Anaesthesia Flashcards by Anita Smith

Q

Regarding adrenaline and selective Beta-1 blockers

Injecting adrenaline in the presence of a selective Beta-1 blocker causes hypertension

A

False

Injecting adrenaline in the presence of a selective Beta-1 blocker causes hypertension
F; in nonselective b-blockers e.g. propranolol, no issue with selective b-blocker e.g. metoprolol p80

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Q

Regarding adrenaline and selective Beta-1 blockers

Selective beta1-blockers and epinephrine can lead to malignant hypertension

A

F

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Q

Regarding Hypertensive Emergencies:

Defined as BP >180mmHg without end organ damage

A

https://bestpractice.bmj.com/topics/en-gb/27
Hypertensive emergency is severely elevated blood pressure (BP) associated with new or progressive target organ dysfunction.

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Q

Clonidine

lowers BP through its alpha agonist effect

A

T
centrally acing agonist at alpha2 adrenoreceptor and imidazole receptor

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Q

RE: Clonidine

Reduces analgesia requirement after surgery

A

T

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Q

Re: Clonidine

Reduces heart rate

A

True
(also listed as adverse effect in AMH)

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Q

re: clonidine

Contraindicated if SBP >180mmHg

A

False

FALSE used for high BP; It should be avoided in patients with a preoperative systolic pressure <100 mmHg or pulse rate <60/min

AMH: contraindicated in severe bradycardia due to sick sinus syndrome or heart block - contraindicated

precautions: conditions that may be worsened by bradycardia or hypotension, raynauds phenonmenon or other vasospastic peripheral vascular disease, depression (may exacerbate), diabetes (may cause transient rise in BSL)

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Q

Re: clonidine

Has an anti-anxiolytic effect

A

True

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Q

Re: clonidine

Clonidine works faster than midazolam

A

False

P229 - If anxiolysis is significant, oral midazolam 5–10 mg will provide rapid anxiolysis within 20 min and has no hemodynamic benefits

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Q

Which of the following is true of Vasovagal reactions

Diaphoresis

A

T

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Q

Which of the following is true of Vasovagal reactions

Tachycardia

A

false - low BP, low HR

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Q

Which of the following is true of Vasovagal reactions

Hypotension

A

T

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Q

Which of the following is true of Vasovagal reactions

Flushing

A

F
seen in adrenaline toxicity, allergic reaction

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Q

Which of the following is true of Vasovagal reactions

Perioral paraesthesia

A

false; lignocaine tox

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Q

Which of the following is true of Vasovagal reactions

Nausea

A

T, note; also in lignocaine tox

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Q

With regard to Anaphylaxis:

The dose of adrenaline given is based on the initial assessment of severity

A

F
standard dose 0.3-0.5mg

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Q

Regarding analgesia:

Codeine works longer if you have liver impairment

A

T
Codeine works longer if you have liver impairment
AMH – hepatic: for codeine – dose adjustment may be required in hepatic impairment, reduce dose and titrate carefully in severe hepatic disease

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Q

Regarding analgesia:

Paracetamol is contraindicated in severe liver impairment

A

T
Paracetamol is contraindicated in severe liver impairment
AMH: patients with chronic liver disease may be at increased risk of liver damage following therapeutic dose or overdose of paracetamol, but evidence is lacking

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Q

Regarding analgesia:

Endone is contraindicated in severe renal impairment

A

False

AMH: although renal impairment does not result in significant accumulation of active metabolites, the concentration of oxycodone may increase. Reduce initial dose if CrCl <30ml/min
For opioids in general and renal (AMH):
Because active/toxic metabolites accumulate in renal impairment, avoid use of codeine and pethidine; use lower doses of hydromorphone, morphine and tramadol with extreme caution. Alternatively, use an opioid such as oxycodone or tapentadol (both with appropriate dose adjustment) or fentanyl.

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Q

Which of the following is under the maximum recommended anaesthetic limits for a 70kg person?

30mL 2% lignocaine without adrenaline

A

F = 600mg lignocaine, exceeds

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Q

Which of the following is under the maximum recommended anaesthetic limits for a 70kg person?
b) 50mL 1% lignocaine with adrenaline

A

F = 500mg lignocaine, exceeds

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Q

Which of the following is under the maximum recommended anaesthetic limits for a 70kg person?
c) 80mL of 0.5% lignocaine without adrenaline

A

F = 400mg, exceeds

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Q

Which of the following is under the maximum recommended anaesthetic limits for a 70kg person?
Bupivicaine 0.5% 50mL without adrenaline F = 250mg, exceeds

A

F = 250mg, exceeds

Max bupivacaine without adr is 2.5mg/kg, with adr is 3mg/kg

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Q

Which of the following is under the maximum recommended anaesthetic limits for a 70kg person?
Ropivacaine 0.5% 50mL without adrenaline

A

F = 250mg, exceeds
Max ropivacaine 3.5mg/kg without adr, undefined for with adr

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# (2019) Tumescent anaesthesia a) Base is normal saline

T

# (2019) Tumescent anaesthesia b) Sodium bicarbonate is NOT added

False

# (2019) Tumescent anaesthesia Max lignocaine concentration is 4-5mg/kg

False safe upper limit of lidocaine dosage with this technique is estimated to be 55 mg/kg – p51 Liposuction chapter - conservative dosage guideline for a maximum lidocaine dose in tumescent local anesthesia is 35–45 mg/kg

# (2019) Tumescent anaesthesia 50ml/min is the appropriate rate

False The infiltration rate should be less than 100 mL/min to minimize patient discomfort. – p452 in liposuction chapter

# (2019) Tumescent anaesthesia The thigh is more sensitive to the back, therefore you should use a lower conc of lignocaine

F less sens, use lower conc P57 - For instance, liposuction of fibrous areas, such as the back, upper abdomen, and breasts, tends to require higher concentrations of lidocaine (1000-1250 mg/dL). As these areas tend to be associated with increased bleeding, they also benefit from higher concentrations of epinephrine (1 mg/dL). In contrast, less fibrous areas, such as the hips and thighs, may not require concentrations beyond 500-700 mg/dL of lidocaine and 0.5-0.65 mg/dL of epinephrine.

How do you locate and block the posterior tibial nerve?

At the ankle, the posterior tibial nerve passes posterior to the posterior tibial artery between the calcaneal tendon and the medial malleolus and travels distally deep to the flexor reticulatum. The posterior tibial nerve can be accessed with the patient supine and with the foot extended and externally rotated. A needle is placed at the level of the upper half of the medial malleolus, posterior to the posterior tibial artery pulse and anterior to the calcaneal tendon. The needle is advanced toward the posterior tibia, withdrawn slightly, and 3–4 mL of anesthetic is injected

How do you locate, and block the sural nerve? What nerve is it a branch of?

The sural nerve, arising from branches of the common saphenous and tibial nerves, passes more superficially between the Achilles tendon and the lateral malleolus as it travels toward the lateral border of the foot. The sural nerve block is performed with the patient prone. A needle is inserted 1–1.5 cm distal to the tip of the lateral malleolus and 3–5 mL of anesthetic is injected.

How do you block the saphenous nerve?

The saphenous nerve, a terminal branch of the femoral nerve, runs along the medial surface of the calf, passes subcutaneously anterior to the medial malleolus, and extends toward the medial surface of the foot. Injecting 3–4 mL of anesthetic into the subcutaneous tissue medial to the saphenous vein and anterior to the medial malleolus blocks the saphenous nerve

How do you block the superficial peroneal nerve?

The superficial peroneal nerve, a branch of the common peroneal nerve, travels along the anterolateral border of the calf. It arises subcutaneously above the ankle where it divides into its branches, the intermediate and medial dorsal cutaneous nerves, before entering the foot. Blocking the superficial peroneal nerve by injecting 3–4 mL of anesthetic into the subcutaneous tissue midway between the anterior tibial surface and the lateral malleolus provides anesthesia to a major surface of the dorsal foot

What nerve supplies the 1st webspace of the foot?

The deep peroneal nerve supplies a small portion of the foot, the first web space. The deep peroneal nerve block is rarely necessary in cutaneous surgery because anesthesia to this area can be adequately achieved by local infiltration.

What nerves supply the plantar surface of the foot?

The posterior tibial nerve innervates the plantar surface except for small areas on the lateral and medial aspects, which are supplied by the sural and saphenous nerves, respectively.

What nerves innervate the dorsum of the foot?

The superficial peroneal, sural, saphenous, and deep peroneal nerves innervate the dorsum of the foot.

To achieve a peripheral nerve block of the feet requires that the particular nerve trunks be accessed at the level of the ankle. Blocking all five nerves can be performed with the patient supine and the foot placed on a padded support; however, some prefer to block the posterior tibial and sural nerves with the patient prone.

T

The concentration of lidocaine and epinephrine can be varied depending on the clinical requirements. For instance, liposuction of fibrous areas, such as the back, upper abdomen, and breasts, tends to require higher concentrations of lidocaine (1000–1250 mg/dL). As these areas tend to be associated with increased bleeding, they also benefit from higher concentrations of epinephrine (1 mg/dL). In contrast, less fibrous areas, such as the hips and thighs, may not require concentrations beyond 500–700 mg/dL of lidocaine and 0.5–0.65 mg/dL of epinephrine.

T

To properly tumesce the neck, the patient is placed in the supine position and sterilely prepped and draped. The patient's neck should be slightly hyperextended for proper visualization and smooth infiltration. Small 3 mm slit incisions are made in the submental crease directly below the chin and 2 cm below the earlobes in the lateral neck at the anterior border of the sternocleidomastoid muscle. Infiltration of the areas can be performed with a blunt 18G cannula or spinal needle inserted into the slits. Dilute, tumescent anesthetic is slowly pumped into the area by an electronic pump. The cannula or needle should be gently advanced across the area to be anesthetized while staying superficial to the level of the platysma muscle. To ensure complete anesthesia, tumescence should be achieved slightly beyond the treatment area. Most cases require 250–400 cc of anesthesia for the entire neck area depending on the size and amount of fat to be removed. The area should be firm to the touch, indicating complete tumescence and anesthesia.

T

To prevent digital injury associated with local anesthesia: block at the level of the metacarpal heads

T

Prevention of allergic reactions to lidocaine: use preservative-free solution if paraben allergy present

T

use alternative agents when true lidocaine allergy noted: amide anesthetic, benzyl alcohol, diphenhydramine, or normal saline (the anesthetic effect of 0.9% saline results from tissue distention and pressure on nerve endings as well as the presence of benzyl alcohol preservative)

T

# To prevent f methemoglobinemia associated with local anesthesia * adhere to recommended anesthetic dosages * avoid using prilocaine and benzocaine in patients with risk factors: age <3 months; hereditary methemoglobinemia; glucose-6-phosphate dehydrogenase deficiency; concomitant oxidant drugs such as dapsone, nitroglycerin, nitrites, nitrates, phenacetin, primaquine, sulfonamides.

T

Allergic reactions to local amide anesthetics are rare. Although idiosyncratic systemic toxicity can occur at low plasma levels of local anesthetics, most systemic signs of toxicity are present at increased plasma levels. Systemic toxicity due to local anesthetics primarily affects the central nervous and cardiovascular systems. Methemoglobinemia can occur particularly in predisposed individuals.

T

Local injections of phentolamine 0.5 mg/mL and topical application of nitroglycerin have been used to reverse epinephrine-induced digital vasospasm. Phentolamine is an α-adrenergic blocker that competitively blocks both presynaptic (α-2) and postsynaptic (α-1) receptors, producing vasodilatation and a decrease in peripheral resistance. It is available in a 5 mg powder and can be diluted in normal saline

T

Patients with hypertension, peripheral vascular disease, and vasospastic disease are at increased risk. For this reason, it is generally recommended to avoid local anesthetic infiltration of epinephrine-containing solutions to the fingers and toes. Digital ischemia can also occur after ring blocks and injection of excessive volumes of anesthesia even without the addition of epinephrine

T

Paresthesias due to nerve injury can occur, particularly with peripheral nerve blocks. Nerve injury may result from transection of the nerve, pressure-induced ischemic injury with intraneural injection, vascular compromise by injury to local vasculature, or direct toxicity of injected agents. Acute pain or paresthesias on injection of local anesthetic can signify intraneural injection and should be avoided.

T

Inadvertent thermal and chemical burns have been associated with the use of local anesthetics. To allow for adequate penetration, EMLA is formulated in an alkaline vehicle with a pH of approximately 9.4. Alkaline chemical injuries to the eye have been reported with the use of EMLA near the eyes. These manifest as corneal abrasions and ulcerations and require immediate ophthalmologic evaluation and management.

T

Psychogenic attacks, which frequently manifest as vasovagal episodes, occur as a result of patients' response to anxiety, fear of needles, and/or pain of injection. Increased parasympathetic tone caused by the stress of injection leads to lightheadedness, diaphoresis, nausea, syncope, bradycardia, and hypotension.

T

Symptoms of flushing, palpitations, and malaise related to the adrenergic effects of epinephrine may be mistaken for an allergic reaction. Although tachycardia is typically present in both an epinephrine reaction and an anaphylactic reaction, blood pressure tends to be elevated with the former and decreased during anaphylaxis.

T

aution should be taken in using epinephrine in patients taking tricyclic antidepressants and β-blockers. The interaction of tricyclic antidepressants and epinephrine may lead to hypertension, tachycardia, and arrythmias.

T

Injection of epinephrine-containing anesthetic has been reported to cause hypertension followed by bradycardia in patients taking propanolol. This is likely a result of unopposed α-adrenergic vasoconstriction. Epinephrine should be avoided in patients with hyperthyroidism, severe hypertension, and pheochromocytoma.

T

Several reports of allergic reactions, ranging from contact dermatitis to anaphylaxis, have been described. Allergic reactions occur more commonly with ester derivatives than amides

T

Allergic reactions occur more commonly with ester derivatives than amides. Esters are metabolized to PABA, which is a potential allergen. Cross-reactivity may occur among ester-type anesthetics, paraphenylenediamine hair dyes, sulfonylureas, and thiazides

T

There is no cross-reactivity between esters and amide anesthetics. Methylparaben, an allergen chemically related to PABA, is a preservative added to anesthetics. Reactions to lidocaine may be due to these preservatives and not to the anesthetic itself

T

Although uncommon, delayed-type hypersensitivity from the topical use of ester and amide anesthetics has been reported. Multiple exposures to increasingly popular over-the-counter products containing lidocaine may contribute to topical sensitization to lidocaine.

T

There are no specific recommendations on the most reliable method of testing for suspected allergy to anesthetics. 34 The possibility of reaction to preservatives should be considered. If there is a clear history of procaine or PABA sensitivity, the use of preservative-free lidocaine is recommended. 34 The use of patch testing and intradermal skin testing with preservative-free lidocaine has been suggested as a rational approach.

T

An alternative in dealing with anesthetic allergy is the use of other agents for local anesthesia. Benzyl alcohol 0.9%, diphenhydramine 1%, and 0.9% saline (which contains benzyl alcohol) have been used to provide anesthesia for minor cutaneous procedures. However, the depth and duration of anesthesia have been shown to be less with diphenhydramine and benzyl alcohol compared to lidocaine. In addition, diphenhydramine induced more pain than lidocaine, caused skin necrosis in one patient, and can potentially be sedating. Intradermal tramadol and metoclopramide have also been shown to have local anesthetic properties

T

Intradermal tramadol 5% provided loss of sensation to pinprick, cold, and light touch 30 min after intradermal injection. In a study comparing intradermal 5% tramadol to prilocaine, both provided similar local anesthetic effect, but tramadol had significantly increased incidence of local rash at the injection site. Because alternatives to local anesthetics are not ideal, referral for allergy testing to rule out a true allergy or to identify a safe anesthetic is recommended.

T

# RE: local anaesthetics Abnormal drug metabolism can occur in conjunction with liver disease, pseudocholinesterase deficiency, and interactions with other medications.

T

Amide-type anesthetics are metabolized by microsomal enzymes in the liver, specifically cytochrome p450–3A4. Concurrent use of medications that inhibit cytochrome p450–3A4 can potentially result in systemic toxicity, especially when larger amounts of anesthetics are used

T

What are the lignocaine doses for use in kids, with and without adrenaline?

1.5-2mg/kg 3.0–4.5 mg/kg with adrenaline

# Concurrent use of medications that inhibit cytochrome p450–3A4 can poten What medications are CYP3A4 inhibitors?

Cytochrome p450–3A4 inhibitors Amiodarone Benzodiazepines (midazolam, triazolam) Carbamazepine Chloramphenicol Cimetidine Clarithromycin Cyclosporine Danazol Dexamethasone Diltiazem Erythromycin Fluconazole Itraconazole Isoniazid Ketoconazole Methadone Methylprednisolone Metronidazole Miconazole Nicardipine Nifedipine Pentoxifylline Propofol Propranolol Quinidine Selective serotonin reuptake inhibitors Terfenadine Tetracycline Thyroxine Valproic acid Verapamil

Lidocaine 1% solution contains 10 mg of lidocaine per 1 mL.

T

The half-life of lidocaine is 90–120 min and is 95% metabolized by the CYP3A4 enzymes in the liver. This time may be prolonged in patients with hepatic failure (average 343 min) or congestive heart failure (136 min). Thus, caution should be exercised when performing significant local anesthesia in patients with these comorbidities. No adjustments are necessary for lidocaine use in patients with renal failure.

T

Decreased cardiac output and hepatic blood flow by beta-blockers can also increase lidocaine levels.

T

# Re: Lignocaine At higher concentrations, muscle twitching, nystagmus, blurred vision, confusion and seizures appear. Cardiac arrest does not occur until very high plasma levels are reached, around 26 µg/mL.

T

What are the signs of lignocaine toxicity at 1–6

Subjective toxicity: lightheadedness, euphoria, tongue and circumoral paresthesia, tinnitus, blurred vision

What are the lignocaine signs of lignocaine toxicity at 5-9?

Objective toxicity: vomiting, tremors, muscular fasciculations

What are the lignocaine signs of lignocaine toxicity at 8-12?

Seizures, cardiopulmonary depression

What are the lignocaine signs of lignocaine toxicity at 12-20?

Coma, respiratory and cardiac arrest

Local anesthetics can affect the cardiovascular system. Transient reactions can occur when using solutions containing epinephrine. These include tachycardia, diaphoresis, tremor, headache, elevated blood pressure, and chest pain.

T

In healthy patients, increased blood pressure and arrhythmias do not usually occur if the dose of epinephrine is limited to 0.5 mg (50 mL of 1: 100 000 dilution). However, patients with underlying systemic diseases, such as hyperthyroidism, cardiac disease, peripheral vascular disease, and pheochromocytoma, as well as those with anxiety disorder, may be more sensitive to epinephrine. The maximum epinephrine dose recommended for such patients is 0.2 mg.

T

Higher toxic blood levels of anesthetics such as lidocaine lead to vasodilatation, hypotension, and bradycardia, which progress to cardiovascular collapse and cardiac arrest. Signs of cardiovascular compromise usually do not manifest until after signs of central nervous system toxicity.

T

Anesthetic potency directly correlates to the degree of myocardial depression. More potent anesthetics, such as bupivacaine and etidocaine, appear to be more cardiotoxic than other anesthetics.

T

Because bupivacaine enters the sodium channel rapidly, but leaves it slowly, it has a greater potential to induce serious re-entrant arrhythmias that may be refractory to treatment. 38 The cardiac toxicity of bupivacaine can be more severe during pregnancy, which may be due to increased progesterone and the adverse effects of pregnancy on venous return during resuscitation

T

Early recognition of anesthetic toxicity can lead to proper and timely management. Initial management of allergic and toxic reactions includes halting the delivery of the anesthetic and maintaining ventilation and oxygenation. Hypoxia and acidosis decrease the seizure threshold and contribute to the cardiodepressant effects of local anesthetics. Seizures can be treated and potentially prevented with thiopental sodium, diazepam, or propofol. Neuromuscular blocking agents such as succinylcholine may be needed to aid in intubation. Hypotension is treated by the administration of fluids; profound hypotension may require vasopressors, such as epinephrine, ephedrine, or phenylephrine. Bradycardia and decreased myocardial contractility may require inotropic agents, such as epinephrine or ephedrine. Bretylium is used to treat recalcitrant dysrhythmias. Amrinone can be used when conventional inotropes are ineffective. Amrinone is a phosphodiesterase inhibitor that leads to increased cAMP in the myocardium and enhanced cardiac contractility.

T

Methemoglobinemia, the presence of increased hemoglobin in the oxidized state instead of the oxygen-carrying reduced state, can occur following the use of local anesthetics. Benzocaine and prilocaine are local anesthetics most commonly associated with clinically significant methemoglobinemia.

T

# Re: methhaemaglobin Several reported cases have occurred in infants or young children after the topical use of benzocaine to mucosal surfaces, and more recently after the application of EMLA to the skin. Infants and children are at greater risk than adults because hemoglobin F is more susceptible to oxidation, newborns have lower levels of reductive enzymes, and the dose tends to be greater per kilogram of body weight. Limiting use to recommended dosages tends to avoid problems; however, susceptibility may increase with glucose-6-phosphate dehydrogenase deficiency, rare and methemoglobin reductase deficiency, and concomitant administration of other methemoglobin-forming drugs, such as sulfonamides and antimalarials

T

Methemoglobinemia presents with a cyanotic appearance in the skin, lips, and nail beds at methemoglobin levels of 10–20%.

T

In addition to the drug history, the presence of cyanosis without cardiorespiratory disease suggests a diagnosis of methemoglobinemia. Symptoms frequently do not occur for 1–3 h following treatment because methemoglobinemia is caused by metabolites of the anesthetic.

T

Conventional pulse oximeters are usually unreliable in the presence of methemoglobinemia; therefore arterial blood gases and methemoglobin levels are recommended.

T

Methemoglobinemia with a level below 30% can usually be managed by removal of the causative drug, oxygen, and observation

T

# Re: Methemoglobinemia Higher levels may need intravenous methylene blue 1–2 mg/kg as a 1% solution. Methylene blue is contraindicated in patients with glucose-6-phosphate deficiency. Ascorbic acid 300–1000 mg/day intravenously in 3–4 doses, is recommended in these patients. Hemodialysis may be considered if symptoms persist

T

Because parabens potentially can displace bilirubin by competitively binding to albumin, the use of preservative-free anesthetic solutions has been suggested in jaundiced neonates.

T

What is the maximum length of emla application in baby < 3months?

1 hour

What is the maximum EMLA application time for patients > 3 months?

4 hours

What is the max dose of EMLA in a baby < 3 months?

1g or 10cm2 area

What is the maximum dose of EMLA in a child aged 1 year?

10g or 100cm2

Benzodiazepines such as diazepam (2–5 mg) and lorazepam (1–2 mg) are effective anxiolytics. Analgesic agents such as hydrocodone and oxycodone can be used prior to procedures as well to increase sedation and to decrease the pain of the procedure

T

For more extensive anesthesia, such as conscious sedation, the patient should be placed on monitoring equipment and resuscitation equipment made available. Intravenous midazolam, diazepam, propofol, and fentanyl are commonly used agents.

T

For more extensive procedures, such as large excisions, ablative laser procedures, and liposuction, patients may require postoperative analgesia. Common medications used are oral hydrocodone or oxycodone, or intramuscular meperidine given at the time of the procedure. In addition, longer-acting local anesthetics such as bupivacaine can be administered at the time of the procedure to give 4–8 h of local postoperative anesthesia.

T

Local infiltration is typically delivered using 30-gauge, 1/2- or 1-inch needles. Larger-diameter needles tend to cause more pain while 32-gauge needles tend to be too flexible and small for easy injection.

T

Field or ring blocks are practical for cyst excisions and incision and drainage of abscesses.

T

A scalp block can be performed by injecting anesthetic approximately 4–5 cm apart starting at the mid-forehead extending circumferentially toward the occiput and back around to the mid-forehead.

T

A ring block around the circumference of the ear provides anesthesia to the ear except for the concha and the external auditory canal.

T

A field block around the nose can also be useful, particularly for rhinophymectomy surgery and other resurfacing procedures.

T

Nerve blocks are useful for procedures involving large surface areas of the face, scalp, hands, and feet, as well as procedures in particularly sensitive areas, such as lips, palms, soles, and digits.

T