- Email: [email protected]
Monitoring after Retrobulbar Injection
LETTERS
Authors' reply
Dear Editor: The two letters by Drs. Farber and Fourman and Dr. Kutner have raised two issues concerning our recent article entitled "Traumatic Hyphema in Children: Treatment with Epsilon-aminocaproic Acid" (Ophthal mology 1987; 94:1232-7). The first problem is that of study design and numbers of cases to be recruited. The second issue is the age groups in which the drug may have beneficial effect. We did not state, as Dr. Farber claims, that" epsilon aminocaproic acid [EACA] has no benefit." Nor did we conclude, as claimed by Drs. Fourman and Kutner, that "aminocaproic acid was not effective in reducing the risk of secondary hemorrhage." We clearly noted in our abstract that in view of the low rebleed rate in our con trol group, "the efficacy ofEACA in reducing the rate of rebleeds could not be determined." Dr. Farber's com ment that there were too few rebleeds in our control group to allow any difference between control and treatment groups to emerge is restating our point. We devoted most of our discussion in the article to the issue of why our rebleed rate was so low when compared with the many studies in the literature dealing with re bleeds in hyphemas, and especially when compared with the very high rates in the placebo groups in two pla cebo-controlled trials that used EACA. 1•2 In trying to account for this latter discrepancy, we commented that several confounding variables not controlled for in those two studies may have led to spuriously high rebleed rates in the control groups, thus rendering invalid the authors' claims of clinical effect ofEACA for all patients. In other words, although their statistical tests yielded significant results for their data within the limits of their study designs, the fact they did not control for these variables leaves these designs subject to question. The prospective study by Fourman and Kutner 3 is the only one in addition to our study dealing with EACA and hyphema that controlled for preadmission anti platelet agents. We commend them for their overall protocol which listed the same strict criteria for entry and handling of patients as we used in our study. How ever, they terminated their recruiting of patients when a significant difference was found between the rebleed rates in the treated and placebo groups. In our opinion, this study is inadequate for such a drug trial. We emphasized in our article that the number of pa tients required for such a study has to be determined before the start of the study. This number is calculated based on the approximate expected rate of occurrence of rebleeds in untreated cases. Dr. Farber correctly points out the issue of power of the statistical tests for signifi cance in such a study: This can only be satisfied by a sufficiently large predetermined patient sample. In the case of drug trials in hyphema, this sample would have to be quite large, certainly much larger than reported in any of the four EACA studies, including our study. 1- 3 Therefore, to address the first of the two issues, that of
study design, we agree with Dr. Farber that a large pro spective randomized trial is needed. This underscores one of our stated conclusions in our discussion. Furthermore, variables that have to be controlled in such a study include use of antiplatelet agents before admission, age of patients, time from injury to admis sion, and racial profiles. We also concur that a multi center study is probably the optimal means by which to obtain a sufficiently large patient sample. Concerning the issue of effect ofEACA in various age groups, we agree with Drs. Fourman and Kutner that its efficacy in the pediatric population requires further large studies. However, we purposely chose not to confine our discussion to the use of this drug in children alone. We believe that there are strong indications for large pro spective trials in both adult and pediatric patients which adhere to the principles of appropriate study design and control of possible confounding variables. Dr. Romano addresses the controversy of steroids versus antifibrinolytic therapy in treating hyphemas. In answer to his comments, we are sure he will be relieved that we will not choose here to add to nor raise "usual weary objections" to his conclusions about the efficacy of steroids in hyphema management. 4 We have not used his steroid protocols in routine hyphema management. Thus, we have no data to dispute his experience with this therapy. However, we believe that a well-designed, prospective, placebo-controlled study should be under taken for steroid treatment to prove its efficacy. It should conform to the same design criteria discussed above for EACA: the studies he lists suffer from the same deficiencies in design and patient samples as the EACA trials. We were pleased that these have been brought to our attention. In our opinion, until the suggested large pro spective trials are done we believe that the cases for EACA or steroids in routine treatment of traumatic hy phema are still open. STEPHEN P. KRAFT, MD JOHN S. CRAWFORD, MD Toronto, Canada References 1. Crouch ER Jr, Frenkel M. Aminocaproic acid in the treatment of traumatic hyphema. Am J Ophthalmol1976; 81:355-60. 2. McGetrick JJ, Jampol LM, Goldberg MF, et al. Aminocaproic acid decreases secondary hemorrhage after traumatic hyphema. Arch Ophthalmol1983; 101 :1031-3. 3. Kutner 8 , Fourman S, Brein K, et al. Aminocaproic acid reduces the risk of secondary hemorrhage in patients with traumatic hyphema. Arch Ophthalmol1987; 105;206-8. 4. Rynne MV, Romano PE . Systemic corticosteroids in the treatment of traumatic hyphema . J Pediatr Ophthalmol Strabismus 1980; 17(3):141-3.
Monitoring after Retrobulbar Injection
Dear Editor: After reading the article " Brain Stem Anesthesia after Retrobulbar Block" by Javitt et al (Ophthalmology
709
OPHTHALMOLOGY
•
MAY 1988 •
1987,: 94:718-24) in which both the authors and the reviewer impress upon us the necessity for the anesthesi ologist to be on hand to deal with the complications that can occur, one wonders what should be done with re spect to all the other procedures in which retrobulbar anesthesia is used such as in retinal photocoagulation and in cyclocryotherapy. A majority ofthese procedures are not carried out in an operating room and there is no anesthesiologist close at hand. In addition, there is no monitoring or intravenous line during the time in which the retrobulbar anesthesia is being administered. If complications do occur, such as those described in the article, the closest help would probably be the arrest team in a hospital or other trained personnel in a private clinic. Should all these procedures be done only in the pres ence of an anesthetist or when an anesthetist is close at hand? Historically, these procedures have been done in outpatient facilities solely under the direction of an oph thalmologist. Should monitoring always be done?
M. K. MATHEN, MD, FRCSC Winnipeg, Canada
Author's reply
Dear Editor: Dr. Mathen raises two separate but crucial points in his letter. First, is there a risk ofapnea after any retrobul bar injection of anesthetic, be it for cataract or outpa tient photocoagulation? Second, is the presence of an anesthesiologist as important in the outpatient setting as in the operating room? Although the cases of apnea we reported followed ret robulbar injection for intraocular surgery, I have per sonally witnessed one episode of transient apnea after retrobulbar injection for a laser procedure. In that in stance, the laser room was equipped with an emergency cart, respiratory support was initiated by bag mask
710
VOLUME 95
•
NUMBER 5
within one minute, and by the time with cardiac arrest team arrived, the patient had resumed spontaneous res pirations. The patient suffered no sequelae and was dis charged from the hospital after inpatient monitoring. I have heard anecdotal reports of similar episodes from other ophthalmologists. The frequency of apnea after retrobulbar block is be tween l/1000 and l/10,000 injections according to the chart review study performed by Wittpenn and co workers. 1 Thus, although this complication is extremely rare, a physician must always be prepared to deal with rare adverse effects of any treatment he administers. The means of preparedness will vary from site to site de pending on the rapidity with which an arrest team is likely to respond and the level of training the ophthal mologist has in emergency life support. I believe a bag/ mask, oral airways, and oxygen should at least be on hand in any setting in which they might be needed. Intraocular surgery in the operating room introduces additional factors that make the presence of an anesthe tist more important than in the outpatient setting. The patient is generally sedated and may be draped by the time an adverse reaction occurs. The surgeon may be out of the room scrubbing or may be involved in the intraocular phase of the surgery and thus unable to di rect an emergency response. In this setting, monitoring by skilled personnel other than the surgeon is essential while at the laser, the surgeon will generally feel com fortable in managing any adverse reaction that may occur. If the treating ophthalmologist has particular rea sons to be concerned about the stability ofthe patient at the laser, however, monitoring may certainly be in order. JONATHAN JAVITT, MD, MPH Baltimore, Maryland Reference 1. Wittpenn J, Papoza P, Sternberg P, Kuwashirna L, Sakald J, Patz A. Respiratory arrest following retrobulbar anesthesia. Ophthalmology
1986; 93:867-70.
Authors' reply
Dear Editor: The two letters by Drs. Farber and Fourman and Dr. Kutner have raised two issues concerning our recent article entitled "Traumatic Hyphema in Children: Treatment with Epsilon-aminocaproic Acid" (Ophthal mology 1987; 94:1232-7). The first problem is that of study design and numbers of cases to be recruited. The second issue is the age groups in which the drug may have beneficial effect. We did not state, as Dr. Farber claims, that" epsilon aminocaproic acid [EACA] has no benefit." Nor did we conclude, as claimed by Drs. Fourman and Kutner, that "aminocaproic acid was not effective in reducing the risk of secondary hemorrhage." We clearly noted in our abstract that in view of the low rebleed rate in our con trol group, "the efficacy ofEACA in reducing the rate of rebleeds could not be determined." Dr. Farber's com ment that there were too few rebleeds in our control group to allow any difference between control and treatment groups to emerge is restating our point. We devoted most of our discussion in the article to the issue of why our rebleed rate was so low when compared with the many studies in the literature dealing with re bleeds in hyphemas, and especially when compared with the very high rates in the placebo groups in two pla cebo-controlled trials that used EACA. 1•2 In trying to account for this latter discrepancy, we commented that several confounding variables not controlled for in those two studies may have led to spuriously high rebleed rates in the control groups, thus rendering invalid the authors' claims of clinical effect ofEACA for all patients. In other words, although their statistical tests yielded significant results for their data within the limits of their study designs, the fact they did not control for these variables leaves these designs subject to question. The prospective study by Fourman and Kutner 3 is the only one in addition to our study dealing with EACA and hyphema that controlled for preadmission anti platelet agents. We commend them for their overall protocol which listed the same strict criteria for entry and handling of patients as we used in our study. How ever, they terminated their recruiting of patients when a significant difference was found between the rebleed rates in the treated and placebo groups. In our opinion, this study is inadequate for such a drug trial. We emphasized in our article that the number of pa tients required for such a study has to be determined before the start of the study. This number is calculated based on the approximate expected rate of occurrence of rebleeds in untreated cases. Dr. Farber correctly points out the issue of power of the statistical tests for signifi cance in such a study: This can only be satisfied by a sufficiently large predetermined patient sample. In the case of drug trials in hyphema, this sample would have to be quite large, certainly much larger than reported in any of the four EACA studies, including our study. 1- 3 Therefore, to address the first of the two issues, that of
study design, we agree with Dr. Farber that a large pro spective randomized trial is needed. This underscores one of our stated conclusions in our discussion. Furthermore, variables that have to be controlled in such a study include use of antiplatelet agents before admission, age of patients, time from injury to admis sion, and racial profiles. We also concur that a multi center study is probably the optimal means by which to obtain a sufficiently large patient sample. Concerning the issue of effect ofEACA in various age groups, we agree with Drs. Fourman and Kutner that its efficacy in the pediatric population requires further large studies. However, we purposely chose not to confine our discussion to the use of this drug in children alone. We believe that there are strong indications for large pro spective trials in both adult and pediatric patients which adhere to the principles of appropriate study design and control of possible confounding variables. Dr. Romano addresses the controversy of steroids versus antifibrinolytic therapy in treating hyphemas. In answer to his comments, we are sure he will be relieved that we will not choose here to add to nor raise "usual weary objections" to his conclusions about the efficacy of steroids in hyphema management. 4 We have not used his steroid protocols in routine hyphema management. Thus, we have no data to dispute his experience with this therapy. However, we believe that a well-designed, prospective, placebo-controlled study should be under taken for steroid treatment to prove its efficacy. It should conform to the same design criteria discussed above for EACA: the studies he lists suffer from the same deficiencies in design and patient samples as the EACA trials. We were pleased that these have been brought to our attention. In our opinion, until the suggested large pro spective trials are done we believe that the cases for EACA or steroids in routine treatment of traumatic hy phema are still open. STEPHEN P. KRAFT, MD JOHN S. CRAWFORD, MD Toronto, Canada References 1. Crouch ER Jr, Frenkel M. Aminocaproic acid in the treatment of traumatic hyphema. Am J Ophthalmol1976; 81:355-60. 2. McGetrick JJ, Jampol LM, Goldberg MF, et al. Aminocaproic acid decreases secondary hemorrhage after traumatic hyphema. Arch Ophthalmol1983; 101 :1031-3. 3. Kutner 8 , Fourman S, Brein K, et al. Aminocaproic acid reduces the risk of secondary hemorrhage in patients with traumatic hyphema. Arch Ophthalmol1987; 105;206-8. 4. Rynne MV, Romano PE . Systemic corticosteroids in the treatment of traumatic hyphema . J Pediatr Ophthalmol Strabismus 1980; 17(3):141-3.
Monitoring after Retrobulbar Injection
Dear Editor: After reading the article " Brain Stem Anesthesia after Retrobulbar Block" by Javitt et al (Ophthalmology
709
OPHTHALMOLOGY
•
MAY 1988 •
1987,: 94:718-24) in which both the authors and the reviewer impress upon us the necessity for the anesthesi ologist to be on hand to deal with the complications that can occur, one wonders what should be done with re spect to all the other procedures in which retrobulbar anesthesia is used such as in retinal photocoagulation and in cyclocryotherapy. A majority ofthese procedures are not carried out in an operating room and there is no anesthesiologist close at hand. In addition, there is no monitoring or intravenous line during the time in which the retrobulbar anesthesia is being administered. If complications do occur, such as those described in the article, the closest help would probably be the arrest team in a hospital or other trained personnel in a private clinic. Should all these procedures be done only in the pres ence of an anesthetist or when an anesthetist is close at hand? Historically, these procedures have been done in outpatient facilities solely under the direction of an oph thalmologist. Should monitoring always be done?
M. K. MATHEN, MD, FRCSC Winnipeg, Canada
Author's reply
Dear Editor: Dr. Mathen raises two separate but crucial points in his letter. First, is there a risk ofapnea after any retrobul bar injection of anesthetic, be it for cataract or outpa tient photocoagulation? Second, is the presence of an anesthesiologist as important in the outpatient setting as in the operating room? Although the cases of apnea we reported followed ret robulbar injection for intraocular surgery, I have per sonally witnessed one episode of transient apnea after retrobulbar injection for a laser procedure. In that in stance, the laser room was equipped with an emergency cart, respiratory support was initiated by bag mask
710
VOLUME 95
•
NUMBER 5
within one minute, and by the time with cardiac arrest team arrived, the patient had resumed spontaneous res pirations. The patient suffered no sequelae and was dis charged from the hospital after inpatient monitoring. I have heard anecdotal reports of similar episodes from other ophthalmologists. The frequency of apnea after retrobulbar block is be tween l/1000 and l/10,000 injections according to the chart review study performed by Wittpenn and co workers. 1 Thus, although this complication is extremely rare, a physician must always be prepared to deal with rare adverse effects of any treatment he administers. The means of preparedness will vary from site to site de pending on the rapidity with which an arrest team is likely to respond and the level of training the ophthal mologist has in emergency life support. I believe a bag/ mask, oral airways, and oxygen should at least be on hand in any setting in which they might be needed. Intraocular surgery in the operating room introduces additional factors that make the presence of an anesthe tist more important than in the outpatient setting. The patient is generally sedated and may be draped by the time an adverse reaction occurs. The surgeon may be out of the room scrubbing or may be involved in the intraocular phase of the surgery and thus unable to di rect an emergency response. In this setting, monitoring by skilled personnel other than the surgeon is essential while at the laser, the surgeon will generally feel com fortable in managing any adverse reaction that may occur. If the treating ophthalmologist has particular rea sons to be concerned about the stability ofthe patient at the laser, however, monitoring may certainly be in order. JONATHAN JAVITT, MD, MPH Baltimore, Maryland Reference 1. Wittpenn J, Papoza P, Sternberg P, Kuwashirna L, Sakald J, Patz A. Respiratory arrest following retrobulbar anesthesia. Ophthalmology
1986; 93:867-70.