Crystalloids are simple solutions that can increase fluid volume and are employed for patients presenting with dehydration and possible physiologic shock (Watkins, 2013, p. 183). Medications administered through intravenous lines are allotted via infusion, piggyback line or intravenous push. Infusion may be gravity assisted, with the medication bag hung above the patient’s heart. Medications are commonly infused via rate- controlled infusion pump; additional technology allows for infusion pumps to regulate the infusion rate as well as infusion pressure. Under certain circumstances, analgesic medication may be administered via patient-controlled analgesia (PCA) pumps, which allow for patients to induce medication release by pressing a control button. PCA pumps are highly regulated, with release parameters preset by the prescribing physician (Watkins, 2013, p. 183). A piggyback solution consists of a series of IV bag and tube branches connected to a primary line. This formation facilitates administration of multiple medications over short durations and is commonly used when medications are prescribed for To review : The nervous system is divided and categorized in terms of location and function . The central nervous system (CNS) includes the brain and spinal cord, while the peripheral nervous system (PNS) includes spinal nerves and other neuronal tissues outside of the CNS. In addition, the autonomic nervous system functions to operate and incorporate visceral physiologic functions such as cardiac output and blood flow distribution. The somatic nervous system consists of PNS structures that create voluntary movement, respiration and posture (Katzung, 2018, p. 89). The nervous system also includes influx and efflux of chemical and electric signals, termed afferent and efferent inputs. Chemical transmission occurs between nerve cells, and between nerve cells and target cells. Autonomic activity can be stratified as central (occurring primarily in the midbrain and medulla), cardiovascular, presynaptic and postsynaptic. The autonomic nervous system (ANS) is composed of two divisions: The sympathetic/thoracolumbar division, and the parasympathetic/craniosacral division. The sympathetic division consists primarily of short paravertebral chains and longer prevertebral ganglia, and is associated with physiologic processes of energy-expenditure. This is the derivation of the common phrase “fight or flight” response. The majority of post- ganglionic parasympathetic fibers innervate target tissues in the form of grids within target organs. For example, the enteric nervous system lies within the gastrointestinal system, and includes more than 150 million neurons innervating the region from the esophagus to the distal colon (Katzung, 2018, p. 91). The enteric nervous system is involved with control of motor and secretion actions within the gastrointestinal tract, as well as motor control of the colon. This design and distribution mediates energy-conserving physiology. Early scientific description of these processes used the word trophotropic, meaning “energy growth” (Katzung, 2018, p. 100). Current parasympathetic analogy includes the phrase “rest and digest.” While the chief autonomic transmitter molecules are acetylcholine and norepinephrine, many other neurochemicals are released and regulated within the ANS. Cholinergic fibers are ANS fibers that release acetylcholine. Nearly all the efferent nerve fibers departing from the CNS are cholinergic, including somatic fibers innervating skeletal muscle. In addition, the majority of parasympathetic postganglionic fibers are also cholinergic. Acetylcholine is synthesized and stored in large “quanta” capacity, often 1,000 to 50,000 molecules, in the nerve ending. This magnitude of formation and storage facilitates rapid transmitter release (Katzung, 2018, p. 95). Release of acetylcholine depends on calcium concentrations outside the cell. Action potentials trigger calcium influx along with efflux of acetylcholine and other neurotransmitters. A single depolarization can release hundreds
use multiple times per day alongside IV solutions. An IV push denotes instant delivery of a limited amount of medication by way of attaching a syringe to the distal IV port. IV push must be administered slowly in order to reduce opportunities for venous irritation. Total parenteral nutrition (TPN) is an IV nutrition solution consisting of fluid, electrolytes, fats, proteins and vitamins. TPN administration is indicated in the presence of severe malnutrition, significant weight loss, inadequate tolerance of enteral nutritional application, bowel obstruction and insufficient gastrointestinal absorption. Complications from intravenous administration may include infiltration, thrombus/phlebitis, air emboli and vein irritation. Infiltration means an IV catheter has become displaced from the intended vein, allowing the IV fluid into the surrounding tissue. A blood clot or venous inflammation can result from needle or catheter trauma, irritating medications, or insufficient vein size for the volume of medication required. Sign of inflammation at the IV site may indicate the presence of a thrombus, phlebitis or infiltration of particulate matter (Watkins, 2013, p. 195).
AUTONOMIC DRUGS
of quanta into the synaptic cleft. Acetylcholine receptors are currently termed cholinoreceptors , an update and departure from previous names such as muscarinic and nicotinic receptors. A common pharmaceutical that blocks the release process is botulinum toxin (Botox). Following release, acetylcholine molecules bind to cholinoreceptors to produce mechanism of action. The enzyme acetylcholinesterase then breaks down acetylcholine en masse. Norepinephrine , also known as noradrenaline , is released along with dopamine by the most postganglionic sympathetic fibers; these fibers are termed adrenergic fibers . Adrenergic release is similarly induced by calcium influx during action potentials. Adrenergic receptors are commonly termed adrenoceptors and are categorized based on agonist and/or antagonist selectivity. Norepinephrine transporter proteins are responsible for uptake and reuptake of the neurochemical, which effectively terminates synaptic activity. Cocaine and certain anti-depressant drugs can block this neurochemical transporter, which leads to increased neurotransmitter activity (Katzung, 2018, p. 95). Drugs such as amphetamines and ephedrine act as sympathomimetics; they act as weak agonists and substrates for monoamine transporters. These drugs are thus taken up into the synaptic cleft, which in turn displaced norepinephrine, causing it to be ejected into synaptic space, and increasing neurotransmitter activity. Despite the upgrade in receptor nomenclature, cholinergic receptor categorization re-emerges when considering pharmaceuticals. Muscarinic and nicotinic receptors denote specifics regarding chemical affinities. Muscarinic receptors derive the name from the chemical alkaloid muscarine, which demonstrated effects that mimic parasympathetic nerve discharge. Therefore, pharmaceuticals that bind to muscarinic receptors are termed parasympathomimetic . Muscarinic receptors are primarily located at effector cells, including smooth muscles and glands. In contrast, nicotinic receptors are located along autonomic ganglia as well as skeletal muscle neuromuscular junctions. Drugs that mimic the effects of acetylcholine are termed cholinomimetics . These medications either activate cholinoreceptors or inhibit break down of acetylcholine by blocking acetylcholinesterase. Cholinomimetic agents fasten to and stimulate muscarinic or nicotinic receptors (Katzung, 2018, p. 109). As mentioned previously in this section, the majority of post-ganglionic fibers are cholinergic. In turn, the effects of cholinomimetic drugs primarily stimulate parasympathetic effects for the nervous system and various organs, which follow: ● Eyes : Contraction of the iris and ciliary muscles; enacting near vision. ● Heart : Sinoatrial and atrioventricular nodes.
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