To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
This chapter provides the reader with an easy to reference tabular guide on a host of parameters relevant to the anesthetic care of children. The reader will find useful tables on normal hemodynamic parameters for children, sizing for equipment, analgesics and references for a variety of frequently used medications. The guide should serve to acquaint novice pediatric providers and may serves as a quick reference for all providers for less commonly administered agents.
Enteral sildenafil may be used in the intensive care unit for treatment of pulmonary arterial hypertension. We aimed to determine if initial enteral sildenafil dosing is safe in children receiving concurrent vasoactive infusions.
We performed a single-centre retrospective chart review that included patients less than 2 years of age in paediatric and cardiovascular intensive care units at an academic medical centre from 1 January, 2010 to 30 November, 2016. Included patients received concomitant enteral sildenafil and a continuously infused vasoactive agent. Exclusion criteria consisted of mechanical circulatory support, any form of dialysis, or a suspicion of septic shock at the time of sildenafil initiation. We sought to identify patients who developed worsening hemodynamic instability after initiation of enteral sildenafil defined as one or more of the following observations within 24 hours of sildenafil initiation: sildenafil discontinuation, total fluid bolus receipt >10 ml/kg, increased vasoactive support, epinephrine intravenous push administration, and/or the initiation of mechanical circulatory support.
Worsening hemodynamic instability was identified in 35% of the 130-patient cohort. Patients younger than 4 months were at increased risk of further hemodynamic instability compared with older patients (56% versus 44%, p = 0.0003) despite receiving lower median doses (1.28 mg/kg/day versus 1.78 mg/kg/day, p = 0.01).
Critically ill children receiving vasoactive infusions may be at increased risk for further hemodynamic instability after initiation of enteral sildenafil, particularly in younger patients. This population may benefit from lower starting enteral sildenafil doses of 0.25 mg/kg/dose or less every 8 hours to avoid further hemodynamic compromise.
Hemorrhage is the leading cause of preventable death in combat, although early recognition of hemorrhage is still challenging on the battlefield.
The objective of this study was to describe the shock index (SI) in a healthy military population, and to measure its variation during a controlled blood loss, simulated by blood donation.
A prospective observational study that enrolled military subjects, volunteers for blood donation, was conducted. Demographic and clinical information, concerning both the patient and the blood collection, were recorded. Baseline vital signs were measured, before and after donation, in a 45° supine position. Statistical analysis was performed after calculation of SI.
A total of 483 participants were included in the study. The mean blood donation volume was 473mL (SD = 44mL). The median pre- and post-blood donation SI were significantly different: 0.54 (IQR = 0.48-0.63) and 0.57 (IQR = 0.49-0.66), respectively (P = .002). Changes in pre-/post-donation blood pressure (BP) and heart rate (HR) also reached statistical difference but represented a clinically poor relevance. The multivariate analysis showed no significant associations between SI variations and age, sex, body mass index (BMI), sport activities, blood donation volume, and enteral volume replacement (EVR).
In this model of mild hemorrhage, SI exhibited significant variations but failed to reach clinical relevance. Further studies are needed to prove the benefit of SI calculation as a possible parameter for early recognition of hemorrhage in combat casualties at the point of injury.
Pasquier P, Duron S, Pouget T, Carbonnel AC, Boutonnet M, Malgras B, Barbier O, de Saint Maurice G, Sailliol A, Ausset S, Martinaud C. Use of shock index to identify mild hemorrhage: an observational study in military blood donors. Prehosp Disaster Med. 2019;34(3):303–307.
This study aimed to compare the effects of topical and systemic lignocaine on the circulatory response to direct laryngoscopy performed under general anaesthesia.
Ninety-nine patients over 20 years of age, with a physical status of I–II (classified according to the American Society of Anesthesiologists), were randomly allocated to 3 groups. One group received 5 ml of 0.9 per cent physiological saline intravenously, one group received 1.5 mg/kg lignocaine intravenously, and another group received seven puffs of 10 per cent lignocaine aerosol applied topically to the airway. Mean arterial pressures, heart rates and peripheral oxygen saturations were recorded, and changes in mean arterial pressure and heart rate ratios were calculated.
Changes in the ratios of mean arterial pressure and heart rate were greater in the saline physiological group than the other groups at 1 minute after intubation. Changes in the ratios of mean arterial pressure (at the same time point) were greater in the topical lignocaine group than in the intravenous lignocaine group, but this finding was not statistically significant.
Lignocaine limited the haemodynamic responses to laryngoscopy and endotracheal intubation during general anaesthesia in rigid suspension laryngoscopy.
Understanding blood flow in human body’s cerebral arterial system is of both fundamental and practical significance for prevention and treatment of vascular diseases. The mechanism and treatment for the growth of daughter aneurysm on its mother aneurysm are not yet fully understood. Themain purpose of the present paper is to elucidate the relationships between hemodynamics and the genesis, growth, subsequent rupture of the mother and daughter aneurysm on the cerebral vascular. The intensified stents with different porosities and structures are investigated to reduce the wall shear stress and pressure of mother and daughter aneurysm. The simulation is based on a lattice Boltzmann modeling of non-Newtonian blood flow. A novel stent structurewith “dense in front and sparse in rear” is proposed,which is verified to have good potential to reduce the wall shear stress of both mother and daughter aneurysm. The simulation is based on a lattice Boltzmann modeling of non-Newtonian blood flow. A novel stent structurewith “dense in front and sparse in rear” is proposed,which is verified to have good potential to reduce the wall shear stress of both mother and daughter aneurysm.
We present a fully automatic approach to recover boundary conditions and locations of the
vessel wall, given a crude initial guess and some velocity cross-sections, which can be
corrupted by noise. This paper contributes to the body of work regarding patient-specific
numerical simulations of blood flow, where the computational domain and boundary
conditions have an implicit uncertainty and error, that derives from acquiring and
processing clinical data in the form of medical images. The tools described in this paper
fit well in the current approach of performing patient-specific simulations, where a
reasonable segmentation of the medical images is used to form the computational domain,
and boundary conditions are obtained as velocity cross-sections from phase-contrast
magnetic resonance imaging. The only additional requirement in the proposed methods is to
obtain additional velocity cross-section measurements throughout the domain. The tools
developed around optimal control theory, would then minimize a user defined cost function
to fit the observations, while solving the incompressible Navier-Stokes equations.
Examples include two-dimensional idealized geometries and an anatomically realistic
saccular geometry description.
A distributed-parameter (one-dimensional) anatomically detailed model for the arterial
network of the arm is developed in order to carry out hemodynamics simulations. This work
focuses on the specific aspects related to the model set-up. In this regard, stringent
anatomical and physiological considerations have been pursued in order to construct the
arterial topology and to provide a systematic estimation of the involved parameters. The
model comprises 108 arterial segments, with 64 main arteries and 44 perforator arteries,
with lumen radii ranging from 0.24 cm – axillary artery- to 0.018 cm – perforator
arteries. The modeling of blood flow in deformable vessels is governed by a well-known set
of hyperbolic partial differential equations that accounts for mass and momentum
conservation and a constitutive equation for the arterial wall. The variational
formulation used to solve the problem and the related numerical approach are described.
The model rendered consistent pressure and flow rate outputs when compared with patient
records already published in the literature. In addition, an application to
dimensionally-heterogeneous modeling is presented in which the developed arterial network
is employed as an underlying model for a three-dimensional geometry of a branching point
to be embedded in order to perform local analyses.
The reliable and effective assimilation of measurements and numerical simulations in
engineering applications involving computational fluid dynamics is an emerging problem as
soon as new devices provide more data. In this paper we are mainly driven by hemodynamics
applications, a field where the progressive increment of measures and numerical tools
makes this problem particularly up-to-date. We adopt a Bayesian approach to the inclusion
of noisy data in the incompressible steady Navier-Stokes equations (NSE). The purpose is
the quantification of uncertainty affecting velocity and flow related variables of
interest, all treated as random variables. The method consists in the solution of an
optimization problem where the misfit between data and velocity - in a convenient norm -
is minimized under the constraint of the NSE. We derive classical point estimators, namely
the maximum a posteriori – MAP – and the maximum likelihood – ML – ones.
In addition, we obtain confidence regions for velocity and wall shear stress, a flow
related variable of medical relevance. Numerical simulations in 2-dimensional and
axisymmetric 3-dimensional domains show the gain yielded by the introduction of a complete
statistical knowledge in the assimilation process.
The parallel implementation of MUPHY, a concurrent multiscale code for large-scale hemodynamic simulations in anatomically realistic geometries, for multi-GPU platforms is presented. Performance tests show excellent results, with a nearly linear parallel speed-up on up to 32GPUs and a more than tenfold GPU/CPU acceleration, all across the range of GPUs. The basic MUPHY scheme combines a hydrokinetic (Lattice Boltzmann) representation of the blood plasma, with a Particle Dynamics treatment of suspended biological bodies, such as red blood cells. To the best of our knowledge, this represents the first effort in the direction of laying down general design principles for multiscale/physics parallel Particle Dynamics applications in non-ideal geometries. This configures the present multi-GPU version of MUPHY as one of the first examples of a high-performance parallel code for multiscale/physics biofluidic applications in realistically complex geometries.
Pre-eclampsia is a multisystem disorder unique to human pregnancy. Over the years, advances in the understanding of the pathophysiology and hemodynamics of the disease have greatly impacted its obstetrical and medical management. Considerable research into the pathophysiology of pre-eclampsia is ongoing and many areas are still debated. Increased heart rate, cardiac output, stroke volume, and left ventricular end-diastolic volume accommodates the growing metabolic needs of the pregnancy. Decreased total peripheral vascular resistance as a consequence of the presence of the low-resistance placental circulation is a physiological characteristic of a normal pregnancy. Current general consensus suggests a combined approach using clinical measurements and serum markers of placental abnormality appropriate for gestational age. Aspirin has been the most widely studied drug therapy in the prevention of pre-eclampsia. Spinal anesthesia is an acceptable option for women with severe pre-eclampsia, especially as an alternative to general anesthesia in emergency cesarean section.
The spatial domain of Molecular Dynamics simulations is usually a regular box that can be easily divided in subdomains for parallel processing. Recent efforts aimed at simulating complex biological systems, like the blood flow inside arteries, require the execution of Parallel Molecular Dynamics (PMD) in vessels that have, by nature, an irregular shape. In those cases, the geometry of the domain becomes an additional input parameter that directly influences the outcome of the simulation. In this paper we discuss the problems due to the parallelization of MD in complex geometries and show an efficient and general method to perform MD in irregular domains.
This chapter focuses on postoperative fluid management and early complications of lung transplantation (LT). Patients with emphysema who undergo single LT (SLT) require special attention to airway pressures and the compliance difference between the allograft and the native lung. Postoperative antimicrobial coverage should be modified if pathogens are identified in the sputum of the donor that is not already covered by the recipient-specific regimen. Postoperative hemodynamic instability has been common in patients with underlying pulmonary hypertension. Maintaining optimal nutrition in the postoperative period is essential and may improve operative outcomes. Early complications of LT can be classified into four categories: complications of the surgery itself, re-implantation response and primary graft dysfunction (PGD), immunologic complications including rejection, and organ-specific complications of the immunosuppressive agents. Standard therapy is recommended in the early post-transplant setting, although a focal structural abnormality may require surgical removal if it becomes the source of recurrent infection.
Intraoperative neurologic monitoring has been the subject of intense research for many years, the goal being to accurately identify intraoperative cerebral ischemia, and predict which patients may benefit from intraoperative shunting. This chapter presents a case study of a 73-year-old male scheduled for a right carotid endarterectomy (CEA) under general anesthesia. The patient experienced delayed emergence and displayed signs of a left hemiparesis. A diffusion-weighted magnetic resonance imaging confirmed the presence of a right-sided ischemic stroke in the middle cerebral artery (MCA) territory. For patients undergoing CEA under general anesthesia a number of monitoring modalities exist: monitors of cerebral hemodynamics, monitors of cerebral oxygenation and metabolism, and monitors of electrophysiologic parameters. None of the monitoring modalities commonly used for CEA under general anesthesia have been shown to either reliably identify or prevent cerebral ischemia or stroke, nor predict which patients may benefit from shunt placement.
Background: Exaggerated cardiovascular reactivity to stressful stimuli may be a risk factor for the development of hypertension. The genetic influence on blood pressure (BP) reactivity to stress and its control mechanisms has been receiving considerable support. This study aims at examining the heritability of BP and its intermediate hemodynamic phenotypes to acute stress in a homogeneous Arab population. Methods: Parameters were computed from continuous BP, electrocardiography and impedance cardiography measurements, during rest, word conflict (WCT) and cold pressor (CPT) tests. Heritability estimates (h2) were obtained using the variance components-based approach implemented in the SOLAR software package. Results: Reactivity scores for WCT and CPT increased significantly (P < .05) for systolic (SBP), diastolic (DBP), heart rate (HR), cardiac output (CO), and total peripheral resistance (TPR). They decreased significantly (P < .05) for stroke volume (SV), left ventricular ejection time (LVET), end diastolic (EDI) and cardiac contractility (IC) indices. Univariate analysis detected heritability estimates that ranged from 0.19–0.35 for rest, 0.002–0.40 for WCT and 0.08–0.35 for CPT. Conclusion: In this unique cohort, resting as well as challenged cardiovascular phenotypes are significantly influenced by additive genetic effects. Heritability estimates for resting phenotypes are in a relatively narrow range, while h2 for their reactivity is somewhat broader with lower estimates. Further analyses of this study may offer important opportunities for gene finding in hypertension. What is Known About the Topic: (1) cardiovascular reactivity to stress predicts cardiovascular disease; (2) genetic susceptibility plays an important role in stress reactivity. Family studies using the cold pressure test reported significant heritability for blood pressure. What this Study Adds: (1) this cohort is from five highly consanguineous isolated Arab pedigrees with genetically verified genealogical records and environmental homogeneity; (2) This is the first study to estimate heritability of detailed intermediate hemodynamic phenotypes that make up normal blood pressure.
Blood flow rheology is a very complex phenomenon. Hemodynamics owns Newtonian or non-Newtonian characteristic is still debatable. Recently, studies related to blood tend to classify blood as non-Newtonian fluid. In this research, power law, Casson and Carreau which are being the most popular non-Newtonian models are applied to investigate the hemodynamics variables that influence formation of thrombosis and predict damageability to blood cell. The branched arterial system is simplified as T-junction geometry and the computational fluid dynamics software Fluent 6.2 with finite volume method is utilized to analyze the blood flow rheology in cases of continuous and pulsatile flow. The analysis results are compared with that of Newtonian model and give out very interesting hemodynamics predictions for each model. The size of recirculation zone is different from each model that is observed significantly. The wall shear stress of Carreau model gets the highest value, 14% in case of continuous flow and around 17% in pulsatile case bigger than that of Newtonian model. The results of pulsatile flow show that the Newtonian model is closed to power law model while the Casson model is similar to the Carreau model.
the norwood procedure involves three separate stages of operative corrections. the first stage involves re-fashioning the pulmonary trunk into a neo-aorta so that it is possible to establish an unrestricted systemic circulation. an interpositional, or systemic-to-pulmonary arterial, shunt is then created between the neo-aorta and the pulmonary arteries to allow pulmonary perfusion and gas exchange. two of the available options for the systemic-to-pulmonary shunt are the central shunt and the right modified blalock-taussig shunt. in the setting of a central shunt, pulmonary perfusion is derived from a conduit placed between the pulmonary arterial bed and the neo-aorta whereas, in the modified blalock-taussig shunt, the conduit is interposed between one of the pulmonary arteries and the brachiocephalic artery. in subsequent stages, pulmonary perfusion is provided directly by deoxygenated blood. this is achieved by connecting, first, the superior caval vein, and then the inferior caval vein, to the pulmonary arteries. it is usually during the second stage that the systemic-to-pulmonary shunt is removed.
A landmark NINDS IV tPA trial showed that treatment with tPA within 3 hours of symptom onset improved neurologic impairment and functional outcome. Recently novel, semiquantitative PET measurements have been proposed to study the penumbra in humans that partially overcome the complexity of quantitative PET measurements. A perfusion-weighted imaging technique (PWI) is an evolving MR technology to study cerebral hemodynamics. The goal of hemodynamic imaging is to rapidly and accurately identify the area of hypoperfusion. Animal ischemia experiments have demonstrated that the lesion identified on diffusion-weighted imaging is larger than the area where ATP depletion has occurred; indicating that only part of the DWI lesion represents the ischemic core. The rationale of thrombolysis in acute stroke is to open occluded vessels and provide beneficial reperfusion. In animal stroke models, primary evidence of the efficacy of therapeutic intervention is established by a reduction in ischemic lesion volume compared to non-treated animals.
Perfusion-weighted magnetic resonance imaging (PWI) encompasses a set of techniques that create images depicting hemodynamics at the microvascular level. PWI offers the opportunity to study the pathophysiological events that lead most directly to ischemic damage. This chapter reviews the techniques employed in PWI with the role of contrast agents, and the MR pulse sequences that are usually chosen. Performing PWI with MRI rather than some other imaging modality offers the theoretical advantage that the contrast agent can be either an endogenous contrast agent that is naturally present in the blood or an exogenous one that is injected for the purpose of obtaining images. PWI techniques are usually designed to rely on gadolinium's susceptibility effect rather than its relaxivity effect, because these effects are exhibited over different ranges. PWI helps to identify tissue that is at risk of inclusion into growing infarcts.
We describe a three-year-old boy who presented with recurrent expectoration of bronchial casts six months following creation of a fenestrated lateral tunnel Fontan circulation for pulmonary atresia with intact ventricular septum. Cardiac catheterization demonstrated elevated central venous pressure with two areas of stenosis within the Fontan circuit, specifically at the junction of the right superior caval vein and the right pulmonary artery, and between the atrial baffle and the right superior caval vein. Insertion of Palmaz stents in these areas resulted in a reduction in central venous pressure, and a transient reduction in production of casts. Eight weeks after catheterization, however, he produced further casts, which resulted in hypoxia, respiratory arrest and death. We reviewed the autopsied specimens obtained from patients with the Fontan circulation over an eleven-year period at our institution in order to ascertain the prevalence of subclinical production of bronchial casts. We found no casts in the thirteen patients examined. Hemodynamic assessment is vital in all patients who develop this syndrome, and should be the primary focus of investigation, rather than solely directing efforts at lysis of casts.