Intraoperative Mapping of the Sensory Root of the Trigeminal Nerve in Patients with Pontocerebellar Angle Pathology

OBJECTIVE

The aim of the present study was to determine the position of the 3 sensory branches of the trigeminal nerve in the preganglionic tract using intraoperative neurophysiological mapping.

METHODS

We included consecutive adult patients who underwent neurosurgical treatment of cerebellopontine angle lesions. The trigeminal nerve was antidromically stimulated at 3 sites along its circumference with different stimulus intensities at a distance of ≤1 cm from the brainstem. The sensory nerve action potentials (SNAPs) were recorded from each main trigeminal branch (V1 [ophthalmic branch], V2 [maxillary branch], and V3 [mandibular branch]).

RESULTS

We analyzed 13 patients. The stimulation points at which we obtained the greatest number of congruous and exclusive SNAPs (SNAPs only on the stimulated branch) was the stimulation point for V3 (20.7%). The stimulation intensity at which we obtained the highest number of congruent and exclusive SNAPs with the stimulated branch was 0.5 mA.

CONCLUSIONS

Using our recording conditions, trigeminal stimulation is a reliable technique for mapping the V3 and V1 branches using an intensity not exceeding 0.5. However, reliable identification of the fibers of V2 is more difficult. Stimulation of the trigeminal nerve can be a reliable technique to identify the V3 and V1 branches if rhizotomy of these branches is necessary.

Is the Patient State Index a reliable parameter as guide to anaesthesiology in cranial neurosurgery? A first intraoperative study and a literature review

BACKGROUND

Patient State Index (PSI) and Suppression Ratio (SR) are two indices calculated by quantitative analysis of EEG used to estimate the depth of anaesthesia but their validation in neurosurgery must be done. Our aim was to investigate the congruity PSI and SR with raw EEG monitoring in neurosurgery.

METHODS

We included 34 patients undergoing elective cranial neurosurgery. Each patient was monitored by a SedLine device (PSI and SR) and by raw EEG. To appraise the agreement between PSI, SR and EEG Suppr%, Bland-Altman analysis was used. We also correlated the PSI and SR recorded at different times during surgery to the degree of suppression of the raw EEG data by Spearman's rank correlation coefficient. For a comparison with previous data we made an international literature review according to PRISMA protocol.

RESULTS

At all recording times, we found that there is a strong agreement between PSI and raw EEG. We also found a significant correlation for both PSI and SR with the EEG suppression percentage (p < 0.05), but with a broad dispersion of the individual values within the confidence interval.

CONCLUSION

The Masimo SedLine processed EEG monitoring system can be used as a guide in the anaesthetic management of patients during elective cranial neurosurgery, but the anaesthesiologist must be aware that previous correlations between PSI and SR with the suppression percentage may not always be valid in all individual patients. The use of an extended visual raw EEG evaluated by an expert electroencephalographer might help to provide better guidance.

Feasibility of Intraoperative Visual Evoked Potential Monitoring by Cortical Strip Electrodes in Patients During Brain Surgery: A Preliminary Study

OBJECTIVE

The role of visual evoked potentials (VEPs) monitoring during neurosurgical procedure in patient remains unclear. The purpose of our study was to determine the feasibility of intraoperative VEP recording using a strip cortical electrode during surgical resection of intracranial lesions.

METHODS

In this prospective, monocentric, observational study, we enrolled consecutive patients undergoing neurosurgical procedure for intracranial lesions. After dural opening, a cortical strip was positioned on the lateral occipital surface. Flash VEPs were continuously recorded using both subdermal corkscrew electrodes and strip electrodes. An electroretinogram was also recorded to guarantee delivery of adequate flash stimuli to the retina.

RESULTS

We included 10 patients affected by different intracranial lesions. Flash VEPs were recorded using subdermal corkscrew electrodes in all patients except 1 in whom they were never identified during the recording. Flash VEPs were recorded using strip electrodes in all patients and showed a polyphasic morphology with a significantly larger amplitude compared with that of flash VEPs measured using subdermal corkscrew electrodes. No patient reported worsened postoperative vision and a >50% decrease in the VEPs amplitude was never registered.

CONCLUSIONS

We have reported for the first time in the literature that VEP monitoring during a neurosurgical procedure is feasible via a cortical strip located on the occipital surface. The technique demonstrated greater stability and a larger amplitude compared with recordings with scalp electrodes, facilitating identification of any changes. Studies with more patients are needed to assess the clinical reliability of the technique.

How the work of respiratory physiotherapists changes the tracheostomy management and decannulation in a NICU department: an Italian experience

Tracheotomy is a clinical procedure that is often necessary though not without complications, hence the need for appropriate and timely decannulation. The inclusion of trained respiratory physiotherapists (RPT) in the staff and the use of shared protocols could help the team to manage the patient with tracheotomy cannula. The objective of this study was to describe the difference in the rate of decannulation and clinical outcomes of tracheostomized patients admitted to a NeuroIntensive Care Unit (NICU) team after the inclusion of a group of physiotherapists specialized in respiratory physiotherapy and a new phoniatric protocol. It is a 6-year retrospective study, in which two periods of 3 years each were compared: in the first period (P1: September 2013-August 2016) physiotherapists were called to treat NICU patients on a consultative basis (2 hours/day for 5 days a week); in the second period (P2: September 2016-August 2019) two full-time respiratory physiotherapists were present on the ward (7 hours/day, 6/7 days/week). In P2 period, a decannulation protocol was used. Patients who had undergone a tracheotomy procedure and who were alive at the time of discharge were retrospectively evaluated. We described the number of decannulations, the length of stay in NICU and decannulation time; the diagnosis of decannulated patients and the number of deaths. 928 total patients were analysed: 468 in P1, 460 in P2. Total length of stay or number of deaths did not change significantly between the two periods, while the number of decannulated patients before the discharge was higher in P2 143 (64%), compared with P1 79 (36%) p<0.001. More patients with neurological pathologies involving possible swallowing disorders, such as cerebral haemorrhage, head trauma and stroke, have been successfully decannulated in P2 than in P1 (120 patients in P2 vs 54 in P1). A multidisciplinary approach, including respiratory physiotherapist, dedicated to tracheostomy management, decannulation and early mobilization in NICU is safe, feasible and seems to improve the number of severe patients decannulated, even if no change was observed in NICU length of stay or deaths. Further studies must confirm our results in other ICU settings.

Amplitude Instability of Somatosensory Evoked Potentials as an Indicator of Delayed Cerebral Ischemia in a Case of Subarachnoid Hemorrhage

We describe a 55-year-old male patient with a subarachnoid hemorrhage (SAH) as a result of left middle cerebral artery (MCA) aneurysm rupture, who underwent continuous electroencephalogram (EEG) and somatosensory evoked potential (cEEG-SEP) monitoring that showed an unusual SEP trend pattern. EEG was continuously recorded, and SEPs following stimulation of median nerves were recorded every 50 minutes, with the amplitude and latency of the cortical components automatically trended. An increase in intracranial pressure required a left decompressive craniectomy. cEEG-SEP monitoring was started on day 7, which showed a prolonged (24 hours) instability of SEPs in the left hemisphere. During this phase, left MCA vasospasm was demonstrated by transcranial Doppler (TCD), and computed tomography perfusion (CTP) showed a temporo-parieto-occipital ischemic penumbra. Following intravascular treatment, hypoperfusion and the amplitude of cortical SEPs improved. In our case, a prolonged phase of SEP amplitude instability during vasospasm in SAH correlated with a phase of ischemic penumbra, as demonstrated by CTP. In SAH, SEP instability during continuous monitoring is a pattern of alert that can allow treatments capable of avoiding irreversible neurological deterioration.

Continuous EEG-SEP monitoring in severe brain injury

AIMS

To monitor acute brain injury in the neurological intensive care unit (NICU), we used EEG and somatosensory evoked potentials (SEP) in combination to achieve more accuracy in detecting brain function deterioration.

METHODS

Sixty-eight patients (head trauma and intracranial hemorrhage; GCS<9) were monitored with continuous EEG-SEP and intracranial pressure monitoring (ICP).

RESULTS

Fifty-five patients were considered "stable" or improving, considering the GCS and CT scan: in this group, SEP didn't show significant changes. Thirteen patients showed neurological deteriorations and, in all patients, cortical SEP showed significant alterations (amplitude decrease>50% often till complete disappearance). SEP deterioration anticipated ICP increase in 30%, was contemporary in 38%, and followed ICP increase in 23%. Considering SEP and ICP in relation to clinical course, all patients but one with ICP less than 20 mmHg were stable, while the three patients with ICP greater than 40 mmHg all died. Among the 26 patients with ICP of 20-40 mmHg, 17 were stable, while nine showed clinical and neurophysiological deterioration. Thus, there is a range of ICP values (20-40 mmHg) were ICP is scarcely indicative of clinical deterioration, rather it is the SEP changes that identify brain function deterioration. Therefore, SEP have a twofold interest with respect to ICP: their changes can precede an ICP increase and they can constitute a complementary tool to interpret ICP trends. It has been very important to associate SEP and EEG: about 60% of our patients were deeply sedated and, because of their relative insensitivity to anesthetics, only SEP allowed us to monitor brain damage evolution when EEG was scarcely valuable.

CONCLUSIONS

We observed 3% of nonconvulsive status epilepticus compared to 18% of neurological deterioration. If the aim of neurophysiological monitoring is to "detect and protect", it may not be limited to detecting seizures, rather it should be able to identify brain deterioration, so we propose the combined monitoring of EEG with SEP.

Continuous EEG–SEP monitoring of severely brain injured patients in NICU: methods and feasibility

AIMS

To evaluate the feasibility of a continuous neurophysiologic monitoring (electroencephalography (EEG)-somatosensory evoked potentials (SEPs)) in the neuro-intensive care unit (NICU), taking into account both the technical and medical aspects that are specific of this environment.

METHODS

We used an extension of the recording software that is routinely used in our unit of clinical neurophysiology. It performs cycles of alternate EEG and SEP recordings. Raw traces and trends are simultaneously displayed. Patient head and stimulator box are placed behind the bed and linked to the ICU monitoring terminal through optic fibers. The NICU staff has been trained to note directly clinical events, main artefacts and therapeutic changes. The hospital local area network (LAN) enables remote monitoring survey.

RESULTS

Continuous EEG (CEEG)-SEP monitoring was performed in 44 patients. Problems of needle detachment were seldomly encountered, thanks to the use of a sterile plastic dressing, which covers needles. We never had infection or skin lesions due to needles or the electrical stimulator. The frequent administration of sedative at high doses prevented us from having a clinically valuable EEG in several cases but SEPs were always monitorable, independently of the level of EEG suppression. The diagnosis of seizures and non-epileptic status was based on raw EEG, while quantitative EEG (QEEG) was used to quantify ictal activity as a guide to treatment.

CONCLUSIONS

EEG and EP waveforms collected in NICU were of comparable quality to routine clinical measurements and contained the same clinical information. A continuous SEP monitoring in a comatose and sedated patient in NICU is not technically more difficult and potentially less useful than in operating room. This monitoring appears to be feasible provided the observance of some requirement regarding setting, electrodes, montages, personnel integration, consulting and software.

Haemodynamic and haemoximetric aspects of experimental orthotopic liver transplantation: comparison between two different doses of propofol

OBJECTIVE

Evaluation of haemodynamic and gas exchange modifications using propofolnitrous oxide anaesthesia after ketamine induction during experimental orthotopic liver transplantation (OLT).

DESIGN

Measurements of haemodynamic and haemoximetric effects of two anaesthesiological conditions, differing each other for the different dose of propofol, performed in an experimental model characterized by temporary anhepatism followed by revascularization.

SETTING

Surgical experimental laboratory of the University Hospital of Florence.

ANIMALS

Thirty experimental OLT on female pigs (weight 30 +/- 2 kg) were performed.

MEASUREMENTS AND MAIN RESULTS

The following haemodynamic: HR, MAP, MPAP, PCWP, CI, SI, RVSWI, LVSWI, SVR, PVR, RPP and gas-exchange parameters: PaCO2, etCO2, D(aA)CO2, PaO2/PAO2, VD/VTphys, HB, PaO2, SaO2, DO2, O2ER, VO2, SvO2, VO2/DO2 relationship were evaluated. Anaesthesia was induced by ketamine and maintained by N2O and propofol infusion using 0.28 mg x kg(-1)x min(-1) (Group 1) and 0.19mg x kg(-1) x min(-1) (Group 2). During the anhepatic phase we used cavalportal-jugular by-pass (CPJ). Haemodynamic preoperative data confirmed the absence of any myocardial depressant effect at the lower dose of propofol. During the most critical stages of surgery a progressive decrease of CI associated with low values of PCWP was observed. The decrease of etCO2 during the anhepatic phase is due to the VD/VT increase following CI reduction and CO2 production decrease. VO2 decreased significantly during the anhepatic phase and successively increased during the reperfusion phase whereas CI remained low, during both surgical phases. These results demonstrated that VO2 was largely independent from DO2 because cellular O2ER gradually increased as DO2 remained constantly low, thus indicating a good cellular metabolism reuptake. The decrease of SVO2 is related to the decrease of CI and to the increase of VO2 and O2ER.

CONCLUSION

The VO2/DO2 relationship showed a complete O2 supply-non-dependency suggesting an adequate cellular metabolism maintenance during the anhepatic and postanhepatic phases. According to these results, the authors suggest that propofol, within the two different anaesthesiological protocols at two different doses, surely favoured a good cellular perfusion also under low cardiac output conditions, undoubtedly contributing to the realization of stress-resistant conditions and influencing a good recovery and postoperative outcome.

Anaesthesia for urological endoscopic procedures in adult outpatients

The aim of this study was to establish whether propofol in combination with fentanyl or ketamine provides a good quality of anaesthesia and recovery time in urological endoscopic outpatient surgery. Sixty patients (ASA I-II) were assigned randomly to receive either 2.5 micrograms kg-1 fentanyl or 1 mg kg-1 ketamine. In both groups anaesthesia was induced with propofol 1.5 mg kg-1 and maintained with 7 mg kg-1 h-1. Patients breathed nitrous oxide and oxygen 3:2 spontaneously. Cardiovascular parameters were more stable after ketamine. The most important side effect was the presence of apnoea lasting longer than 60 s in 14 patients receiving fentanyl. The time to establish alertness was shorter in the ketamine group, who also had a better (P < 0.05) as well as post-anaesthetic recovery room score.