Evaluation of posttonsillectomy hemorrhage and risk factors

Evaluation of posttonsillectomy hemorrhage and risk factors JULIE L. WEI, MD, CHARLES W. BEATTY, MD, and RAY O. GUSTAFSON, MD, Rochester, Minnesota

BACKGROUND: A 13-year retrospective study was undertaken to determine the incidence of posttonsillectomy hemorrhage, to evaluate potential risk factors, and to assess the efficacy and safety of ambulatory tonsillectomy. METHODS: From January 1985 to December 1997, 4662 patients underwent tonsillectomy at our institution. Ninety patients with posttonsillectomy bleeding were identified. For each patient with posttonsillectomy bleeding, 2 nonbleeding control subjects were selected and matched by age and sex to evaluate potential risk factors. RESULTS: Age was the only factor found to be statistically significant among the bleeding patients and the control group. The highest incidence (3.61%) of posttonsillectomy hemorrhage occurred in patients 21 to 30 years of age. In our experience, secondary hemorrhage was more common than primary hemorrhage, presenting most frequently on postoperative days 5 to 7. CONCLUSIONS: The incidence of posttonsillectomy bleeding in this review was 1.93%, and about half (47%) of the patients with posttonsillectomy hemorrhage returned to the operating room for hemorrhage control. The highest incidence (3.61%) of posttonsillectomy hemorrhage occurred in patients 21 to 30 years of age. Patients with posttonsillectomy hemorrhage, regardless of management, had a 12% incidence of subsequent hemorrhage. We found no difference in the incidence of posttonsillectomy bleeding between outpatient and inpatient procedures. (Otolaryngol Head Neck Surg 2000;123:229-35.)

T

medical practice, these procedures are increasingly performed on an outpatient basis. Both retrospective and prospective studies have assessed the safety of ambulatory adenotonsillectomy, and the consensus is that it is a safe practice given specific patient selection criteria.1-5 Despite refinements in surgical technique, the overall incidence of posttonsillectomy hemorrhage cited in the literature ranges from 0.1% to 9.3%.4-12 Primary posttonsillectomy hemorrhage is defined as bleeding that occurs within the first 24 hours of surgery, whereas secondary hemorrhage occurs after the first 24 hours. Whether primary or secondary, any bleeding can be lifethreatening, especially in young children. Several studies in the past decade have evaluated potential risk factors such as surgical technique, volume of intraoperative blood loss, hematologic parameters, and postoperative blood pressure.5-15 Although factors such as intraoperative blood loss volume and recent viral illness have been postulated to be associated with primary postoperative hemorrhage, neither factor has been proved to be statistically significant in the identification of patients at risk for posttonsillectomy hemorrhage.4,5 Approximately 400 tonsillectomies, with or without adenoidectomies, are performed annually at MayoRochester (Table 1). This large volume facilitates a study of the incidence of posttonsillectomy hemorrhage, as well as a powerful statistical analysis of potential risk factors. Both staff and residents participate in these procedures, and variations in technique allow random sampling for assessment of multiple potential risk factors. We reviewed our experience with posttonsillectomy hemorrhage during a recent 13-year period with specific attention to the incidence of posttonsillectomy hemorrhage, the identification of potential risk factors, and the assessment of the safety of ambulatory tonsillectomy.

onsillectomy, with or without adenoidectomy, remains one of the most commonly performed pediatric surgical procedures. As cost containment continues to influence

METHODS AND MATERIAL Subjects

From the Department of Otorhinolaryngology, Mayo Clinic. Presented at the Annual Meeting of the American Academy of Otolaryngology–Head and Neck Surgery, New Orleans, LA, September 26-29, 1999. Reprint requests: Julie L. Wei, MD, Department of Otorhinolaryngology, Mayo Clinic, 200 First St SW, Rochester, MN 55905. Copyright © 2000 by the American Academy of Otolaryngology– Head and Neck Surgery Foundation, Inc. 0194-5998/2000/$12.00 + 0 23/1/107454 doi:10.1067/mhn.2000.107454

The Mayo-Rochester Surgical Information Recording System identified a total of 4892 tonsillectomies, with or without other procedures, performed from January 1, 1985, to December 31, 1997. From these, we excluded a total of 230 patients. In 225 patients, tonsillectomy was performed as part of uvulopalatopharyngoplasty or in conjunction with septoplasty. Five patients were excluded because of the diagnosis of tonsil cancer. The exclusion criteria resulted in a database of 4662 patients, and 105 patients with posttonsillectomy hemorrhage 229

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Table 1. Number of tonsillectomies and incidence of postoperative hemorrhage Year

No. of tonsillectomies

1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 TOTAL INCIDENCE

254 304 354 371 363 379 348 348 386 333 441 442 344 4667 4662*

Table 2. Patient characteristics and procedurerelated variables

No. of bleeding episodes (%)

4 (1.6) 8 (2.6) 6 (1.7) 8 (2.2) 9 (2.5) 8 (2.1) 5 (1.4) 6 (1.7) 10 (2.6) 5 (1.5) 6 (1.4) 12 (2.7) 3 (0.9) 90 (1.93) 90 (1.93)

*From 4892, 225 patients were excluded for concomitant uvulopalatopharyngoplasty or septoplasty procedures, resulting in 4667 patients. Five patients with tonsil cancer were also excluded; therefore n = 4662.

were identified. From the 105 patients, 1 patient was excluded because tonsillectomy was performed for control of spontaneous tonsil hemorrhage attributable to von Willebrand’s disease; this patient did not have posttonsillectomy hemorrhage. On review 14 patients were found not to have posttonsillectomy hemorrhage (false-positive results). Therefore a total of 90 patients with posttonsillectomy hemorrhage were included in this study, and each episode of posttonsillectomy bleeding was confirmed by emergency trauma unit medical record documentation. No cases of postadenoidectomy bleeding were included. Of the 90 patients with posttonsillectomy hemorrhage, 63 (90%) had tonsillectomy only, 21 (23%) had adenotonsillectomy, and 6 (7%) had myringotomy and tympanostomy tube placement with adenotonsillectomy (Table 2). An optimal matching algorithm was used to cull 180 control subjects from the remaining 4557 cases. For each patient with posttonsillectomy hemorrhage, we identified 2 sexmatched controls with age differences of less than 1 year. Study data included patient characteristics, procedure-related variables, postprocedure variables (Tables 2 and 3), vital signs at the time of emergency trauma unit evaluation, and immediate management strategy. For patients with multiple episodes of posttonsillectomy hemorrhage, data were collected for each episode.

Cases (n = 90)

Controls (n = 180)

P value

Sex Male 52 (58%) 104 (58%) Female 38 (42%) 76 (42%) 1.00 Preoperative diagnosis Chronic tonsillitis 53 (59%) 101 (56%) Airway obstruction 25 (28%) 47 (26%) Chronic tonsillitis and 5 (6%) 23 (13%) airway obstruction Peritonsillar abscess 7 (8%) 9 (5%) 0.27 Procedure Tonsillectomy 63 (70%) 110 (61%) T&A 21 (23%) 56 (31%) Myringotomy, tube, T & A 6 (7%) 14 (8%) 0.35 Bismuth Yes 23 (26%) 40 (22%) No 67 (74%) 140 (78%) 0.54 Method Needle point cautery 37 (41%) 70 (39%) Bipolar 6 (7%) 6 (3%) Cold knife 47 (52%) 102 (57%) Laser 0 (0%) 1 (1%) 0.55 Injection Yes 16 (18%) 35 (20%) No 74 (82%) 144 (80%) 0.7 Antibiotics Yes 66 (80%) 127 (74%) No 16 (20%) 44 (26%) 0.28 Ketorolac (intraoperative or during recovery) Yes 1 (1%) 2 (1%) No 61 (73%) 120 (67%) No, but other (Demerol, 22 (26%) 56 (32%) 0.76 morphine, etc) Age (y) Mean (SD) 14.6 (10.0) 14.5 (10.1) Range 2-41 2-42 0.87 Preoperative systolic BP (mm Hg) Mean (SD) 110.4 (14.1) 109.9 (15.8) Range 80-150 78-162 0.73 Preoperative diastolic BP (mm Hg) Mean (SD) 68.0 (9.2) 67.5 (11.5) Range 50-90 40-110 0.64 Intraoperative fluids (mL) Mean (SD) 511.1 (306.4) 509.3 (325.9) Range 50-1500 50-1600 0.78 Intraoperative blood loss (mL) Mean (SD) 59.9 (85.4) 54.9 (65.7) Range 1-700 0-400 0.61 T & A, Tonsillectomy and adenoidectomy; BP, blood pressure.

Statistical Analysis Procedure-related variables and postprocedure variables were compared among cases and controls with Fisher’s exact test for categorical variables and the Wilcoxon rank sum test for continuous variables. A P value of less than 0.05 was considered statistically significant.

RESULTS

From January 1, 1985, through December 31, 1997, a total of 4662 patients who underwent tonsillectomy with or without adenoidectomy met the criteria for this

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Table 3. Postprocedure variables Cases (n = 90)

Controls (n = 180)

Postoperative status Outpatient 34 (38%) 76 (42%) 23-hr observation 37 (42%) 71 (39%) Admit 18 (20%) 33 (18%) Postoperative analgesic Tylenol + codeine elixir 67 (75%) 143 (80%) Tylenol + codeine tabs 6 (7%) 6 (3%) MSO4, Darvon, other narcotics 5 (6%) 9 (5%) Tylenol 8 (9%) 17 (10%) Combinations of the above 3 (3%) 4 (4%) Postoperative systolic BP (mm Hg) Mean (SD) 127.1 (16.4) 125.1 (14.7) Range 90-170 88-174 Postoperative diastolic BP (mm Hg) Mean (SD) 75.1 (11.8) 73.9 (9.9) Range 50-102 48-110

P value

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Table 4. Surgical method preference between 1985 and 1997 Cases (n = 90)

Controls (n = 179)*

Method

19851992

19931997

19851992

19931997

Needle point monopolar Forceps monopolar Cold knife

7 3 44

30 3 3

17 4 93

53 2 9

0.82

*Data

for surgical method were not available in 2 controls.

0.69

0.16

0.46

BP, Blood pressure; MSO4 , morphine sulfate.

study. Posttonsillectomy hemorrhage was identified in 90 cases, resulting in an overall incidence of posttonsillectomy bleeding of 1.93% (Table 1). For the 90 index cases, patient characteristics and procedure-related variables are presented in Table 2. Fifty-two patients were male, and 38 were female. Ages ranged from 2 to 41 years (mean 14.6 years). The incidence of posttonsillectomy hemorrhage in this series was 1.93%. The only variable found to be statistically significant was age, with a higher incidence of posttonsillectomy hemorrhage in patients older than 20 years, as reported in previous studies.8,11,12,16 Our experience demonstrated that 42 of 90 (47%) patients with posttonsillectomy hemorrhage required a second general anesthetic for hemorrhage control. Although 8% of bleeding patients and 5% of controls had histories of previous peritonsillar abscess, this factor did not prove to be statistically significant. Only 1 patient had primary hemorrhage in our series. Recurrent pharyngotonsillitis and chronic upper airway obstruction were the 2 most common surgical indications for both index cases and controls. Most procedures were tonsillectomy alone (70% of cases, 61% of controls), followed by tonsillectomy and adenoidectomy (23% of cases, 31% of controls) and finally tonsillectomy and adenoidectomy with ventilation tube placement (7% of cases, 8% of controls). No statistical significance was found in these procedure-related variables (P = 0.27). Cold-steel dissection (knife dissection with No. 10 or No. 15 blade) was the surgical technique in more than 50% of patients for both cases and controls. Needle-point monopolar electrodissection was used in

40% of patients in both groups. Forceps monopolar cautery, with or without the use of an operating microscope, was used in 3% of controls and 7% of cases. No statistical significance was found for surgical technique (P = 0.55) (Table 4). Intraoperative blood loss averaged 60 mL for cases and 55 mL for controls. Intraoperative blood loss averaged 70 mL with cold dissection, 27 mL with needlepoint electrocautery dissection, and 19 mL with forceps monopolar electrodissection. Although cold-knife tonsillectomy resulted in higher intraoperative blood loss, this technique was not associated with an increased incidence of posttonsillectomy hemorrhage. No statistical significance was found for the volume of intraoperative blood loss or intravenous fluid replacement (P = 0.61 and P = 0.78, respectively). Intraoperative peritonsillar injection of local anesthetic, with or without epinephrine, was used in approximately 20% of patients. This variable had no statistical significance (P = 0.73). In approximately 25% of cases and controls, bismuth subgallate was painted on the tonsillar fossae, and this variable had no statistical significance (P = 0.54). Perioperative antimicrobial therapy was used in 80% of cases and 74% of controls, and this variable had no statistical significance (P = 0.28). Preoperative blood pressure and the highest recorded postoperative systolic and diastolic blood pressures were not statistically significant factors (Tables 2 and 3). Seventy-five percent of cases and 80% of controls received postoperative oral analgesics in the form of acetaminophen with codeine (tablet or elixir). Approximately 10% of both cases and controls received only acetaminophen without narcotic analgesic. Only 1 patient in the case group and 2 patients in the control group received postoperative ketorolac for analgesia. The administration of narcotics was not statistically significant (P = 0.76), and our data are not sufficient to support an association between ketorolac and postoperative hemorrhage.

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Fig 1. Trend in inpatient versus outpatient surgeries from 1985 to 1997.

Table 5. Presentation of posttonsillectomy bleeding by postoperative day Postoperative day

No. of patients

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 23

1 3 4 2 2 13 16 12 5 6 8 3 7 2 4 1 1 1

Table 6. Distribution of bleeding presentation by postoperative day for patients with multiple bleeding episodes Postoperative day

Some patients had multiple episodes; the above data represent the first episodes of bleeding.

Postprocedure variables are presented in Table 3. Approximately 40% of patients in both groups were outpatients, and 40% of patients in both groups were admitted for 23-hour observation. Twenty percent of patients were admitted for more than 24 hours. Ambulatory tonsillectomy was not associated with an increase in the incidence of posttonsillectomy hemorrhage (Fig 1). Only 1 patient had a primary hemorrhage. Posttonsillectomy hemorrhage occurred most commonly on postoperative day 6 (16/90), followed by days 5 (13/90) and 7 (12/90) (Table 5 and Fig 2). Delayed postoperative bleeding presented as late as 23 days after surgery

2 episodes 0, 1 5, 7 6, 9 6, 10 6, 12 7, 10 7, 11 10, 11 3 episodes 1, 6, 10 6, 9, 15 4 episodes 7, 11, 15, 19

No. of patients

1 1 1 1 1 1 1 1 1 1 1

(Table 5). Eleven of 90 (12%) patients with posttonsillectomy hemorrhage had subsequent bleeding episodes, usually 3 to 4 days after the first episode. Two patients had 3 episodes, and 1 patient had 4 episodes (Table 6). Full hematologic evaluation of this patient did not reveal a coagulopathy, and subsequent elective carotid angiography did not identify any aberrant vascular anatomy. Age was the only risk factor found to be statistically significant for posttonsillectomy hemorrhage (P = 0.0071, Table 7). The highest incidence of posttonsillectomy hemorrhage occurred in patients 21 to 30 years of age (3.61%), followed by those 11 to 20 years of age (2.48%). Patients younger than 10 years had an incidence of posttonsillectomy hemorrhage similar to that of those older than 30 years, 1.46% and 1.59%, respectively.

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Fig 2. Presentation of posttonsillectomy hemorrhage by postoperative day.

Management strategies for posttonsillectomy hemorrhage included observation, hydration, and silver nitrate chemocauterization or electrocauterization, with subsequent same-day discharge in 53% of cases. Significant active bleeding led to immediate operative intervention in 19% of cases. However, regardless of the initial management, 42 of 90 (47%) patients with posttonsillectomy hemorrhage ultimately required a second general anesthetic for hemorrhage control. DISCUSSION

Our goals for this study were to identify the incidence of posttonsillectomy hemorrhage, to evaluate potential risk factors, and to assess the safety of ambulatory tonsillectomy. Although these issues have been addressed previously in numerous studies, controversy lingers regarding the efficacy of preoperative hemostatic assessment, as well as the existence of specific factors that may identify those patients at risk for posttonsillectomy hemorrhage.1-12,15-22 Routine preoperative screening of coagulation parameters is not performed at our institution. Our data support the safety of ambulatory tonsillectomy,1-5 and our 1.93% incidence of posttonsillectomy bleeding compares favorably with findings of other contemporary reviews, which have reported figures from 0.1% to 9.3%.4-12 We found age to be the only risk factor statistically significant for posttonsillectomy hemorrhage. Akkielah et al13 performed a prospective trial comparing bipolar and monopolar electrodissection tonsillectomy, with each patient serving as his or her own control. Although pain seemed less on the side treated with monopolar electrodissection, no conclusions were made regarding postoperative hemorrhage. A prospec-

Table 7. Distribution of posttonsillectomy hemorrhage by age Age (y)

0-10 11-20 21-30 >30 TOTAL

Controls

2632 983 508 434 4557

Cases

39 25 19 7 90

Total

%

2671 1008 527 441 4647*

1.46 2.48 3.61 1.59 —

χ2 12.807, P = 0.0071 *Controls did not include the 105 patients initially identified with posttonsillectomy hemorrhage (4662 – 105 = 4557). From 105, 15 were excluded on review because of false-positive results, leaving 90 cases of posttonsillectomy hemorrhage.

tive study by Kujawski et al14 did not show any statistical significance between microsurgical bipolar electrodissection and traditional cold dissection tonsillectomy with regard to hemorrhage, although postoperative pain was less for the bipolar group. In this series coldknife tonsillectomy resulted in higher intraoperative blood loss compared with needle-point or forceps monopolar electrodissection. However, neither surgical technique nor volume of intraoperative blood was found to be statistically significant. Ketorolac, a nonsteroidal anti-inflammatory drug, has gained popularity as an analgesic because of its lack of respiratory depression and possible lack of emesis center provocation.23 The use of ketorolac perioperatively has been shown to be associated with an increased incidence of posttonsillectomy hemorrhage.23-26 As a nonsteroidal anti-inflammatory drug, ketorolac prolongs bleeding time by inhibiting thromboxane A2 production as well as platelet aggregation. In a review by

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Judkins et al,23 58 of 311 tonsillectomy patients received intraoperative ketorolac. The ketorolac recipients had an overall postoperative bleeding incidence of 17%, much higher than the 4.4% incidence in the remaining 253 patients who received an opioid analgesic. Gunter et al24 performed a prospective study of recovery and complications in ketorolac and morphine recipients in pediatric tonsillectomy. Their study was terminated after 97 cases because of an increased incidence of primary hemorrhage in the ketorolac recipients. Splinter et al25 reported a similar incidence of postoperative emesis in patients receiving ketorolac or codeine, but a higher incidence of perioperative bleeding in the ketorolac group. Rusy et al26 compared ketorolac and acetaminophen for analgesia and bleeding in 50 patients ranging in age from 2 to 15 years. They found that ketorolac was no more effective than high-dose rectal acetaminophen for analgesia, but intraoperative hemostasis was more difficult in patients receiving ketorolac. Although our data are insufficient to support an association of ketorolac with perioperative hemorrhage, the experiences of others point to a significant association of ketorolac with postoperative hemorrhage.23-26 In a study by Tami et al,16 no difference in platelet counts between patients with and without perioperative bleeding was reported. However, statistically more patients with perioperative bleeding had prolonged prothrombin times (PTs) or partial thromboplastin times (PTTs) before surgery. In a review of 1061 children undergoing adenotonsillectomy, Kang et al17 advocated the use of preoperative bleeding time and PTT. Manning,18 however, disagreed with that practice recommendation because, of the 27 patients identified with initial abnormal clotting values, 17 were found to have no coagulopathy on further investigation, and only 1 of the remaining 10 patients had posttonsillectomy hemorrhage; 2 of the patients did not have further workup.18 Bolger et al19 reviewed preoperative hemostatic evaluations of 52 adenotonsillectomy patients. All patients had normal platelet counts, but 5.8% had prolonged PTs, 11.5% had prolonged PTTs, and 9.6% had prolonged bleeding times. Ultimately, 6 of 52 (11.5%) were considered to have true coagulopathy. On the basis of the findings the authors recommended comprehensive laboratory screening tests to identify platelet dysfunction and von Willebrand’s disease. After reviewing 994 adenotonsillectomy cases and the usefulness of preoperative PT/PTT screening, Manning et al20 concluded that these tests had no predictive value for surgical bleeding. Thomas and Arbon21 evaluated the effectiveness of preoperative PTT screening for potential bleeding dyscrasias and identified no abnormalities, even

among patients who bled after surgery. Howells et al15 reviewed 382 patients undergoing tonsillectomy and concluded that preoperative PT/PTT provides no more useful information than a good bleeding history and should be done in only select cases. At our institution, a screening profile including PT, PTT, bleeding time, and complete blood and platelet counts currently costs about $150 per patient. We do not believe that routine preoperative coagulation profiles are cost-effective in predicting risk of postoperative bleeding. In our review, once a patient had posttonsillectomy hemorrhage, there was a 12% incidence of a subsequent bleeding episode. This contrasts with the experience of Kang et al,17 who reported no additional episodes in 64 patients. We believe that once a patient is identified and treated for posttonsillectomy hemorrhage, follow-up is important in anticipation of a possible second episode. Patients should be warned to avoid physical exertion and to continue a soft diet during the perioperative period. Once posttonsillectomy hemorrhage is identified, we do not routinely perform coagulation studies absent of an unusual circumstance, such as repeated episodes of bleeding requiring more than one admission postoperatively or hemostasis requiring more than 1 general anesthesia posttonsillectomy. One such patient, who had 4 episodes of bleeding, had a normal hematologic workup and a subsequent carotid angiogram, which was negative for aberrant vascular anatomy. Myssiorek and Alvi22 reviewed a group of 1138 patients and concluded that older age (>10 years), history of chronic tonsillitis, excessive intraoperative blood loss, and elevated postoperative mean arterial pressure are significant risk factors for posttonsillectomy hemorrhage. Our data demonstrate that the highest incidence of bleeding occurred in patients 21 to 30 years of age, followed by patients 11 to 20 years of age, and age was the only factor found to be statistically significant. One shortcoming of this retrospective study was the inability to define why older patients have a higher risk of posttonsillectomy hemorrhage. Potential contributing factors may include (1) a technically more challenging dissection through areas of fibrosis from prior episodes of infection and (2) premature resumption of normal daily routines after surgery. Future prospective studies may help to more accurately determine the significance of these factors. CONCLUSIONS

Although numerous studies1,5,8,11,12,16,22 have suggested that certain factors may predispose to posttonsillectomy bleeding, few if any have been consistently found to be statistically significant. Taking into account the variables in perioperative management and surgical

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techniques, we believe our postoperative hemorrhage rate of 1.93% is acceptable. Although variations in management may influence short-term factors during convalescence, tonsillectomy remains a safe procedure. We believe that the compulsive laboratory pursuit of potential risk factors for posttonsillectomy hemorrhage is of limited use, but previously diagnosed coagulopathies mandate preoperative management. We acknowledge our inability to accurately predict which patients will experience postoperative hemorrhage. We believe that it is still the surgeon’s responsibility to minimize surgical trauma, achieve absolute hemostasis, and then manage the postoperative course on an individual basis. If postoperative bleeding occurs, it must be evaluated promptly and managed aggressively, especially in children. Both the surgeon and the patient must be aware of the potential for a second episode of posttonsillectomy bleeding. We thank Hongzhe Li, PhD, and James Kuiper, MS, for helping with the study design and performing the statistical analysis of all data. REFERENCES 1. Rakover Y, Almog R, Rosen G. The risk of postoperative haemorrhage in tonsillectomy as an outpatient procedure in children. Int J Pediatr Otorhinolaryngol 1997;41:29-36. 2. Gabalski EC, Mattucci KF, Setzen M, et al. Ambulatory tonsillectomy and adenoidectomy. Laryngoscope 1996;106:77-80. 3. Moralee SJ, Murray JAM. Would day-case adult tonsillectomy be safe? J Laryngol Otol 1995;109:1166-7. 4. Schloss MD, Tan AKW, Schloss B, et al. Outpatient tonsillectomy and adenoidectomy: complications and recommendations. Int J Pediatr Otorhinolaryngol 1994;30:115-22. 5. Tan AK, Rothstein J, Tewfik TL. Ambulatory tonsillectomy and adenoidectomy: complications and associated factors. J Otolaryngol 1993;22:442-6. 6. Irani DB, Berkowitz RG. Management of secondary hemorrhage following pediatric adenotonsillectomy. Int J Pediatr Otorhinolaryngol 1997;40:115-24. 7. Randall DA, Hoffer ME. Complications of tonsillectomy and adenoidectomy. Otolaryngol Head Neck Surg 1998;118:61-8. 8. Roberts C, Jayaramachandran S, Raine CH. A prospective study of factors which may predispose to postoperative tonsillar fossa haemorrhage. Clin Otolaryngol 1992;17:13-7.

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9. Handler SD, Miller L, Richmond KH. Post-tonsillectomy hemorrhage: incidence, prevention, and management. Laryngoscope 1986;96:1243-7. 10. Schroeder WA. Post tonsillectomy hemorrhage: a ten-year retrospective study. Missouri Med 1996;92:592-5. 11. Chowdhury K, Tewfik TL, Schloss MD. Post-tonsillectomy and adenoidectomy hemorrhage. J Otolaryngol 1988;17:46-9. 12. Carmody D, Vamadevan T, Cooper SM. Post tonsillectomy hemorrhage. J Otolaryngol Otol 1982;96:635-8. 13. Akkielah A, Kalan A, Kenyon GS. Diathermy tonsillectomy: comparison of morbidity following bipolar and monopolar microdissection needle excision. J Laryngol Otol 1997;111:7358. 14. Kujawski O, Dulguerov P, Gysin C, et al. Microscopic tonsillectomy: a double-blind randomized trial. Otolaryngol Head Neck Surg 1997;117:641-7. 15. Howells RC II, Wax M, Ramadan H. Value of preoperative prothrombin time/partial thromboplastin time as a predictor of postoperative hemorrhage in pediatric patients undergoing tonsillectomy. Otolaryngol Head Neck Surg 1997;117:628-32. 16. Tami TA, Parker GS, Taylor RE. Post-tonsillectomy bleeding: an evaluation of risk factors. Laryngoscope 1987;97:1307-11. 17. Kang J, Brodsky L, Danziger I, et al. Coagulation profile as a predictor for post-tonsillectomy and adenoidectomy (T + A) hemorrhage. Int J Pediatr Otorhinolaryngol 1994;28:57-165. 18. Manning SC. Re: Coagulation profile as a predictor for post-tonsillectomy and adenoidectomy (T + A) hemorrhage [letter]. Int J Pediatr Otorhinolaryngol 1995;32:261-3. 19. Bolger WE, Parsons DS, Potempa L. Preoperative hemostatic assessment of the adenotonsillectomy patient. Otolaryngol Head Neck Surg 1990;103:396-405. 20. Manning SC, Beste D, Mcbride T, et al. An assessment of preoperative coagulation screening for tonsillectomy and adenoidectomy. Int J Pediatr Otorhinolaryngol 1987;13:237-44. 21. Thomas GK, Arbon RA. Preoperative screening for potential T & A bleeding. Arch Otolaryngol 1970;91:453-6. 22. Myssiorek D, Alvi A. Post-tonsillectomy hemorrhage: an assessment of risk factors. Int J Pediatr Otorhinolaryngol 1996;37:3543. 23. Judkins JH, Dray TG, Hubbell RN. Intraoperative ketorolac and post-tonsillectomy bleeding. Arch Otolaryngol 1996;122:937-40. 24. Gunter JB, Varughese AM, Harrington JF, et al. Recovery and complication after tonsillectomy in children: a comparison of ketorolac and morphine. Anesth Analg 1995;81:1136-41. 25. Splinter WM, Rhine EJ, Roberts DW, et al. Preoperative ketorolac increases bleeding after tonsillectomy in children. Can J Anesth 1996;43:560-3. 26. Rusy LM, Houck CS, Sullivan LJ, et al. A double-blinded evaluation of ketorolac tromethamine versus acetaminophen in pediatric tonsillectomy analgesia and bleeding. Anesth Analg 1995; 80:226-9.