Regarding intravenous regional anaesthesia (Bier’s block), which ONE of the following statements is TRUE?
Answer: B: Prilocaine is the drug of choice for intravenous regional anaesthesia because it is the least toxic local anaesthetic agent. It can safely be given at a dose of 2.5 mg/kg (0.5 mL/kg of a 0.5% solution). Prilocaine should be injected slowly over 90 seconds. Lignocaine is an acceptable alternative to prilocaine. The standard dose of lignocaine is 3 mg/kg injected as a 0.5% solution (without adrenaline). A high success rate has also been achieved with a minidose of 1.5 mg/kg and is preferred by some clinicians.
The minimum tourniquet inflation time should be 20–30 minutes to prevent systemic toxicity. The maximum tourniquet inflation time should not exceed 60 minutes (some suggest 90 minutes).
Anaesthesia from a fingertip-to-elbow direction occurs irrespective of the site of anaesthetic infusion. Selecting an injection site near the site of pathology will provide more rapid anaesthesia at a lower dosage. There is some evidence that indicates that the procedure is more successful when the anaesthetic is injected distally.
References:
Femoral nerve blocks are performed for the management of pain in femoral shaft fractures.
Which ONE of the following statements is TRUE?
Answer: A: Femoral nerve blocks have proven effectiveness and low complication rates. It significantly decreases time to achieve lowest pain score as compared with intravenous narcotics, and patients have been found to require significantly lower doses of narcotics in conjunction.
When the blind technique is utilised, it is common practice to elicit paraesthesia to ensure the needle tip is in close proximity to the nerve. However, when paraesthesia is elicited, it is important that the needle must be withdrawn 1–2 mm before the anaesthetic is injected to prevent intraneural injection.
Peripheral nerve stimulators are commonly used by anaesthetists in performing peripheral nerve blocks to ensure consistent delivery of the anaesthetic to the immediate vicinity of the nerve. However, this practice is not common in the ED but neither is there any evidence to discourage this practice in the ED.
Advantages of using ultrasound in the ED to guide femoral nerve block include the ability to achieve a more complete block with less local anaesthetic and fewer vascular punctures. Detailed knowledge of the sonographic anatomy of the femoral nerve in the inguinal region is essential to be successful with this technique.
Regarding the use of opiods for the management of acute pain in the emergency department (ED), which ONE of the following is TRUE?
Answer: B: Opiods are frequently used in the ED for the relief of moderate to severe pain. However, it is frequently given in inadequate doses due to the concerns for precipitation of adverse events like respiratory depression. Contrary to the belief, <1% of patients who receive opiods will develop respiratory depression. Tolerance to this side effect develops simultaneously to tolerance to the analgesic effect. If the opiod dose is increased so that at least half the pain is relieved, the chance of respiratory depression is small. The risk of respiratory depression is increased when opiods are administered in conjunction with benzodiazepines, ethanol or other depressive drugs.
A typical adult dose of fentanyl for management of acute severe pain is 1–2 mcg/kg given intravenously. It has an onset of action within 1 minute, a peak effect at 2–5 minutes and a duration of 30–60 minutes. It does not possess any intrinsic anxiolytic or amnestic properties. Intranasal fentanyl has become popular for use especially in the paediatric population. Well-designed randomised controlled trials found that intranasal administration of fentanyl provides initial pain relief comparable to intravenous opiods and may even obviate the need for intravenous access. An initial dose of 1.5 mcg/kg is usually adequate. A second dose may be administered within 10 minutes of the first if necessary at a dose of 0.75–1.5 mcg/kg. If further analgesia is required after the second dose the patient should be reviewed and alternative or additional analgesia considered.
Traditionally, pethidine was preferred over morphine in the management of biliary colic as it was thought to have less of an effect on the sphincter of Oddi. However, its effect on the sphincter of Oddi is similar to morphine and there is no evidence to support the preferential use of pethidine in gall bladder or pancreatic disease. Pethidine has been removed from the Pharmaceutical Benefits Scheme and from a number of Australian hospitals because it has shown no advantage compared with other parenteral opioids, and has a number of significant disadvantages. Accumulation of the active metabolite, norpethidine can cause hyperexcitability, tremors, myoclonus and seizures, especially with repeated dosing or renal impairment. In addition, pethidine can cause serotonin syndrome when combined with other serotonergic medication and has a higher potential for abuse. It is now highly recommended that pethidine should be avoided.
Regarding agents used in procedural sedation and analgesia (PSA) in the ED, which ONE of the following statements is TRUE?
Answer: D: Midazolam has anxiolytic, sedative and amnestic effects but no analgesic activity. Paradoxal agitation has been reported with midazolam in 1–15% of patients and can be reversed with flumazenil. Propofol is frequently used for PSA in the ED. It has no analgesic activity, but it does have an excellent amnestic effect. There is strong supportive evidence that ketamine does not exhibit dosedependant adverse events within the range of clinically administered doses using standard administration techniques. Adverse effects of ketamine include vomiting, which typically occurs well into the recovery phase when the patient is alert and can clear the airway without assistance. The peak age for vomiting is early adolescence with lesser risk in younger and older children. Vomiting seems to be more frequent with the IM route compared with IV. Hypersalivation associated with ketamine use is rare and usually not clinically significant. Anticholinergic agents are not routinely recommended but can be used if clinically important hypersalivation occurs or for patients with impaired ability to mobilise secretions.
Regarding fasting and ED PSA, which ONE of the following is the MOST appropriate answer?
Answer: D: Depression and impairment of protective airway reflexes is a potential risk of PSA. The most significant potential risk associated with diminished airway reflexes is pulmonary aspiration. However, the risk of aspiration is low with PSA and fasting is just one consideration. Compared with general anaesthesia, PSA does not involve the use of volatile inhalational anaesthetics, which are particularly emetogenic, nor does it involve pharyngeal manipulation or instrumentation, again a potent stimulus for induced vomiting.
The tradition of fasting prior to a procedure is based on the intuitive recognition that vomiting and aspiration requires something in the gut. In ED PSA, fasting is not always practical, as patients are rarely fasted at the time of presentation and they present to the ED with injuries and illnesses requiring PSA that is rarely elective in nature. Additionally, there is insufficient evidence to support that prolonged fasting prior to sedation reduces the risk of vomiting and/or aspiration in both elective and emergency procedures. Despite this lack of evidence, most guidelines still recommend at least 2 hours and 6 hours from the last intake of fluid and food respectively to allow for gastric emptying. Similarly, there is insufficient evidence to associate fasting time, gastric volume or gastric acidity with the probability of aspiration during procedural sedation in both children and adults. There is also no evidence to support the frequently repeated supposition that gastric emptying is delayed by acute stress or anxiety.
Despite the low risk of aspiration and lack of evidence, it is prudent to err on the side of caution. Rather than just focusing on fasting times prior to PSA, emergency clinicians should aim to:
Click to expand