Surgical Infections - MU

• Surgical infections are infections of the tissues, organs, or spaces exposed during an invasive surgical procedure.

Surgical Site Infections (SSIs)

• After an operation, SSIs can occur
• Defined as infections of the tissues, organs or spaces exposed during the performance of an invasive surgical procedure.
• They are classified into 3 types:
  • Incisional: Affecting the skin and subcutaneous tissues (superficial) or involving deeper musculoaponeurotic layers.
  • Organs
  • Spaces: Such as subphrenic, pelvic, or interloop abscesses.

Etiology (Predisposing Factors)

• General host factors include old age, obesity, anemia, malnutrition, immunosuppression (like in diabetes, uremia, malignancy), and intake of immunosuppressive drugs (corticosteroids, chemotherapy).
• Local factors include poor skin preparation, poor blood supply (prolonged hypotension, tissues sutured under tension), prolonged surgery, foreign bodies/prosthetic material, instrument sterilization defects, improper surgical technique (dead spaces, hematoma, diathermy use, rough handling), and the nature of the operation itself.
• The nature of the operation is the most important factor determining SSIs.
• Operative wounds are classified based on contamination level:
  • Clean: Elective, non-traumatic wounds without entry into gastrointestinal, urinary, or respiratory tracts. Risk of SSI is less than 2%.
  • Clean Contaminated: Elective surgery entering gastrointestinal (stomach & jejunum), urinary, or respiratory tracts without significant spillage. Risk is 2-5%.
  • Contaminated: Includes open accidental wounds within 4 hours, gross spillage from the gastrointestinal tract, or incisions through inflamed, non-purulent tissues. Risk is 10-20%.
  • Dirty: Traumatic wounds over 4 hours old, purulent infection, necrotizing soft tissue infection, or perforated viscus with high contamination (peritonitis). Risk is 40%.

Clinical Features of Surgical Site Infections

• SSIs usually appear between the 5th and 10th days post-operation.
• Earliest signs are increasing wound pain and postoperative fever.
• The wound may be swollen with sutures dipping, tender, and red.
• Fluctuant areas or crepitus may be felt.
• Discharge might be seen from the wound.
• Recognize that deep infections are difficult to recognize and are associated with systemic signs of infection.

Prophylaxis

• Correct any predisposing factors by controlling diabetes, stopping smoking, and correcting nutritional deficiencies.
• Avoid operations in patients with active infections if possible.
• Shave or clip hairs just before skin incision.
• Prepare skin with antiseptics.
• Surgeons should have short nails and scrub properly.
• Use meticulous surgical techniques with adequate hemostasis, gentle tissue handling, and avoiding tight sutures or dead space.
• Delay primary closure of heavily contaminated wounds.

Prophylactic Antibiotics

• A brief course of antibiotics just before the operation.
• Use in clean surgery only if prosthetic materials are implanted or if the patient has a high risk of infection (old age, obese, smoker, immunocompromised).
• In all classes of contaminated surgery.
  • Give antibiotics pre-operatively one hour before surgery and in the early post-operative period.
  • Further doses depend on the degree of wound contamination.
  • First-generation cephalosporin (cephazolin) is commonly used.

Treatment

• Liberal drainage involves opening the wound and removing skin stitches.
• Antibiotics are used if there's evidence of invasive infections (temperature >38.5°C, erythema >5cm, leukocytic count >11,000). Administer antibiotics based on culture and sensitivity tests.
• Correct sources of hospital-acquired infection being traceable.

Erysipelas

• Definition: Diffuse streptococcal infection of the superficial lymphatics of the skin.
• Etiology: Wounds & abrasions on hand, face, & scrotum.
• Predisposing Factors: Bad general health and debilitating diseases.

Complications of Erysipelas

• Recurrent lymphangitis with lymphatic obstruction & elephantiasis.
• Septicaemia and pyaemia.
• Cavernous sinus thrombosis in facial erysipelas.

Clinical Presentation

• General signs include constitutional manifestations (FAHM).
• Local signs include:
  • A rose-pink rash that itches and spreads rapidly.
  • A well-defined, irregular, and raised advancing edge.
  • Minute vesicles are often present.
  • The affected area is both painful and tender.

Differential Diagnosis

• Cellulitis: Rash that is rose pink with an elevated edge. Affected the face and auricle. There may be islets of inflammation beyond the spreading margin separated from the main area by apparently normal skin.

Treatment

• Improve general health with diet, tonics, and vitamins.
• Use antibiotics (penicillin) intravenously in severe cases.
• Apply local ichthyol ointment to soothe the itching.

Tetanus

• Definition: A specific anaerobic infection mediated by the neurotoxin of Clostridium tetani, which leads to nervous irritability and tetanic muscular contractions. It is becoming less prevalent due to immunization.

Etiology

• The causative organism, Clostridium tetani, is a gram-positive anaerobic bacillus with a terminal spore. It has a drum-stick appearance.
• Naturally present in the intestine of horses.
• Spores are found in manured soil and street dirt.

Mode Of Infection

• Wounds:
  • The organism enters and flourishes in hypoxic wounds contaminated with soil or feces.
  • Tetanus-prone wounds are typically puncture wounds or those containing devitalized tissue, foreign bodies, or pyogenic organisms with reduced blood supply.
• Umbilical stump:
  • Tetanus neonatorum arises from infection of the umbilical stump by contaminated dressings or powders.

Pathology

• Bacillus remains at the inoculation site, but its exotoxin reaches the CNS via the bloodstream and/or motor nerves.
• Once the toxin reaches the nervous system, it is fixed by motor cells and is not detectable in the blood or CSF.
• Tetanus antitoxin can only neutralize the toxin before it fixes to nervous tissue.
• The toxin increases excitability of the motor cells, leading to violent spasms from even the slightest stimuli.
• Death results from exhaustion, hyperpyrexia, heart failure, asphyxia, or pneumonia.

Clinical Presentation

• Incubation Period: Varies from 24 hours to 15 days.
• Tonic Stage:
  • Initial symptoms: pain and tingling in area of injury.
  • Limitation of jaw movements (lock jaw, trismus) is the earliest sign.
  • Spasm of facial muscles (risus sardonicus), often sparing limbs.
  • Followed by: stiffness of the neck, difficulty in swallowing and laryngospasm, and hesitancy in micturition due to sphincter spasm.
• Clonic Stage (Convulsions):
  • Attacks of convulsions are superimposed on tonic rigidity after a few days.
  • Spontaneous or induced by minor stimuli (noise, light, air draught, and movement).
  • OPISTHOTONUS is the typical posture.
  • Spasms of intercostal muscles and diaphragm lead to longer periods of apnea.
  • Temperature is normal or slightly elevated, with profuse sweating.
  • Marked tachycardia is a grave sign.

Differential Diagnosis

• Trismus- exclusion by proper examination
• Meningitis- neck rigidity, CSF is diagnostic
• Strychnine poisoning- convulsions relax, no tonic rigidity
• Tetany has carpopedal spasms, positive Chvostek's and Trousseau's signs, and low serum calcium.
• Rabies- dog bite and hydrophobia

Prevention of Tetanus

• Every child should be immunized by routine DPT vaccine at 2, 4, 6 months, with a booster dose of tetanus toxoid every 7-10 years.
• So according to these facts, there are 3 possibilities for prevention:
• 3 or more doses of toxoid with last dose within 10 years: Booster dose of TT (0.5 ml IM).
• Less than 3 previous doses:
  • With clean minor wounds, only tetanus toxoid is needed.
  • For wounds at high risk of tetanus, both TT and tetanus IG are given.
• Not previously immunized:
  • With clean minor wounds, only tetanus toxoid is needed but 3 doses at 4-6 weeks interval and antibiotic
  • High risk of tetanus - TT (3 doses) + tetanus IG (7500 U IM). plus antibiotics

Treating Established Cases

• Neutralize toxin:
  • Administer 3000-6000 IU of TIG IM to limit further fixation of exotoxin in CNS.
  • Repeated doses since the half-life of AB is 3 weeks, and tetanus lasts longer.
• Control Convulsions:
  • In mild cases, promazine or barbiturate is sufficient
  • In severe cases, muscle relaxant (Curare or Flaxedyl) and maintained on artificial respiration until no further convulsions occur.
• Highly Efficient Nursing Care:
  • Darkened room
  • Observation of respiration
  • Nutrition maintained by a Ryle's tube
  • Prophylactic antibiotics are essential
  • Saline if Dehydrated
• Large doses of penicillin or tetracycline.

Local Treatment

• Wound excision.
• Irrigate with hydrogen peroxide.

Prognosis

• Overall Poor
• Conditions dependendant on previous immunization, wounds in face or scalp, short incubation period.

Gas Gangrene

• Definition: Acute clostridial myositis, associated with gas formation and ends in gangrene.
• Etiology: Clostridia of gas gangrene are obligatory anaerobes, spore-bearing, gram-positive bacilli, motile and non-capsulated (except Clostridium welchii).
• Divided into two groups: saccharolytic and proteolytic.
• Anaerobic environment facilitated by bruised lacerated muscles, especially bulky and deep muscles of the buttocks and thighs.
• Organisms normally present in bowel. Thighs and buttocks particularly affected
• Organisms prefer bulky, deep muscles of the buttock and thigh.*

Pathology

• Saccharolytic group plays the primary role, causing muscle necrosis, thrombosis, and hemolysis through exotoxins that ferment glycogen, releasing CO₂ and hydrogen gases.
• Proteolytic organisms play a secondary role, attacking and flourishing on dead muscles, splitting protein into ammonia and hydrogen sulfide (causing the musty odor).

Clinical Presentation

• Incubation Period: 24-48 hours.
• General Features: Patient is pale, anxious, and alert, with rapid pulse
• Local Features: Tense limb, mottled skin, foul brown discharge, loss of contractility, gas on X-Ray
• Evidence occurs under Plaster of Paris

Diagnosis

• Simple contamination*
• Diagnosis with clostridial cellulitis
• Dx with localyzed myositis

Prophylaxis

• Proper surgical technique.
• Prophylactic penicillin.
• Polyvalent anti-gas gangrene serum in wounds of buttocks and thighs.

Treatment

• Rapid resuscitation.
• Polyvalent anti-gas gangrene serum.
• Crystalline penicillin.
• Hyperbaric oxygen therapy.
• High amputation with gas extraction.
• Proximal diversion if Colon is site.