administration via nasogastric tube (in 5% glucose solution). Tomographic slices of stomach topography have shown the presence of liquid gastric contents (Figure 6A) 40 minutes after contrast administration (total of 390 mL). Before tracheal extubation, gastric contents were emptied through the nasogastric tube and 200 mL of total administered volume were recovered. New tomographic slices were obtained immediately after emptying and has shown stomach contents emptying, however with considerable liquid residue remaining in the organ (Figure 6B).
Data in our study have shown that 40 to 50 minutes after final fraction ingestion of 30 mL.kg-1 meglumine ioxithalamate in children aged 1 month to 8 years, liquid gastric residue is expressive.
According to the American Society of Anesthesiologists 11 the recommendation to decrease gastric contents aspiration risk for clear fluids is at least 2 hours fasting which, however, would make unfeasible the exam considering that after this time, the quality of tomographic images could be impaired by unequal and inefficient digestive tract contrasting.
In cases 1 and 2, oral contrast was administered with water or fruit juice without pulp, that is, clear fluids. Patient 1 presented inflamed abdomen which could determine gastric emptying delay. Patient 2, however, could have been considered healthy since he was being submitted to late postoperative control of a retroperitoneal surgery and the exam has not revealed any clinical change.
The analysis of cases 3, 4, 5 and 6 clearly shows that gastric emptying through nasogastric tube does not determine the recovery of all contrast volume administered. In case 3, 50% of administered volume was recovered by the tube, while in case 4, this value was below 30%. Obviously, part of administered solution has followed digestive tract path along time, between administration and procedure completion, however in cases 4 and 5, even after gastric emptying by normal physiological movements and nasogastric tube aspiration, liquid residue was observed in the stomach.
Our findings confirm other authors' reports 12, who have studied 42 patients and have observed that fluid volume obtained with orogastric suction is poorly related to residual gastric contents measured by a dilution method.
On the other hand, it has to be considered that gastric tubes may be useful to decrease gastric contents. Hardy et al. 13 have measured gastric volume aspired by a Salem Sump tube in 24 patients. Then they have directly observed the stomach and measured remaining volume. Residual volume has varied 0 to 13 mL.
It is clear from our data that 40 to 50 minutes are not enough for gastric emptying after meglumine ioxithalamate contrast administration and that even gastric content aspiration via nasogastric tube results in the presence of variable liquid residue. Considering potential gastric contents aspiration risks, and that children below 5 years of age in general need general anesthesia or sedation for abdominal tomography, most adequate approach to minimize such risks is adequate airway protection with tracheal intubation before contrast administration via nasogastric tube.
Nasogastric tube positioned by the Anesthesiologist may be useful to decrease gastric contents after the procedure. This approach, however, does not assure protection against bronchoaspiration risks. After tracheal extubation, the anesthesiologist must have in mind that stomach keeps residual liquid contents, thus requiring the same care preconized for the extubation of "full stomach" patients.
We acknowledge professor Dr. Henrique Lederman; Nurse Marlene Potenza; Nursing Helpers Francisco Silva, Maria Aparecida Mendes, Luzia Neves, Rosalina Ferreira and Sonia Spindola; Radiographic Technicians Marcos Godoy, Ricardo Jimenez and Jose Santos.
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Submitted for publication April 9, 2003
Accepted for publication July 25, 2003
* Received from Setor de Tomografia Computadorizada do Departamento de Diagnóstico por Imagem do Hospital São Paulo da Escola Paulista de Medicina da Universidade Federal de São Paulo (EPM UNIFESP), SP