Drugs
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The enantiomerically pure (S-enantiomer) amide local anaesthetic drug ropivacaine blocked nerve fibres responsible for transmission of pain (Aδ and fibres) more completely than those that control motor function (Aβ fibres) in in vitro studies. The drug shares the biphasic vascular effects common to the amide local anaesthetic drug class. In vitro studies indicate that ropivacaine is less cardiotoxic than equimolar concentrations of bupivacaine. Apart from one trial in women undergoing hysterectomy, clinical studies that compared the efficacy of different doses of epidurally administered ropivacaine in patients undergoing various surgical procedures did not reveal any consistent dose-related differences with respect to sensory blockade. However, motor blockade did become more intense as the dose of ropivacaine increased. Overall, direct comparisons show that epidural ropivacaine is less potent than epidural bupivacaine when the 2 drugs are administered at the same concentration. However, this difference is less marked in terms of sensory blockade than motor blockade. The greater degree of separation between motor and sensory blockade seen with ropivacaine relative to bupivacaine is more apparent at the lower end of the dosage scale. Nevertheless, higher doses of ropivacaine than bupivacaine are generally required to elicit equivalent anaesthetic effects. Ropivacaine has been shown to induce successful brachial plexus anaesthesia when given at a concentration of 5 mg/ml, but not 2.5 mg/ml, and was as effective as bupivacaine in comparative studies in this indication. Limited data indicate that continuous epidural infusion of ropivacaine post-operatively reduces postsurgical pain in a dose-related manner. Morphine consumption was also reduced. Higher doses of ropivacaine were significantly more effective than placebo. Similarly, ropivacaine controlled postsurgical pain when infiltrated directly into surgical wound sites (i.e. wound infiltration) and was as effective as bupivacaine, and more effective than placebo, in this regard. Adverse events associated with epidurally administered ropivacaine include hypotension, nausea, bradycardia, transient paraesthesia, back pain, urinary retention and fever. The drug appears to have an adverse event profile similar to that of bupivacaine. In animal studies, overdoses of ropivacaine were better tolerated than overdoses of bupivacaine but not lidocaine (lignocaine). Human volunteers tolerated a higher intravenous dosage of ropivacaine than bupivacaine before developing initial signs of toxicity. Thus, ropivacaine, according to animal data, is less cardiotoxic than bupivacaine. Based on available clinical data, ropivacaine appears to be as effective and well tolerated as bupivacaine when equianalgesic doses are compared. The greater degree of separation between motor and sensory blockade seen with ropivacaine relative to bupivacaine at lower concentrations (≈5 mg/ml) will be advantageous in certain applications. ⋯ Recommended epidural doses of ropivacaine for surgical anaesthesia range between 113 and 200mg. Different doses can be achieved by varying either the concentration or volume of solution injected. Epidural ropivacaine administered to control postsurgical pain can be given as a 20 to 40mg bolus with 20 to 30mg top-up doses at ≥30-minute intervals or as a 2 mg/ml continuous epidural infusion at a rate of 6 to 14 ml/h (lumbar) or 4 to 8 ml/h (thoracic).
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Cholera is a dramatic clinical illness that requires rapid diagnosis and aggressive therapy. Clinical signs and symptoms of mild, moderate and severe dehydration must be determined, before beginning fluid therapy. Fluid therapy has 2 phases: rehydration (first 3 to 4 hours to correct deficits) and maintenance (to match continuing losses). ⋯ For most patients with cholera, an ORS using one of the higher sodium-containing solutions and plain water optimally provide the fluid and salt needed. Close monitoring of intake, outputs and hydration status should be performed for all patients. Antimicrobial therapy should be given to moderately and severely ill patients in order to decrease the volume of fluids lost and to shorten the period of excretion of vibrios.
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Review Comparative Study
Opioid analgesics: comparative features and prescribing guidelines.
The term 'opioid' is a generic term for naturally occurring, semisynthetic and synthetic drugs which combine with opioid receptors to produce physiological effects and which are stereospecifically antagonised by naloxone. For clinical purposes, opioids can be classified according to their receptor interactions (agonist, partial agonist, agonist-antagonist and antagonist), the pain intensity for which they are conventionally used (moderate or severe), and their half-life (short or long). Pure agonists conventionally used for moderate pain, short and long half-life pure agonists conventionally used for severe pain, mixed agonist-antagonists and partial agonist opioids are described in detail. ⋯ The regimen for opioid medications should generally provide around-the-clock analgesia with provision for rescue doses for the management of exacerbations of the pain not covered by the regular dosage. At all times, uncontrolled pain should be addressed by gradual increase in the opioid dose until either pain control is achieved or intolerable and unmanageable adverse effects supervene. The management of pain with opioid analgesics demands frequent patient assessment and a readiness to re-evaluate the therapeutic plan in the setting of either inadequate relief or adverse effects.
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Premature and full-term neonates, infants and children are capable of experiencing pain just like adults, and deserve aggressive treatment. Assessment of pain is difficult in the preverbal group. However, physiological and behavioural responses to noxious stimuli are well developed even in the fetus, and modifying these responses through treatment can affect outcome. ⋯ Drug dependence and withdrawal can be avoided by using the opioids appropriately and following logical weaning schedules after long term use of these agents. Use of needles for administering analgesia is still an intimidating part of the process for young children. The development of drugs having fewer adverse effects and noninvasive administration techniques will be important research priorities in the future.
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Review Comparative Study
Sevoflurane. A review of its pharmacodynamic and pharmacokinetic properties and its clinical use in general anaesthesia.
Sevoflurane is an ether inhalation general anaesthetic agent with lower solubility in blood than isoflurane or halothane but not desflurane. The low solubility and the absence of pungency facilitate rapid mask induction; the low blood solubility also expedites "wash-out' and therefore recovery from anaesthesia. Sevoflurane produces dose-dependent CNS, cardiovascular and respiratory depressant effects that generally parallel those of isoflurane. ⋯ In summary, sevoflurane provides for a rapid and smooth induction of, and recovery from, anaesthesia. These features combined with its favourable cardiovascular profile should make sevoflurane the agent of choice for inhalation induction in adult and paediatric anaesthesia. Although further clinical evaluation will define the role of this agent relative to that of propofol and desflurane, sevoflurane should also prove to be a valuable alternative anaesthetic agent for adults in both outpatient and inpatient surgery.