BISoN: A Bayesian Framework for Inference of Social Networks.

Animal social networks are often constructed from point estimates of edge weights. In many contexts, edge weights are inferred from observational data, and the uncertainty around estimates can be affected by various factors. Though this has been acknowledged in previous work, methods that explicitly quantify uncertainty in edge weights have not yet been widely adopted, and remain undeveloped for many common types of data. Furthermore, existing methods are unable to cope with some of the complexities often found in observational data, and do not propagate uncertainty in edge weights to subsequent statistical analyses.We introduce a unified Bayesian framework for modelling social networks based on observational data. This framework, which we call BISoN, can accommodate many common types of observational social data, can capture confounds and model effects at the level of observations, and is fully compatible with popular methods used in social network analysis.We show how the framework can be applied to common types of data and how various types of downstream statistical analyses can be performed, including non-random association tests and regressions on network properties.Our framework opens up the opportunity to test new types of hypotheses, make full use of observational datasets, and increase the reliability of scientific inferences. We have made both an R package and example R scripts available to enable adoption of the framework.

Common permutation methods in animal social network analysis do not control for non-independence.

The non-independence of social network data is a cause for concern among behavioural ecologists conducting social network analysis. This has led to the adoption of several permutation-based methods for testing common hypotheses. One of the most common types of analysis is nodal regression, where the relationships between node-level network metrics and nodal covariates are analysed using a permutation technique known as node-label permutations. We show that, contrary to accepted wisdom, node-label permutations do not automatically account for the non-independences assumed to exist in network data, because regression-based permutation tests still assume exchangeability of residuals. The same assumption also applies to the quadratic assignment procedure (QAP), a permutation-based method often used for conducting dyadic regression. We highlight that node-label permutations produce the same p-values as equivalent parametric regression models, but that in the presence of non-independence, parametric regression models can also produce accurate effect size estimates. We also note that QAP only controls for a specific type of non-independence between edges that are connected to the same nodes, and that appropriate parametric regression models are also able to account for this type of non-independence. Based on this, we suggest that standard parametric models could be used in the place of permutation-based methods. Moving away from permutation-based methods could have several benefits, including reducing over-reliance on p-values, generating more reliable effect size estimates, and facilitating the adoption of causal inference methods and alternative types of statistical analysis. Supplementary Information: The online version contains supplementary material available at 10.1007/s00265-022-03254-x.

Generation and evaluation of intraoperative inferences for automated health care briefings on patient status after bypass surgery.

OBJECTIVE: The authors present a system that scans electronic records from cardiac surgery and uses inference rules to identify and classify abnormal events (e.g., hypertension) that may occur during critical surgical points (e.g., start of bypass). This vital information is used as the content of automatically generated briefings designed by MAGIC, a multimedia system that they are developing to brief intensive care unit clinicians on patient status after cardiac surgery. By recognizing patterns in the patient record, inferences concisely summarize detailed patient data. DESIGN: The authors present the development of inference rules that identify important information about patient status and describe their implementation and an experiment they carried out to validate their correctness. The data for a set of 24 patients were analyzed independently by the system and by 46 physicians. MEASUREMENTS: The authors measured accuracy, specificity, and sensitivity by comparing system inferences against physician judgments, in cases where all three physicians agreed and against the majority opinion in all cases. RESULTS: For laboratory inferences, evaluation shows that the system has an average accuracy of 98 percent (full agreement) and 96 percent (majority model). An analysis of interrater agreement, however, showed that physicians do not agree on abnormal hemodynamic events and could not serve as a gold standard for evaluating hemodynamic events. Analysis of discrepancies reveals possibilities for system improvement and causes of physician disagreement. CONCLUSIONS: This evaluation shows that the laboratory inferences of the system have high accuracy. The lack of agreement among physicians highlights the need for an objective quality-assurance tool for hemodynamic inferences. The system provides such a tool by implementing inferencing procedures established in the literature.

Personalizing retrieval of journal articles for patient care.

We present a system for patient-specific searches on a database of medical journal articles which uses natural language techniques to match search results against patient records. We performed an information retrieval experiment comparing the performance of this system to two strategies, one of which uses extensive medical knowledge, while the other uses the same patient information our system has. The results show that our system is useful in improving recall over the strategy simulating a human specialist, and clearly outperforms the strategy of using the patient record content without intelligent processing.

Venoarterial shunting for the treatment of right sided circulatory failure after left ventricular assist device placement.

Right sided circulatory failure (RSCF), a common complication after left ventricular assist device (LVAD) implantation, results in decreased systemic output due to diminished blood flow across the pulmonary vasculature. The authors hypothesized that creation of a venoarterial shunt (VAS) would decompress the right-sided circulation and improve systemic pressure and perfusion with significant arterial desaturation. An experimental model was created in which RSCF was induced acutely in a large animal (n = 6) by beta-blockade after LVAD placement. After VAS creation, hemodynamic and blood gas determinations were performed to compare non shunt and shunt states. After induction of heart failure after LVAD placement, VAS resulted in a 22% elevation in systemic blood pressure (p < 0.0001), a 36% elevation in cerebral blood flow (p = 0.02), and an 18% decrease in right sided filling pressures (p = 0.08). Systemic pH and aortic oxygen saturation remained unchanged from baseline. In a large animal model of RSCF after LVAD implantation, VAS improves systemic hemodynamics without a significant cost in arterial oxygenation to critical organs and without creating acid-base imbalance. Beside implementation, adjustable capabilities, easy removal and salutatory hemodynamic effects suggest that VAS may serve as a first line, short-term therapy for LVAD recipients who develop perioperative RSCF.

Noncardiac surgery in long-term implantable left ventricular assist-device recipients.

OBJECTIVE: The authors describe their experience with left ventricular assist-device (LVAD) recipients undergoing noncardiac surgery and delineate surgical, anesthetic, and logistic factors important in the successful intraoperative management of these patients. SUMMARY BACKGROUND DATA: Left ventricular assist-devices have become part of the armamentarium in the treatment of end-stage heart failure. As the numbers of patients chronically supported with long-term implantable devices grows, general surgical problems that are commonly seen in other hospitalized patients are becoming manifest. Of particular interest is the intraoperative management of patients undergoing elective noncardiac surgical procedures. METHODS: The anesthesia records and clinical charts were reviewed for eight ventricular assist-device recipients undergoing general surgical procedures between August 1, 1990 and August 31, 1994. RESULTS: A total of 12 procedures were performed in 6 men and 2 women averaging 52.7 years of age. Mean time elapsed from device implantation to operation was 68 +/- 35 days. Conventional inhalational and intravenous anesthetic techniques were well tolerated in these patients undergoing diverse surgical procedures. No perioperative mortality was observed. Five of eight patients went on to successful cardiac transplantation. CONCLUSIONS: Hemodynamic recovery after LVAD insertion has defined a new group of patients who develop noncardiac surgical problems often seen in other critically ill patients. Recognition of the unique potential problems that the LVAD recipient may encounter in the perioperative period--in particular patient positioning, device limitations, and fluid and inotropic management--will ensure an optimal surgical outcome for LVAD recipients undergoing noncardiac surgery.

Subarachnoid blockade alters homeostasis by modifying compensatory splanchnic responses to hemorrhagic hypotension.

To demonstrate that sympathetic responses transmitted by the splanchnic nerve help maintain intravascular stability, 12 mongrel dogs (35-45 kg each), anesthetized with pentobarbital, were given two separate but identical hypotensive stimuli (mean arterial blood pressure of 60 mm Hg for 15 min) by the withdrawal of appropriate amounts of blood. The first stimulus was performed in the absence of drug or surgical manipulation. The second stimulus was performed after animals were subjected to no intervention (n = 4), bilateral splanchnic nerve section (n = 4), or spinal anesthesia (n = 4). Before and 10 min after the onset of hypotension, arterial epinephrine concentration and adrenal medullary and abdominal organ blood flow were measured. In the group without intervention, the second hypotensive stimulus (like the first) elicited 3-fold increases in adrenal medullary blood flow, 40-fold increases in arterial epinephrine concentration, and a 61% reduction in abdominal organ blood flow (P greater than 0.002). The volume of blood withdrawn to produce hypotension was similar (approximately 21 ml.kg-1). Bilateral splanchnic nerve section attenuated the adrenal medullary blood flow, arterial epinephrine concentration, and abdominal organ blood flow responses to hypotension by 86, 64, and 66%, respectively (P less than 0.008), and the blood volume withdrawn was reduced by 42% (P less than 0.02). Spinal anesthesia eliminated the adrenal medullary blood flow response to hypotension, attenuated the arterial epinephrine concentration and abdominal organ blood flow responses by 78 and 57%, respectively (P less than 0.01), and decreased the blood volume extracted by 55% (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Epidural morphine decreases postoperative hypertension by attenuating sympathetic nervous system hyperactivity.

Twenty-four adults who were undergoing operations on the abdominal aorta were enrolled in a randomized, double-blind, placebo-controlled study in which epidural morphine sulfate (6 mg) was employed to attenuate the sympathoadrenal response to surgery to evaluate the possible contribution of sympathetic nervous system hyperactivity to postoperative hypertension. Patients who received epidural morphine required less parenteral morphine in the 24 hours following surgery, had lower analogue pain scores, and had markedly lower plasma norepinephrine levels when compared with patients in the control group who received an identical volume of saline in the epidural space. Epidural morphine had no effect on plasma epinephrine or arginine vasopressin levels. Fewer patients in the morphine group (4 of 12 vs 9 of 12 patients in the saline group) required treatment for hypertension (mean arterial blood pressure, greater than or equal to 110 mm Hg) in the 24 hours following surgery. In addition, patients in the morphine group had lower blood pressures in the 24 hours following surgery. These data suggest that sympathetic nervous system activity and not adrenal epinephrine or pituitary secretion of arginine vasopressin is responsible for the development of hypertension following aortic surgery. Furthermore, epidural narcotics appear to provide a means of attenuating this response.

Adrenergic receptors of adrenal medullary vasculature.

The present study evaluates possible effects of adrenal catecholamines, released by splanchnic nerve stimulation, on adrenal medullary blood flow (MQ) and adrenal catecholamine secretion (CS). Twelve pentobarbital-anesthetized mongrel dogs were subjected to three identical splanchnic nerve stimulations (5 V, 20 Hz, for 3 min) at 30-min intervals, and MQ (radiolabeled microsphere technique) and CS (high-performance liquid chromatography) were measured before and during each nerve stimulation. Animals were assigned to one of three groups and administered either saline, pindolol (1 and 4 mg/kg), or prazosin (1 and 4 mg/kg) before the second and third nerve stimulation, respectively. In the saline control group, each nerve stimulation resulted in similar increases in MQ and CS. Pindolol attenuated nerve stimulation-induced increases in MQ and CS by 50%, but had no effect on medullary catecholamine concentration. Prazosin augmented nerve stimulation-induced MQ, CS, and medullary catecholamine concentration by 35%. These data suggest that adrenal adrenergic receptors modulate elicited CS and mediate changes in adrenal medullary vascular tone.

Evaluation of sepsis in a critically ill surgical population.

We report a new clinical rating system which assesses septic patients' ongoing disease course and its severity. Our system incorporates the Therapeutic Intervention Scoring System (TISS) and Acute Physiology and Chronic Health Evaluation to measure discrete organ system abnormalities, plus a multiple system organ failure scale to quantify the number of abnormal organ systems. The resulting score, which reflects the severity of multiple organ dysfunction and grades responsiveness to therapy, was validated against the actual disease course. Retrospective and prospective profiles of individual surgical ICU patients demonstrated that this tracking method was a more effective indicator of severity of sepsis and more sensitive to the day-to-day changes in clinical status than either the TISS or APACHE II components alone. We also demonstrate that a graphic illustration of daily system scores yields clinically useful information relevant to the patients' septic course.

Neural control of adrenal medullary and cortical blood flow during hemorrhage.

Hemorrhagic hypotension produces an increase in adrenal medullary blood flow and a decrease in adrenal cortical blood flow. To determine whether changes in adrenal blood flow during hemorrhage are neurally mediated, we compared blood flow responses following adrenal denervation (splanchnic nerve section) with changes in the contralateral, neurally intact adrenal. Blood pressure was reduced and maintained at 60 mmHg for 25 min by hemorrhage into a pressurized bottle system. Adrenal cortical blood flow decreased to 50% of control with hemorrhage in both the intact and denervated adrenal. Adrenal medullary blood flow increased to four times control levels at 15 and 25 min posthemorrhage in the intact adrenal, but was reduced to 50% of control at 3, 5, and 10 min posthemorrhage in the denervated adrenal. In a separate group of dogs, the greater splanchnic nerve on one side was electrically stimulated at 2, 5, or 15 Hz (n = 4 each group) for 40 min. Adrenal medullary blood flow increased 5- to 10-fold in the stimulated adrenal but was unchanged in the contralateral, nonstimulated adrenal. Adrenal cortical blood flow was not affected by nerve stimulation. We conclude that activity of the splanchnic nerve profoundly affects adrenal medullary vessels but not adrenal cortical vessels and mediates the observed increase in adrenal medullary blood flow during hemorrhagic hypotension.