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On-line version ISSN 1806-907X
Rev. Bras. Anestesiol. vol.52 no.2 Campinas Mar./Apr. 2002
Preanesthetic clinical problems of morbidly obese patients submitted to bariatric surgery: comparison with non-obese patiens*
Problemas clínicos pré-anestésicos de pacientes mórbidamente obesos sometidos a cirugías bariátricas: comparación con pacientes no obesos
Getúlio Rodrigues de Oliveira Filho, TSA, M.D.I; Tânia Helena Carnieleto Nicolodi, M.D.II; Jorge Hamilton Soares Garcia, TSA, M.D.III; Marcos Antônio Nicolodi, TSA, M.D.III; Ranulfo Goldschmidt, TSA, M.D.III; Adilson José Dal Mago, M.D.III
IResponsável pelo CET/SBA
IIAnestesiologista do Grupo de Cirurgia Bariátrica do Hospital de Caridade
IIIInstrutor do CET/SBA
BACKGROUND AND OBJECTIVES:
Morbid obesity is associated to clinical problems responsible for decreased
life expectancy. Morbidly obese patients are candidates to gastric bypass and
pose new challenges to the anesthesiologist. This study compared the prevalence
of clinical problems among morbidly obese patients submitted to bariatric surgery
to non-obese patients submitted to other elective surgical procedures.
METHODS: Electronic records of 2986 patients were retrospectively studied. Patients were divided in two groups; 1: patients with morbid obesity submitted to bariatric surgeries; and group 2: non obese patients (body mass index less than 30 kg.m-2), submitted to other elective surgical procedures. Groups were matched according to age, gender and ASA physical status. Preanesthetic problems common to group 1 were investigated in group 2, and prevalence was compared. Odds ratios and 95% confidence limits were calculated.
RESULTS: Clinical problems identified in groups 1 and 2 and their respective prevalence were: gastroesophageal reflux (16.67% and 0.48%), systemic hypertension (50% and 3.06%), type II diabetes mellitus (6.25% and 0.31%), hypothyroidism (6.25% and 0.31%), bronchial asthma (10.42% and 1.43%) and restrictive lung disease (10.42% and 0.03%). Incidences were significantly higher in group 1. Additionally, the following problems were found in group 1, but not in group 2: epilepsy (2.08%), nonalcoholic fatty liver (12.5%), gall bladder stones (6.25%), dyslipemia (20.83%) and hypopytuitarism (2.08%).
CONCLUSIONS: The prevalence of clinical problems was significantly higher in morbidly obese patients as compared to their non-obese counterparts.
Key words: PREANESTHETIC EVALUATION; SURGERY: Abdominal: bariatric
JUSTIFICATIVA Y OBJETIVOS:
La obesidad mórbida se asocia a problemas clínicos, responsables por disminución
de la expectativa de vida. Pacientes obesos mórbidos son candidatos a cirugías
bariátricas, imponiendo nuevos desafíos al anestesiólogo. Este estudio comparó
la prevalencia de problemas clínicos entre pacientes mórbidamente obesos sometidos
a cirugías bariátricas y no obesos sometidos a otros procedimientos electivos.
MÉTODO: Fueron estudiados, retrospectivamente, los registros electrónicos de 2986 pacientes divididos en grupo 1, obesos mórbidos sometidos a cirugías bariátricas y grupo 2, con índice de masa corporal menor que 30, sometidos a otros procedimientos electivos, relacionados al grupo 1 por la edad, sexo y estado físico (ASA). Los problemas pré-anestésicos del grupo 1 fueron pesquisados en el grupo 2 y las prevalencias comparadas. Las razones de chance (RC) y respectivos limites de 95% de confianza (LC 95%) fueron calculados.
RESULTADOS: Los problemas identificados nos grupos 1 y 2 y sus respectivas prevalencias fueron: reflujo gastroesofágico (16,67% y 0,48%), hipertensión arterial sistémica (50% y 3,06%), diabetes mellitus tipo II (6,25% y 0,31%), hipotiroidismo (6,25% y 0,31%), asma bronquica (10,42% y 1,43%) y pneumopatia restrictiva (10,42% y 0,03%). Las prevalencias fueron significativamente mas altas en el grupo 1. Fueron también identificados, en el grupo 1, los siguientes problemas que no fueron encontrados en el grupo 2: epilepsia (2,08%), esteatosis hepática (12,5%), colecistopatia calculosa (6,25%), dislipidemia (20,83%) e hipopituitarismo (2,08%).
CONCLUSIONES: La prevalencia de problemas clínicos es significativamente mas alta en pacientes portadores de obesidad mórbida de que en no obesos de la misma edad, sexo y estado físico.
Morbid obesity is defined by a high body mass index, that is, weight in kilos divided by the square of height in meters, equal to or higher than 40 kg.m-2. Its prevalence has increased in the last decades and, as a consequence, the cost with the treatment of associated diseases, such as hypertension, diabetes mellitus, ischemic heart disease and pulmonary artery hypertension have also increased. Life expectancy of morbidly obese patients is significantly lower as compared to their non-obese counterparts. For such patients, surgery is the only effective treatment 1. The knowledge of obesity-related problems allows for a deeper investigation of systems more often affected by the disease during preanesthetic evaluation. This study aimed at identifying obesity-related diseases detected during preanesthetic evaluation in morbidly obese patients submitted to gastric bypass and at comparing their incidence in a non-obese population.
fter the Hospitals Medical Ethics Committee approval, preanesthetic evaluation records of 2.986 patients were reviewed. Patients were divided in Group 1 (n = 48): morbidly obese, submitted to gastric bypass; and Group 2 (n = 2938): with body mass index (BMI) below 30 and submitted to other elective procedures, who were matched to Group 1 patients by age, gender and ASA physical status. Preanesthetic problems identified in Group 1 were investigated in Group 2 and prevalences were compared by Chi-square test with Yates correlation and Fishers exact test. Odds ratio (OR) and respective 95% confidence limits (CL 95%) were calculated from respective contingency tables. Significance level was 5%.
Groups were homogeneous in age and height. Frequency of physical status ASA II and female gender, as well as weight and BMI were significantly higher in Group 1 (Table I).
Diseases identified during preanesthetic evaluation of Group 1 patients and also seen in Group 2, together with their respective prevalences, were: gastroesophageal reflux (16.67% and 0.48%), systemic hypertension (50% and 3.06%), type II diabetes mellitus (6.25% and 0.31%), hypothyroidism (6.25% and 0.31%), bronchial asthma (10.42% and 1.43%) and restrictive lung disease (10.42% and 0.03%) (Table II).
The following problems were also identified in Group 1, but not seen in Group 2: epilepsy (2.08%), nonalcoholic fatty liver (12.5%), gall bladder stones (6.25%), dyslipidemia (20.83%) and hypopytuitarism (2.08%).
Selection criteria for gastric bypass were established by the International Federation for Obesity Surgery and are the following: body mass index above 40 kg.m-2, or between 35 and 40 kg.m-2 in patients with co-morbidities treatable by weight loss, presence of obesity for at least 5 years, conservative treatment failure, no alcohol or severe psychiatric problems history, age between 18 and 55 years and acceptable surgical risk determined by preoperative evaluation 1.
Obese patients candidates to obesity surgeries are submitted to a multidisciplinary evaluation including, nutritionists, specialized nurse, psychologist or psychiatrist and anesthesiologist. The anesthesiologists role is critical for detecting coexistent morbidities, recommending additional exams and specialized evaluations, aiming at controlling coexistent diseases. This is the reason why preanesthetic evaluation is performed well in advance.
In our study, the prevalence of gastroesophageal reflux was significantly higher in obese patients. While obesity could not contribute to the presence of gastroesophageal reflux 2, there are evidences that weight and body mass index are directly related to this condition 3, probably due to a higher incidence of hiatal hernia 4. Manometric esophageal changes were observed in 61% of patients and may contribute for visceral sensation abnormalities in morbidly obese patients 5. Patients with body mass index above 30 kg.m-2 had 2.8 times more chance of developing reflux (1.7 to 4.5) than those with BMI below 30 kg.m-2 6. The presence of gastroesophageal reflux is related to critical events associated to tracheal intubation 7.
Systemic hypertension was observed in 50% of obese patients. Obesity leads to eccentric ventricular hypertrophy related to the increase in circulating blood volume. However, in hypertensive obese patients there is an increase in systemic vascular resistance and left ventricle concentric hypertrophy, increasing the risk for myocardial ischemia during adrenergic discharge-triggering maneuvers. Weight loss results in improved ventricular dimensions 8 and in hypertension control 9,10.
Glicidic and lypidic metabolic changes are common in morbidly obese patients. Obesity is invariably followed by insulin resistance. Although fasting lipemia being normal in obese patients, post-prandial hyperlipemia is frequent, probably due to the competition of kilomicra and very low molecular weight lipoproteins for the same metabolic paths. Obesity leads to an overproduction of very low molecular weight lipoproteins by liver free fatty acids influx increase, both in post-prandial periods (as from lipolysis of triglyceride-rich particles) and during post-absorption periods (as from adipocytes) 11. So, 6.25% prevalence of type II diabetes mellitus and 20.83% prevalence of dyslipemia in obese patients are justified. Both conditions are risk factors for arteriosclerosis and ischemic heart disease, and are controlled by gastric bypass 12.
Sub-clinical hypothyroidism is more frequent in obese and/or diabetes patients and may be responsible for the low resting energy expenditure rate found in some obese patients 13,14
Non-alcoholic fatty liver is frequent in obese patients and may evolve to liver cirrhosis and failure. Treating obesity will improve this condition. Most important risk factors are insulin resistance and systemic hypertension 15. In our study, non-alcoholic fatty liver was diagnosed by preoperative ultrasound in 12.5% of patients. The diagnosis of such condition should direct the investigation to additional liver function lab tests since intravenous anesthetics and neuromuscular blockers pharmacokinetics may be changed in the presence of liver disfunction. In addition, the fatty liver is more susceptible to hypoxic damage 16.
Morbidly obese patients have abnormal pulmonary function tests, characterized by decreased reserve expiratory volume, forced vital capacity, forced expiratory volume in 1 second, functional residual capacity and maximum voluntary ventilation 17. Respiratory work is increased with obesity. Sleep apnea worsens such condition for decreasing respiratory conductance in upper and lower airways, thus overloading breathing muscles 18. Intravenous anesthetics and neuromuscular blockers used for inducing anesthesia change respiratory mechanics, especially by increasing airway resistance resulting in hypoxemia 19. The increased closing volume of obese patients prolongs alveolar denitrogenation time and reduces apnea tolerance 20.
Asthma is more frequent in obese, as compared to non-obese patients, as shown by this and other studies 21. Gastroesophageal reflux might be an important factor in asthma patogenesis in obese patients. Gastric bypass controls disease severity in 50% of patients 22. Asthma is associated to an increased risk for bronchospasm during tracheal intubation and prophylactic measures are justified.
This study has the limitations inherent to case-control retrospective studies. For example, some well-known obesity-related problems, such as spinal and upper airway anatomic abnormalities were not included because they were not recorded in the database. For choosing the control group, patients were recorded by age, gender and physical status, aiming at establishing similar demographics for both groups. In spite of that, there has been a predominance of females and physical status ASA II patients in the morbidly obese group. This is explained by the fact that no fixed relationship was established to match groups as to the number of cases, that is, all patients with the same characteristics of each group 1 patient were included in the control group.
Notwithstanding those limitations, the study has shown clinical problems most frequently associated to obesity in the context of gastric bypass.
The conclusion was that, when compared to non-obese patients of the same age, gender and physical status, morbidly obese patients had a higher prevalence of preanesthetic problems. It is recommended that the preanesthetic evaluation be done well in advance to allow for additional lab tests and specialized evaluations.
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Dr. Getúlio Rodrigues de Oliveira Filho
Rua Luiz Delfino 111/902
88015-360 Florianópolis, SC
Submitted for publication August 03, 2001
Accepted for publication October 09, 2001