Relation between partial arterial carbon dioxide pressure and pH value and optic nerve sheath diameter: a prospective self-controlled non-randomized trial study

[Small tidal volume hyperventilation relieves intraocular and intracranial pressure elevation in prone spinal surgery: a randomized controlled trial]

OBJECTIVE

To investigate the effects of different ventilation strategies on intraocular pressure (IOP) and intracranial pressure in patients undergoing spinal surgery in the prone position under general anesthesia.

METHODS

Seventy-two patients undergoing prone spinal surgery under general anesthesia between November, 2022 and June, 2023 were equally randomized into two groups to receive routine ventilation (with Vt of 8mL/kg, Fr of 12-15/min, and etCO2 maintained at 35-40 mmHg) or small tidal volume hyperventilation (Vt of 6 mL/kg, Fr of18-20/min, and etCO2 maintained at 30-35 mmHg) during the surgery. IOP of both eyes (measured with a handheld tonometer), optic nerve sheath diameter (ONSD; measured at 3 mm behind the eyeball with bedside real-time ultrasound), circulatory and respiratory parameters of the patients were recorded before anesthesia (T0), immediately after anesthesia induction (T1), immediately after prone positioning (T2), at 2 h during operation (T3), immediately after supine positioning after surgery (T4) and 30 min after the operation (T5).

RESULTS

Compared with those at T1, IOP and ONSD in both groups increased significantly at T3 and T4(P < 0.05). IOP was significantly lower in hyperventilation group than in routine ventilation group at T3 and T4(P < 0.05), and ONSD was significantly lower in hyperventilation group at T4(P < 0.05). IOP was positively correlated with the length of operative time (r=0.779, P < 0.001) and inversely with intraoperative etCO2 at T3(r=-0.248, P < 0.001) and T4(r=-0.251, P < 0.001).ONSD was correlated only with operation time (r=0.561, P < 0.05) and not with IOP (r=0.178, P>0.05 at T3; r=0.165, P>0.05 at T4).

CONCLUSION

Small tidal volume hyperventilation can relieve the increase of IOP and ONSD during prone spinal surgery under general anesthesia.

Additional predictive value of optic nerve sheath diameter for neurological prognosis after cardiac arrest: a prospective cohort study

BACKGROUND

The goal is to estimate the additional value of ultrasonographic optic nerve sheath diameter (ONSD) measurement on days 1-3, on top of electroencephalography (EEG), pupillary light reflexes (PLR), and somatosensory evoked potentials (SSEP), for neurological outcome prediction of comatose cardiac arrest patients. We performed a prospective longitudinal cohort study in adult comatose patients after cardiac arrest. ONSD was measured on days 1-3 using ultrasound. Continuous EEG, PLR, and SSEP were acquired as standard care. Poor outcome was defined as cerebral performance categories 3-5 at 3-6 months. Logistic regression models were created for outcome prediction based on the established predictors with and without ONSD. Additional predictive value was assessed by increase in sensitivity for poor (at 100% specificity) and good outcome (at 90% specificity).

RESULTS

We included 100 patients, 54 with poor outcome. Mean ONSD did not differ significantly between patients with good and poor outcome. Sensitivity for predicting poor outcome increased by adding ONSD to EEG and SSEP from 25% to 41% in all patients and from 27% to 50% after exclusion of patients with non-neurological death.

CONCLUSIONS

ONSD on days 1-3 after cardiac arrest holds potential to add to neurological outcome prediction.

TRIAL REGISTRATION

clinicaltrials.gov, NCT04084054. Registered 10 September 2019, https://www.

CLINICALTRIALS

gov/study/NCT04084054 .

Diagnostic Accuracy of Optic Nerve Sheath Diameter Measured With Ocular Ultrasonography in Acute Attack of Chronic Obstructive Pulmonary Disease

OBJECTIVE

The study aimed to evaluate intracranial pressure changes by measuring ONSD before and after treatment in patients with chronic obstructive pulmonary disease (COPD).

METHODS

The study was designed as a prospective analysis, in which 56 COPD in acute exacerbation and 50 volunteers. COPD severity was determined by the Dyspnea Scale of Modified Medical Research Council (mMRC). Measurements were made with ocular ultrasonography and linear probe in both eyes.

RESULTS

Both the right and left ONSDs were higher in the patient compared to the control (P = .017) and regressed after the treatment (P = .021). In the ROC analysis for the predictability of COPD, right eye ONSDs showed a predictive potential for COPD with %75.7 specificity and %68.1 sensitivity at 0.455 cut-off (AUC: 0.727; P = .0001; %95CI: 0.609-0.833). Similar to the right eye, the left ONSD presented %74.4 specificity and %67 sensitivity at 0.505 cut-off value (AUC: 0.718; P = .0001; %95CI: 0.608-0.841).

CONCLUSION

The ONSD measurement that was with the help of ocular ultrasonography can be a useful diagnostic tool for symptomatic COPD presenting with an acute attack.

The Association Between Hyponatremia and Optic Nerve Sheath Diameter: A Prospective Study

Background Hyponatremia is a common electrolyte balance disorder. It may result in brain edema and increased intracranial pressure (ICP). Optic nerve sheath diameter (ONSD) measurement remains an increasingly sought-after method in many situations associated with ICP elevations. The aim of our study was to investigate the relationship between the change of ONSD before and after hypertonic saline (3% sodium chloride) treatment and the clinical improvement with increased sodium levels in patients with symptomatic hyponatremia who presented to the emergency department. Methodology This study was conducted in the emergency department of a tertiary hospital, according to the design of a prospective, self-controlled, non-randomized trial study. Determined by power analysis, 60 patients were included in the study. The statistical analysis of the continuous data was performed using the means, standard deviations, and minimum and maximum values of the feature values. The frequency and percentage values were used to define categorical variables. The mean difference comparison of pre-and post-treatment measurements was evaluated by paired t-test. P<0.05 was considered to be significant. Results The measurement parameters' differences before and after hypertonic saline treatment were evaluated. While the mean of the right eye ONSD was 5.27±0.22 mm before treatment, it declined substantially to 4.52±0.24 mm after treatment (p<0.001). It was also found that the left eye ONSD was 5.26±0.23 mm before the treatment and declined to 4.53±0.24 mm after the treatment (p<0.001). In addition, the mean of the overall ONSD was 5.26±0.23 mm before treatment and 4.52±0.24 mm after treatment (p<0.001). Conclusions Ultrasonic measurement of ONSD can be used to monitor the clinical improvement of patients receiving hypertonic saline therapy for symptomatic hyponatremia.