Effect of position and weight force on inferior vena cava diameter – Implications for arrest-related death

Position- and posture-dependent vascular imaging-a scoping review

OBJECTIVES

Position- and posture-dependent deformation of the vascular system is a relatively unexplored field. The goal of this scoping review was to create an overview of existing vascular imaging modalities in different body positions and postures and address the subsequent changes in vascular anatomy.

METHODS

Scopus, Medline, and Cochrane were searched for literature published between January 1, 2000, and June 30, 2022, incorporating the following categories: image modality, anatomy, orientation, and outcomes.

RESULTS

Out of 2446 screened articles, we included 108. The majority of papers used ultrasound (US, n = 74) in different body positions and postures with diameter and cross-sectional area (CSA) as outcome measures. Magnetic resonance imaging (n = 22) and computed tomography (n = 8) were less frequently used but allowed for investigation of other geometrical measures such as vessel curvature and length. The venous system proved more sensitive to postural changes than the arterial system, which was seen as increasing diameters of veins below the level of the heart when going from supine to prone to standing positions, and vice versa.

CONCLUSIONS

The influence of body positions and postures on vasculature was predominantly explored with US for vessel diameter and CSA. Posture-induced deformation and additional geometrical features that may be of interest for the (endovascular) treatment of vascular pathologies have been limitedly reported, such as length and curvature of an atherosclerotic popliteal artery during bending of the knee after stent placement. The most important clinical implications of positional changes are found in diagnosis, surgical planning, and follow-up after stent placement.

CLINICAL RELEVANCE STATEMENT

This scoping review presents the current state and opportunities of position- and posture-dependent imaging of vascular structures using various imaging modalities that are relevant in the fields of clinical diagnosis, surgical planning, and follow-up after stent placement.

KEY POINTS

• The influence of body positions and postures on the vasculature was predominantly investigated with US for vessel diameter and cross-sectional area. • Research into geometrical deformation, such as vessel length and curvature adaptation, that may be of interest for the (endovascular) treatment of vascular pathologies is limited in different positions and postures. • The most important clinical implications of postural changes are found in diagnosis, surgical planning, and follow-up after stent placement.

Prone restraint death: Possible role of the Valsalva maneuver

There is an on-going debate about the safety of prone restraint and the exact role of the prone position in physical restraint death. Cardiac arrest in prone restraint death is essentially the end-result of a violent physical altercation wherein a combative individual suddenly loses consciousness while trying to counteract an opposing force. The direct correlations of increased static weight force with decreased inferior vena cava diameter, decreased cardiac output, and decreased stroke volume in prone restraint studies suggest that decreased venous return and decreased cardiac output could have a significant role to play in prone restraint death. Although the degree of changes observed in those studies might not be sufficient to cause cardiac arrest, they could predispose people who instinctively try to free themselves of the restraints to severe complications. The Valsalva maneuver, or forceful expiration against a closed airway, is frequently performed spontaneously in daily activities involving straining and resistance exercise, but has never been considered in restraint death. Pre-existing diminished venous return could increase the risk of major complications in individuals performing the Valsalva maneuver. A substantial decrease in venous return and cardiac output could increase the risk of cerebral hypoperfusion, loss of consciousness, hypoventilation, and sudden death. By increasing the risk of increased intra-abdominal pressure and its negative effect on venous return, high body mass index may be a significant risk factor in prone restraint death. The Valsalva maneuver may have different roles in prone restraint cardiac arrest and might be overlooked in prone restraint death.

Ultrasonographically derived caudal vena cava parameters acquired in a standing position and lateral recumbency in healthy, lightly sedated cats: a pilot study

OBJECTIVES

The aim of this study was to determine the feasibility of ultrasonographically measuring the caudal vena cava (CVC) at the subxiphoid view of healthy, lightly sedated cats in a standing position and lateral recumbency.

METHODS

This was a prospective, observational, experimental single-centre study. Twenty healthy research-purposed cats were enrolled. Two trained operators scanned each cat in two positions - standing and lateral recumbency - in a randomised order. CVC diameter was measured at the narrowest diameter during inspiration and at the widest diameter during expiration, at two anatomical locations along the CVC - where the CVC crosses the diaphragm (base) and 2 mm caudal to the diaphragm. The CVC collapsibility index (CVC-CI) was calculated for each site. Normalcy was assessed with a Shapiro-Wilk test. A one-way ANOVA with post-hoc Tukey's test was used to compare inspiratory with expiratory values within and between groups. A paired t-test compared the CVC-CI between groups (P ⩽0.05 indicated statistical significance). Spearman's correlation and Bland-Altman analysis assessed inter-operator variability.

RESULTS

All ultrasonographic data passed normalcy and were reported as mean ± SD. When compared with each other, inspiratory and expiratory values were statistically different for position, location and operator (all P <0.0001). There was no statistically significant difference between lateral recumbency or standing position for inspiratory, expiratory and CVC-CI values. Inter-operator variability was substantial, with operator 2 consistently obtaining smaller measurements than operator 1. The mean CVC-CI in lateral recumbency at the base was 24% for operator 1 and 37% for operator 2. For the same site in standing position, CVC-CI was 27% and 41% for operators 1 and 2, respectively.

CONCLUSIONS AND RELEVANCE

This pilot study demonstrates that it is possible to ultrasonographically measure the CVC diameter in both lateral recumbency and a standing position in healthy, lightly sedated cats. However, measurements obtained are operator dependent with variability between individuals. Further studies are needed to determine if ultrasonographic CVC assessment will prove helpful in estimating intravascular volume status in cats.

Prone restraint cardiac arrest: A comprehensive review of the scientific literature and an explanation of the physiology

Deaths occurring among agitated or violent individuals subjected to physical restraint have been attributed to positional asphyxia. Restraint in the prone position has been shown to alter respiratory and cardiac physiology, although this is thought not to be to the degree that would cause asphyxia in a healthy, adult individual. This comprehensive review identifies and summarizes the current scientific literature on prone position and restraint, including experiments that assess physiology on individuals restrained in a prone position. Some of these experimental approaches have attempted to replicate situations in which prone restraint would be used. Overall, most findings revealed that individuals subjected to physical prone restraint experienced a decrease in ventilation and/or cardiac output (CO) in prone restraint. Metabolic acidosis is noted with increased physical activity, in restraint-associated cardiac arrest and simulated encounters. A decrease in ventilation and CO can significantly worsen acidosis and hemodynamics. Given these findings, deaths associated with prone physical restraint are not the direct result of asphyxia but are due to cardiac arrest secondary to metabolic acidosis compounded by inadequate ventilation and reduced CO. As such, the cause of death in these circumstances would be more aptly referred to as "prone restraint cardiac arrest" as opposed to "restraint asphyxia" or "positional asphyxia."

Arrest-related death on the basis of a drug-induced excited delirium syndrome

AIMS

In typical arrest-related death (ARD) scenarios, the victims often show signs of excited delirium syndrome (ExDS), intoxication, exhaustion and/or suffered from a preexisting physical or psychiatrical condition, all of which could have caused or at least triggered the person's death. Since autopsy findings are very rare in such cases, a clear clinicopathologic diagnosis and thus mechanism of death is rarely found.

METHODS

We present a case of a 25-year old woman, who died while being arrested by the police. Based on the patient's medical history, autopsy findings, contradicting witness testimonies, and reliable clinical and toxicological blood parameters, the most probable diagnosis is discussed.

RESULTS

The cause of death was determined as cardiac arrest subsequent to a combination of excited delirium syndrome, physical exhaustion and respiratory impairment. The manner of death was unnatural and juridically, the charges were dropped.

CONCLUSIONS

In cases, where the cause and mechanism of death can only be diagnosed by exclusion, police collaboration, detailed clinical history (past and present) as well as clinical blood parameter analyses are necessary to help evaluating possible contributing factors and the most probable cause of death in ARD.

Restraint physiology: A review of the literature

Law-enforcement often uses forensic restraints to control individuals and often these individuals are placed in positions and with various amounts of weight used to hold them in place. There has been a moderate amount of research performed on humans in this field of study to assess the physiologic impact of the positions and weight on ventilatory and cardiovascular parameters. This review discusses the scientific medical literature on the use of restraints and restraint position including the use of weight force and aggregates the findings in specific physiologic areas, such as impact on blood pressure, heart rate, and ventilatory parameters.

EXCITATION study: Unexplained in-custody deaths: Evaluating biomarkers of stress and agitation

BACKGROUND

Law enforcement personnel often confront violent and dangerous individuals suffering from Excited Delirium Syndrome (ExDS) who need emergent medical evaluation and treatment to optimize the best outcomes for this potentially lethal medical emergency. These subjects typically require physical restraint and use of force measures to control them. We sought to determine if stress-related biomarkers can differentiate ExDS subjects when compared with agitation and stress under other circumstances, including agitation and extreme physical exhaustion and restraint coupled with emotional stressors.

METHODS

This was a prospective multi-center study enrolling a convenience sample of patients who presented with agitation or ExDS. Patients were enrolled from three academic emergency departments (ED), two in the United States and one in Canada. Three study groups (SG) included: SG1) patients brought to the ED with ExDS based on the use of standardized clinical criteria; SG2) ED patients with acute agitation who were not in a clinical state of ExDS but required sedation; SG3) a laboratory control group of subjects exercised to physical exhaustion, restrained, and psychologically stressed with threat of Conducted Energy Device (CED) activation. We examined a panel of stress-related biomarkers, including norepinephrine (NE), cortisol, copeptin, orexin A, and dynorphin (Dyn) from the blood of enrolled subjects.

RESULTS

A total of 82 subjects were enrolled: 31 in the agitation group, 21 in the ExDS group, and 30 in the laboratory control group. Data were analyzed, comparing the findings between ExDS and the two other groups to determine if specific stress-related biomarkers are associated with ExDS. Biomarker comparisons between subjects identified with ExDS, agitation, and control groups demonstrated that cortisol levels were more elevated in the ExDS group compared with the other groups. Orexin was only significant in ExDs (with Agitated tendency but lot of variability in the group). NE and Dyn increased as response to stress in Agitated and ExDS.

CONCLUSIONS

Cortisol levels were more elevated in subjects in the ExDS group compared with the other comparison groups and orexin was elevated in ExDS compared to controls, a trend that did not reach statistical significance in the agitated group. The clinical or diagnostic significance of these difference have yet to be defined and warrants further study.

Assessment of Volume Status During Prone Spine Surgery via a Novel Point-of-care Ultrasound Technique

Background Operations performed with the patient in the prone position can pose a significant challenge to the anesthesiologist. Hypotension is a commonly encountered complication. Intravascular volume depletion and decreased cardiac output secondary to decreased preload are thought to be the most likely cause of hypotension in the prone position. Measurement of inferior vena cava (IVC) diameter via point-of-care ultrasound examination (POC_US) has been used to provide an estimate of intravascular volume status. However, this measurement is most often obtained with the patient in the supine position. Materials and methods In this study, we describe a technique for evaluating IVC diameter via POC_US in the prone position. Right lateral long axis imaging of the IVC was used to assess the intravascular volume status of 10 patients undergoing lumbar spine surgery in the prone position. In addition, we used a non-invasive measure of cardiac output to correlate changes in IVC width with changes in cardiac output. Results Images of the IVC in the prone position were obtainable in all 10 patients. IVC diameter increased in six out of 10 patients on going from supine to prone position. The increase in IVC diameter corresponded to an increase in cardiac output, measured noninvasively in five out of the six patients. Conclusions Our findings indicate that POC_US examination of the IVC is possible in the prone position. Further study of a larger patient population could demonstrate the utility of this technique in assessing intravascular volume status in patients undergoing surgery in the prone position.

Feasibility and Safety of Ultrasonography Guidance and Flank Position during Percutaneous Nephrolithotomy

PURPOSE

Percutaneous nephrolithotomy is generally performed using fluoroscopy, which is associated with exposure to radiation. Another drawback of fluoroscopic guided percutaneous nephrolithotomy is the prone position, which is not suitable for all patients. In this study we evaluated the feasibility, safety and efficacy of ultrasound guided percutaneous nephrolithotomy with the patient in the flank position.

MATERIALS AND METHODS

A total of 603 patients with a mean ± SD age of 50.9 ± 13 years were included in this study from December 2010 to July 2016. Access to the collecting system and tract dilation were performed under ultrasound guidance. Perioperative data on the stone-free rate, operative time, length of stay and complication rates were recorded.

RESULTS

Successful access was achieved in all but 1 patient. Mean operative time was 56.6 ± 6.5 minutes. Complete stone clearance was achieved in 529 patients (87.7%) and Clavien-Dindo grade 3 complications were noted in 17 (2.8%). Blood transfusion was necessary in 43 patients (7.1%). However, bleeding was self-limited in all cases and did not require angioembolization.

CONCLUSIONS

To our knowledge this is the largest series of ultrasound guided percutaneous nephrolithotomy with the patient in the flank position. Unlike in other studies we used this procedure in all patients irrespective of stone burden, renal anomaly and body habitus. Ultrasound guided percutaneous nephrolithotomy has outcomes comparable to those of conventional percutaneous nephrolithotomy and it is not associated with radiation exposure. Furthermore, anesthesia while in the flank position might be less harmful in some patients, including those with obesity or cardiopulmonary comorbidities.

Restraint in mental health settings: is it time to declare a position?

The emergence of a drive to reduce restrictive interventions has been accompanied particularly in the UK by a debate focussing on restraint positions. Any restraint intervention delivered poorly can potentially lead to serious negative outcomes. More research is required to reliably state the risk attached to a particular position in a particular clinical circumstance.Declaration of interestF.S. is a consultant psychiatrist in Psychiatric Intensive Care at the Maudsley Hospital, London. He is on the Executive Committee of the National Association of Psychiatric Intensive Care and Low Secure Units, and was a member of the National Institute for Health and Care Excellence Guideline Development Group for the Short-Term Management of Aggression and Violence (2015). J.P. is a senior lecturer at the Faculty of Health and Life Sciences, Coventry University. E.B. is a consultant and expert witness in violence reduction and the use of physical interventions, independent expert to the High Secure Hospitals Violence Reduction Manual Steering Group and a member of the College of Policing Guideline Committee Steering Group and Mental Health Restraint Expert Reference Group. B.P. is the clinical director for Crisis and Aggression Limitation and Management (CALM) Training and formerly a senior lecturer for the Faculty of Health, University of Stirling. He is a nurse and psychotherapist and presently chairs the European Network for Training in the Management of Aggression. A.O'B. is a consultant psychiatrist, the Director of Educational Programmes for the National Association of Psychiatric Intensive Care and Low Secure Units, and the Dean for Students at St George's University of London.

Intubation of Profoundly Agitated Patients Treated with Prehospital Ketamine

Background

Profound agitation in the prehospital setting confers substantial risk to patients and providers. Optimal chemical sedation in this setting remains unclear.

Objective

The goal of this study was to describe intubation rates among profoundly agitated patients treated with prehospital ketamine and to characterize clinically significant outcomes of a prehospital ketamine protocol.

Methods

This was a retrospective cohort study of all patients who received prehospital ketamine, per a predefined protocol, for control of profound agitation and who subsequently were transported to an urban Level 1 trauma center from May 1, 2010 through August 31, 2013. Identified records were reviewed for basic ambulance run information, subject characteristics, ketamine dosing, and rate of intubation. Emergency Medical Services (EMS) ambulance run data were matched to hospital-based electronic medical records. Clinically significant outcomes are characterized, including unadjusted and adjusted rates of intubation.

Results

Overall, ketamine was administered 227 times in the prehospital setting with 135 cases meeting study criteria of use of ketamine for treatment of agitation. Endotracheal intubation was undertaken for 63% (85/135) of patients, including attempted prehospital intubation in four cases. Male gender and late night arrival were associated with intubation in univariate analyses (χ2=12.02; P=.001 and χ2=5.34; P=.021, respectively). Neither ketamine dose, co-administration of additional sedating medications, nor evidence of ethanol (ETOH) or sympathomimetic ingestion was associated with intubation. The association between intubation and both male gender and late night emergency department (ED) arrival persisted in multivariate analysis. Neither higher dose (>5mg/kg) ketamine nor co-administration of midazolam or haloperidol was associated with intubation in logistic regression modeling of the 120 subjects with weights recorded. Two deaths were observed. Post-hoc analysis of intubation rates suggested a high degree of provider-dependent variability.

Conclusions

Prehospital ketamine is associated with a high rate of endotracheal intubation in profoundly agitated patients; however, ketamine dosing is not associated with intubation rate when adjusted for potential confounders. It is likely that factors not included in this analysis, including both provider comfort with post-ketamine patients and anticipated clinical course, play a role in the decision to intubate patients who receive prehospital ketamine.

OlivesTD, NystromPC, ColeJB, DoddKW, HoJD. Intubation of profoundly agitated patients treated with prehospital ketamine. Prehosp Disaster Med. 2016;31(6):593–602.

Prehospital use of i.m. ketamine for sedation of violent and agitated patients

INTRODUCTION

Violent and agitated patients pose a serious challenge for emergency medical services (EMS) personnel. Rapid control of these patients is paramount to successful prehospital evaluation and also for the safety of both the patient and crew. Sedation is often required for these patients, but the ideal choice of medication is not clear. The objective is to demonstrate that ketamine, given as a single intramuscular injection for violent and agitated patients, including those with suspected excited delirium syndrome (ExDS), is both safe and effective during the prehospital phase of care, and allows for the rapid sedation and control of this difficult patient population.

METHODS

We reviewed paramedic run sheets from five different catchment areas in suburban Florida communities. We identified 52 patients as having been given intramuscular ketamine 4 mg/kg i.m., following a specific protocol devised by the EMS medical director of these jurisdictions, to treat agitated and violent patients, including a subset of which would be expected to suffer from ExDS. Twenty-six of 52 patients were also given parenteral midazolam after medical control was obtained to prevent emergence reactions associated with ketamine.

RESULTS

Review of records demonstrated that almost all patients (50/52) were rapidly sedated and in all but three patients no negative side effects were noted during the prehospital care. All patients were subsequently transported to the hospital before ketamine effects wore off.

CONCLUSION

Ketamine may be safely and effectively used by trained paramedics following a specific protocol. The drug provides excellent efficacy and few clinically significant side effects in the prehospital phase of care, making it an attractive choice in those situations requiring rapid and safe sedation especially without intravenous access.

Investigation of Deaths Temporally Associated with Law Enforcement Apprehension

The investigation of a death that occurs in custody requires a careful and methodical approach since concerns of police or institutional misconduct may be raised. The medicolegal official charged with the investigation and ultimate certification of death bears heavy responsibility to the decedent's family, the public, law enforcement and other institutions. A wide variety of causes of death and manners of death are seen in these deaths. This paper reviews causes, mechanisms, manners, findings, and evaluation of persons who have died in temporal relation to legal apprehension.