Clinical presentation and diagnosis

Intra-abdominal infections have a wide spectrum of clinical features. Peritonitis usually is easily recognized, but intra-abdominal abscess often may continue unrecognized for long periods of time. Patients with primary and secondary peritonitis present quite differently.

treatment Desired Outcomes

The primary goals of treatment are correction of the intra-abdominal disease processes or injuries that have caused infection and drainage of collections of purulent material (abscess). A secondary objective is to resolve the infection without major organ system complications (e.g., pulmonary, hepatic, cardiovascular, or renal failure) or adverse drug effects. Ideally, the patient should be discharged from the hospital with full function for self-care and routine daily activities.

Clinical Presentation of Secondary Peritonitis General

Patients may be in acute distress. Symptoms

• Patients may complain of nausea, vomiting, and generalized abdominal pain.

• Patients may demonstrate abdominal guarding and a "boardlike abdomen." Signs

• Tachypnea and tachycardia are present.

• Temperature is normal initially, then may increase to 100°F to 102°F (37.7-38.9°C) within the first few hours, and may continue to rise for the next several hours.

• Hypotension and shock may develop if intravascular volume is not restored.

• Decreased urine output may develop owing to dehydration.

• Bowel sounds are faint initially and eventually cease. Laboratory Tests

• The WBC is high (WBCs 15-20 x 103/mm3 [15-20 x 109/L]), with neutrophils predominating and an elevated percentage of immature neutrophils (bands).

• The hematocrit and blood urea nitrogen increase because of dehydration.

Hyperventilation and vomiting result in early alkalosis, which changes to acidosis and lactic academia to reduced intravascular volume and diminished tissue perfusion.

Other Diagnostic Tests

Abdominal radiographs may be useful because free air in the abdomen (indicating intestinal perforation) or distension of the small or large bowel is often evident.

General Approach to Treatment

The treatment of intra-abdominal infection most often requires the coordinated use of three major modalities: (a) prompt drainage; (b) support of vital functions; and (c) appropriate antimicrobial therapy to treat infection not eradicated by surgery.14 Antimicrobials are an important adjunct to drainage procedures in the treatment of secondary intra-abdominal infections; however, the use of antimicrobial agents without surgical intervention usually is inadequate. For most cases of primary peritonitis, drainage procedures may not be required, and antimicrobial agents become the mainstay of therapy.

Patient Encounter 1, Part 2: Physical Examination and Diagnostic Tests PE:

The patient is found responsive but in acute distress. He is lying on the examination table with knees drawn up to his chest. There is involuntary abdominal guarding with a rigid abdomen. There are no audible bowel sounds. He is alert and oriented times 3. Neurologic function is intact. Mucous membranes are dry. Stool is heme-negative.

VS: T 101°F (38.3°C), BP 105/70 mm Hg, P 132 bpm, wt 82 kg (180 lb), ht 5'7" (170 cm), RR 24 per minute.

Labs: Hct 46% (0.46 volume fraction), Hgb 15.4 g/dL (154 g/L or 9.5 mmol/L), WBC count 15.2 x 103/mm3 (15.2 x 109/L) (45% neutrophils, 20% bands)

Serum: Glucose 213 mg/dL (11.8 mmol/L), serum creatinine 1.9 mg/dL (168 ^mol/L), BUN 42 g/dL (15 mmol/L), Na 138 mEq/L (138 mmol/L), K 3.7 mEq/L (3.7 mmol/ L), Cl 101 mEq/L (101 mmol/L), CO2 21 mEq/L (21 mmol/L), calcium 9.8 mg/dL (2.45 mmol/L), magnesium 2.0 mEq/L (1.0 mmol/L), total bilirubin 0.4 mg/dL (6.84 ^mol/L), albumin 4.2 g/dL (42 g/L), lactic acid 3.2 mEq/L (3.2 mmol/L)

KUB: An upright abdominal x-ray shows dilated loops of small bowel and free air under the diaphragm.

DPL (diagnostic peritoneal lavage: examination of fluid in peritoneal cavity): No blood is found, but WBCs are evident.

Develop a care plan for this patient for the first 7 days of his hospitalization. This plan should include specific drug recommendations, and monitoring parameters to evaluate outcome.

In the early phase of serious intra-abdominal infections, attention should be given to preserving major organ system function. With generalized peritonitis, large volumes of IV fluids are required to maintain intravascular volume, to improve cardiovascular function, and to ensure adequate tissue perfusion and oxygenation. Adequate urine output should be maintained to ensure appropriate fluid resuscitation and to preserve renal function. A common cause of early death is hypovolemic shock caused by inadequate intravascular volume expansion and tissue perfusion.

An additional important component of therapy is nutrition. Intra-abdominal infections often involve the GI tract directly or disrupt its function (paralytic ileus). The return of GI motility may take days, weeks, and occasionally, months. In the interim, enteral or parenteral nutrition as indicated facilitates improved immune function and wound healing to ensure recovery.

Patient Encounter 2, Part 2

A sample of dialysate fluid was found to be cloudy. A spun specimen had numerous white cells and gram-positive cocci on gram stain.

Suggest an initial regimen for this patient (agent, dose, and route of administration).

What are some factors that would be considered when deciding the route of antimicrobial administration for this patient?

How long should the antimicrobial be continued?

What can be done to prevent future infections like this?

Nonpharmacologic Therapy

Drainage Procedures

Primary peritonitis is treated with antimicrobials and rarely requires drainage. Secondary peritonitis requires surgical removal of the inflamed or gangrenous tissue to prevent further bacterial contamination. If the surgical procedure is suboptimal, attempts are made to provide drainage of the infected or gangrenous structures.

The drainage of purulent material is the critical component of management of an intra-abdominal abscess. This may be performed surgically or with percutaneous image-guided techniques.15 Without adequate drainage of the abscess, antimicrobial therapy and fluid resuscitation can be expected to fail. The most valuable microbio-logic information may be obtained at the time of percutaneous or operative abscess drainage.

Fluid Therapy

In patients with peritonitis, hypovolemia is often accompanied by acidosis and large volumes of a solution such as lactated Ringer's may be required initially to restore intravascular volume. Maintenance fluids should be instituted (after intravascular volume is restored) with 0.9% sodium chloride and potassium chloride (20 mEq/L [20 mmol/L]) or 5% dextrose and 0.45% sodium chloride with potassium chloride (20 mEq/L [20 mmol/L]). The administration rate should be based on estimated daily fluid loss through urine and nasogastric suction, including 0.5 to 1.0 L for insensible fluid loss. Potassium would not be included routinely if the patient is hyperkalemic or has renal insufficiency. Aggressive fluid therapy often must be continued in the postoperative period because fluid will continue to sequester in the peritoneal cavity, bowel wall, and lumen.

Pharmacologic Therapy

Antimicrobial Therapy

The goals of antimicrobial therapy are as follows:

• To control bacteremia and prevent the establishment of metastatic foci of infection

• To reduce suppurative complications after bacterial contamination

• To prevent local spread of existing infection

After suppuration has occurred (e.g., an abscess has formed), a cure by antibiotic therapy alone is difficult to achieve; antimicrobials may serve to improve the results with surgery.

® An empirical antimicrobial regimen should be started as soon as the presence of intra-abdominal infection is suspected and before identification of the infecting organisms is complete. Therapy must be initiated based on the likely pathogens, which vary depending on the site of intra-abdominal infection and the underlying disease process. Cultures of secondary intra-abdominal infection sites generally are not useful for directing antimicrobial therapy. Table 77-1 lists the likely pathogens against which antimicrobial agents should be directed.

Antimicrobial Experience

Many studies have been conducted evaluating or comparing the effectiveness of antimicrobials for treatment of intra-abdominal infections. Substantial differences in patient outcomes from treatment with a variety of agents generally have not been demonstrated. 16

Important findings from the last 25 years of clinical trials regarding selection of antimicrobials for intra-abdominal infections are as follows:

• Antimicrobial regimens for secondary intra-abdominal infections should cover a broad spectrum of aerobic and anaerobic bacteria from the GI tract.

• Single-agent regimens (such as antianaerobic cephalosporins, extended-spectrum penicillins with P-lactamase inhibitors, or carbapenems) are as effective as combinations of aminoglycosides or fluoroquinolones with antianaerobic agents. This is also true for antimicrobial treatment of acute bacterial contamination from penetrating abdominal trauma.

• Clindamycin and metronidazole appear to be equivalent in efficacy when combined with agents effective against aerobic gram-negative bacilli (e.g., gentamicin or aztreonam).

• For most patients, antimicrobial treatment can be completed orally with amoxicil-lin-clavulanate or the combination of ciprofloxacin and metronidazole.

• Five to seven days of antimicrobial treatment are sufficient for most intra-abdom-inal infections of mild to moderate severity.

Intra-abdominal infection presents in many different ways and with a wide spectrum of severity. The antibiotic regimen employed and duration of treatment depend on the specific clinical circumstances (i.e., the nature of the underlying disease process and the condition of the patient).

Recommendations

® For most intra-abdominal infections, the antimicrobial regimen should be effective against both aerobic and anaerobic bacteria.17 Although it is impossible to provide antimicrobial activity against every possible pathogen, agents with activity against enteric gram-negative bacilli, such as E. coli and Klebsiella, and anaerobes, such as B. fragilis and Clostridia spp., should be administered.

Table 77-2 presents the recommended agents for treatment of community-acquired and complicated intra-abdominal infections from the Infectious Diseases Society of America and the Surgical Infection Society.18,19 These recommendations were formulated using an evidence-based approach. Most community-acquired infections are "mild to moderate," whereas health care-associated infections tend to be more severe and difficult to treat. Table 77-3 presents guidelines for treatment and alternative regimens for specific situations. These are general guidelines; there are many factors that cannot be incorporated into such a table.

Table 77-1 Likely Intra-Abdominal Pathogens

Table 77-2 presents the recommended agents for treatment of community-acquired and complicated intra-abdominal infections from the Infectious Diseases Society of America and the Surgical Infection Society.18,19 These recommendations were formulated using an evidence-based approach. Most community-acquired infections are "mild to moderate," whereas health care-associated infections tend to be more severe and difficult to treat. Table 77-3 presents guidelines for treatment and alternative regimens for specific situations. These are general guidelines; there are many factors that cannot be incorporated into such a table.

Table 77-1 Likely Intra-Abdominal Pathogens

Typiof Infection

MrtbH

AnHnhi

Primary J>»riti>nlTlt

Chlldien (spontaneous)

Citojfi A Slieptoccxciii. f-Hrhwiciiiij tiWi pneti/rvxocct

(ifhoiii

£. cofl «rtwJIft poewmOC«i j (murry onhCfs)

-

ftoriConiMl tfaly»

Ssoptytococcui. Sfrepioraccus

-

StCdniliry BjLltri Jl PtilUAllll

(iaH loduudenal

SilipltKBCIUl. F.cort

-

Sftarylfifi

f. rofi H?tK)iHia m&o((HX>

CkRcrtilum or (tocrwidt*; (infrequent)

Small Jjrgo bowel

f. avi «t tsu'iis wi, frowus seo.

(iiniefiiki«iri^iiivaiy(tiiiic< (txieitAJei;

ClOsiriilniiTi

ApoefidkHis

f, Mil f^turt^nonss

BQilvOktii unt

Abicesses

f. coli fcfebsirfVj. enliraoccJ

il. IfogWiarMj-Dthci BacteroMeSi

CKHjiWIum. onseKXiiC COCCI

i.lwf

f. coft Wtbv(Hlj. mUerococci iiop^toraccio™eiH

HinttrokJos {infiLtiuunO

Spleen

itaptiftecoccui, StKpbxoccui

Fiom inPiroJT.Talberl W, YeetiCeL .il„ (edsj Phaimacol h«apy. A Pathophysiologic Approach 7th edL Hew York: McGraw Hill; XW6.

Fiom inPiroJT.Talberl W, YeetiCeL .il„ (edsj Phaimacol h«apy. A Pathophysiologic Approach 7th edL Hew York: McGraw Hill; XW6.

Table 77-2 Recommended Agents for the Treatment of Community-Acquired Complicated Intra-Abdominal Infections

Agents RLaLamniLand«J IrSr Mrld 14 Moderate Infeetliiftl

Agentt Rttommendedfor High-Sntiiiy Infeciiani

0-Lactamip-Laccann lie 1 nfubltor Combinations

An>piciinn-sulbii( (am

CifftTjcj|li"p Ui-oUxtJin

Tkatcim-cl^ulanate

tiihpwmi

irtapenem

IrnipenenvtilKiifln

Merofensm

Combination Regime»}

Cefajolinor cefuianime-plut metionldaiole

Third- of fourth-generation cephalosporins (cefotaxime, ceftriaxone,

Ciprofloxacin, kvofkxucin rntii'kjjtjcin. Or ^atilknac In. In

<efiiitfliirtii_ ieftMidinw. tttcti*ii}pius ii&ettonklaioK'

combination with metniriiiLiAJli -

Ciprofloxacin, in combination inHtonklifale

Ajueonam plus metrorbda/ole

FiomBek 17 and 13.

Table 77-3 Guidelines for Initial Antimicrobial Agents for Intra-Abdominal Infections

FiomBek 17 and 13.

Table 77-3 Guidelines for Initial Antimicrobial Agents for Intra-Abdominal Infections

Primly Agents

Alternative!

Prlnl*ry Bj.:[rrJi| p^itijnltl*

EltrhoeJs Cefotaxime

Aeticcmeil (fialysis Initial eiYip'u1 recpirvns

CefcucHIrt 0* cmhalolNn plus celUikJimr o «iepin*?

Staphylococcus penic illinaieteihia™ ptriitillri tj iiist-yeneraikjn cephalosporin

Sc i pt<jcotc ut« Ente iqcocc us: ampk Jta

Arrobk grjiri ■ncgsl'fli tut ¡Ilk cef ta«J«ie a tefeplme

Pseucfc>nar\as aeruginosa: twoagents wilh dittoing niHtoniirni of actions. sutls as an 01,11 quindone plus ceftarklme, ceiepimf, (abr.mytiii.of piperacillin iMondsry BiLiiiri Jl Perlionliii

Perforated pep« uker F»st-gene:a1ion cephalosporins

Other

Imlpenem-rlllslatln, meropenem, yrtauencrn, a Onlunchxt iptiliuin pefK illins. whh j5-Lk tamase Inhibitor

1. Add clindamycin 01 metrcmlda/oip if anaerobes are suspecled

2. OD*i lhiidgeneritioii cephalosporins, emended specniim pen<»nv ajrnec<iam,and imipenem «alwrrwniw«

J. Amnoglycoside with antipseudomcnal pemcillln

1. An aminoglycoside may be used in place of ceftazidime ot cifEtitir»?

J. Imlpenenvtllsaaiin ui ceieplmsemay be used alone

1 Qulnolones maybe us«i in place of ceftazidime or cefepirne If local lUKcpHniitirs alk*v

I Alternative for meif»cillin resistant staphylococci ft vancomycin

2. Forvancom^ln reslslant iJaphj^oeotcus aweus. line/cJki. (taptoniycin, or QiHnwpriHiivdalfopriiiin must he used

1. An aminogfycowJe may be added tor entpococjcal peritonitis

2. LrfttrtikJor-tluinuyiiiiin-dtiltipriHiriihCuid beincd tOUfj! irancomycin-iesistani fraerococcus run susceptible Kiampicillln

I. fhp'egimen should be based on In vitro sensitivity tests l-Anlianaetobic cepiialosporins-1 2. P«siWy jOd jrnino^ljttMjdtif iijtientiiSikJiiioii is poo 3i Am ¡nogfyiijside with c linit.imyi in or mern^iidaioift ampEillin if palienl is immunocompromised or IbfarynQ ongMcfmfKiiGn

1. Clptoflowae In with mptronidlaTiole

2. AJIniondm with dkTCUmjtin Oi metraikliiuY; 1 Ajuianaerobic cephiiwpoiins ■

Abiceji

(ienem

Liwet Spsetn

4pp<ndl[i(ii

Normal or Inflamed

OangienotfS Of DCffofaled

Acute ti»iecviini4

CtKjldrH|ili*.

AiuieContartiiivniori intraabdominal IrJflHrkl Pelvic inflammatory dHtH

rm I pwwu-dtauiifn, mtfopenw, eriapenem, CM exiencteil-spectrum pti 'tlllirt-.- wilh JJiiirjcruv? inhibits

Ai abcw? bin add a flrit-tpnefarlon cephakjipotin Am rroglytwKle fvi pef^; illn^i W'liiiit^M pentrlllln

Antlanacrobic cephakjipofinv

{discontinued imrT*>dki(ely pxjiloDtfjIiurO

Imlpenefn-iilaiitiiln, menjperpem, arlapenem, anliarueiobk cephalunpotim of e*KfvJed-HJectrum peniciinis with Jjiac lamav mhihitnr FEntgeneiiiiini tepfkjioiisotin

Ail- iv h |lyc c»h l> ■ wilhh.iiYipkillin wilhOf without clindamycin or metronidazole

Anriaftioriifct (eiyjtHtoi W or ,sn' pkMlln-iulhv r.i?n

Cefotetan of cefoxitin with-doxy:yc line

1. AZtrOOiUm with clindamycin Of mitiofiidwole I ("ijy;il Ins.y in with in^trcinkU^e 1 Aminaqlyijoikfcwifllii.liridjiTi^in O tnitronidjiufe i. Usi memxikiirnle i amioebic livier ihK^ii suspected

1, i*Jttfmttol t<ii pcnkilliiVK Wiil^n; p^nii i Hi jro flfjt-generatfcin opphakiipcifini or vancomycin

L Atnpfcillln-sulbactam

1. Aitreonam wkfKllndamyclncf merraHdairJe

2. Clpfolkwacin with mefronkidiiole

J. Amkwg^axfdt with dlndiiijtcln t» nwfonidJiKt i. Armin-sgivtosjik? p*n .¿i«(5(cniin if stvwe infection i. tJv ■■■.irurjiriy. -l tif .imp« iI!;m if | :.bl ■ tie r. .iTenik 1Q

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