Abstract
Induced hypotensive anaesthesia and isovolaemic haemodilution are well-established blood-sparing techniques in major surgery. This prospective study compared them for blood loss, transfusion requirements, and surgical field quality during standardized orthognathic operations. In a surgeon-blinded trial, 60 healthy patients requiring either Le Fort I osteotomy or bimaxillary surgery were randomly allocated to receive normotensive anaesthesia, induced hypotensive anaesthesia, or induced hypotensive anaesthesia combined with isovolaemic haemodilution. Blood loss and haemoglobin level were measured intraoperatively and calculated on postoperative day 3. The surgeons rated surgical field quality. Mean blood loss was 1021.63, 392.38 ( p < 0.05) and 1191.65 ml in the normotensive, hypotensive and haemodilution groups, respectively. Mean haemoglobin level immediately after surgery was 9.3, 10.3, and 7.4 g/dl ( p < 0.05), respectively. No hypotensive group patients received transfusions; four normotensive group patients required allogenic transfusions; seven haemodilution group patients needed autogenous retransfusions ( p < 0.05). Surgical field quality was significantly better in the hypotensive than in the normotensive ( p < 0.05) or haemodilution ( p < 0.05) groups. In orthognathic surgery, hypotensive anaesthesia significantly reduces blood loss and transfusion requirements and minimizes allogenic transfusions risks. Induced hypotensive anaesthesia combined with isovolaemic haemodilution has no additional blood-sparing effects but impairs surgical field quality.
Orthognathic surgery involves common elective and standardized procedures for correction of dentofacial deformities . Surgical planning and techniques have improved to the extent that safe one-stage operations can be performed for complex bimaxillary deformities, but excessive blood loss, requiring allogenic transfusions, is one of the major complications . Increasing awareness of transfusion risks have led to the development of strategies for reducing intraoperative blood loss, particularly during elective operations .
Induced hypotensive anaesthesia, first described by Gardner in 1946, is commonly applied to reduce blood loss and the need for allogenic transfusions during major general surgery as well as orthognathic surgery . It is also thought to improve surgical field visualisation and to reduce operating time . The technique involves reducing the mean arterial pressure (MAP) up to 50 mmHg with different drugs, including inhalational anaesthetic agents, beta-adrenergic antagonists, calcium channel blockers, and direct-acting vasodilators such as nitroglycerin and sodium nitroprusside .
Isovolaemic haemodilution has been widely used in major general and orthopaedic surgery, particularly when significant blood loss is probable, but its efficacy in reducing transfusion requirements is still questioned . The circulating blood volume is maintained by infusing crystalloid to replace the blood initially removed. The decrease in red blood cell volume is matched by an increase in plasma volume. By reducing the haematocrit, isovolaemic haemodilution limits the decrease in red cell mass caused by blood loss during the surgical procedure. The removed blood is then reinfused as autologous whole blood during or after surgery. Intraoperative autogenous blood donation also has potential disadvantages . It requires adequate monitoring and does not eliminate the risk of bacterial contamination or administration errors. Additional costs are incurred by isovolaemic haemodilution, and additional time is required to collect and store blood . No prospective study has examined the simultaneous use of induced hypotensive anaesthesia and isovolaemic haemodilution in orthognathic surgery.
The aim of this prospective, randomized, single-blinded study was to examine induced hypotensive anaesthesia alone and combined with isovolaemic haemodilution and to compare the two procedures in terms of blood loss, transfusion requirements, and surgical field quality during standardized orthognathic surgery.
Patients and methods
After institutional ethics committee approval and obtaining informed patient consent, this study included 60 patients requiring orthognathic surgery. The orthognathic procedures performed were either standardized Le Fort I osteotomy (one or two pieces cut) or bimaxillary osteotomies (i.e. Le Fort I osteotomy as one or two pieces cut combined with standardized mandibular bilateral sagittal split osteotomy according to O bwegeser /D al P ont or H unsuck ) . All patients were classified as American Society of Anesthesiologists physical status I or II, had no cardiovascular, cerebrovascular, renal, or hepatic diseases, and denied taking any medication within the last 2 weeks.
Study design
Patients were randomly assigned to one of three study groups receiving either normotensive anaesthesia (normotensive group, n = 19), induced hypotensive anaesthesia (hypotensive group, n = 21), or induced hypotensive anaesthesia combined with isovolaemic haemodilution (haemodilution group, n = 20). Only the anaesthesiologist was aware of the patients’ group assignment; surgeons were blinded to all anaesthesiological procedures. All operations were performed by the same surgical team. All patients were placed in a 20–30° head-up position, and 10 ml of 1% lidocaine with epinephrine 1:200,000 was injected submucosally in the oral cavity. Induced hypotensive anaesthesia (groups 2 and 3) with a MAP of 50–55 mmHg was achieved by intermittent intravenous boluses of sodium nitroprusside and maintained from the beginning of the osteotomy to the end of osteosynthesis. Arterial pressure was invasively recorded every 5 min during surgery. Group 3 patients additionally received preoperative isovolaemic haemodilution with two whole blood donation units (900 ml) up to a haemoglobin concentration of 9.0 g/dl and simultaneous infusion of hydroxyethyl starch solution (6%) for isovolaemia. The preoperatively collected blood was anticoagulated with citrate and stored at room temperature until used. Allogenic or autogenous transfusion was given for a haemoglobin concentration below 6.5 g/dl during surgery and below 7.0 g/dl thereafter. The anaesthetist measured the perioperative blood loss by subtracting the volume of saline used from the total volume in the suction unit (no surgical gauze was used). The calculated blood loss on the third postoperative day was estimated according to B ourke & S mith .
Routine laboratory tests included creatine kinase (CK), CK myocardial bound (CK-MB) fraction, cardiac troponin T to detect myocardial cell injury, serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and gamma glutamyl transferase (γGT) as markers of hepatic disorders, serum levels of sodium (Na+), potassium (K+) and creatinine to detect renal dysfunction, and international normalized ratio (INR), prothrombin time (PTT) and platelet counts as routine coagulation parameters. All parameters were obtained one day before, and immediately after, surgery as well as on the first, second and third postoperative days.
The surgical field quality immediately after surgery was independently rated by the surgeon and first assistant and scored by bleeding severity on an ordinal scale published by F romme et al. ( Table 1 ).
| Grade 5: | Massive uncontrollable bleeding |
| Grade 4: | Heavy but controllable bleeding that significantly interferes with dissection |
| Grade 3: | Moderate bleeding that slightly compromises surgical dissection |
| Grade 2: | Moderate bleeding that is a nuisance but does not interfere with accurate dissection |
| Grade 1: | Mild bleeding that is not a surgical nuisance |
| Grade 0: | No bleeding, virtually bloodless field |
Anaesthetic protocol
All patients were premedicated with 7.5 mg of oral midazolam 1 h before induction of anaesthesia. The standardized anaesthetic technique consisted of intravenous induction with 4–5 mg/kg of sodium thiopental, 3 μg/kg of fentanyl, and 0.6 mg/kg of rocuronium. The patient was then intubated by the nasoendotracheal route and placed in a 10° Fowler position. Anaesthesia was maintained by continuous inhalation of 66% nitrous oxide in oxygen and isoflurane 0.6–1.0 vol%, as well as intermittent boluses of 1–2 μg/kg of fentanyl, and 0.15 mg/kg of rocuronium. Intraoperative monitoring consisted of electrocardiogram measurement of end-tidal carbon dioxide, pulse oximetry, temperature, and arterial pressure.
Statistical analysis
All data analyses were calculated by the Institute for Medical Statistics, Charité-Campus Benjamin Franklin, Berlin (Priv.-Doz. Dr. rer. nat. Dr. med. W. Hopfenmueller) and performed with the Statistical Package for Social Sciences software (SPSS for Windows 12.0; SPSS Inc.). Continuous variables were compared using t test when normally distributed or one-way ANOVA for more than two groups. Nonparametric variables were compared using the Mann–Whitney U -test. All statistical tests were two-tailed with a p value < 0.05 indicating statistical significance.
Results
The three study groups had similar demographic data with no statistically significant differences in mean weight, height, body mass index, or preoperative systolic/diastolic pressure ( Table 2 ). The study included significantly more women ( p < 0.05), and the mean age was significantly lower in the haemodilution group than in the normotensive or hypotensive groups ( p < 0.05) ( Table 2 ).
| Variable | Normotensive (group 1, n = 19) | Hypotensive (group 2, n = 21) | Haemodilution (group 3, n = 20) | p value |
|---|---|---|---|---|
| Sex: female/male | 15/4 | 15/6 | 12/8 | >0.05 (female vs male) |
| Mean age (years) | 31.6 | 27.9 | 22.7 | >0.05 (group 3 vs group 1 and 2) |
| Mean weight (kg) | 68.1 | 67.9 | 66.8 | n.s. |
| Mean height (cm) | 172 | 172 | 174 | n.s. |
| Mean body mass index | 22.8 (18.5–30.6) | 21.0 (18.3–33.5) | 22.1 (19.4–26.3) | n.s. |
| Mean preoperative systolic/diastolic blood pressure (mmHg) | 123.4/67.3 | 120.1/65.1 | 123.7/69.6 | n.s. |
| Mean preoperative haemoglobin level (g/dl) | 13.5 (11.6–16.0) | 13.4 (12.2 – 16.0) | 13.6 (11.3–16.0) | n.s. |
| Double jaw/single jaw operation | 13/6 | 13/8 | 14/6 | n.s |
| Mean operating time (min) | 227.6 (105–450) | 215.5 (125–525) | 211.5 (90–355) | n.s. |
| Blood transfusion | 4 (allogenic) | 0 | 7 (autogenous) | >0.05 (group 2 vs group 1 and 3) |
The mean preoperative haemoglobin level, mean operating time, and mean number of single or double jaw operations did not differ significantly between the groups. The mean preoperative haemoglobin level was 13.5 g/dl (11.6–16.0 g/dl) in the normotensive group, 13.4 g/dl (12.2–16.0 g/dl) in the hypotensive group, and 13.6 g/dl (11.3–16.0 g/dl) in the haemodilution group ( Table 2 ). The mean operating time was 227.6 min (105–450 min) in the normotensive group, 215.5 min (125–525 min) in the hypotensive group, and 211.5 min (90–355 min) in the haemodilution group ( Table 2 ). The mean number of single or double jaw operations was 13 double and 6 single jaw operations in the normotensive group, 13 double and 8 single jaw operations in the hypotensive group, and 14 double and 6 single jaw operations in the haemodilution group ( Table 2 ).
The mean measured blood loss during surgery was 1021.63 ml (300–2600 ml) in the normotensive group, 392.38 ml (50–1610 ml) in the hypotensive group, and 1191.65 ml (50–2950 ml) in the haemodilution group ( Fig. 1 ). Statistical analysis revealed a significantly lower mean blood loss in the hypotensive group than in the normotensive ( p < 0.05) or haemodilution ( p < 0.05) groups. The mean blood loss did not differ significantly between the normotensive and haemodilution group ( Fig. 1 ).
The mean haemoglobin level immediately after surgery was 9.3 g/dl (6.4–12.8 g/dl) in the normotensive group, 10.3 g/dl (8.3–14.6 g/dl) in the hypotensive group, and 7.4 g/dl (6.0–8.9 g/dl) in the haemodilution group ( Fig. 2 ). Four of 19 patients in the normotensive group received allogenic transfusions, and 7 of 20 in the haemodilution group were retransfused without requiring additional allogenic transfusions. None of the 21 patients in the hypotensive group required allogenic blood transfusion ( p < 0.05) ( Table 2 ). The postoperative haemoglobin level was significantly lower in the haemodilution group than in the normotensive ( p < 0.05) or hypotensive ( p < 0.05) groups, but did not differ significantly between the latter two groups ( Fig. 2 ).
The mean blood loss calculated according to B ourke & S mith was 811.59 ml (120–1660 ml) on postoperative day 3 in the hypotensive group, but was significantly higher at 1495.44 ml (53–3460 ml) in the normotensive group and 1198.90 ml (300–3086 ml) in the haemodilution group ( p < 0.05) ( Fig. 3 ). The calculated blood loss did not differ significantly between the normotensive and haemodilution groups ( Fig. 3 ).
