Warning criteria for MEP monitoring during carotid endarterectomy: a retrospective study of 571 patients.

Monitoring of transcranial electrical motor evoked potentials (tcMEP) during carotid endarterectomy (CEA) has been shown to effectively detect intraoperative cerebral ischemia. The unique purpose of this study was to evaluate changes of MEP amplitude (AMP), area under the curve (AUC) and signal morphology (MOR) as additional MEP warning criteria for clamping-associated ischemia during CEA. Therefore, the primary outcome was the number of MEP alerts (AMP, AUC and MOR) in the patients without postoperative motor deficit (false positives). We retrospectively reviewed data from 571 patients who received CEA under general anesthesia. Monitoring of somatosensory evoked potentials (SSEP) and tcMEP was performed in all cases (all-or-none MEP warning criteria). The percentages of false positives (primary parameter) of AMP, AUC and MOR were evaluated according to the postoperative motor outcome. In the cohort of 562 patients, we found significant SSEP/MEP changes in 56 patients (9.96%). In 44 cases (7.83%) a shunt was inserted. Nine patients (1.57%) were excluded due to MEP recording failure. False positives were registered for AMP, AUC and MOR changes in 121 (24.01%), 148 (29.36%) and 165 (32.74%) patients, respectively. In combination of AMP/AUC and AMP/AUC/MOR false positives were found in 9.52% and 9.33% of the patients. This study is the first to evaluate the correctness of the MEP warning criteria AMP, AUC and MOR with regard to false positive monitoring results in the context of CEA. All additional MEP warning criteria investigated produced an unacceptably high number of false positives and therefore may not be useful in carotid surgery for adequate detection of clamping-associated ischemia.

Use of NEedle Versus suRFACE Recording Electrodes for Detection of Intraoperative Motor Warnings: A Non-Inferiority Trial. The NERFACE Study Part II.

In the NERFACE study part I, the characteristics of muscle transcranial electrical stimulation motor evoked potentials (mTc-MEPs) recorded from the tibialis anterior (TA) muscles with surface and subcutaneous needle electrodes were compared. The aim of this study (NERFACE part II) was to investigate whether the use of surface electrodes was non-inferior to the use of subcutaneous needle electrodes in detecting mTc-MEP warnings during spinal cord monitoring. mTc-MEPs were simultaneously recorded from TA muscles with surface and subcutaneous needle electrodes. Monitoring outcomes (no warning, reversible warning, irreversible warning, complete loss of mTc-MEP amplitude) and neurological outcomes (no, transient, or permanent new motor deficits) were collected. The non-inferiority margin was 5%. In total, 210 (86.8%) out of 242 consecutive patients were included. There was a perfect agreement between both recording electrode types for the detection of mTc-MEP warnings. For both electrode types, the proportion of patients with a warning was 0.12 (25/210) (difference, 0.0% (one-sided 95% CI, 0.014)), indicating non-inferiority of the surface electrode. Moreover, reversible warnings for both electrode types were never followed by permanent new motor deficits, whereas among the 10 patients with irreversible warnings or complete loss of amplitude, more than half developed transient or permanent new motor deficits. In conclusion, the use of surface electrodes was non-inferior to the use of subcutaneous needle electrodes for the detection of mTc-MEP warnings recorded over the TA muscles.

Modified Early Obstetric Warning Criteria Predict Maternal Morbidity in the Immediate Postpartum Period: A Case-Control Study.

OBJECTIVE: To evaluate the application of Modified Early Obstetric Warning Criteria (MEOWC) in the immediate postpartum period and to generate a preliminary predictive model for postpartum maternal morbidity. DESIGN: Retrospective case-control study that was conducted from January 2017 to January 2020. A total of 2,762 births occurred during the study period. SETTING: Obstetrics unit of a general hospital located in the Nakhon Si Thammarat province of Thailand. PARTICIPANTS: Three hundred charts of complete health records for women in the first 24 hours postbirth were used in the study. Severe maternal morbidity indicators from the Centers for Disease Control and Prevention as well as corresponding International Classification of Diseases, 10th Revision-Clinical Modification codes during birth and postpartum hospitalizations were used to define maternal morbidity. Case and control individuals were matched in an approximate 1:2 fashion based on the year when the birth occurred. MEASUREMENTS: Outcomes measurement was carried out using three data record forms-personal data, obstetric history, and MEOWC. To estimate the risks, logistic regression was performed, and a receiver operating characteristic curve was derived to evaluate the model's performance. RESULTS: One hundred cases of maternal morbidity that occurred in the immediate postpartum period were identified and matched with 200 control cases. Women with MEOWC during the immediate postpartum were much more likely to experience subsequent postpartum maternal morbidity than were women without the criteria. MEOWC were a moderate predictor of postpartum maternal morbidity. CONCLUSION: MEOWC are associated with increased odds of postpartum maternal morbidity. However, these findings should be validated in a prospective cohort to develop a predictive model that is effective for use in immediate postpartum care.

Maternal early warning criteria predict postpartum severe maternal morbidity and mortality after delivery hospitalization discharge: a case-control study.

BACKGROUND: The predictors of postpartum severe maternal morbidity and mortality have not been well-described using patient-level data. OBJECTIVE: This study aimed to evaluate the application of maternal early warning criteria in the postpartum period and generate a preliminary predictive model for severe maternal morbidity and mortality occurring after delivery hospitalization discharge until 42 days postpartum. STUDY DESIGN: A retrospective case-control study was conducted from January 2013 to September 2020. Cases were identified from electronic medical records using the International Classification of Diseases, Tenth Revision codes for Centers for Disease Control and Prevention-defined severe maternal morbidity. Patients meeting the criteria for severe maternal morbidity and mortality from delivery hospitalization discharge until 42 days postpartum were matched for delivery hospital and year with the controls in an approximate 1:2 fashion. The objective was to identify the demographic and clinical risk factors during the antepartum through postpartum periods for postpartum severe maternal morbidity and mortality. Multivariable logistic regression was performed to estimate the risks, and a receiver operating characteristic curve was derived to evaluate the model. RESULTS: Ninety cases of postpartum severe maternal morbidity and mortality that occurred following delivery hospitalization discharge were identified. These were matched with 175 controls. Women with postpartum severe maternal morbidity and mortality had more postpartum assessments (mean: 1.7 vs 1.4, P=.005) and a higher frequency of maternal early warning criteria (58% [52/90] vs 2% [3/175]; P<.001) preceding the diagnosis of severe maternal morbidity and mortality than controls. Black women had higher odds of postpartum severe maternal morbidity and mortality than White women (odds ratio, 1.93; 95% confidence interval, 1.14-3.27). Women with maternal early warning criteria during postpartum assessments were more likely to experience subsequent postpartum severe maternal morbidity and mortality (odds ratio, 67.2; 95% confidence interval, 21.3-211.6) than women with no maternal early warning criteria. Although the point estimate was different in Black women (odds ratio, 161.8; 95% confidence interval, 8.9 to >999) than White women (odds ratio, 47.9; 95% confidence interval, 13.8-167.1), the effect modification between the maternal early warning criteria and race was not statistically significant (P=.93). In a multivariable model, race, body mass index, cesarean delivery, and maternal early warning criteria at postpartum assessments were associated with subsequent severe maternal morbidity and mortality, with an area under the curve of 0.905 (95% confidence interval, 0.864-0.946). CONCLUSION: Maternal early warning criteria are associated with increased odds of postpartum severe maternal morbidity and mortality. A straightforward model that includes race, body mass index, cesarean delivery, and presence of maternal early warning criteria appears to be a promising tool to identify those at risk for postpartum severe maternal morbidity and mortality following delivery hospitalization discharge. This is an important first step in improving the ability to recognize and respond to conditions preceding postpartum severe maternal morbidity. These findings should be validated in a prospective cohort.

Motor Evoked Potential Warning Criteria in Supratentorial Surgery: A Scoping Review.

During intraoperative monitoring of motor evoked potentials (MEP), heterogeneity across studies in terms of study populations, intraoperative settings, applied warning criteria, and outcome reporting exists. A scoping review of MEP warning criteria in supratentorial surgery was conducted in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). Sixty-eight studies fulfilled the eligibility criteria. The most commonly used alarm criteria were MEP signal loss, which was always a major warning sign, followed by amplitude reduction and threshold elevation. Irreversible MEP alterations were associated with a higher number of transient and persisting motor deficits compared with the reversible changes. In almost all studies, specificity and Negative Predictive Value (NPV) were high, while in most of them, sensitivity and Positive Predictive Value (PPV) were rather low or modest. Thus, the absence of an irreversible alteration may reassure the neurosurgeon that the patient will not suffer a motor deficit in the short-term and long-term follow-up. Further, MEPs perform well as surrogate markers, and reversible MEP deteriorations after successful intervention indicate motor function preservation postoperatively. However, in future studies, a consensus regarding the definitions of MEP alteration, critical duration of alterations, and outcome reporting should be determined.

Recommendations of the International Society of Intraoperative Neurophysiology for intraoperative somatosensory evoked potentials.

Intraoperative somatosensory evoked potentials (SEPs) provide dorsal somatosensory system functional and localizing information, and complement motor evoked potentials. Correct application and interpretation require in-depth knowledge of relevant anatomy, electrophysiology, and techniques. It is advisable to facilitate cortical SEPs with total intravenous propofol-opioid or similarly favorable anesthesia. Moreover, SEP optimization is recommended to enhance surgical feedback speed and accuracy by maximizing signal-to-noise ratio (SNR); it consists of selecting highest-SNR peripheral and cortical derivations while omitting low-SNR channels. Confounding factors causing non-surgical SEP reduction should be excluded before issuing a warning. It is advisable to facilitate their identification with peripheral SEP controls and cortical SEP systemic controls whenever possible. Warning criteria should adjust for baseline drift and reproducibility. The recommended adaptive warning criterion is visually obvious amplitude reduction from recent pre-change values and clearly exceeding trial-to-trial variability, particularly when abrupt and focal. Acquisition and interpretation should be done by qualified technical and professional level personnel. Indications for SEP monitoring include intracranial, posterior fossa, and spinal neurosurgery, as well as orthopedic spine, cerebrovascular, and descending aortic surgery. Indications for SEP mapping include sensorimotor cortex and dorsal column midline identification. Future advances could modify current recommendations.

Pyelonephritis in Pregnancy: Relationship of Fever and Maternal Morbidity.

Objective To evaluate the relationship between maternal fever at the time of hospital admission and subsequent maternal morbidity in pregnant patients with pyelonephritis. Study Design In this retrospective cohort study, inpatient records were reviewed for all obstetric patients discharged from a single tertiary care hospital between June 1, 2011, and May 30, 2017, with the diagnosis of pyelonephritis. Patients were stratified into two groups, those with and without fever at the time of admission. Descriptive statistics were utilized to evaluate the association of fever at the time of presentation with subsequent morbidity. Using admission vital signs, maternal early warning criteria (MEWC) were applied and odds ratios calculated to predict intensive care unit (ICU) admission. Results A total of 110 patients were admitted with pyelonephritis in pregnancy; 24 patients were febrile and 86 patients were afebrile on admission. There was no difference in rates of maternal ICU admission between both groups. Positive MEWC was predictive of ICU admission with an adjusted odds ratio of 16.54 (95% confidence interval: 1.29-212.5; p = 0.03). Conclusion Afebrile pregnant patients with pyelonephritis remain at risk of significant maternal morbidity. Application of the MEWC on admission identifies patients at higher risk of ICU admission.

Intraoperative neurophysiological monitoring of the bulbocavernosus reflex during surgery for conus spinal lipoma: what are the warning criteria?

OBJECTIVEDespite the surge in the intraoperative use of the bulbocavernosus reflex (BCR) during lumbosacral surgeries, there are as yet no widely accepted BCR warning criteria for use with intraoperative neurophysiological monitoring (IONM). The author's aim was to find clinically acceptable warning criteria for use in IONM of the BCR.METHODSRecords of IONM of the BCR in 164 operations in 163 patients (median age 5 months) with a conus spinal lipoma who underwent surgery between August 2002 and May 2016 were retrospectively analyzed. The outcomes of IONM of the BCR were grouped by the residual amplitude at the end of surgery: group 1, ≥ 50%; group 2, 25%-50% (including the lower bound, but not the upper); and group 3, < 25%. Cases in which the BCR was lost were separately assessed as a subgroup of group 3. The postoperative urinary complication rate was used to verify the warning criteria zones.RESULTSThe BCR could be monitored in 149 surgeries (90.9%). There were 118 surgeries (79.2%) in group 1, 18 (12.1%) in group 2, and 13 (8.7%) in group 3. Two surgeries (11.1%) in group 2 and 6 (46.2%) in group 3 resulted in urinary complications. In the group 3 subgroup (lost BCR), all 5 surgeries resulted in urinary complications. The cutoff value of the BCR amplitude reduction was placed between groups 1 and 2 (zone 1: cutoff 50%), groups 2 and 3 (zone 2: cutoff 25%), and group 3 and its subgroup (zone 3: cutoff zero, present or lost). In zone 1, the positive predictive value (PPV) was 25.8% and the negative predictive value (NPV) was 100%. In zone 2, the PPV was 53.8% and the NPV 98.5%. In zone 3, the PPV was 100% and the NPV 97.9%. The PPV was highest in zone 3. The NPV was highest in zone 1, but its PPV was low (25.8%).CONCLUSIONSThe "lost or remained" criterion of BCR amplitude (zone 3: cutoff zero) can be used as a predictor of postoperative urinary function. As a warning criterion, the cutoff value of the BCR amplitude reduction at 75% (zone 2) may be used. This preliminary clinical report on the warning criteria for the BCR may contribute to improving the safety of surgery for conus spinal lipoma.

The critical warning sign of real-time brainstem auditory evoked potentials during microvascular decompression for hemifacial spasm.

OBJECTIVE: The aim of this study was to define the critical warning sign of real-time brainstem auditory evoked potential (BAEP) for predicting hearing loss (HL) after microvascular decompression (MVD) for hemifacial spasm (HFS). METHODS: Nine hundred and thirty-two patients with HFS who underwent MVD with intraoperative monitoring (IOM) of BAEP were analyzed. We used a 43.9 Hz/s stimulation rate and 400 averaging trials to obtain BAEP. To evaluate HL, pure-tone audiometry and speech discrimination scoring were performed before and one week after surgery. We analyzed the incidence for postoperative HL according to BAEP changes and calculated the diagnostic accuracy of significant warning criteria. RESULTS: Only 11 (1.2%) patients experienced postoperative HL. The group showing permanent loss of wave V showed the largest percentage of postoperative HL (p < 0.001). No patient who experienced only latency prolongation (≥1 ms) had postoperative HL. Loss of wave V and latency prolongation (≥1 ms) with amplitude decrement (≥50%) were highly associated with postoperative HL. CONCLUSIONS: Loss of wave V and latency prolongation of 1 ms with amplitude decrement ≥50% were the critical warning signs of BAEP for predicting postoperative HL. SIGNIFICANCE: These findings elucidate the critical warning sign of real-time BAEP.

Implementing Obstetric Early Warning Systems.

Severe maternal morbidity and mortality are often preventable and obstetric early warning systems that alert care providers of potential impending critical illness may improve maternal safety. While literature on outcomes and test characteristics of maternal early warning systems is evolving, there is limited guidance on implementation. Given current interest in early warning systems and their potential role in care, the 2017 Society for Maternal-Fetal Medicine (SMFM) Annual Meeting dedicated a session to exploring early warning implementation across a wide range of hospital settings. This manuscript reports on key points from this session. While implementation experiences varied based on factors specific to individual sites, common themes relevant to all hospitals presenting were identified. Successful implementation of early warnings systems requires administrative and leadership support, dedication of resources, improved coordination between nurses, providers, and ancillary staff, optimization of information technology, effective education, evaluation of and change in hospital culture and practices, and support in provider decision-making. Evolving data on outcomes on early warning systems suggest that maternal risk may be reduced. To effectively reduce maternal, risk early warning systems that capture deterioration from a broad range of conditions may be required in addition to bundles tailored to specific conditions such as hemorrhage, thromboembolism, and hypertension.

Retrospective Waveform Analysis of Transcranial Motor Evoked Potentials (MEP) to Identify Early Predictors of Impending Motor Deficits in Spinal Surgeries.

PURPOSE: Although there are guidelines analyzing transcranial motor evoked potentials (MEP) waveform criteria, they vary widely and are not applied universally during intraoperative neurophysiologic monitoring (IONM). The objective is to generate hypotheses to identify early and reliable MEP waveform characteristics prior to complete loss of MEP to predict impending motor spinal cord injuries during spinal surgeries. The ultimate goal is to enhance real-time feedback to prevent injury or detect reversible spinal cord damage. METHODS: Fifteen true positive cases of persistent intraoperative MEP loss and new postoperative motor deficits were retrospectively identified from 2011 to 2013. Waveform characteristics of latency, amplitude, duration, phases, and area-under-the-curve (AUC) were measured, and an intraoperative spinal cord index (ISCI) was calculated for 5 traces prior to complete MEP loss. ISCI = [amplitude x duration x (phases+1) x AUC]/latency. RESULTS: Out of 22 muscles in 15 cases, latency increased in 2, duration decreased in 12, amplitude decreased in 13, AUC decreased in 13, and ISCI decreased in 14. In 11 out of 15 cases (73%), ISCI dropped > 40% in at least one muscle before MEP were completely lost. Thirteen cases had concurrent somatosensory evoked potentials (SSEP) changes, 9 out of 13 had > 50% decrease in SSEP: 2 out of 9 changed before MEP, 5 out of 9 simultaneously, and 2 out of 9 after. CONCLUSIONS: In these cases of motor injury, smaller and simpler MEP waveforms preceded complete loss of signal. An ISCI 40% drop could be tested as a warning threshold for impending motor compromise in future prospective studies and lead to eventual standardization to predict irreversible postoperative deficits.

Maternal early warning systems.

This article reviews evidence and recommendations for maternal early warning systems designed to reduce severe maternal morbidity and mortality. The clinical rationale for these systems is discussed as is research literature on early warning systems from other fields.