Incidence of perioperative adverse events in obese children undergoing elective general surgery

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1 British Journal of Anaesthesia 106 (3): (2011) Advance Access publication 10 December doi: /bja/aeq368 Incidence of perioperative adverse events in obese children undergoing elective general surgery S. El-Metainy 1 *, T. Ghoneim 1, E. Aridae 1 and M. Abdel Wahab 2 1 Department of Anaesthesia, Faculty of Medicine and 2 Department of Biostatistics, High Institute of Public Health, University of Alexandria, Alexandria, Egypt * Corresponding author. shelmetainy@yahoo.com Editor s key points The prevalence of obesity is increasing in both adults and children of developed and developing countries. Associations between obesity and perioperative complications were assessed in a prospective cohort study of 1456 children in Egypt. There were significant associations between obesity and a number of adverse respiratory events, including difficult mask ventilation, airway obstruction, bronchospasm, and haemoglobin oxygen desaturation. Background. A worldwide increase in the prevalence of obesity has been observed in both developed and developing countries. Few studies have addressed the anaesthetic or perioperative implications of childhood obesity. Methods. Children aged 2 16 yr undergoing general surgery were classified using age- and sex-adjusted BMI. Patient characteristic, co-morbidity, and perioperative data were collected to ascertain the risks associated with overweight and obese children. Results. We enrolled 1465 subjects in our study, of which 154 (10.5%) were classified as obese and a further 223 (15.2%) as overweight. After adjusting for age, we identified increased rates of arterial haemoglobin desaturation, difficult mask ventilation, airway obstruction, and bronchospasm in obese children. The relative risk (RR) of adverse respiratory events was higher among obese subjects than non-obese subjects and higher in younger age groups. Controlling for age, adjusted-rr (confidence interval) was 1.49 ( ). There was a significant association between obesity and asthma with a higher odds ratio (OR) in younger age groups controlling for age: adjusted-or¼1.8 ( ). A significant association was detected between obesity and sleep apnoea controlling for age: adjusted-or¼4.03 ( ). Conclusions. These results suggest an increased incidence of perioperative adverse respiratory events in obese children, especially at younger ages. Keywords: anaesthesia; body mass index; childhood obesity; perioperative complications; surgery Accepted for publication: 10 November 2010 A worldwide increase in the prevalence of obesity has been observed in both developed and developing countries. 1 Furthermore, childhood obesity is associated with a number of medical co-morbidities, including asthma, hyperlipidaemia, obstructive sleep apnoea (OSA), hypertension, and adult heart disease. 2 Published information regarding the anaesthetic and perioperative implications of childhood obesity is sparse, and is mostly based on data from adult studies. 3 5 From the anaesthesiologist s point of view, caring for an obese child means dealing with early manifestations of the co-morbidities of adult obesity and sometimes dealing with new surgical procedures (bariatric surgery). There are few data regarding outcome in obese children undergoing anaesthesia and surgery. Two retrospective studies have been performed in children. 67 A previous prospective study suggests that obese children presenting for elective surgical procedures have a greater prevalence of pre-existing co-morbid medical conditions and an increased incidence of perioperative adverse respiratory events compared with normalweight children. 8 This study was designed to prospectively examine the relationship between childhood obesity and perioperative adverse events in children undergoing elective general surgery. Methods After the approval of the ethics committee, all children aged 2 16 yr undergoing elective general surgical procedures (inguinal hernia, hypospadias, umbilical hernia, undescended testes, and excision of dermoid cysts, lipoma, or haemangioma) were included in this prospective cohort study over a period of 2 yr (2007 8). The study site was the paediatric theatre with four operating theatres at Alexandria University Hospital. Preoperative height and weight were used to calculate BMI. BMI (kg m 22 ) is used to classify weight in adults: a BMI of 25 or more as overweight, 30 or more as obese, and 40 or more as morbidly obese. BMI, however, cannot be used as such in paediatric patients because of growth, body shape, or bone density changes occurring at puberty & The Author [2010]. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please journals.permissions@oup.com

2 El-Metainy et al. Table 1 Patient characteristic data, clinical characteristics, ASA status, co-morbidities, and preoperative airway assessments of obese (O) and non-obese (N) subjects. Data are represented as n (%), mean (SD). * and ** significant difference between obese and non-obese for this age group at 95% confidence limits (CL) and 99% CL, respectively N(n5287) O (n523) N (n5611) O (n534) N (n5252) O (n575) N (n5161) O (n522) Males [n (%)] 186 (64.8) 16 (69.6) 403 (66) 23 (67.6) 169 (67.1) 51 (68) 107 (66.5) 15 (68.2) Females [n (%)] 101 (35.2) 7 (30.4) 208 (34) 11 (32.4) 83 (32.9) 24 (32) 54 (33.5) 7 (31.8) Height (m) 0.84 (0.2) 0.89 (0.26) 1.07 (0.42) 1.11 (0.36) 1.3 (0.21) 1.35 (0.31) 1.56 (0.33) 1.67 (0.21) Weight (kg) 12.5 (6.2) 21.4 (4.5)** 19.2 (8.1) 35.3 (8.4)** 31.1 (4.2) 56.2 (9.1)** 47.6 (12.4) 87.6 (8.1)** BMI (kg m 22 ) 17.8 (2.2) 27.8 (4.2)** (3.2) 29.1 (3.4)** (1.3) 31.1 (3.4)** (3.3) 32.2 (4.4)** Duration of anaesthesia 81.5 (5.7) 86.7 (4.4) 80.2 (7.2) 87.9 (5.1) 80.6 (4.6) 82.3 (6.4) 80.5 (2.9) 89.8 (4) (min) PACU stay (min) 92.4 (2.8) 93.8 (4.0) 91.3 (6.3) 94.7 (5.1) 91.8 (4.2) 98.2 (3.0) 95.9 (2.2) 96.3 (2.4) ASA status Class I 201 (70) 13 (56.5)** 426 (69.7) 19 (55.8)** 177 (70.6) 42 (56.6)** 113 (70.1) 12 (54.4)** Class II 73 (25.4) 6 (26.0) 151 (24.7) 8 (23.6) 62 (24.6) 18 (24.0) 41 (25.4) 6 (27.3) Class III 14 (4.9) 5 (21.7)** 32 (5.2) 6 (17.6)** 12 (4.7) 14 (18.7)** 8 (4.9) 4 (18.1)** Medical co-morbidity Hypertension 3 (1.0) 1 (4.3) 6 (0.9) 1 (2.9) 3 (1.2) 0 3 (1.8) 1 (4.6) Asthma 41 (14.3) 6 (26.1)* 85 (13.9) 8 (23.5)* 34 (13.5) 16 (21.3)* 21 (13.0) 4 (18.2)* Diabetes mellitus II (2.9) 1 (1.3) 2 (2.6) 0 1 (2.4) Sleep apnoea 15 (5.2) 5 (21.7)* 34 (5.6) 6 (17.6)* 12 (4.8) 13 (17.3)* 10 (6.2) 4 (18.2)* Mallampati score I 233 (81.2) 14 (60.9)** 497 (81.3) 21 (61.7)** 201 (79.8) 45 (60)** 129 (80.1) 13 (59.1)** II 49 (17.1) 5 (20.7) 106 (17.3) 8 (21.8) 45 (17.8) 17 (22.7) 29 (18.0) 6 (27.3) III 4 (1.4) 4 (17.3)** 7 (1.2) 5 (14.7)* 5 (1.9) 13 (17.3)** 2 (1.2) 3 (13.6)* IV 1 (4.3) 0 1 (2.9) 0 1 (0.4) 0 1 (4.5) 0 Table 2 Comparison of anaesthetic care between obese (O) and non-obese (N) subjects. Data are represented as n (%). * and ** significant difference between obese and non-obese for this age group at 95% CL and 99% CL, respectively N O N O N O N O Induction methods Inhalation 215 (74.9) 14 (60.9)* 458 (74.9) 20 (58.8)* 191 (75.8) 45 (60.0)* 123 (75.0) 13 (59.1)* I.V. 71 (24.7) 10 (43.5)* 153 (25.1) 14 (41.2)* 62 (24.6) 30 (40.0)* 39 (24.2) 8 (36.4)* I.V. in non-intubated 25 (8.7) 0 (0)* 52 (8.5) 2 (5.9) 25 (9.9) 2 (2.7) 16 (9.9) 1 (4.5) Rapid sequence induction 5 (1.7) 2 (6.7) 9 (1.5) 3 (8.8) 3 (1.2) 5 (6.7) 2 (1.2) 2 (9.1)* Maintenance methods Face mask 18 (6.3) 2 (7.7) 37 (4.9) 2 (5.9) 15 (5.9) 4 (5.3) 9 (5.6) 1 (4.5) Laryngeal mask 228 (79.4) 10 (43.5)* 485 (79.4) 15 (44.1)* 201 (79.8) 34 (45.3)* 129 (80.0) 10 (45.5)* Tracheal intubation 41 (14.3) 12 (57.1)** 88 (14.4) 17 (48.6)** 36 (14.3) 38 (50.7)** 24 (14.9) 11 (50.0)** Caudal block 172 (59.9) 7 (30.4)* 370 (60.5) 10 (29.4)* 152 (60.3) 23 (30.7)* 97 (60.2) 6 (27.3)* Controlled ventilation 57 (19.9) 12 (52.2)* 122 (20.0) 18 (52.9)* 51 (20.2) 40 (53.3)* 32 (19.9) 11 (50.0)* and differences in the distribution of muscle and fat. Specific growth curves showing the percentiles for BMI according to sex and age have been used. 9 Accordingly, subjects were classified as obese, overweight, and normal weight. The following data were collected from patient files: patient characteristics, airway examination, duration of surgery, and medical co-morbidities. Data regarding the incidence and severity of respiratory complications were recorded throughout the perioperative period by the anaesthesia provider of each case. Significant desaturation was defined by any recorded intraoperative Sp O2 value,90%. Upper airway obstruction was defined as the requirement of oral airway 360

3 Respiratory events in obese children to maintain airway patency, and difficult mask ventilation (measured using a four-point scale according to Han and colleagues) was recorded. 10 Difficult laryngoscopy was defined as grade 2 according to Cormack and Lehane. 11 Bronchospasm was detected as auscultated wheezing, and multiple laryngoscopy attempts were noted. Paediatric anaesthetists supervised all procedures. Standard monitors were applied to all subjects, although the anaesthetic management of each subject was up to the individual anaesthesia provider. Anaesthetists were asked if they had changed their anaesthetic plan because the child was obese. Other complications, including postoperative nausea and vomiting, aspiration, and unplanned hospital admission, were noted. We excluded children with secondary causes of obesity from the study. Children with laryngo-tracheomalacia and neuromuscular disorders were also excluded. Statistical analysis Statistical analysis was performed using the PAST software package ( issue1_01.htm). Statistical significance was set at a confidence interval (CI) of 95%. Summary statistics are presented as arithmetic mean (standard deviation), except for frequency and per cent. Comparisons between obese and nonobese subjects within each age group stratum were done using Student s t-test for quantitative variables and z-test of proportion for categorical variables. Effect measures were calculated in the form of odds ratio (OR) for studying the association between obesity and medical co-morbidities, and relative risk (RR) for the occurrence of Mallampati airway classification and the incidence of any respiratory event. The Mantel Haenszel test was used to calculate the pooled effect measures controlling for age (after concluding that neither confounding nor interaction was detected as an effect of age, the age-adjusted values were used). Statistical significance was defined as P Results We studied 1465 children, of whom 154 (10.5%) were obese, 223 (15.2%) were overweight, and 1088 (74.3%) were normal weight. Preliminary analysis of the data showed that normalweight and overweight children behaved similarly with regard to the incidence of complications. We decided to restrict our analysis to two groups only: obese and non-obese (normal and overweight combined). The characteristics of the study subjects are presented in Table 1. The control group is significantly larger than the obese group. Therefore, we decided to age match the subjects of the obese group with those of the control group to make direct comparisons between the two groups. Age was categorized into four strata, and then obese and non-obese subjects were compared within each age group. No significant differences were observed between obese and non-obese subjects with regard to sex, duration of anaesthesia, or PACU stay. Table 1 also shows the ASA status, medical co-morbidities, and preoperative airway assessment for each cohort. Nonobese subjects were significantly healthier (ASA class I) than obese subjects in all four age groups. Obese children showed a significantly higher prevalence of coexisting conditions, especially asthma and sleep apnoea. Obese children were less likely to be classified as Mallampati I compared with non-obese children and the incidence of Mallampati III classification was significantly more common in obese subjects than non-obese subjects in all age classes. The airway and anaesthetic techniques used are presented in Table 2. Approximately 36% of anaesthesiologists caring for Table 3 Comparison of perioperative complications between obese (O) and non-obese (N) subjects. Data are represented as n (%). * and ** significant difference between obese and non-obese for this age group at 95% CL and 99% CL, respectively N O N O N O N O Difficult laryngoscopy 6 (2.1) 2 (7.8) 12 (1.9) 3 (8.8) 6 (2.4) 5 (6.7) 5 (3.1) 1 (3.5) Multiple laryngoscopy 7 (2.4) 1 (4.3) 15 (2.5) 1 (2.9) 5 (1.9) 2 (2.7) 4 (2.5) 1 (3.4) Grade 2 mask ventilation 7 (3.0) 5 (21.7)** 16 (2.6) 7 (20.6)** 6 (2.4) 15 (20.0)** 6 (3.7) 5 (22.7)** Coughing 11 (3.8) 3 (13.0)* 25 (4.1) 5 (14.7)* 10 (4.0) 9 (12.0) 7 (4.3) 3 (13.6)* Breath holding 6 (2.1) 0 12 (1.9) 1 (2.9) 5 (2.0) 1 (1.3) 3 (1.8) 1 (4.5) Airway obstruction 41 (14.3) 6 (26.1)* 87 (14.2) 8 (23.5)* 36 (14.3) 18 (24.0)* 23 (14.3) 5 (22.7)* Laryngospasm 10 (3.5) 1 (4.2) 22 (3.6) 1 (2.9) 9 (3.6) 2 (2.7) 6 (3.7) 1 (4.0) Bronchospasm 5 (1.7) 2 (8.7)** 11 (1.8) 3 (8.8)** 4 (1.6) 5 (6.7)* 4 (2.4) 2 (9.1)* Bronchospasm in asthmatic patients 3 (7.3) 2 (33.3)** 6 (7.0) 2 (25)** 3 (8.8) 3 (18.7)** 2 (9.5) 1 (25)** Oxygen desaturation 19 (6.6) 4 (17.4)* 40 (6.5) 5 (14.7)* 17 (6.7) 11 (14.7)* 11 (6.8) 3 (13.6)* Overall any respiratory event 76 (26.5) 10 (43.5)* 159 (26.0) 13 (38.2)* 67 (26.6) 32 (42.7)* 53 (33.1) 8 (36.4) Aspiration 1 (0.3) 0 4 (0.6) 0 2 (0.8) 1 (1.3) 2 (1.2) 0 Postoperative vomiting 5 (1.7) 1 (2.1) 12 (2.0) 1 (2.6) 6 (2.4) 3 (3.1) 4 (2.5) 1 (3.4) Unplanned hospital admission 6 (2.9) 1 (4.0) 12 (1.9) 1 (2.9) 5 (2.0) 1 (1.3) 3 (1.8) 0 361

4 El-Metainy et al. obese children reported a change in their anaesthetic plan because of the child s obesity. More obese subjects were induced i.v. in all age classes and more underwent rapid sequence induction (only significant in yr age group). The incidence of tracheal intubation was more common in obese subjects. The results shown in Table 3 revealed significant differences in the incidence of haemoglobin oxygen desaturation, difficult mask ventilation, and airway obstruction between obese and non-obese for all age classes. The occurrence of bronchospasm was higher in obese subjects, especially those with asthma. Adverse respiratory events were significantly more frequent in obese subjects, especially in younger age classes (Table 4). Mallampati classification.ii showed statistically significant higher RR among obese than non-obese subjects controlling for age with age-adjusted RR¼8.34. The risk of all adverse respiratory events was higher among obese subjects with age-adjusted RR¼1.49. There were also significant associations between obesity and asthma controlling for age (OR¼1.8), and between obesity and sleep apnoea (OR¼4.0) (Table 5). Discussion The present study revealed an increased incidence of perioperative adverse respiratory events in obese children, especially in younger age classes. In a study examining female adolescents in Egypt, 12 35% of the examined girls were overweight, and 13% were obese. Overweight classification was more common in urban girls than in rural girls and more common in girls with a higher socio-economic status than in those with a lower socio-economic status. The dramatic increase in childhood obesity in the developing countries including Egypt necessitates examining different modalities of anaesthetic management for this group of patients, anticipating the incidence of complications in these patients, and identifying predictors of complications. The prevalence of obesity in our study was 10.5% of children undergoing surgery and anaesthesia, which was less than results from a recent retrospective study in children. 6 This difference might be attributed to differences in socioeconomic standards between Egypt and developed countries. 6 Childhood obesity is usually associated with medical co-morbidities such as type II diabetes mellitus, asthma, hyperlipidaemia, hypertension, OSA, and heart disease. Our study showed an increased prevalence of coexisting conditions, including asthma, and sleep apnoea, consistent with previous studies. Several studies have shown that being overweight or obese are risk factors for perioperative adverse events in adults, including difficult mask ventilation, laryngoscopy, aspiration, postoperative atelectasis, and surgical site infection However, despite the adult data, there are few studies regarding outcome in overweight or obese children who present for anaesthesia and surgery. In one recent retrospective study, there was a small increase in minor respiratory complications in children who were obese. 7 In another retrospective study that compared normal-weight children with obese children, there was a greater frequency of difficult mask ventilation (2.2% vs 7.4%), postoperative airway obstruction (0.07% vs 1.6%), and difficult laryngoscopy (0.4% vs 1.3%), in obese children. 6 Highly significant differences in the incidence of desaturation, difficult mask ventilation, airway obstruction, or bronchospasm between obese and non-obese subjects for all age classes were encountered in our study. The occurrence of bronchospasm and all adverse respiratory events were significantly higher in obese subjects, especially in younger age classes. In the present study, the risk of all adverse respiratory events was higher among younger obese children than older ones. Table 4 Association between obesity and Mallampati classification.ii and adverse respiratory events. *RR statistically significant at 95% CI Total Adjusted-RR (95% CI) Mallampati classification.ii [RR (95% CI)] Adverse respiratory events [RR (95% CI)] 9.98 ( )* ( )* 7.28 ( )* 7.32 ( )* ( )* 1.64 ( ) 1.47 ( ) 1.61 ( )* 1.09 ( ) ( )* Table 5 Association between obesity and selected medical co-morbidities controlling for age. *OR statistically significant at 95% CI Total Adjusted-OR (95% CI) Hypertension [OR (95% CI)] 4.3 ( ) 3.06 ( ) 2.51 ( ) ( ) Asthma [OR (95% CI)] 2.12 ( ) 1.9 ( ) 1.74 ( ) 1.48 ( ) ( )* Diabetes mellitus [OR (95% CI)] 6.88 ( ) Sleep apnoea [OR (95% CI)] 5.04 ( )* 3.64 ( )* 4.19 ( )* 3.36 ( ) ( )* 362

5 Respiratory events in obese children In conclusion, our results confirmed an increase in the incidence of overweight status and obesity and an association between obesity and adverse respiratory events among Egyptian children presenting for anaesthesia and surgery. It is important to identify patients at risk of complication and anticipate and treat expected complications in obese children. Conflict of interest None declared. Funding This work was supported by Alexandria University. References 1 Hossain P, Kawar B, Nahas M. Obesity and diabetes in the developing countries: a growing challenge. N Engl J Med 2007; 356: Finkelstein E, Fiebelkorn I, Wang G. National medical spending attributable to overweight and obesity: how much, and who s paying? Health Affairs 2003; (Suppl. W3): Ross PA, Scott GM. Childhood obesity: a growing problem for the pediatric anesthesiologist. Semin Anesth Perioper Med Pain 2006; 25: Smith HL, Meldrum DJ, Brennan LJ. Childhood obesity: a challenge for the anaesthetist? Paediatr Anaesth 2002; 12: Brenn BR. Anesthesia for pediatric obesity. Anesthesiol Clin North Am 2005; 23: Nafiu O, Reynolds P, Bambgade O, Tremper K, Welch K, Kasa-Vubu J. Childhood body mass index and perioperative complications. Paediatr Anaesth 2007; 17: Setzer N, Saade E. Childhood obesity and anesthetic morbidity. Paediatr Anaesth 2006; 17: Tait AR, Voepel-Lewis T, Burke C, Kostrzewa A, Lewis I. Incidence and risk factors for perioperative adverse respiratory events in children who are obese. Anesthesiology. 2008; 108: Cole TJ, Bellizzi MC, Flegal KM, Dietz WH. Establishing a standard definition for child overweight and obesity worldwide: international survey. Br Med J 2000; 320: Han R, Tremper KK, Kheterpal S, O Reilly M. Grading scale for mask ventilation. Anesthesiology 2004; 101: Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 1984; 39: Jackson RT, Rashed M, Saad-Eldin R. Rural urban differences in weight, body image, and dieting behavior among adolescent Egyptian schoolgirls. Int J Food Sci Nutr 2003; 54: Sorof JM, Turner J, Martin DS, et al. Cardiovascular risk factors and sequelae in hypertensive children identified by referral versus school-based screening. Hypertension 2004; 43: Hasler G, Buysse DJ, Klaghofer R, et al. The association between short sleep duration and obesity in young adults: a 13-year prospective study. Sleep 2004; 27: Mannino DM, Mott J, Ferdinands JM, et al. Boys with high body masses have an increased risk of developing asthma: findings from the National Longitudinal Survey of Youth (NLSY). Int J Obes 2006; 30: Lavaut J, Dupont H, Lefevre P, Demetriou M, Dumoulin J, Desmonts J. Difficult tracheal intubation is more common in obese than in lean patients. Anesth Analg 2004; 98: Kheterpal S, Han R, Tremper K, et al. Incidence and predictors of difficult and impossible mask ventilation. Anesthesiology 2006; 105: Eichenberger A, Proietti S, Wicky S, et al. Morbid obesity and postoperative pulmonary atelectasis: an underestimated problem. Anesth Analg 2002; 95: Han R, Tremper K, Kheterpal S, O Reilly M. Grading scale for mask ventilation (letter). Anesthesiology 2004; 101: Bond A. Obesity and difficult intubation. Anaesth Intensive Care 1993; 21: