[ effect of head flexion after endotracheal intubation on intraocular pressure, cardiovascular, and respiratory responses in patients undergoing cataract surgery]

ABSTRACT

During the cataract surgery, after induction of general anesthesia and endotracheal intubation [ETI], the periorbital area is prepared and draped. For this purpose, the patient's head and neck is usually flexed 30 to 45 degrees. Neck flexion causes displacement of the endotracheal tube tip toward the carina. Stimulation of the tracheal mucosa especially during light anesthesia may cause bucking, increase in intraocular pressure [IOP], laryngospasm and/or bronchospasm. Laryngeal constriction and all of the components of the tracheal response may have some effects on end-tidal carbon dioxide pressure [PETCO[2]] and peripheral arterial hemoglobin oxygen saturation [SpaO[2]]. In the current study, the influence of head and neck flexion after endotracheal intubation on the patients' heart rate [HR], systolic and diastolic blood pressure [SAP and DAP], SpaO[2], PETCO[2], and IOP was investigated for patients, who underwent cataract surgery during general anesthesia. In a double-blind clinical trial study, 106 patients aged 40-80 years were included according to ASA [American Social Anesthesia] physical status I and II. Anesthesia was induced with sodium thiopental, lidocaine and fentanyl. Atracurium 0.5 mg/kg was given to facilitate tracheal intubation. HR, SAP, DAP, SpaO[2], PETCO[2], and IOP were measured at 1, 2, and 5 minutes after head flexion. Data were then analyzed using Chi-Square and t-test, p< 0.05 was considered as significant. The means of SAP, DAP, IOP, and HR were increased after ETI, head flexion [p<0.05] and PETCO[2], SpaO[2] were decreased after ETI, also after 1 and 2 minutes head flexion compared with the baseline values [p<0.05]. It can be concluded from this study that for patients undergoing cataract surgery during general anesthesia, endotracheal tube movement along with changes in head and neck position may have a significant effect on heart rate, systolic and diastolic blood pressures, laryngeal reflexes, SpaO[2], PETCO[2], and intraocular pressure. Accordingly, an adequate monitoring of these vital parameters during anesthesia is warranted