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Chapter 47. Regional Anesthesia and Systemic Disease

Lumbar neuraxial anesthesia results in the following pulmonary changes:

A. Bronchoconstriction is frequently seen.

B. Effort-dependent pulmonary function tests (eg, FEV1) are decreased.

C. Partial pressure of CO2 rises and partial pressure of O2 falls.

D. Tidal volume decreases with a compensatory rise in respiratory rate.

B is correct. Effort-dependent pulmonary function tests such as FEV1, FVC, and PEFR are modestly decreased due to weakness of abdominal and chest wall muscles that are used during forced expiration.

A is incorrect. Bronchoconstriction is a theoretical concern due to reduced sympathetic tone; however, this does not occur to any significant degree.

C is incorrect. Partial pressure of CO2 and O2 are essentially unchanged.

D is incorrect. Lumbar epidural anesthesia does not affect resting minute ventilation, tidal volume, or respiratory rate.

With regard to brachial plexus block and phrenic nerve blockade, which of the following is true?

A. Phrenic nerve blockade is poorly tolerated by most patients, and if it occurs patients must remain in hospital for observation.

B. Regional anesthesia for shoulder surgery is impossible without interscalene block, and therefore a high risk of phrenic nerve block.

C. The risk of phrenic nerve block reduces with more distal approaches to brachial plexus blockade.

D. Unilateral phrenic nerve blockade results in a 50% decrease in FEV1 and FVC.

C is correct. The risk of phrenic nerve block is as high as 100% with the interscalene approach, although the risk may be reduced with low volumes of local anesthetic. The supraclavicular approach is typically associated with a 50% risk of phrenic nerve block, although this may be reduced significantly with ultrasound guidance. Infraclavicular (coracoid) and axillary approaches are sufficiently distal to avoid the phrenic nerve altogether.

A is incorrect. Phrenic nerve blockade is of questionable significance in patients with good respiratory function, most of whom will remain asymptomatic or complain only of a mild, subjective sensation of dyspnea.

B is incorrect. Interscalene block is typically used for patients undergoing shoulder surgery as it provides excellent analgesia. However, in patients who may not tolerate phrenic nerve blockade, alternative approaches can be used such as axillary nerve or infraclavicular brachial plexus blocks combined with suprascapular nerve block.

D is incorrect. Unilateral phrenic nerve block results in paralysis of half of the diaphragm, which is the main ...

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