Susanna Lai

Uncoupling of the autonomic and cardiovascular systems in acute brain injury

We hypothesized that acute brain injury results in decreased heart rate (HR) variability and baroreflex sensitivity indicative of uncoupling of the autonomic and cardiovascular systems and that the degree of uncoupling should be proportional to the degree of neurological injury. We used HR and blood pressure (BP) power spectral analysis to measure neuroautonomic regulation of HR and BP and the transfer function magnitude (TF) between BP and HR as a measure of baroreflex modulation of HR. In 24 brain-injured patients [anoxic/ischemic injury ( n = 7), multiple trauma ( n = 6), head trauma ( n = 5), central nervous system infection ( n = 4), and intracranial hemorrhage ( n = 2)], neurological injury and survival was associated with low-frequency (0.01-0.15 Hz) HR and BP power and TF. Brain-dead patients showed decreased low-frequency HR power [0.51 ± 0.36 (SE) vs. 2.54 ± 0.14 beats/min2, P = 0.03] and TF [0.61 ± 0.16 (SE) vs. 1.29 ± 0.07 beats ⋅ min-1 ⋅ mmHg-1, P = 0.05] compared with non-brain-dead patients. We conclude that 1) severity of neurological injury and outcome are inversely associated with HR and BP variability and 2) there is direct evidence for cardiovascular and autonomic uncoupling in acute brain injury with complete uncoupling during brain death.We hypothesized that acute brain injury results in decreased heart rate (HR) variability and baroreflex sensitivity indicative of uncoupling of the autonomic and cardiovascular systems and that the degree of uncoupling should be proportional to the degree of neurological injury. We used HR and blood pressure (BP) power spectral analysis to measure neuroautonomic regulation of HR and BP and the transfer function magnitude (TF) between BP and HR as a measure of baroreflex modulation of HR. In 24 brain-injured patients [anoxic/ischemic injury (n = 7), multiple trauma (n = 6), head trauma (n = 5), central nervous system infection (n = 4), and intracranial hemorrhage (n = 2)], neurological injury and survival was associated with low-frequency (0.01-0.15 Hz) HR and BP power and TF. Brain-dead patients showed decreased low-frequency HR power [0. 51 +/- 0.36 (SE) vs. 2.54 +/- 0.14 beats/min2, P = 0.03] and TF [0. 61 +/- 0.16 (SE) vs. 1.29 +/- 0.07 beats . min-1 . mmHg-1, P = 0.05] compared with non-brain-dead patients. We conclude that 1) severity of neurological injury and outcome are inversely associated with HR and BP variability and 2) there is direct evidence for cardiovascular and autonomic uncoupling in acute brain injury with complete uncoupling during brain death.

Linear and nonlinear analysis of hemodynamic signals during sepsis and septic shock.

Objective Neuroautonomic modulation of heart rate (HR) and blood pressure were assessed in sepsis or septic shock. We hypothesized that these metrics would be diminished in pediatric patients with sepsis and septic shock, indicating uncoupling of the autonomic and cardiovascular systems. Design Prospective case series. Setting Pediatric intensive care unit in a tertiary care children’s hospital. Patients Thirty pediatric patients with sepsis or septic shock. Interventions None. Measures and Main Results Metrics used included power spectral analysis, a linear frequency domain measure, and detrended fluctuation analysis, a nonlinear technique that assesses the degree of long-range correlation in HR or blood pressure. We found decreased low-frequency (2.68 ± 0.24 vs. 3.37 ± 0.17 [sem] bpm2;p = .03) and high-frequency HR power (2.18 ± 0.14 vs. 2.79 ± 0.23 bpm2;p = .04) and increased detrended fluctuation analysis scaling exponent (1.22 ± 0.06 vs. 1.00 ± 0.07 bpm2;p = .02) in sepsis vs. shock patients, respectively. Compared with sepsis or shock, recovery was associated with increases in low-frequency (3.61 ± 0.15 vs. 3.05 ± 0.19 bpm2;p < .0001) and high-frequency HR power (3.11 ± 0.15 vs. 2.50 ± 0.22 bpm2;p < .0001). Conclusions We conclude that uncoupling of the autonomic and cardiovascular systems occurs over both short- and long-range time scales during sepsis, and the degree of uncoupling may help differentiate between sepsis, septic shock, and recovery states.

Physiologic data acquisition system and database for the study of disease dynamics in the intensive care unit.

ObjectiveTo describe a real-time, continuous physiologic data acquisition system for the study of disease dynamics in the intensive care unit. DesignDescriptive report. SettingA 16-bed pediatric intensive care unit in a tertiary care children’s hospital. PatientsA total of 170 critically ill or injured pediatric patients. InterventionsNone. Main Outcome MeasuresNone. ResultsWe describe a computerized data acquisition and analysis system for the study of critical illness and injury from the perspective of complex dynamic systems. Both parametric (1 Hz) and waveform (125–500 Hz) signals are recorded and analyzed. Waveform data include electrocardiogram, respiration, systemic arterial pressure (invasive and noninvasive), central venous pressure, pulmonary arterial pressure, left and right atrial pressures, intracranial pressure, body temperature, and oxygen saturation. Details of the system components are explained and examples are given from the resultant physiologic database of signal processing algorithms and signal analyses using linear and nonlinear metrics. ConclusionsWe have successfully developed a real-time, continuous physiologic data acquisition system that can capture, store, and archive data from pediatric intensive care unit patients for subsequent time series analysis of dynamic changes in physiologic state. The physiologic signal database generated from this system is available for analysis of dynamic changes caused by critical illness and injury.

Bone Marrow Aspiration and Biopsy

Bone marrow aspiration is performed to assess cellular morphology and to conduct tests on the bone marrow. Bone marrow biopsy is often performed in tandem to provide information about the marrow and the extent of disease. This video demonstrates both procedures.

Umbilical Vascular Catheterization

Placement of umbilical catheters is an important skill for the treatment of critically ill neonates. Catheters can provide vascular access for resuscitation, monitoring, fluid administration, blood...

Linear and nonlinear analysis of heart rate variability during propofol anesthesia for short-duration procedures in children.

Objective To determine whether heart rate variability metrics provide an accurate method of monitoring depth of anesthesia, assessing the response to painful stimuli, and assessing neuroautonomic regulation of cardiac activity in children receiving propofol anesthesia for short-duration procedures. Design Prospective, case series. Setting Sixteen-bed pediatric intensive care unit, oncology unit, and endoscopy suite in a tertiary care children’s hospital and ophthalmology examination rooms in an associated eye institute. Patients Thirty-three pediatric patients undergoing propofol anesthesia for short procedures. Interventions None. Measurements and Main Results Heart rate variability metrics studied included mean, sd, low- and high-frequency power, detrended fluctuation analysis (represented by correlation coefficient, &agr;), and approximate entropy. Compared with the initial anesthetized state, we found increased heart rate sd (3.17 ± 1.31 vs. 7.05 ± 0.26 bpm, p < .0001), heart rate low-frequency power (3.69 ± 0.36 vs. 4.48 ± 0.41 bpm2/Hz, p < .0001), heart rate low-/high-frequency ratio (1.47 ± 0.26 vs. 1.26 ± 0.24, p = .001), and heart rate &agr; (1.12 ± 0.24 vs. 1.35 ± 0.21, p < .0001) during painful procedure. Mean heart rate (105.8 ± 13.4 vs. 101.5 ± 12.4 bpm, p = .005) and heart rate approximate entropy decreased with painful procedure (0.75 ± 0.19 vs. 0.53 + 0.16, p < .001), whereas there was no significant change in heart rate high-frequency power (3.04 ± 0.63 vs. 3.16 ± 0.71 bpm2/Hz, p = .26). Conclusions We conclude that power spectral analysis of heart rate variability may be an accurate and clinically useful measure of depth of propofol anesthesia. We speculate that high-frequency heart rate power during propofol anesthesia correlates with depth of anesthesia, whereas low-frequency power allows for assessment of the patient’s sympathetic response to pain.

Interactive web sites for families and physicians of pediatric intensive care unit patients: A preliminary report

Objective: To describe our experience with a Web-based communications program for the patients, families, and referring physicians of patients admitted to our pediatric intensive care unit. Design: Prospective descriptive case series for a 32-month period from April 2000 through January 2003. Setting: Sixteen-bed multidisciplinary medical-surgical pediatric intensive care unit (PICU). Subjects: Seventy-three of 78 patients admitted to the PICU for ≥3 days and their families participated in the study, along with 26 referring physicians. Intervention: None. Measurements and Main Results: We found that 77% (474/619) of surveyed family members and friends thought that the Web page helped them share information, 13% (82/619) were unsure, and only <1% (4/619) thought it did not help them share information. When comparing respondents who thought the Web page helped them share information with those who did not or those who did not know, internet use was significantly associated with thinking that the Web page helped them share information (p = .0007). Seventy-three percent (19/26) of physicians thought that Web page-based communication was easier than present methods to convey patient information, and 62% (16/26) replied that the Web-based communication met their expectation. Fifty-four percent (14/26) of physicians thought they were more likely to refer patients to our PICU because of the Web-based communication; this was significantly associated with physician assessment that the Web-based communication was easier than the present methods of communicating with referring physicians (p = .003). Conclusions: We conclude that both families and referring physicians find Web-based communications during a childs PICU hospitalization to be very helpful. We suggest that the Web-based PICU communications be developed and studied for both medical and economic impact.

Precursors to rapid elevations in intracranial pressure

Intracranial pressure (ICP) monitoring and management have substantially improved the outcome of patients with traumatic brain injury (TBI). However, rapid elevations in ICP remain a significant problem as they may lead to secondary brain injury and worse outcome due to cerebral ischemia. Current therapy is targeted towards treating rapid ICP elevations after they occur. Ideally, anticipatory treatment to obviate any elevation in ICP could occur if reliable precursors to ICP elevation were determined. In this paper, we report evidence for a physiologic transition zone prior to rapid elevations in ICP. We found that in thirty-three episodes of ICP elevation recorded from eleven patients, there was a statistically consistent decrease in the cardiac component of the ICP signal and the coefficient of correlation between the ICP trend and the pulse amplitude. We conclude that specific ICP signal metrics may serve as precursors that characterize the transition zone prior to a rapid elevation and may enable prediction of these elevations up to thirty seconds ahead.

Significance of intracranial pressure pulse morphology in pediatric traumatc brain injury

We investigated the relationship between the intracranial pulse pressure (ICP/sub PP/) and the mean intracranial pressure (ICP/sub M/). In adult patients, several research groups have described a linear relationship between ICP/sub PP/ and ICP/sub M/ within the range of cerebral autoregulation. Current monitoring and therapy are mainly based on the mean ICP/sub M/, since it is believed that the ICP/sub M/ contains most of the information provided by the other pulse morphology metrics. In this paper we attempt to answer whether there is further information within the ICP morphology not explained by ICP/sub M/ that might be of prognostic significance. We screened ICP records of 42 patients admitted to the Pediatric Intensive Care Unit at Doernbecher Childrens Hospital for segments in which the ICP/sub M/ varied at least 5 mmHg during a 1-hour period. We found 54 segments in 9 different pediatric TBI patients (ages 0.2-17.8 years, mean=9.9 years). ICP/sub PP/ and ICP/sub M/ were calculated for each pulse using an automatic pressure detection algorithm. The coefficient of linear correlation r was > 0.70 in 43/54 segments (p < 0.001), which indicates that there exists a linear relationship between ICP/sub PP/ and ICP/sub M/. However, we found r > 0.90 only in 16/54 segments (p=NS) . This result and visual inspection of ICP/sub PP/ vs. ICP/sub M/ density plots suggest that ICP pulse pressure is not fully explained by the ICP M.

Reduction of Pulled Elbow

Pulled elbow, a common childhood injury, can be reduced by a simple intervention that can be performed in an outpatient setting with rapid results. This video is intended to instruct clinicians in treating this injury.