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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_725_Библиотеки_им_академика_М_И_Перельмана
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resuscitation,asreflectedintheurineoutput.
Youraimisatleast0.5to1mlurine/kg(patient’sweight)perhour.Sofromthe‘average’70kg
or155lbpatient(oh,howrareinourmodernpractice…),youwouldwantbetween30-50ccof
urineperhour.Adequateurineoutputisthesinglebestsignofadequatetissueperfusion
associatedwithsuccessfulfluidresuscitation.
Invasivemonitoring
The central venous catheter and the Swan-Ganz pulmonary arterial
catheteraretoolswhichpermit‘specialstudies’tobecarriedoutrapidly
andrepeatedly.The downsideofsuchdevicesis thattheyareinvasive,
expensive, often inaccurate, and associated with potentially lifethreatening complications. Invasive hemodynamic monitoring could
provideendpoint measurements that,inconjunction with urinary output,
indicatetheadequacyoffluidresuscitation.
Thecentralvenouscatheter
The central venous catheter measures central venous pressure
(CVP)which is a productofvenous return (i.e.bloodvolume) and right
ventricularfunction.LowCVPalwaysmeanshypovolemia,butahigh
CVPcansignify either over-expansion of bloodvolume orcardiac
failure.SoaimforanadequateurinaryoutputwithaCVPinthenormal
range,upto12cmH2O.WhentheCVPrisesabovethenormalrangeand
the urinary output is still not adequate then either cardiac or renal
functionis impairedor themeasurement isan error.Falseelevationsin
CVP are caused by abnormally high intra-thoracic or intra-abdominal
pressure, which is directly transmitted to the great thoracic veins. The
messageisclear—aslongastheurineoutputisnotadequateand
theCVPislow—pourinthefluids.Butremember:yourpatient may
be far behind on fluid in the presence of a high or normal CVP. And
anotherhint:theabsoluteCVPreadingmeanslessthanitstrend;it
iswhen a low ornormalCVPsuddenlyjumpsupthatyou have to
slowthefluids.
Oryou can give abolus of fluid (300mlfor example) rapidly andmeasure CVP.If it doesnot
increase,thepatientappearstobehypovolemic.Ari
The important message here is that it is the response of the CVP
measurement to a fluid challenge that best indicates the patient’s fluid
status.
TheSwan-Ganzpulmonaryarteryflotationcatheter
TheSwan-Ganzmeasurespulmonarycapillarywedgepressure,which
reflects the volume status and left cardiac function. Like the CVP
catheter,the‘Swan’isusedinconjunctionwithurinaryoutput.Weaimfor
a normal ‘wedge’ pressure (around 14mmHg) in conjunction with an
adequate urinary output. As with the CVP — a low wedge pressure
alwaysmeanshypovolemia; a high wedge pressure on the other hand,
mayindicateeithervolumeoverload,ordysfunctionoftheleftheart.With
the Swan-Ganz insitu, you can calculate and derive information about
cardiacfunction(cardiacoutputandcardiacindex),adrenergicresponse
to injury or illness (peripheral vascular resistance) or tissue perfusion
(oxygenconsumption andoxygen delivery).Anormalcardiac indexisa
good confirmatory endpoint for resuscitation and, if pre-existing renal
failure is present, is a good independent endpoint. When the wedge
pressureisnormal orhighandtheurinary outputandcardiacindexare
stilllowthenpharmacologicalintervention with inotropic agents may be
indicated.
Weknowthatintensivistsandjuniordoctorsliketoinsertcentrallines
and especially Swan-Ganz catheters. Being invasive and able to
measure sophisticated data is fun and clinically attractive.But invasive
monitoringmaybeapanaceaoraPandora’sbox.Wedgepressuresare
notoriously inaccurate in emergency surgical patients — proneto false
highreadingssimilartotheCVP.Swan-Ganzcathetersareexpensive,
predisposed to complications and — above all — they rarely add
anything to the management of your patients. Consider this: when
was the last time that your anesthetist really effectively used, intraoperatively, the Swan-Ganz you placed pre-operatively? We cannot
remembersuchacase.
Anon-invasiveequivalentoftheSwan-Ganzcatheteriscurrentlyavailabletomeasurecardiac
output—PICCO(peripherallyinsertedcontinuouscardiacoutputmonitoring).Danny
Laboratory
Theinformationprovidedbylaboratorystudiesiseasytointerpret.Aim
for resolution of hemoconcentration, normalization of electrolyte, BUN
andcreatininelevels,andresolutionofmetabolicacidosis.Asmentioned
previously, look at the baseexcess (BE) —if persistentlynegative, the
oxygendeficitatthetissuelevelhasnotresolved.
Bloodandbloodproducts
Blood products, such as whole blood, packed red blood cells, fresh
frozen plasma, cryoprecipitate or platelet concentrate, are indicated
selectively to restore oxygen-carrying capacity in actively bleeding or
chronically anemic patients, and to correct clotting abnormalities if
present.Do notforget,however, the bloodbankbloodisadouble-
edged sword. Beyond the usual and well-known complications of
transfusion, blood is immunosuppressive and may be associated
with an increased probability of postoperative infections. In
addition, the more blood you give the higher the risk of
postoperative organ system dysfunction, including the risk of
transfusion-relatedacutelunginjury(TRALI)andmortality.
Do not forget that rehydration with crystalloids may unmask chronic
anemiaasthehematocritfallswithvolumeexpansion.
Suggestedstepsinvolumeoptimization
•
Institute intravenous fluid therapy and if signs of intestinal
dysfunction such as nausea,vomiting or abdominal distensionare
present then designate nil per mouth (NPO) and, if necessary,
nasogastric suction. Intravenous crystalloid may be started at a
basicrate of 100to 200ml perhourwith theadditionof bolusesof
250to500mlgivenoverintervals of 15 to 30 minutes. Weadvise
you,however,tositbyyourpatient…
•
Institute procedures for monitoring the effectiveness of treatment
including serial physical exam, Foley catheter placement and, in
moreseverecases,centralvenouscatheterplacement.
•
If the main underlying problem is hemorrhage, institute transfusion
of packed red blood cells — typed and cross-matched if there is
time, type-specific only if there is not. (Add blood components as
necessary.)
•
Titrate the rate of fluid administration in light of the results of
monitoring.Increaseordecreasethebasicrateoffluidflowandgive
additionalbolusinfusionsasnecessary.
•
After the restoration of intravascular fluid volume, address any
residual signs of physiologic dysfunction with inotropic agents to
improvecardiacoutputand,possibly,anafterload-reducingagentto
improve myocardial oxygen supply and ease the workload of the
heart.
•
Wheelthepatientdirectlytotheoperatingroomyourself.Donotwait
fortheporter—aren’ttheyusuallylate?
•
Ifthebasicproblemiscontinuinghemorrhagethenforgetthis
listandgodirectlytotheoperatingroom.Thebestresuscitation
in actively bleeding patients is surgical control of the source. In
addition, pre-operative over-resuscitation and transfusion
increasethebloodloss.
Whenisenoughenough?
The above steps in optimization are done with the aim of correcting
physiologicderangementasmuchaspossiblebutwithoutunnecessarily
delaying operative intervention. There is no magic formula for
achievingthisbalance.Thediseaseprocessitselfwilldeterminethe
duration of pre-operative optimization. At one end of the spectrum,
uncontrolled hemorrhage will require immediate operative intervention
afteronlypartialfluidresuscitationornoneatall.Attheotherendofthe
spectrum, intestinal obstruction that has been developing over several
dayswill requirea morecomplete resuscitationprior tooperation.Asin
life in general, most cases will fall somewhere in between — which
meansaround3hours.Stubbornattemptsto‘improve’a‘non-responder’
beyond6 hours are usually counter-productive.That you, or your boss,
do not feel like leaving your warm beds at 3 a.m. is not an excuse to
“continueaggressiveresuscitation”untilsunrise.
Butstop!Perhapsyourpatientdoesnotneedanoperation?One
ofthecleverestaphorismsinsurgerywascoinedbythelateFrancis
D.Moore:“Neveroperateonapatientwhoisgettingrapidlybetter
orrapidlyworse.”
Sofinallytorecap…
The key to pre-operative optimization in emergency surgery is
oxygenation of the blood and intravenous fluid resuscitation with
crystalloidsolutions.Theonlygoalofresuscitationistherestorationof
adequate tissue perfusion to supply oxygen to the suffocating
mitochondria. Accomplish it aggressively to reduce intra-operative and
postoperativecomplications.
These old folks maintain a fragile system quite well… until it gets
disturbed—likeahouseofcards.
“Everyoperationisanexperimentinphysiology.”
TidKommer
From the Editors: a few more words on the dangers of overresuscitation
Weagree thatrestoringbloodvolumeis acrucialstepbeforeany emergencyoperationbutat
thesametimewehavetowarnyou—aswe’lldoagainandagain—nottodrownyour
patients in too much fluid. Pre-operative, intra-operative, or postoperative fluid
administration can cut both ways. Equipped with huge-bore i.v. lines and fancy monitoring
devices, enthusiastic surgeons and anesthetists commonly flood their patients with too much
water and salt. We tend to ignore the ‘obligatory’ postoperative weight gain caused by over
aggressiveresuscitationwithashrug:“Well,”wesay,“thepatientisperfusingwellandhisurine
outputisexcellent—he’lldiuresetheexcessfluidsoncehe’swell.”Butwearewrong!
Accumulatingevidenceshowsthatthedeleteriouseffectofexcessfluidisnotlimitedtopatients
whoareactivelybleeding(byincreasingtherateofhemorrhageandtheriskofrebleeding)but
can,in fact, be demonstratedin all ofour patients. Swollen,edematouscellsare
bad news in each and every system. Edema contributes to
respiratory failure and cardiac dysfunction. It prevents tissue
healing — adversely affecting intestinal anastomoses and
abdominalclosure.It swells abdominal contents producing intraabdominalhypertension.
Sodonot gooverboard!Giveonlyasmuchfluid asisnecessary
and,aboveall,monitorwhattheanesthetistisdoingonhissideof
thescreen. The old-fashioned formulas used to calculate how much fluid to administer
duringtheoperationareexaggeratedandoutdated.Onehastoreplacebloodlossandmaintain
urineoutputat0.5ml/kgperhour,whichpracticallymeansbetween30-50ccperhour—nothing
more. The more unnecessary fluid given before and during the
operation—themoreproblemsyou’llhavewiththepatientinthe
ICUandonthefloor(ontheward,fornon-USsurgeons!).
Resuscitationinthetraumatizedorbleedingpatient
WehavetoforgetwhattheATLScourses(andbook)previouslytaughtus—tofloodthepatient
withcrystalloids.Todayweknowthatoverlyaggressivefluidresuscitation‘washes’outtheclot,
disturbs hemostasis, increases bleeding and decreases survival. Hence, the current
paradigm is ‘hypotensive resuscitation’ — keep the blood
pressure just high enough to preserve vital organ perfusion. In
practicalterms—donotaimfor‘normal’bloodpressurebutkeepsystolicataround90mmHg.
In actively bleeding patients start slowly with Ringer’s lactate (do not ‘pump’ it in) and then
switch to blood. Recent studies suggest that whole fresh blood is better than component
therapy.Butifyou haveto transfusemorethan twounitsof packed
red blood cells, growing evidence suggests that mortality and
morbidity rates are improved by adding one unit of fresh frozen
plasma,andoneunitofplateletsforeachunitofbloodgiven.
Thisisequallytruefortheinjuredpatient,theonebleedingfrom his ulcer and the one with a
rupturedaorticaneurysm!
Fora‘classification’oftheurgencyofthecasesee Table6.1.TheEditors
Chapter7
Pre-operativeantibiotics
MosheSchein
Mostmendieoftheirremedies,notoftheirdiseases.
Molière
CurmudgeonistheguywhogetsupattheM&Mmeeting,
after you describe your brilliant save with an ER
thoracotomyforthoracoabdominalGSWandaskswhyyou
didnotgiveprophylacticantibiotics.
AlbertI.Alexander
Itiscommonpracticetoadministerbroad-spectrumantibioticsbeforea
laparotomy for an acute surgical condition or trauma. In this situation,
antibioticsareeithertherapeuticorprophylactic.
Therapeutic antibiotics: given for an already established, tissue-invasive,
infection(e.g.perforatedappendicitis).
Prophylactic antibiotics: administered in the absence of infection, with the
objective of reducing the anticipated incidence of infections due to existing (e.g. penetrating
injury of the colon) or potential (e.g. gastrotomy to suture a bleeding ulcer) contamination
duringtheoperativeprocedure.
It is very important to distinguish between contamination and
infection ( Chapter 13), as only the latter requires postoperative
antibiotic administration, a topic to be discussed in the postoperative
section( Chapter44).
Therapeuticantibioticsassistthesurgeonandthenaturalperitoneal
defensestoeradicateanestablishedinfection.
Prophylactic antibiotics prevent postoperative infections of the
laparotomy wound; they do notprevent pulmonaryor urinaryinfections
nor the occurrence of intra-abdominal abscesses, and should not be
administeredinanattempttodoanyofthesethings.
The overprescription of antibiotics is a modern curse for which our
patientspaythepriceintermsofmorbidityandmortalityfromantibioticassociatedcolitisandtheemergenceofresistantstrains.Allprescriptions
should be provided with a clear purpose in mind and shouldbe for as
short a duration as possible. Finally, even dummies know that
antibioticsareonly an adjunct to the proper surgical management
ofcontaminationandinfection( Chapter13).
Whenshouldyoustartantibiotics?
Therearetwoschoolsofthoughthere.Onesaysthatifintra-abdominal
contamination or infection is evident or strongly suspected preoperatively,administerantibioticsimmediately—“thesoonerthebetter”.
Incases wherethere isdelay inproceedingwiththelaparotomy, givea
second dose of pre-incisional antibiotics in the operating room. Pre-
incisional administration is best in cases where contamination is
expectedtooccurintra-operatively.Somesurgeonsbelievedifferently
and prefer to await the operative findings before giving antibiotics.
Should, for example, the acute appendicitis prove to be ‘simply
phlegmonous’( Chapter23),ortheblunttraumanotbreachthelumen
of a hollow viscus ( Chapter 32), they would avoid antibiotics
altogether. Alternatively, if contamination or infection were encountered,
they would start antibiotic therapy afew minutes afterabdominal entry,
apparently with no disadvantage. This will alsoallow propercultures to
betaken.Supportforthissecondphilosophycomesfromthesuggestion
thatantibioticsliberateendotoxinfromthekilledbacteria;thisleadssome
surgeons to believe that evacuation of pus (containing the source of
endotoxin) should be a prerequisite for commencing antimicrobial
therapy.
We, among many others, believe however, that antibiotics should
permeate the tissues at the time of the abdominal incision, because
immediatevasoconstriction at the incision site would preventantibiotics
— if given later — from reaching the operative wound. Thus, our
positionistoadministeradoseofantibioticspriortoallemergency
abdominaloperations.Wheninfectionorcontaminationisencountered,
or when contamination is expected to occur, the prophylactic or
therapeuticvalueofantibioticsisobvious.Inviewofthebeneficialeffects
of prophylactic antibiotics in certain elective, clean procedures, we
assume that the same may be true in the acutely ill patient who is
subjected to laparotomy, even in the absence of contamination or
infection. The clinical significance of any antibiotic-generated
endotoxemiaispresentlyunknown.
Not uncommonly, we observe surgeons who, in the peri-operative
chaos, forget to administer antibiotics. To compensate for their failure,
they order antibioticsafter the operation. This is utterly futile. Are dirty
hands washed before or after the meal? The fate of the operative
wound is sealed by peri-operative events, including timely
administration of antibiotics. Almost nothing done after the
operationcanchangetheoutcomeofthewound( Chapter49).
Whichantibioticstouse?
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