Comparing the compensatory reserve metric obtained from invasive arterial measurements and photoplethysmographic volume-clamp during simulated hemorrhage.

PURPOSE: The compensatory reserve metric (CRM) is a novel tool to predict cardiovascular decompensation during hemorrhage. The CRM is traditionally computed using waveforms obtained from photoplethysmographic volume-clamp (PPGVC), yet invasive arterial pressures may be uniquely available. We aimed to examine the level of agreement of CRM values computed from invasive arterial-derived waveforms and values computed from PPGVC-derived waveforms. METHODS: Sixty-nine participants underwent graded lower body negative pressure to simulate hemorrhage. Waveform measurements from a brachial arterial catheter and PPGVC finger-cuff were collected. A PPGVC brachial waveform was reconstructed from the PPGVC finger waveform. Thereafter, CRM values were computed using a deep one-dimensional convolutional neural network for each of the following source waveforms; (1) invasive arterial, (2) PPGVC brachial, and (3) PPGVC finger. Bland-Altman analyses were used to determine the level of agreement between invasive arterial CRM values and PPGVC CRM values, with results presented as the Mean Bias [95% Limits of Agreement]. RESULTS: The mean bias between invasive arterial- and PPGVC brachial CRM values at rest, an applied pressure of -45mmHg, and at tolerance was 6% [-17%, 29%], 1% [-28%, 30%], and 0% [-25%, 25%], respectively. Additionally, the mean bias between invasive arterial- and PPGVC finger CRM values at rest, applied pressure of -45mmHg, and tolerance was 2% [-22%, 26%], 8% [-19%, 35%], and 5% [-15%, 25%], respectively. CONCLUSION: There is generally good agreement between CRM values obtained from invasive arterial waveforms and values obtained from PPGVC waveforms. Invasive arterial waveforms may serve as an alternative for computation of the CRM.

Physiologic validation of the compensatory reserve metric obtained from pulse oximetry: A step towards advanced medical monitoring on the battlefield.

BACKGROUND: The Compensatory Reserve Metric (CRM) provides a time sensitive indicator of hemodynamic decompensation. However, its in-field utility is limited due to the size and cost-intensive nature of standard vital sign monitors or photoplethysmographic volume-clamp (PPGVC) devices used to measure arterial waveforms. In this regard, photoplethysmographic measurements obtained from pulse oximetry (PPGPO) may serve as a useful, portable alternative. This study aimed to validate CRM values obtained using PPGPO. METHODS: Forty-nine healthy adults (25 females) underwent a graded lower body negative pressure (LBNP) protocol to simulate hemorrhage. Arterial waveforms were sampled using PPGPO and PPGVC. The CRM was calculated using a one-dimensional convolutional neural network. Cardiac output and stroke volume were measured using PPGVC. A brachial artery catheter was used to measure intraarterial pressure. A 3-lead ECG was used to measure heart rate. Fixed-effect linear mixed models with repeated measures were used to examine the association between CRM values and physiologic variables. Log-rank analyses were used to examine differences in shock determination during LBNP between monitored hemodynamic parameters. RESULTS: The median LBNP stage reached was 70 mmHg (Range: 45-100 mmHg). Relative to baseline, at tolerance there was a 47±12% reduction in stroke volume, 64±27% increase in heart rate, and 21±7% reduction in systolic blood pressure (P<0.001 for all). CRM values obtained with both PPGPO and PPGVC were associated with changes in heart rate (P<0.001), stroke volume (P<0.001), and pulse pressure (P<0.001). Furthermore, they provided an earlier detection of hemodynamic shock relative to the traditional metrics of shock index (P<0.001 for both), systolic blood pressure (P<0.001 for both), and heart rate (P=0.001 for both). CONCLUSION: The CRM obtained from PPGPO provides a valid, time-sensitized prediction of hemodynamic decompensation, opening the door to provide military medical personnel noninvasive in-field advanced capability for early detection of hemorrhage and imminent onset of shock. LEVEL OF EVIDENCE: Diagnostic Tests or Criteria, Level IV.

Improvements in the Endoscopic Transsphenoidal Resection of Craniopharyngiomas: A Global Learning Curve.

BACKGROUND: Surgical management of craniopharyngiomas is nuanced and has varied in terms of the selected approach and aggressiveness of resection over time. In the past several decades, the endoscopic transsphenoidal approach has become commonly used for craniopharyngioma resection. There is a well characterized institutional 'learning curve' regarding endoscopic transsphenoidal approaches for craniopharyngiomas at specialized centers; however, the broader global learning curve remains to be characterized. METHODS: Clinical outcome data following endoscopic transsphenoidal craniopharyngioma resection were obtained from a previously published meta-analysis, including data published during or after the year 1990. Additionally, the year of publication, the country where procedures were performed, and the human development index of the country at time of publication were abstracted. Meta-regressional analyses were used to determine the significance of year and human development index as a covariate of the logit event rate of clinical outcomes. Statistical analyses were performed using the Comprehensive Meta-Analysis with a priori significance set as P < 0.05. RESULTS: A total of 100 studies (8230 patients) were examined, representing data from 19 countries. There was a significant increase in the achieved gross total resection rate (P = 0.0002) and a decrease in the achieved partial resection rate (P < 0.0001) across the time studied. Additionally, the rate of visual worsening (P = 0.025), postoperative cerebrospinal fluid leaks (P = 0.007), and development of meningitis (P = 0.032) decreased across time. CONCLUSIONS: This work suggests the existence of a global learning curve when examining clinical outcomes following endoscopic transsphenoidal craniopharyngioma resection. Globally, these findings highlight a general improvement in clinical outcomes across time.

Comparing Surgical Approaches for Craniopharyngioma Resection Among Adults and Children: A Meta-analysis and Systematic Review.

BACKGROUND: Craniopharyngioma treatment often necessitates surgical resection. Conventional approaches, such as transcranial and transsphenoidal approaches, are predominantly used. However, a recently adopted supraorbital approach may be more efficacious. Thus, this meta-analysis and systematic review aimed to compare the efficacy of the transcranial, transsphenoidal, and supraorbital approaches for resection and treatment of craniopharyngiomas. METHODS: This study was performed following PRISMA guidelines. Analyses were performed according to study design: (1) analyses for studies comparing several surgical approaches; and (2) analyses of all included studies. Random effects meta-analysis models were used to pool odds ratios among studies comparing several approaches. Similarly, categorical meta-regression models were used to examine the effect of surgical approach as a covariate of outcome data for all studies. Statistics were performed using Comprehensive Meta-Analysis software (CMA 3.3, Biostat, Englewood, NJ) (significance set at P < 0.05). RESULTS: Patients were well-matched for age, sex, and preoperative comorbidities between groups stratified by surgical approach. Analyses including 22 studies that compared several approaches demonstrated that the transsphenoidal group had a greater occurrence of postoperative visual improvement (P < 0.0001), lesser occurrence of visual deterioration (P < 0.0001), and lower tumor recurrence rate (P = 0.015) compared with the transcranial group. Only 2 studies compared the supraorbital approach to another approach, limiting analyses. Analyses including all studies demonstrated that the supraorbital group did not differ to either the transcranial or transsphenoidal group for any examined variables. CONCLUSIONS: The present study suggests that the transsphenoidal approach is associated with improved clinical outcomes for craniopharyngioma resection. There are limited data regarding the supraorbital approach, warranting future investigation.

Attenuated cardiac autonomic function in humans with high-affinity hemoglobin and compensatory polycythemia.

During hypoxic exposure, humans with high-affinity hemoglobin (and compensatory polycythemia) have blunted increases in heart rate compared with healthy humans with typical oxyhemoglobin dissociation curves. This response may be associated with altered autonomic control of heart rate. Our hypothesis-generating study aimed to investigate cardiac baroreflex sensitivity and heart rate variability among nine humans with high-affinity hemoglobin [6 females, O2 partial pressure at 50% [Formula: see text] (P50) = 16 ± 1 mmHg] compared with 12 humans with typical affinity hemoglobin (6 F, P50 = 26 ± 1 mmHg). Participants breathed normal room air for a 10-min baseline, followed by 20 min of isocapnic hypoxic exposure, designed to lower the arterial partial pressure O2 ([Formula: see text]) to ∼50 mmHg. Beat-by-beat heart rate and arterial blood pressure were recorded. Data were averaged in 5-min periods throughout the hypoxia exposure, beginning with the last 5 min of baseline in normoxia. Spontaneous cardiac baroreflex sensitivity and heart rate variability were determined using the sequence method and the time and frequency domain analyses, respectively. Cardiac baroreflex sensitivity was lower in humans with high-affinity hemoglobin than controls at baseline and during isocapnic hypoxic exposure (normoxia: 7 ± 4 vs. 16 ± 10 ms/mmHg, hypoxia minutes 15-20: 4 ± 3 vs. 14 ± 11 ms/mmHg; group effect: P = 0.02, high-affinity hemoglobin vs. control, respectively). Heart rate variability calculated in both the time (standard deviation of the N-N interval) and frequency (low frequency) domains was lower in humans with high-affinity hemoglobin than in controls (all P < 0.05). Our data suggest that humans with high-affinity hemoglobin may have attenuated cardiac autonomic function.