The aim of the present study is to assess effect of local wound infiltration in comparison with caudal block by bupivacaine 0.25% after inguinal herniotomy in pediatrics on: Wound infection and healing (primary outcome) and postoperative analgesia (secondary outcome).

THE EFFECT OF LOCAL WOUND INFILTERATION VERSUS CAUDAL BLOCK ON WOUND INFECTION AND HEALING AFTER INGUINAL HERNIOTOMY IN PAEDIATRICS

INTRODUCTION Since the introduction of cocaine in 1884, local anesthetics have been used as a mainstay of pain management. However, numerous studies over the past several decades have elucidated the supplemental role of local anesthetics as antimicrobial agents. In addition to their anesthetic properties, medications, such as: bupivacaine and lidocaine have been shown to exhibit bacteriostatic, bactericidal, fungistatic, and fungicidal properties against a wide spectrum of microorganisms.(1) Johnson et al.(2)made a comprehensive literature search using MEDLINE 1950-present for in vitro and in vivo studies pertaining to the antimicrobial activity of various local anaesthetics on a broad range of bacterial and fungal pathogens. Studies testing the effect on microbial growth inhibition of local anaesthetics alone and in combination with other agents, such as: preservatives and other medications, as well as the effect of conditions, such as: concentration and temperature were included for review. Evidence suggests that local anesthetics as a class possess inherent antimicrobial properties against a wide spectrum of human pathogens. Limited studies attribute the mechanism of action of antimicrobial activity of local anesthetics to a disruption of microbial cell membrane permeability, leading to leakage of cellular components and subsequent cell lysis.(2) Multiple local anesthetics at concentrations typically used in the clinical setting (e.g.:- bupivacaine 0.125%-0.75%; lidocaine 1%-3%) inhibit the growth of numerous bacteria and fungi under various conditions. Different local anesthetics showed various degrees of antimicrobial capacity; bupivacaine and lidocaine, for example, inhibit growth to a significantly greater extent than does ropivacaine.(2) In 1943 Lofgren (3) developed lidocaine. This was an amide and had a low risk of allergic reactions in comparison to ester local anesthetics. This was followed by mepivacaine (1957), prilocaine (1960), bupivacaine (1963), ropivacaine (1997) and levobupivacaine (2000).(3) Bupivacaine has been used in clinical practice for more than 40 years. It is remarkably stable in solution and is commercially available in 0.25% and 0.5% solutions (with and without epinephrine). Spinal heavy bupivacaine (0.5% bupivacaine + 6% glucose) is also manufactured. It is four times more potent than lidocaine. Therefore, 0.25% bupivacaine is equipotent with 1% lidocaine. Bupivacaine is particularly cardiotoxic and should never be used in Biers blocks. Bupivacaine binds tightly to tissues and thus has a long duration of action (up to 24 hours in some cases). Adding epinephrine will decrease its toxicity by delaying the drug absorption but, will have minimal effect on the duration of the block.(3)

The recommended maximum safe doses of bupivacaine are as follows:

BUPIVACAINE WITHOUT EPINEPHRINE ------- 2.0 mg/kg BUPIVACAINE WITH EPINEPHRINE ------- 2.5 mg/kg.(3) Caudal anesthesia is one of the most used-popular regional blocks in children. This technique is a useful adjunct during general anesthesia and for providing postoperative analgesia after infraumbilical operations. The quality and level of the caudal blockade is dependent on the dose, volume, and concentration of the injected drug.(4) Prophylactic analgesia with local anesthetics is an attractive concept, especially in pediatric practice, because the evaluation of pain can be very challenging in young children.(5) In contrast to opioids, local anesthetics can be administered safely, and in recent guidelines regional anaesthesia is accepted as the cornerstone of post-operative pain relief in the pediatric patients.(6) Although regional anaesthesia holds a good safety record overall, the global experience with pediatric regional anaesthesia is still quite low; even the most commonly performed procedure, caudal block, represents only 2.5% of all central neuroaxial blocks performed.(7,8) Determining the risk-benefit ratio is rather difficult for techniques that are relatively rarely performed. Wound infiltration can produce reliable analgesia for superficial skin surgery. Infiltration itself is extensively used by pediatricians, surgeons and emergency physicians for skin laceration repair or minor superficial surgery.(5) Several studies have compared the local anesthesia so far, including: ilio-inguinal and iliohypogastric nerve block plus subcutaneous injection by the surgeon against the caudal anesthesia.(9,10) But to our knowledge, there is still no study comparing the local wound infiltration by itself and caudal anesthesia for postoperative analgesia as regard their effect on wound infection and healing.

AIM OF THE WORK The aim of the present study is to assess effect of local wound infiltration in comparison with caudal block by bupivacaine 0.25% after inguinal herniotomy in pediatrics on: Wound infection and healing (primary outcome) and postoperative analgesia (secondary outcome).

PATIENTS After approval of ethical committee faculty of medicine, University of Alexandria, a prospective interventional concealed randomized clinical study which will include 50 children (calculated by department of community medicine) aged 2 months-1 year admitted to the Pediatrics Surgery Department of Alexandria University Hospitals for elective inguinal herniotomy surgery, and an informed written consent will be taken from the parents or the guardians.

All patients will be selected to be grade I or II according to American Society of Anesthesiologists (ASA) classification

The patients will be classified randomly into two groups using closed envelope technique, 25 patients each:

Group L: 25 patients will receive 1mg/kg bupivacaine 0.25% (diluted as 1ml bupivacaine + 1ml normal saline) by local infiltration in the wound before closure of the skin and subcutaneous.

Group C: 25 patients will receive caudal block with 1mg/kg bupivacaine 0.25%.

Exclusion criteria included:

• History of developmental delay or mental retardation.
• Diabetes mellitus type I.
• Known allergy or contraindication to any local anesthetics.
• Known congenital anomaly in the inguinal region.
• Any patient who will develop any infections postoperatively (respiratory infection, urinary infection) other than wound infection will be excluded.

METHODS

All patients will be subjected to the following:

A) Pre-operative visit:

Each patient will be visited the day before surgery for the following:

• Proper evaluation by history taking from parents, clinical examination and laboratory investigations.
• Explanation of the technique of postoperative analgesia to the parents and explain to them that the wound will be observed postoperatively for signs of inflammation and infection.

B) Pre-medication:

Paracetamol suppository 40mg/kg will be given half an hour before surgery.

C) Anaesthesia:

• All patients will be monitored for:

  • Heart rate (beats/minute) through continuous ECG tracing (lead II).
  • Non-invasive arterial blood pressure (mmHg).
  • Arterial oxygen saturation using pulse oximetry (%).

• Induction of general anaesthesia will be achieved with 8% sevoflurane in 100% oxygen.

• After securing an IV line with cannula, all patients will receive fentanyl 1mcg /kg.

• Laryngeal mask air way of proper size will be inserted under adequate depth of anaesthesia.

• Anaesthesia will be maintained with sevoflurane with concentration maintaining adequate depth of anaesthesia.

• At the end of procedure and before application of stitches, bupivacaine 0.25% will be infiltrated in the skin and subcutaneous layer in group L, and caudal block will be performed in group C; at the end of surgery inhalational anaesthetics will be stopped; laryngeal mask will be removed when patient is fully conscious.

• Postoperative pain will be assessed using the Faces Legs Activity Cry Consolability tool (FLACC, 0- 10) at 15 min, 1, and 3 h after operation.(11) Table (I): FLACC scale (Behavioral observation pain rating scale) Categories Scoring 0 1 2 Face No particular expression or smile; disinterested Occasional grimace or frown, withdrawn Frequent to constant frown, clenched jaw, quivering chin Legs No position or relaxed Uneasy, restless, tense Kicking, or legs drawn up Activity Lying quietly, normal position, moves easily Squirming, shifting back and forth, tense Arched, rigid, or jerking Cry No crying (awake or asleep) Moans or whimpers, occasional complaint Crying steadily, screams or sobs, frequent complaints Consolability Content, relaxed Reassured by occasional touching, hugging, or talking to. Distractible Difficult to console or comfort Each of the five categories (F) face; (L) legs; (A) Activity; (C) Cry; (C) Consolability is scored from 0-2, which results in a total score between 0 and 10.

• A child with a score of more than 4 on FLACC will receive intravenous acetaminophen 15mg/kg.

• The incision will then be monitored for signs of infection (Redness, Hotness, Swelling, Discharge, or Separation/Breakdown of deep tissues).

• Data regarding the incision will be obtained on day 7 postoperative or with sutures removal or any time before this if he/she develops any of wound inflammation signs earlier.

D) Measurements:

• Postoperative vital signs/hour for 4 hours.
• Faces Legs Activity Cry Consolability tool (FLACC, 0- 10) at 15 min, 1, and 3 h after operation.(11)
• Timing of first postoperative complaint of pain, first requirement for postoperative analgesia and total consumption of analgesia
• Laboratory measurements: white blood cells count at day 0 and day 7 postoperative.
• Culture: with first dressing change at day 7 postoperative from the wounds with discharge (suspected infected wounds).
• Wound infection and healing scale: using Southampton scoring system,(12) which classifies wounds according to healing into 6 grades (0, I, II, III, IV, V).

Table (II): Southampton wound scoring system Southampton wound scoring system Grade Appearance 0 Normal healing I Normal healing with bruising or mild erythema A Some bruising B Considerable bruising C Mild erythema II Erythema +other signs of inflammation A At one point B Around the sutures C Along the wound D Around the wound III Clear or heamoserous discharge A At one pint only (<2cm) B Along the wound (>2cm) C Large volume D Prolonged (3days) Major complication IV pus A At one point only (<2cm) B Along the wound (>2cm) V: deep or severe wound infection with or without tissue break down; hematoma requiring aspiration.

ETHICS OF RESEARCH

Research on human or human products:

Prospective study: Informed consent will be taken from patients. In case of incompetent patients the informed consent will be taken from the guardians.

Inclusion Criteria:

• Children aged 2 months-1 year
• Admitted for elective inguinal herniotomy surgery.

Exclusion Criteria:

• History of developmental delay or mental retardation.
• Diabetes mellitus type I.
• Known allergy or contraindication to any local anesthetics.
• Known congenital anomaly in the inguinal region.
• Any patient who will develop any infections postoperatively (respiratory infection, urinary infection) other than wound infection will be excluded.

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