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CHIEF COMPLAINT: Swollen and painful left knee

HISTORY OF PRESENT ILLNESS:

This 76 year-old man presented to the hospital with complaints of left knee pain that began at approximately 10pm on the night before admission. The pain involved the entire knee, and was associated with swelling. He noted no redness or warmth to the area. He denied any trauma to the area. He had had chronic mild osteoarthritic symptoms in the left knee joint, but never required treatment. The following morning, both the pain and swelling were much worse, and he was unable to bear weight on the joint. He then presented to the Emergency Room.

REVIEW OF SYMPTOMS:

He denied any constitutional, cardiovascular, pulmonary, gastrointestinal, genitourinary, neurologic, dermatologic, musculoskeletal, endocrine, hematologic, or allergic problems prior to admission, other than as listed in the history of present illness.

PAST MEDICAL HISTORY:

Hypertension

Parkinsons disease, early stage

Benign prostatic hypertrophy, status post TURP operation

Nephrolithiasis (1970's)

Hypercholesterolemia

MEDICATIONS:

Amlodipine (Norvasc), 5mg PO QD

Hydrochlorothiazide (HCTZ), 50mg PO QD

Lisinopril (Zestril), 20mg PO QD

Atorvastatin (Lipitor), 10mg PO QD

Ropinirole (Requip), 1.5mg PO QD

ECASA, 325mg PO QD

ALLERGIES:

No known drug allergies.

SOCIAL HISTORY:

The patient denied tobacco or drug use. He consumes two or three glasses of wine per week.

The patient lives alone in an assisted living facility, and is retired.

FAMILY HISTORY:

None.

PHYSICAL EXAM:

Temp=37°C

RR=12

BP=150/70

SaO2= 99%/RA

HR=72

General: No acute distress

HEENT: Oropharynx clear, mucous membranes moist

CVS: Regular rhythm, no audible murmurs, gallops, or rubs

Lungs: CTA bilaterally

Abd: Soft, mildly obese, NT/ND, +BS

Extr. The patient had his left knee positioned at about 10 degrees of flexion with a pillow underneath it. The joint was grossly swollen with significant suprapatellar effusion. There was mild warmth to the area but no erythema. The joint was diffusely tender on palpation, and tenderness worsened with full joint extension. There was no tenderness along the tibial plateau, medial collateral ligament, or the patellar tendon. The right knee was unremarkable. The remainder of the extremity exam was within normal limits-there were strong distal pulses, normal sensation, no pre-tibial edema or other significant joint findings.

LABS:

CBC: WBC count: 12,700 mer mlL

Hemoglobin: 15.2g/dL

Hematocrit: 45.1%

Platelet count: 163,000 per mL

Differential: 83% Granulocytes/3% band forms/6% Lymphocytes/7% Monocytes/1% Eosinophils

Chem 7:

Sodium: 140 mmol/L

Chloride: 102 mmol/L

BUN: 18mg/dL

Glucose: 137 mg/dL

Potassium: 4.4mmol/L

Bicarbonate: 28 mmol/L

Creatinine: 1.4 mg/dL

Urinalysis was within normal limits. Blood cultures and urine cultures were sent.

EMERGENCY ROOM COURSE:

The patients left knee effusion was tapped. Fluid was sent for the following analyses:

Fluid type: synovial

Appearance: cloudy

BF color: yellow

Nucleated cell count: 48,000 (89% neutrophils, 11% monocytes)

RBC count: 11,400

Crystals: none

Gram stain: 4+ polymorphonuclear cells, no organisms seen; cultures sent

The patient was treated in the ER with Indocin 50 mg PO x1, and Tylenol #3 PO x2.

HOSPITAL COURSE:

The patient was admitted to the medical service and was treated with nafcillin 1 gram IV Q4H and ceftriaxone 1 gram IV Q24H for presumed bacterial monoarthritis, with percocet for analgesia and ibuprofen as an anti-inflammatory agent. His other home medications were continued.

On Hospital Day#1, the patients creatinine increased to 1.7. That same day, approximately 24 hours after admission, 1 out of 2 blood cultures came back positive for gram positive bacteria in chains, suggestive of Streptococcus. Preliminary results on the synovial fluid culture came back at the same time, for 1+ betahemolytic Streptococcus Group B. Later in the day the patient developed some nausea and had emesis of stomach contents.

On Hospital Day#2, the patient's BUN increased from 21 to 55, and the creatinine increased from 1.7 to 6.4.

On Hospital Day#3, the patient exhibited some confusion/delirium. His blood and synovial cultures returned with betahemolytic Streptococcus Group B demonstrating ampicillin sensitivity. Culture of the urine from admission came back with

On Hospital Day#4, Infectious Disease consultation recommended continuing vancomycin and asking orthopedic surgery to evaluate for open drainage.

On Hospital Day#5, orthopedic surgery was consulted, and arthroscopic debridement and drainage with indwelling suction drain placement was recommended and then performed the same day under GETA, without complication.

The remainder of the patients clinical course included a rise in the creatinine to a peak value of 8.9, and then gradual decrease over several days to 3.0. His symptoms of delirium cleared with stabilization of his renal function and treatment of his infection. Physical therapy for the left knee was begun on POD #3 (after removal of the wound vac) and the patient was encouraged to ambulate. Rheumatology made recommendations regarding the duration of IV antibiotics. Transthoracic echocardiogram showed normal LV function with no evidence of vegetations. On HD#8, the patient developed abdominal pain and distention and on placement of a nasogastric tube was found to have >2 liters of gastric fluid aspirated. Two days later, black liquid was aspirated from the NG tube and the hemoglobin dropped a total of 3.7 grams over the hospital stay. EGD showed a Dieulafoy's lesion that was clipped x3, and some scattered superficial gastric ulcers and duodenal erosions; the patient was subsequently treated with a proton pump inhibitor. Also during his hospital stay, the patient developed a diffuse erythematous maculopapular rash consistent with vancomycin reaction; the dose and infusion rate were decreased. A total of 14 days of IV vancomycin was given in the hospital. The patient was discharged to home, and a further 7 days of IV vancomycin were administered at home via a PICC line. he was able to ambulate short distances with a walker at the time of discharge.

DIAGNOSIS:

Septic Monoarticular Arthritis, beta-hemolytic Streptococcus Group B

DISCUSSION:

1. What is the utility of radiologic imaging for diagnosing or managing septic arthritis?

Diagnosis of septic arthritis is generally done with careful history and physical examination, along with analysis of the synovial fluid, and not with the aid of a radiologic study. In the acute setting, an inflammatory or septic arthritis generally will have no abnormal findings on a plain radiograph that aid in diagnosis other than soft tissue swelling. Abnormalities such as fractures, underlying osteoarthritis, and tumors may be visible, however. Magnetic resonance imaging (MRI) is of greater utility than other modes of radiologic imaging because it can help detect meniscal tears and other pathologic joint findings, and can help localize areas of inflammation and infection to either the joint or the surrounding tissues. The extent of joint involvement and determination if either effusion, synovitis, or both are present can be made by MRI. Additionally, it can assist in determining if local bony inflammation is present, which commonly accompanies septic arthritis and may be suggestive of underlying osteomyelitis. This information is particularly useful in a patient who may undergo surgical synovectomy. Lastly, MRI may assist in diagnosis of septic arthritis at an unusual location, such as in the sacroiliac joint.

Baker DG, Schumaker HR. Acute monarthrirk NEJM 1993; 329:1013-20.

Forrester DM, Feske, WI, (1990). Imaging of infectious arthritis. Sem In Roent 1996; 30:239-49.

McNally E. Magnetic resonance imaging of the knee. BMJ 2002;325:115-6.

2. What are the usual pathogenic organisms in septic arthritis, and what should empiric antibiotic treatment consist of?

The most common etiologic organism in septic arthritis is Neisseriagonorrhoeae, although this varies among populations, gender (female>male), and age (young>old). About 80% of nongonococcal bacterial joint infections involve a single joint and are caused by gram-positive aerobic organisms, generally via hematogenous spread from a primary infection site which is often the skin. Staphylococcus aureus is the most common nongonococcal bacterial pathogen in septic arthritis [60% of cases], especially in the setting of underlying diseases such as diabetes and rheumatoid arthritis, and is associated with a high level of joint destruction. Other common gram-positive aerobes associated with septic arthritis are beta-hemolytic Streptococcus (Groups A, B, C, F, and G) [15%], and Streptococcus pneumoniae [3%]. Patients with beta-hemolytic Streptococcus Group B septic arthritis often present without fever, tend to have a less acute course than other pathogens (in one study, patients had a median of 5 days of symptoms prior to admission), have more severe symptoms of pain, and often have an underlying malignancy. Staphylococcus epidermidis is often associated with infection of bioprosthetic joints.

Less commonly, other infectious pathogens have been associated with septic arthritis. Gram-negative bacilli can occasionally be causative agents. Acute tuberculous arthritis can occur, but is more likely to present as a chronic syndrome. It is usually diagnosed by synovial biopsy. Fungal arthritis may also present with a chronic monarthritis. Mycobacterial and fungal joint infections are much more common in the immunocompromised. Lyme disease may present as a monarthritis, frequently of the knee, and is associated with recurrent large joint effusions that may recede spontaneously without antibiotics. Viral arthritis infrequently involves only a single joint; common implicated viruses include rubella, hepatitis B and C, and parvovirus B19. Up to 15% of cases of infective endocarditis will be associated with bone or joint infection. Reactive arthritis and post-streptococcal arthritis involve sterile inflammation of the joint associated with bacterial infection at a distant site. Case reports suggest septic arthritis can occur infrequently with other organisms as well.

Empiric antibiotic therapy should be based on the synovial fluid gram stain, however if that is uninformative it is generally recommended to begin nafcillin or oxacillin in combination with a 3rd-generation cephalosporin to cover the most frequent pathogens. Neisseria gonorrhoeae is infrequently isolated from the joint, and other sites should be cultured in cases with high suspicion (e.g. urethra, cervix).

Baker DG, Schumaker HR. loc. at.

Goldenberg D. Septic arthritis. Lancet 1998;351:197-202.

Sack K. Monarthritis: Differential diagnosis. AJM 1997;102(1A) Suppl: 30S-40S.

Schattner A, Vosti K. Bacterial arthritis due to Beta-Hemolytic Streptococci of Serogroups A, B, C, F, and G. Medicine 1998;77:122-39.

3. What is the usual duration of antibiotic therapy in septic arthritis?

If the synovial fluid gram stain is negative (uninformative), then empiric therapy for methicillin-resistant Staphylococcus aureus and streptococci should be initiated, which usually consists of a second- or third-generation cephalosporin and nafcillin given intravenously. With an informative gram stain, antimicrobial therapy can be more specifically directed based on the organism identified. A high-level of suspicion for Neisseria gonorrhoeae should prod the investigator to identify the organism at another site (e.g. urethral or cervical culture, etc.) as it is infrequently identified from synovial fluid [

Baker DG, Schumaker HR. loc.cit.

Goldenberg D. loc.cit.

4. What is the indication for arthroscopic debridement and drainage in septic arthritis, and when is the optimal time for the procedure?

Complete drainage of the joint cavity is always indicated in septic arthritis. During the initial course of treatment a patient may require daily needle aspiration. In shoulder and knee infections, either arthroscopy or open arthrotomy with drainage is indicated immediately so that adequate irrigation can be performed. Open arthrotomy is indicated when the hip joint is involved. In any infected bioprosthetic joint, all mechanical components must be surgically removed, the area debrided, and replacement arthroplasty be repeated at a later date. Timely joint drainage, as well as initiation of physical therapy and joint mobility exercises, is important in reducing morbidity associated with septic arthritis.

Baker DG, Schumaker HR loc.cit.

Goldenberg D. loc.cit.

Thiery JA. Arthroscopic drainage in septic arthritides of the knee. Arthroscopy 1989;5:65-9.

5. What is the prognosis in septic arthritis?

Overall outcome in patients with septic arthritis is poor, both from the standpoint of the patient and the joint. One review of the literature (Kaandorp et al) quotes data that septic arthritis is associated with a mortality rate of 10-15%, and that up to 2550% of surviving patients have irreversible functional loss of the involved joint. Comorbid illness/joint disease and infection of a bioprosthesis tends to bode for a worse outcome, especially in the immunosuppressed and the elderly. Additionally, prolonged hospitalization associated with therapy and surgical intervention add to the significant financial burden of the diagnosis.

Kaandorp CJE, Krijnen P. et al. The outcome of bacterial arthritis. Arthr Rheum 1970; 40:884-92.

Schatcner A, Vosti K. loc.cit.

JOHN E. SNYDER, MS, MD

CORRESPONDENCE:

John Snyder, MS, MD

e-mail: johnsnyder@comcast.net

Copyright Rhode Island Medical Society Jul 2004
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