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.
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.
Study Type
OBSERVATIONAL
Enrollment
100
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.
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.
Pirogov National Medical and Surgical Center
Moscow, Russia
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.
Time frame: during osteotomy, up to 90 minutes
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
Time frame: 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).
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: at the start of the surgery, during controlled hypotension phase, immediately after extubation
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