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Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.56 no.2 Campinas Mar/Apr. 2006
Dexmedetomidine in morbid obese patients undergoing gastroplasty: cardiovascular stability and consumption of intravenous anesthetics. A retrospective study*
Uso de dexmedetomidina en pacientes obesos mórbidos sometidos a gastroplastia: estabilidad cardiovascular y consumo de anestésicos venosos. Estudio retrospectivo
Luiz Piccinini Filho, M.D.I; Lígia Andrade da Silva Telles Mathias, TSA, M.D.II; Carlos Alberto Malheiros, M.D.III; Waldemar Montoya de Gregori, M.D.IV; Álvaro Antonio Guaratini, TSA, M.D.V; Joaquim Edson Vieira, TSA, M.D.IV
Assistente, Hospital Central da ISCMSP; Diretor do Serviço de Anestesiologia
do Hospital Santa Isabel; Médico Assistente do Hospital Central da ISCMSP
IIDiretora do Serviço e Disciplina de Anestesiologia da ISCMSP e Faculdade de Ciências Médicas da ISCMSP; Responsável pelo CET-SBA, ISCMSP
IIIMédico Assistente, Hospital Central da ISCMSP; Professor Adjunto de Cirurgia da Faculdade de Ciências Médicas da ISCMSP
IVMédico Assistente, Hospital Central da ISCMSP
VMédico Assistente, Hospital Central da ISCMSP; Co-Responsável pelo CET/SBA da ISCMSP
VICoordenador do Centro para Desenvolvimento da Educação Médica CEDEM da Faculdade de Medicina da Universidade de São Paulo
AND OBJECTIVES: The administration of powerful and short duration anesthetic
agents is essential for patients undergoing bariatric surgical procedure. The
dexmedetomidine, an a2-adrenergic agonist,
has appeared as an adjuvant option of the venous anesthesia technique. This study
aimed at assessing the efficacy of dexmedetomidine associated with the venous
anesthesia in morbid obese patients undergoing gastroplasty procedures.
METHODS: Retrospective analysis of morbid obese patients undergone open bariatric surgical intervention under anesthesia with propofol and alfentanil, with or without dexmedetomidine. Patients were allocated into two groups: Control (propofol and alfentanil) and Dexmedetomidine (propofol, alfentanil and dexmedetomidine). For both groups, the anesthetic maintenance was as follows: propofol = 0.075 to 0.1 mg.kg-1.min-1 and alfentanil = 0.75 to 1 µg.kg-1.min-1; in the dexmedetomidine (DMD) group, initial dose of 1 µg.kg-1 in 10 min and maintenance with 0.4 to 0.7 µg.kg-1.h-1. The variables studied were: age, gender, body mass index (BMI), surgical time and recovery time, heart rate (HR), systolic and diastolic blood pressure (SBP and DBP), hemoglobin peripheral saturation (SpO-2), propofol and alfentanil consumption and side effects.
RESULTS: The dexmedetomidine group has shown a significant reduction in propofol and alfentanil consumption. The heart rate presented a significant variation only in the dexmedetomidine group. Both SPB and DBP presented a statistically significant reduction in both groups for the first 20 minutes, and subsequent stabilization. No side effects were observed in both groups of patients.
CONCLUSIONS: This study has shown the efficacy of dexmedetomidine administration in combination with venous anesthesia with propofol and alfentanil, thus promoting reduction in venous anesthetic drugs consumption, cardiovascular stability and time to recovery similar to that of the technique without dexmedetomidine. No side effects were noted associated with the use of dexmedetomidine.
Key words: ANALGESICS, Opioids: alfentanil; ANESTHESIA, General: venous; ANESTHETICS, Venous: propofol; DISEASES: morbid obesity; DRUGS: dexmedetomidine; SURGERY, Abdominal: gastroplasty.
Y OBJETIVOS: La utilización de agentes anestésicos potentes
y de corta duración es fundamental en pacientes sometidos a la intervención
quirúrgica bariátrica. La dexmedetomidina, agonista a
2-adrenérgica, surgió como una opción de auxilio
a la técnica de anestesia venosa. El objetivo de esta investigación
fue la de evaluar la eficacia de la dexmedetomidina asociada a la anestesia venosa
en pacientes obesos mórbidos, sometidos a la gastroplastia.
MÉTODO: Análisis retrospectivo de pacientes portadores de obesidad mórbida, sometidos a la intervención quirúrgica bariátrica abierta, bajo anestesia con propofol y alfentanil con o sin dexmedetomidina. Los pacientes fueron colocados en dos grupos: Control (propofol y alfentanil) y Dexmedetomidina (propofol, alfentanil y dexmedetomidina). El mantenimiento de la anestesia en los dos grupos constó de: propofol = 0,075 a 0,1 mg.kg-1.min-1 y alfentanil = 0,75 a 1 µg.kg-1.min-1; en el grupo Dexmedetomidina en la dosis inicial de 1 µg.kg-1 en 10 min y mantenimiento con 0,4 a 0,7 µg.kg-1.h-1. Las variables estudiadas fueron la edad, sexo, IMC, tiempo quirúrgico y de despertar, frecuencia cardiaca (FC), presión arterial sistólica y diastólica (PAS, PAD), saturación periférica de hemoglobina (SpO2), consumo de propofol y alfentanil y efectos colaterales.
RESULTADOS: Se registró una reducción significativa en el consumo de propofol y alfentanil en el grupo Dex-medetomidina. La FC presentó variación significativa apenas en el grupo Dexmedetomidina. La PAS y la PAD presentaron una reducción estadística significativa en los dos grupos en los primeros 20 min, estabilizándose a continuación. Los pacientes de los dos grupos no presentaron efectos colaterales.
CONCLUSIONES: Ese estudio demostró la eficacia del uso de la dexmedetomidina asociada a la anestesia venosa con propofol y alfentanil, trayendo una reducción del consumo de los anestésicos venosos, estabilidad cardiovascular y tiempo de despertar semejante a la técnica sin añadidura de la dexmedetomidina. No hubo efectos colaterales imputables al uso de la dexmedetomidina.
Mortality rates are significantly high in morbid obese (MO) surgical patients. The anesthesia for patients undergoing bariatric surgery intervention requires the knowledge of its pathophysiology, which is fundamental as far as the anatomic, physiologic and biochemical changes are concerned regarding the several organs and systems involved, which imply different responses to drugs and anesthetic techniques used1.
Dexmedetomidine (dextro-rotatory isomer DMD) is the result of the separation of the a2-agonist racemic medetomidine for veterinary use in two isomers, thus evidencing that hypnotic and analgesic effects were due its action on the a2-adrenergic receptors.
Talke et al.3 have shown that dexmedetomidine may be safely used in patients under high risk for complications. Animal studies have showed that the drug not only reduces the anesthetics needing but also has an intrinsic anesthetic property 4,5.
The searching for a safer anesthetic technique to morbid obese patients undergoing bariatric surgery procedures has come with a possibility of dexmedetomidine use as adjuvant of the balanced general anesthesia technique. Therefore, the objective of the present research was to assess the efficacy of dexmedetomidine in combination with intravenous anesthesia in a retrospective study involving morbid obese patients undergoing open gastroplasty.
Upon approval by the Ethics Committee on Research of the Irmandade Santa Casa de Misericórdia de São Paulo (ISCMSP) this study focused on examination medical records of morbid obese patients (body mass index from 40 kg.m-2 on) undergone bariatric surgery intervention, namely open gastroplasty with jejunogastric Roux-en-Y and silastic ring, under intravenous general anesthesia (midazolam, propofol and alfentanil), with or without dexmedetomidine association, during the years 2001 and 2002.
Patients were participants of the Institution's Morbid Obesity Group and as such were assessed before surgery by a multi-disciplinary team, had recent additional tests performed and their medical condition duly balanced, thus being regarded as physical status ASA II patients.
The study exclusion criteria were: BMI < 40 kg.m-2, aged over 60 years, administration of any anesthetic or analgesic drug except propofol, alfentanil and dexmedetomidine as anesthetic technique, administration of preanesthetic drug, change in heart rate independent of the baseline disease and use of a2-adrenergic antagonists, antidysrythmic or anxiolytics.
The patients' medical records were allocated in two groups:
Control Group anesthetic technique: propofol and alfentanil;
Dexmedetomidine Group anesthetic technique: propofol, alfentanil and dexmedetomidine.
Assistance and care procedures for both groups of patients were the same.
Monitoring and anesthetic technique were also similar, except the administration of dexmedetomidine.
At the operating room, a 18G catheter was inserted in a peripheral vein and lactate Ringer's infusion started.
Patients were positioned in the surgical table on horizontal dorsal decubitus, with the head slightly elevated in 10 degrees. They were monitored for heart rate (HR), electrocardiographic tracing (ECG), systolic and diastolic blood pressures (SBP and DBP) by non invasive method and peripheral hemoglobin saturation (SpO2), and then had the bispectral index electrode (BIS) placed on the forehead.
Drug doses used during anesthetic procedure were calculated based on the 100 kg weight for men and women.
The 100% O2 oxigenation started with facial mask, followed by venous induction with sequential administration of midazolam (5 to 10 mg), alfentanil (300 µg), propofol (2 to 3 mg.kg-1) and atracurium (50 mg).
After orotracheal intubation, patients were kept under mechanical ventilation with a 2 L.min-1 flow semi-closed circular system anesthetic device, using a 50% O2:N2O mixture.
The anesthesia maintenance was carried out with a rate adjusted infusion pump to keep the BIS values between 50 and 60 6, and started in both groups with following doses: propofol 0.075 to 0.1 mg.kg-1.min-1 and alfentanil 0.75 to 1 µg.kg-1.min-1. Dexmedetomidine doses used were: initial the 1µg.kg-1 in 10 minutes; maintenance 0.4 to 0.7 µg.kg-1.h-1.
When the aponeurosis suture started, the dexmedetomidine and alfentanil infusion were interrupted, the propofol pump has been interrupted at the start of the skin suture. When the patient reached a tidal volume over 400 mL under assisted ventilation, and being awaken, he/she was changed to spontaneous ventilation, which, once adequate, led to extubation. Then, it was assessed the recovery time (BIS > 90 as a standard) 7, pain presence and intensity, nausea and vomiting and the patient was referred to the postanesthesia recovery room.
The variables considered were: age, gender, weight, height and BMI; surgical time; propofol, alfentanil and dexmedetomidine consumption; HR; SBP; DBP; SpO2; recovery time and intra and postoperative complications.
Data for HR, SBP, DBP and SpO2 variables were analyzed before induction, at every 5 up to 60 min after induction and every 10 min up to the end of the anesthetic procedure.
The statistical tests applied were: non-paired Student t, Mann-Whitney, Chi-square (c2), ANOVA for repeated measures and Tukey. It was also considered the statistically significant difference when p < 0.05. The statistical software used was the Sigma Stat for Windows, version 2.03, SPSS Inc.
Seventy-three medical records were analyzed, 33 to the Control Group and 40 to the Dexmedetomidine Group. There was not significant difference between groups as regards demographic data and HR, SBP and DBP variable results at the beginning of the study (Table I).
Surgical times (mean value) were of 165 min and 180 min for Control and Dexmedetomidine groups, respectively, with no significant difference between them (p = 0.85, Mann-Whitney test). Recovery time was similar for both groups, between 5 and 10 minutes. Propofol and alfentanil values were presented as median, because they did not pass the Kolmogorov-Smirny normality test and were recorded for total doses related to observation time in both groups (Table II). The noted reduction was 30%, for propofol and alfentanil aswell, with a statistically significant difference.
The mean dexmedetomidine consumption was 198.1 ± 16.9 µg and the time-related mean consumption was 0.98 µg.min-1. Considering initially, 1 µg.kg-1 dose in 10 min and weight defined as 100 kg, all patients received 100 µg at the first 10 min. Then the dose was reduced to 0.4 to 0.7 µg.kg.h-1, corresponding to 40 to 70 µg.kg-1.h-1.
The time-related mean evolution did not differ between groups for HR, SBP and DBP variables (p = 0.073, 0.121 and 0.89, respectively). Statistically different values were noted in the begining HR: 5 and 140 min; in the begining SBP: 5, 10 and 35 min, and in the begining DBP: 5, 10, 140 and 150 min.
The time-related HR variation for both studied groups may be noted in figure 1. In Control group, the ANOVA for HR repeated measures did not show statistical difference among all studied moments (p = 0.077). In Dexmedetomidine group, that test revealed a statistically significant difference (p < 0.001) among the different studied moments. Table III shows the Tukey test results with statistically significant differences.
Figure 2 shows the moments related SBP variation in both studied groups. Values have shown a statistically significant evolution in both groups (ANOVA < 0.0001) and the Tukey test results with a statistically significant variation shown on Table III.
The moments related DBP variation in both studied groups may be observed on figure 3. In the Variance Analysis for repeated measures, a statistical difference (p < 0.001) was noted in both studied groups and the Tukey test results with a statistically significant variation, as shown on table III.
Values recorded for SpO2 have shown stability during all observation period, and no statistically significant difference has been demonstrated between groups and among considered moments.
Time to recovery was similar for both Control and Dexmedetomidine groups, with a 5 to 10 min variation.
Patients recovered without nausea or vomiting symptoms in both groups and only four patients in Control group and three in Dexmedetomidine group experienced low intensity pain, without needing analgesics.
All patients were transferred to the PACU, with an Aldrete-Kroulik index between 9 and 10.
Both group patients did not present any anesthetic techniques-related complications in the intra and postoperative periods.
The bariatric surgery has changed the morbid obese patient requiring anesthesia profile. These subjects are evaluated by a multidisciplinary team, receiving psychotherapic support, associated diseases are properly investigated and treated and then they are referred for surgery. There was also a significant investment in the postoperative evolution of these patients 8. This way, the morbimortality associated with the surgical-anesthetic procedure for morbid obese subjects has significantly decreased 9.
There are a few studies associating the anesthetic technique for bariatric surgery with intraoperative hemodynamic conditions and recovery conditions 10-13. Up to the time of the present study undertaking, three publications have been found in the literature about the use of dexmedetomidine in the anesthesia for bariatric surgery, being one case report 14 and two studies that evaluated only the intra and postoperative analgesia 15,16.
This research has evaluated the Institution standard anesthetic technique compared to the dexmetedomidine associated use, which should has offered advantages to morbid obese patient both intra and postoperative.
Use of BIS was a key factor to demonstrate that the same anesthetic level for both anesthezied patients groups that, in addition to promote the reduction in the amount of anesthetics required 6.
Several formulas have been proposed to calculate the ideal weight 11,17,18. Bouillon and Shafer 19 suggested that, regardless of any formulas existing for this calculation, one should not go over 80 kg for women and 100 kg for men as maximum values. Stoelting and Dierdorf 20 proposed to consider 80 kg for women and 100 kg for men as the ideal weight for an obese patient.
As no consensus exists as to the calculation method of anesthetic dose for obese patients, it was decided to use 100 kg for both genders. However, it is important to mention that this calculation was used only for drug administration starting process purposes, as afterwards, during the continuous infusion, the criterion was the BIS maintenance between 50 and 60, which are values regarded by the literature as indicative of deep hypnosis 6.
The literature lacks material on the comparison among different anesthetic techniques for morbid obese patients. However, when analyzing studies issued on the hemodynamic, respiratory and post-anesthesia recovery changes in morbid obese patients, one can note that most of them have received propofol as general anesthesia, which indicated it of as a safe drug for morbid obese patients 21-28.
Even in the presence of controversies about which anesthetic technique is going to be used, intravenous or inhalational, research shows that the association with dexmedetomidine in non-obese patients may be advantageous when compared to both techniques individually 29,33.
The total and time-related propofol and alfentanil consumption have shown a statistically significant difference in both groups, lower in the Dexmedetomidine group, around 30%, which is regarded as clinically important, thus confirming previous researches in non-obese patients 29,30,32.
The present study did not intend to evaluate the techniques used as regards cost involved. However, as cost is a key item today in hospital governing terms, it is worthy to mention that at the time this procedures were performed, the total sum of expenses with technique applied to Control group was higher than for the Dexmedetomidine group, including one dexmedetomidine ampoule. Therefore, considering the anesthetics consumption, the association of dexmedetomidine with intravenous anesthetic techniques has shown to be advantageous, as already demonstrated in the literature for non morbid obese patients 29,30,32.
There was no statistically significant change in heart rate for Control group. In the Dexmedetomidine group there was a significant reduction soon after induction, rapidly stabilized and kept as such till the end of the study. Although representing a statistically significant difference, this 12.5 reduction does not have any clinical value 34.
Systolic and diastolic blood pressure values were similar in both groups, demonstrating significant variation over time. The initial reduction and subsequent stabilization, tending to go back to baseline graphics, were noted in both groups. In the Control group there was a 15% reduction in SBP and DBP levels, whereas in the Dexmedetomidine group the reduction varied from 15% to 20%.
In both groups, recovery time was similar, without any occurrence.
Dexmedetomidine associated with the intravenous anesthetic technique provided initial reduction in the HR, SBP and DBP variables, then maintaining them under proper levels and promoting cardiovascular stability during the study course, as noted by the literature for non obese patients 3,35. In addition, dexmedetomidine use did not increase prevalence of adverse reactions.
The postoperative hypoxia is one of the greatest complications of surgical procedures in morbid obese patients. Some authors even propose the oxygen administration during the first 3-days period after surgery 36,37. Morbid obese patients present a high incidence of thromboembolic disease and are in risk for pulmonary embolism 36. Therefore, anesthetic techniques who provide a faster postanesthesia recovery, thus allowing early mobility for the morbid obese patient, reduce the possibility of respiratory depression and thromboembolism.
Taking all the aforementioned comments into account, one can conclude by the present study that the proposed anesthetic technique, intravenous anesthesia with dexmedetomidine, is indicated for morbid obese patients, as it reduces the anesthetics consumption, maintain the cardiovascular stability and promotes the early post anesthesia recovery.
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Dra. Lígia Andrade da Silva Telles Mathias
Alameda Campinas, 139/41
01404-000 São Paulo, SP
for publication 02 de junho de 2005
Accepted for publication 09 de janeiro de 2006
* Received from CET/SBA, Serviço de Anestesiologia da Irmandade Santa Casa de Misericórdia de São Paulo (ISCMSP), São Paulo, SP.