Correlation of Positive End-Expiratory and Intracranial Pressure Using the Ultrasonographic-Guided Measurement of Optic Nerve Sheath Diameter in Traumatic Brain Injury Patients.

BACKGROUND: In brain injury patients, positive end-expiratory pressure (PEEP) may potentially increase the intracranial pressure (ICP). ICP can be noninvasively assessed from the sonographic measurement of the optic nerve sheath diameter (ONSD). Herein, we aim to evaluate the association between PEEP and ICP via measuring ONSD in traumatic brain injury (TBI) patients. METHODS: TBI patients with age ≥18 years, severe brain injury (GCS 8 or less), receiving mechanical ventilation, initial PEEP ≤4 mmHg and no history of severe cardiopulmonary disease were included in this study. Patients with intracranial hypertension (defined as ICP >20 mmHg) and already receiving PEEP >15 cm H2O at enrollment were excluded from the study. ONSD measurement was performed when hemodynamic parameters were most stable. Variables included central venous pressure, invasive blood pressure, heart rate, saturation, and ventilator parameters. RESULTS: The ONSD and ICP did not increase significantly while PEEP increased from 0-5 cm and 5-10 cm H2O. However, ONSD and ICP significantly increased when PEEP increased from 10-15 cm H2O. There was no significant difference noted while comparing measurements of optic nerve sheath (ONS) diameter in both eyes at all PEEP values in cases as well as control patients. Mean arterial pressure (MAP) decreased with an increase in PEEP value. Highly significant decrease occurred in MAP change from PEEP 10-15 in cases (P < 0.001) and control (P < 0.001). CONCLUSIONS: The PEEP up to 10 cm H2O can be safely applied in patients with TBI. In addition, the increment of PEEP might further increase the oxygenation, at the cost of ICP accentuation.

Effect of Two Different Doses of Dexmedetomidine on the Hemodynamics of "Hypertensive Patients" Undergoing Laparoscopic Cholecystectomy.

CONTEXT: In laparoscopic cholecystectomy, pneumoperitoneum results in tachycardia, hypertension, and increased myocardial oxygen demand. These changes are more pronounced in hypertensive patients. The intravenous administration of dexmedetomidine attenuates sympathoadrenal response and provides better hemodynamic stability intraoperatively. AIMS: To evaluate the hemodynamic stabilizing and sedation properties of two different doses of dexmedetomidine including 0.7 µg.kg-1.h-1 and 0.5 µg.kg-1.h-1 in hypertensive patients undergoing laparoscopic cholecystectomy. SETTINGS AND DESIGN: This was a randomized, prospective, double-blind controlled trial. SUBJECTS AND METHODS: A total of 60 controlled hypertensive patients of either sex, aged 30-60 years, and ASA class 2 without any other serious comorbid conditions who were undergoing laparoscopic cholecystectomy under general anesthesia were randomly assigned into three groups of 20 each. Group A and B received loading dose of dexmedetomidine 1 µg.kg-1 over 10 min and maintenance dose at 0.7 and 0.5 µg.kg-1.h-1, respectively. Group C received normal saline infusion only. Hemodynamic parameters (heart rate and systolic, diastolic, and mean arterial pressure) and sedation score were compared at different time intervals among groups. STATISTICAL ANALYSIS USED: The Chi-square test, ANOVA, and Tukey Post hoc Test. RESULTS: Fluctuations in the hemodynamics of hypertensive patients are effectively attenuated by dexmedetomidine and there is no difference in the attenuation of these hemodynamic changes by maintenance dose of 0.5 or 0.7 µg.kg-1.h-1. However, maintenance dose of 0.5 µg.kg-1.h-1 causes lesser sedation. CONCLUSIONS: Dexmedetomidine administered as infusion in a maintenance dose of 0.5 µg.kg-1.h-1 serves as an ideal anesthetic adjuvant in hypertensive patients undergoing laparoscopic cholecystectomy.