Change in the optic nerve sheath diameter after deflation of a pneumatic tourniquet: a prospective observational study

Abstract

Applying a pneumatic tourniquet provides surgeons with a bloodless surgical field. However, application of the tourniquet induces various physiological changes. We evaluated the effect of tourniquet deflation on the intracranial pressure by using ultrasonography to measure the optic nerve sheath diameter (ONSD) in patients undergoing lower limb surgery. The ONSD was measured in 20 patients at five time points: after anesthetic induction (T0) and immediately before (T1), immediately after (T2), 5 min after (T3), and 10 min after tourniquet deflation (T4). Hemodynamic and respiratory variables were recorded. The ONSD showed significant differences at each point (P < 0.001). The ONSDs at T2 and T3 were significantly greater than that at T1 (P = 0.0007 and < 0.0001, respectively). The change in the end-tidal carbon dioxide partial pressure (EtCO2) was similar to the change in the ONSD. The change in the ONSD was significantly correlated with the change in the EtCO2 after tourniquet deflation (r = 0.484, P = 0.030). In conclusion, the ONSD, as an indicator of intracranial pressure, increased after tourniquet deflation in patients undergoing lower limb surgery. This was correlated with an increased EtCO2 and arterial carbon dioxide partial pressure.Trial registration: ClinicalTrials.gov (NCT03782077).

Effect of Tourniquet Deflation on Intracranial Pressure Measured by Ultrasound of the Optic Nerve Sheath Diameter in Patients Undergoing Orthopedic Surgery Under Spinal Anesthesia: An Observational Study

“…The ONSDs at T5 and T10 were significantly greater than that at T0 (p = 0.002). This study finding is consistent with that reported by Kim et al [15] where significant differences in ONSD were noted at each observation point. In our study, the highest difference in ONSD value was noted at T10 (10 minutes after the deflation of the tourniquet), which is contrary to that reported by Kim et al [15] as well as Besir et al [13] where the maximum changes in ONSD were observed at five minutes following the deflation of the tourniquet.…”

“…The use of pneumatic tourniquets in orthopedic surgery provides the benefits of reduced operating time and lesser blood loss during the procedure. The pH, arterial oxygen partial pressure (PaO 2 ), arterial carbon dioxide partial pressure (PaCO 2 ), potassium ion, and lactate levels fluctuate because of tourniquet inflation and deflation [15]. Tourniquet deflation results in the release of carbon dioxide (CO 2 ) into the systemic circulation that has collected during the ischemia phase.…”

“…A rise in ICP follows the resulting elevation in PaCO 2 . Although most healthy patients can compensate for and tolerate this increase in CBF, it may result in an increase in ICP in patients with impaired intracranial compliance [15]. Cerebral ischemia is one of the harmful effects of elevated ICP.…”

“…Cerebral ischemia is one of the harmful effects of elevated ICP. Therefore, patients undergoing lower limb surgery who have or are at high risk of cerebrovascular illness require careful monitoring and meticulous treatment of the ICP utilizing a pneumatic tourniquet [15].…”

“…Additionally, an increase in ONSD is a precursor to an increase in ICP, and a rise in ICP causes cerebrospinal fluid to move from the cerebral subarachnoid space into the optic subarachnoid space [20]. Therefore, the ONSD is helpful for keeping an eye on the ICP during surgery [15].…”