Problem

Orthognathic surgery (OS) is widely accepted for correcting dentofacial deformities. It includes surgical manipulation of the facial skeletal components to readjust the anatomic and functional relationships in patients with dentofacial skeletal abnormalities [1], and bimaxillary osteotomies are frequently necessary to achieve an acceptable result. However, due to the rich blood supply in the head and neck region, considerable bleeding can occur from the incised soft tissues and bone during orthognathic surgery [2,3]. In addition, factors like prolonged procedure length, major vascular injury, and surgical inexperience can lead to an increase in the intraoperative bleeding (IOB) volume [4].

Because both anemia and allogeneic blood transfusions can increase postoperative morbidity, with several risks including the transmission of bacterial, viral, or protozoal infections and alloimmunization, in previous decades, IOB and the need for blood transfusions in OS has been prevented using different techniques such as hypotensive anesthesia (HA), and the use of antifibrinolytic agents [4–6].

HA is a method used in surgical practice by which blood pressure is decreased predictably and deliberately, and it was first described concerning maxillofacial surgery in 1950 by Enderby [2]. Controlled hypotension is defined as a reduction of the systolic blood pressure to 80-90 mm Hg, a decrease of mean arterial pressure (MAP) to 50-65 mm Hg, or a 30% reduction of baseline MAP [3].

Several clinical trials have been reported in the literature regarding the effects of HA on reducing blood loss, and operation time, and improving the quality of the surgical field for patients undergoing OS. However, there is a risk of hypoperfusion of vital organs during deliberate hypotension [3]. Furthermore, these studies have yielded conflicting results regarding the effectiveness of HA in reducing IOB, and the value of HA in OS remains controversial [2,5,7].

Methods

We used Epistemonikos database, which is maintained by screening more than 30 databases, to identify systematic reviews and their included primary studies. With this information we generated a structured summary using a pre-established format, which includes key messages, a summary of the body of evidence (presented as an evidence matrix in Epistemonikos), meta-analysis of the total of studies, a summary of findings table following the GRADE approach and a table of other considerations for decision-making.

Summary of findings

Information on the effects of hypotensive anesthesia is based on ten randomized controlled studies involving 358 patients. All the studies reported intraoperative blood loss, operation time and quality of the surgical field. The types of osteotomies included: anterior maxillary osteotomy, Le Fort I, bilateral sagittal split osteotomy, double jaw, and combined maxillary and mandibular osteotomy. All the studies evaluated the use of hypotensive agents compared with normotensive pressure.

• The use of hypotensive anesthesia in orthognathic surgery may reduce intraoperative blood loss (low certainty evidence).

• The use of hypotensive anesthesia in orthognathic surgery may make little or no difference to operation time (low certainty evidence).

• The use of hypotensive anesthesia in orthognathic surgery may improve the quality of surgical field (low certainty evidence).

• No studies were found that reported adverse effects or even mortality associated to hypotensive anesthesia in orthognathic surgery.

How we conducted this summary

Using automated and collaborative means, we compiled all the relevant evidence for the question of interest and we present it as a matrix of evidence (Figure 1)

Figura 1

Matrix of evidence.

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Follow the link to access the interactive version:

Notes

The upper portion of the matrix of evidence will display a warning of “new evidence” if new systematic reviews are published after the publication of this summary. Even though the project considers the periodical update of these summaries, users are invited to comment in Medwave or to contact the authors through email if they find new evidence and the summary should be updated earlier. After creating an account in Epistemonikos, users will be able to save the matrixes and to receive automated notifications any time new evidence potentially relevant for the question appears.

This article is part of the Epistemonikos Evidence Synthesis project. It is elaborated with a pre-established methodology, following rigorous methodological standards and internal peer review process. Each of these articles corresponds to a summary, denominated FRISBEE (Friendly Summary of Body of Evidence using Epistemonikos), whose main objective is to synthesize the body of evidence for a specific question, with a friendly format to clinical professionals. Its main resources are based on the evidence matrix of Epistemonikos and analysis of results using GRADE methodology. Further details of the methods for developing this FRISBEE are described here (http://dx.doi.org/10.5867/medwave.2014.06.5997)

The details about the methods used to produce these summaries are described here (http://dx.doi.org/10.5867/medwave.2014.06.5997)

Epistemonikos foundation is a non-for-profit organization aiming to bring information closer to health decision makers with technology. Its main development is Epistemonikos database (www.epistemonikos.org).