The gastric tube for esophageal replacement in children

The gastric tube for esophageal replacement in children

Volume 66, Number 3 September 1973 THORACIC AND CARDIOVASCULAR SURGERY The Journal of The gastric tube for esophageal replacement in children Kath...

2MB Sizes 9 Downloads 51 Views

Volume 66, Number 3

September

1973

THORACIC AND CARDIOVASCULAR SURGERY The Journal of

The gastric tube for esophageal replacement in children Kathryn D. Anderson, M.D. * (by invitation), and Judson G. Randolph, M.D., ** Washington, D. C.

Since the report in 1955 by Dale and Sherman," the colon has been the organ most widely used as an esophageal substitute in children. In some instances, the colon may be unsuitable. In 1966, Burrington and Stephens" began working with the gastric tube for esophageal replacement in selected children. In 1967, the tubed gastric pedicle was used at the Children's Hospital of the District of Columbia for a patient whose colon transplant failed. Experience with this patient was so gratifying that the gastric tube has been used as the primary organ for esophageal replacement in 6 additional paFrom the Surgical Service, the Children's Hospital National Medical Center, Washington, D. C., and the Department of Surgery, George Washington University,

Washington, D. C. Read at the Fifty-third Annual Meeting of The American Association for Thoracic Surgery, Dallas, Texas, April 16, 17, and 18, 1973. • Formerly, Chief Surgical Resident, Children's Hospital. Presently Assistant Professor of Surgery and Director of Pediatric Surgery, Georgetown University, Washington, D. C. "Surgeon-in-Chief, Children's Hospital National Medical Center, and Professor of Surgery, George Washington University.

tients. Clinical evaluation of these 7 children forms the basis of this report. Clinical material

In the past 6 years, 7 infants and children have undergone esophageal replacement with the tubed gastric pedicle (Table I). The age range at the time of operation has been 8 months to 5 years. Three of the patients needed reconstruction of the esophagus because they were born with esophageal atresia without fistula. Four children had extensive esophageal strictures secondary to lye ingestion. Illustrative case reports CASE 1. V. T. (CHDC No. 77364) was first seen at the age of 15 months, 3 months after ingestion of lye. There was extensive esophageal stricture for which numerous dilatations were carried out over the next few months. This approach was abandoned after repeated episodes of aspiration pneumonitis complicated his course, and a substernal right colon interposition procedure was carried out. After the operation, the interposed segment became ischemic, necessitating its removal. For the ensuing 2 years the child was

333

The Journol of

334

Anderson and Randolph

Thorocic ond Cardiovascular Surgery

esophagus

right gastroep iploic a. Fig. 1. Drawing of formation of the gastric tube. Note the distal incision at the point of division of the right gastroepiploic artery.

Table I Case No.

Initials

I 2 3 4 5 6 7

V.T. F.T. C. H. J. B. S. L. S.c. P. S.

Diagnosis 4 yr. 5 yr.

3 3 8 8 8

yr. yr. mo. mo. mo.

M M

F M F M F

Lye stricture Lye stricture Lye stricture Lye stricture Esophageal atresia Esophageal atresia Esophageal atresia

maintained in good condition by gastrostomy feedings. At the age of 4 years, a retrosternal bypass operation with the gastric tube was carried out. The cervical anastomosis was performed as a second stage 8 days later. He required dilatation of the upper anastomosis at 6 month intervals for the first year after the operation but has done well. He eats by mouth normally, and his weight gain and growth are normal for his age.

Comment. The complication of failure of the blood supply of a transposed colon is fortunately very rare. However, in such an instance or in cases in which the marginal artery is so poorly developed it may not

Route

Substernal Transthoracic Transthoracic Transthoracic Transthoracic Substernal Transthoracic

Operation: No. of stages

2 I I I 2 2 2

adequately support the isolated portion of colon, the gastric tube is a useful alternative. CASE 2. S. L. (CHDC No. 230023), a l-dayold infant, presented with isolated esophageal atresia. A gastrostomy and cervical esophagostomy were performed shortly after admission. At 8 months, when the infant weighed 17 pounds, a gastric tube was constructed and placed behind the hilus of the lung. The cervical anastomosis was deferred because of the length of the operative time in the infant. This anastomosis was performed a week later; a small leak developed but healed spontaneously without significant stricture. One month later, during dilatation of the cervical anastomosis, the gastric tube was per-

Volume 66

Gastric tube for esophageal replacement

Number 3

335

September, 1973

right gastroepiploic a.

Fig. 2. Suturing of the gastric tube is done in stages as the flap is cut from the greater curvature. forated in omy and recovered done well

the chest requiring immediate thoracotclosure of the perforation. The child without further complication and has since, eating normally by mouth.

Comment. It is recognized that esophageal atresia without tracheoesophageal fistula is, in most cases, associated with complete absence of the thoracic esophagus. Esophageal substitution is usually necessary. The tubed gastric pedicle can be safely and satisfactorily interposed at an early age. CASE 3. F. T. (CHDC No. 0243877/8), a 5-year-old boy, ingested powdered lye 7 months prior to admission. This produced a severe pharyngeal burn, necessitating a tracheostomy, and an esophageal stricture which could not be dilated. Exploration of the cervical esophagus confirmed the total absence of a lumen, and a gastric tube was constructed and anastomosed to the pharynx. He was unable to swallow without aspiration until the scar tissue in the supraglottic area was resected and replaced with a split-thickness skin graft. He has since learned to swallow normally and has had full return of laryngeal function.

Comment. In this instance, the severe burn began in the hypopharynx. The larynx

and epiglottis were severely scarred as well, necessitating a very high insertion of the tube in the neck at the level of the tonsillar fossa. This readily available length of the tubed gastric pedicle is one of its major advantages. Operative technique

The abdomen is entered through a transverse incision. Division of the gastrocolic omentum permits inspection of the left gastroepiploic artery at its origin from the splenic artery and determination of its suitability to supply the tube. The right gastroepiploic artery is divided approximately 2 em. proximal to the pylorus. Parallel incisions are then made in both the anterior and posterior walls of the stomach, as shown in Fig. 1, about 1 em. from the greater curvature. The incisions are begun at the level of ligation of the right gastroepiploic artery and are continued until sufficient length is obtained. The flap, with its vascular pedicle, is rolled around a red,

The Journal of

336

Anderson and Randolph

Thoracic and Card iovascular Surgery

Fig. 3. Oper ative picture of the partially sutured tube.

rubber catheter to form the tube. The size of the cath eter varies with the size of the patient but ranges from No. 18 to No. 24 Fr. The edges of the gastric flap are sutured together in two layers-an inner layer in the mucosa with 3-0 chromic catgut and a serosal layer with interrupted 3-0 silk. The inner suture line is continuous except for several centimeters at the origin of the tube which will lie in the neck, at which point they are interrupted. The tube is sutured around the cath eter in stages as the flap is being cut (Figs. 2 and 3) to minimize blood loss. Once the desired tube length is achieved (Figs. 4 and 5) the catgut suture is continued over onto the stomach wall to reapproximate the anterior and posterior edges of the stomach. The running catgut suture along the newly formed greater curvature is oversewn with interrupted sutures of 3-0 silk. The tube is now ready for placement in its final position. An incision is made in the left side of the neck

Fig. 4. Completed gastric tube lying over the chest before placement in the thorax. Relat ionships of the tube , vascular pedicle . and stom ach are shown.

just above the clavicle, and the cervical esophagus is dissected free. In esophageal atresia, the esophagocutaneous fistula created in the newborn period is dissected free and the edges are trimmed. In patients with caustic stricture without previous esophagostomy, the esophagus is divided at a level above the burned portion ; then, the lower end of the esophagus is closed with interrupted 4-0 silk sutures and allowed to retract into its natural position in the posterior mediastinum. Either the substernal or transthoracic retrohilar position may be selected for the tube . If the substernal location is chosen , the tunnel is prepared by blunt dissection from both the abdominal and neck incisions. If the transthoracic route is elected, a posterolateral incision is made

Volume 66 Number 3

Gastric tube for esophageal replacement

337

September, 1973

left gastroepiploic a.

Fig. S. Depiction of relationship of tube and stomach at completion of suturing. Note the interrupted sutures at the end of the tube which permit trimming without disruption of the entire suture line.

in the left chest at the level of the sixth intercostal space, and a 2 to 3 em. opening is created in the diaphragm posterolateral to the esophageal hiatus. The tube is drawn through this new opening and positioned behind the left lung root. The opening in the diaphragm must be adequate to transmit the tube without obstructing the vascular pedicle. Next, a passage, wide enough to admit the gastric tube, is made at the apex of the thorax in Sibson's fascia. Both the thoracic and neck incisions are used in its construction. Great care should be taken to protect the subclavian vessels which lie just anterior to the plane of dissection and to avoid the stellate ganglion which lies pos-

teriorly. As the tube is brought into the neck, twisting is avoided since this can impair the blood supply. The anastomosis between the gastric tube and the esophagus may be performed at this stage or may be delayed. With the latter approach, the tube is brought out onto the left side of the neck as a stoma. The cervical anastomosis is made in two layers by means of interrupted sutures of 4-0 silk. Gastrostomy is performed routinely. The abdomen is closed without drainage, but the neck is drained. Postoperative management

Gastrostomy feedings are begun as soon as peristalsis returns. When the operation is

The Journal of

338

Anderson and Randolph

Thoracic and Cardiovascular Surgery

Fig. 6. Barium swallow, I month after operation, shows ample caliber of tube and good mediastinal position without redundancy.

Fig. 7. Barium swallow, I month after operation, shows retrohilar position. Reflux into strictured esophagus is present. Note that the rem aining stom ach now appe ars normal in size.

completed in one stage, oral feedings are begun on the tenth day after a barium swallow has demonstrated integrity of the gastric tube (Figs. 6 and 7). If the tube has been placed via the intrathoracic route, the chest tube is not removed until this time. The gastric tube can be visualized on the tenth day , even if the cervical anastomosis has been delayed, by instilling barium through a catheter inserted into the stoma of the gastric tube in the neck . When the cervical anastomosis is staged, oral liquids are begun 5 days after the second operation. If there is any question as to compromise of the blood supply of the upper end of the tube, the operation should be staged. However, the gastric contents can reflux out of the tube, necessitating special care of the skin of the neck to avoid maceration and to min imize inflammation in the operative field for the subsequent anastomosis. It is

preferable to complete the cervical anastomosis at the initial operation. Discussion Reconstruction of the esophagus has been achieved in many different ways. The first reconstruction of the cervical esophagus was described by Czerny- in 1877 . Early efforts to replace the thoracic esophagus involved use of pedicle tubes lined by skin." Later, portions of jejunum' < 18 and colon1 3 , 1 5 . 22 were used. More recently, prosthetic materials have been studied in the laboratory." In adults, transposition of a major portion of the stomach was successfully bridged an esophageal defect,20 However, children do not adapt well to the presence of a major portion of the stomach in the thoracic cavity. Pulmonary complications are frequent because of atelectasis or reflux with aspiration. Experience has

Volume 66 Number 3 September, 1973

shown that nutrition is not well maintained, and the consequences of gastric distention in a relatively small cavity with a mobile mediastinum may be disastrous. Work with a tubed gastric pedicle was first reported by Depage: in 1903. He created a tube from the anterior wall of the stomach and brought it out onto the abdominal wall for feeding purposes. Two years later, Beck and Carrel' demonstrated that a gastrostomy could be constructed from a flap fashioned from the greater curvature of the stomach and emphasized the importance of the gastroepiploic artery in the vascular support of this tube. Use of the tubed gastric pedicle to bypass the esophagus was first suggested after animal and cadaver experiments by Jianu':' in 1912. However, the procedure was rarely successful because of difficutly in creating enough length for the tube to reach the neck. Long-term evaluation of the procedure was not possible because esophageal bypass was usually performed in debilitated patients suffering from preterminal esophageal carcinoma. Mes" in 1948 and Gavriliu" in 1951 reintroduced the gastric tubed pedicle as a primary method of esophageal replacement. Heimlich"- 12 popularized the technique in the United States and recommended its use in adults with both carcinoma and benign strictures of the esophagus. The gastric tube was first used in children by Burrington and Stephens" who reported their experience with this technique in 8 children in 1968. They were led to try this procedure in an infant who was born with esophageal atresia and coexisting imperforate anus, since the loss of a segment of colon for bypass might have added to the difficulties of rehabilitation of a surgically reconstructed anus. Our experience with the tubed gastric pedicle began in 1967, when a colon transplant became necrotic, necessitating its removal 3 days after the original operation (Table I, Case I). A subsequent laparotomy disclosed that the arterial anatomy of the remaining colon precluded its use for esophageal substitution. Later, with the help

Gastric tube for esophageal replacement

339

of Burrington,' a gastric tube was constructed. The child's subsequent course was very gratifying, provoking interest in the use of this procedure as a primary method of esophageal replacement. Like the colon, the gastric tube may be placed in the substernal or intrathoracic position. The tube was placed in the substernal position in 2 of our patients, while in 5 it is behind the lung. The advantages of one route over the other with respect to the colon have been well discussed.v- 21 In general, the substernal tunnel can be made more quickly since entrance into the thoracic cavity is unnecessary. Thus complications relative to thoracotomy are avoided. On the other hand, the intrathoracic retrohilar position of a substitute esophagus more nearly approaches normal anatomy, and esophagoscopy is more easily accomplished. None of the patients in this group has died. Because of the possibility of infectious complications following removal of the spleen in children, splenectomy has been avoided in all patients. In no case has this resulted in compromise of the length of the tube. Distention of the intrathoracic portion of the tube has not occurred, and the wellknown "cascading" of contrast material with delay in entering the stomach, noted on fluoroscopy of the colon, has not been seen. Use of the gastric tube is not without complications. Cervical stricture has occurred in 3 patients but required revision in only 1. In this patient, the lye stricture was so extensive that the anastomosis was done with proximal scarred esophagus. This patient also developed obstruction of the pyloric outlet which required surgical correction. The complication probably occurred as a consequence of damage to the vagus nerve resulting either from the original lye burn or from dissection of the cervical esophagus. The lower end of the gastric tube, where it passes through the diaphragm, is especially vulnerable to perforation with an esophageal dilator, although it is rare for this segment of the tube to need

The Journal of

340

Anderson and Randolph

Thoracic and Cardiovascular Surgery

dilatation. One such instance occurred in an infant and necessitated immediate transthoracic repair. Another child developed an ulcer at the lower end of the tube, but the ulcer disappeared on an antacid regimen. We feel that in this case, the intrathoracic portion of the gastric tube was somewhat redundant and there was some stasis at the lower end of the tube. In an extensive experience with the use of this procedure in adults, Heimlichtv P does not report any significant problem with reflux of gastric acids into the tube and has no recorded instance of ulcer formation. Longterm study will be necessary to evaluate the potential of peptic ulceration in children. These complications have all responded well to appropriate therapy. All 7 of these children are now eating well, with good function of the substitute esophagus; weight gain and growth have been normal for their respective ages. Conclusions 1. In children with coexisting abnormalities of the colon or anus, the gastric tube is preferable to the colon for esophageal substitution. 2. Because of the highly developed collateral system in the submucosa of the stomach, the gastric tube has a rich blood supply. 3. The gastric tube can be made long enough to reach easily into the neck. 4. The creation of a gastric tube is technically simple, and the operation can be performed in less time than the colon operation. This is of significance in infants. REFERENCES Beck, A. R., and Carrel, A.: A Demonstration of Specimens Illustrating a New Method of Formation of a Prethoracic Esophagus, III. Med. 1. 7: 463, 1905. 2 Bircher, E.: Ein beitraf zur plastischen bildung eines neuen Oesophagus, Zentralbl. Chir., Dec. 21, 1907. 3 Burrington, J. D., and Stephens, C. A.: Esophageal Replacement With a Gastric Tube in Infants and Children, J. Pediatr. Surg. 3: 246, 1968.

4 Burrington, J.: Personal communication. 5 Czerny, Y.: Neue Operationen, Zebl. Schiro 4: 443, 1877. 6 Dale, W. A., and Sherman, C. D., Jr.: Late Reconstruction of Congenital Esophageal Atresia by Intrathoracic Colon Transplantation, 1. THORAC. SURG. 29: 344, 1955. 7 Depage, A.: Nouvelle methode de gastronomie (Abstr.), Presse Med. 19: 755, 1903. 8 Gavriliu, D., and Georgescue, L.: Esophagoplastie direction a material gastric, Rev. Stiintelor Med. (Bucharest) 3: 33, 1955. 9 Gross, R. E.: The Surgery of Infancy and Childhood, Philadelphia, 1955, W. B. Saunders Company. 10 Harrison, A. W.: Transthoracic Small Bowel Substitution in High Stricture of the Esophagus, J. THORAC. SURG. 18: 316, 1949. 11 Heimlich, H. J.: Peptic Esophagitis With Stricture Treated by Reconstruction of the Esophagus With a Reversed Gastric Tube, Surg. Gynecol, Obstet. 114: 673, 1962. 12 Heimlich, H. J.: Elective Replacement of the Esophagus, Br. J. Surg, 58: 913, 1966. 13 Hopkins, W. A., and Zwiren, G. T.: Colon Replacement of the Esophagus in Children, J. THORAC. CARDIOVASC. SURG. 46: 346, 1963. 14 Jianu, A.: Gastronstime u oesophagosplastik, Dtsch. Z. Chir. 118: 383,1912. 15 Kelling, G.: Oesophagoplastik mit hilfe des querkolon, Zentralbl. Chir. 33: 34, 191 I. 16 Lister, J. L., Altman, R. P., and Allison, W. A.: Prosthetic Substitution of Thoracic Esophagus in Puppies: Use of Marlex Mesh With Collagen or Anterior Rectus Sheath, Ann. Surg, 162: 812, 1965. 17 Mes, G. M.: New Method of Esophagoplasty, J. Int. Coli. Surg. 11: 270, 1948. 18 Roux, c.: L'oesophago-jejuno-gastrostomose. Nouvelle operation par retrecissement infranchissable de I'oesophage, Sern. Med. 27: 37, 1907. 19 Sherman, C. D., r-, and Waterston, D.: Esophageal Reconstruction in Children Using Intrathoracic Colon, Am. J. Dis. Child. 32: 11, 1957. 20 Sweet, R. H.: Subtotal Esophagectomy With High Intrathoracic Esophagogastric Anastomosis in the Treatment of Extensive Cicatricial Obliteration of the Esophagus, Surg. Gynecol. Obstet. 83: 417, 1946. 21 Waterston, D.: Colonic Replacement of Esophagus (Intrathoracic), Surg. Clin. North Am. 44: 1441, 1964. 22 Waterston, D.: Reconstruction of the Esophagus, in Mustard, W. T., Ravitch, M. M., Snyder, W. H., Jr., Welch, K. J., and Benson, C., editors: Pediatric Surgery, ed. 2, Chicago, 1969, Year Book Medical Publishers, Inc., p. 400.

Volume 66 Number 3

Gastric tube for esophageal replacement

34 1

September. 1973

23 Yudin, S. S.: The Surgical Constriction of 80 Cases of Artificial Esophagus, Surg, Gynecol. Obstet. 78: 561, 1944.

Discussion DR. JOHN HENRY Nashville, Tenn.

In March, 1973, I was asked to see an 11year-old lad at Vanderbilt Hospital who was in extremis with a 24 hour history of substernal pain. The child was born with proximal esophageal atresia and C-type tracheoesophageal fistula. Following correction, the anastomosis fell apart and esophageal replacement was required. A greater curvature gastric tube was constructed to replace the esophagus. The child did well for 10 years but developed significant dysphagia and substernal pain 3 months before entering the hospital. On admission, he was cyanotic, dyspneic, and hypotensive. Chest x-ray study demonstrated a peculiar air shadow in the mediastinum and pericardium. [Slide] A central venous pressure catheter was introduced, a nasogastric tube was placed into the gastric tube pedicle, and resuscitation was begun. X-ray films taken immediately prior to contrast study showed a marked accumulation of air in the pericardial cavity. [Slide] The study showed that the contrast material entered the pericardial cavity from the gastric tube. [Slide] He was taken to the operating room immediately where the mediastinum and pericardial cavity were explored. Gastric contents and a thickened pericardium (10 mm. thick) were found. The thick pericardium was excised, the mediastinum was drained, and a gastrostomy was performed. Esophagoscopy was attempted, but a cervical stricture prevented visualization of the ulcer. The child was maintained on total parenteral hyperalimentation. Repeat contrast study on the seventh day showed free reflux from the stomach into the gastric tube and into the pericardial cavity. No dye could be seen traversing the pylorus. The gastric secretory volume for a 12 hour, overnight period was 1,200 c.c. It contained 126 mEq. of total acid and 100 mEq. free acid. The child underwent a second surgical procedure on Day 10. [Slide] A large ulcer (4 em. in diameter), a cavity of similar size, and a pericardial fistula (1.5 em.) were observed at the junction of the middle and lower thirds of the gastric tube. The site of gastric obstruction was a scarred pylorus and antrum. Removal of the gastric tube, creation of a cervical esophagostomy, laparotomy with closure of the proximal stomach, and a U'-shaped Finney

pyloroplasty were accomplished. One month after the second operation, the child was gaining weight. The plan is to replace his esophagus with a colon interposition as described by Waterston. This case represents a serious late complication (10 years after the initial procedure) of the use of tL gastric tube pedicle for replacement of the esophagus. It demonstrates peptic ulceration related to stasis, similar in location to that reported by Drs. Anderson and Randolph, and stricture of the gastric tube esophageal anastomosis, which the authors demonstrated in 3 of their 7 patients. Peptic ulcerations are not confined only to gastric tube replacements but have also been reported in jejunal replacement tubes and in colon interpositions. Dr. John Malcolm reported 11 such cases in 1968 (1. THORAc. CARDIOVASC. SURG. 55: 763, 1968). I think it is very important to perform an adequate pyloroplasty at the time of esophageal replacement. Although further experience and longterm follow-up are needed on all forms of esophageal replacements, complete or selective vagotomy may prove to be essential. I urge each of you who are following such patients to study their ulcer potential carefully and treat those with high acid secretion appropriately. DR. WILLIAM E. NEVILLE Newark, N. J.

My preference for the colon to reconstruct the esophagus is based upon an 18 year follow-up in children who have progressed satisfactorily in growth and nutrition to adulthood. George Clowes and I presented our results before this Association in 1957 using the colon to replace the esophagus. In 1 child, a stricture of the lower esophagus was resected and a colon interposition operation was performed in 1956. He has done very well. In another boy with a long stricture of the esophagus due to caustics, the colon was placed retrosternally between the cervical esophagus and the stomach in 1956. We resected his esophagus a few months later and he has progressed satisfactorily to adulthood. Still another boy had a colon transplant through a mediastinal tunnel at the age of 1 year in 1955. The original pathology was a congenital blind upper esophageal segment and a lower tracheoesophageal fistula. He is now a freshman in college and has had no difficulties. In high school he was an excellent athlete participating in all sports. I must concede that the tubed gastric pedicle is a welcomed alternative to the colon and I couldn't criticize anyone for using it. However, the colon has proved its efficacy over the years and on this basis should be the preferential substitute for the esophagus.

342

Anderson and Randolph

The Journal of Thoracic and Cardiovascular Surgery

DR. R. HENDERSON Toronto, Ontario, Canada

Reflux is the major problem in any form of tube replacement of the esophagus. We have been interested in methods of preventing reflux in cases in which a gastric tube is used to replace the esophagus. In experimental and in clinical studies we have been able to show that a 6 ern. tube of stomach, below the diaphragm, prevents reflux. On the other hand, if the tube is entirely intrathoracic, free reflux occurs. Studies of esophageal pressure have shown that the tube actually presents as a pressure barrier. By maintaining this pressure barrier below the diaphragm, it is possible to control reflux. If the tube is subjected to myotomy, the pressure barrier falls and reflux again occurs. If atropine is given the pressure falls; if gastrin is given the pressure rises. This principle is used in the gastric tube of the Collis gastroplasty to prevent reflux. Similarly, in cases in which the tube is used to replace the lower half of the esophagus, reflux is completely controlled if a segment 6 cm. long is maintained below the diaphragm.

mechanism that helps us prevent reflux. This can be a difficult problem indeed. We have all noticed in our series of colon transplants the problems of reflux all the way into the anastomotic area of the neck, which causes further difficulties. It is difficult to argue with Dr. Neville's extensive experience in colon transplants. We too have followed his work with colon transplants and that of others through the years, and we believe that this gastric operation simply offers an alternative in selected instances. Indications will vary with the individual surgeon as to whether he uses this procedure for all kinds of esophageal replacement or just in certain instances, such as in patients with a colon anomaly, an imperforate anus, or perhaps a tenuous blood supply. Dr. Henry's story coming 10 years later certainly emphasizes the problem of ulceration which can occur in either a transposed colon or a gastric tube. I think we will need to follow some children for a long time before the jury comes back in to reveal whether this is a significant problem.

DR. RANDOLPH (Closing) Thank you very much. I was most interested in Dr. Henderson's remarks concerning the

Introductory abstracts Beginning in January, 1974, it is requested that each article begin with a brief abstract. Authors submitting articles on or after September 1, 1973, should supply an abstract of 150 words or less.