Orthognathic surgery with or without induced hypotension

Abstract

This study involved a retrospective evaluation of patients subjected to surgery for dentofacial deformities treated without induced controlled hypotension (group I, n = 50) and a prospective evaluation of patients who were subjected to surgery under hypotensive general anaesthesia (group II, n = 50). No statistical differences were found between the study groups with regard to the duration of surgery. However, there were statistically significant differences in the need for blood transfusion and the occurrence of bradycardia during the maxillary down-fracture. Hypotensive anaesthesia decreased the need for a blood transfusion and the occurrence of bradycardia, and is therefore considered highly beneficial for patients undergoing orthognathic surgery.

Introduction

Orthognathic surgery for the correction of dentofacial deformities is very well established in terms of outcomes and safety. Double-jaw surgery is often necessary to achieve the expected results. Due to the complex vascularization of the oral and facial area, major bleeding may occur, leading to the need for a blood transfusion. Homologous transfusion is associated with innumerable drawbacks, including bacterial or viral transmission and immunological reactions. Because of these negative aspects, several alternatives to blood transfusion have been investigated.

An autogenous transfusion reduces the need for a homologous transfusion. However, this option requires important preparation and still presents a contamination risk, with possible laboratory problems related to the transfusion process.

Gardner, who used an arteriotomy to reduce blood pressure during a surgical procedure in 1946, first introduced general anaesthesia under hypotension. Since then, a myriad of techniques for inducing hypotension during surgery have been used in orthopaedic and neurosurgery procedures. The first reported maxillofacial procedure in which this technique was applied was performed by Schaberg et al.

Although hypotension reduces intraoperative bleeding, studies to evaluate its effectiveness in reducing blood loss during orthognathic surgery have produced conflicting results. Other studies have described the risk of vital organ hypoperfusion during induced hypotensive anaesthesia.

Due to this controversy in the scientific literature, a study was done involving two groups of patients undergoing general anaesthesia during orthognathic surgery, one group with induced hypotension and the other without. The need for a blood transfusion was evaluated in these two patient groups. In addition, a comparison between the preoperative and postoperative data collected in the hypotensive anaesthesia group was done in order to determine if the orthognathic surgery altered these parameters.

Materials and methods

Data were collected from the medical records of 50 patients who underwent orthognathic surgery in 1998, a year in which all general anaesthesia procedures for orthognathic surgery were performed without any kind of controlled induced hypotension; these patients constituted study group I. Data from a further 50 patients who were operated on under induced controlled hypotension were collected prospectively during the year 1999; these patients constituted study group II.

All the patients included in this study were healthy, without any significant problems in their past or present medical history. Complete clinical and surgical records were available for all of these patients, and all attended their scheduled follow-up appointments. All operations were performed by the same group of surgeons, and all anaesthetic procedures were done by the same group of anesthesiologists. Group II patients were recruited consecutively into the study; these were the first 50 patients who presented with the necessity for orthognathic surgery and who fulfilled the inclusion criteria: healthy, no significant medical history, complete medical records, and attendance of follow-up.

The need for a blood transfusion was compared between the two study groups. Postoperative hematocrit (Hct) and haemoglobin (Hb) values of group II patients were compared to preoperative values in order to establish how these values vary in patients who undergo orthognathic surgery with controlled hypotension. A blood transfusion was considered necessary under the following conditions: Hb values <7 g/dl in association with a heart rate >100 bpm, or hypotension, or diminished urinary output, or increased respiration pattern, or delayed capillary filling (>2 s). The postoperative Hb and Hct levels were assessed 12 h after the end of surgery.

For group I, the drugs used for the induction and maintenance of general anaesthesia were: thiopental (single dose of 2.5 mg/kg) or propofol (single dose of 2 mg/kg) at induction, and a fentanyl bolus (doses of 2–10 μg/kg) at the beginning of the surgical procedure, with additional boluses during surgery, in accordance with the anaesthesiologist’s criteria. Alloferine (neuromuscular blocking agent) was given for muscle relaxation at the required doses. Isoflurane, enflurane, or halothane was given at the doses required to achieve the minimum pulmonary alveolar concentration, or sufficient for the patient to remain anaesthetized.

For group II, the drugs used were: propofol (single dose of 2 mg/kg) at induction, followed by a fentanyl bolus (2 μg/kg). The fentanyl was kept in continuous infusion during the surgery at 1 μg/kg/min and was varied for a higher or lower dose according to the blood pressure response, trying to maintain blood pressure values at an average of 30% lower than normal. Succinylcholine (1%) was given at a dose of 1 mg/kg in a single bolus at anaesthetic induction in order to facilitate the intubation process. Pancuronium (0.08%) at a dose of 0.08 mg/kg was given at induction to achieve neuromuscular blockage. Isoflurane was used in variable concentrations, always lower than the alveolar minimal concentration, thus working in association with the venous drug to maintain the anaesthesia. Protoxide was used at concentrations varying from 50% to 60% during the surgery as a supplementary anaesthetic drug. Droperidol (0.25%) was used at a dosage sufficient to achieve the blood pressure levels desired, never higher than 0.2 mg/kg. Metoprolol (0.1%) was given at a dosage sufficient to keep the heart rate similar to the preoperative level.

At the beginning of surgery all patients (groups I and II) received 500 mg of hydrocortisone, 1 g of ampicillin, and 50 mg of ranitidine. At the end of surgery all patients (groups I and II) received dipyrone 40 mg/kg and nalbuphine hydrochloride (0.02 mg to 0.1 mg/kg). Atropine (0.015 mg/kg) and prostigmine (0.025 mg/kg) were also used.

The osteotomies performed were the sagittal split ramus osteotomy as described by Dal Pont in1961 and the classic Le Fort I osteotomy with no segmentations, sometimes associated with a chin osteotomy, which was done in eight patients in group I and in 12 patients in group II. The data obtained were tabulated and analyzed statistically by analysis of variance (ANOVA).

Materials and methods

Data were collected from the medical records of 50 patients who underwent orthognathic surgery in 1998, a year in which all general anaesthesia procedures for orthognathic surgery were performed without any kind of controlled induced hypotension; these patients constituted study group I. Data from a further 50 patients who were operated on under induced controlled hypotension were collected prospectively during the year 1999; these patients constituted study group II.

All the patients included in this study were healthy, without any significant problems in their past or present medical history. Complete clinical and surgical records were available for all of these patients, and all attended their scheduled follow-up appointments. All operations were performed by the same group of surgeons, and all anaesthetic procedures were done by the same group of anesthesiologists. Group II patients were recruited consecutively into the study; these were the first 50 patients who presented with the necessity for orthognathic surgery and who fulfilled the inclusion criteria: healthy, no significant medical history, complete medical records, and attendance of follow-up.

The need for a blood transfusion was compared between the two study groups. Postoperative hematocrit (Hct) and haemoglobin (Hb) values of group II patients were compared to preoperative values in order to establish how these values vary in patients who undergo orthognathic surgery with controlled hypotension. A blood transfusion was considered necessary under the following conditions: Hb values <7 g/dl in association with a heart rate >100 bpm, or hypotension, or diminished urinary output, or increased respiration pattern, or delayed capillary filling (>2 s). The postoperative Hb and Hct levels were assessed 12 h after the end of surgery.

For group I, the drugs used for the induction and maintenance of general anaesthesia were: thiopental (single dose of 2.5 mg/kg) or propofol (single dose of 2 mg/kg) at induction, and a fentanyl bolus (doses of 2–10 μg/kg) at the beginning of the surgical procedure, with additional boluses during surgery, in accordance with the anaesthesiologist’s criteria. Alloferine (neuromuscular blocking agent) was given for muscle relaxation at the required doses. Isoflurane, enflurane, or halothane was given at the doses required to achieve the minimum pulmonary alveolar concentration, or sufficient for the patient to remain anaesthetized.

For group II, the drugs used were: propofol (single dose of 2 mg/kg) at induction, followed by a fentanyl bolus (2 μg/kg). The fentanyl was kept in continuous infusion during the surgery at 1 μg/kg/min and was varied for a higher or lower dose according to the blood pressure response, trying to maintain blood pressure values at an average of 30% lower than normal. Succinylcholine (1%) was given at a dose of 1 mg/kg in a single bolus at anaesthetic induction in order to facilitate the intubation process. Pancuronium (0.08%) at a dose of 0.08 mg/kg was given at induction to achieve neuromuscular blockage. Isoflurane was used in variable concentrations, always lower than the alveolar minimal concentration, thus working in association with the venous drug to maintain the anaesthesia. Protoxide was used at concentrations varying from 50% to 60% during the surgery as a supplementary anaesthetic drug. Droperidol (0.25%) was used at a dosage sufficient to achieve the blood pressure levels desired, never higher than 0.2 mg/kg. Metoprolol (0.1%) was given at a dosage sufficient to keep the heart rate similar to the preoperative level.

At the beginning of surgery all patients (groups I and II) received 500 mg of hydrocortisone, 1 g of ampicillin, and 50 mg of ranitidine. At the end of surgery all patients (groups I and II) received dipyrone 40 mg/kg and nalbuphine hydrochloride (0.02 mg to 0.1 mg/kg). Atropine (0.015 mg/kg) and prostigmine (0.025 mg/kg) were also used.

The osteotomies performed were the sagittal split ramus osteotomy as described by Dal Pont in1961 and the classic Le Fort I osteotomy with no segmentations, sometimes associated with a chin osteotomy, which was done in eight patients in group I and in 12 patients in group II. The data obtained were tabulated and analyzed statistically by analysis of variance (ANOVA).

Results

Data related to the duration of the operation and the presence or absence of bradycardia at the time of the maxillary down-fracture are described in Tables 1 and 2 .

Table 1
Group I: duration of anaesthesia and presence or not of bradycardia at down-fracture and manipulation of the maxilla. a
Patient no. Bradycardia, yes/no Duration of anaesthesia, min Patient no. Bradycardia, yes/no Duration of anaesthesia, min
1 Yes 360 26 Yes 180
2 Yes 300 27 Yes 585
3 No 240 28 Yes 270
4 No 210 29 Yes 420
5 No 240 30 No 270
6 Yes 480 31 No 450
7 Yes 480 32 No 510
8 Yes 330 33 No 300
9 Yes 450 34 No 285
10 No 190 35 Yes 420
11 No 310 36 Yes 480
12 Yes 300 37 No 300
13 No 195 38 Yes 300
14 Yes 720 39 No 368
15 Yes 630 40 Yes 360
16 No 210 41 Yes 600
17 No 420 42 Yes 705
18 No 345 43 No 368
19 Yes 240 44 No 368
20 Yes 330 45 No 368
21 Yes 300 46 No 368
22 No 330 47 No 368
23 Yes 450 48 No 368
24 Yes 300 49 No 368
25 No 300 50 No 368
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Jan 19, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Orthognathic surgery with or without induced hypotension
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