Original article
Clinical effect of hyperbaric oxygen therapy in adhesive postoperative small bowel obstruction Y. Fukami, Y. Kurumiya, K. Mizuno, E. Sekoguchi and S. Kobayashi Department of Surgery, Toyota Kosei Hospital, 500-1 Josui-cho, Toyota, Aichi 470-0396, Japan Correspondence to: Dr Y. Fukami (e-mail: [email protected])
Background: Hyperbaric oxygen (HBO) therapy is a controversial treatment for adhesive postoperative
small bowel obstruction, with only a few small studies reported. The aim of this study was to assess the clinical value of HBO therapy in the treatment of adhesive postoperative small bowel obstruction. Methods: Between April 2006 and March 2012, all patients with adhesive postoperative small bowel obstruction were treated using either decompression therapy or HBO. Patients undergoing HBO therapy were treated once a day at a pressure of 2·0 atmospheres absolute and received 100 per cent oxygen. Patients showing no clinical and radiological improvement with HBO therapy were converted to decompression therapy by means of a long tube. Medical records were reviewed and outcomes analysed. Results: A total of 305 patients were treated, of whom 142 underwent tube decompression therapy during the first 3 years and the remaining 163 had HBO therapy during the last 3 years. The median number of HBO treatments was 3 (range 1–7). A total of 143 patients (87·7 per cent) were treated successfully with HBO without long-tube decompression. HBO therapy was associated with earlier resumption of oral intake (mean 4·7 versus 6·5 days; P = 0·001) and a shorter hospital stay (mean 10·3 versus 14·1 days; P = 0·001). The rate of operation was 7·4 per cent in the HBO group and 14·8 per cent in group treated by decompression alone (P = 0·037). Conclusion: In this study, HBO therapy was safe for the treatment of adhesive postoperative small bowel obstruction. It reduced the need for surgery and time to recovery as well as the hospital stay. Paper accepted 29 October 2013 Published online 3 February 2014 in Wiley Online Library (www.bjs.co.uk). DOI: 10.1002/bjs.9389
Introduction
Adhesive small bowel obstruction is a major cause of postoperative morbidity, and appropriate management using the proper diagnostic and therapeutic pathway is necessary. Immediate surgical intervention is required when strangulation is suspected. The management of incomplete adhesive small bowel obstruction remains controversial1 – 5 , and initial conservative management should be the choice in most patients. Long-tube decompression is one of the most common conservative treatments, and is successful in most patients5,6 . However, this treatment has become a significant socioeconomic burden because of the high rate of recurrence7,8 . To make matters worse, quality of life during treatment is poor, with symptoms such as sore nose and throat. Hyperbaric oxygen (HBO) therapy involves the intermittent inhalation of 100 per cent oxygen under a pressure greater than 1 atmosphere absolute, and has various beneficial physiological, cellular and biochemical effects9,10 . 2014 BJS Society Ltd Published by John Wiley & Sons Ltd
The impact of HBO therapy in various clinical situations has been evaluated in previous studies9 . Only a few human clinical trials11 – 13 have described the effect of HBO therapy for small bowel obstruction. The aim of the present study was to investigate the clinical value of HBO therapy in adhesive postoperative small bowel obstruction.
Methods
Between April 2006 and March 2012, all patients with adhesive postoperative small bowel obstruction were treated using either decompression therapy or HBO. The diagnostic criteria for adhesive postoperative small bowel obstruction included: a history of previous abdominal surgery more than 4 weeks previously; clinical symptoms and signs of mechanical obstruction, such as abdominal pain, vomiting, abdominal distension and constipation; and a plain abdominal X-ray taken with the patient upright BJS 2014; 101: 433–437
434
Y. Fukami, Y. Kurumiya, K. Mizuno, E. Sekoguchi and S. Kobayashi
and routine computed tomography (CT) showing dilated loops of small intestine, and air–fluid levels and air in the distal small bowel/colon. Emergency abdominal exploration was undertaken in patients with suspected strangulation or peritonitis, and such patients were excluded from the present study. In patients with a history of surgery for cancer, recurrence was ruled out by routine examinations (clinical examination, measurement of tumour marker levels, ultrasonography and CT). When HBO became available, further exclusion criteria were: pregnancy, pneumothorax, emphysema and sinusitis.
Management plan The authors’ conservative strategy for management of adhesive postoperative small bowel obstruction changed after April 2009. In the early part of the study (from April 2006 to March 2009), management comprised no oral intake, administration of intravenous fluids with electrolytes (as nutrition), and insertion of a nasogastric tube until there was clinical improvement. When the small bowel was shown to be markedly dilated by CT, a long tube was inserted for immediate decompression. In the late period (from April 2009 to March 2012), there was no oral intake, intravenous fluids with electrolytes were administered (as nutrition) and HBO therapy was performed within 24 h of admission. A nasogastric tube was inserted if the patient was vomiting. Patients undergoing HBO therapy were treated once a day, up to seven times until improvement was observed, in a single hyperbaric chamber (BARA-MED; Environmental Tectonics Corporation, Southampton, Pennsylvania, USA) at a pressure of 2·0 atmospheres April 2006 to March 2009 (no-HBO interval) Adhesive small bowel obstruction n = 142
absolute with 100 per cent oxygen. The sessions started with 15 min of compression to 2·0 atmospheres and lasted 90 min, ending with 15 min of decompression to 1·0 atmosphere. Clinical improvement was defined by the presence of decreased abdominal pain, distension and tenderness, an abdominal X-ray showing no dilated small bowel, and the appearance of flatus and defaecation. A liquid diet was then started, usually followed by a soft diet the next day, and solid food the day after. Patients were discharged when solid food was well tolerated. A long tube was inserted if there was no improvement. Patients who showed signs of persistent or worsening obstruction underwent surgery. All patients gave signed informed consent before undergoing therapy. The medical records of patients were reviewed, and outcome in the two groups was compared.
Statistical analysis Continuous data are expressed as mean(s.d.). Statistical analyses were carried out using Student’s t test, χ2 test and Fisher’s exact probability test, as appropriate. P < 0·050 was considered statistically significant. Analyses were performed using SPSS version 11 (IBM, Armonk, New York, USA). Results
A total of 305 patients with adhesive postoperative small bowel obstruction were treated. Some 142 patients received tube decompression therapy during the first 3 years, and 163 patients underwent HBO therapy during the last 3 years (Fig. 1). In total, there were 192 men and 113 April 2009 to March 2012 (HBO interval) Adhesive small bowel obstruction n = 163 HBO n = 163 With nasogastric tube n = 78
Nasogastric tube n = 62 n = 14 n = 48
n = 80
Long tube n = 94
n = 73
Improvement n = 121
Long tube n = 18
n = 143 n=8 Surgery n = 21
Improvement n = 151
n=2 n = 10 Surgery n = 12
Management of patients with adhesive small bowel obstruction in intervals before (April 2006 to March 2009) and after (April 2009 to March 2012) the introduction of hyperbaric oxygen (HBO) therapy
Fig. 1
2014 BJS Society Ltd Published by John Wiley & Sons Ltd
www.bjs.co.uk
BJS 2014; 101: 433–437
Hyperbaric oxygen therapy in adhesive small bowel obstruction
Table 1
435
Patient characteristics
Table 2 No HBO (n = 142)
Age (years)* 66(16) Sex ratio (M : F) 98 : 44 Region of previous surgery Upper abdomen 50 (35·2) Lower abdomen 50 (35·2) Upper and lower abdomen 42 (29·6) No. of previous operations 1 107 (75·4) 2 25 (17·6) ≥3 10 (7·0) Interval since last operation (months)* 163(169) Previous ASBO surgery 10 (7·0)
HBO (n = 163) 64(14) 94 : 69
P† 0·271‡ 0·748 0·224
44 (27·0) 71 (43·6) 48 (29·4) 0·002 93 (57·1) 56 (34·4) 14 (8·6) 153(170) 12 (7·4)
0·609‡ 0·914
Values in parentheses are percentages unless indicated otherwise; *values are mean(s.d.). HBO, hyperbaric oxygen therapy; ASBO, adhesive small bowel obstruction. †χ2 test, except ‡Student’s t test.
Gastrointestinal Colorectal (or appendicectomy) Hepatopancreatobiliary
No-HBO interval HBO interval
Gynaecological Urological Other > 1 operation 50 40 30 20 10 0 10 20 30 40 50 60 70 No. of patients
Type of previous operation that caused adhesive small bowel obstruction in intervals before (April 2006 to March 2009) and after (April 2009 to March 2012) the introduction of hyperbaric oxygen (HBO) therapy
Fig. 2
women with a mean age of 65(15) years. Some 94 patients had undergone upper abdominal surgery previously, 121 lower abdominal surgery, and 90 patients upper and lower abdominal surgery. One hundred and five patients had a history of more than one previous operation. The mean interval since the last operation was 157(169) months. Twenty-two patients had a history of adhesive postoperative small bowel obstruction before the present study (Table 1). Fig. 2 shows the types of previous surgery that caused obstruction. In the no-HBO group, 62 patients received a nasogastric tube and 94 patients a long tube (including 14 with nasogastric tube failure). A total of 21 patients required surgery for persistent or worsening signs of obstruction. 2014 BJS Society Ltd Published by John Wiley & Sons Ltd
Clinical outcomes
Time to oral intake (days)* Length of hospital stay (days)* Surgery
No HBO (n = 142)
HBO (n = 163)
P†
6·5(5·2) 14·1(11·3) 21 (14·8)
4·7(3·7) 10·3(6·9) 12 (7·4)
0·001 0·001 0·037‡
Values in parentheses are percentages unless indicated otherwise; *values are mean(s.d.). HBO, hyperbaric oxygen therapy. †Student’s t test, except ‡χ2 test.
In the HBO group, the median number of HBO treatments was 3 (range 1–7). Eleven patients (6·7 per cent) experienced mild earache, but there were no other complications. A total of 143 patients (87·7 per cent) were treated successfully with HBO without long-tube decompression. The group of patients who underwent HBO resumed oral intake significantly earlier (4·7(3·7) versus 6·5(5·2) days; P = 0·001) and had a significantly shorter hospital stay (10·3(6·9) versus 14·1(11·3) days); P = 0·001) than those treated without HBO. A significantly smaller proportion of patients in the HBO group required surgery (7·4 versus 14·8 per cent; P = 0·037) (Table 2). In the no-HBO group, adhesional small bowel resection was performed in nine patients and adhesiolysis in 11. One patient underwent small intestinal bypass owing to severe adhesions. In the HBO group, adhesional small bowel resection was done in four patients, and adhesiolysis in seven. The final patient had severe adhesions and required small intestinal bypass. According to the Dindo–Clavien system14 , surgical complications in the no-HBO group were grade I in 16 patients, grade II in four and grade IIIa (puncture of the abdominal abscess) in one. In the HBO group, 11 patients had grade I and one had grade II complications. Patients in both groups were discharged from hospital in good condition.
Discussion
Adhesive postoperative small bowel obstruction is one of the most common reasons for surgical admission. It is characterized by the presence of abdominal pain, vomiting, distension and constipation, and confirmed by imaging. The most important risk factors are the type of surgery and extent of peritoneal damage. Colonic and rectal procedures are associated with a high risk of adhesionrelated problems15 . In the present study, gastrointestinal surgery also commonly caused adhesive postoperative small bowel obstruction. www.bjs.co.uk
BJS 2014; 101: 433–437
436
Y. Fukami, Y. Kurumiya, K. Mizuno, E. Sekoguchi and S. Kobayashi
The risk of future readmission for adhesive small bowel obstruction increases with growing numbers of previous episodes of obstruction. Non-surgical management of the initial episode has been advocated as a risk factor for recurrence16 . For patients presenting without signs of strangulation, there is good evidence to support conservative management1 – 5 . Early decompression, with either a long tube or nasogastric tube, is beneficial in the initial management of adhesive postoperative small bowel obstruction. The role of water-soluble contrast agents has been evaluated recently1,2,17,18 . The results of a systematic review and meta-analysis19 support the diagnostic and therapeutic use of water-soluble contrast agent in adhesive small bowel obstruction. Various methods have been used to select patients with adhesive small bowel obstruction for either operative or conservative management. Abdominal ultrasonography and CT may improve the diagnostic accuracy for bowel strangulation, detecting the cause of obstruction as well as the presence of a closed loop20,21 . Several recent studies have focused on identifying predictive factors for failure of conservative management and the need for surgery. Sakakibara and colleagues6 reported on conservatively treated patients with adhesive small bowel obstruction, in whom the drainage volume through the long tube on day 3 (cut-off value 500 ml) was the indicator for surgery. Water-soluble contrast follow-through is also valuable in patients undergoing initial conservative management to rule out complete small bowel obstruction and to predict the need for surgery1 . Unnecessary surgery must be avoided by referring to the diagnostic image and by physical examination. Failure rates for conservative management (tube decompression or water-soluble contrast agent) are reported to range from 10 to 35 per cent19,22 – 24 . In the early part of the present series, when obstruction was managed by tube decompression, the operation rate was 14·8 per cent. HBO therapy significantly reduced the need for surgery, to 7·4 per cent. Previous studies9,10 have evaluated the impact of HBO therapy in various clinical situations, such as carbon monoxide poisoning, decompression sickness, arterial gas embolism, radiation-induced tissue injury, clostridial myonecrosis, necrotizing fasciitis, refractory osteomyelitis, acute traumatic ischaemic injury, compromised skin grafts and flaps, anaemia due to exceptional blood loss, thermal burns and problem wounds. HBO therapy involves the intermittent inhalation of 100 per cent oxygen under a pressure greater than 1 atmosphere absolute, typically between 2·0 and 3·0 atmospheres for periods between 60 and 120 min once or twice daily. It is possible to deliver a greatly increased pressure of oxygen to the
lungs, blood and tissues. Tissue swelling is most likely decreased through an osmotic effect of oxygen. According to Boyle’s law25 , the volume of intestinal gas is reduced when the environmental pressure increases. Oxygenation under high pressure enhances inert gas diffusion from the closed intestinal lumen into the blood. Relaxation of the distended intestinal loop improves the compromised microcirculation and oxygenation of hypoxic intestinal tissue, which leads to preservation of intestinal viability and recovery of motility13 . An experimental study26 showed that HBO ameliorates bacterial translocation in rats with mechanical intestinal obstruction. Chen and colleagues27 demonstrated the efficacy of HBO therapy in a rat peritoneal adhesion model. Abu-Asi and co-workers28 reported the value of HBO in treating recurrent acute bowel obstruction after previous pelvic radiotherapy. In the present study, HBO therapy significantly reduced the need for operation in patients with adhesive postoperative small bowel obstruction. HBO therapy was associated with earlier resumption of oral intake and a shorter hospital stay. HBO therapy is safe when used according to standard protocols. Potential side-effects include middle ear barotrauma, pulmonary and nervous system toxicity, visual changes, anxiety, euphoria and seizures9 . Here, 11 patients (6·7 per cent) developed mild earache in the HBO group, but no other complications were observed. It remains unclear whether any effect of HBO on small bowel obstruction is cellular (actually breaking up adhesions) or mechanical (general distension of the abdominal cavity leading to devolvement of bowel loops) in nature. Several limitations of this study must be acknowledged. This was a retrospective, non-randomized review conducted in a single institution. The no-HBO and HBO groups were recruited during consecutive, relatively short intervals (3 years each), possibly minimizing the heterogeneity of the measured variables. The magnitude of the differences in outcome was large and clinically significant. It was not possible to identify clear criteria for the success of conservative versus operative treatment of small bowel obstruction. Parameters predicting the recurrence of adhesive postoperative small bowel obstruction in patients managed with HBO remain unclear.
2014 BJS Society Ltd Published by John Wiley & Sons Ltd
www.bjs.co.uk
Disclosure
The authors declare no conflict of interest. References 1 Choi HK, Chu KW, Law WL. Therapeutic value of Gastrografin in adhesive small bowel obstruction after unsuccessful conservative treatment: a prospective randomized trial. Ann Surg 2002; 236: 1–6.
BJS 2014; 101: 433–437
Hyperbaric oxygen therapy in adhesive small bowel obstruction
2 Biondo S, Par´es D, Mora L, Mart´ı Ragu´e J, Kreisler E, Jaurrieta E. Randomized clinical study of Gastrografin administration in patients with adhesive small bowel obstruction. Br J Surg 2003; 90: 542–546. 3 Williams SB, Greenspon J, Young HA, Orkin BA. Small bowel obstruction: conservative vs. surgical management. Dis Colon Rectum 2005; 48: 1140–1146. 4 Ji ZL, Li JS, Yuan CW, Chen WD, Zhang YN, Ju XT et al. Therapeutic value of sesame oil in the treatment of adhesive small bowel obstruction. Am J Surg 2010; 199: 160–165. 5 Fleshner PR, Siegman MG, Slater GI, Brolin RE, Chandler JC, Aufses AH Jr. A prospective, randomized trial of short versus long tubes in adhesive small-bowel obstruction. Am J Surg 1995; 170: 366–370. 6 Sakakibara T, Harada A, Yaguchi T, Koike M, Fujiwara M, Kodera Y et al. The indicator for surgery in adhesive small bowel obstruction patient managed with long tube. Hepatogastroenterology 2007; 54: 787–790. 7 Foster NM, McGory ML, Zingmond DS, Ko CY. Small bowel obstruction: a population-based appraisal. J Am Coll Surg 2006; 203: 170–176. 8 Duron JJ, Silva NJ, du Montcel ST, Berger A, Muscari F, Hennet H et al. Adhesive postoperative small bowel obstruction: incidence and risk factors of recurrence after surgical treatment: a multicenter prospective study. Ann Surg 2006; 244: 750–757. 9 Tibbles PM, Edelsberg JS. Hyperbaric-oxygen therapy. N Engl J Med 1996; 334: 1642–1648. 10 Leach RM, Rees PJ, Wilmshurst P. Hyperbaric oxygen therapy. Br Med J 1998; 317: 1140–1143. 11 Hopkinson BR, Schenk WG Jr. Effect of hyperbaric oxygen on experimental intestinal obstruction. Arch Surg 1969; 98: 228–232. 12 Ohno Y, Kanematsu T. Hyperbaric oxygen therapy for intestinal obstruction in children: an exceptional experience in a compromised child. J Pediatr Surg 1998; 33: 1543–1545. 13 Ambiru S, Furuyama N, Kimura F, Shimizu H, Yoshidome H, Miyazaki M et al. Effect of hyperbaric oxygen therapy on patients with adhesive intestinal obstruction associated with abdominal surgery who have failed to respond to more than 7 days of conservative treatment. Hepatogastroenterology 2008; 55: 491–495. 14 Dindo D, Demartines N, Clavien PA. Classification of surgical complications: a new proposal with evaluation in a cohort of 6336 patients and results of a survey. Ann Surg 2004; 240: 205–213. 15 Parker MC, Ellis H, Moran BJ, Thompson JN, Wilson MS, Menzies D et al. Postoperative adhesions: ten-year follow-up
2014 BJS Society Ltd Published by John Wiley & Sons Ltd
437
16
17
18
19
20
21
22
23
24
25 26
27
28
of 12 584 patients undergoing lower abdominal surgery. Dis Colon Rectum 2001; 44: 822–829. Barkan H, Webster S, Ozeran S. Factors predicting the recurrence of adhesive small-bowel obstruction. Am J Surg 1995; 170: 361–365. Chen SC, Chang KJ, Lee PH, Wang SM, Chen KM, Lin FY. Oral Urografin in postoperative small bowel obstruction. World J Surg 1999; 23: 1051–1054. Farid M, Fikry A, El Nakeeb A, Fouda E, Elmetwally T, Yousef M et al. Clinical impacts of oral Gastrografin follow-through in adhesive small bowel obstruction (SBO). J Surg Res 2010; 162: 170–176. ¨ Branco BC, Barmparas G, Schnuriger B, Inaba K, Chan LS, Demetriades D. Systematic review and meta-analysis of the diagnostic and therapeutic role of water-soluble contrast agent in adhesive small bowel obstruction. Br J Surg 2010; 97: 470–478. Balthazar EJ, George W. Holmes Lecture. CT of small-bowel obstruction. AJR Am J Roentgenol 1994; 162: 255–261. Gazelle GS, Goldberg MA, Wittenberg J, Halpern EF, Pinkney L, Mueller PR. Efficacy of CT in distinguishing small-bowel obstruction from other causes of small-bowel dilatation. AJR Am J Roentgenol 1994; 162: 43–47. Sosa J, Gardner B. Management of patients diagnosed as acute intestinal obstruction secondary to adhesions. Am Surg 1993; 59: 125–128. Seror D, Feigin E, Szold A, Allweis TM, Carmon M, Nissan S et al. How conservatively can postoperative small bowel obstruction be treated? Am J Surg 1993; 165: 121–125. Assalia A, Schein M, Kopelman D, Hirshberg A, Hashmonai M. Therapeutic effect of oral Gastrografin in adhesive, partial small-bowel obstruction: a prospective randomized trial. Surgery 1994; 115: 433–437. West JB. The original presentation of Boyle’s law. J Appl Physiol 1999; 87: 1543–1545. Akin ML, Uluutku H, Erenoglu C, Ilicak EN, Elbuken E, Erdemoglu A et al. Hyperbaric oxygen ameliorates bacterial translocation in rats with mechanical intestinal obstruction. Dis Colon Rectum 2002; 45: 967–972. Chen MJ, Chen TY, Cheng YM, Hsu YC. The effect of postoperative hyperbaric oxygen treatment on intra-abdominal adhesions in rats. Int J Mol Sci 2012; 13: 12 224–12 231. Abu-Asi MJ, Andreyev HJ. The utility of hyperbaric oxygen therapy to treat recurrent acute bowel obstruction after previous pelvic radiotherapy: a case series. Support Care Cancer 2013; 21: 1797–1800.
www.bjs.co.uk
BJS 2014; 101: 433–437
438
Y. Fukami, Y. Kurumiya, K. Mizuno, E. Sekoguchi and S. Kobayashi
Commentary
Clinical effect of hyperbaric oxygen therapy in adhesive postoperative small bowel obstruction (Br J Surg 2014; 101: 433–437) Intra-abdominal adhesions are a major source of abdominal complaints and of readmission to surgical wards. Morbidity may range from minor, self-limiting, interval pains to a hostile abdomen, and even death in the case of untreated, strangulated loop obstruction. Surgery is a frequent cause, but intra-abdominal disease (such as endometriosis) and, increasingly, long-term effects after radiotherapy for malignancy may also be the source. In the postsurgical setting, a number of preventive measures including gels and films have been proposed to prevent adhesions1,2 , with only limited effects. Commonly perceived mechanisms of adhesion formation include peritoneal damage (by surgical trauma or other insults) giving rise to inflammation, thereby promoting procoagulant and antifibrinolytic reactions, and a subsequent significant increase in fibrin formation3 . When fibrin deposits persist, fibrinous adhesions can develop. Repeated surgery to resolve adhesions frequently results in new development of adhesions. A non-operative means of resolution is thus welcomed. The idea of using hyperbaric oxygen (HBO) to relieve bowel obstruction is not new4 , yet the clinical data are very limited. In the present before–after study, Fukami and colleagues demonstrated a reduction by half in the number of patients needing surgery. As has been demonstrated in a number of animal experiments4,5 , it appears that HBO also works in the clinical setting. Further clinical data concerning use of HBO to treat bowel obstruction due to radiation-induced fibrosis will emerge from the HOT II trial (ISRCTN 86894066). Although the present data may give a clinical clue that HBO works, it is crucial to find out why and how. Access to HBO remains limited in many hospitals, and a better understanding of the process of adhesion formation will allow the design of new preventive strategies and better non-operative treatment. K. Søreide Department of Gastrointestinal Surgery, Stavanger University Hospital, PO Box 8100, N-40368 Stavanger, Norway
(e-mail: [email protected]) DOI: 10.1002/bjs.9459
Disclosure
The author declares no conflict of interest. References 1 Chaturvedi AA, Lomme RM, Hendriks T, van Goor H. Prevention of postsurgical adhesions using an ultrapure alginate-based gel. Br J Surg 2013; 100: 904–910. 2 Lalountas M, Ballas KD, Michalakis A, Psarras K, Asteriou C, Giakoustidis DE et al. Postoperative adhesion prevention using a statin-containing cellulose film in an experimental model. Br J Surg 2012; 99: 423–429. 3 Hellebrekers BW, Kooistra T. Pathogenesis of postoperative adhesion formation. Br J Surg 2011; 98: 1503–1516. 4 Hopkinson BR, Schenk WG Jr. Effect of hyperbaric oxygen on experimental intestinal obstruction. Arch Surg 1969; 98: 228–232. 5 Chen MJ, Chen TY, Cheng YM, Hsu YC. The effect of postoperative hyperbaric oxygen treatment on intra-abdominal adhesions in rats. Int J Mol Sci 2012; 13: 12 224–12 231.
2014 BJS Society Ltd Published by John Wiley & Sons Ltd
www.bjs.co.uk
BJS 2014; 101: 438
Clinical effect of hyperbaric oxygen therapy in adhesive postoperative small bowel obstruction Y. Fukami, Y. Kurumiya, K. Mizuno, E. Sekoguchi and S. Kobayashi Department of Surgery, Toyota Kosei Hospital, 500-1 Josui-cho, Toyota, Aichi 470-0396, Japan Correspondence to: Dr Y. Fukami (e-mail: [email protected])
Background: Hyperbaric oxygen (HBO) therapy is a controversial treatment for adhesive postoperative
small bowel obstruction, with only a few small studies reported. The aim of this study was to assess the clinical value of HBO therapy in the treatment of adhesive postoperative small bowel obstruction. Methods: Between April 2006 and March 2012, all patients with adhesive postoperative small bowel obstruction were treated using either decompression therapy or HBO. Patients undergoing HBO therapy were treated once a day at a pressure of 2·0 atmospheres absolute and received 100 per cent oxygen. Patients showing no clinical and radiological improvement with HBO therapy were converted to decompression therapy by means of a long tube. Medical records were reviewed and outcomes analysed. Results: A total of 305 patients were treated, of whom 142 underwent tube decompression therapy during the first 3 years and the remaining 163 had HBO therapy during the last 3 years. The median number of HBO treatments was 3 (range 1–7). A total of 143 patients (87·7 per cent) were treated successfully with HBO without long-tube decompression. HBO therapy was associated with earlier resumption of oral intake (mean 4·7 versus 6·5 days; P = 0·001) and a shorter hospital stay (mean 10·3 versus 14·1 days; P = 0·001). The rate of operation was 7·4 per cent in the HBO group and 14·8 per cent in group treated by decompression alone (P = 0·037). Conclusion: In this study, HBO therapy was safe for the treatment of adhesive postoperative small bowel obstruction. It reduced the need for surgery and time to recovery as well as the hospital stay. Paper accepted 29 October 2013 Published online 3 February 2014 in Wiley Online Library (www.bjs.co.uk). DOI: 10.1002/bjs.9389
Introduction
Adhesive small bowel obstruction is a major cause of postoperative morbidity, and appropriate management using the proper diagnostic and therapeutic pathway is necessary. Immediate surgical intervention is required when strangulation is suspected. The management of incomplete adhesive small bowel obstruction remains controversial1 – 5 , and initial conservative management should be the choice in most patients. Long-tube decompression is one of the most common conservative treatments, and is successful in most patients5,6 . However, this treatment has become a significant socioeconomic burden because of the high rate of recurrence7,8 . To make matters worse, quality of life during treatment is poor, with symptoms such as sore nose and throat. Hyperbaric oxygen (HBO) therapy involves the intermittent inhalation of 100 per cent oxygen under a pressure greater than 1 atmosphere absolute, and has various beneficial physiological, cellular and biochemical effects9,10 . 2014 BJS Society Ltd Published by John Wiley & Sons Ltd
The impact of HBO therapy in various clinical situations has been evaluated in previous studies9 . Only a few human clinical trials11 – 13 have described the effect of HBO therapy for small bowel obstruction. The aim of the present study was to investigate the clinical value of HBO therapy in adhesive postoperative small bowel obstruction.
Methods
Between April 2006 and March 2012, all patients with adhesive postoperative small bowel obstruction were treated using either decompression therapy or HBO. The diagnostic criteria for adhesive postoperative small bowel obstruction included: a history of previous abdominal surgery more than 4 weeks previously; clinical symptoms and signs of mechanical obstruction, such as abdominal pain, vomiting, abdominal distension and constipation; and a plain abdominal X-ray taken with the patient upright BJS 2014; 101: 433–437
434
Y. Fukami, Y. Kurumiya, K. Mizuno, E. Sekoguchi and S. Kobayashi
and routine computed tomography (CT) showing dilated loops of small intestine, and air–fluid levels and air in the distal small bowel/colon. Emergency abdominal exploration was undertaken in patients with suspected strangulation or peritonitis, and such patients were excluded from the present study. In patients with a history of surgery for cancer, recurrence was ruled out by routine examinations (clinical examination, measurement of tumour marker levels, ultrasonography and CT). When HBO became available, further exclusion criteria were: pregnancy, pneumothorax, emphysema and sinusitis.
Management plan The authors’ conservative strategy for management of adhesive postoperative small bowel obstruction changed after April 2009. In the early part of the study (from April 2006 to March 2009), management comprised no oral intake, administration of intravenous fluids with electrolytes (as nutrition), and insertion of a nasogastric tube until there was clinical improvement. When the small bowel was shown to be markedly dilated by CT, a long tube was inserted for immediate decompression. In the late period (from April 2009 to March 2012), there was no oral intake, intravenous fluids with electrolytes were administered (as nutrition) and HBO therapy was performed within 24 h of admission. A nasogastric tube was inserted if the patient was vomiting. Patients undergoing HBO therapy were treated once a day, up to seven times until improvement was observed, in a single hyperbaric chamber (BARA-MED; Environmental Tectonics Corporation, Southampton, Pennsylvania, USA) at a pressure of 2·0 atmospheres April 2006 to March 2009 (no-HBO interval) Adhesive small bowel obstruction n = 142
absolute with 100 per cent oxygen. The sessions started with 15 min of compression to 2·0 atmospheres and lasted 90 min, ending with 15 min of decompression to 1·0 atmosphere. Clinical improvement was defined by the presence of decreased abdominal pain, distension and tenderness, an abdominal X-ray showing no dilated small bowel, and the appearance of flatus and defaecation. A liquid diet was then started, usually followed by a soft diet the next day, and solid food the day after. Patients were discharged when solid food was well tolerated. A long tube was inserted if there was no improvement. Patients who showed signs of persistent or worsening obstruction underwent surgery. All patients gave signed informed consent before undergoing therapy. The medical records of patients were reviewed, and outcome in the two groups was compared.
Statistical analysis Continuous data are expressed as mean(s.d.). Statistical analyses were carried out using Student’s t test, χ2 test and Fisher’s exact probability test, as appropriate. P < 0·050 was considered statistically significant. Analyses were performed using SPSS version 11 (IBM, Armonk, New York, USA). Results
A total of 305 patients with adhesive postoperative small bowel obstruction were treated. Some 142 patients received tube decompression therapy during the first 3 years, and 163 patients underwent HBO therapy during the last 3 years (Fig. 1). In total, there were 192 men and 113 April 2009 to March 2012 (HBO interval) Adhesive small bowel obstruction n = 163 HBO n = 163 With nasogastric tube n = 78
Nasogastric tube n = 62 n = 14 n = 48
n = 80
Long tube n = 94
n = 73
Improvement n = 121
Long tube n = 18
n = 143 n=8 Surgery n = 21
Improvement n = 151
n=2 n = 10 Surgery n = 12
Management of patients with adhesive small bowel obstruction in intervals before (April 2006 to March 2009) and after (April 2009 to March 2012) the introduction of hyperbaric oxygen (HBO) therapy
Fig. 1
2014 BJS Society Ltd Published by John Wiley & Sons Ltd
www.bjs.co.uk
BJS 2014; 101: 433–437
Hyperbaric oxygen therapy in adhesive small bowel obstruction
Table 1
435
Patient characteristics
Table 2 No HBO (n = 142)
Age (years)* 66(16) Sex ratio (M : F) 98 : 44 Region of previous surgery Upper abdomen 50 (35·2) Lower abdomen 50 (35·2) Upper and lower abdomen 42 (29·6) No. of previous operations 1 107 (75·4) 2 25 (17·6) ≥3 10 (7·0) Interval since last operation (months)* 163(169) Previous ASBO surgery 10 (7·0)
HBO (n = 163) 64(14) 94 : 69
P† 0·271‡ 0·748 0·224
44 (27·0) 71 (43·6) 48 (29·4) 0·002 93 (57·1) 56 (34·4) 14 (8·6) 153(170) 12 (7·4)
0·609‡ 0·914
Values in parentheses are percentages unless indicated otherwise; *values are mean(s.d.). HBO, hyperbaric oxygen therapy; ASBO, adhesive small bowel obstruction. †χ2 test, except ‡Student’s t test.
Gastrointestinal Colorectal (or appendicectomy) Hepatopancreatobiliary
No-HBO interval HBO interval
Gynaecological Urological Other > 1 operation 50 40 30 20 10 0 10 20 30 40 50 60 70 No. of patients
Type of previous operation that caused adhesive small bowel obstruction in intervals before (April 2006 to March 2009) and after (April 2009 to March 2012) the introduction of hyperbaric oxygen (HBO) therapy
Fig. 2
women with a mean age of 65(15) years. Some 94 patients had undergone upper abdominal surgery previously, 121 lower abdominal surgery, and 90 patients upper and lower abdominal surgery. One hundred and five patients had a history of more than one previous operation. The mean interval since the last operation was 157(169) months. Twenty-two patients had a history of adhesive postoperative small bowel obstruction before the present study (Table 1). Fig. 2 shows the types of previous surgery that caused obstruction. In the no-HBO group, 62 patients received a nasogastric tube and 94 patients a long tube (including 14 with nasogastric tube failure). A total of 21 patients required surgery for persistent or worsening signs of obstruction. 2014 BJS Society Ltd Published by John Wiley & Sons Ltd
Clinical outcomes
Time to oral intake (days)* Length of hospital stay (days)* Surgery
No HBO (n = 142)
HBO (n = 163)
P†
6·5(5·2) 14·1(11·3) 21 (14·8)
4·7(3·7) 10·3(6·9) 12 (7·4)
0·001 0·001 0·037‡
Values in parentheses are percentages unless indicated otherwise; *values are mean(s.d.). HBO, hyperbaric oxygen therapy. †Student’s t test, except ‡χ2 test.
In the HBO group, the median number of HBO treatments was 3 (range 1–7). Eleven patients (6·7 per cent) experienced mild earache, but there were no other complications. A total of 143 patients (87·7 per cent) were treated successfully with HBO without long-tube decompression. The group of patients who underwent HBO resumed oral intake significantly earlier (4·7(3·7) versus 6·5(5·2) days; P = 0·001) and had a significantly shorter hospital stay (10·3(6·9) versus 14·1(11·3) days); P = 0·001) than those treated without HBO. A significantly smaller proportion of patients in the HBO group required surgery (7·4 versus 14·8 per cent; P = 0·037) (Table 2). In the no-HBO group, adhesional small bowel resection was performed in nine patients and adhesiolysis in 11. One patient underwent small intestinal bypass owing to severe adhesions. In the HBO group, adhesional small bowel resection was done in four patients, and adhesiolysis in seven. The final patient had severe adhesions and required small intestinal bypass. According to the Dindo–Clavien system14 , surgical complications in the no-HBO group were grade I in 16 patients, grade II in four and grade IIIa (puncture of the abdominal abscess) in one. In the HBO group, 11 patients had grade I and one had grade II complications. Patients in both groups were discharged from hospital in good condition.
Discussion
Adhesive postoperative small bowel obstruction is one of the most common reasons for surgical admission. It is characterized by the presence of abdominal pain, vomiting, distension and constipation, and confirmed by imaging. The most important risk factors are the type of surgery and extent of peritoneal damage. Colonic and rectal procedures are associated with a high risk of adhesionrelated problems15 . In the present study, gastrointestinal surgery also commonly caused adhesive postoperative small bowel obstruction. www.bjs.co.uk
BJS 2014; 101: 433–437
436
Y. Fukami, Y. Kurumiya, K. Mizuno, E. Sekoguchi and S. Kobayashi
The risk of future readmission for adhesive small bowel obstruction increases with growing numbers of previous episodes of obstruction. Non-surgical management of the initial episode has been advocated as a risk factor for recurrence16 . For patients presenting without signs of strangulation, there is good evidence to support conservative management1 – 5 . Early decompression, with either a long tube or nasogastric tube, is beneficial in the initial management of adhesive postoperative small bowel obstruction. The role of water-soluble contrast agents has been evaluated recently1,2,17,18 . The results of a systematic review and meta-analysis19 support the diagnostic and therapeutic use of water-soluble contrast agent in adhesive small bowel obstruction. Various methods have been used to select patients with adhesive small bowel obstruction for either operative or conservative management. Abdominal ultrasonography and CT may improve the diagnostic accuracy for bowel strangulation, detecting the cause of obstruction as well as the presence of a closed loop20,21 . Several recent studies have focused on identifying predictive factors for failure of conservative management and the need for surgery. Sakakibara and colleagues6 reported on conservatively treated patients with adhesive small bowel obstruction, in whom the drainage volume through the long tube on day 3 (cut-off value 500 ml) was the indicator for surgery. Water-soluble contrast follow-through is also valuable in patients undergoing initial conservative management to rule out complete small bowel obstruction and to predict the need for surgery1 . Unnecessary surgery must be avoided by referring to the diagnostic image and by physical examination. Failure rates for conservative management (tube decompression or water-soluble contrast agent) are reported to range from 10 to 35 per cent19,22 – 24 . In the early part of the present series, when obstruction was managed by tube decompression, the operation rate was 14·8 per cent. HBO therapy significantly reduced the need for surgery, to 7·4 per cent. Previous studies9,10 have evaluated the impact of HBO therapy in various clinical situations, such as carbon monoxide poisoning, decompression sickness, arterial gas embolism, radiation-induced tissue injury, clostridial myonecrosis, necrotizing fasciitis, refractory osteomyelitis, acute traumatic ischaemic injury, compromised skin grafts and flaps, anaemia due to exceptional blood loss, thermal burns and problem wounds. HBO therapy involves the intermittent inhalation of 100 per cent oxygen under a pressure greater than 1 atmosphere absolute, typically between 2·0 and 3·0 atmospheres for periods between 60 and 120 min once or twice daily. It is possible to deliver a greatly increased pressure of oxygen to the
lungs, blood and tissues. Tissue swelling is most likely decreased through an osmotic effect of oxygen. According to Boyle’s law25 , the volume of intestinal gas is reduced when the environmental pressure increases. Oxygenation under high pressure enhances inert gas diffusion from the closed intestinal lumen into the blood. Relaxation of the distended intestinal loop improves the compromised microcirculation and oxygenation of hypoxic intestinal tissue, which leads to preservation of intestinal viability and recovery of motility13 . An experimental study26 showed that HBO ameliorates bacterial translocation in rats with mechanical intestinal obstruction. Chen and colleagues27 demonstrated the efficacy of HBO therapy in a rat peritoneal adhesion model. Abu-Asi and co-workers28 reported the value of HBO in treating recurrent acute bowel obstruction after previous pelvic radiotherapy. In the present study, HBO therapy significantly reduced the need for operation in patients with adhesive postoperative small bowel obstruction. HBO therapy was associated with earlier resumption of oral intake and a shorter hospital stay. HBO therapy is safe when used according to standard protocols. Potential side-effects include middle ear barotrauma, pulmonary and nervous system toxicity, visual changes, anxiety, euphoria and seizures9 . Here, 11 patients (6·7 per cent) developed mild earache in the HBO group, but no other complications were observed. It remains unclear whether any effect of HBO on small bowel obstruction is cellular (actually breaking up adhesions) or mechanical (general distension of the abdominal cavity leading to devolvement of bowel loops) in nature. Several limitations of this study must be acknowledged. This was a retrospective, non-randomized review conducted in a single institution. The no-HBO and HBO groups were recruited during consecutive, relatively short intervals (3 years each), possibly minimizing the heterogeneity of the measured variables. The magnitude of the differences in outcome was large and clinically significant. It was not possible to identify clear criteria for the success of conservative versus operative treatment of small bowel obstruction. Parameters predicting the recurrence of adhesive postoperative small bowel obstruction in patients managed with HBO remain unclear.
2014 BJS Society Ltd Published by John Wiley & Sons Ltd
www.bjs.co.uk
Disclosure
The authors declare no conflict of interest. References 1 Choi HK, Chu KW, Law WL. Therapeutic value of Gastrografin in adhesive small bowel obstruction after unsuccessful conservative treatment: a prospective randomized trial. Ann Surg 2002; 236: 1–6.
BJS 2014; 101: 433–437
Hyperbaric oxygen therapy in adhesive small bowel obstruction
2 Biondo S, Par´es D, Mora L, Mart´ı Ragu´e J, Kreisler E, Jaurrieta E. Randomized clinical study of Gastrografin administration in patients with adhesive small bowel obstruction. Br J Surg 2003; 90: 542–546. 3 Williams SB, Greenspon J, Young HA, Orkin BA. Small bowel obstruction: conservative vs. surgical management. Dis Colon Rectum 2005; 48: 1140–1146. 4 Ji ZL, Li JS, Yuan CW, Chen WD, Zhang YN, Ju XT et al. Therapeutic value of sesame oil in the treatment of adhesive small bowel obstruction. Am J Surg 2010; 199: 160–165. 5 Fleshner PR, Siegman MG, Slater GI, Brolin RE, Chandler JC, Aufses AH Jr. A prospective, randomized trial of short versus long tubes in adhesive small-bowel obstruction. Am J Surg 1995; 170: 366–370. 6 Sakakibara T, Harada A, Yaguchi T, Koike M, Fujiwara M, Kodera Y et al. The indicator for surgery in adhesive small bowel obstruction patient managed with long tube. Hepatogastroenterology 2007; 54: 787–790. 7 Foster NM, McGory ML, Zingmond DS, Ko CY. Small bowel obstruction: a population-based appraisal. J Am Coll Surg 2006; 203: 170–176. 8 Duron JJ, Silva NJ, du Montcel ST, Berger A, Muscari F, Hennet H et al. Adhesive postoperative small bowel obstruction: incidence and risk factors of recurrence after surgical treatment: a multicenter prospective study. Ann Surg 2006; 244: 750–757. 9 Tibbles PM, Edelsberg JS. Hyperbaric-oxygen therapy. N Engl J Med 1996; 334: 1642–1648. 10 Leach RM, Rees PJ, Wilmshurst P. Hyperbaric oxygen therapy. Br Med J 1998; 317: 1140–1143. 11 Hopkinson BR, Schenk WG Jr. Effect of hyperbaric oxygen on experimental intestinal obstruction. Arch Surg 1969; 98: 228–232. 12 Ohno Y, Kanematsu T. Hyperbaric oxygen therapy for intestinal obstruction in children: an exceptional experience in a compromised child. J Pediatr Surg 1998; 33: 1543–1545. 13 Ambiru S, Furuyama N, Kimura F, Shimizu H, Yoshidome H, Miyazaki M et al. Effect of hyperbaric oxygen therapy on patients with adhesive intestinal obstruction associated with abdominal surgery who have failed to respond to more than 7 days of conservative treatment. Hepatogastroenterology 2008; 55: 491–495. 14 Dindo D, Demartines N, Clavien PA. Classification of surgical complications: a new proposal with evaluation in a cohort of 6336 patients and results of a survey. Ann Surg 2004; 240: 205–213. 15 Parker MC, Ellis H, Moran BJ, Thompson JN, Wilson MS, Menzies D et al. Postoperative adhesions: ten-year follow-up
2014 BJS Society Ltd Published by John Wiley & Sons Ltd
437
16
17
18
19
20
21
22
23
24
25 26
27
28
of 12 584 patients undergoing lower abdominal surgery. Dis Colon Rectum 2001; 44: 822–829. Barkan H, Webster S, Ozeran S. Factors predicting the recurrence of adhesive small-bowel obstruction. Am J Surg 1995; 170: 361–365. Chen SC, Chang KJ, Lee PH, Wang SM, Chen KM, Lin FY. Oral Urografin in postoperative small bowel obstruction. World J Surg 1999; 23: 1051–1054. Farid M, Fikry A, El Nakeeb A, Fouda E, Elmetwally T, Yousef M et al. Clinical impacts of oral Gastrografin follow-through in adhesive small bowel obstruction (SBO). J Surg Res 2010; 162: 170–176. ¨ Branco BC, Barmparas G, Schnuriger B, Inaba K, Chan LS, Demetriades D. Systematic review and meta-analysis of the diagnostic and therapeutic role of water-soluble contrast agent in adhesive small bowel obstruction. Br J Surg 2010; 97: 470–478. Balthazar EJ, George W. Holmes Lecture. CT of small-bowel obstruction. AJR Am J Roentgenol 1994; 162: 255–261. Gazelle GS, Goldberg MA, Wittenberg J, Halpern EF, Pinkney L, Mueller PR. Efficacy of CT in distinguishing small-bowel obstruction from other causes of small-bowel dilatation. AJR Am J Roentgenol 1994; 162: 43–47. Sosa J, Gardner B. Management of patients diagnosed as acute intestinal obstruction secondary to adhesions. Am Surg 1993; 59: 125–128. Seror D, Feigin E, Szold A, Allweis TM, Carmon M, Nissan S et al. How conservatively can postoperative small bowel obstruction be treated? Am J Surg 1993; 165: 121–125. Assalia A, Schein M, Kopelman D, Hirshberg A, Hashmonai M. Therapeutic effect of oral Gastrografin in adhesive, partial small-bowel obstruction: a prospective randomized trial. Surgery 1994; 115: 433–437. West JB. The original presentation of Boyle’s law. J Appl Physiol 1999; 87: 1543–1545. Akin ML, Uluutku H, Erenoglu C, Ilicak EN, Elbuken E, Erdemoglu A et al. Hyperbaric oxygen ameliorates bacterial translocation in rats with mechanical intestinal obstruction. Dis Colon Rectum 2002; 45: 967–972. Chen MJ, Chen TY, Cheng YM, Hsu YC. The effect of postoperative hyperbaric oxygen treatment on intra-abdominal adhesions in rats. Int J Mol Sci 2012; 13: 12 224–12 231. Abu-Asi MJ, Andreyev HJ. The utility of hyperbaric oxygen therapy to treat recurrent acute bowel obstruction after previous pelvic radiotherapy: a case series. Support Care Cancer 2013; 21: 1797–1800.
www.bjs.co.uk
BJS 2014; 101: 433–437
438
Y. Fukami, Y. Kurumiya, K. Mizuno, E. Sekoguchi and S. Kobayashi
Commentary
Clinical effect of hyperbaric oxygen therapy in adhesive postoperative small bowel obstruction (Br J Surg 2014; 101: 433–437) Intra-abdominal adhesions are a major source of abdominal complaints and of readmission to surgical wards. Morbidity may range from minor, self-limiting, interval pains to a hostile abdomen, and even death in the case of untreated, strangulated loop obstruction. Surgery is a frequent cause, but intra-abdominal disease (such as endometriosis) and, increasingly, long-term effects after radiotherapy for malignancy may also be the source. In the postsurgical setting, a number of preventive measures including gels and films have been proposed to prevent adhesions1,2 , with only limited effects. Commonly perceived mechanisms of adhesion formation include peritoneal damage (by surgical trauma or other insults) giving rise to inflammation, thereby promoting procoagulant and antifibrinolytic reactions, and a subsequent significant increase in fibrin formation3 . When fibrin deposits persist, fibrinous adhesions can develop. Repeated surgery to resolve adhesions frequently results in new development of adhesions. A non-operative means of resolution is thus welcomed. The idea of using hyperbaric oxygen (HBO) to relieve bowel obstruction is not new4 , yet the clinical data are very limited. In the present before–after study, Fukami and colleagues demonstrated a reduction by half in the number of patients needing surgery. As has been demonstrated in a number of animal experiments4,5 , it appears that HBO also works in the clinical setting. Further clinical data concerning use of HBO to treat bowel obstruction due to radiation-induced fibrosis will emerge from the HOT II trial (ISRCTN 86894066). Although the present data may give a clinical clue that HBO works, it is crucial to find out why and how. Access to HBO remains limited in many hospitals, and a better understanding of the process of adhesion formation will allow the design of new preventive strategies and better non-operative treatment. K. Søreide Department of Gastrointestinal Surgery, Stavanger University Hospital, PO Box 8100, N-40368 Stavanger, Norway
(e-mail: [email protected]) DOI: 10.1002/bjs.9459
Disclosure
The author declares no conflict of interest. References 1 Chaturvedi AA, Lomme RM, Hendriks T, van Goor H. Prevention of postsurgical adhesions using an ultrapure alginate-based gel. Br J Surg 2013; 100: 904–910. 2 Lalountas M, Ballas KD, Michalakis A, Psarras K, Asteriou C, Giakoustidis DE et al. Postoperative adhesion prevention using a statin-containing cellulose film in an experimental model. Br J Surg 2012; 99: 423–429. 3 Hellebrekers BW, Kooistra T. Pathogenesis of postoperative adhesion formation. Br J Surg 2011; 98: 1503–1516. 4 Hopkinson BR, Schenk WG Jr. Effect of hyperbaric oxygen on experimental intestinal obstruction. Arch Surg 1969; 98: 228–232. 5 Chen MJ, Chen TY, Cheng YM, Hsu YC. The effect of postoperative hyperbaric oxygen treatment on intra-abdominal adhesions in rats. Int J Mol Sci 2012; 13: 12 224–12 231.
2014 BJS Society Ltd Published by John Wiley & Sons Ltd
www.bjs.co.uk
BJS 2014; 101: 438
