Quantitative Pupillometry: Clinical Applications for the Internist.

From the time of Galen, examination of the pupillary light reflex has been a standard of care across the continuum of health care. The growing body of evidence overwhelmingly supports the use of quantitative pupillometry over subjective examination with flashlight or penlight. At current time, pupillometers have become standard of care in many hospitals across 6 continents. This review paper provides an overview and rationale for pupillometer use and highlights literature supporting pupillometer-derived measures of the pupillary light reflex in both neurological and non-neurological patients across the health care continuum.

Objective Pupillometry as an Adjunct to Prediction and Assessment for Oculomotor Nerve Injury and Recovery: Potential for Practical Applications.

BACKGROUND: Pupillary light reflex examinations are intrinsic to any good neurological examination. Consistent evidence has shown that automated pupillometry assessments provide superior accuracy and interrater correlation compared with bedside eye examinations. Pupillary indexes such as the neurological pupil index (NPI) can also provide several hours of warning before the advent of herniation syndromes or third nerve palsy. METHODS: We determined the unique temporal relationship between NPI changes and third nerve palsy occurrence and recovery in an initially neurologically intact hospitalized patient. A 53-year-old woman presented with aneurysmal subarachnoid hemorrhage and headaches. Her aneurysm was treated surgically without complications. After lumbar drainage for hydrocephalus, she developed isolated left third nerve palsy that slowly recovered over the following weeks. Pupilometer data were obtained throughout her hospital stay. RESULTS: A total of 121 pupillary measurement sets were obtained. The NPI had decreased to an abnormal level (<3) 12 hours before she became symptomatic. The NPI also started improving 24 hours before improvement in her clinical examination. The patient did not display signs of neurological dysfunction related to vasospasm during her stay. CONCLUSION: The NPI seems to reliably correlate with third nerve function and appears to possess predictive temporal properties that could allow practitioners to anticipate neurological injury and recovery. These findings could affect the fields of neurosciences, trauma, military medicine, critical care, and ophthalmology.

Intrathoracic pressure regulation therapy applied to ventilated patients for treatment of compromised cerebral perfusion from brain injury.

BACKGROUND: Reducing intrathoracic pressure in the setting of compromised cerebral perfusion due to acute brain injury has been associated with reduced intracranial pressure and enhanced cerebral perfusion pressure and blood flow in animals. Noninvasive active intrathoracic pressure regulation lowers intrathoracic pressure, increases preload, reduces the volume of venous blood and cerebral spinal fluid in the skull, and enhances cerebral blood flow. We examined the feasibility of active intrathoracic pressure regulation therapy in patients with brain injury. We hypothesized that active intrathoracic pressure regulation therapy would be associated with lowered intracranial pressure and increased cerebral perfusion pressure in these patients. METHODS: At three institutions, active intrathoracic pressure regulation therapy (CirQlator™, ZOLL) was utilized for 2 consecutive hours in five mechanically ventilated patients with brain injury. A 30-minute interval was used to collect baseline data and determine persistence of effects after device use. End-tidal carbon dioxide was controlled by respiratory rate changes during device use. The intracranial pressure, mean arterial pressure, and cerebral perfusion pressure were recorded at 5-minute intervals throughout all three periods of the protocol. Results for each interval are reported as mean and standard deviation. RESULTS: Intracranial pressure was decreased in all five patients by an average of 21% during (15 ± 4 mmHg) compared to before active intrathoracic pressure regulation (19 ± 4) (p = 0.005). This effect on intracranial pressure (15 ± 6) was still present in four of the five patients 30 minutes after therapy was discontinued (p = 0.89). As a result, cerebral perfusion pressure was 16% higher during (81 ± 10) compared to before active intrathoracic pressure regulation (70 ± 14) (p = 0.04) and this effect remained present 30 minutes after therapy was discontinued. No adverse events were reported. CONCLUSIONS: These data support the notion that active intrathoracic pressure regulation, in this limited evaluation, can successfully augment cerebral perfusion by lowering intracranial pressure and increasing mean arterial pressure in patients with mild brain injury. The measured effects were immediate on administration of the therapy and persisted to some degree after the therapy was terminated.

Education Research: Variation in priorities for neurocritical care education expressed across role groups.

OBJECTIVE: To define expectations for neurocritical care (NCC) core competencies vs competencies considered within the domain of other subspecialists. METHODS: An electronic survey was disseminated nationally to NCC nurses, physicians, fellows, and neurology residents through Accreditation Council for Graduate Medical Education neurology residency program directors, United Council for Neurologic Subspecialties neurocritical care fellowship program directors, and members of the Neurocritical Care Society. RESULTS: A total of 268 neurocritical care providers and neurology residents from 30 institutions responded. Overall, >90% supported NCC graduates independently interpreting and managing systemic and cerebral hemodynamic data, or performing brain death determination, neurovascular ultrasound, vascular access, and airway management. Over 75% endorsed that NCC graduates should independently interpret EEG and perform bronchoscopies. Fewer but substantial respondents supported graduates being independent performing intracranial bolt (45.8%), ventriculostomy (39.0%), tracheostomy (39.8%), or gastrostomy (19.1%) procedures. Trainees differed from physicians and program directors, respectively, by advocating independence in EEG interpretation (92.8%, 61.8%, and 65.3%) and PEG placement (29.3%, 9.1%, and 8.5%). CONCLUSIONS: Broad support exists across NCC role groups for wide-ranging NCC competencies including skills often performed by other neurology and non-neurology subspecialties. Variations highlight natural divergences in expectations among trainee, physician, and nurse role groups. These results establish expectations for core competencies within NCC and initiate dialogue across subspecialties about best practice standards for the spectrum of critically ill patients requiring neurologic care.

Understanding the Relationship Between the Neurologic Pupil Index and Constriction Velocity Values.

The pupillary light reflex (PLR) describes the response when light hits the retina and sends a signal (cranial nerve II) to the Edinger-Westphal Nucleus which via cranial nerve III results in pupillary constriction. The Neurological Pupil indexTM (NPi) and pupil constriction velocity (CV) are two distinct variables that can be observed and measured using a pupillometer. We examine NPi and CV in 27,462 pupil readings (1,617 subjects). NPi values <3.0 and a CV < 0.8 mm/sec were considered abnormal. Regression was used to clarify the effect of pupil size and repeated measures. An odds ratio of abnormal CV given normal NPi (and vice versa) was computed using the glimmixed (SAS) regression. Of 27,462 readings, 49.2% revealed bilaterally normal NPi wtih brisk CV, and 10.8% revealed bilaterally abnormal NPi and slow CV; 9.1% with unilaterally normal NPi and brisk CV where the opposite pupil had an abnormal NPi and slow CV. The remaining 30.9% revealed that one or both PLR had either a normal NPi with slow CV, or abnormal NPi with brisk CV. Brisk CV does not rule out an abnormal PLR; slow CV does not rule in abnormal PLR. Practitioners should consider these implications when interpreting pupillometry readings.

Correlation of Noninvasive Blood Pressure and Invasive Intra-arterial Blood Pressure in Patients Treated with Vasoactive Medications in a Neurocritical Care Unit.

BACKGROUND: The correlation between noninvasive (oscillometric) blood pressure (NBP) and intra-arterial blood pressure (IAP) in critically ill patients receiving vasoactive medications in a Neurocritical Care Unit has not been systematically studied. The purpose of this study is to examine the relationship between simultaneously measured NBP and IAP recordings in these patients. METHODS: Prospective observational study of patients (N = 70) admitted to a neurocritical care unit receiving continuous vasopressor or antihypertensive infusions. Paired NBP/IAP observations along with covariate and demographic data were abstracted via chart audit. Analysis was performed using SAS v9.4. RESULTS: A total of 2177 paired NBP/IAP observations from 70 subjects (49% male, 63% white, mean age 59 years) receiving vasopressors (n = 21) or antihypertensive agents (n = 49) were collected. Paired t test analysis showed significant differences between NBP versus IAP readings: ([systolic blood pressure (SBP): mean = 136 vs. 140 mmHg; p < 0.0001], [diastolic blood pressure (DBP): mean = 70 vs. 68 mmHg, p < 0.0001], [mean arterial blood pressure (MAP): mean = 86 vs. 90 mmHg, p < 0.0001]). Bland-Altman plots for MAP, SBP, and DBP demonstrate good inter-method agreement between paired measures (excluding outliers) and demonstrate NBP-IAP SBP differences at extremes of blood pressures. Pearson correlation coefficients show strong positive correlations for paired MAP (r = 0.82), SBP (r = 0.84), and DBP (r = 0.73) recordings. An absolute NBP-IAP SBP difference of > 20 mmHg was seen in ~ 20% of observations of nicardipine, ~ 25% of observations of norepinephrine, and ~ 35% of observations of phenylephrine. For MAP, the corresponding numbers were ~ 10, 15, and 25% for nicardipine, norepinephrine, and phenylephrine, respectively. CONCLUSION: Despite overall strong positive correlations between paired NBP and IAP readings of MAP and SBP, clinically relevant differences in blood pressure are frequent. When treating with vasoactive infusions targeted to a specific BP goal, it is important to keep in mind that NBP and IAP values are not interchangeable.

Increasing Adherence to Brain Trauma Foundation Guidelines for Hospital Care of Patients With Traumatic Brain Injury.

BACKGROUND: The Brain Trauma Foundation has developed treatment guidelines for the care of patients with acute traumatic brain injury. The Adam Williams Initiative is a program established to provide education and resources to encourage hospitals across the United States to incorporate the guidelines into practice. OBJECTIVE: To explore the relationship in hospitals between participation in the Adam Williams Initiative and adherence to the Brain Trauma Foundation guidelines for patients with acute traumatic brain injury. METHOD: Hospitals that participated in the Adam Williams Initiative entered data into an online tracking system of patients with traumatic brain injury for at least 2 years after the initial site training. Data included baseline hospital records and daily records on hospital care of patients with traumatic brain injury, including blood pressure, intracranial pressure, cerebral perfusion pressure, oxygenation, and other data relevant to the 15 key metrics in the Brain Trauma Foundation guidelines. RESULTS: The 16 hospitals funded by the Adam Williams Initiative had good overall adherence to the 15 key metrics of the recommendations detailed in the Brain Trauma Foundation guidelines. Variability in results was primarily due to data collection methods and analysis. CONCLUSIONS: The Adam Williams Initiative helps promote adherence to the Brain Trauma Foundation guidelines for hospital care of patients with traumatic brain injury by providing a platform for developing and standardizing best practices. Participation in the initiative is associated with high adherence to clinical guidelines, a situation that may subsequently improve care and outcomes for patients with traumatic brain injury.

The State of Neurocritical Care Fellowship Training and Attitudes toward Accreditation and Certification: A Survey of Neurocritical Care Fellowship Program Directors.

Neurocritical care as a recognized and distinct subspecialty of critical care has grown remarkably since its inception in the 1980s. As of 2016, there were 61 fellowship training programs accredited by the United Council for Neurologic Subspecialties (UCNS) in the United States and more than 1,000 UCNS-certified neurointensivists from diverse medical backgrounds. In late 2015, the Program Accreditation, Physician Certification, and Fellowship Training (PACT) Committee of the Neurocritical Care Society (NCS) was convened to promote and support excellence in the training and certification of neurointensivists. One of the first tasks of the committee was to survey neurocritical care fellowship training program directors to ascertain the current state of fellowship training and attitudes regarding transition to Accreditation Council for Graduate Medical Education (ACGME) accreditation of training programs and American Board of Medical Specialties (ABMS) certification of physicians. First, the survey revealed significant heterogeneities in the manner of neurocritical care training and a lack of consistency in requirements for fellow procedural competency. Second, although a majority of the 33 respondents indicated that a move toward ACGME accreditation/ABMS certification would facilitate further growth and mainstreaming of training in neurocritical care, many programs do not currently meet administrative requirements and do not receive the level of institutional support that would be needed for such a transition. In summary, the results revealed that there is an opportunity for future harmonization of training standards and that a transition to ACGME accreditation/ABMS certification is preferred. While the results reflect the opinions of more than half of the survey respondents, they represent only a small sample of neurointensivists.

Complication Rates of 3% Hypertonic Saline Infusion Through Peripheral Intravenous Access.

INTRODUCTION: Hyperosmolar therapy with hypertonic saline (HTS) is a cornerstone in the management of intracranial hypertension and hyponatremia in the neurological intensive care unit. Theoretical safety concerns remain for infiltration, thrombophlebitis, tissue ischemia, and venous thrombosis associated with continuous 3% HTS administered via peripheral intravenous (pIV) catheters. It is common practice at many institutions to allow only central venous catheter infusion of 3% HTS. METHODS: Hospital policy was changed to allow the administration of 3% HTS via 16- to 20-gauge pIVs to a maximum infusion rate of 50 mL/h in patients without central venous access. We prospectively monitored patients who received peripheral 3% HTS as part of a quality improvement project. We documented gauge, location, maximum infusion rate, and total hours of administration. Patients were assessed for infiltration, erythema, swelling, phlebitis, thrombosis, and line infection. RESULTS: There were 28 subjects across 34 peripheral lines monitored. Overall, subjects received 3% HTS for a duration between 1 and 124 hours with infusion rates of 30 to 50 mL/h. The rate of complications observed was 10.7% among all subjects. Documented complications included infiltration (n = 2), with an incidence of 6%, and thrombophlebitis (n = 1), with an incidence of 3%. CONCLUSIONS: There has been a long concern among healthcare providers, including nursing staff, in regard to pIV administration of prolonged 3% HTS infusion therapy. Our study indicates that peripheral administration of 3% HTS carries a low risk of minor, nonlimb, or life-threatening complications. Although central venous infusion may reduce the risk of these minor complications, it may increase the risk of more serious complications such as large vessel thrombosis, bloodstream infection, pneumothorax, and arterial injury. The concern regarding the risks of pIV administration of 3% HTS may be overstated and unfounded.

Association Patterns of Simultaneous Intraventricular and Intraparenchymal Intracranial Pressure Measurements.

BACKGROUND: The process of measuring intracranial pressure (ICP) can be accomplished using a variety of monitors placed primarily either in the ventricles or brain parenchyma. OBJECTIVE: There is inadequate data to support the conclusion that ICP measured simultaneously from 2 different sites using 2 different devices produces similar findings in the same subject. The purpose of this study was to identify the correlation between simultaneous measurements from both an external ventricular drain (EVD) and an intraparenchymal monitor (IPM). METHODS: In this retrospective observational study, manual chart abstraction was used to obtain time-indexed ICP values during a period of 2 years from patients diagnosed with severe traumatic brain injury who had received simultaneous EVD and IPM placement. RESULTS: When all time points were compared, the correlation between EVD and IPM was strong (r = 0.6955). However, when limiting the ICP values to be <20 or <25 in either the EVD or the IPM, the correlation was noted to be weaker (r = 0.3576 and r = 0.4232, respectively). CONCLUSION: There is inadequate evidence to support that intraparenchymal ICP values can be treated in a similar manner to ICP values obtained from an EVD. ABBREVIATIONS: CSF, cerebrospinal fluidEVD, external ventricular drainICP, intracranial pressureIPM, intraparenchymal monitorTBI, traumatic brain injury.