Blood flow velocity in the middle cerebral artery during transnasal endoscopic skull base surgery performed in controlled hypotension.

BACKGROUND AND PURPOSE: To assess blood flow velocity in the middle cerebral artery (MCA) during transnasal endoscopic procedures performed with decreased hemodynamic parameters. MATERIALS AND METHODS: In 40 patients who underwent endoscopic skull base surgery in controlled hypotension (studied group) and in 13 patients operated without reduction of hemodynamic parameters (control group), blood flow velocity in MCA was assessed with transcranial color Doppler sonography. RESULTS: Blood flow velocity in MCA remained within the range of age-specific reference values in all patients before operation. It decreased significantly in both groups after induction of anesthesia and then dropped even further in studied group of patients when hemodynamic parameters were reduced; the systolic velocity fell below the normal reference values in 25% of patients, the mean velocity in 50% and the diastolic velocity in 57% of patients. The diastolic velocity was much more heavily influenced by diminished hemodynamic parameters than systolic velocity in the studied group as opposed to the control group where reduction of blood flow velocity pertained equally systolic and diastolic velocity. CONCLUSION: During transnasal endoscopic procedures performed in moderate hypotension, in addition to significant drop of blood flow velocity to values well below the normal reference range, a divergent reduction of systolic and diastolic velocity was detected. Since divergent systolic and diastolic velocity may indicate an early phase of cerebral autoregulation compromise, and the decrease of mean blood flow velocity in MCA corresponds with a decrease of cerebral blood flow, further investigations in this field seem warranted.

[Reduction of intraoperative bleeding during functional endoscopic sinus surgery]. / Wspólczesne poglady na temat ograniczania krwawienia w polu operacyjnym w endoskopowej chirurgii zatok przynosowych.

Functional endoscopic sinus surgery (FESS) is a surgical procedure, during which all necessary manipulations are performed while using a fibreoptic camera. The endoscope is inserted together with the surgical instruments, through the nasal cavity. During the surgery, bleeding has to be minimized, since even a small amount of blood may completely obstruct vision via the endoscope. Various approaches have been used to secure a dry operating field; among them are: topical vasoconstrictors, Fowler's position, alpha-and beta-adrenergic blockade, and preoperative steroids. All these methods are far from being effective and are associated with significant side effects. The recently approved approach to this problem is to combine total intravenous anaesthesia using propofol and remifentanil, together with esmolol. With the heart rate reduced to 60 bpm, excellent operative conditions can be achieved with moderate hypotension (MAP 65 mm Hg-8.7 kPa). Altered microcirculation and a low cardiac output are the principal underlying mechanisms in these cases.

[The assessment of correlation between mean arterial pressure and intraoperative bleeding during endoscopic sinus surgery in patients with low heart rate]. / Ocena korelacji sredniego cisnienia tqtniczego z krwawieniem sródoperacyjnym przy wolnej czynnosci serca w trakcie endoskopowej chirurgii zatok przynosowych.

UNLABELLED: Induced controlled hypotension is a standard method aimed at decreasing intraoperative bleeding and achieving good operative field conditions. Low hemodynamic parameters during the operation are related to increased risk of brain hypoperfusion and injury to hypoxia-sensitive nerve cells. The purpose of this study was to find the mean arterial pressure (MAP) that preserves good operative conditions at low heart rate (HR) during endoscopic sinus surgery. MATERIAL AND METHOD: Twenty eight patients ASA I-II were anesthetized using remifentanil and sevoflurane. The anesthetist was attempting to keep the heart rate around 60 b/min. tried to diminish the MAP gradually until good operative field conditions were achived. The surgeon blinded to the HR and MAP values rated the bleeding in the operative field on the basis of Fromm and Boezzart scale. Spearman rank correlation coefficient was used to assess the statistical dependence between the variables. RESULTS: The best operative conditions were achieved in patients with the lowest MAP and HR. By keeping the HR at the level of 60 b/min in about 40% of patients very good and good operative field conditions were achieved at MAP higher than 65 mm Hg. There was a significant and strong correlation between the operative field conditions and MAP (Spearman rank correlation test, R = 0.54 p = 0.003). CONCLUSIONS: With the stable low heart rate at the minimal physiological values the bleeding in the operative field depends on MAP. Keeping HR around 60 b/min there is no need to decrease the MAP to dangerously low levels to achieve good operative field conditions in great proportion of patients.