A Cohort Prospective Study of Predictors Influencing the Quality of Visualization of the Operating Field During Orthognathic Surgery

Study Overview
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Brief Summary
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It is very important to decrease the bleeding during bimaxillary osteotomy in order to increase the visibility of the surgical site. Our primary goal is to investigate the predictive value of pre- and perioperative factors, including controlled hypotension, on visibility of surgical site during bimaxillary osteotomy.

Detailed Description
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100 patients undergoing bimaxillary osteotomy under general anesthesia will be included into this prospective cohort study. There will be two episodes of controlled hypotension for upper and lower jaw respectively. Hypotension will be induced and sustained according to the same procedure as described here. Controlled hypotension will be induced (intravenous administration of nitroglycerin 2-10 µg/kg/min) 15 minutes prior to the start of mucosal detachment, and will be sustained for the osteotomy stage. The surgeon will evaluate the surgical field quality (in terms of bleeding) according to Modena Bleeding Score (MBS), with scores 1-2 being satisfactory to proceed with the osteotomy. The following arterial pressure correction (proceeding with controlled hypotension or returning to normotension) will depend on the bleeding in the surgical field and the monitoring of cerebral oxygen saturation carried out using near-infrared spectroscopy (NIRS) . The lowest targeted arterial pressure in order to have a clear surgical field will be 55 mmHg. However when the cerebral oxygen saturation decreases by 20% compared with the baseline at any arterial pressure level intervention would be carried out by Norepinephrine (intravenous, individual dosage for each patient - as judged by the anesthesiologist). Arterial blood samples will be taken at 3 time points (at the start of the surgery, during controlled hypotension phase, after extubation) for arterial gas analysis. Two blood samples will be taken to measure (prior to surgery and immediately after surgery) neuron-specific enolase (NSE), cystatin c and troponin I levels. The general condition, operation, anesthesia and hospitalization related data of the patients will be recorded. Cognitive function will be evaluated within 3 days before surgery and 2 days and 1 month after surgery.

Official Title
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A Cohort Prospective Study of Predictors Influencing the Quality of Visualization of the Operating Field During Orthognathic Surgery

Conditions
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Malocclusion, Maxillofacial Injuries, Orthodontics, Hemorrhage

Intervention / Treatment
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* Drug: Nitroglycerin solution
* Device: monitoring of cerebral oxygen saturation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients refered for bimaxillary osteotomy under general anesthesia with endotracheal intubation; Anesthesia risk classes (ASA) I and II; Written statement of informed consent. Exclusion Criteria: Hypertension as a symptom of hypertensive heart disease or endocrine dysfunction; Patients receiving antihypertensive drugs; Patients receiving anticoagulant therapy; Ischemic heart disease; Cerebrovascular insufficiency; Severe hypovolemia; Anemia; BMI 30 kg/m2 and higher; Connective tissue disorders; Pregnancy; Participation in other clinical studies; Recent history of substance abuse (recreational drugs, alcohol); Allergies to drugs used in the study; Anxiety requiring psychiatrist supervision and pharmacological therapy.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 40 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Patients undergoing bimaxillary osteotomy under general anesthesia<br> | Drug: Nitroglycerin solution<br>* Controlled hypotension will be induced (intravenous administration of nitroglycerin 2-10 µg/kg/min) 15 minutes prior to the start of mucosal detachment, and will be sustained for the osteotomy stage.<br>Device: monitoring of cerebral oxygen saturation<br>* NIRS-based monitoring of rSO2 has unique advantages: directly or indirectly detecting physiological changes and metabolic processes, it is easy to realize, and involves simple procedures.<br>* Other names: NIRS;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Visibility of surgical site | Surgical site will be rated according to Modena Bleeding Score (MBS) by the same surgeon in terms of bleeding during osteotomy. The MBS goes from Grade 1 - no bleeding to Grade 5 - bleeding that prevents every surgical procedure except those dedicated to bleeding control. | during osteotomy, up to 90 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Proportion of patients with cerebral desaturation | Proportion of patients with decrease in cerebral oxygen saturation decreased by 20% compared with the baseline for 300 seconds without improvement | during osteotomy, up to 90 minutes | 
| changes in the values of mean arterial pressure | Changes in mean arterial pressure (MAP) values before and during controlled hypotension phase will be registered. MAP calculated as follows: MАP = Diastolic blood pressure + ((Systolic blood pressure - Diastolic blood pressure) / 3). | during the whole surgery (from start to finish - the timing stated in the surgery protocol) | 
| Changes in neuron-specific enolase (NSE) concentration | NSE is released from neurons during injury and it's high blood concentration is associated with ischemic brain injury. Level of NSE will be measured in blood samples taken during surgery. Increase of NSE level suggests brain ischemia. | 3 time-points during the surgery - immediately after anesthesia induction, at the time of controlled hypotension (5 minutes after induction of controlled hypotension, i.e. nitroglycerin i.v. administration), immediately after extubation | 
| Intraoperative blood loss | Total volume of blood loss during the time of surgery, calculated using direct volumetric measurement. | during the whole surgery (from start to finish - the timing stated in the surgery protocol) | 
| Cognitive status change | Cognitive function will be evaluated by means of Mini Mental State Examination (MMSE), which is a 30-point test, validated and commonly used to measure cognitive impairment. Any score of 24 or more (out of 30) indicates a normal cognition. Below this, scores can indicate severe (≤9 points), moderate (10-18 points) or mild (19-23 points) cognitive impairment. | within 3 days before operation, 2 days after surgery, 1 month after surgery | 
| Changes in cystatin C concentration | Cystatin C is a well investigated biomarker with clear advantages over serum creatinine in patients with extremes in muscle mass, weight, age, and other areas where estimating equations using creatinine have well documented limitations. Increase of cystatin C level suggests kidney impairment. | at the start of the surgery, during controlled hypotension phase, immediately after extubation | 
| Change in Troponin I concentration | The test can be used to aid in diagnosing myocardial infarction. | at the start of the surgery, during controlled hypotension phase, immediately after extubation | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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nitroglycerin, the quality of visualization of the operating field, Near-infrared Spectroscopy (NIRS), cerebral oximetry, regional cerebral oxygen saturation (rSO2), Le Fort; I, controlled hypotension anesthesia