Muscle tissue is classified into striated (skeletal and cardiac) vs smooth muscle tissue according to the arrangement of the contractile proteins, or lack thereof. Striated muscle organises actin and myosin into sarcomeres where these proteins are regularly spaced, whereas in smooth muscle these elements are organised into a more flexible arrangement that favours a larger range of possible lengths.
APRV has never come up in the CICM exams, and may never come up, because it would be unfair to test the candidates on something even the examiners themselves have little understanding of. It is a promising but poorly researched strategy that maximises alveolar recruitment and embodies the main principles of open-lung ventilation for ARDS.
The power of ventilation is defined as the work over time, and is normally 2-3 J/min. All other lung-protective strategies (low tidal volumes, low driving pressures) are ultimately all aspects of the same equation, i.e. all these strategies converge in their aim to reduce the power of mechanical ventilation
Dialysis for the severely hyponatremic patient can be a) avoided, b) delayed, c) underdosed, or d) performed with a "hacked" set of dialysate bags which have been altered to contain a lower concentration of sodium. Another option, which is easier and less satisfying, is to administer free water systemically in the form of 5% dextrose.
Dialysis disequilibrium syndrome is cerebral oedema resulting from the rapid removal of urea, and the resulting osmotic movement of water into CNS tissue. It has clinical manifestation similar to other forms of cerebral oedema and is treated in the same way (eg. with osmotherapy). Slower gentler dialysis is the most important preventative measure.
Body water content is regulated mainly by vasopressin. Circumventricular organs sense tiny (<3 mOsm/kg) changes in tonicity and modulate the release of vasopressin from the posterior pituitary, which results in the increased or decreased expression of aquaporins at the cortical collecting duct, where water is reabsorbed. This way urinary concentration mechanisms can be used to modify the loss of body water. The same hypothalamic control centre activates the sensation of thirst and affects behaviour to increase water intake.
Vasopressin is a nonapeptide, and its analogues are various modifications of that same basic molecular structure, used to change the pharmacokinetics and receptor selectivity of the end product. Terlipressin is a prodrug for lysine vasopressin which has a higher selectivity for V1 receptors, making it an almost pure vasopressor, and desmopressin (DDAVP) has a higher selectivity for V2 receptors, making it a more pure antidiuretic.
Numerous chemically diverse classes of oral hypoglycemic agents with various mechanisms of action exist, including biguanides, sulfonylureas, α-glucosidase inhibitors, meglitinides, thiazolidinediones, DPP-4 inhibitors, and SGLT-2 blockers. Unsurprisingly, for the majority of these (with some exceptions), hypoglycaemia is the most clinically important adverse effect.
Regular human insulin (eg. Actrapid) is an exact duplicate analog of the human peptide hormone, consisting of 51 amino acids. Other insulin variants modify the normal molecule to adjust the self-association behaviour of the drug, leading to longer or shorter absorption from the subcutaneous depot.
Calcium homeostasis is regulated by three main hormones: parathyroid hormone (PTH), calcitriol, and calcitonin. PTH and calcitriol work to increase plasma calcium by increasing its absorption from the intestine and bone, and by resisting its loss in the renal tubule. Calcitonin, on the other hand, defends against hypercalcemia by inhibiting bone resorption and encouraging renal elimination.
Adrenal hormones include cortisol, aldosterone, androgens, and catecholamines. Each hormone is secreted from structurally and functionally distinct zones of the adrenal gland. The synthesis of steroid hormones occurs on demand in the adrenal cortex, whereas catecholamines are constantly being synthesised and stored in chromaffin granules inside cells of the adrenal medulla. The stimuli for their release can be broadly summarised as "stress".
Corticosteroids have numerous effects, some often described as "adverse", but their undeniable safety needs to be highlighted, as there are very few endogenous substances for which, following the administration of an exogenous dose one hundred times the normal level, nothing serious happens.
Different corticosteroid drugs tend to be used for different conditions because of some peculiarities in their pharmacokinetics and pharmacodynamics. For example, methylprednisolone penetrates best into the lung, whereas dexamethasone can cross the blood-brain barrier more easily mainly because it is less protein-bound. These differences in pharmacology dictate the specific use case scenarios for corticosteroids.