Inflammation, Wound Healing, and Infection

Anne McConville, MD

Why do we care?

Wound infection and failure remain common complications

Prolong hospitalization

Increased resource consumption

Increased costs

Increased mortality

Influenced by patient factors and perioperative management

Infection Control: Hand Hygiene

Hand Hygiene Often neglected Semmelweis first noted in with 1847: puerperal

infections Resident vs. Transient flora Even “clean” procedures can result in

contamination

Infection Control:Hand Hygiene

Various Hand Hygiene Products Plain soap and water Alcohol-based rinses and gels Chlorhexidine Iodine and iodophors

Choice depends on expected pathogen, acceptability of HCW’s, and cost (usually $1/patient day).

Infection Control: Hand Hygiene

Barriers to hand hygiene Skin irritation Inaccessibility HCW acceptance

Infection Control:Antisepsis

Masks

Caps

Sterile gloves

Drapes

Decrease OR traffic

Site of line placement

Infection Control:Antibiotic Prophylaxis

Miles et. al used guinea pig model as proof of principle for antibiotic prophylaxis

Knighten et. al assessed the use of high inspired oxygen alone and in addition to prophylactic antibiotics

Classen et. al prospective human study showed same results as Miles.

Standard for surgeries in which greater than minimal risk of infection

Infection Control:Antibiotic Prophylaxis

THA, TKA, extradural ortho and neuro spine, CT, vascular, kidney transplant: Cefazolin

Cranial and intradural spine: Ceftriaxone

Liver transplantation: Ceftriaxone

Colon surgery: Cefotetan

Vaginal and abdominal Hysterectomy: Cefazolin or Cefotetan (if bowel involved)

Dosing depends on weight, redosing interval depends on durgs used.

Discontinued by 24 hours postoperatively

Surgical Site Infections

Superficial Incisional (SSI)

Deep Incisional SSI

Organ/Space SSI

Mechanism of Wound Repair

Inflammation

Matrix production

Angiogenesis

Epithelization

Remodeling

Initial Response to Injury

Starts with skin incision creating a wound

Phases: hemostasis, inflammation, proliferation, and remodeling

Each phase is mediated by contaminants, interaction between cells, cytokines, and other chemical mediators

Initial Response to Injury: Hemostasis

Platelet aggregation and degranulation

Release of chemoattractants and growth factors

Coagulation results

Initial Response to Injury: Inflammation

Bradykinin, complement and histamine released by mast cells

PMN’s arrive almost immediately followed by macrophages in 1-2 days

WBC’s continue cycle of inflamamtion

Characterized by erythema and edema of wound edges

Proliferation

Begins about 4 days after injury

Neovasularization Angiogenesis Vasculogenesis

Collagen and Extracellular Matrix Deposition Oxygen dependent process

Epithelization

Maturation and Remodeling

Ongoing remodeling of granulation tissue and increasing tensile wound strength

Wound will never achieve tensile strength of uninjured skin/tissue

Hypertrophic and keloid scars

Wound Perfusion and Oxygenation

Ischemic or hypoxic tissue susceptible to infection and poor healing

Wound tissue oxygenation dependent on: Perfusion Arterial oxygen tension Hemoglobin dissociation conditions Local oxygen consumption Carrying capacity

Wound Perfusion and Oxygenation

Avoid vasoconstrictors Keep patient warm

Preoperative Management

Address modifiable risk factors

Optimize cardiopulmonary function

Treat vasoconstriction

Treat existing infection

Administer appropriate antibiotics

Glucose control

Intraoperative Management

Administer appropriate antibiotics and re-dose at indicated intervals

Maintain normothermia

Elevate PaO2

Gentle surgical technique

Keep wound moist

Antibiotic irrigation

Delay closure for contaminated wounds

Use appropriate suture and dressings

Judicious fluid administration

Postoperative Management

Pain control

Maintain adequate blood volume

Keep patient warm

Avoid vasoactive substances

Maintain PaO2

Maintain glycemic control

Summary

Anesthesiologists have opportunity to enhance wound healing during perioperative management