Low cardiac output syndrome is a postoperative complication caused by reperfusion and ensuing oxidative stress to the pulmonary and cardiac tissues. This syndrome is important to consider for its association with high morbidity and mortality due to impaired cardiovascular function.
Low cardiac output syndrome (LCOS) is a reduction in cardiac output often seen in postoperative situations, especially those of coronary artery bypass grafting (CABG), and cardiopulmonary bypass (CPB)  . It happens on account of the oxidative stress caused by reperfusion after surgical manipulations. The oxidative stress, as well as inflammatory reactions, cause a disturbance of function in the myocardium resulting in a necessity of inotropic support . Pulmonary tissues also undergo reperfusion that participates in the development of vascular reactivity and damage to the alveoli causing pulmonary edema; the latter is responsible for poor tissue oxygenation .
There are no strict clinical criteria for diagnosing the patient with possible LCOS. Strong indications for LCOS is hemodynamic instability and impaired tissue oxygenation occurring postoperatively. Additionally, one of the essential pointers is the need for administration of afterload reduction agents or inotropic agents e.g. dobutamine, epinephrine, and dopamine in order to maintain sufficient cardiac function . Intra-aortic balloon counterpulsation support and positive pressure oxygenation are also important factors contributing to the diagnosis  .
On examination, the patient will reveal cold extremities, particularly in the most distal parts like toes, an absence of pedal pulse and a decrease in the systolic pressure measuring under 90 mmHg. Likewise, weakened perception of sensation may be noted . LCOS is considered to be associated with high risk of morbidity and mortality, thus prompt recognition and preservation of adequate circulation are of immense importance .
Entire Body System
Secondary postoperative outcomes investigated included myocardial injury, supraventricular arrhythmias, development of LCOS, acute kidney injury (AKI), duration of mechanical ventilation, intensive care unit and hospital lengths of stay, and incidence of hypotension [ncbi.nlm.nih.gov]
Etiology Syndrome ass. with CV instability and hypotension. • Sepsis ( Hypotension with ed SVR) • Anaphylactic reaction (blood products, drugs) • Adrenal insufficiency (primary or pt with preoperative steroids) • Protamine reaction 14. [slideshare.net]
Severe hypotension occurred in 57% of patients receiving levosimendan and 48% of those receiving placebo (P = .11). The management of hypotension was comparable between the 2 groups, except for the use of epinephrine. [jamanetwork.com]
- Refractory Shock
Hydrocortisone "stress dosing" is reported to provide hemodynamic benefits in some patients with refractory shock. [ncbi.nlm.nih.gov]
In such cases it is advisable to expand monitorization and to obtain information on the cardiac output of the patient: – Refractory shock: In patients who 3–6h after the start of treatment present signs of refractory shock, including persistent lactic [medintensiva.org]
- Orthostatic Hypotension
Hypotension - Seizure, mental status change, diaphoresis, and signs of orthostatic hypotension and shock. Low cardiac output - Fatigue, weakness, dyspnea on exertion, lethargy, and lightheadedness. [en.wikipedia.org]
Low cardiac output syndrome can be the cause of decreased tissue oxygenation and disturbance in the cardiovascular system. Parameters evaluating the dynamics of this syndrome are linked with measurements of the arterial blood gas, central venous pressure, blood pressure, and estimates of the cardiac output.
It is possible to assess cardiac output (CO) directly by thermodilution. This technique includes a placement of the pulmonary artery catheter and is considered a gold standard for measuring the CO. It also gives data of right ventricle activity, such as right ventricular ejection fraction and right ventricular end diastolic volume. Although there are some drawbacks to this method, firstly it is an invasive procedure and secondly, it is not meant for continuous measurement of the CO . There are other less invasive techniques for measuring the CO e.g. with transthoracic (TTE) or transesophageal (TEE) echocardiography.
LCOS is considered if the cardiac index (which is calculated with CO as a variable) is less than 2.2 L/min/m2, pulmonary artery occlusion pressure (PAOP) is more than 16 mmHg, and oxygen saturation drops to less than 60%  .
In the case of poor oxygenation caused by LCOS, serum lactate levels increase to more than 2 mmol/L for at least 2 hours and metabolic acidosis is recognized. Compensatory mechanisms will be exhibited by oliguria with urine output of less than 1.0 mL/kg/h .
Arterial blood gas analysis may uncover changes in partial arterial oxygen tension with less than 100 mmHg and partial arterial carbon dioxide tension of value exceeding the normal range of 35–45 mmHg. Central venous pressure is also likely to deviate from the norm of 6–8 mmHg  .
- Base Deficit
Arterial blood pressure, but MAP ~ CO x SVR Cardiac filling pressures: CVP 9-12 mmHg, MPAP < 1/3 MAP, LAP 9-15 mmHg in biventricular heart without shunt Peripheral perfusion (capillary refill time) Core – peripheral temperature difference Urine output Base [dontforgetthebubbles.com]
Serial ABG analysis reveal ↑ levels of base deficit and ↓ HCO3- levels Frank et al……………….metab acidosis with ↑ pH is a late feature of ↓ peripheral perfusion & care takers should not wait for this sign to diagnose LCOS ↑ in arterial lactate levels [slideshare.net]
There was metabolic acidosis (diagnosed by PH, base deficit and lactate level), in patients of both groups, but more in patients of group B than that of group A. [hoajonline.com]
This is detectable as a high lactate on blood gas measurement causing an acidosis or acidemia. § Lactate > 2mmol/L § Base deficit > -4 mmol/L correlates with inadequate tissue oxygenation and increased morbidity. · Impaired oxygen delivery also leads [cancertherapyadvisor.com]
These haemodynamic effects were maintained over the 48 h of treatment and persisted 3 h after discontinuation of treatment. [ncbi.nlm.nih.gov]
The treatment with alprostadil was continued until surgery to maintain patency of the PDA. [annals.in]
Milrinone, epinephrine, dopamine and dobutamine are mostly used, and should be prioritised for future research on LCOS treatment. [adc.bmj.com]
In this respect, the prognosis was clearly poorer among the patients with cardiogenic shock. Two relevant findings were made in our study: 1. [medintensiva.org]
The prognosis for people with heart failure and preserved LV ejection fraction is a little better than the prognosis for people with heart failure and reduced ejection fraction. Generally, the lower the ejection fraction, the poorer the prognosis. [patient.info]
In this type of surgery, prior cardiovascular status is extremely important for prognosis and the, considerably higher, perioperative mortality is the most important individual factor taken into account when evaluating the quality of surgical programs [revespcardiol.org]
英文摘要: Low cardiac output syndrome is a common complication after pediatric cardiac surgery, which has brought many adverse effects on the prognosis of patients. [xxgzz.com.cn]
Multifactorial in etiology, this article will discuss the pathophysiology of low cardiac output syndrome, including myocardial depression following bypass, altered cardiac loading conditions, and inflammation driving a hypermetabolic state. [scholars.northwestern.edu]
This article provides an overview of the determinants involved in oxygen transport, the physiologic factors influencing cardiovascular function, the assessment of hemodynamic variables, the etiology of LCOS, and management strategies, including a brief [unboundmedicine.com]
384) Neurology (250) Infectology (236) Surgery, Traumatology and Orthopaedics (228) Physiology and Pathophysiology (226) Medical Chemistry and Biochemistry (185) Microbiology (174) Genetics (136) Dermatology (131) Gastroenterology and Hepatology (115) Epidemiology [portal.mefanet.cz]
Although the symptoms, causes, prevalence, and epidemiology of the six different types of heart failure are somewhat different, there is substantial overlap, and types may coexist. [aafp.org]
Epidemiology The exact prevalence and incidence of LoHF in the general population is completely unknown. At present, there are no population-based epidemiological data specific to LoHF. [oatext.com]
Criteria abstracted from The Users' Guide to Medical Literature, from the Health Information Research Unit and Clinical Epidemiology and Biostatistics, McMaster University Highlighted lines and questions below provide links to the pertinent description [pedsccm.org]
Epidemiology [ 1, 3 ] Currently around 920,000 people in the UK have a diagnosis of heart failure. Prevalence in developed countries is approximately 1-2% of the adult population, increasing to 10% or more in those over 70 years of age. [patient.info]
TY - JOUR T1 - Pathophysiology of post-operative low cardiac output syndrome AU - Epting, Conrad L AU - McBride, Mary Eileen AU - Wald, Eric L AU - Costello, John M. [scholars.northwestern.edu]
Title: Pathophysiology of Post-Operative Low Cardiac Output Syndrome VOLUME: 14 ISSUE: 1 Author(s): Conrad L. Epting, Mary E. McBride, Eric L. Wald and John M. [eurekaselect.com]
Multifactorial in etiology, this article will discuss the pathophysiology of low cardiac output syndrome, including myocardial depression following bypass, altered cardiac loading conditions, and inflammation driving a hypermetabolic state. [ncbi.nlm.nih.gov]
The low cardiac output syndrome complicates 1 in 10 coronary bypass operations and is associated with a heightened risk of perioperative death.1 The pathophysiology of this syndrome is complex, with likely contributions from reperfusion injury, systemic [nejm.org]
Thus potentially, levosimendan is a beneficial alternative to standard medication for the prevention of low cardiac output syndrome in paediatric patients after open heart surgery. [ncbi.nlm.nih.gov]
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