The potential use of hypotensive anaesthesia for maxillofacial surgery was first noted in the 1950s. Since then a number of studies have been reported on the effects of hypotensive anaesthesia in relation to blood loss operating time and surgical field quality producing conflicting results.
The aim of this review was to evaluate the efficacy of hypotensive anaesthesia in reducing intraoperative blood loss, decreasing operation time, and improving the quality of the surgical field during orthognathic surgery.
Methods
Searches were conducted in the PubMed, ProQuest, MEDLINE, Web of Science, Google Scholar, Current Controlled Trials (www.controlled-trials.com); US Clinical Trials (http://clinicaltrials.gov); Trials Central (www.trialscentral.org); CenterWatch (www. centerwatch.com); the UK Research register (http:// www.nihr.ac.uk) and the Cochrane Central Register of Controlled Trials (CENTRAL) databases.
Randomised controlled trials (RCTs) in ASA class I or II patients undergoing orthognathic surgery under hypotensive /normotensive anaesthesia and published in English were considered. The primary outcome was the amount of intraoperative blood loss during orthognathic surgery, secondary outcomes included duration of surgery and quality of the surgical field. Two reviewers independently selected studies, abstracted data and assessed study quality . The Jadad scale and a Delphi list of criteria were used to assess study quality. A random effect meta-analysis was conducted.
Results
- 10 RCTs involving a total of 358 patients were included.
- 2 studies were considered to be of high quality.
- Meta-analysis ((10 studies; 178 patients in hypotensive group and 180 in control) found hypotensive anaesthesia significantly reduced intraoperative blood loss compared with the control group mean difference (MD) = 168.98 mL, (95%CI; 228.19 -109.77 mL) P < .00001; I2 =56%.
- Meta-analysis (8 studies; 143 patients in hypotensive group and 139 in control) found no statistically significant reduction of operation time between the hypotensive group and control group. MD= -9.46 mins, (95%CI; -22.87 to 3.95 mins) P = 0.17 I2 = 9%.
- Meta-analysis (6 studies; 121 patients in the hypotensive group and 117 in control) showed a statistically significant improvement of quality of the surgical field compared with the control group; Standardised mean difference (SMD) = 0.66, (95% CI; 1.05 to 0.28) P = .0008; I2 = 52%.
- Subgroup analysis indicated that for blood loss in double-jaw surgery, the weighted mean difference favoured the hypotensive group, with a reduction in blood loss of 175 mL, but no statistically significant reduction in blood loss was found for anterior maxillary osteotomy. If local anaesthesia with epinephrine was used in conjunction with hypotensive anaesthesia, the reduction in intraoperative blood loss was increased to 254.93 mL.
Conclusions
The authors concluded
a statistically significant reduction of blood loss and improvement in the quality of the surgical field with hypotensive anaesthesia in orthognathic surgery. Hypotensive anaesthesia was not shown to reduce the operation time in orthognathic surgery. Findings from sub- group analysis suggested that when hypotensive anaesthesia was used in conjunction with local anaesthesia for nerve blocks, the reduction of intraoperative blood loss was enhanced.
Comments
The author shave undertaken and extensive search for studies for the review although restricting publication to those published in English may mean that some relevant studies could have been excluded. The Jadad scale was used as one of the study quality assessment tools and this is no longer a recommended approach. However, the Delphi List used considered many of the items included within the more usual Cochrane risk of bias tool. A sensitivity analysis was undertaken for the main outcomes using just the high-quality studies which suggests that the overall findings of the review are robust. It is interesting to note that the average reduction in blood loss found with hypotensive anaesthesia is very similar to that seen with the use of tranexamic acid (Dental Elf – 6th Aug 2015).
Links
Primary paper
Lin S, McKenna SJ, Yao CF, Chen YR, Chen C. Effects of Hypotensive Anesthesia on Reducing Intraoperative Blood Loss, Duration of Operation, and Quality of Surgical Field During Orthognathic Surgery: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. J Oral Maxillofac Surg. 2017 Jan;75(1):73-86. doi: 10.1016/j.joms.2016.07.012. Review. PubMed PMID: 27542543.
Other references
Olsen JJ, Skov J, Ingerslev J, Thorn JJ, Pinholt EM. Prevention of Bleeding in Orthognathic Surgery–A Systematic Review and Meta-Analysis of Randomized Controlled Trials. J Oral Maxillofac Surg. 2016 Jan;74(1):139-50. doi: 10.1016/j.joms.2015.05.031. Review. PubMed PMID: 26073131.
Dental Elf – 6th Aug 2015
Orthognathic surgery: intra-operative bleeding reduced with tranexamic acid
