Automated drug delivery system to control systemic arterial pressure, cardiac output, and left heart filling pressure in acute decompensated heart failure

System Design for Optimizing Drug Infusions Using Cardiovascular Space Mapping for Acute Heart Failure

Acute heart failure is caused by various factors and requires multiple drug therapies to remedy underlying causes. Due to the complexity of pharmacologic effects of cardiovascular agents, few studies have theoretically addressed the multidrug optimization problem. This paper proposes a drug infusion system for acute heart failure that controls cardiovascular performance metrics (cardiac output, left atrial pressure, and mean arterial pressure) within desired ranges as dictated by the cardiovascular parameters (systemic vascular resistance, cardiac contractility, heart rate, and stressed blood volume). The key to our system design is modeling and controlling cardiovascular parameters to yield the desired cardiovascular metrics. A 'tailored drug infusion' technique controls parameters by solving the optimization problem in order to conquer the complexity of multi-dependencies and the different dosage limits among multiple drugs. A 'cardiovascular space mapping' technique identifies the desired parameters from the desired metrics by deriving the analytical solutions of the metrics as functions of the parameters. To facilitate clinical discussions, parameters were set to realistic values in 5,600 simulated patients. Our results showed not only that the optimized drug combinations and dosages controlled the cardiovascular metrics to within the desired ranges, but also that they mostly corresponded to the recommended clinical use guidelines. An additional value of our system is that it proactively predicts the limitations of the tailored drug therapy, which supports the clinical decision of pivoting to alternative treatment strategies such as mechanical circulatory support.

Development of an automated closed-loop β-blocker delivery system to stably reduce myocardial oxygen consumption without inducing circulatory collapse in a canine heart failure model: a proof of concept study

Beta-blockers are well known to reduce myocardial oxygen consumption (MVO₂) and improve the prognosis of heart failure (HF) patients. However, its negative chronotropic and inotropic effects limit their use in the acute phase of HF due to the risk of circulatory collapse. In this study, as a first step for a safe β-blocker administration strategy, we aimed to develop and evaluate the feasibility of an automated β-blocker administration system. We developed a system to monitor arterial pressure (AP), left atrial pressure (P_LA), right atrial pressure, and cardiac output. Using negative feedback of hemodynamics, the system controls AP and P_LA by administering landiolol (an ultra-short-acting β-blocker), dextran, and furosemide. We applied the system for 60 min to 6 mongrel dogs with rapid pacing-induced HF. In all dogs, the system automatically adjusted the doses of the drugs. Mean AP and mean P_LA were controlled within the acceptable ranges (AP within 5 mmHg below target; P_LA within 2 mmHg above target) more than 95% of the time. Median absolute performance error was small for AP [median (interquartile range), 3.1% (2.2–3.8)] and P_LA [3.6% (2.2–5.7)]. The system decreased MVO₂ and P_LA significantly. We demonstrated the feasibility of an automated β-blocker administration system in a canine model of acute HF. The system controlled AP and P_LA to avoid circulatory collapse, and reduced MVO₂ significantly. As the system can help the management of patients with HF, further validations in larger samples and development for clinical applications are warranted.

Low-Dose Landiolol Reduces Heart Rate and Cardiac Oxygen Consumption Without Compromising Initial Hemodynamic Resuscitation in a Canine Model of Endotoxin Shock

In septic shock, it is not known whether β-blocker can be used to reduce heart rate (HR) safely during the initial phase of hemodynamic resuscitation. The purpose of this study was to experimentally investigate the effects of low-dose landiolol, a β-blocker, on initial hemodynamic resuscitation in dogs with endotoxin shock. In 13 anesthetized dogs [n = 7 in control (CT) group, n = 6 in β-blockade (BB) group], after endotoxin shock was induced by intravenous infusion of lipopolysaccharide (4 mg kg), we started hemodynamic resuscitation to restore mean arterial pressure (AP) and cardiac output (CO) by infusing noradrenaline (NA) and Ringer acetate solution (RiA). During 4 h of hemodynamic resuscitation, dose of NA and RiA were automatically titrated with use of a computer-controlled drug infusion system that we developed previously. In BB group, landiolol was administered at a low-dose range (1-10 μg kg min) to lower HR to lower than 140 bpm. Hemodynamic resuscitation using the system restored AP to 70 mmHg and CO to greater than 90% of baseline level similarly in both groups. Throughout resuscitation, HR and indices of cardiac contractility were significantly lower in BB group than in CT group. However, there were no significant intergroup differences in the dose of NA and RiA. During First 2 h of resuscitation, cardiac oxygen consumption was significantly lower in BB group than in CT group. In conclusion, low-dose landiolol may reduce HR without compromising initial hemodynamic resuscitation in septic shock. To clearly establish this, large-size randomized study using animal models more relevant to septic shock is needed.

Computer-controlled closed-loop drug infusion system for automated hemodynamic resuscitation in endotoxin-induced shock

Background

Hemodynamic resuscitation in septic shock requires aggressive fluid replacement and appropriate use of vasopressors to optimize arterial pressure (AP) and cardiac output (CO). Because responses to these drugs vary between patients and within patient over time, strict monitoring of patient condition and repetitive adjustment of drug dose are required. This task is time and labor consuming, and is associated with poor adherence to resuscitation guidelines. To overcome this issue, we developed a computer-controlled closed-loop drug infusion system for automated hemodynamic resuscitation in septic shock, and evaluated the performance of the system in a canine model of endotoxin shock.

Methods

Our system monitors AP, CO and central venous pressure, and computes arterial resistance (R), stressed blood volume (V) and Frank-Starling slope of left ventricle (S). The system controls R with noradrenaline (NA), and V with Ringer’s acetate solution (RiA), thereby controlling AP and CO. In 4 dogs, AP and CO were measured invasively. In another 4 dogs, AP and CO were measured less invasively using clinically acceptable modalities, aiming to make the system clinically feasible. In all 8 dogs, endotoxin shock was induced by injecting Escherichia coli lipopolysaccharide, which significantly decreased AP from 95 (91–108) to 43 (39–45) mmHg, and CO from 112 (104–142) to 62 (51–73) ml·min⁻¹·kg⁻¹. The system was then connected to the dogs, and activated. System performance was observed over a period of 4 h.

Results

Our system immediately started infusions of NA and RiA. Within 40 min, RiA increased V to target level, and NA maintained R at target level, while S was concomitantly increased. These resulted in restoration of AP to 70 (69–71) mmHg and CO to 130 (125–138) ml·min⁻¹·kg⁻¹. Median of absolute performance error, an index of precision of control, was small in AP [2.5 (2.1–4.5) %] and CO [2.4 (1.4–5.5) %], which were not increased even when the variables were measured less invasively.

Conclusions

In a canine model of endotoxin shock, our system automatically improved and maintained AP and CO at their target values with small performance error. Our system is potentially an attractive clinical tool for rescuing patients with septic shock.

Electronic supplementary material

The online version of this article (10.1186/s12871-017-0437-9) contains supplementary material, which is available to authorized users.

Less Invasive and Inotrope-Reduction Approach to Automated Closed-Loop Control of Hemodynamics in Decompensated Heart Failure

We have been developing an automated cardiovascular drug infusion system for simultaneous control of arterial pressure (AP), cardiac output (CO), and left atrial pressure (PLA) in decompensated heart failure (HF). In our prototype system, CO and PLA were measured invasively through thoracotomy. Furthermore, the control logic inevitably required use of inotropes to improve hemodynamics, which was not in line with clinical HF guidelines. The goal of this study was to solve these problems and develop a clinically feasible system. We integrated to the system minimally invasive monitors of CO and pulmonary capillary wedge pressure (PCWP, surrogates for PLA) that we developed recently. We also redesigned the control logic to reduce the use of inotrope. We applied the newly developed system to nine dogs with decompensated HF. Once activated, our system started to control the infusion of vasodilator and diuretics in all the animals. Inotrope was not infused in three animals, and infused at minimal doses in six animals that were intolerant of vasodilator infusion alone. Within 50 min, our system controlled AP, CO, and PCWP to their respective targets accurately. Pulmonary artery catheterization confirmed optimization of hemodynamics (AP, from 98 ± 4 to 74 ± 11 mmHg; CO, from 2.2 ± 0.5 to 2.9 ± 0.3 L·min(-1)·m(-2); PCWP, from 27.0 ± 6.6 to 13.8 ± 3.0 mmHg). In a minimally invasive setting while reducing the use of inotrope, our system succeeded in automatically optimizing the overall hemodynamics in canine models of HF. The present results pave the way for clinical application of our automated drug infusion system.

An analytic tool for prediction of hemodynamic responses to vasopressors

This paper presents a new analytic tool for automated control of vasopressor infusion, which uses measured changes in blood pressure to infer changes in the underlying cardiovascular system and then estimate dose-response relationships for the underlying cardinal cardiovascular parameters, i.e., those related to cardiac output (CO) and total peripheral resistance (TPR). Ultimately, blood pressure as a function of vasopressor dose is predicted based on the estimated underlying cardiovascular state by extrapolating the dose-response relationship. As well, this tool adapts to individual subjects with a minimum of individualized training data. In this report, proof-of-principle is provided using experimental epinephrine dose-response data from four different sets of subjects. Given two observations from different infusion rates, the analytic tool was able to accurately predict the groups' blood pressure, heart rate, TPR, stroke volume, and CO as a function of vasopressor dose levels: the root-mean-squared prediction error for the mean arterial pressure (MAP) was consistently smaller than 5% of the underlying MAP; the r(2) values for the TPR, stroke volume, and CO were consistently higher than 0.96; and the limits of agreement between actual versus predicted blood pressure (BP), TPR, stroke volume, and CO were consistently smaller than 8% of the respective underlying values. The proposed analytic tool may provide a meaningful step towards automated control of vasopressor therapy.

Adaptive multi-infusion decision support for the multivariable circulatory management of critically ill patients

We have developed a novel adaptive multi-infusion advisory system for circulatory management of critically ill patients which co-ordinates infusion adjustments to ensure safe trajectories. This system should reduce patient hospital stay and improve patient outcome by enhancing the quality of patient circulatory control; alleviating the clinical cognitive load, giving staff more time for direct patient care, while also reducing infusion adjustment errors. We have applied three derived circulatory variables which relate to the three main types of cardiovascular infusions (inotropic, vasoactive and fluid). A lumped parameter steady flow model of the human circulatory system and the effects of cardiovascular infusions was constructed for algorithm development, clinical experts providing feedback on a representative test set of simulated patients in circulatory shock. Independent self-learning fuzzy logic controllers (SLFLC) were found to give good adaptation to variable patient infusion sensitivities. A supervisory, rule-based module co-ordinates infusion adjustments to ensure safe circulatory trajectories. Monitoring of manual infusion adjustments allows timely advice and also a critiquing capability which can train junior staff and reduce infusion adjustment errors. A physical mock circulatory loop was used to construct and test our physical advisory system. Preliminary clinical results show good clinical utility of our adaptive multi-infusion advisory system.

Reduction of myocardial oxygen demand by controlling heart rate and hemodynamics simultaneously by novel circulatory model

We were already capable of restoring automatically blood pressure, cardiac output, and left atrial pressure by an inotropic, a vasodilator, and volume infusion/a diuretic. Countermeasures for cardioprotection, however, should be integrated to improve the long-term outcomes. We established a full control of heart rate and examined if such a control was useful for decreasing cardiac oxygen consumption. Based on a simulation result, we conducted an animal experiment. In 7 dogs with acute heart failure, we treated hemodynamics, and then lowered heart rate. Compared to the treatment for hemodynamics alone, the addition of bradycardia decreased cardiac oxygen consumption. It was possible to maintain hemodynamics without sacrificing cardiac oxygen consumption.

The pressure-volume relationship of the heart: past, present and future

The pressure-volume relationship of the heart was first reported more than a century ago. It was not widely accepted, however, until the mid-1970s. The pressure-volume diagram became a central theme of cardiac mechanics once it was shown to be a good representation of ventricular mechanics. Early in 1980s, the introduction of the ventricular interaction with afterload using effective arterial elastance made it possible to translate ventricular mechanical properties represented by the pressure-volume relationship to the pumping ability of the heart. Furthermore incorporating the framework of ventricular arterial interaction into the classic Guyton's circulatory equilibrium early in 2000s enabled us to express quantitatively how mechanical properties of the ventricles and vascular systems determine the circulatory equilibrium. Successful quantitative descriptions of circulatory equilibrium using the pressure-volume concept would promote basic cardiovascular physiology and accelerate its clinical applications.

Automated drug delivery system for the management of hemodynamics and cardiac energetic in acute heart failure

We have developed a novel automated drug delivery system for simultaneous control of systemic arterial pressure (AP), cardiac output (CO), and left atrial pressure (P(LA)) in acute heart failure. The circulatory equilibrium framework we established previously discloses that AP, CO, and P(LA) are determined by equilibrium of the mechanical properties of the circulation, i.e. pumping ability of the left heart, stressed blood volume and systemic arterial resistance. Our system directly controls the three mechanical properties with cardiovascular drugs including inotropes and vasodilators, thereby controlling AP, CO, and P(LA). Furthermore, by precisely controlling bradycardia and LV inotropy, our system enables to improve cardiac energetic efficiency while preserving AP, CO, and P(LA) within acceptable ranges. In conclusion, by directly controlling the mechanical properties of the heart and vessel, our automated system realizes comprehensive management of hemodynamics in acute heart failure.

Feedback control of multiple hemodynamic variables with multiple cardiovascular drugs

The ultimate goal of disease treatment is to control the biological system beyond the native regulation to combat pathological process. To maximize the advantage of drugs, we attempted to pharmacologically control the biological system at will, e.g., control multiple hemodynamic variables with multiple cardiovascular drugs. A comprehensive physiological cardiovascular model enabled us to evaluate cardiovascular properties (pump function, vascular resistance, and blood volume) and the feedback control of these properties. In 12 dogs, with dobutamine (5+/-3 mug.kg(-1).min(-1)), nitroprusside (4+/-2 mug.kg(-1).min(-1)), dextran (2+/-2 ml.kg(-1)), and furosemide (10 mg in one, 20 mg in one), rapid, sufficient and stable control of pump function, vascular resistance and blood volume resulted in similarly quick and stable control of blood pressure, cardiac output and left atrial pressure in 5+/-7, 7+/-5, and 12+/-10 minutes, respectively. These variables remained stable for 60 minutes (RMS 4+/-3 mmHg, 5+/-2 ml.min(-1).kg(-1), 0.8+/-0.6 mmHg, respectively).

Bionic cardiology: exploration into a wealth of controllable body parts in the cardiovascular system

Bionic cardiology is the medical science of exploring electronic control of the body, usually via the neural system. Mimicking or modifying biological regulation is a strategy used to combat diseases. Control of ventricular rate during atrial fibrillation by selective vagal stimulation, suppression of ischemia-related ventricular fibrillation by vagal stimulation, and reproduction of neurally commanded heart rate are some examples of bionic treatment for arrhythmia. Implantable radio-frequency-coupled on-demand carotid sinus stimulators succeeded in interrupting or preventing anginal attacks but were replaced later by coronary revascularization. Similar but fixed-intensity carotid sinus stimulators were used for hypertension but were also replaced by drugs. Recently, however, a self-powered implantable device has been reappraised for the treatment of drug-resistant hypertension. Closed-loop spinal cord stimulation has successfully treated severe orthostatic hypotension in a limited number of patients. Vagal nerve stimulation is effective in treating heart failure in animals, and a small-size clinical trial has just started. Simultaneous corrections of multiple hemodynamic abnormalities in an acute decompensated state are accomplished simply by quantifying fundamental cardiovascular parameters and controlling these parameters. Bionic cardiology will continue to promote the development of more sophisticated device-based therapies for otherwise untreatable diseases and will inspire more intricate applications in the twenty-first century.

Computationally managed bradycardia improved cardiac energetics while restoring normal hemodynamics in heart failure

In acute heart failure, systemic arterial pressure (AP), cardiac output (CO), and left atrial pressure (P (LA)) have to be controlled within acceptable ranges. Under this condition, cardiac energetic efficiency should also be improved. Theoretically, if heart rate (HR) is reduced while AP, CO, and P (LA) are maintained by preserving the functional slope of left ventricular (LV) Starling's curve (S (L)) with precisely increased LV end-systolic elastance (E (es)), it is possible to improve cardiac energetic efficiency and reduce LV oxygen consumption per minute (MVO (2)). We investigated whether this hemodynamics can be accomplished in acute heart failure using an automated hemodynamic regulator that we developed previously. In seven anesthetized dogs with acute heart failure (CO < 70 mL min(-1) kg(-1), P (LA) > 15 mmHg), the regulator simultaneously controlled S (L) with dobutamine, systemic vascular resistance with nitroprusside and stressed blood volume with dextran or furosemide, thereby controlling AP, CO, and P (LA). Normal hemodynamics were restored and maintained (CO; 88 +/- 3 mL min(-1) kg(-1), P (LA); 10.9 +/- 0.4 mmHg), even when zatebradine significantly reduced HR (-27 +/- 3%). Following HR reduction, E (es) increased (+34 +/- 14%), LV mechanical efficiency (stroke work/oxygen consumption) increased (+22 +/- 6%), and MVO (2) decreased (-17 +/- 4%) significantly. In conclusion, in a canine acute heart failure model, computationally managed bradycardia improved cardiac energetic efficiency while restoring normal hemodynamic conditions.

Comprehensive physiological cardiovascular model enables automatic correction of hemodynamics in patients with acute life-threatening heart failure

Saving life of patients with acute life-threatening heart failure is a major challenge. One has to correct several fatal hemodynamic abnormalities at the same time within a limited time frame. The formulation of such complicated treatments enables the development of a system that can be used to save automatically lives of patients with acute heart failure, an autopilot system. To accomplish this, we established a comprehensive physiological cardiovascular model, on which we based the design of the autopilot system. By translating hemodynamics into cardiovascular parameters (pumping ability, vascular resistance, blood volume), and by controlling each of these with individual drugs, we were able to correct blood pressure, cardiac output, and left atrial pressure to the target values rapidly (5.2 +/- 6.6, 6.8 +/- 4.6, and 11.7 +/- 9.8 minutes), stably, and simultaneously.