Baseline Optic Nerve Sheath Diameter Research Articles

Evaluation of the association between the optic nerve sheath diameter and extracorporeal life support time during cardiac surgery in newborns.

Congenital heart disease (CHD), a birth defect, is a major cause of neonatal mortality; however, improvements in surgical procedures and medical treatments have resulted in decreased mortality rates. Nonetheless, postoperative morbidity, particularly cerebral dysfunction, remains an issue in patients receiving extracorporeal life support (ECLS) for cardiac surgeries. Herein, we aimed to assess the association between optic nerve sheath diameter (ONSD) and ECLS time in newborns receiving ECLS for cardiac surgery. We enrolled 25 newborn patients who received ECLS for cardiac surgery at our hospital. ONSD was measured at four different time points during the surgery: baseline (T1), 15 min after cross-clamping (T2), after displacement of cross-clamping (T3) and at the end of the surgery (T4). Furthermore, the ECLS time, aortic cross-clamp time, and surgery time were recorded. The regression analysis revealed a significant association between ONSD and ECLS time, cross-clamp time and surgery time. The correlation analysis showed strong associations between baseline ONSD and ONSD at T2, T3, and T4. Moreover, ONSDs significantly increased at T2 compared with those at baseline during cardiac surgery. Our findings suggest an association between ONSD and ECLS time in newborns receiving ECLS for cardiac surgery. Monitoring ONSD may provide valuable information about intracranial pressure changes in these patients.

Effect of intravenous administration of 20% Mannitol on optic nerve sheath diameter in patients with raised intracranial pressure

Background and aims: Mannitol is commonly used to reduce elevated intracranial pressure (ICP) in patients with traumatic brain injury, intracranial hemorrhage and acute cerebrovascular accident. Optic nerve sheath diameter (ONSD) has high sensitivity and specificity in diagnosing raised ICP. This study aims to evaluate effect of Mannitol on ONSD in patients with raised ICP.
 Methods: This was a prospective cohort observational study of adult patients receiving osmotherapy for increased ICP admitted to the ICU. Baseline ONSD (T1) was recorded bilaterally followed by administration of Mannitol. ONSD was remeasured bilaterally at 30 (T2), 60 (T3) and 120 (T4) minutes after completion of administration of mannitol. Peak inspiratory pressures and PEEP were recorded for patients on mechanical ventilation.
 Results: Of the 40 patients included in the study, the mean age of patients was 54.03 ±19.15 years. Among them 26 were mechanically ventilated. Compared to the baseline values of 6.1 ± 0.74 mm, the mean ONSDs at T2, T3 and T4 were significantly lower after administration of 20% Mannitol with all p values < 0.001. A statistically significant correlation between change in ONSD (ΔONSD) at each time point and the dose of Mannitol administered was observed.
 Conclusion: ONSD can be used for monitoring effectiveness of osmotherapy on a point-of-care basis in patients with elevated ICP.

Analysis of dynamic changes in optic nerve sheath diameter (ONSD) with ultrasound in post-craniotomy patients: Trends and correlation with computed tomography ONSD and Glasgow coma scale in post-operative period.

Intracranial pressure (ICP) monitoring in patients with intracranial tumors undergoing craniotomy is usually done in perioperative period in intensive care unit. Invasive measurement of ICP, though considered as the gold standard, has its own limitations such as availability of expertise, equipment, and associated complications. Period of raised ICP in post-operative period may impact patient outcomes. Post-craniotomy computed tomography (CT) assessment is done routinely and may need to be repeated if indicated during post-operative stay. Utility of sonographic serial optic nerve sheath diameter (ONSD) assessment in post-operative monitoring of patients who have undergone elective craniotomy was explored in this study. The primary objective of the study was to measure the dynamic change in ONSD as compared to baseline pre-operative measurement in the first 3 postoperative days after elective craniotomy. The secondary objective of the study was to evaluate correlation between ONSD value with Glasgow Coma Scale (GCS) and post-operative CT findings. In this prospective, observational, and cohort study, we studied adult patients undergoing craniotomy for intracranial tumors. GCS assessment and sonographic measurement of ONSD were done preoperatively, immediate post-operative period, and 12, 24, and 48 h after surgery. CT scan to detect raised ICP was done at 24 h post-operative. Correlation of ONSD with GCS at respective period and correlation of CT scan finding with respective ONSD assessment were evaluated. A total of 57 patients underwent elective craniotomy for intracranial tumors. Significant difference was observed in ONSD value depending on time of measurement perioperatively (χ2 = 78.9, P = 0.00). There was initial increase in the first 12 h followed by decrease in ONSD in the next 48 h. Negative correlation was observed between baseline ONSD and 12 h GCS (ρ = -0.345, P = 0.013). There was significant change in GCS scores based on the status of ONSD (raised or normal) at 12 h after surgery (P = 0.014). Significant correlation between USG ONSD and CT ONSD was observed (ρ = 0.928, P = 0.000). Optimal cutoff value of ONSD to detect raised ICP with reference to CT signs was 4.8 mm with 80% sensitivity and 95% specificity. ONSD undergoes dynamic changes, correlates with CT scan, and has good diagnostic accuracy to detect raised ICP post-craniotomy for intracranial tumors. It may serve as a useful tool in monitoring in resource-limited setup.

Optic Nerve Sheath Diameter Affected by Cervical Collar Placement in Minor Head Trauma Patients

Background: Head trauma may cause an increase in intracranial pressure (ICP). The use of ocular ultrasound to measure optic nerve sheath diameter (ONSD) is a method to determine the ICP. The use of the rigid cervical collar in head trauma patients contribute to elevating ICP, and therefore, potentially causing further deterioration in their condition. Objectives: This study aimed to describe changes in ONSD after the placement of a c-collar and analyze these changes depending on the time in the c-collar. Methods: This prospective study measured the ONSD of minor head trauma patients before and after the placement of a c-collar. Patients aged ³18 with blunt head trauma and Glasgow Coma Score ³13 were included in the study. Each eye was scanned twice. This was done before c-collar placement, at 5 and 20 min after placement. The mean values of both eyes were calculated and analyzed. Results: This study investigated 50 patients. The mean baseline ONSD was obtained at 4.71mm±0.22 (4.54-4.77). Furthermore, T5 and T20 measurements were 5.19±0.41 (5.07-5.31) and 5.26±0.45 (5.14-5.39), respectively. The ONSD increased at T5 and T20. The changes from the baseline measurements were statistically significant (P=0.000, P=0.000). The difference between T5 and T20 groups was an increase in ONSD, and these differences were also statistically significant (0.07±0.19; P=0.008). Conclusion: Our results revealed that minor head trauma patients using a c-collar may increase ONSD by timeline the clinical effects of which have to be determined with further studies. Enlargement in ONSD should be considered when interpreting ICP.

Assessment of intracranial pressure with ultrasonographic measurement of optic nerve sheath diameter on patients undergoing suspension direct laryngoscopy.

The study aims to examine the effect on intracranial pressure by calculating the optic nerve sheath diameter (ONSD) using ultrasound in patients who underwent suspension direct laryngoscopy. Thirty-three patients who underwent suspension direct laryngoscopy were included in this prospective observational study. ONSD measurement was performed using a high-frequency linear probe. The ONSD basal (T0) value was determined using ultrasound in the supine position before the induction. Ultrasonography was used to record ONSD in the Boyce Jackson position (T1) just before inserting the laryngeal blade, in the Boyce Jackson position just before removing the laryngeal blade (T2), and in the supine position (T3) just before extubation. A statistically significant rise (p < 0.001) was seen between the patients' baseline ONSD values and the values at T1, T2, and T3. The optic nerve sheat diameter level recorded prior to withdrawing the laryngeal blade (T2) was considerably greater than the ONSD level calculated instantly before insertion of the laryngeal blade (T1) (p < 0.001). The ONSD value prior to extubation (T3) following the removal of the laryngeal blade was considerably smaller than the ONSD value prior removing the laryngeal blade (T2) (p < 0.001). This study found that when the laryngeal blade is mounted during the suspension direct laryngoscopy surgery, there is a significant increase in ultrasonographically measured ONSD and increased the ONSD even further during the time the mouth gag was remained in situ. This is the first research to indicate that measuring ONSD with ultrasonography during suspension direct laryngoscopy raises intracranial pressure.

Study of Changes in Optic Nerve Sheath Diameter Following Tracheal Intubation Using Macintosh Laryngoscope or Fibreoptic-Guided Intubation Through Ambu Aura-I: A Randomised Controlled Study.

Background: Neuroanaesthesiologists are faced with managing and optimising the intracranial pressure in the perioperative period. Laryngoscopy and tracheal intubation are known to increase sympathetic activity that is well tolerated by healthy patients but may be detrimental to many comorbid patients. We, therefore, hypothesised that airway management and tracheal intubation through Ambu Aura-I (Ambu, Baltorpbakken 13, Denmark) may be associated with lesser changes in optic nerve sheath diameter (ONSD) compared to conventional tracheal intubation and designed a study to ultrasonographically measure the changes in optic nerve sheath diameter following tracheal intubation using Macintosh laryngoscope or fibreoptic-guided intubation through Ambu Aura-I in patients receiving endotracheal anaesthesia.Material and methods: This randomised controlled hospital-based clinical study was conducted on 60 patients divided into two groups: group 1 (n=30, tracheal intubation facilitated by direct laryngoscopy with Macintosh laryngoscope) or group 2 (n=30, fibreoptic-guided tracheal intubation through Ambu Aura-I), undergoing elective surgery under general anaesthesia requiring tracheal intubation.Results: Baseline parameters before induction of anaesthesia were recorded for further comparison. Baseline ONSD at 3 mm behind the globe in both eyes (before induction of anaesthesia), both in transverse and the coronal plane, was measured by transorbital sonography with the patient lying in the supine position using a portable Sonosite Turbo-M ultrasonography (Fujifilm Sonosite, Bothell, USA) machine. End-tidal carbon dioxide concentration (EtCO2) was also recorded at this time. Observations of HR, systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MBP), oxygen saturation (SpO2), EtCO2, and ONSD measurements were recorded immediately and at three and five minutes after intubation, and complications were recorded. Data collected were tabulated, and statistical analysis was done using SPSS 22.00 for windows (SPSS Inc, Chicago, USA). The ONSD increase peaked at 4.19±0.35 and 4.16±0.31 mm in right and left eyes. Like in group 1, the ONSD decreased slightly to 4.06±0,29 and 4.05±0.29 mm in right and left eyes in group 2 at 10 minutes after intubation. The changes in ONSD when compared to baseline values (before intubation) were statistically not significant (p>0.05). Between-group comparison in ONSD in both the eyes at different time intervals was statistically not significant (p>0.05).Conclusion: We conclude that fibreoptic-guided tracheal intubation through Ambu Aura-I is not superior to tracheal intubation using direct laryngoscopy with Macintosh laryngoscope in terms of its effect on intracranial pressure, as measured ultrasonographically by optic nerve sheath diameter.

Correlation between optic nerve sheath diameter and extracorporeal life support time

IntroductionThe objective of the study was to analyse the correlation between extracorporeal life support (ECLS) and aortic cross-clamp times and optic nerve sheath diameter (ONSD). Patients and methodsStudy in a cohort of patients aged 0–15 years that underwent ECLS for cardiac surgery after obtention of signed informed consent. We calculated a sample size of 23 participants. First, we obtained 3 vertical and 3 horizontal measurements of the ONSD for each eye and calculated the mean of both eyes for each measurement to be used in the analysis. The measurements were made at admission and at 6 and 24 h post surgery. We retrieved the ECLS time and the aortic cross-clamp time were from the operative report. ResultsWe analysed data for 23 participants, 52.2% female, with a median age of 14 months. The median ECLS time was 60 min; the median aortic cross-clamp time was 32 min. The median baseline ONSD was 3.1 mm. ONSD values had increased a median of 0.015 mm at 6 h post surgery (P = .03). We found a positive correlation between ECLS time and ONSD values (r = 0.476, P < 0,05). The ONSD values returned to baseline by 24 h post surgery. None of the patients developed signs or symptoms of increased intracranial pressure. ConclusionOur study found a correlation between ECLS time and ONSD at 24 h post surgery. We found variations in the ONSD even in patients without signs or symptoms of increased ICP. Further research is required to identify the factors related to these variations.

Correlación del diámetro de la vaina del nervio óptico y el tiempo de circulación extracorpórea

IntroductionThe objective of the study was to analyse the correlation between extracorporeal life support (ECLS) and aortic cross-clamp times and optic nerve sheath diameter (ONSD). Patients and methodsStudy in a cohort of patients aged 0 to 15 years that underwent ECLS for cardiac surgery after obtention of signed informed consent. We calculated a sample size of 23 participants. First, we obtained 3 vertical and 3 horizontal measurements of the ONSD for each eye and calculated the mean of both eyes for each measurement to be used in the analysis. The measurements were made at admission and at 6 and 24hours post surgery. We retrieved the ECLS time and the aortic cross-clamp time were from the operative report. ResultsWe analysed data for 23 participants, 52.2% female, with a median age of 14 months. The median ECLS time was 60minutes; the median aortic cross-clamp time was 32minutes. The median baseline ONSD was 3.1mm. ONSD values had increased a median of 0.015mm at 6hours post surgery (P=.03). We found a positive correlation between ECLS time and ONSD values (r=0.476, p<,05). The ONSD values returned to baseline by 24hours post surgery. None of the patients developed signs or symptoms of increased intracranial pressure. ConclusionOur study found a correlation between ECLS time and ONSD at 24hours post surgery. We found variations in the ONSD even in patients without signs or symptoms of increased increased intracranial pressure. Further research is required to identify the factors related to these variations.

Sonographic Optic Nerve Sheath Diameter Following Seizure Prophylaxis in Pre-Eclamptic Parturients With Severe Features: A Prospective, Observational Study.

Neurological manifestations, including raised intracranial pressures, are a hallmark of worsening pre-eclampsia. Invasive methods for measuring intracranial pressure, though a gold standard, are not always a viable option. Maternal ocular sonography is a promising bedside tool, which serves as a noninvasive, cost-effective means for measuring optic nerve sheath diameter (ONSD), a surrogate marker of raised intracranial pressures. We studied the ultrasonographically measured ONSD in severely pre-eclamptic women, and the effect of magnesium sulfate therapy on its values. Thirty severely pre-eclamptic women at ≥28 weeks gestation were included. We recorded baseline ONSD values, serum magnesium levels, neurological symptoms, vitals, and repeated them at 4 and 12 hours following magnesium sulfate therapy, and then at 24 hours postpartum. An ONSD value >5.8 mm was suggestive of raised intracranial pressure. Primary outcome measure was to evaluate changes in ultrasonographically measured ONSD following seizure prophylaxis with magnesium sulfate. Women, 73.3%, had baseline ONSD >5.8 mm, with mean diameter being significantly high (6.02 ± 0.77 mm). There was a statistically nonsignificant decline in mean ONSD values at 4 and 12 hours, as well as at 24 hours postpartum. Patients with neurological symptoms declined significantly (from 70 to 10%; p value <.001) following magnesium sulfate therapy. Majority of severely pre-eclamptic parturients had high ONSD value suggestive of raised intracranial pressures, which persisted in the postpartum period and was unaffected by magnesium sulfate therapy. Ultrasound can thus serve as a point-of-care, cost-effective, easily available bedside tool for indirectly measuring intracranial pressures in this high-risk population.

Optic Nerve Sheath Ultrasound for the Detection and Monitoring of Raised Intracranial Pressure in Tuberculous Meningitis.

BackgroundNeurological complications of tuberculous meningitis (TBM) often lead to raised intracranial pressure (ICP) resulting in high morbidity and mortality. Measurement of optic nerve sheath diameter (ONSD) by point-of-care ultrasound may aid in the identification of raised ICP in TBM.MethodsFrom June 2017 to December 2019, 107 Vietnamese adults with TBM, enrolled in the ACT HIV or LAST ACT trials (NCT03092817, NCT03100786), underwent ONSD ultrasound at ≥1 of days 0, 3, 7, 14, 21, and day ±30 after enrollment. Demographic data, TBM severity grade, HIV coinfection status, and clinical endpoints by 3 months were recorded. ONSD values were correlated with disease severity, baseline brain imaging, cerebrospinal fluid parameters, and clinical endpoints.Results267 ONSD ultrasound scans were performed in 107 participants over the first 30 days of treatment, with measurements from 0.38–0.74 cm. Paired baseline ONSD and brain imaging were performed in 63 participants. Higher baseline ONSD was associated with more severe disease and abnormal brain imaging (abnormal imaging 0.55 cm vs 0.50 cm normal imaging, P = .01). Baseline median ONSD was significantly higher in participants who died by 3 months (0.56 cm [15/72]) versus participants who survived by 3 months (0.52 cm [57/72]) (P = .02). Median ONSD was higher at all follow-up times in participants who died by 3 months.ConclusionsHigher ONSD was associated with increased disease severity, brain imaging abnormalities, and increased death by 3 months. ONSD ultrasound has a potential role as a noninvasive, affordable bedside tool for predicting brain pathology and death in TBM.

Ultrasound measurement of optic nerve sheath diameter pre- and post-lumbar puncture

BackgroundTo test the hypothesis that optic nerve sheath diameter (ONSD) correlates with real-time changes in intracranial pressure, we performed ultrasound measurements of the ONSD in ambulatory patients undergoing elective lumbar puncture (LP). We conducted a prospective cohort study, including adult patients undergoing LP in a non-emergent setting. We measured ONSD perpendicular to the optic nerve at 3 mm behind the globe in both eyes in the traverse and sagittal planes, with the patient supine. The primary outcome was change in ONSD from pre-LP to post-LP. We calculated association of opening and closing LP pressures with changes in the pre- and post-LP ONSD measurements.ResultsThe mean patient age was 49.0 years (SD = 37–61, range 19–67) with 21 females (72.4%) and 26 (89.7%) white American (not Hispanic or Latino). The average opening pressure and closing pressures were 20.4 cm and 13.5 cm with a difference of 6.9 cm, (95% CI 3.9–10.0 cm). Pressures between the participants with baseline ONSD measurement > 5 mm (average opening pressure = 21.3 cm) to those < 5 mm (20.2 cm) differed by 1.1 cm (95% CI − 5.7 to 8.0). Linear regression revealed no association between the sagittal, transverse, average, and change in ONSD measurements with the observed LP opening pressure, change in LP pressure, or volume of cerebral spinal fluid (CSF) drained.ConclusionsIn this study of ambulatory patients undergoing rapid decreases in ICP via elective LP, we detected no acute changes in ultrasonographic measurement of the ONSD.

The Role of Transocular Ultrasound in the Assessment of Neurotoxicity-Related Encephalopathy in Mushroom Poisoning

ObjectiveMushroom poisonings can lead to life-threatening organ dysfunctions and neurotoxicity-related encephalopathy. This study aimed to detect increased intracranial pressure by measuring optic nerve sheath diameter (ONSD) ultrasonographically and to determine its association with clinical and laboratory parameters.MethodsIn this prospective case-control study, we evaluated the patients aged above 18 years who presented to the emergency department with mushroom poisoning. Vital signs, clinical and laboratory parameters and ONSD of both eyes measured with transocular ultrasound were noted at initial admission and the 24th hour.ResultsWe measured ONSD in 26 cases with mushroom poisoning and 26 healthy volunteers. Baseline ONSD measurements of the poisoning group were significantly higher than those of the control group (5.94±0.73 vs. 4.11±0.64, p<0.0001). ONSD values significantly regressed at 24th hour compared with the baseline measurements in the poisoning group (5.94±0.73 vs. 5.06±0.56, p<0.001).The ONSD values were significantly higher in patients who had a clinical picture of encephalopathy compared with patients who didn’t have (6.05±0.72 vs. 4.36±1.03, p<0.001). No significant deterioration was observed in ammonium levels, hepatic and renal functions of the patients.ConclusionWe detected increased ONSDs in patients with mushroom poisoning compared with those in the control healthy volunteers. Our findings suggest that ONSD, measured by ultrasonography, may be safely and effectively used to diagnose transient encephalopathy associated with neurotoxicity.

Evaluation of the effect of Boyle-Davis mouth gag on intracranial pressure in patients undergoing adenotonsillectomy by using ultrasonographic optic nerve sheath diameter measurement

ObjectiveWe aimed to evaluate the effect of an increase in intracranial pressure (ICP) due to sympatho-adrenergic response caused by mouth gag and tongue depressor during adenotonsillectomy by measuring the optic nerve sheath diameter (ONSD) by ultrasonographic method. MethodsForty patients (age range 3–12 years) who underwent adenotonsillectomy were included in the study. All patients underwent surgery under general anesthesia with endotracheal intubation. Boyle-Davis mouth gag was used during the procedure. ONSD measurement was performed and a high-frequency linear probe. All ONSD measurements were performed by a single investigator experienced in the use of ultrasound. Ultrasonographically measured ONSD before induction was accepted as baseline (T0) value. Immediately after insertion of the mouth gag (T1), just before removal of the mouth gag (T2), and just before extubation (T3), ultrasonographic measurements of ONSD were recorded. ResultsWhen patients' baseline ONSD values were compared with the values obtained in T1, T2, T3, and a statistically significant increase was detected. The ONSD value measured before removing the mouth gag (T2) was significantly higher than the ONSD value measured immediately after the insertion of the mouth gag (T1). The ONSD value measured just before extubation (T3) and after removal of the mouth gag was significantly lower than the ONSD value (T2) measured just before removal of the mouth gag. When heart rate, mean arterial pressure (MAP), peripheral oxygen saturation (SpO2) values of T0, T1, T2, T3 were compared, any statistically significant difference was not observed. When end-tidal carbon dioxide level (etCO2) and peak inspiratory pressure (PIP) values of T1, T2, T3 were compared, any statistically significant difference was not observed. ConclusionThis study showed that the Boyle-Davis mouth gag used during the adenotonsillectomy operation resulted in a significant increase in the diameter of the optic nerve sheath measured ultrasonographically and increased the ONSD even further during the time the mouth gag was remained in situ. In children with intracranial pathologies who will undergo adenotonsillectomy or those with increased ICP-related risk factors, the risks that may arise from the effect of the Boyle-Davis mouth gag on ICP should be considered.

Effects of low- and high-pressure carbon dioxide pneumoperitoneum on intracranial pressure during laparoscopic cholecystectomy.

Laparoscopic surgeries are a risk factor for raised intracranial **pressure and neurological complications. Even though rare, the consequences may be severe. One hundred and one patients of laparoscopic cholecystectomy were enrolled and were randomized into two groups: low-pressure 8mm Hg (Group A) and high-pressure 14mm Hg (Group B) carbon dioxide pneumoperitoneum during surgery. Fifty patients were in group A and 51 patients were in group B. Intracranial pressure was measured by measuring the optic nerve sheath diameter (ONSD) using ultrasound examination. Baseline ONSD was recorded followed by ONSD recording at various intervals: at the induction of anesthesia; 30min, 45min, at the end of surgery; and 30min post surgery. The groups were comparable in terms of demographics and comorbidities. The mean age of group A was 45years and for group B it was 45.75years. Most common indication for surgery was symptomatic gall stone disease. Baseline ONSD in group A was 0.427 ± 0.0459mm, whereas it was 0.412 ± 0.0412mm in group B. There was a significant rise of ONSD (p < 0.05) 30min after induction of pneumoperitoneum and up to 30min post anesthesia. In the low-pressure group 7 (14%) patients had a significant rise of ICP, whereas in the high-pressure group 20 (39%) patients had a significant rise of ICP (p < 0.05). High-pressure pneumoperitoneum causes significant rise in intracranial pressure in comparison to low-pressure pneumoperitoneum during laparoscopic cholecystectomy, which can be monitored by ONSD measurement by ultrasound examination and is totally non-invasive.

Effect of History of Mild Traumatic Brain Injury on Optic Nerve Sheath Diameter Changes after Valsalva Maneuver.

Optic nerve sheath diameter (ONSD) measured by transocular ultrasound is a marker of real-time intracranial pressure (ICP). The objective of this study was to evaluate the association between optic nerve sheath (ONS) dilation after a Valsalva maneuver and a prior history of mild to moderate traumatic brain injury (mTBI) in a heterogeneous sample of participants. Participants were excluded if they had had a recent brain injury, were symptomatic from a prior brain injury, had a history consistent with severe TBI and/or had undergone intracranial surgery. Ninety-five participants with and without a history of mTBI were included in the study. Transocular ultrasound of the ONS was performed before and after a Valsalva maneuver. Differences in the ONSD before and after a Valsalva maneuver were analyzed and correlated to the participants' history of mTBI. Baseline ONSD measurements between groups were not statistically significant. Following Valsalva, participants with a history of mTBI had a statistically significant increase in the ONSD compared with participants with no history of mTBI. This significant difference persisted after controlling for age, race, and sex. This study demonstrated an association between a prior history of mTBI and dilation of the ONS after Valsalva maneuver in a sample of asymptomatic participants, which was not seen in participants without a history of mTBI.

Cervical Interlaminar Epidural Injections at High Doses Do Not Increase Optic Nerve Sheath Diameter on a Long-Term Basis

Background: Cervical epidural injection (CEI) is widely performed on patients with pain originating from the cervical spine. Studies have shown a good relationship between the optic nerve sheath diameter (ONSD) and the intracranial pressure (ICP). Objective: The aim of this study was to evaluate the changes in the ONSD as a non-invasive surrogate marker of ICP after CEI. Study Design: Prospective observational study. Setting: Hospital and ambulatory pain clinic. Methods: Twenty patients undergoing CEI at the C5-6 level were enrolled in this observational study. The CEIs were performed using a total of 14 mL of mixture volume via the interlaminar approach in the right lateral decubitus position. The ONSD through ultrasonography was measured in the initial supine position (T0, baseline), 30 seconds after the completion of CEI (T0.5), at 30-second intervals for 5 minutes (T0.5~T5), and at one-minute intervals for 5 minutes (T6~T10). Results: The values of the baseline ONSD (T0) in both eyes were 4.1 ± 0.4 mm. The ONSD significantly increased from T1 to T10 (P &lt; 0.05) compared with T0. The maximum value of the ONSD was measured as 5.1 ± 0.4 mm at T4, and the mean difference between the baseline ONSD and its maximum value was 1.0 mm, which represented about 27%. There was no increase in ICPrelated complications such as dizziness, headache, visual acuity, or retinal hemorrhage. Limitations: This was an observational study without a control group. All patients were presumed to have no intracranial pathology. Conclusion: The 14 mL CEI resulted in an increase in the ONSD by ultrasonography over time. The most critical increase in ONSD was observed 4 minutes after CEI, but this increase was not sustained. Further work is needed to confirm the effects of the speed and volume of the injection and of the position. Registration: Registered in the Clinical Research Information Service of the Korea National Institute of Health (https://cris.nih.go.kr/cris/index.jsp), registration number: KCT0001487 Key words: Analgesic techniques, epidural block, intracranial pressure, optic nerve sheath diameter, ultrasonography

The correlation between optic nerve sheath diameter and volume status in patients after cardiac surgery

Objective: To investigate the relationship between optic nerve sheath diameter (ONSD) and volume status of patients after cardiac surgery. Methods: A total of consecutive 56 patients who were treated in Critical Care Unit in Peking Union Medical College Hospital after open heart surgery from January to August 2015 were screened in this study. Central venous pressure (CVP) and 72 h net fluid balance were monitored. ONSD and diameter of inferior vena cava (IVC) were measured by ultrasound. Results: A total of 44 patients were finally included in the study. The postoperative baseline ONSD was (5.31±1.96)mm, compared to (5.07±1.77)mm after 72 h treatment, with ΔONSD(0.22±0.21)mm. Baseline and post-treatment at 72 h CVP were (11.98±4.09)mmHg and (8.95±4.02)mmHg respectively. IVC dropped from (19.75±4.12)mm to (17.11±4.68)mm. ΔONSD and ΔCVP were significantly correlated (r=0.422, P<0.05), ΔONSD and net fluid balance (NFB) at 72 h were significantly correlated (r=-0.388, P<0.05). While ΔONSD were significantly correlated with ΔIVC (r=0.423, P<0.05), ΔCVP and ΔIVC were also significantly correlated (r=0.391, P<0.05). Conclusion: The change of ONSD in patients after cardiac surgery is related to the change of volume status. Therefore ONSD is helpful to estimate brain edema, not only could be a potential index to evaluate volume status, but also be used to guide improving prognosis after cardiac surgery.

Dependence of the optic nerve sheath diameter on acutely applied subarachnoidal pressure - an experimental ultrasound study

To determine the distensibility and elastic characteristics of the optic nerve sheath for development of a basic understanding of ultrasound studies aimed to measure optic nerve sheath diameter (ONSD) for detection of acutely elevated intracranial pressure (ICP). Isolated human optic nerves preparations obtained from autopsies were submitted to predefined pressure alterations, and consecutive changes in ONSD were measured by B-scan ultrasound under defined conditions. Following submission to pressure, the diameter of the nerve sheath increased up to 140% of its baseline value. The increase (mean 1.97 mm, SD 0.52 mm) corresponded to the magnitude of pressure steps measured in the perineural subarachnoidal space (SAS). Similarly, the ONSD declined in each of the preparations within a few minutes after the optic nerve was decompressed. However, it did not reach its baseline value again when pressure loads of 45-55 mmHg or more had been applied. The elasticity of the anterior sheath of the optic nerve is sufficient for the detection of pressure changes in the SAS especially for upward pressure steps. This is basically important for the application of clinical monitoring of the sheath diameter to facilitate the identification of patients with elevated ICP non-invasively (screening). However, further implementation of this procedure in neurointensive care and emergency medicine has to consider that the sheath diameter reversibility may be impaired after episodes of prolonged intracranial hypertension and a model for hysteresis is proposed.