Spinal anesthesia-induced hypotension (SAIH) occurs frequently, particularly in the elderly and in patients undergoing caesarean section. SAIH is caused by arterial and venous vasodilatation resulting from the sympathetic block along with a paradoxical activation of cardioinhibitory receptors. Bradycardia after spinal anesthesia (SA) must always be treated as a warning sign of an important hemodynamic compromise. Fluid preloading (before initiation of the SA) with colloids such as hydroxyethyl starch (HES) effectively reduces the incidence and severity of arterial hypotension, whereas crystalloid preloading is not indicated. Co-loading with crystalloid or colloid is as equally effective to HES preloading, provided that the speed of administration is adequate (ie, bolus over 5 to 10 minutes). Ephedrine has traditionally been considered the vasoconstrictor of choice, especially for use during SAIH associated with bradycardia. Phenylephrine, a α 1 adrenergic receptor agonist, is increasingly used to treat SAIH and its prophylactic administration (ie, immediately after intrathecal injection of local anesthetics) has been shown to decrease the incidence of arterial hypotension. The role of norepinephrine as a possible alternative to phenylephrine seems promising. Other drugs, such as serotonin receptor antagonists (ondansetron), have been shown to limit the blood pressure drop after SA by inhibiting the Bezold-Jarisch reflex (BJR), but further studies are needed before their widespread use can be recommended.
Summary
Interscalene brachial plexus block provides analgesia for shoulder surgery but is associated with hemidiaphragmatic paralysis. Before considering a combined suprascapular and axillary nerve block as an alternative to interscalene brachial plexus block, evaluation of the incidence of diaphragmatic dysfunction according to the approach to the suprascapular nerve is necessary. We randomly allocated 84 patients undergoing arthroscopic shoulder surgery to an anterior or a posterior approach to the suprascapular nerve block combined with an axillary nerve block using 10 ml ropivacaine 0.375% for each nerve. The primary outcome was the incidence of hemidiaphragmatic paralysis diagnosed by ultrasound. Secondary outcomes included: characterisation of the hemidiaphragmatic paralysis over time; numeric rating scale pain scores; oral morphine equivalent consumption; and patient satisfaction. The incidence of hemidiaphragmatic paralysis was 40% (n = 17) vs. 2% (n = 1) in the anterior and posterior groups, respectively (p < 0.001). In one third of patients with hemidiaphragmatic paralysis, it persisted beyond the eighth hour. The median (interquartile range [range]) oral morphine equivalent consumption was significantly higher in the posterior approach when compared with the anterior approach, whether in the recovery area (20 [5–31 (0–60)] mg vs. 7.5 [0–14 (0–52)] mg, respectively; p = 0.004) or during the first 24 h (82 [61–127 (12–360) mg] vs. 58 [30–86 (0–160)] mg, respectively; p = 0.01). Patient satisfaction was comparable between groups (p = 0.6). Compared with the anterior approach, diaphragmatic function is best preserved with the posterior needle approach to the suprascapular nerve block.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.