anesthetics, sedative-hypnotics, neuromuscular blocking agents and opioids. This approach seeks to utilize the most therapeutic properties of each drug while simultaneously reducing adverse effects as much as possible. The primary points of contact for physical therapists with general anesthetics is the inpatient hospital setting, and generally includes patients presenting post-surgery and/or during critical/intensive medical care. Patients who undergo orthopedic surgery, elective as well as traumatic, are regularly prescribed post-operative physical therapy. Current hospital practice standards have significantly reduced the period between surgical intervention and physical therapy evaluation. Therefore, physical therapists will treat patients who may present under relative influence of multi-modal general anesthesia. General functional concerns include decreased cardiac output due to decreased myocardial contractility, myocardial oxygen consumption and arterial pressure. In effect, patients presenting acutely post-operative require initial vital sign measurement to ensure hemodynamic stability and oxygen perfusion prior to progressive mobilization. The same can be said for patients receiving physical therapy in critical/intensive care units, though with additional respect to acute presentation of decreased consciousness, especially for patients receiving ventilatory pulmonary support. Medical management for this patient population often includes variable administration of general anesthetics, which can affect activity tolerance, participation and cognitive ability. Local anesthetics Similar respect should be paid to local anesthetics, which are commonly employed during orthopedic surgical intervention as an adjunct for post-operative pain control. The mechanism of action includes binding of drug molecules to voltage-gated sodium ion channels, which regulate neural signal conduction. These drugs are typically administered via injection to provide an acute analgesic block for sympathetic transmission afferent as well as efferent signals related to pain, temperature, light touch and motor output (Katzung, 2018, p. 466). Common local anesthetics include lidocaine, ropivacaine and chloroprocaine. Local anesthetics are commonly applied at the caudal subarachnoid space, which induces analgesia distributed generally below the neural level of injection. Physical therapists will commonly encounter inpatients who have received local pharmaceutical anesthesia via epidural injection for purpose of orthopedic surgeries as well as labor and delivery. Average elimination half-life of lidocaine is 1.6 hours for patients presenting without severe hepatic disease; lidocaine is the current reference standard for local anesthetics (Katzung, 2018). Patients who have received localized anesthesia for their lower extremities present concern for musculoskeletal instability, with associated risks of falls and/or lower extremity injury. Therefore, it is important that physical therapists practicing in hospital settings where orthopedic intervention is followed by progressive mobilization use a physical examination to determine when it is appropriate to advance post-operative patients toward lower-extremity weight-bearing positions. Lower extremity physical exam should include, but not be limited to, comparative measurement of knee extension and ankle dorsiflexion strength. Current efforts in the profession of clinical anesthesiology have gravitated toward local anesthetic precision to reduce required recovery periods following surgical intervention. Amendments in position during administration along with pharmaceutical choice may affect duration of somatosensory versus motor effects. Risks associated with receiving local epidural anesthesia include neural injury as well as chronic persistent transient neurologic symptoms. While etiology of the adverse effects is not well understood, current evidence does not report connection between clinical effect and toxicity. This is an additional area of concern for physical therapists, as patients may present to outpatient clinics following orthopedic surgical intervention with complaints of transient neurologic
pain, which inherently requires more of a pain science-based therapeutic approach. Muscle relaxants Muscle relaxants are most commonly applied either to induce controlled muscle paralysis during surgery and/or intensive/ critical care, or to diminish painful states of relative muscle spasticity. Muscle relaxants act by interrupting function of myelinated somatic nerves, unmyelinated motor nerve terminals, nicotinic acetylcholine receptors, the motor end plate, muscle membrane and intracellular muscle contractile system (Katzung, 2018, p. 475). Neuromuscular blocking pharmaceuticals, such as succinylcholine, vecuronium, cisatracurium and rocuronium, bind to acetylcholine receptors at the neuromuscular junction. These drugs may be applied alongside general anesthesia during surgical intervention to enhance muscular relaxation and reduce tetanic twitches, reduce pharyngeal and laryngeal muscle spasms during endotracheal tube placement, and improve ventilatory compliance during mechanical ventilation (Katzung, 2018, p. 485). Antispasmodic and spasmolytic drugs are applied in the presence of peripheral musculoskeletal pathologies as well as upper motor neuron lesions. These pharmaceuticals include benzodiazepines such as diazepam, botulinum toxin (Botox), baclofen, tizanidine and dantrolene. Physical therapists may encounter patients receiving muscle relaxants in cases of cerebral palsy, cerebral vascular accident, spinal cord injury and multiple sclerosis. Parkinsonism and movement disorder pharmacology Pathologic movements such as rigidity, bradykinesia, tremors, chorea, tics, athetosis and dystonia characterize general movement disorders. Though not well understood, the majority of movement disorders are relatively associated with dysfunction at or near the basal ganglia. Specifically, the etiology of Parkinsonism is associated with reduced dopaminergic production and activity in the basal ganglia. In turn, pharmacologic management of Parkinsonism revolves around supplying dopamine, most commonly in the form of Levodopa, a metabolic precursor with chemical characteristics suitable to cross the blood-brain-barrier, along with carbidopa, which decreases peripheral conversion of levodopa to dopamine. This pharmaceutical combination is known as sinemet . Common concerns associated with prolonged levodopa administration include adverse behavioral effects, “dopa”-dyskinesias of the face and distal extremities, and fluctuations in clinical response (Katzung, 2018, p. 497). Additional dopamine receptor agonists, monoamine oxidase and catechol-o-methyltransferase inhibitors, may enhance the effects and prolong dopaminergic presence and activity. Physical therapists commonly treat patients with Parkinsonism across the rehab spectrum, including acute hospital inpatient admissions, acute neurologic inpatient facility rehab, skilled nursing facility rehab, home health, and/or outpatient settings. Therefore, knowledge pertaining to the interaction between the aforementioned pharmaceuticals and pathological progression may allot the best plan of care with regards to improving functional movement. Additional movement disorders, such as Huntington’s disease, may present pathologic movements associated with overactivity in dopaminergic pathways. Huntington’s disease in particular may be pharmaceutically managed with combinations of beta- blockers, such as propranolol, benzodiazepines and antiepileptic drugs to reduce involuntary choreatic movements and associated dementia. Opioids Opioids are derivatives of opium. Morphine is the pure alkaloid form. Katzung et. al relate the name of this pharmaceutical to Morpheus, the Greek god of dreams (2018, p. 553). Opioids may be administered via oral, intramuscular and subcutaneous pathways. First-pass elimination is dependent upon method of administration. This class of narcotics induces analgesic effects by binding to protein receptors in the brain, spinal cord and possibly peripheral nerve endings, associated with
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