Blood Loss During Periodontal Flap Surgery
12
B e r d o n published the first report on hemorrhage during periodontal surgery. Using a cyanmethemoglobin comparison technique, he measured blood loss dur ing 50 gingivectomies involving a surgical field of 5 to 14 teeth. H e established that approximately 5 ml to 149 ml of blood was lost. The quantity of hemorrhage from two patients undergoing full-mouth gingivecto mies under a general anesthetic was also measured and found to be 435 ml and 624 ml respectively. Observa tion and supportive therapy was recommended for those patients with the "higher volume" of blood loss. N o specific guidelines for fluid replacement were rec ommended, however.
by DAVID A . B A A B , D.D.S., M.S.D.* WILLIAM F . AMMONS, JR., D . D . S . , M.S.D.* HERBERT SELIPSKY, B.D.S., H . D . D . ,
1
M c l v o r and Wengraf studied blood loss colorimetrically during gingivectomies and/or isolated periodontal flap procedures on 14 patients. Three patients had small, one- or two-tooth, mucoperiosteal flaps elevated and osteoplasty performed. B l o o d loss for these three patients ranged from 12 ml to 62 m l , while the other patients lost 0.7 ml to 18 ml of blood during gingivecto mies. Based upon this data, they speculated that one could expect a 10-fold increase in blood loss per tooth during a periodontal flap procedure as compared to a gingivectomy. The reasons given were that more com plex procedures involving flaps take longer and expose highly vascular bone, resulting in greater blood loss.
M.S.D.* HEMORRHAGE ASSOCIATED with surgery is a common problem which requires proper management. This in cludes accurate determination of blood loss, establish ment of effective hemostasis, and replacement of fluids when indicated. Surgery has become commonplace in the treatment of the periodontal patient. A flap approach is com monly used to allow the exposure and correction of periodontal defects. Although such surgery may be routine, little attention has been directed to the extent of hemorrhage occuring during this type of procedure. A literature search indicates that only one study has attempted, on a limited basis, to measure the amount of blood lost by patients undergoing periodontal flap surgery. It is important, therefore, to investigate the blood loss associated with periodontal flap surgery.
Full-mouth periodontal flap procedures performed under general anesthesia were estimated to result in a blood loss of 350 ml by Ariaudo in 1 9 7 0 . The meth odology was not described in that paper. Recently Hecht and A p p measured blood loss dur ing standardized gingivectomies of mandibular poste rior segments. When local gingival infiltration was used, blood loss ranged from 3 ml to 13 m l , while 8 ml to 31 ml were lost when mandibular block anesthesia was used. Clinicians have long recognized that hemorrhage varies significantly between patients, and within the same patient at various t i m e s . This variation has been attributed to systemic factors, local factors, and surgical technique. Certain systemic factors such as age, blood pressure and bleeding times, within the range of normal, have not been shown to be related to blood l o s s . Hemophiliacs, when controlled with factor V I I I cryoprecipitate, lost less blood than normal patients dur ing oral surgical procedures in one study. It is inter esting, however, that a relationship between blood loss and sex may exist, since males appear to lose blood 5 0 % faster than females during gingival surgery. Johnson, however, states that there is no such rela tionship during oral surgical procedures. A series of local factors have been enumerated which may affect the amount of surgical hemorrhage. The duration of the surgery appears to influence total blood loss, although a statistically significant relation ship has not been established. The use of epinephrine in the local anesthetic has been shown to decrease
1
13
1 4
REVIEW OF THE LITERATURE
Definitive data regarding surgical blood loss was un available until 1924. Prior to this time, surgeons had relied on physical signs such as skin color and pulse rate to indicate impending shock. Gatch and Little in 1924 first studied operative hemorrhage during general sur gery. These investigators estimated the range of values for the operative blood loss associated with 30 common surgical procedures. In the succeeding half-century, numerous investigators have established the extent of blood loss for a variety of general surgical proce dures. The blood loss associated with oral surgery was first measured by Gores, Royer and M a n n in 1955. They found that patients undergoing full-mouth odontectomies under general anesthesia lost 5 ml to 771 ml of whole blood. This value equaled or exceeded the blood loss which occurred during many major surgical opera tions. Other similar s t u d i e s reported blood loss ranging from 35 to 912 m l . Rhymes and Williams reported that patients lost 32 ml to 520 ml while un dergoing full-mouth odontectomies with local anesthe sia. 2
1 , 5 , 1 5
9 , 1 0 , 1 2 , 1 3 , 1 5
3-7
8
16
12
9
9,10
11
9,11, 1 2
* Department of Periodontics SM-44 University of Washington, School of Dentistry, Seattle, Wash 98105.
693
694
J. Periodontal. November, 1977
Baab, Amnions, Selipsky 8,17
blood loss during full-mouth extractions, although Meyer and A l l e n reported normal saline to be equally effective in reducing blood loss. In addition, postopera tive blood loss associated with the use of epinephrine was shown to be significantly greater than that found after the use of neosynephrine. Local infiltration of 2 % lidocaine with 1:100,000 epinephrine reduced bleeding significantly during gingivectomy when com pared with block anesthesia using the same anes thetic. The extent of the surgical field also appears to influence the volume of blood l o s t . The degree of inflammation in the periodontal tissues is claimed by some to affect blood loss during full-mouth odontectomy. T o date, no study has ascertained the effects of these variables on blood loss during peri odontal flap surgery. The purpose of this study was to measure the amount of surgical blood loss in patients undergoing periodon tal flap surgery. In addition, such factors as duration, amount of anesthetic, number of teeth in the surgical field, length of incision, blood pressure, and level of inflammation in the gingival sulcus, were evaluated for their effects on operative hemorrhage. 1 5
15
14
1,9
9 , 1 0 , 1 8
MATERIALS AND M E T H O D S
Thirty patients who were to undergo 39 periodontal flap procedures were selected from patients at the University of Washington School of Dentistry. The following criteria were used for patient selection: 1. There were no medical contraindications to the surgery. 2. The area of surgery included at least 4 posterior teeth, including canines. 3. Initial therapy, consisting of root planing, occlu sal adjustment, oral hygiene instructions was completed at least 3 weeks prior to the surgery. 4. N o intravenous sedation or inhalation analgesia was used during the surgery. 5. Periodontal flap surgery could include either flap curettage, bone recontouring and/or osseous coagulum grafts. In addition to the Health History Review in the patient's chart, a brief questionniare was completed by the patient prior to surgery. Such questions as, "Have you ever had prolonged bleeding following a tooth extraction?" and, "Have you taken aspirin in the last 24 hours?" were asked, to ensure that the bleeding status of the patient was recorded. Additional preoperative data including blood pres sure, location and number of teeth, length of the incision and sulcular inflammation index were re corded. A 0.5 mm diameter periodontal probe cali brated to deliver a standard pressure of 5 g, as de scribed by R o l f s , was used to gently probe the gingival sulcus at six points around each tooth involved in the surgery. The number of bleeding points divided by the total number of points probed was used as an index of
the inflammatory state of the gingival sulcus. The length of the incision was estimated by tracing the incision on the patient's models with a linear mapmeasuring device.* A 5 ml sample of whole blood was drawn from the patient's median cubital vein just prior to the start of surgery and set aside for colorimetric analysis. A l l surgical procedures were performed by eight graduate students, and one faculty member ( W . F . A . ) . Lidocaine 2 % with 1:100,000 epinephrine was used in all cases. Both block and infiltration injections into the depth of the vestibule were used. The volume of anesthetic was recorded to the nearest carpule (1.8 ml) and the time of the initial incision was recorded at the start of the procedure. In all surgeries, an inversebevel, scalloped incision was made, the coronal gingiva was thinned, and full thickness flaps were then elevated to expose the bone in the surgical site. Thorough hard and soft tissue debridement was accomplished using sharp curettes. Bone recontouring was performed in 34 surgeries using rotary instruments for osteoplasty, and hand instruments for ostectomy. The severity of the defects in a further 5 surgeries dictated the per formance of flap curettage. Continuous sling sutures were used in all cases to adapt the flaps to the crest of the marginal bone. A portable aspirator and 2 x 2 sterile gauze sponges were used to collect blood during the procedure. The patient was repeatedly cautioned to avoid swallowing during the procedures. B l o o d and saliva were suctioned as efficiently as possible using good retraction. When suturing was completed the time was again recorded. Postoperative blood pressure was recorded before the patient was dismissed. A l l instruments, hoses, suction tips, and 2 x 2 sponges were washed in a container with water, and the solution was poured into the aspirator jar. Blood loss was measured using the cyanmethemoglobin comparison technique. The concentration of he moglobin (Hb) in the aspirated blood was measured at 540 nm using a Coleman Jr. spectrophotometer.! The blood loss was calculated by comparing the concentra tion of H b in the patient's whole blood with the concentration of H b in aspirated blood times the volume of aspirated blood. The formula used is as follows: 6
U p o n completion of the surgical procedure, the surgeon was asked to estimate the blood loss in order to allow comparison with the measured value. A l l data were entered on computer cards and ana lyzed statistically using the Pearson correlation coeffi-
19
* Recreational Equipment, Inc., 1525 11th Ave., Seattle, Wash 98122. t Coleman Instrument Division of Perkin-Elmer Corp., Maywood, IL 60153.
Volume 48 Number 11
Blood Loss 695
cient and the Student's t test to evaluate and test relationships between measured variables and blood loss. A multiple stepwise regression analysis with resid uals was performed in an effort to isolate which of the measured factors contributed the most to the variation in blood loss.
variation in the volume of blood lost per surgical site, from 16 m l to 592 m l . In addition, blood loss in patients undergoing more than one area of periodontal flap surgery on different days approximately 1 month apart varied greatly. Table III summarizes this data. Patient N o . 2 showed the largest range, 50 ml to 592 ml. Those patients undergoing surgery in two different areas of the mouth during the same day showed a maximum variation in blood loss of 36 m l . There was one episode of adverse side effects attrib utable to surgical hemorrhage. A 56-year-old male, undergoing two periodontal flap procedures on the same day, lost a total of 720 ml of blood. A t the end of the procedures, his blood pressure had dropped considerably and he was experiencing orthostatic hy potension. The patient was treated postoperatively with 500 ml of intravenous balanced salt solution over a period of 1 hour and he responded well. Such factors as degree of sulcular inflammation, length of the incision, number of teeth and units of teeth did not significantly affect the volume of blood
RESULTS
Thirty-nine posterior flap procedures were done on 30 patients over a period of 6 months. Table I summa rizes the data obtained for the different variables measured during the procedures. Correlation (r) values and probability ( P ) values for each of the variables tested against blood loss are also shown in Table I. The effect of the patient's sex, location of the surgery, type of surgery, and aspirin intake can be seen in Table II. A sample size of 30 was used when reporting measured variables per patient, but a sample size of 39 was used when reporting blood loss values per surgical procedure. A s can be seen in Table I, there was a great deal of T A B L E I. Summaryof
Variable
Mean*
Surgical blood loss (ml) Duration of procedure (min) No. of teeth in surgical field No. of units in surgical field Length of incision (from models) (cm) Volume of anesthetic (carpules) Inflammation index Blood pressure Preoperative Postoperative
Measured Variables
SD*
SE*
Range*
134.4 151.8
114.3 52.2
20.9 9.5
16-592 51-255
0.44
0.002
5.5
1.6
0.30
4-13
0.02
0.46
7.3
1.8
0.33
5-16
0.07
0.33
12.4
3.1
0.57
4.5-27.5
0.25
0.06
4.4
2.0
0.36
2-10
0.48
0.001
0.15
0.40
0.65 1.77
0.00 0.33
0.13
0.20
119/72 123/77
19/14 21/13
3/2 4/2
100-180/60-100 100-180/60-105
0.26 0.31
0.04 0.02
r value P value
* N = 30. T A B L E II. Sex, Area,
Other variables Sex* Females Males Area of surgeryt Upper right Upper left Lower left Lower right Type of surgeryt Flap Curettage Osseous surgery Prior aspirin intake (24 hours)t No aspirin intaket * N = 30. † N = 39.
N
Average blood loss (S.D.)
Type of Surgery, and Aspirin Intake Range
Average blood loss per tooth (SD)
Average blood loss per minute (SD)
19 11
121.7 ( ± 1 1 6 ) 156.4 ( ± 1 1 3 )
15.6-449.4 35.4-591.6
24.2 ( ± 2 3 . 4 ) 27.4 ( ± 2 2 )
7 6 10 16
121.5 109.9 136.5 160.1
(±103) (±147) (±129) (±149)
47.5-340.9 35.4-408.2 15.6-449.4 23.4-591.6
24.6 22.1 28.9 30.7
5 34 10
171.8 ( ± 1 2 6 ) 140.4 ( ± 1 4 1 ) 160.0 ( ± 1 8 8 )
56.9-340.9 15.6-591.6 15.6-591.6
38.7 ( ± 2 7 . 0 ) 26.9 ( ± 2 8 . 2 ) 31.3 ( ± 5 7 . 9 )
1.14 ( ± . 5 9 ) 0.81 ( ± . 6 3 ) 0.93 ( ± . 8 1 )
29
131.9 ( ± 1 1 0 )
23.4-449.4
25.6 ( ± 2 2 . 2 )
0.88 ( ± . 6 4 )
(±20.9) (±29.3) (±27.4) (±29.7)
.84 ( ± . 6 7 ) .98 ( ± . 6 0 )
.73 .76 .75 1.09
(±.56) (±.75) (±.59) (±.75)
t test
No Sig. Diff.
696
J. Periodontol. November, 1977
Baab, Amnions, Selipsky T A B L E III.
Patient number
Sex
1
F
2
M
3
F
4
F
5
F
6
F
7
F
Patients undergoing multiple procedures on Days Different
Procedure No. & area
Inflam, index
Number of teeth involved
(a) L L (b) L R (a) L R (b) L L (c) U R (a) L R (b) L L (a) L L (b) L R (a) U R (b) L L (a) L R (b) L L (a) L L (b) U L
0.14 0.17 0.03 0.04 0.17 0.23 0.00 0.17 0.07 0.07 0.10 0.13 0.10 0.10 0.10
6 6 5 4 6 5 5 5 5 5 5 4 5 5 5
loss in this study. There was no one variable that could be attributed to the large standard deviation in mea sured blood loss. Seven of the eight surgeons were graduate students and one was a private practitioner. The private practi tioner took an average of 12 min/tooth and his patients lost an average of 14 ml/tooth, while the graduate students took an average of 36 min/tooth and their patients lost an average of 30 ml/tooth. The surgeon's estimated blood loss was on the aver age within 57 ml of the mean measured blood loss, but there was wide variation in the amount of error ( ± 1 to 200 ml). The range of error for the more experi enced private practitioner was ± 3 to 134 m l . DISCUSSION
The accuracy of the cyanmethemoglobin comparison method used in this study for the determination of blood loss has been demonstrated by several investiga tors to be accurate within 2 to 3 % of a known volume of b l o o d . The measurements in this study were all carried out by the same investigator using standardized, hematological laboratory techniques. Possible sources of error in measurement of blood loss using the cyanmethemoglobin comparison tech nique are blood lost to the gastrointestinal system due to swallowing, and blood lost into the tissues and not recovered. A total blood volume measurement before and after surgery using one of the indirect techniques, 1 or C r , would check on our measurements and account for blood lost into the tissues or swallowed. If measurements were taken 1 or 2 days postoperatively, this method would provide us with some information as to how much net blood loss occurs postoperatively. None of the variables measured exerted significant influence upon the volume of blood lost. The amount of anesthetic used during the procedures was the 6-8
131
5 1
Surgical blood loss
ml 37.4 119.6 591.6 270.0 50.2 71.6 108.5 116.8 245.5 59.1 80.2 23.4 15.6 103.1 48.5
Surgical Du ration
ml/Tooth
ml/min.
6.2 19.9 118.3 67.5 8.4 14.3 21.7 23.4 49.1 11.8 16.0 5.9 3.1 20.6 9.8
0.53 1.75 2.47 1.80 0.63 0.44 0.48 0.68 1.56 0.30 0.41 0.46 0.26 0.57 0.49
min 71 68 240 150 193 160 223 172 157 200 195 51 60 180 100
variable most correlated with blood loss. However, this could be attributed to the necessity for using more anesthetic to control bleeding and discomfort during the longer surgeries. Duration also appeared related to blood loss, although not in a predictable manner. A s shown in Figure 1, there appeared to be two distinct groups. One group of patients lost less than 125 ml of blood regardless of the duration, while another group bled constantly at a much faster rate throughout the surgeries, losing 200 to 400 ml during 2 to 4 hours of surgery. This phenomenon did not appear to be related to any of the variables measured in this study, although all patients who lost over 200 ml of blood were operated on for over 2 hours. Therefore, one cannot predict the volume of blood lost by timing the procedure. Other factors may exert a greater influence on blood loss than duration of the procedure. However, when surgical time was kept under 2 hours, no patient lost more than 125 ml of blood. The location and type of the surgery appeared to affect blood loss, but not in a statistically significant way. F o r example, periodontal flap surgery in the mandible resulted in an average blood loss of 151 ml per segment, while the corresponding procedure in the maxilla resulted in an average blood loss of 110 ml per segment. The greatest average blood loss per segment occurred from the mandibular right posterior area, while surgery in the maxillary left posterior area re sulted in the least average blood loss per segment. This phenomenon could be explained by the fact that all therapists were right-handed, and surgical access for the right-hander is usually more difficult in the mandibular right lingual area. Two patients appeared to bleed "excessively" in this study. Bleeding work-ups were performed for these patients and all findings were within normal
Volume 48 Number 11
Blood Loss
limits. This is consistent with other reports which state that bleeding, clotting, and prothrombin times can be within normal limits in an individual who bleeds profusely. Surgeons could estimate blood loss more accurately in this study since the aspirator jar in the portable suction was visible to the surgeon at all times. Even so, there was a wide range in error. In most private offices a central vacuum is used, and one would expect an even greater degree of error in estimating blood loss. The data indicate that, on the average, a substantial amount of blood is lost during a posterior sextant of periodontal flap surgery (134 ml). But of greater importance is the fact that a wide variability (16-592 ml) may occur between patients and in the same patient. Postoperative blood loss, while not measured in this study, has been shown to be equal to, or greater than, surgical blood loss following full-mouth extrac tions. A similar phenomenon may occur following periodontal flap surgery. A healthy adult may lose up to 1 liter of blood 9,12,14
11,15
FIGURE
697
before developing hypotension, and many people fre quently donate 500 ml to a blood bank without any apparent adverse consequences. However, consid ering the possibility of postoperative oozing and blood lost into the tissues during surgery, several investigators recommend that blood losses greater than 500 ml should be replaced immediately with intravenous fluids or whole b l o o d . Balanced salt solutions do not involve as many hazards as blood transfusion and should be used for volume replacement when the loss of volume is less than 1 liter and the hemoglobin concentration is adequate. The following procedures are recommended to those periodontists operating large areas of the mouth at one sitting or operating for long time periods. Preop erative and postoperative blood pressures with the patient sitting should be taken. A postoperative stand ing blood pressure should be recorded to assess possi ble orthostatic hypotension resulting from acute blood loss. Patients experiencing a drop in systolic blood pressure in the standing position oí 20 mm H g , or a drop in diastolic blood pressure o l 10 mm H g following 20,21
8 , 9 , 2 0
21
1
698
J. Periodontal. November, 1977
Baab, Amnions, Selipsky
surgery, should be treated with balanced salt solutions intravenously until the blood pressure returns to nor m a l . A simple volumetric measurement of blood loss during periodontal flap surgery should be performed using an aspirator with a collection reservoir. The volume can be assessed by using a known volume of irrigating fluids and subtracting this from the total volume of fluid recovered. A n estimate of blood loss could thus be made, which would aid in calculating the volume of fluid replacement necessary. Intravenous fluid replacement should be performed when the patient either (a) experiences orthostatic hypotension, or (b) loses 500 ml or more of blood. Postoperative management of all periodontal surgery patients should include instructions to drink 1 to 2 liters of fluid the day of surgery and 2 days following surgery to help prevent postoperative dehydration. The combination of possible postoperative blood loss with operative hemorrage suggests that patients un dergoing multiple quadrants of periodontal flap surgery on the same day may lose as much blood as patients undergoing a major surgical operation. W e , as perio dontists, need to be more conscious of the possible sequellae and treatment of hypotension and dehydra tion resulting from surgical blood loss. This is especially true in periodontal surgery, as most patients are being treated on an outpatient basis. 21
20
SUMMARY AND CONCLUSIONS
replacement is recommended for those patients who either (a) experience orthostatic hypotension, or (b) lose 500 ml or more of blood. REFERENCES
1. Mclvor, J. and Wengraf. A . : Blood loss in periodontal surgery. Dent Pract 16: 448, 1966. 2. Gatch, W. D . , and Little, W. D.: Amount of blood lost during some of the more common operations. J Am Med Assoc 8 3 : 1075, 1924. 3. Coller, F. A . , Crook, C . E . , and lob, V . : Blood loss during surgical operations. J Am Med Assoc 126: 1, 1944. 4. Lenahan, N . E . , Spitz, I. A . , and Metealf, D . W.: Blood determinations and estimation of blood loss during surgical operations. Arch Surg 5 7 : 435, 1948. 5. Bonica, J. J . , and Lyter, C . S.: Measurement of blood loss during surgical operations. Am J Surg 8 1 : 496, 1951. 6. Pilcher, F . , and Sheard, C : Measurements on the loss of blood during transurethral prostate resection and other surgical procedures, determined by spectrophotometric and photelometric methods. Proc Staff Meetings Mayo Clin 12:209,1937. 7. Salzstein, H . C , and Linkner, L . M . : Blood loss during operations. J Am Med Assoc 1 4 9 : 722, 1952. 8. Gores, R. J . , Royer, R. Q . , and Mann, F. D.: Blood loss during operation for multiple extraction with alveoloplasty and other surgical procedures. J Oral Surg 13: 299, 1955. 9. Johnson, R. L . : Blood loss in oral surgery. J Dent Res 3 5 : 175, 1956. 10. Spengos, M . N.: Determination of blood loss during full-mouth extraction and alveoloplasty by plasma volume studies with I -tagged human albumin. Oral Surg 16: 276, 1963. 11. Rhymes, R., and Williams, C : Blood loss following extraction of teeth. J Am Dent Assoc 6 9 : 347, 1964. 12. Berdon, J. K.: Blood loss during gingival surgery. J Periodontol 36: 102, 1965. 13. Ariado, A . : Periodontal surgery under general anes thesia in a hospital. J Periodontol 4 1 : 507, 1970. 14. Hecht, A . , and App, G . R.: Blood volume lost during gingivectomy using two different anesthetic techniques. J Periodontol 4 5 : 9, 1974. 15. Meyer, R., and Allen, G . D . : Blood volume studies in oral surgery: I. Operative and postoperative blood losses in relation to vasoconstrictors. J Oral Surg 2 6 : 721, 1968. 16. Sinclair, J. H . : Loss of blood following the removal of teeth in normal and hemophilia patients. Oral Surg 2 3 : 415, 1967. 17. Curtis, M . B . , Gores, R. J . , and Owen, C . A . : The effect of certain hemostatic agents and the local use of diluted epinephrine on bleeding during oral surgical proce dures. Oral Surg 2 1 : 43, 1966. 18. Ambrose, J. A . , and Detamore, R. J.: Correlation of histologic and clinical findings in periodontal treatment. Effect of scaling on reduction of gingival inflammation prior to surgery. J Periodontol 3 1 : 238, 1960. 19. Rolfs, D . A . : Personal communication. 1975. 20. Shires, G . T.: Manual of Preoperative and Postoper ative Care, ed 1, pp. 42-74. Philadelphia, W. B. Saunders Co., 1971. 21. Greenwalt, T . J. et al: General Principles of Blood Transfusion, ed 2, pp. 25-28. Chicago, American Medical Association, 1973. 131
The volume of blood loss was measured on 30 patients undergoing a total of 39 periodontal flap procedures on posterior sextants at the University of Washington School of Dentistry. Measurements were recorded for the degree of inflammation in the gingival sulcus, the length of the incisions, pre- and postopera tive blood pressures, the number and units of teeth involved in the surgeries, the duration of the proce dures, the volume of anesthetic used, the surgeon's estimate of blood loss, aspirin intake, sex, areas and type of surgery. A cyanmethemoglobin determination of blood loss was made using a spectrophotometer. Patients lost an average of 134 ml of blood, with a range of 16 to 592 m l , during periodontal flap proce dures involving an average of 5 1/2 teeth in posterior sextants. Wide variations were seen between patients and in the same patient. None of the variables mea sured were strongly related to blood loss, although the duration of the procedure seemed to exert the greatest effect. It would seem a good precaution to limit surgical time to 2 hours. In view of the variability and magni tude of blood loss, it is suggested that patients undergo ing periodontal flap surgery be carefully monitored. Preoperative and postoperative blood pressures in the sitting and standing position and volumetric assessment of hemorrhage are recommended. Intravenous fluid
12
B e r d o n published the first report on hemorrhage during periodontal surgery. Using a cyanmethemoglobin comparison technique, he measured blood loss dur ing 50 gingivectomies involving a surgical field of 5 to 14 teeth. H e established that approximately 5 ml to 149 ml of blood was lost. The quantity of hemorrhage from two patients undergoing full-mouth gingivecto mies under a general anesthetic was also measured and found to be 435 ml and 624 ml respectively. Observa tion and supportive therapy was recommended for those patients with the "higher volume" of blood loss. N o specific guidelines for fluid replacement were rec ommended, however.
by DAVID A . B A A B , D.D.S., M.S.D.* WILLIAM F . AMMONS, JR., D . D . S . , M.S.D.* HERBERT SELIPSKY, B.D.S., H . D . D . ,
1
M c l v o r and Wengraf studied blood loss colorimetrically during gingivectomies and/or isolated periodontal flap procedures on 14 patients. Three patients had small, one- or two-tooth, mucoperiosteal flaps elevated and osteoplasty performed. B l o o d loss for these three patients ranged from 12 ml to 62 m l , while the other patients lost 0.7 ml to 18 ml of blood during gingivecto mies. Based upon this data, they speculated that one could expect a 10-fold increase in blood loss per tooth during a periodontal flap procedure as compared to a gingivectomy. The reasons given were that more com plex procedures involving flaps take longer and expose highly vascular bone, resulting in greater blood loss.
M.S.D.* HEMORRHAGE ASSOCIATED with surgery is a common problem which requires proper management. This in cludes accurate determination of blood loss, establish ment of effective hemostasis, and replacement of fluids when indicated. Surgery has become commonplace in the treatment of the periodontal patient. A flap approach is com monly used to allow the exposure and correction of periodontal defects. Although such surgery may be routine, little attention has been directed to the extent of hemorrhage occuring during this type of procedure. A literature search indicates that only one study has attempted, on a limited basis, to measure the amount of blood lost by patients undergoing periodontal flap surgery. It is important, therefore, to investigate the blood loss associated with periodontal flap surgery.
Full-mouth periodontal flap procedures performed under general anesthesia were estimated to result in a blood loss of 350 ml by Ariaudo in 1 9 7 0 . The meth odology was not described in that paper. Recently Hecht and A p p measured blood loss dur ing standardized gingivectomies of mandibular poste rior segments. When local gingival infiltration was used, blood loss ranged from 3 ml to 13 m l , while 8 ml to 31 ml were lost when mandibular block anesthesia was used. Clinicians have long recognized that hemorrhage varies significantly between patients, and within the same patient at various t i m e s . This variation has been attributed to systemic factors, local factors, and surgical technique. Certain systemic factors such as age, blood pressure and bleeding times, within the range of normal, have not been shown to be related to blood l o s s . Hemophiliacs, when controlled with factor V I I I cryoprecipitate, lost less blood than normal patients dur ing oral surgical procedures in one study. It is inter esting, however, that a relationship between blood loss and sex may exist, since males appear to lose blood 5 0 % faster than females during gingival surgery. Johnson, however, states that there is no such rela tionship during oral surgical procedures. A series of local factors have been enumerated which may affect the amount of surgical hemorrhage. The duration of the surgery appears to influence total blood loss, although a statistically significant relation ship has not been established. The use of epinephrine in the local anesthetic has been shown to decrease
1
13
1 4
REVIEW OF THE LITERATURE
Definitive data regarding surgical blood loss was un available until 1924. Prior to this time, surgeons had relied on physical signs such as skin color and pulse rate to indicate impending shock. Gatch and Little in 1924 first studied operative hemorrhage during general sur gery. These investigators estimated the range of values for the operative blood loss associated with 30 common surgical procedures. In the succeeding half-century, numerous investigators have established the extent of blood loss for a variety of general surgical proce dures. The blood loss associated with oral surgery was first measured by Gores, Royer and M a n n in 1955. They found that patients undergoing full-mouth odontectomies under general anesthesia lost 5 ml to 771 ml of whole blood. This value equaled or exceeded the blood loss which occurred during many major surgical opera tions. Other similar s t u d i e s reported blood loss ranging from 35 to 912 m l . Rhymes and Williams reported that patients lost 32 ml to 520 ml while un dergoing full-mouth odontectomies with local anesthe sia. 2
1 , 5 , 1 5
9 , 1 0 , 1 2 , 1 3 , 1 5
3-7
8
16
12
9
9,10
11
9,11, 1 2
* Department of Periodontics SM-44 University of Washington, School of Dentistry, Seattle, Wash 98105.
693
694
J. Periodontal. November, 1977
Baab, Amnions, Selipsky 8,17
blood loss during full-mouth extractions, although Meyer and A l l e n reported normal saline to be equally effective in reducing blood loss. In addition, postopera tive blood loss associated with the use of epinephrine was shown to be significantly greater than that found after the use of neosynephrine. Local infiltration of 2 % lidocaine with 1:100,000 epinephrine reduced bleeding significantly during gingivectomy when com pared with block anesthesia using the same anes thetic. The extent of the surgical field also appears to influence the volume of blood l o s t . The degree of inflammation in the periodontal tissues is claimed by some to affect blood loss during full-mouth odontectomy. T o date, no study has ascertained the effects of these variables on blood loss during peri odontal flap surgery. The purpose of this study was to measure the amount of surgical blood loss in patients undergoing periodon tal flap surgery. In addition, such factors as duration, amount of anesthetic, number of teeth in the surgical field, length of incision, blood pressure, and level of inflammation in the gingival sulcus, were evaluated for their effects on operative hemorrhage. 1 5
15
14
1,9
9 , 1 0 , 1 8
MATERIALS AND M E T H O D S
Thirty patients who were to undergo 39 periodontal flap procedures were selected from patients at the University of Washington School of Dentistry. The following criteria were used for patient selection: 1. There were no medical contraindications to the surgery. 2. The area of surgery included at least 4 posterior teeth, including canines. 3. Initial therapy, consisting of root planing, occlu sal adjustment, oral hygiene instructions was completed at least 3 weeks prior to the surgery. 4. N o intravenous sedation or inhalation analgesia was used during the surgery. 5. Periodontal flap surgery could include either flap curettage, bone recontouring and/or osseous coagulum grafts. In addition to the Health History Review in the patient's chart, a brief questionniare was completed by the patient prior to surgery. Such questions as, "Have you ever had prolonged bleeding following a tooth extraction?" and, "Have you taken aspirin in the last 24 hours?" were asked, to ensure that the bleeding status of the patient was recorded. Additional preoperative data including blood pres sure, location and number of teeth, length of the incision and sulcular inflammation index were re corded. A 0.5 mm diameter periodontal probe cali brated to deliver a standard pressure of 5 g, as de scribed by R o l f s , was used to gently probe the gingival sulcus at six points around each tooth involved in the surgery. The number of bleeding points divided by the total number of points probed was used as an index of
the inflammatory state of the gingival sulcus. The length of the incision was estimated by tracing the incision on the patient's models with a linear mapmeasuring device.* A 5 ml sample of whole blood was drawn from the patient's median cubital vein just prior to the start of surgery and set aside for colorimetric analysis. A l l surgical procedures were performed by eight graduate students, and one faculty member ( W . F . A . ) . Lidocaine 2 % with 1:100,000 epinephrine was used in all cases. Both block and infiltration injections into the depth of the vestibule were used. The volume of anesthetic was recorded to the nearest carpule (1.8 ml) and the time of the initial incision was recorded at the start of the procedure. In all surgeries, an inversebevel, scalloped incision was made, the coronal gingiva was thinned, and full thickness flaps were then elevated to expose the bone in the surgical site. Thorough hard and soft tissue debridement was accomplished using sharp curettes. Bone recontouring was performed in 34 surgeries using rotary instruments for osteoplasty, and hand instruments for ostectomy. The severity of the defects in a further 5 surgeries dictated the per formance of flap curettage. Continuous sling sutures were used in all cases to adapt the flaps to the crest of the marginal bone. A portable aspirator and 2 x 2 sterile gauze sponges were used to collect blood during the procedure. The patient was repeatedly cautioned to avoid swallowing during the procedures. B l o o d and saliva were suctioned as efficiently as possible using good retraction. When suturing was completed the time was again recorded. Postoperative blood pressure was recorded before the patient was dismissed. A l l instruments, hoses, suction tips, and 2 x 2 sponges were washed in a container with water, and the solution was poured into the aspirator jar. Blood loss was measured using the cyanmethemoglobin comparison technique. The concentration of he moglobin (Hb) in the aspirated blood was measured at 540 nm using a Coleman Jr. spectrophotometer.! The blood loss was calculated by comparing the concentra tion of H b in the patient's whole blood with the concentration of H b in aspirated blood times the volume of aspirated blood. The formula used is as follows: 6
U p o n completion of the surgical procedure, the surgeon was asked to estimate the blood loss in order to allow comparison with the measured value. A l l data were entered on computer cards and ana lyzed statistically using the Pearson correlation coeffi-
19
* Recreational Equipment, Inc., 1525 11th Ave., Seattle, Wash 98122. t Coleman Instrument Division of Perkin-Elmer Corp., Maywood, IL 60153.
Volume 48 Number 11
Blood Loss 695
cient and the Student's t test to evaluate and test relationships between measured variables and blood loss. A multiple stepwise regression analysis with resid uals was performed in an effort to isolate which of the measured factors contributed the most to the variation in blood loss.
variation in the volume of blood lost per surgical site, from 16 m l to 592 m l . In addition, blood loss in patients undergoing more than one area of periodontal flap surgery on different days approximately 1 month apart varied greatly. Table III summarizes this data. Patient N o . 2 showed the largest range, 50 ml to 592 ml. Those patients undergoing surgery in two different areas of the mouth during the same day showed a maximum variation in blood loss of 36 m l . There was one episode of adverse side effects attrib utable to surgical hemorrhage. A 56-year-old male, undergoing two periodontal flap procedures on the same day, lost a total of 720 ml of blood. A t the end of the procedures, his blood pressure had dropped considerably and he was experiencing orthostatic hy potension. The patient was treated postoperatively with 500 ml of intravenous balanced salt solution over a period of 1 hour and he responded well. Such factors as degree of sulcular inflammation, length of the incision, number of teeth and units of teeth did not significantly affect the volume of blood
RESULTS
Thirty-nine posterior flap procedures were done on 30 patients over a period of 6 months. Table I summa rizes the data obtained for the different variables measured during the procedures. Correlation (r) values and probability ( P ) values for each of the variables tested against blood loss are also shown in Table I. The effect of the patient's sex, location of the surgery, type of surgery, and aspirin intake can be seen in Table II. A sample size of 30 was used when reporting measured variables per patient, but a sample size of 39 was used when reporting blood loss values per surgical procedure. A s can be seen in Table I, there was a great deal of T A B L E I. Summaryof
Variable
Mean*
Surgical blood loss (ml) Duration of procedure (min) No. of teeth in surgical field No. of units in surgical field Length of incision (from models) (cm) Volume of anesthetic (carpules) Inflammation index Blood pressure Preoperative Postoperative
Measured Variables
SD*
SE*
Range*
134.4 151.8
114.3 52.2
20.9 9.5
16-592 51-255
0.44
0.002
5.5
1.6
0.30
4-13
0.02
0.46
7.3
1.8
0.33
5-16
0.07
0.33
12.4
3.1
0.57
4.5-27.5
0.25
0.06
4.4
2.0
0.36
2-10
0.48
0.001
0.15
0.40
0.65 1.77
0.00 0.33
0.13
0.20
119/72 123/77
19/14 21/13
3/2 4/2
100-180/60-100 100-180/60-105
0.26 0.31
0.04 0.02
r value P value
* N = 30. T A B L E II. Sex, Area,
Other variables Sex* Females Males Area of surgeryt Upper right Upper left Lower left Lower right Type of surgeryt Flap Curettage Osseous surgery Prior aspirin intake (24 hours)t No aspirin intaket * N = 30. † N = 39.
N
Average blood loss (S.D.)
Type of Surgery, and Aspirin Intake Range
Average blood loss per tooth (SD)
Average blood loss per minute (SD)
19 11
121.7 ( ± 1 1 6 ) 156.4 ( ± 1 1 3 )
15.6-449.4 35.4-591.6
24.2 ( ± 2 3 . 4 ) 27.4 ( ± 2 2 )
7 6 10 16
121.5 109.9 136.5 160.1
(±103) (±147) (±129) (±149)
47.5-340.9 35.4-408.2 15.6-449.4 23.4-591.6
24.6 22.1 28.9 30.7
5 34 10
171.8 ( ± 1 2 6 ) 140.4 ( ± 1 4 1 ) 160.0 ( ± 1 8 8 )
56.9-340.9 15.6-591.6 15.6-591.6
38.7 ( ± 2 7 . 0 ) 26.9 ( ± 2 8 . 2 ) 31.3 ( ± 5 7 . 9 )
1.14 ( ± . 5 9 ) 0.81 ( ± . 6 3 ) 0.93 ( ± . 8 1 )
29
131.9 ( ± 1 1 0 )
23.4-449.4
25.6 ( ± 2 2 . 2 )
0.88 ( ± . 6 4 )
(±20.9) (±29.3) (±27.4) (±29.7)
.84 ( ± . 6 7 ) .98 ( ± . 6 0 )
.73 .76 .75 1.09
(±.56) (±.75) (±.59) (±.75)
t test
No Sig. Diff.
696
J. Periodontol. November, 1977
Baab, Amnions, Selipsky T A B L E III.
Patient number
Sex
1
F
2
M
3
F
4
F
5
F
6
F
7
F
Patients undergoing multiple procedures on Days Different
Procedure No. & area
Inflam, index
Number of teeth involved
(a) L L (b) L R (a) L R (b) L L (c) U R (a) L R (b) L L (a) L L (b) L R (a) U R (b) L L (a) L R (b) L L (a) L L (b) U L
0.14 0.17 0.03 0.04 0.17 0.23 0.00 0.17 0.07 0.07 0.10 0.13 0.10 0.10 0.10
6 6 5 4 6 5 5 5 5 5 5 4 5 5 5
loss in this study. There was no one variable that could be attributed to the large standard deviation in mea sured blood loss. Seven of the eight surgeons were graduate students and one was a private practitioner. The private practi tioner took an average of 12 min/tooth and his patients lost an average of 14 ml/tooth, while the graduate students took an average of 36 min/tooth and their patients lost an average of 30 ml/tooth. The surgeon's estimated blood loss was on the aver age within 57 ml of the mean measured blood loss, but there was wide variation in the amount of error ( ± 1 to 200 ml). The range of error for the more experi enced private practitioner was ± 3 to 134 m l . DISCUSSION
The accuracy of the cyanmethemoglobin comparison method used in this study for the determination of blood loss has been demonstrated by several investiga tors to be accurate within 2 to 3 % of a known volume of b l o o d . The measurements in this study were all carried out by the same investigator using standardized, hematological laboratory techniques. Possible sources of error in measurement of blood loss using the cyanmethemoglobin comparison tech nique are blood lost to the gastrointestinal system due to swallowing, and blood lost into the tissues and not recovered. A total blood volume measurement before and after surgery using one of the indirect techniques, 1 or C r , would check on our measurements and account for blood lost into the tissues or swallowed. If measurements were taken 1 or 2 days postoperatively, this method would provide us with some information as to how much net blood loss occurs postoperatively. None of the variables measured exerted significant influence upon the volume of blood lost. The amount of anesthetic used during the procedures was the 6-8
131
5 1
Surgical blood loss
ml 37.4 119.6 591.6 270.0 50.2 71.6 108.5 116.8 245.5 59.1 80.2 23.4 15.6 103.1 48.5
Surgical Du ration
ml/Tooth
ml/min.
6.2 19.9 118.3 67.5 8.4 14.3 21.7 23.4 49.1 11.8 16.0 5.9 3.1 20.6 9.8
0.53 1.75 2.47 1.80 0.63 0.44 0.48 0.68 1.56 0.30 0.41 0.46 0.26 0.57 0.49
min 71 68 240 150 193 160 223 172 157 200 195 51 60 180 100
variable most correlated with blood loss. However, this could be attributed to the necessity for using more anesthetic to control bleeding and discomfort during the longer surgeries. Duration also appeared related to blood loss, although not in a predictable manner. A s shown in Figure 1, there appeared to be two distinct groups. One group of patients lost less than 125 ml of blood regardless of the duration, while another group bled constantly at a much faster rate throughout the surgeries, losing 200 to 400 ml during 2 to 4 hours of surgery. This phenomenon did not appear to be related to any of the variables measured in this study, although all patients who lost over 200 ml of blood were operated on for over 2 hours. Therefore, one cannot predict the volume of blood lost by timing the procedure. Other factors may exert a greater influence on blood loss than duration of the procedure. However, when surgical time was kept under 2 hours, no patient lost more than 125 ml of blood. The location and type of the surgery appeared to affect blood loss, but not in a statistically significant way. F o r example, periodontal flap surgery in the mandible resulted in an average blood loss of 151 ml per segment, while the corresponding procedure in the maxilla resulted in an average blood loss of 110 ml per segment. The greatest average blood loss per segment occurred from the mandibular right posterior area, while surgery in the maxillary left posterior area re sulted in the least average blood loss per segment. This phenomenon could be explained by the fact that all therapists were right-handed, and surgical access for the right-hander is usually more difficult in the mandibular right lingual area. Two patients appeared to bleed "excessively" in this study. Bleeding work-ups were performed for these patients and all findings were within normal
Volume 48 Number 11
Blood Loss
limits. This is consistent with other reports which state that bleeding, clotting, and prothrombin times can be within normal limits in an individual who bleeds profusely. Surgeons could estimate blood loss more accurately in this study since the aspirator jar in the portable suction was visible to the surgeon at all times. Even so, there was a wide range in error. In most private offices a central vacuum is used, and one would expect an even greater degree of error in estimating blood loss. The data indicate that, on the average, a substantial amount of blood is lost during a posterior sextant of periodontal flap surgery (134 ml). But of greater importance is the fact that a wide variability (16-592 ml) may occur between patients and in the same patient. Postoperative blood loss, while not measured in this study, has been shown to be equal to, or greater than, surgical blood loss following full-mouth extrac tions. A similar phenomenon may occur following periodontal flap surgery. A healthy adult may lose up to 1 liter of blood 9,12,14
11,15
FIGURE
697
before developing hypotension, and many people fre quently donate 500 ml to a blood bank without any apparent adverse consequences. However, consid ering the possibility of postoperative oozing and blood lost into the tissues during surgery, several investigators recommend that blood losses greater than 500 ml should be replaced immediately with intravenous fluids or whole b l o o d . Balanced salt solutions do not involve as many hazards as blood transfusion and should be used for volume replacement when the loss of volume is less than 1 liter and the hemoglobin concentration is adequate. The following procedures are recommended to those periodontists operating large areas of the mouth at one sitting or operating for long time periods. Preop erative and postoperative blood pressures with the patient sitting should be taken. A postoperative stand ing blood pressure should be recorded to assess possi ble orthostatic hypotension resulting from acute blood loss. Patients experiencing a drop in systolic blood pressure in the standing position oí 20 mm H g , or a drop in diastolic blood pressure o l 10 mm H g following 20,21
8 , 9 , 2 0
21
1
698
J. Periodontal. November, 1977
Baab, Amnions, Selipsky
surgery, should be treated with balanced salt solutions intravenously until the blood pressure returns to nor m a l . A simple volumetric measurement of blood loss during periodontal flap surgery should be performed using an aspirator with a collection reservoir. The volume can be assessed by using a known volume of irrigating fluids and subtracting this from the total volume of fluid recovered. A n estimate of blood loss could thus be made, which would aid in calculating the volume of fluid replacement necessary. Intravenous fluid replacement should be performed when the patient either (a) experiences orthostatic hypotension, or (b) loses 500 ml or more of blood. Postoperative management of all periodontal surgery patients should include instructions to drink 1 to 2 liters of fluid the day of surgery and 2 days following surgery to help prevent postoperative dehydration. The combination of possible postoperative blood loss with operative hemorrage suggests that patients un dergoing multiple quadrants of periodontal flap surgery on the same day may lose as much blood as patients undergoing a major surgical operation. W e , as perio dontists, need to be more conscious of the possible sequellae and treatment of hypotension and dehydra tion resulting from surgical blood loss. This is especially true in periodontal surgery, as most patients are being treated on an outpatient basis. 21
20
SUMMARY AND CONCLUSIONS
replacement is recommended for those patients who either (a) experience orthostatic hypotension, or (b) lose 500 ml or more of blood. REFERENCES
1. Mclvor, J. and Wengraf. A . : Blood loss in periodontal surgery. Dent Pract 16: 448, 1966. 2. Gatch, W. D . , and Little, W. D.: Amount of blood lost during some of the more common operations. J Am Med Assoc 8 3 : 1075, 1924. 3. Coller, F. A . , Crook, C . E . , and lob, V . : Blood loss during surgical operations. J Am Med Assoc 126: 1, 1944. 4. Lenahan, N . E . , Spitz, I. A . , and Metealf, D . W.: Blood determinations and estimation of blood loss during surgical operations. Arch Surg 5 7 : 435, 1948. 5. Bonica, J. J . , and Lyter, C . S.: Measurement of blood loss during surgical operations. Am J Surg 8 1 : 496, 1951. 6. Pilcher, F . , and Sheard, C : Measurements on the loss of blood during transurethral prostate resection and other surgical procedures, determined by spectrophotometric and photelometric methods. Proc Staff Meetings Mayo Clin 12:209,1937. 7. Salzstein, H . C , and Linkner, L . M . : Blood loss during operations. J Am Med Assoc 1 4 9 : 722, 1952. 8. Gores, R. J . , Royer, R. Q . , and Mann, F. D.: Blood loss during operation for multiple extraction with alveoloplasty and other surgical procedures. J Oral Surg 13: 299, 1955. 9. Johnson, R. L . : Blood loss in oral surgery. J Dent Res 3 5 : 175, 1956. 10. Spengos, M . N.: Determination of blood loss during full-mouth extraction and alveoloplasty by plasma volume studies with I -tagged human albumin. Oral Surg 16: 276, 1963. 11. Rhymes, R., and Williams, C : Blood loss following extraction of teeth. J Am Dent Assoc 6 9 : 347, 1964. 12. Berdon, J. K.: Blood loss during gingival surgery. J Periodontol 36: 102, 1965. 13. Ariado, A . : Periodontal surgery under general anes thesia in a hospital. J Periodontol 4 1 : 507, 1970. 14. Hecht, A . , and App, G . R.: Blood volume lost during gingivectomy using two different anesthetic techniques. J Periodontol 4 5 : 9, 1974. 15. Meyer, R., and Allen, G . D . : Blood volume studies in oral surgery: I. Operative and postoperative blood losses in relation to vasoconstrictors. J Oral Surg 2 6 : 721, 1968. 16. Sinclair, J. H . : Loss of blood following the removal of teeth in normal and hemophilia patients. Oral Surg 2 3 : 415, 1967. 17. Curtis, M . B . , Gores, R. J . , and Owen, C . A . : The effect of certain hemostatic agents and the local use of diluted epinephrine on bleeding during oral surgical proce dures. Oral Surg 2 1 : 43, 1966. 18. Ambrose, J. A . , and Detamore, R. J.: Correlation of histologic and clinical findings in periodontal treatment. Effect of scaling on reduction of gingival inflammation prior to surgery. J Periodontol 3 1 : 238, 1960. 19. Rolfs, D . A . : Personal communication. 1975. 20. Shires, G . T.: Manual of Preoperative and Postoper ative Care, ed 1, pp. 42-74. Philadelphia, W. B. Saunders Co., 1971. 21. Greenwalt, T . J. et al: General Principles of Blood Transfusion, ed 2, pp. 25-28. Chicago, American Medical Association, 1973. 131
The volume of blood loss was measured on 30 patients undergoing a total of 39 periodontal flap procedures on posterior sextants at the University of Washington School of Dentistry. Measurements were recorded for the degree of inflammation in the gingival sulcus, the length of the incisions, pre- and postopera tive blood pressures, the number and units of teeth involved in the surgeries, the duration of the proce dures, the volume of anesthetic used, the surgeon's estimate of blood loss, aspirin intake, sex, areas and type of surgery. A cyanmethemoglobin determination of blood loss was made using a spectrophotometer. Patients lost an average of 134 ml of blood, with a range of 16 to 592 m l , during periodontal flap proce dures involving an average of 5 1/2 teeth in posterior sextants. Wide variations were seen between patients and in the same patient. None of the variables mea sured were strongly related to blood loss, although the duration of the procedure seemed to exert the greatest effect. It would seem a good precaution to limit surgical time to 2 hours. In view of the variability and magni tude of blood loss, it is suggested that patients undergo ing periodontal flap surgery be carefully monitored. Preoperative and postoperative blood pressures in the sitting and standing position and volumetric assessment of hemorrhage are recommended. Intravenous fluid
