The Down Fracture (DF) in Le Fort I osteotomy, triggers a potent reflex whose afferences are mediated fundamentally through V2, and the efferences are mediated by the sympathetic as by the parasympathetic system.

We studied the effects of this reflex onto the hemodinamy of the patients trying to know the prevalence, the magnitude and the predominance of the changes produced.

Materials and methods: We studied 100 patients submitted to Le Fort I osteotomy, under inhalatory general anesthesia monitorized in the standard fashion. We did not used vasoactive or antiarrhythmic drugs previous to the DF, and we try to reach to that moment in a deep plane of anesthesia.

We used standard statistic for to analyze the results.

Results: Female 42%. Age 21.9 (15.7–28.1) years. None was a known hypertensive subject. ASA I 71%, ASA II and ASA III 2%. Bradycardia 5%; tachycardia 38%. No one patient developed a significant arrhythmia.

The Systolic Arterial Pressure dropped in 8 cases and raised in 47% been over 30 mmHg in 6. The Diastolic Arterial Pressure felled down significantly in 9 and rose in 52 overcoming 20 mmHg of variation in 44.

No specific treatment was needed.

Conclusions: The DF generates a potent reflex manifested even in conditions of very deep anesthesia. The majority of our patients were stable and in those who presented variations, predominated those compatible whit a trigeminal-sympathetic reflex mild in magnitude and short in duration.

Conflict of interest: None declared.