[Evaluation of a Combination of Waveform Amplitude Latency and Decrease of Waveform Amplitude Magnitude during Spinal Surgery in Intraoperative Neurophysiological Monitoring of Transcranial Motor Evoked Potentials and Its Incidence on Postoperative Neurological Deficit]. / Vplyv predlzenia latencie transkraniálnych motorických evokovaných potenciálov v korelácií so znízením amplitúdy pocas spinálnych operácií s pouzitím intraoperacného neurofyziologického monitoringu na prognózu pooperacného neurologického deficitu.

PURPOSE OF THE STUDY This retrospective study investigated the significance of a combination of peak latency of waveform amplitude and waveform amplitude in association with spinal deformities. The correlation with postoperative neurologic deficit was evaluated too. MATERIAL AND METHODS Between January 2007 and January 2018, a group of 113 patients was evaluated in the study who underwent spine surgery using intraoperative neurophysiological monitoring (IONM) focusing on transcranial motor evoked potential (tc-MEP) monitoring. The average age of the patients was 30 years. Tc-MEPs were recorded bilaterally from tibialis anterior muscle and the abductor hallucis muscle in 88 patients without neurological deficit and in 25 patients with neurological deficit. The peak latency of waveform amplitude was defined as the period from stimulation until the waveform amplitude reached its peak. The correlation with postoperative neurological deficit was examined separately for latency delays of 5% and 10% or more and in combination with a decrease in amplitude of 70% or more. We used the presence-absence paradigm to evaluate the disappearance of previously present tc-MEPs and amplitude latency delays. The correlation with the deterioration of amplitudes from baseline or the elevation of thresholds was not used. Statistical tests were used to investigate the changes. The cases in our study with significant tc-MEP alerts were reviewed against the evidence-based response checklist. RESULTS Of 113 patients, the decrease in amplitude of 70% or more was identified in the neurological deficit group in 64% vs. 36% in the normal neurological group (p < 0.001). The neurological deficit was observed in 7.96% of patients postoperatively. A decrease in intraoperative amplitude of 70% or more from previously present tc-MEP occurred in 40 cases, with 89% sensitivity, 64% specificity, 36% false positive rate (FPR), and 20% positive predictive value (PPV) for prediction of postoperative neurological deficit. The amplitude latency peak delay of 10% or more was observed in 41 cases from the group of patients with postoperative neurological deficit, with 100% sensitivity, 64% specificity, 36% FPR and 22% PPV. A combination of a decrease in amplitude of 70% or more from the previously present tc-MEP and a delay in amplitude latency peak of 10% or more resulted in 100% sensitivity, 49% specificity, 51% FPR and 10% PPV in the group of postoperative neurological deficit patients. DISCUSSION Intraoperative tc-MEP alarm points have previously focused mainly on waveform amplitude. In our series, a criterion of an amplitude decrease of 70% or more from previously present tc-MEP was set as the alarm point. No alarm criterion for delay of peak latency of waveform amplitude was set before. We set a latency peak delay of 5% or more and 10% or more of waveform amplitude compared with the previously present tc-MEP as alarm criteria. This is the first study exploring the issue. We demonstrated the efficacy of latency peak of waveform amplitude together with the decrease of waveform amplitude. Another study found similarities in the decrease of amplitude of 70 % or more from baseline and the delay in amplitude latency of 10% or more from baseline; with 86% sensitivity, 98% specificity, 2% FPR and 86% PPV (1). CONCLUSIONS In conclusion, we investigated the efficacy of a change of peak latency delay of waveform amplitude in tc-MEP monitoring. The utilizing of the peak latency delay of waveform amplitude value resulted in high sensitivity up to 100 % and allows reduction of the FPR and an increase of the PPV. Further studies should set the alarm criteria more precisely for the waveform amplitude latency peak delay to achieve more effective spinal cord tc-MEP monitoring. Our concept of findings supports the neurophysiological monitoring findings in other studies. Key words: monitoring, IONM, intraoperative neurophysiological monitoring, tc-MEP, motor evoked potential, transcranial, amplitude, latency, peak.

The influence of anesthesia on intraoperative neurophysiological monitoring during spinal surgeries.

BACKGROUND: Intraoperative neuromonitoring using tc-MEPs satisfactorily detects motor tract integrity changes during spinal surgery. However, tc-MEP is affected by anesthesia and other factors, in which the stimulation threshold increases because the waveform amplitude decreases over time with the accumulation and boluses of anesthetics. METHODS: We conducted a retrospective study of 139 patients. The average age was 30 years. Tc-MEPs were recorded bilaterally from the tibialis anterior muscle and the abductor hallucis muscle. Statistical tests were used to investigate the changes to evaluate anesthetic effects. RESULTS: There were no significant differences in tc-MEP amplitude change (%) between the groups of propofol (13 %), remifentanil (22 %) and sufentanil (26 %, p < 0.01). Significant differences were found between the groups of propofol, remifentanil, and sufentanil (20 %) and bolus sufentanil (‒30 %), and bolus ketamine (730 %, p < 0.008). Major differences were observed between bolus sufentanil (‒30 %) and bolus ketamine (730 %, p < 0.001). When comparing tc-MEPs with no amplitude, no significant difference was found between the groups of propofol (26 %), remifentanil (24 %), and sufentanil (28 %, p < 0.007). Substantial difference was found between the groups of propofol, remifentanil, and sufentanil (mean 26 %) and the group where ketamine boluses were administered. We didn't observe any loss of amplitude (0 %, p < 0.0002). CONCLUSION: IONM may be useless in patients where boluses of sufentanil are administered and also with Medical Research Council grades 3 and below. Consider applying IONM in patients with severe spinal deformity along with a higher age of over 50 and neurological deficit. Increasing stimulus intensity or facilitation techniques may be considered to improve the usefulness of tc-MEP. Our concept of findings supports the neurophysiological monitoring findings in other studies (Tab. 10, Ref. 45).

The use of antiplatelet medication in hospitalised elderly patients.

BACKGROUND: The use of antiplatelet agents is strongly recommended for the secondary prevention of ischemic events such as myocardial infarction, stroke/transient ischemic attack (TIA). OBJECTIVES: The aim of our study was to analyse the use of antiplatelet medication in patients after myocardial infarction, stroke/TIA, and patients with both conditions and to identify patient-related characteristics, which determine the use of such drugs in elderly patients. METHODS: Study sample (n=372) was derived from 2,157 patients admitted to long-term care departments of three municipal hospitals. The study included patients aged ≥65 years after myocardial infarction, stroke/TIA or both. RESULTS: Antiplatelet medications were prescribed in 54.8 % and 68.5 % of patients at hospital admission and discharge, respectively. Hospitalisation led to a significant increase in the use of antiplatelet medication in patients after myocardial infarction and in those with the combination of both events. However, in patients after only stroke/TIA, we did not find any significant difference comparing the use of antiplatelet medication at the time of hospital admission and discharge, respectively. CONCLUSION: Our study revealed that physicians are more aware of the benefits of antiplatelet medication in elderly patients after myocardial infarction or those after both myocardial infarction and stroke/TIA in comparison with patients after only stroke/TIA (Tab. 3, Ref. 32).

Accuracy and clinical usefulness of scoliosis measurement with magnetic spine mapping--Ortelius.

OBJECTIVES: Our objective was to assess the accuracy of radiation-free magnetic method of scoliosis curve measurement (Ortelius 800) and its usefulness in clinical practice, as well as to judge whether it can replace x-rays, which represent currently the golden standard for scoliosis measurement. BACKGROUND: Patients with adolescent idiopathic scoliosis have to undergo multiple full-length spinal x-rays. Repeated exposure to ionizing radiation leads to higher incidence of breast cancer, thyroid cancer, and leukemia. One of the radiation-free methods that are candidates for replacing the x-rays is the magnetic measurement of the spine with Ortelius 800. METHODS: Twenty-eight patients with adolescent idiopathic scoliosis were measured with Ortelius. Data from Ortelius were compared with standard spinal x-rays taken the same week. RESULTS: The average Cobb's angle measured by x-ray was 35.11 degrees. The average absolute difference between Ortelius and x-rays was 6.69 degrees. The difference was statistically significant (p=0.0443). An acceptable difference was measured in subgroup of curves that do not exceed 40 degrees (difference 5, p=0.8915). CONCLUSION: Ortelius is most accurate in curves in range of 15-30 degrees of Cobb's angle. In larger curves it is increasingly inaccurate. Most important for clinical practice is the Cobb's angle range over 40 degrees, where the conservative therapy is to be replaced with surgery. Ortelius is not accurate enough in this range and therefore cannot fully substitute full spinal x-rays. It can be used to reduce the number of x-rays in the follow-up of smaller curve angles (Tab. 4, Fig. 8, Ref. 10).

Suboptimal use of gastroprotective medication in elderly antiplatelet users.

BACKGROUND: Use of acetylsalicylic acid (ASA) or thienopyridines in monotherapy or combination of both drugs is associated with increased risk of gastrointestinal (GI) bleeding. The administration of drugs inhibiting gastric acid production represents an effective way to avoid GI disorders associated with antiplatelet therapy. OBJECTIVES: The aim of our study was to evaluate the use of gastroprotective medication in elderly antiplatelet users in relation to risk factors for GI bleeding. METHODS: Patients (n = 428) aged ≥ 65 years who were prescribed low dose ASA or clopidogrel in monotherapy or combination at hospital discharge were enrolled in the study. RESULTS: Only 39.7 % of patients with 2 or more risk factors for GI bleeding were prescribed gastroprotective medication at hospital discharge. The probability of elderly antiplatelet drug user for prescription of gastroprotective medication was improved with following risk factors: age ≥ 85 years (OR = 2.99); history of peptic ulcer disease/ GI bleeding (OR = 15.79); other GI disorders (OR = 15.48); concomitant therapy with drugs increasing the risk of GI bleeding - systemic corticosteroids (OR = 29.03) and NSAIDs (OR = 4.79). CONCLUSION: Results of our study indicate the necessity to increase the awareness of GI bleeding risk in long-term antiplatelet users among prescribing physicians.

Dissolution and spectrophotometric determination of astaxanthin in aqueous solutions.

The poor solubility of astaxanthin in water can cause problems during dissolution tests of dosage forms because they are usually performed in water-based media. The aim of this study was the development of a convenient dissolution medium and a method for a spectrophotometric determination of astaxanthin in an aqueous solution. Three surfactants in different concentrations were tested as solubility-improving substances: sodium lauryl sulfate (SLS), polysorbate 80 (PS 80) and macrogolglycerol hydroxystearate (Cremophor RH 40, CR 40). Optimal conditions were determined. The dissolution of astaxanthin from solid dosage form is performed into 1000 g of a solution of sodium lauryl sulfate with the concentration 1.0% (w/w) at 37 degrees C by paddle method, 100 rotations per minute, dissolution time 30 minutes. The procedure is convenient for solid dosage forms with a content of 4 to 12 mg of astaxanthin. The spectrophotometric determination of astaxanthin in aqueous solution from the dissolution test is measured at 486 nm. The specific absorbance A(1%) 1cm for astaxanthin in water is 2000, a sodium lauryl sulfate solution (1%) was used as a blank.

Selectivity tuning in chiral dual column gas chromatography.

The enantioselective tuning of two columns coupled in series is investigated in chiral high-resolution gas chromatography. Two columns with opposite enantioselectivities (Chirasil-L-Val and Chirasil-D-Val) are coupled in series via a T connector, and the relative retention of enantiomers chromatographed on the system is changed by varying the individual carrier gas flow rates in the coupled columns. The flow-rate ratio necessary for the required selectivity is calculated on the basis of the measured retention factors on the individual columns. The performance of this method for adjusting selectivity is studied by the separation of enantiomers of the N-TFA-O-methyl esters of six amino acids. It is demonstrated that the change of the coupling point carrier gas pressure, at the constant inlet and outlet pressures, may change the enantioselectivity of the given column series to such an extent that the enantiomer elution order may be reversed.