Effects of hypotensive anesthesia, nonsteroidal antiinflammatory drugs, and polymethylmethacrylate on bleeding in total hip arthroplasty patients

Effects of Hypotensive Anesthesia, Nonsteroidal Ant|inflammatory Drugs, and Polymethylmethacrylate on Bleeding in Total Hip Arthroplasty Patients

Howard

S. A n , M I ) , * W a s s c f E. M i k h a i l , M D , * W i l l i a m T. J a c k s o n , M I ) , * B r a d T o l i n , M I ) , w a n d G c o r g e A. D o d d , B A ~

Abstract: Ont." hundred k)rl~' patients ranging in age from 26 to 88 years, who had primary total hip arthroplasty (l)erformcd by the same surgc(m and lateral surgical apl~roach), were analyzed for intraopcrative and postoperative bh)od loss. "lhe factors affecting blood loss. ,,vhich include bleeding disorders, medications, duration of surgery, the mean intraoperativc blood pressure, and use of cement, were all recorded. A significant reduction in the intraopcrative blood loss ,,','as ol.,se~'cd in the groul, of patients with hypotcnsive anesthesia (>20 mmllg drop in the mean intraoperativc blood pressure using inhalation anesthetics) compared to tile group of patients who did not have hyl,otensivc anesthesia. The patients who had been on aspirin or nonsteroidal ant|inflammatory drugs prior to surgery had increased intraoperativc and postoperative I,Iood loss compared to the patients who did not take sudl medications. The effect of cementing with methylmcthacr3'late on bleeding was also observed; the patients with uncemented implants had a greater blood loss after operation than tile patients who had cemented prosthetic components. Key words: total hip arthroplasty, surgical bleeding, hypotensive anesthesia, nonsteroidal antiinflaminalo~, drugs, methylmethacryl,'~te cement

Any technique to dccrcasc blood loss during a major surgical procedure is obviously beneficial to tile patient in reducing tile risks of transfusion-related complications. Total. hip arthroplasty ('I'IIA)

has been (,no of the most frequently pcrfornwd orthopaedic procedures, and it carries tile risk of major blood loss. For many years, controlled hypotcnsive anesthesia has bccn utilized in a variety of major surgical procedures in order to reduce intraoperativc blood loss and has recently been applied to THA ( 15, 9, i I, 16-18, 21, 23). Another factor for bleeding may bc aspirin or nonstcroidal antiinflammatoq,, drugs (NSAIDs), which many patients take for their arthritic pain before surgery. Some authors have reported increased per|operative blood loss (14, 22), whereas others have found no significant diffcrcnce in bleeding (1, 6) with per|operative use of aspirin.

From the "lh'pamvtnt of Orthepa,'dir Surgery. The Mc,lical Celltgt ef Wismn$in. 8700 West Wisconsin Avtmte. Mihvauktr Wiscensin. tDepartmcnt ef Orthcs St. Vincent ,'~Itdical Center. Toledo. Ohio. #Derartmenl of Orthol'aedk"s. The Medical Colh'ge cf Ohio. Teledo. Ohio. ~llnivcr$ity of Pomsylvania. t'hiladellqfia. Pomsylvania. and '*,~ltdical Celh'4e of Ohio. ToledJ, Ohio. This paper was ptc~,cntcd at the 55th Annual American A(.atlcmy of Orthol,mcdic Surgeons, Atlanta. Georgia. Fcbruat,/. 1988. Reprint request,,: Dr. l,lowdrd S. An. As,,istant Professor. Dcparlmcttt of Or(hopacdics, "The Medical College of Wisconsin. 8700 West Wi~,con~.in Avenue, Mil'e,',lukcc, WI 53226.

245

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The Journal of Arthrop!asty Vol. 6 No. 3 September 1991

Another diffcrcntiating factor for postoperative blood loss nlay bc the use of cement in THA. Rcllortcd hcrc is a sttidy of llaticnts who underwent primary TIIA. "rhc cifcct of deliberate hy'potcllsivc anesthesia during surgery oil intraopcrativc bleeding as well as the effects of aspirin or NSAIDs and polynlcthyhnetlaacrylatc on licriopcrativc blood loss are investigated.

Materials and Methods One hundrcd hirty s patients who uildelavcni prinlary TltA at the St. Vincent Mcdical Center and Toledo llospital ill Toledo, Ohio (leaching hospitals afliliatcd with Ihe Medical College of Ohio at Tolcdo) during ihc period 1983-1986 wcrc reviewed retrOSl~CClivcly. The ages of patients ranged from 26 to 88, averaging 64.4 ycars. Any paticrlls who llad bleeding disordcrs with abnornial proihroinbin Iinie (lrr), p,'lrlial ihroinboplaslin Iilne (!'I'I'), and those who h,ld lakcn anticoagulants (warfarin sodiunl or dc• for Iherallculic or proph),lactic purposcs were r215 from ihc study. We did nol use aniicoagtllanis oil a rOlllinc basis from 1983 to 1986, although wc havc started using routine anticoagulants siilcc 1986. All palienis in 01is study wore pneumatic r cutfs for prophylaxis. The patici~.ts who had bccn on aspirin or NSAIDs were included in this study to assess their effects on bleeding. NSAIDs inchldcd ibuprofen, salsalate, indonicthacin, fenoprofen, Naproxcn. piroxicaln, sulindac, Iohrlctiil. and diflunisal in this series. All of the surgery was performcd or supcrviscd l,y the sanle surgeon (W.E.M.). and the straight lateral or llardingc approach was used in all cases. "l'he agents used for anesthesia wcrc halothanc (Fluethane), enfluranc {Ethranc), or flurane (Isofluranc) after induction with pcnlotlial. "rhc intraopcrativc blood loss was deicrnlincd by the volume of blood in suction apparatus and the weight of the sponges with I,lood. The I,Ostopcrativc blood hiss was determined by the a m o u n t of suction dr,'linagc for 48 hours after operation. The hclnoglobin drop dire to surgery was calculated by subtracting the hemoglobin valric just prior to discharge from the preoperative hemoglobin value aml adding 1 g/ dL for each unit of blood irailsfusion given. The duratiola (if Ol,eration and use of l~olynlethylmelhac rylatc wcrc also recorded. "l'hc preoperative blood pressure was obtained by averaging all the available preoperative blood pressures taken in the hospital the day before stirgcr)'. "The average intraopcrativc blood pressure was dctcrlnincd by averaging each blood prc.,,surc at 30-

niimlic intewals from Ihe lime of incision to the end of ihc proccdurc. The lileali artcrial pressure for cach blood pressure incasuremcnt was calculated fronl the formula: l)iastolic pressure + (systolic pressure - diastolic prcssurc)/3. Thc drop iu blood pressure was then calculated by subtracting the average intraopcrative blood I,rcssure from the a',,cragc preoperative I,lood pressure. If the blood pressure drop was greater than 2() mnlllg (group 1, 90 patients), it was considered to bc a hypotcnsivc anesthetic technique. The patients wilh a drop ill blood pressure of less than 20 nunllg duling surgery served as colitrol (group 2, 50 patients). Two groups were compared with respect t(, intraopcrative blood loss, postopcrati','c blood loss. and henloglobin droll, hi order to elitninatc coiifolinding variabics, furiller caiculalion ',,,'as done tin onl 7 those patients who did not iakc aspirili or NSAIDs, and separate analysis was done for those w h o had cemented prosthesis and uncclncntcd prosthesis (groups A. B, and C). "lhe clfcct of aspirin or NSA1Ds was also analyzed by conlparing a grotip of patients w h o had not bccn on aspirin or NSAIDs or discontinued the medications at least 2 weeks prior to surger), (group 1, 85 patients) Io a group of patients who had been on the medications or did not slop the incdications prior to surge%' (group 2. 55 i,atients). Again. further analysis was done, separating those patients w h o h a d ilnCCllientcd prosthcsi,, from Ccillcnlcd prosthesis, and those patients wh(i had hypotcnsivc anesthcsia from those who did il~)t (groups I A and IB). Finally. thc effect of usc of polymethyhncthacrylate on bleeding was analyzed. A comparison was nladc of blood loss anlong patients who had both conlli(mcnts (group !, 10 patients) and iicither componenl cclncnted (groilp 2, 9,1 patients) thiring siirgery. Again, further analysis was done on those paiicnls who had not taken aspirin or NSAIDs prior to 5urgc~, alld had h),poir anesihcsia (groulis I A aiid 2A). The dittcrcnccs bciween ihc groulis were evahiatcd !,)' iiieans Of tilt" unpaired Sltldelil's/-test.

Results Effect of Hypotensive Anesthesia The mean inlraoperalivc blood loss in lhc hypotcnsivc group was significantly Icss than Ihe norIllOICIISiVC group amollg ihose l)atienls w h o had not taken aspirin or NSA[Ds and who had both pros-

Factors Affecting Blood Loss in THA

6glcc

I

GtOul)I. ttlfl~olen$1ve

I

Group,I. No~'molensvve

*

An ot al.

247

I

GtOuDIA"

I

Group,IA Notmolcntlv(t

HyDotensnve

$88cc

413 3.53 mg.,dl 317

A

Operative Bk)od Loss

Poslogerative Blood Loss

66kc

Hemoglobin Drop

I

Gtoul)lB.

I

~tO~D

118

B

O1)erltive Blood Loss (p : O.028)

Poslol)eral,ve BlOod Loss

lqYDOtc~nsIve fdorrno,en%Jvr

Hemoc~ob~n I~'oD

I

GrOuDIC; Hyl)o,ln$1ve

I

GIouptiC: Normo,r

6 2 ~ r 1 6 2__

i?9cc

30 mg'OI

C

Opetltnre Blood Loss

PosloDetrlhve Blood Loss

285 mg,ot

Hemogk:X~n I~op

D

Oll)eraltve

PolltODeral,ve

Hemog~4)m

Blood Loss (p = 0.027)

Blood Loss

Drop

Fig. 1. Effect o f I w p o l c n s i v c a n e s t h e s i a o n b l e e d i n g in i l i A : i n t r a o p e r a t i v c a n d i ) o s t o p c r a l i v e I.)lood loss a t e s h o w n as well as h e m o g l o b i n d r o p . (A) All palienls. (B) Patients w i t h c e m e n t e d p r o s t h e s i s a n d n o NSAIL)S. (C) l'ali(:nls w i t h u n c e m e n l c d prosd~esis and n o NSAIDs. (D) l'alienls w i t h n o NSAIDs.

lower l)lood loss in the hypotcnsivc group lhan normotcnsivc group (428 cm s in group IC vs 561 c'm ~ in group 2(:. P = .027). When lhc' analysis was done will)out consideration of medic'ations and prosthesis, no observable difference was found in operative l)lood loss between lhc hypolcnsive and normotcnsix,(: groups (492 cn) ~ in group I vs 4 8 ] cm s in group 2). A summary of findings betwc(.'n the hypoten.sive and normotensivc groups is s h o w n in Table i and Figure I.

thclic components cemented (447 (.ms in group I A vs 635 cm s in group 2A. I' = .028). Among those who had uncemented l)roslhcsis and no medication. the intraopcralive blood loss in the hypotensive group was also less than the normolcnsivc grot,p. but it was not statistically significant (422 cn) ~ in group IB vs 511 cm ~ in group 2B. P = .2). The combined analysis of intraoperative blood loss among patients wi[h either uncemcntcd or ccm(:ntcd prosthesis but no mcdicadon revealed a significantly

Table 1. El'feel of llypolensivc Anesthesia on Bleeding in Total llip Arlhroplasly Group

I

2

IA

2A

IB

2B

IC

2C

90 32.6 12-1 .192 656 3.5 ] 5(,6

50 I 3.7 118 .181 691 3.17 658

I0 35.6 138 -blT" 462 3.18 700

10 7.3 15(9 6~,5" 588 .l. 1 ~, 1050

~4 32.1 I I0 -122 666 3.0 ,I 38

I5 10.3 ! 14 S 11 579 2.85 .I 16

-I4 32.9 116 .128 t (,20 3.06 497

25 9.1 128 561 t 582 3.36 670

,1

No. patients Mean blood pressure drop (mmilg) Meat) opcrati,.(: time" (minutes) Operative blood loss (cm ~) |'ostopcraliVe blood loss (cm ~) Hemoglobin drop (WdL) Blood Ira,]sfusion ((.m ~)

group 1. h~,'pOtr anesthesia (greater than 20 HunlJg drop ill blood pres,,t,rc dr,ring surgcl'T); l.:it)t.lp 2. n(,rmotcnsivr anesthesia (Ir than 20 m m l t g drop in blood pressure during st, rgcrT): .~rt)up A. no .)Hfirin or NSAII.),, and r l)rosthcsis; group B. no .1~.piril) oi" NS.,~.I[)~ +111dunccl94 p|osthcsis; group C.. no aspid,) <,r NSAI[>s (combhwd analysi,, of A and B groups) 9 St,'Itisticallysignificant. P =- .028"; * St,)tisticallysignifi,~.int./' = .027

248

The Journal of Arthroplasty Vol. 6 No. 3 September 1991 Table

Effect of Aspirin or N S A I D s

Tile postoperative blood loss of tile patients of group 1, w h o either discontinued tile ntcdications at least 2 weeks prior to surge~' o r did not take such medications at all, was significantly less than those of group 2, '.vho had bccn on aspirin or NSAII)s just prior to surgery (600 cm ~ vs 772 ctn ~, P = .005). Tile me,art operative blood loss was only slightly less in group 1 than group 2 (481 cm '~ vs 499 cm~). Although tile difference of m e a n blood llrcssure drop between groups 1 and 2 was small, separate analysis was done a m o n g those patients w h o had hypotcnsivc anesthesia and u n c e m e n t e d prosthesis. This analysis revealed that both the operative and postoperative blood losses were less in the group without the history medications (group I A) than in the other group (group 1B), attd the hemoglobin drop ',,.'as significantly different between groups 1A and 1B (3.03 gMl, vs 3.9 g/dL, P = .015). Analysis a m o n g the I)atients w h o had normotensive anesthesia and cemented prosthesis was not done because o f the small n u m b e r of patients in this category. A stmunary of findings o n effect of aspirin anti NSAIDs on bleeding is s h o w n in Table 2 anti Figure 2.

Effect of C e m e n t

Tile postoperative blood loss in tile patients w h o had both c o m p o n e n t s cemented was significantly less c o m p a r e d to tile group w h o had no cement (522 cm 3 in group 1 vs 730 cm ~ in group 2). A significant difference in tile m e a n postoperative blood loss was also observed a m o n g tile patients w h o had hypotens|re anesthesia and no medication (,162 cm s in groul) IA, 666 cm ~ in group 2A, P = .081). Analysis a m o n g the patients w h o had normotcnsive anesthesia and cemented prosthesis was not done, because of the small n u m b e r of patients in this care-

I

GrOuD I. NO Mc~CLcahon$

]

Group |1. Meckcahon$

2. Effcct o f A s p i r i n o r N S A I D s o n Total llip Arthroplasty Group

2

I

No. patients M e a n bh)od pressure drop (mmHg) M e a n operative time (minute.,) Operative blood loss (r ~) t'ostopcr,ltivc bh)od loss (cm ~) tlcmoglobin drop (g'd[.) Blood tr,'msfu,.i(m (cm ~)

85 25.3,

55 26.8

127 481 600" L36 6.1.1

l 1,1 499 772" 3.46 532

A

Postopetlaive Blood Loss

(P = 0.005)

IA

2A

34 32.1

19 ~,3.9

I tO ,123

666 3.03 t

438

112 531 81 l 3.90 t .147

g r o u p I. no aspirin or NSAIDs; I.:rotlp 2, aspirin or NSAIDs prior to surgery; group A. hypotensivc anc~,the~,ia dnd u n c e m e n t c d pro,,thc~,is 9 statistically significant. P = .005; v stati,,ticMIy significant. P .015

T a b l e 3. Effcct of Cement on Bite(ling in Total flip

Arlhroplasty Group

I

No. patients Mean blood I)rcs~.utc drop (mmilg) M e a n opcrativc time (minutcs) Operative blood Io~,s (cm ~) Postoperative blood los':, (crn ~) }lemoglobin (ho|) (g'dL) Blood tran,,fu',ion (tin ~)

2

3,0 22.9

9-1 26. I

141" 5~,4 522 'r 3.66 766

i tO' 457 730 t 3.18 .177

IA

2A

l0 35.6

~,.t 3,2. l

138 4.18 462t 3.18 700

110 423 666* 3.0~ 43,8

group I. ccmcntcd t)t'osthcsis; groui~ 2. UtlCCtllClltCd |~rosthe~,is; group A. hy|~)tensi','c anc~thcsi.a a n d no aspirin or NSAIDs 9 statistically ~,ignificant, (P = .00l for groups I and 2. P = .008 h)r group,, IA aml IB); t stati,,tically significant (P = .006); * ahnost stati,,lically r,ignificant (P -: .08 I)

gory. A s u m m a r y of findirtgs on effect of cement on bleeding is s h o w n in Tablc 3 and Figure 3.

Discussion

This rctrospecti'.'e study confirms tile previolts reports on hypotensive ancsthesia's reduction of operative blood loss ( 1 - 5 , 9, I I, 16-18, 21, 23) and 811CC I I

3.36 3 46 m~,,r mqlem

OI)eqllnm Blood Lost

Bleeding in

Group IA, NO Med~C.Hnon$ GeouOIIA' MechCahOnS

"ln'l

Hemoglobin Dto~

OI)enltive Blood Loss

[3

Poitooefiawe Blood Loss

3.90 mSl r

Hemogloben (~op

(p = o.ots)

Fig. 2. Effect of aspirin or NSA1Ds on bleeding in TIIA; intraopcrativc, i)ostoperative blood loss and hemoglobin drop arc shown. (A) All patients. (B) Patients with hypotcnsivc anesthesia anti unccmcntcd prosthesis.

Factors Affecting Blood Loss in T H A I 61~cr I

Gfouo IA" Ccmen!

9

I

Gio,;o IIA: NO Cement

730cc I

A

Postoperat,ve Blood Loss (1= = O.08t)

G~o.~DII NO Cement

m r

Hemocjk:)bln D~op

Ol~er~ive Blood Loss

B

Postoper~,ve Blood Loss (p : 0.006)

249

GiOuO I. Cement

3.66

318 3 03 m ~ mq,~

C~er,~ive Blood Loss

An el al.

318

Hemocjlobin Drol~

Fig. 3. l!lfcct of the ccmcnt on blccding in total hip aithroplast)'; intraol)crativc and im~,topcrativc blood I(i,,s and hcmoglobin drop arc shown. (At Patients with hypotcu<,ive aricsthcsia and no NSAII)~. (If,) All pat|tills.

finds aspirin or NSAIDs to be associated '.vith incrcascd per|operative bleeding. Also. there ,,,,','is more blood loss in noncemcnted "I'HA than in cemented TIlA. We found a statistically sigtfificant difference in intraoperativc blood loss t,etween tmrnmtensive and hypotensive groups atttong cemented total hip patients but not among u n c e m e n t e d total hip patients. We cannot explain this. except that the ntinibet of patients is too small to be statistically sigtiil|cant. The various agents that have been used to iriduce |iylmtension in TttA arid otlaer orthopaedic procedures irlclude halothanc (2, 3, 16), cnflura,tc (15), pcntolinium (1 I, 13), Irintethaphan (12. 13}, arid nitroprussidc (3, 4, 9, 19, 21, 23), riitroglycerin (8). cpidural block (17), and spinal attcsthcsia (18). A majority of patients i,t thi,~ series was anesthesized with halotharie, arid a fe,,v patients with enthtranc and Isoflurane. The choice of anesthetic agents or techniques is often based primarily on the personal preference of the attcsthc,;iologist, and the importance rests on careful and close monitoring of blood pressure to avoid contplications (8, I0). The possible complications tnay inchtdc arrythmia, cerebrovascular accident, rnyocardial infarction, arid renal ,,r hcpatic damage (10). These COml~licati6ns can be nliniinizcd by the trtaintenance of systolic blood pressure above 70 ml. of nlerctiry to perftise vital oigans (20). Also, it is inllmrlanl to select otll any pat|cuts with histoW of carotid stem)sis, c o r o n a r y atrely disease, or renal impairnient (8). The only COlilplications of this series wcrc ill a 79-ycar-old Illall who developed a o-irdiopulnmriat T arrest and died, ptobabh.,' seconda~' to a massive puhnonar 3, entbolism, and in a 62-year-ohl than who dcvclopcd nonfatal puhuonary embolisnt. Whether hypotensive anesthesia had any r o d iil these coniplications i~ difficult to delerntine.

It is widely known thai aspirin or NSAII)s inlet fere with the plalelcts* aggregating properly via inhibition of proslaglandin synthesis (7). This study points out that a significant difk'rcnce in blood loss may be due to these medications (20). Fcrraris and Swanson reported 52 patients undergoing general surgical procedures and foulld no increased perioperali`.,e blood loss (6). Ilovr Torosian el al. found a higher mediastinal blood loss in pal|cuts taking aspirin after coronary artery bypass graft surgery (22). I'ostoperati,.'e hematoma is also attributed to aspirin irlgestion (14). Amrcin et al. reported 129 patients undergoing TtIA and found aspirirl to cause a slight increase in bleeding that l,ccomcs discernible statistically, in general, only when large numbers of patients arc compalcd (I). The additional blood loss was about 400 Cnl ~ overall, vehich is similar to our study. "rhis study did not mention operati`.'e duration or use of cement (1). We disagree with their conclusion that the additional blood loss is not of great intlmrtance. In fact, they fotmd tit,it in a subgroup of pat|colts who had hypotensive anesthesia, the blood loss was significantly greater in the aspirin group than control subjects ( 1,777 cm ~vs 1,281 tin ~, I' < .01). Therefore, ',,,'c reoumnlelul to the patients umlergoing TIIA to discotitintle aspirin or NSAII)s prior to surgery. A larger stttdy is needed to compare the diifercnccs in bleeding ,-imemg the various NSAIDs. Finally. the trend of nmrc bleeding irl noncenlented THA than in cemented Ti IA is probably duc to the effect of cctnent phigging bleeding sites from the bone, whereas more bleeding is expected fronl the exposed bone when tit) ccnlent is used. In sutn|n,-iry, in order to nlinimize transfusion-related risks, such ,'is transfiision react|or|, hepatitis, and acqttircd imnnlnodelicicllcy syndronle (All)S).

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The Journal of Arthroplasty Vol, 6 No. 3 September 1991

the o r t h o p a e d i c s u r g e o n s h o u l d i n f o r m the p a t i e n t u n d e r g o i n g T I I A to d i s c o n t i n u e a s p i r i n a n d NSAIDs prior to s u r g e r y a n d p l a n for h y p o t e n s i v e a n e s t h e s i a w h e n a p p r o p r i a t e . O n e shot,hi also cxpc,.'t m o r e p o s t o p e r a t i v e blood loss if ilnft'nlClllt'(I prostllcsis is used i n s l c a d o f c e m e n t e d p r o s l h c s i s .

References I. Amrcin I'C. Ellman L, Ilarris Wll: Aspirin-indt,ccd prolongation of bleeding time and pcri(~pcr,ativc blood loss. JAMA 2,15:1825. 1981 2. Amaranath L. Casco~bi IIF. Singh-Amaranath AV, Frankmann I)B: Relation of ancsfllcsia to total hip replacement and control of opcraliVt? i)lood loss. Auc~th Analg 5./,:641, 1975 3. Barbicr-llohm G. l)csmonts JM. Coudcrc li ct ah Comparative effect`; of indttccd hypotcnsion anti normovolacmic hacmodihtlion on blood los,; in total hip arthroplasty. Br J Anac:,lh 52:!039, 1980 4. Cunningham AJA: Controlled hyp()tcnsiou to minimite blood loss of anaemic jehovah's witness patient undergoing total hip and shoulder replacement. Fir J Anacslh 5 4 : 8 9 5 , 1982 5. Davis N.J. Jcmdngs .JJ. llarris WIt: Induced hylmtcnsion anaesthesia f'nr total hip rclflaccmcnt. Clitl O f thop 101:93. 1974 6. Fcrraris VA, Sv,'an~on E: Aspirin usage and pcrinpcrativc blood loss in patients tmdcrgoing unexpected opcralions. Surg Gynccol Obstct 156:439, 1983 7. Kclton FG. llirsh F: Amiplatclct agents: rationale and rcsuhs, p. 737. In Bloom. AL ct al. reds): Ilcmo~lasis arid thronlbosis. Churchill l.ivingstonc. New York. 1981

8. Knapl) I'W, Stehling I.C: Anesthesia update # 12: hypolcnsivc ancslhcsia. Orthop Roy 11 : 121, 1982 9. Lawson N%V.q hompson DS. Nelson CLct ah Sodium nitropmsside induced hylmtcnsion for supine total hip replacement. Anesth Analg 5 5 : 6 5 4 . 1976

!0. Lindop M.J: Cmnplicalion`; and mod)idity of controlled hypolcnsion. Br J Anacslh ,t7:799, 1975 11. Mallory TII: Ilypotcllsivt" anesthesia in Iolal hip replacement. JAMA 22,1:2,18. 1973, 12. Mandcl RJ. Brown MI), ,McCollough NC ct ah Ilypoicnsivc ancslhcsia and auloiransfusion ill sphlal sur~4cry. Clin Ortlmp 15,/,;2?. 1981 13. ,McNcill TW. DcWald RL. Kun K N c t ah Controlled hypotensivr anesthesia in scoliosis surgcry..I llonc .loinl Surg 56A:1167, 1974 I,I. Mcrriman li. Bell W. l.ong I)M: Surgical po`;topcralivc bleeding associated wilh aspirin ingestion. J Nct,rosurg 50:682. 197(2 15. Patti NJ. Patti IIS. Paskin S. Laufcr S: h"ltluccd nil)dcrate Iwi)otcusivc ancslhcsia for sl~inal ftt`;ion and Ilarrington-rod ill~,Irtllnclllalioll..I l}tmc Joinl Surg 67:138,1. 1985

16. Oriel TF. Kovslcd P. Sorcn`;cn B'. ,Moderate hytmtcn~i~,'c ,'lll,lt'::,lht'~i,l for rcdtx(tion of blood loss d!lring total hip replacement. Acta Anac~lhc~iol 5c,lnd 2 6 : } 5 1 . 19,82

17. Rosbcrg B. Frcdin II, Gustafson C: Anesthetic techniques, and surgical Icdmiqucs and surgic,ll hi(rod loss in total hip arlhroplasty. Aria Anacsthcsiol Stand 2 6 : 1 8 9 , 1982

18. Set,lee, Ti', Ranav,'al C: "lhc use o1 Sl'final anaesthesia for Iolal hip rcplaccmcnl arlhroplasty. J Bone .Ioinl Sutg 57A:17~,. 1975 19. Shapira Y, Nyska M. Eimcrl I.) c! ah llyl~otcnsivc anesthesia during Imslcrior fusion ()f spinal dcl'ormitics. Otthop Rcv 1,1:21 I. 1985 20. Strt, nix~ L: Organ pcrfu~ioxl dtnring controlled hypotcn,,iml. Br J Anacsth 4 7 : 7 9 3 , 1975 21. Thompson GI'. Miller RI). Slovens WC, Murray WR: Ilypolcnsivc anaesthesia for total hip arthmph'lsty. Anesthesiology 48:91. 1978 22. "l'orosian M. Michcl`;on El., Morganroth J. ,MacVaut:h I1: Aspirin ,and coumadm relalcd bleeding after coronary arlcry bypass gr,fft surgery. Ann Intern Mcd 8 9 : 3 2 5 , 1978

27,. Vazccry AK. l.undc O: C(mlrollcd hypotcn~ion in hip joint surgery. Acta Orthop Stand 50:433. 1979