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Retrobulbar block revisited and revised
Retrobulbar block revisited and revised Robert C. Hamilton, MB, BCh, FRCPC ABSTRACT In recent years, the traditional Atkinson retrobulbar block anesthesia technique has been modified to reduce the risk of certain complications. Technique modifications described in this paper eliminated anesthesia-induced postoperative extraocular muscle malfunction in a series of 8500 procedures. J Cataract Refract Surg 1996; 22: 1147-1150
I
n this paper, I describe the development of a modified retrobulbar block designed to address the complica-
led to a small incidence of anesthesia-related postoperative diplopia.
tion of postoperative extraocular muscle malfunction that may follow a traditional Atkinson retrobulbar block.
In a 1991 article, Hamed stressed the importance of aiming the retrobulbar needle midway between the
Regional Anesthesia Injection Technique 1
In 1988, my colleagues and 1 reported on regional block anesthesia in 12,000 cataract extraction and intraocular lens implantation procedures. Common to all the procedures was an initial injection using a 38 mm (1 Yz inches), sharp, disposable 27 gauge needle with the entry point at the junction of the medial two thirds and lateral third of the inferior orbit rim (Figure 1). Prolonged postoperative diplopia attributable to anesthetic agent myotoxicity occurred in 23 cases. The report concluded that avoiding direct intramuscular injection should eliminate this problem. By late 1989, the technique I used was a combined retrobulbar/periconal sequence: an initial retrobulbar
4
inferior and lateral rectus muscles to gain entry into the intraconal space, avoiding trauma to the inferior rectus muscle. He suggested moving the entry point of the retrobulbar injection to the temporal side. To avoid damage to both the inferior rectus and the inferior oblique muscle and its nerve supply (Figure 2), I modified the retrobulbar portion of my technique by changing the needle entry location to the lower temporal rim of the orbit (Figure 3, A). The needle track passes initially backward in the sagittal plane and parallel to the orbit floor (i.e., with a 10 degree elevation from the transverse plane), until the midshaft of the needle has reached the plane of the iris and the needle tip has passed the globe equator (Figure 3, B-C). The needle is then directed medially and slightly upward, aiming for an imaginary point behind the globe on the axis formed by the pupil and the macula, so the needle tip approaches but does not pass the midsagittal plane of the globe (Figure 3, D-F).
injection from the traditional entry point on the inferior
Needle penetration of the orbit is gauged by observ-
orbit rim using a 31 mm (1 V4 inches), sharp, disposable 27 gauge needle, as advocated by Katsev and coauthors, 2
ing the hub/shaft junction of the 31 mm needle in relation to the plane of the iris, instead of by measuring from the inferior orbit rim as in the traditional tech-
followed by a medial periconal injection using a short, 30 gauge, sharp disposable needle. 3 This technique still Reprint requests to Robert C. Hamilton, MB, BCh, FRCPC, Gimbel Eye Centre, 4935 40th Avenue NW, Calgary, Alberta, Canada T3A 2NJ.
nique. The modified entry point at the lower temporal orbit rim is slightly above the orbit floor, which makes it unlikely that the needle tip will enter the inferior rectus muscle.
J CATARACT REFRACT SURG-VOL 22, NOVEMBER 1996
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TECHNIQUES: HAMILTON
Discussion
Figure 1. (Hamilton) Retrobulbar block. Small insert shows the needle entry point at the junction of the medial two thirds and lateral third of the inferior orbit rim. The needle's path is close to the orbit floor until the globe equator is passed (A), after which its angle of direction is adjusted upward and medially and advanced to enter the intraconal space posterior to the globe (B) (by permission of Gimbel Educational Services).
Between May 1991 and August 1995, a series of 8500 cataract extraction surgeries was performed by one ophthalmologist using this modified retrobulbar block combined with a complemental medial periconal block; 3 I was the anesthesiologist. There were no cases of postoperative diplopia that could be related to needle trauma to, or local anesthetic injection into, an extraocular muscle.
Although use of peribulbar anesthesia for ophthalmic surgery has been increasing, most surgeons still prefer the retrobulbar method, 5 probably because it was the one in which they were trained and the one they know best. 6 First described in 1936/ Atkinson's retrobulbar anesthesia method became the traditional teaching method for generations of ophthalmology residents and continues to be reproduced in modern ophthalmology and anesthesiology textbooks even though "there is now no doubt that [it] is unsafe and there are medicolegal implications." 8 The needle entry point is at the junction of the medial two thirds and lateral third of the inferior orbit rim (Figure 1), following which the needle is directed toward the orbit apex. 2 Patients are instructed to direct their eyes "up and in" during retrobulbar needle placement "so the inferior oblique muscle and fascia between the lateral and inferior rectus muscles are forward and upward, out of the way." 7 In 1981, Unsold and coauthors9 studied the Atkinson method in a cadaver model. They demonstrated conclusively that as the needle tip approached from the inferotemporal quadrant, it might damage the stretched optic nerve and the posterior pole of the globe or puncture the optic nerve sheath, causing the anesthetic agent to be injected into the subarachnoid space.
Inferior
division Ill
m.
A
Figure 2.
(Hamilton) Right orbit. A: View from above. B: View from the front with the globe removed. The needle path is close to the inferior oblique muscle belly, its motor nerve, and the lateral border of the inferior rectus muscle (from Hunter and coauthors 16).
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J CATARACT REFRACT SURG-VOL 22, NOVEMBER 1996
TECHNIQUES: HAMILTON
Figure 3. (Hamilton) Revised inferotemporal retrobulbar block (using a 27 gauge, 31 mm, sharp, disposable needle). A,D: Views from the front. B,E: Views from the lateral side. C,F: Views from above. The globe is in primary gaze (by permission of Gimbel Educational Services).
In 1986, Pautler and coauthors 10 reported two cases of optic nerve trauma in which long and sharp needles were injected toward the orbit apex with the globe in the "up and in" position; this resulted in catastrophic loss of vision. Based on the study by Unsold and coauthors, they recommended that for retrobulbar blocks patients should fixate in primary gaze and the needle length should be reduced to 32 mm (11,4 inches) and directed toward an imaginary point behind the macula rather than toward the orbit apex. They reported that, in the primary gaze globe position, the optic nerve lies in a nontaut manner on the nasal side of the sagittal plane passing through the visual axis; in this location, the risk of nerve damage is much lower. In 1989, Katsev and coauthors 2 analyzed the dimensions of 120 orbits from 60 human skulls related to the length of needles used for retrobulbar anesthesia and recommended that depth of needle penetration into the orbit be limited to a maximum of31.5 mm (11,4 inches) from the inferior orbit rim to avoid damage to the tightly packed important structures, including the optic nerve, at the orbital apex. In 1992, Liu and coauthors 8 repeated Unsold and coauthors' cadaver experiment in vivo using magnetic resonance imaging and confirmed the finding that the
optic nerve is taut in nasal and upgaze and is sinuous and loose in the primary globe position. Several studies of the myotoxicity oflocal anesthetics have been published, 11 ' 12 particularly damage to the inferior rectus musde, 4 ' 13- 15 which probably indicates that the needle tip did not dear the inferior rectus muscle to lie within the intraconal compartment (Figure 4),
Figure 4. (Hamilton) A straight, 31 mm needle advancing from the inferotemporal quadrant toward the intraconal space has not risen sufficiently from the orbit floor. The needle tip has entered the belly of the inferior rectus muscle (by permission of Gimbel Educational Services).
J CATARACT REFRACT SURG-VOL 22, NOVEMBER 1996
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TECHNIQUES: HAMILTON
Inferior oblique muscle injury and trauma to its motor nerve by regional anesthesia injection have been reported. 16 The tip of a 38 mm (1 Yz inches) retrobulbar needle may enter the superior rectus from an inferotemporal approach. 13 Strabismus after cataract surgery may result from various etiologies, 4 among them extraocular muscle malfunction related to local anesthesic agent myotoxicity or needle trauma.
Conclusion In summary, the traditional retrobulbar block technique was modified by making the needle entry point at the lower temporal rim of the orbit rather than the inferior rim at the junction of the medial two thirds and lateral third. A combined retrobulbar/periconal technique was used in 8500 cases without an occurrence of extraocular muscle damage related to anesthetic injections.
References 1. Hamilton RC, Gimbel HV, Strunin L. Regional anaesthesia for 12,000 cataract extraction and intraocular lens implantation procedures. Can] Anaesth 1988; 35:615623 2. Katsev DA, Drews RC, Rose BT. An anatomic study of retrobulbar needle path length. Ophthalmology 1989; 96:1221-1224 3. Hustead RF, Hamilton RC, Loken RG. Periocular local anesthesia: medial orbital as an alternative to superior nasal injection.] Cataract Refract Surg 1994; 20:197201 4. Hamed LM. Strabismus presenting after cataract surgery. Ophthalmology 1991; 98:247-252
1150
5. Learning DV. Practice styles and preferences of ASCRS members-1994 survey.] Cataract Refract Surg 1995; 21:378-385 6. Forrester JV. Local anaesthesia for eye surgery (editorial). Br] Ophthalmol1992; 76:705 7. Atkinson WS. Retrobulbar injection of anesthetic within the muscular cone (cone injection). Arch Ophthalmol 1936; 16:494-503 8. Liu C, Youl B, Moseley I. Magnetic resonance imaging of the optic nerve in extremes of gaze; implications for the positioning of the globe for retrobulbar anaesthesia. Br] Ophthalmol1992; 76:728-733 9. Unsold R, Stanley JA, DeGroot]. The CT-topography of retrobulbar anesthesia; anatomic-clinical correlation of complications and suggestion of a modified technique. Albrecht von Graefes Arch Klin Exp Ophthalmol 1981; 217:125-136 10. Pautler SE, Grizzard WS, Thompson LN, Wing GL. Blindness from retrobulbar injection into the optic nerve. Ophthalmic Surg 1986; 17:334-337 11. Carlson BM, Emerick S, Komorowski TE, et al. Extraocular muscle regeneration in primates; local anestheticinduced lesions. Ophthalmology 1992; 99:582-589 12. Rainin EA, Carlson BM. Postoperative diplopia and ptosis; a clinical hypothesis on the myotoxicity of local anesthetics. Arch Ophthalmol1985; 103:1337-1339 13. Capo H, RothE, Johnson T, et al. Vertical strabismus after cataract surgery. Ophthalmology 1996; 103:918921 14. Hamed LM, Mancuso A. Inferior rectus muscle contracture syndrome after retrobulbar anesthesia. Ophthalmology 1991; 98:1506-1512 15. Ong-Tone L, Pearce WG. Inferior rectus muscle restriction after retrobulbar anesthesia for cataract extraction. Can] Ophthalmol1989; 24:162-165 16. Hunter DG, Lam GC, Guyton DL. Inferior oblique muscle injury from local anesthesia for cataract surgery. Ophthalmology 1995; 102:501-509
J CATARACT REFRACT SURG-VOL 22, NOVEMBER 1996
I
n this paper, I describe the development of a modified retrobulbar block designed to address the complica-
led to a small incidence of anesthesia-related postoperative diplopia.
tion of postoperative extraocular muscle malfunction that may follow a traditional Atkinson retrobulbar block.
In a 1991 article, Hamed stressed the importance of aiming the retrobulbar needle midway between the
Regional Anesthesia Injection Technique 1
In 1988, my colleagues and 1 reported on regional block anesthesia in 12,000 cataract extraction and intraocular lens implantation procedures. Common to all the procedures was an initial injection using a 38 mm (1 Yz inches), sharp, disposable 27 gauge needle with the entry point at the junction of the medial two thirds and lateral third of the inferior orbit rim (Figure 1). Prolonged postoperative diplopia attributable to anesthetic agent myotoxicity occurred in 23 cases. The report concluded that avoiding direct intramuscular injection should eliminate this problem. By late 1989, the technique I used was a combined retrobulbar/periconal sequence: an initial retrobulbar
4
inferior and lateral rectus muscles to gain entry into the intraconal space, avoiding trauma to the inferior rectus muscle. He suggested moving the entry point of the retrobulbar injection to the temporal side. To avoid damage to both the inferior rectus and the inferior oblique muscle and its nerve supply (Figure 2), I modified the retrobulbar portion of my technique by changing the needle entry location to the lower temporal rim of the orbit (Figure 3, A). The needle track passes initially backward in the sagittal plane and parallel to the orbit floor (i.e., with a 10 degree elevation from the transverse plane), until the midshaft of the needle has reached the plane of the iris and the needle tip has passed the globe equator (Figure 3, B-C). The needle is then directed medially and slightly upward, aiming for an imaginary point behind the globe on the axis formed by the pupil and the macula, so the needle tip approaches but does not pass the midsagittal plane of the globe (Figure 3, D-F).
injection from the traditional entry point on the inferior
Needle penetration of the orbit is gauged by observ-
orbit rim using a 31 mm (1 V4 inches), sharp, disposable 27 gauge needle, as advocated by Katsev and coauthors, 2
ing the hub/shaft junction of the 31 mm needle in relation to the plane of the iris, instead of by measuring from the inferior orbit rim as in the traditional tech-
followed by a medial periconal injection using a short, 30 gauge, sharp disposable needle. 3 This technique still Reprint requests to Robert C. Hamilton, MB, BCh, FRCPC, Gimbel Eye Centre, 4935 40th Avenue NW, Calgary, Alberta, Canada T3A 2NJ.
nique. The modified entry point at the lower temporal orbit rim is slightly above the orbit floor, which makes it unlikely that the needle tip will enter the inferior rectus muscle.
J CATARACT REFRACT SURG-VOL 22, NOVEMBER 1996
1147
TECHNIQUES: HAMILTON
Discussion
Figure 1. (Hamilton) Retrobulbar block. Small insert shows the needle entry point at the junction of the medial two thirds and lateral third of the inferior orbit rim. The needle's path is close to the orbit floor until the globe equator is passed (A), after which its angle of direction is adjusted upward and medially and advanced to enter the intraconal space posterior to the globe (B) (by permission of Gimbel Educational Services).
Between May 1991 and August 1995, a series of 8500 cataract extraction surgeries was performed by one ophthalmologist using this modified retrobulbar block combined with a complemental medial periconal block; 3 I was the anesthesiologist. There were no cases of postoperative diplopia that could be related to needle trauma to, or local anesthetic injection into, an extraocular muscle.
Although use of peribulbar anesthesia for ophthalmic surgery has been increasing, most surgeons still prefer the retrobulbar method, 5 probably because it was the one in which they were trained and the one they know best. 6 First described in 1936/ Atkinson's retrobulbar anesthesia method became the traditional teaching method for generations of ophthalmology residents and continues to be reproduced in modern ophthalmology and anesthesiology textbooks even though "there is now no doubt that [it] is unsafe and there are medicolegal implications." 8 The needle entry point is at the junction of the medial two thirds and lateral third of the inferior orbit rim (Figure 1), following which the needle is directed toward the orbit apex. 2 Patients are instructed to direct their eyes "up and in" during retrobulbar needle placement "so the inferior oblique muscle and fascia between the lateral and inferior rectus muscles are forward and upward, out of the way." 7 In 1981, Unsold and coauthors9 studied the Atkinson method in a cadaver model. They demonstrated conclusively that as the needle tip approached from the inferotemporal quadrant, it might damage the stretched optic nerve and the posterior pole of the globe or puncture the optic nerve sheath, causing the anesthetic agent to be injected into the subarachnoid space.
Inferior
division Ill
m.
A
Figure 2.
(Hamilton) Right orbit. A: View from above. B: View from the front with the globe removed. The needle path is close to the inferior oblique muscle belly, its motor nerve, and the lateral border of the inferior rectus muscle (from Hunter and coauthors 16).
1148
J CATARACT REFRACT SURG-VOL 22, NOVEMBER 1996
TECHNIQUES: HAMILTON
Figure 3. (Hamilton) Revised inferotemporal retrobulbar block (using a 27 gauge, 31 mm, sharp, disposable needle). A,D: Views from the front. B,E: Views from the lateral side. C,F: Views from above. The globe is in primary gaze (by permission of Gimbel Educational Services).
In 1986, Pautler and coauthors 10 reported two cases of optic nerve trauma in which long and sharp needles were injected toward the orbit apex with the globe in the "up and in" position; this resulted in catastrophic loss of vision. Based on the study by Unsold and coauthors, they recommended that for retrobulbar blocks patients should fixate in primary gaze and the needle length should be reduced to 32 mm (11,4 inches) and directed toward an imaginary point behind the macula rather than toward the orbit apex. They reported that, in the primary gaze globe position, the optic nerve lies in a nontaut manner on the nasal side of the sagittal plane passing through the visual axis; in this location, the risk of nerve damage is much lower. In 1989, Katsev and coauthors 2 analyzed the dimensions of 120 orbits from 60 human skulls related to the length of needles used for retrobulbar anesthesia and recommended that depth of needle penetration into the orbit be limited to a maximum of31.5 mm (11,4 inches) from the inferior orbit rim to avoid damage to the tightly packed important structures, including the optic nerve, at the orbital apex. In 1992, Liu and coauthors 8 repeated Unsold and coauthors' cadaver experiment in vivo using magnetic resonance imaging and confirmed the finding that the
optic nerve is taut in nasal and upgaze and is sinuous and loose in the primary globe position. Several studies of the myotoxicity oflocal anesthetics have been published, 11 ' 12 particularly damage to the inferior rectus musde, 4 ' 13- 15 which probably indicates that the needle tip did not dear the inferior rectus muscle to lie within the intraconal compartment (Figure 4),
Figure 4. (Hamilton) A straight, 31 mm needle advancing from the inferotemporal quadrant toward the intraconal space has not risen sufficiently from the orbit floor. The needle tip has entered the belly of the inferior rectus muscle (by permission of Gimbel Educational Services).
J CATARACT REFRACT SURG-VOL 22, NOVEMBER 1996
1149
TECHNIQUES: HAMILTON
Inferior oblique muscle injury and trauma to its motor nerve by regional anesthesia injection have been reported. 16 The tip of a 38 mm (1 Yz inches) retrobulbar needle may enter the superior rectus from an inferotemporal approach. 13 Strabismus after cataract surgery may result from various etiologies, 4 among them extraocular muscle malfunction related to local anesthesic agent myotoxicity or needle trauma.
Conclusion In summary, the traditional retrobulbar block technique was modified by making the needle entry point at the lower temporal rim of the orbit rather than the inferior rim at the junction of the medial two thirds and lateral third. A combined retrobulbar/periconal technique was used in 8500 cases without an occurrence of extraocular muscle damage related to anesthetic injections.
References 1. Hamilton RC, Gimbel HV, Strunin L. Regional anaesthesia for 12,000 cataract extraction and intraocular lens implantation procedures. Can] Anaesth 1988; 35:615623 2. Katsev DA, Drews RC, Rose BT. An anatomic study of retrobulbar needle path length. Ophthalmology 1989; 96:1221-1224 3. Hustead RF, Hamilton RC, Loken RG. Periocular local anesthesia: medial orbital as an alternative to superior nasal injection.] Cataract Refract Surg 1994; 20:197201 4. Hamed LM. Strabismus presenting after cataract surgery. Ophthalmology 1991; 98:247-252
1150
5. Learning DV. Practice styles and preferences of ASCRS members-1994 survey.] Cataract Refract Surg 1995; 21:378-385 6. Forrester JV. Local anaesthesia for eye surgery (editorial). Br] Ophthalmol1992; 76:705 7. Atkinson WS. Retrobulbar injection of anesthetic within the muscular cone (cone injection). Arch Ophthalmol 1936; 16:494-503 8. Liu C, Youl B, Moseley I. Magnetic resonance imaging of the optic nerve in extremes of gaze; implications for the positioning of the globe for retrobulbar anaesthesia. Br] Ophthalmol1992; 76:728-733 9. Unsold R, Stanley JA, DeGroot]. The CT-topography of retrobulbar anesthesia; anatomic-clinical correlation of complications and suggestion of a modified technique. Albrecht von Graefes Arch Klin Exp Ophthalmol 1981; 217:125-136 10. Pautler SE, Grizzard WS, Thompson LN, Wing GL. Blindness from retrobulbar injection into the optic nerve. Ophthalmic Surg 1986; 17:334-337 11. Carlson BM, Emerick S, Komorowski TE, et al. Extraocular muscle regeneration in primates; local anestheticinduced lesions. Ophthalmology 1992; 99:582-589 12. Rainin EA, Carlson BM. Postoperative diplopia and ptosis; a clinical hypothesis on the myotoxicity of local anesthetics. Arch Ophthalmol1985; 103:1337-1339 13. Capo H, RothE, Johnson T, et al. Vertical strabismus after cataract surgery. Ophthalmology 1996; 103:918921 14. Hamed LM, Mancuso A. Inferior rectus muscle contracture syndrome after retrobulbar anesthesia. Ophthalmology 1991; 98:1506-1512 15. Ong-Tone L, Pearce WG. Inferior rectus muscle restriction after retrobulbar anesthesia for cataract extraction. Can] Ophthalmol1989; 24:162-165 16. Hunter DG, Lam GC, Guyton DL. Inferior oblique muscle injury from local anesthesia for cataract surgery. Ophthalmology 1995; 102:501-509
J CATARACT REFRACT SURG-VOL 22, NOVEMBER 1996