[Peribulbar anesthesia versus retrobulbar anesthesia with facial nerve block. Techniques, local anesthetics and additives, akinesia and sensory block, complications].

BACKGROUND

Retrobulbar anesthesia (RETRO), combined with a facial block, is the most frequently employed method of anesthesia in cataract surgery. There is, however, an increasing tendency to use peribulbar anesthesia (PERI), which is claimed to provide the same degree of anesthesia and akinesia as RETRO while reducing many of the complications.

OBJECTIVES OF THE STUDY

Survey of the principal techniques of RETRO, facial block and PERI as well as of the most important local anesthetics and additives; quantitative investigation of resulting akinesia and sensory blockade; comparison of systemic and local complications (literature review).

TECHNIQUES OF LOCAL ANESTHESIA

A) RETRO: 1) Atkinson technique: injection within the orbital muscle cone, superonasal eye position during injection; 2) Unsöld technique: primary eye position during injection (advantage: lower risk of optic nerve lesion). - B) Facial block: 1) O'Brien technique: injection anterior to the tragus of the ear, just above the condyloid process of the mandible (disadvantage: frequently blockade of the upper portion only of the peripheral facial nerve); 2) Nadbath/Rehman technique (modified O'Brien block): injection just inferior to the earlobe (advantage: better orbicularis akinesia due to blockade of upper and lower portions of peripheral facial nerve); 3) van Lint technique: infiltration anesthesia at the temporal orbital margin, aiming at the short zygomatic branches of the facial nerve (disadvantage: bad orbicularis akinesia). - C) PERI: 1) Technique with two injections outside the muscle cone (inferotemporally and superonasally), just past the equator; 2) one-injection technique, mostly inferotemporally (disadvantage: worse akinesia).

LOCAL ANESTHETICS

A) Short and weak action: lidocaine and prilocaine; advantages: good tissue penetration, low toxicity. - B) Intermediate duration and potency of action: mepivacaine; advantage: pronounced vasoconstrictor activity, alternative to adrenaline. - C) Long and strong action: 1) etidocaine; advantage: pronounced motor blockade, particularly suitable for facial block; 2) bupivacaine; advantage: pronounced sensory blockade, excellent postoperative analgesia; disadvantage: relatively toxic (cave: cardiac and respiratory arrest). - D) Mixtures of local anesthetics: mostly lidocaine-bupivacaine mixture; combines the advantages short-onset action (lidocaine) and long-duration action (bupivacaine).

ADDITIVES TO LOCAL ANESTHETICS

Adrenaline: prolongs the action of local anesthetics with short and intermediate duration of action, reduces the incidence of hemorrhages and of intraoperative vitreous bulging. - Hyaluronidase: highly effective for prevention of vitreous bulging.

AKINESIA AND SENSORY BLOCKADE

In randomized order, 160 cataract patients received PERI (technique with 2 injections) with 6, 8 or 10 ml of a bupivacaine-lidocaine-hyaluronidase mixture (without facial block) or RETRO (Unsöld technique) with 5 ml of the above mixture, combined with a Nadbath/Rehman facial nerve block (5 ml etidocaine-lidocaine mixture). Measured 20 min after injection (intervening period of oculopression), the smallest ocular motility (Kestenbaum limbus test) was left after RETRO. After administration of PERI - even with a volume of 10 ml - the range of residual ocular motility was always higher, i.e., there was a less reliable globe akinesia than after RETRO. The lid closure force (Straub technique) averaged zero after all methods of anesthesia; however, the smallest spread (highest reliability) was observed after PERI. Complete corneal anesthesia (Draeger esthesiometer) was found in nearly all cases, i.e., RETRO and PERI are comparably effective concerning sensory blockade...