Frequently, the college will put some sort of horrible LFT picture up for the candidates and ask them to make sense of it. The general trend of questions seems to be coma, flavoured with a recent history of discharge from an alcohol rehab institution of some sort. There is one specific question which is frequently repeated where the ammonia is also elevated, and the LFTs are raised in a non-specific pattern. Give six differentials, they usually ask.
Heart failure management is a massive daunting topic. In order to approach this in a systematic manner, I have separated the problems of heart failure into the variables which govern cardiac output, and the means of manipulating those variables. The approach resembles that of the similar chapter from the section on cardiothoracic intensive care. The definitive resource for this is probably this 2013 guideline statement by the AHA/ACC. Unless otherwise reported, it is my source for most of the information below. For the sane exam candidate who may be disinclined to read the entire fifty-page document, of particular interest may be Section 7.3.2, Pharmacological Treatment for Stage C HFrEF.
The liver has synthetic, metabolic and storage functions. Synthesis of most blood proteins, glucose and ketones occurs in the liver. It also has exocrine synthetic function (it produces bile). Metabolic function can be loosely grouped by scale; the liver metabolises macronutrients (carbohydrates lipids and proteins) as well as molecules present in smaller numbers (eg. drugs and toxins). It has a storage role (eg. ~20% of total body glycogen) and it participates in the immune system as Kupffer cells can act as antigen presenting cells.
This chapter is basically a set of long, enormously elaborate footnotes to the Wiggers Diagram, which describes the timing of pressure and volume changes in the chambers of the heart. In short, the cardiac cycle can be split into seven fairly predictable phases, each with their clearly defined boundaries, containing well described events which are a favourite of the CICM examiners.
The pulmonary circulation is a low pressure, highly elastic system, with vessel walls which are much thinner and less muscular than the systemic circuit. The pulmonary trunk divides into pulmonary arteries which can be divided into elastic (large), muscular (small) and nonmuscular (the smallest), though further subdivisions are histologically apparent. Pulmonary arteries and veins travel with bronchi, nerves and lymphatics in bronchovascular bundles, which are extensions of the visceral pleura. Pulmonary veins are thinner and more collagen-rich than pulmonary arteries. The bronchi are supplied by the systemic circulation which arises from the intercostal arteries on the right and from the aorta on the left.
The splanchnic circulation by definition consists of blood vessels which supply and drain the liver, spleen, stomach, pancreas, and the amall and large intestine. Owing to their low oxygen extraction ratio, these organs tend to have no need of blood flow autoregulation to support their metabolism, as they can just extract more oxygen instead. Thus, the splanchnic circulation mainly regulates its blood flow according to demands made by digestion, and after a meal intestinal blood flow can be up to 35% of the total cardiac output.
Class I antiarrhythmics are sodium channel blockers with local anaesthetic effect. They bind to open or inactivated sodium channels and can be classified into subclasses according to their dissociation kinetics and the effect they have on the shape of the cardiac action potential. Class Ib agents shorten the duration of the action potential, Class Ia agents increase its duration, and Class Ic agents have no effect on it. These agents exert their antiarrhythmic effect by slowing conduction, suppressing the excitability of ectopic pacemakers, and prolonging the repolarisation.
The point of these is to estimate the magnitude of the oxygen transfer deficit, and thus assess how well the lung is functioning as an oxygenator of pulmonary blood. Essentially, one is attempting to make an estimate of intrapulmonary shunt. However, these indices perform poorly in this role. In general it is fair to say that indices based on oxygen tension are popular because of simplicity, not validity. The best index of pulmonary oxygen transfer is still the measured intrapulmonary shunt.
Miraculous pale fluid, tincture of calm, friend to the swollen brain, the bringer of immediate improvement into any nurses' night shift. Propofol, 2,6 diisopropylphenol, is an extremely oily GABA agonist which completely replaced older dirtier agents when it appeared on the market in the late 1970s. Its only disadvantage is its tendency to completely switch off the sympathetic nervous system, with predictable haemodynamic consequences.
The biliary tree consists of a series of ducts, mostly lined with cholangiocytes, which extend from the liver to the duodenum (where they empty via the sphincter of Oddi). This tree has approximately 10 ramifications, ranging from the 1-2μm biliary canaliculi where bile is first secreted to the 4-7mm common bile duct. Cholangiocytes which line this system are an epithelial cell species responsible for the secretion and modification (concentration, alkalinisation) of bile.
Respiratory compliance is defined as the change in lung volume per unit change in transmural pressure gradient. It is usually about 100ml/cm H2O. Static compliance is defined as the change in lung volume per unit change in pressure in the absence of flow. Dynamic compliance is defined as the change in lung volume per unit change in pressure in the presence of flow. Specific compliance is lung compliance which is normalised to a lung volume or capacity, which permits comparison between lungs of different size.
The liver is an essential organ of mainly innate immunity. It secretes most of the complement proteins, and contains 80-90% of the total body tissue-bound macrophages (it is 15% Kupffer cells by weight). Sinusoidal endothelial cells and Kupffer cells filter antigens and microorganisms from portal venous and systemic blood. The liver also contains large amounts of dendritic antigen-presenting cells, as well as NK cells and T-cells.
The liver has a dual blood supply, receiving most of its blood flow (75%) as deoxygenated blood from the portal vein, and the rest from the hepatic artery. The portal vein is a low-pressure system of valveless vessels which does not autoregulate according to hepatic oxygen demand, but rather according to supply (eg. with meals, the portal vein dilates and increases its flow). The hepatic artery, apart from beign subject to normal arterial autoregulatory mechanisms, is also able to adjust its flow to compensate for changes in portal venous flow - a phenomenon known as the hepatic arterial buffer response.