Neuro Resus

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**Neuro Resus**

Podcasts on topics relevant to intensive care medicine

Latest Episodes:

Debate: Who should care for GUCH? Aug 06, 2018

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Debate: Who should care for GUCH?

Presenters: Dr Susanna Price & Dr Peta Alexander. Moderator: Dr Bennett Sheridan

GUCH - A growing problem. Aug 06, 2018

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GUCH - A growing problem by Dr Susanna Price.

Congenital heart disease – Repair or Palliate? Aug 06, 2018

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Congenital Heart Disease (CHD) in infants presents as inadequate systemic or pulmonary blood flow, or heart failure from intra-cardiac shunts. Approaches to surgical intervention comprise primary repair, early palliation with subsequent repair or definitive palliation.

CHD palliation evolved in the pre-cardiopulmonary bypass era. In 1938 a patent ductus arteriosus was ligated, in 1944 pulmonary blood flow was established via subclavian artery to pulmonary artery anastomosis (Blalock, Taussig and Thomas), and in 1952 pulmonary artery banding was employed to protect pulmonary vasculature. In the 1950s-60s symptomatic infants underwent these palliative procedures with reparative intra-cardiac interventions delayed due to perceived risk. In the late 1960s emerging publications shifted the focus to early primary repair.

An exponential increase in the complexity of surgical repairs over the past 50 years have built on early innovation, exemplified by management of transposition of the great arteries. Surgical approach transitioned from palliative atrial switch procedures (Senning 1957 and Mustard 1963) with low early mortality but impressive late morbidity to the reparative arterial switch procedure (Jatene 1975) which remains standard of care.

Despite advances in the field, biventricular repair is not an option for all patients. Children born with a single functional left ventricle benefited from staged palliative procedures to the Fontan circulation. First described in 1971, the Fontan procedure established passive pulmonary blood flow, using the single ventricle for systemic circulation. Further innovation by Norwood (1981) facilitated similar staged palliation of patients with single right ventricles. While for most patients with functionally univentricular CHD, staged palliation is dictated by underlying anatomy, it is increasingly recognized that a proportion of these patients may have anatomy and physiology amenable to biventricular circulation.

As we embark on the next era of innovation in CHD, patient selection, multicenter collaboration and meaningful outcome measures are challenges to be addressed.

Inotrope therapy: Which one and when? Aug 06, 2018

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Inotropic agents are commonly used in critically ill patients to support myocardia contractility either in the setting of cardiac surgery or ischemia or in the setting of sepsis associated myocardial dysfunction. The most commonly used agents are beta-agonist drugs (dobutamine), mixed beta and alpha agents (adrenaline and dopamine), phosphodiesterase inhibitors (inodilators) such as milrinone or enoximone or calcium sensitizers (levosimendan). Such agents are currently used according to clinician and/or unit preference based on tradition, mentorship, belief, inductive physiological reasoning, familiarity, understanding of pharmacokinetic and pharmacodynamics properties, side effects, and cost. No randomized controlled trials exist to support the notion that treatment targeted to similar physiological outcomes (ie cardiac index or MVO2) with one drug versus another would yield a different clinical outcome. More recently, however, two double-blind RCTs have compared adjunctive inotropic therapy with levosimendan in patients with post-operative low-cardiac output syndrome or low pre-operative ejection fraction. Both found that the addition of levosimendan was not superior to the edition of placebo.

Principles of management of acute heart failure Aug 06, 2018

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Acute heart failure (AHF) is defined as rapid onset of new or worsening signs and symptoms of heart failure. It represents a life-threatening condition requiring treatment for fluid overload and hemodynamic compromise. Presentation may be initial diagnosis with symptoms and signs of AHF or acute decompensation of pre-existing cardiomyopathy. Hemodynamic instability results from disorders of the myocardium, valves, conduction system or pericardium, in isolation or combination. Potentially treatable causes, e.g. acute coronary syndromes, must be diagnosed and managed early for restoration of function.

Physiological changes associated with AHF result in reduced cardiac output and end-organ hypoperfusion. Once potentially treatable causes are managed, stratification of patients by clinical presentation guides further therapeutic intervention. AHF patients can be categorized as either 'wet' or 'dry' by clinical fluid status assessment, and either 'cold' or 'warm' according to perfusion status. In combination, these features identify four patient groups ('warm-wet', 'warm-dry', 'cold-dry', 'cold-wet') that guide therapy and facilitate prognostication. 'Warm-dry' patients rarely require intensive care for AHF treatment but may benefit from escalation of oral therapeutic regimen. Patients who examine as 'cold-dry' may benefit from fluid challenge, and/or inotropic agent infusion. 'Warm-wet' patients present with predominantly congestive or hypertensive symptoms which benefit from diuresis and vasodilatation. Patients who present 'wet-cold' with normal blood pressure (SBP >90) may benefit from vasodilators and diuretics, with inotropic agents for refractory symptoms. Hypotensive 'wet-cold' patients (classic cardiogenic shock) require inotropy with or without vasopressor agents, effective diuresis and early consideration of mechanical circulatory support (MCS).

Definitive therapies for AHF depend on underlying cause, and may include coronary artery intervention, valve repair, rhythm control to restore atrio-ventricular synchrony or management of pericardial tamponade. Patients with severe AHF not responsive to standard therapies should be considered for temporary MCS while candidacy for more durable option is explored by the multi-disciplinary team.

Heart failure in the 'non-cardiac' ICU patient Aug 06, 2018

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In non-cardiac ICU patients, the two major causes of acute myocardial dysfunction are sepsis-related cardiac depression (SRCD) and stress-related cardiomyopathy, the most common cause being the former. The main mechanisms responsible for SRCD include release of cardiac-depressant substances such as pro-inflammatory cytokines, hyporesponsiveness of beta-adrenergic receptors, decreased sensitivity of the myofilament to Ca++, and excessive production of perioxynitrite. Echocardiography is the best method to diagnose SRCD. If a cut-off value of 45% left ventricular ejection fraction is used to define SRCD, the occurrence of SRCD is 60% in septic shock patients (40% on the day of admission and in 20% the two following days). Recent advances in ultrasonography such as speckle-tracking (measuring the longitudinal systolic strain) may allow detecting cardiac abnormalities that are not detected by conventional echocardiography. Even when the SRCD is diagnosed, an important issue is to decide to treat it since left ventricular dilatation is an adaptive mechanism associated with a good outcome. The Surviving Sepsis Campaign suggests using dobutamine in patients who show evidence of persistent hypoperfusion despite adequate fluid loading and the use of vasopressor agents. In our opinion, it is more logical to give an inotrope when the shock state persists in the presence of: 1) proven SRCD with echocardiography and, 2) either low (mixed or central) venous blood oxygen saturation or increased veno-arterial carbon dioxide pressure gradient. Dobutamine is still recommended as the first-choice inotropic agent. Levosimendan is considered an alternative as it can restore the sensitivity of the cardiomyocyte myofilament to Ca++. Early administration of norepinephrine can not only increase blood pressure through an alpha1-adrenergic effect but also improve cardiac contractility through a beta1-adrenergic effect and/or an increase in the diastolic arterial pressure (i.e. the perfusion pressure of the left ventricle).

Pathophysiology of acute heart failure in ICU Aug 06, 2018

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Ventricular pump function is often compromised during critical illness and for a variety of reasons. The most common cause of a limited cardiac output in acutely ill patients is right ventricular (RV) dysfunction. Exacerbations of chronic obstructive lung disease or the use of high end-expiratory pressure sin acute lung injury to support arterial oxygenation can result in acute elevations of pulmonary arterial pressure impeding RV ejection, causing RV dilation, decreased left ventricular (LV) diastolic compliance. All these effects limit cardiac output and LV stroke volume. Importantly, the treatment is to sustain mean arterial pressure greater than pulmonary artery pressure to prevent RV ischemia and balance RV fluid status to avoid both over-distention (acute cor pulmonale) and under-filling. This delicate fluid balance is greatly facilitated by the immediate and repeated use of bedside echocardiography. Attempts to minimize lung over distention should be a primary focus of therapy. If one focuses only on the LV, these patients would be said to have a reversible form of diastolic dysfunction, in that LV ejection fraction would be normal but the LV not able to increase its end-diastolic volume without excess filling pressures promoting pulmonary edema. The second most common etiology of impaired heart functional reserve is chronic LV hypertrophy secondary to hypertension, wherein systemic afterload reduction is the primary treatment. Third, decreased systolic pump function is often seen in sepsis owing to reduced myocardial adrenergic responsiveness. However, this is often under-appreciated because of the usually co-existent peripheral vasodilation. In septic patients, measures aimed primarily to increase mean arterial pressure, such as the use of vasopressors often results in a decrease in cardiac output because the septic heart is not able to handle the increased load. Importantly, this form of systolic dysfunction is reversible once the sepsis state resolves, but may require inotropes during its height to sustain flow under pressure. Finally both chronic heart failure patients can also get sick and acute myocardial infarction will impair both diastolic and systolic function. Their treatments include reversing coronary ischemia, if present, afterload reduction and a balanced fluid response. A clear and logical approach to all critically ill patients is needed to quickly separate these diverse forms of heart failure from each other as they have markedly different therapies and clinical trajectories.

ANZ ICU experience Aug 06, 2018

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Over 65,000 people are diagnosed with heart failure every year in Australia. Heart failure is implicated in the deaths of 61,000 individuals per year. Although the need for cardiovascular support is common in patients in the Intensive Care Unit (ICU) with about 60% of ventilated patients requiring some form of inotropic or vasopressor support, a primary diagnosis of acute heart failure on admission to ICU is much less common. There are about 3000 ICU admissions per year primarily due to cardiogenic shock, cardiomyopathy or congestive heart failure in Australia and New Zealand. This represents 2% of all ICU admissions. Only a minority of these patients have a prior history of significant cardiac disease. The mortality of these three conditions are 40%, 17% and 14% respectively. Since the early 2000's there has been a progressive decline in risk adjusted mortality of all patients admitted to ANZ ICUs. However, the decline in mortality for patients with acute heart failure has lagged behind other diagnoses. This gap is widening.

Paediatric ICU Part 6: Traumatic Brain Injury Aug 01, 2018

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Shree Basu and Ahmed Osman discuss paediatric traumatic brain injury. They cover initial management, prevention of secondary injury, what is different in paediatrics compared to adults and the latest evidence.

From www.IntensiveCareNetwork.com

Making Complex Problems Simple by Chris Hicks Aug 01, 2018

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Resuscitation is complicated, but the solutions don't have to be. These are the psychological hacks that will help you conquer complexity and excel in dynamic environments.

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