StomatologyEduJ 5(1) SEJ_5_1 | Page 49

hypotension. Bijker et al [60] in a literature review found more than 50 different definitions of intraoperative hypotension used in the recent anaesthesia literature. When it comes to controlled hypotension in the orthognathic literature, again no consensus is found as to what constitutes controlled hypotension and how it would differ from intraoperative hypotension. Bijker et al [61] found that patient and surgical characteristics, notably age and duration of surgery and duration of low blood pressure, influence the relationship between intraoperative hypotension and adverse outcome. Controlled hypotension is an anesthesiological technique to lower the mean arterial blood pressure of the patient in orthognathic surgery on the presumption that a lower blood pressure correlates with less blood loss and a better quality of the operation field. In the orthognathic literature, hypotension has not been related to adverse effects except for patients with pre-existing hypofunction. In these cases, cerebral damage or neurological deficit, stroke, dysrhythmia, cardiac arrest, or even death have been reported [32]. The absence of a common definition of hypotension, the different ways of measurement of arterial pressure, the different attitudes towards the intraoperative duration of hypotension, the timing to reverse hypotensive anaesthesia to discover and address undetected arterial hemorrhage [29], and the different means to achieve hypotension render comparisons between study groups difficult. An entire range encompassing aggressive attitudes (MAP 50–55 mm Hg), cautious attitudes (blood pressure 20%– 30% below mean preoperative level), and no deliberate hypotension is reported with orthognathic surgery. Measurement of mean arterial pressure was mostly done with the aid of measurements from a radial artery catheter. [45] calculated mean arterial pressure with the formula: systolic pressure × 2/5 + diastolic pressure × 3/5. No other mean arterial pressure measurement formula was found in the 50 other retained articles. Contemporary monitors measuring mean arterial pressure use the following formula: (diastolic pressure × 2) + systolic pressure) / 3. 3.6.1. Advantages of controlled hypotension Controlled hypotension has advocates and opponents. Arguments raised in favour of controlled hypotension are a shorter operation time, a better quality of the operation field, diminished blood loss, and lower blood transfusion. Others question the advantages of controlled hypotension [6]. Choi and Samman [32] studied that controversy with a systematic review and concluded in support of hypotensive anaesthesia, with three studies reporting a significant decrease of blood loss in patients receiving hypotensive anaesthesia, two studies reporting a significant decrease in transfusion rate, and two other studies demonstrating an improved surgical field and significant reduction in operation time. Their conclusion was that hypotensive anaesthesia is most valuable in operations of long duration when a large amount of blood loss and consequent blood transfusion are to be expected. 3.6.2. Minimizing perioperative bleeding Both surgeon and anesthesiologist have means at their disposal to affect coagulation, blood loss, and the quality of the surgical field. Stomatology Edu Journal - Anesthesiologist: • normovolemic hemodilution • application of Cell Saver Systems • carefully controlled body temperature • use of tranexamic acid (antifibrinolytic agent) as a clot stabiliser • use of aprotinin (serine protease inhibitor) • use of desmopressin, increasing coagulant activity • hypotensive anesthetic techniques • optimised tissue perfusion by administration of 500 mL of hydroxyethyl starch 6%/200/0.5 before segmentation of the maxilla [55] • atraumatic nasal intubation with heated nasal tubes • avoidance of trauma at adenoid fossa during intubation • preoperative injection of human recombinant erythropoietin (not routine in OMFS) • preoperative exclusion of bleeding disorders • maintaining hypocapnia - Surgeon: • avoiding perioperative vascular injury • bipolar electrocoagulation; cutting diathermy • use of an electrocautery unit to make incisions • skilled surgeons to perform the operation instead of residents • surgical vigilance • administration of local anaesthesia with vasoconstrictor immediately after intubation • timely administration of local anaesthesia in Le Fort I • fluid injection with vasoconstrictor subperiosteally at nasal floor • cocainisation of the nasal mucosa prior to maxillary surgery • vasoconstriction of intranasal lining with cottonoid sponges soaked in nasal decongestant • placement of the patient in a reverse Trendelenburg position • incisions that are cleanly made through the periosteum • packing of open surgical sites with gauze • local hemostatics like oxidised regenerated cellulose (Surgicel®, Ethicon Inc, Johnson&Johnson Company, Somerville, NJ, USA) • piezosurgical osteotome • endoscopic assistance for a controlled dissection of nasal mucosa [62] • hemostats and hemoclips • short duration of operation • instrumentation that allows suction with built-in light system • avoiding venous obstruction BLOODLOSS AND TRANSFUSION NEED IN ORTHOGNATHIC SURGERY: REVIEW OF LITERATURE 3.7. Excessive blood loss Reports concerning the need for blood transfusion also give some insight into the occurrence of excessive blood loss, either directly by explicit mention or by observation of the range of blood loss. Kok-Leng Yeow and Por [19] report 3 excessive bleedings in 102 orthognathic patients, occurring from the facial artery, maxillary artery, and pterygoid plexus separately in three patients. When we observ