– Results range from 0 to 100 whereby 0 = complete suppression of activity (isoelectric EEG) and 100 = full awareness
– Help in determining level of patient’s awareness during surgery, lowers the consumption of anesthetics during surgery, helps in earlier awakening and faster recovery from anesthesia
– Also helps in titration of levels of sedative medications
– BIS < 40 for > 5 minutes is an independent predictor of increased perioperative morbidity due to stroke and myocardial infarction in high-risk patients.
Q57. Enumerate the causes of Postoperative fever. Discuss its management.
Ans. Temperature >38.3°C in postoperative period Causes
6 W s Cause Post operative Day
Wind Atelectasis
Pneumonia 1
2
Water Urinary tract infection
Thrombophlebitis 2
2
Wound Wound infection
Anastomotic leak 3,4
5-8
Walk Deep vein thrombosis
Pulmonary embolism 5-8
5-8 Wonder drugs Anesthetic drugs
Antibiotics Blood products
Immediate/intraoperative Anytime
Anytime
Waste products GIT Anyday after 3rd day
Immediate
Fever that occurs in operation theater or in immediate postoperative period Causes
y Malignant hyperthermia
y Medication (antibiotics, blood transfusion)
y Necrotizing infections (Clostridium, group A Streptococcus) Acute fever
Fever in the first week after operation Causes
y Atelectasis, pneumonia
y Urinary tract infection (catheter >2 days increases the risk) y IV line infection
y Wound infection, anastomotic leak
y Pulmonary embolism, deep vein thrombosis
y Myocardial infarction, pancreatitis, aspiration pneumonia.
Subacute fever ( > 1 week) y UTI, IV line
y SSI
y Antibiotic induced fever
y Pseudomembranous enterocolitis y Febrile drug reactions.
Management
y Appropriate resuscitative measures and care of patient’s airway, breathing and circulation y Cultures from all existing lines, sputum, urine, blood and wound in case of SSI
y Remove/replace peripheral lines, nontunneled lines and catheter y Chest X-ray, ultrasound for wound and intra-abdominal collections y Evaluation of drug list
y Lower limb doppler and chest CT, D-dimer for suspected PE/DVT y Open/debride/drain wound in case of SSI
y Start broad spectrum antibiotics in case of pneumonia, bacteremia, UTI, sepsis and continue for 10 to 14 days except in septic thrombosis or endocarditis where antibiotics need to be continued for 4–6 weeks.
Catheter salvage therapy
y Indicated in patients with tunnelled catheters that are too risky to remove or replace or in patients with coagulase negative staphylococci with no evidence of metastatic disease/severe sepsis/persistent bacteremia/tunnel infection
y Achieved by antibiotic lock therapy in which, the catheter is filled with antibiotic solution for few hours every day.
Q58. Discuss the role of prophylactic antibiotics in surgery.
Ans.
Definitions
y Infection: The invasion of the body by pathogenic microorganisms that reproduce and multiply causing disease by local cellular injury, secretion of a toxin or antigen-antibody reaction in the host
y Colonization: The presence of bacteria on a body surface (like on the skin, mouth, intestines or airway) without causing disease in the person
y Prophylactic antibiotic treatment: The use of antibiotics before, during or after a diagnostic, therapeutic or surgical procedure to prevent infectious complications y Therapeutic antibiotic treatment: The use of substances that reduce the growth
or reproduction of bacteria, including eradication therapy (Antimicrobial therapy prescribed to clear infection by an organism or to clear an organism that is colonising a patient but is not causing infection)
y Primary prophylaxis refers to the prevention of an initial infection
y Secondary prophylaxis refers to the prevention of recurrence or reactivation of a pre- existing infection
y Eradication refers to the elimination of a colonized organism to prevent the development of an infection.
Need of prophylaxis
y Prevent surgical site infection (SSI)
y Prevent SSI-related morbidity and mortality
y Reduce the duration of hospital stay and cost of health care At the same time care should be taken so that there is
y Minimal effect of antibiotics on the patient’s normal bacterial flora y Minimal adverse effects of the used drugs
y Minimal change to the patient’s host defences Risks
y Unknown allergy to drugs and anaphylaxis (mainly penicillin and cephalosporin group) y Antibiotic associated diarrhea (even single dose can cause it)
y Antibiotic resistance
y Multiresistance carriage (mainly MRSA and VRE).
Choice of Antibiotics
y Must cover the expected pathogens y Local resistance patterns
y Narrow spectrum, less expensive
y Carriers of MRSA (anterior nasal swab cultures) should have a course of eradication therapy prior to high risk surgery (orthopaedic implant, heart valve, vascular graft or shunt or CABG).
Dosage and timing of administration
y Serum and tissue concentrations exceeding the minimum inhibitory concentration (MIC) – At the time of incision
– For the duration of the procedure.
y Intravenous route
y Should be given ≤60 minutes before the skin is incised
y For fluoroquinolones and vancomycin, the administration should begin within 120 minutes before surgical incision
y A single standard therapeutic dose of antibiotic is enough y Arthroplasty—24 hours
y Cardiothoracic surgery—48 hours.
Need of re-administration
y The redosing interval should be measured from the time of administration of the preoperative dose
y Duration of surgery longer than twice the half-lives of the drug y Major intraoperative blood loss
– In adults (>1,500 mL) – In children (25 mL/kg)
Additional dosage of prophylactic antibiotics should be considered after fluid replacement.
Antimicrobial prophylaxis for the prevention of infective endocarditis y Evidence is weak and inconclusive
y The 2007 AHA guideline. Similar indications by the British Society for Antimicrobial Chemotherapy
y The highest risk conditions (Prosthetic heart valves, a prior history of IE, unrepaired cyanotic congenital heart disease).
y The following are the highest risk procedures (All dental procedures, procedures in patients with ongoing GI or GU tract infection, on infected skin, skin structure, or musculoskeletal tissue and cardiac surgery).
y The antibiotics should be procedure and patient specific y Antibiotic of choice—oral amoxycillin
y Penicillin allergy—ceftriaxone, cefazolin, vancomycin, clindamycin Important considerations
y Agents that are FDA-approved for use in surgical antimicrobial prophylaxis include cefazolin, cefuroxime, cefoxitin, cefotetan, ertapenem, intranasal mupirocin and vancomycin
y The safety and efficacy of topical antimicrobials have not been clearly established.
Recommendations in surgery
Antibiotic prophylaxis is recommended in clean surgery with prosthesis, all clean and contaminated surgeries and in all dirty surgeries alongwith therapeutic antibiotic therapy.
Q59. Discuss probiotics, prebiotics and synbiotics.
Ans.
Definitions
y Probiotics: Live microorganisms which, when administered in adequate amounts, confer a health benefit on the host
y Prebiotics: Nondigestible substances that provide a beneficial physiological effect for the host by selectively stimulating the favorable growth or activity of a limited number of indigenous bacteria
y Synbiotics: Products that contain both probiotics and prebiotics
y Species of Lactobacillus and Bifidobacterium are most commonly used as probiotics but the yeast S. cerevisiae and some E. coli and Bacillus species are also used as probiotics.
Lactic acid bacteria, including Lactobacillus species, which have been used for preservation of food by fermentation for thousands of years can serve a dual function by acting as agents for food fermentation and in addition, potentially imparting health benefits.
Benefits of using probiotics/prebiotics Probiotics
y Immunologic benefits
– Activate local macrophages to increase antigen presentation to B lymphocytes and increase secretory immunoglobulin A (IgA) production both locally and systemically – Modulate cytokine profiles
– Induce hyporesponsiveness to food antigens.
y Nonimmunologic benefits
– Digest food and compete for nutrients with pathogens
– Alter local pH to create an unfavorable local environment for pathogens – Produce bacteriocins to inhibit pathogens
– Scavenge superoxide radicals
– Stimulate epithelial mucin production – Enhance intestinal barrier function – Compete for adhesion with pathogens – Modify pathogen-derived toxins.
Prebiotics
y Metabolic effects: Production of short-chain fatty acids, fat metabolism, absorption of ions (Ca, Fe, Mg)
y Enhancing host immunity (IgA production, cytokine modulation, etc.).
Clinical applications Colon cancer
y Studies suggest that a synbiotic preparation can decrease the expression of biomarkers for colorectal cancer.
Diarrhea
y Treatment of acute diarrhea: Different probiotic strains such as L. reuteri, L. rhamnosus GG, L. casei, and S. cerevisiae (boulardii) are useful in reducing the severity and duration of acute infectious diarrhea in children. The oral administration of probiotics shortens the duration of acute diarrheal illness in children by approximately 1 day.
y Antibiotic-associated diarrhea: In antibiotic-associated diarrhea, there is strong evidence of efficacy for S. boulardii or L. rhamnosus GG in adults or children who are receiving antibiotic therapy.
y Radiation-induced diarrhea: L. casei, L. plantarum, L. acidophilus, L. delbrueckii, B.
longum, B. breve, B. infantis, and S. thermophilus are effective in the treatment of radiation- induced diarrhea.
Hepatic encephalopathy
y Prebiotics such as lactulose are commonly used for the prevention and treatment of this complication of cirrhosis. Minimal hepatic encephalopathy was reversed in 50% of patients treated with a synbiotic preparation (four probiotic strains and four fermentable fibers including inulin and resistant starch) for 30 days.
Pouchitis
y There is good evidence for the usefulness of probiotics in preventing an initial attack of pouchitis and in preventing further relapse of pouchitis after the induction of remission with antibiotics. Probiotics can be recommended to patients with pouchitis of mild activity or as maintenance therapy for those in remission.
Ulcerative colitis
y The probiotic E. coli Nissle strain may be an equivalent to mesalazine in maintaining remission of ulcerative colitis. There is an in adequate research evidence to be certain that other probiotic preparations are effective in ulcerative colitis.
Crohn’s disease
y Studies of probiotics in Crohn’s disease have been disappointing and a recent Cochrane systematic review concluded that there is no evidence to suggest that probiotics are beneficial for maintenance of remission in Crohn’s disease.
Irritable bowel syndrome (IBS)
y Several studies have demonstrated significant therapeutic gains with probiotics in comparison with placebo. A reduction in abdominal bloating and flatulence as a result of probiotic treatments is a consistent finding in published studies. Some strains may ameliorate pain and provide global relief in addition. Lactobacillus reuteri may improve colicky symptoms within one week of treatment as shown in a recent trial with 90 breast- fed babies with infantile colic. In summary, there is literature suggesting that certain probiotics may improve the principal symptoms in persons with IBS.
Lactose malabsorption
y S. thermophilus and L. delbrueckii subsp bulgaricus improve lactose digestion and reduce symptoms related to lactose intolerance.
Necrotizing enterocolitis
y Clinical trials have shown that probiotic supplementation reduces the risk of necrotizing enterocolitis in preterm neonates of less than 33 weeks’ gestation. A systematic review of randomized controlled trials also indicated a reduced risk of death in probiotic treated groups.
In summary, there is strong support for the use of certain probiotic strains in preterm infants.
Q60. What is surgical site infection? Discuss the methods to reduce surgical site infection.
Enumerate the factors responsible for surgical site infection.
Ans. Definition
Nosocomial Infection
y An infection acquired in hospital by a patient who was admitted for a reason other than that infection
y An infection occurring in a patient in a hospital or other health care facility in whom the infection was not present or incubating at the time of admission. This includes infections acquired in the hospital but appearing after discharge and also occupational infections among staff of the facility.
Infections occurring for more than 48 hours after admission are usually considered nosocomial Amongst surgical patients, SSI are the most common nosocomial infections (38%).
Classes of SSI
CDC criteria for defining a surgical site infection
y Superficial incisional SSI: Infection occurs within 30 days after the operation and infection involves only skin of subcutaneous tissue of the incision and at least one of the following:
– Purulent drainage with or without laboratory confirmation from the superficial incision
– Organisms isolated from an aseptically obtained culture of fluid or tissue from the superficial incision
– At least one of the following signs or symptoms of infection:
- Pain or tenderness - Localised swelling - Redness
- Heat
- And superficial incision deliberately opened by a surgeon, unless incision is culture negative
– Diagnosis of superficial incisional SSI by the surgeon or attending physician.
y Deep incisional SSI: Infection occurs within 30 days after the operation if no implant is left in place or within one year if implant is in place and the infection appears to be related to the operation and infection involves deep soft tissues (e.g. fascial and muscle layers) of the incision and at least one of the following:
– Purulent drainage from the deep incision but not from the organ/space component of the surgical site
– A deep incision spontaneously dehisces or is deliberately opened by a surgeon when the patient has at least one of the following signs or symptoms:
- Fever (>38°C) - Localized pain
- Tenderness unless site is culture-negative
– An abscess or other evidence of infection involving the deep incision is found on direct examination, during re-operation or by histopathological or radiological examination – Diagnosis of deep incisional SSI by a surgeon or attending physician.
y Organ/space SSI: Infection occurs within 30 days after the operation if no implant is left in place or within one year if implant is in place and the infection appears to be related to the operation and infection involves any part of the anatomy (e.g. organs or spaces), other than the incision, which was opened or manipulated during an operation and at least one of the following:
– Purulent discharge from a drain that is placed through a stab wound into the organ/
space
– Organisms isolated from an aseptically obtained culture of fluid or tissue in the organ/space
– An abscess or other evidence of infection involving the organ/space that is found on direct examination, during re-operation, or by histopathologic or radiological examination
– Diagnosis of an organ/space SSI by a surgeon or attending physician.
Strategies to prevent SSI Objectives
y Reduce the inoculum of bacteria at the surgical site y Surgical site preparation
y Antibiotic prophylaxis strategies
y Optimize the microenvironment of the surgical site y Enhance the physiology of the host (host defenses)
In relation to risk factors, classified as:
y Patient-related (intrinsic) y Preoperative
y Operative
Patient-related factors
y Diabetes—recommendation y Preoperative
y Control serum blood glucose—reduce HbA1C levels to <7% before surgery if possible y Postoperative (cardiac surgery patients only)
y Maintain the postoperative blood glucose level at less than 200 mg/dL y Other patient related factors include:
– Smoking, anemia, malnutrition – Hypoalbuminemia, jaundice – Obesity, hyperlipidemia – Ascites, PVD
– Immunosupression.
Procedure-related risk factors
y Hair removal technique (clipping> on table shaving > previous night shaving) y Preoperative infections control and bath
y Surgical scrub y Skin preparation
y Antimicrobial prophylaxis
y Surgeon skill/technique/instruments y Asepsis
y Operative time (should be within 1.5 times the normal) y Operating room characteristics/OT sterility.
Surgeon skill and technique
Excellent surgical technique reduces the risk of SSI Includes
y Gentle traction and handling of tissues y Effective hemostasis
y Removal of devitalized tissues y Obliteration of dead spaces
y Irrigation of tissues with saline during long procedures y Use of fine, nonabsorbed monofilament suture material y Wound closure without tension.
Examples of multimodal approach(es) to reduce SSI
y Timely antibiotic prophylaxis, strict glycemia control, no shaving SSI 1.5% vs. 3.5% in controls
y 100k lives campaign
(antibiotic prophylaxis, glycemia control, normothermia)
SSI from 2.3% to 1.7% (-27%)
y Risk stratification of patients according to National nosocomial infection surveillance system (NNISS) include wound type (contaminated/dirty), ASA grade (3,4,5) and duration of operation (>75th percentile of normal) to give risk of SSI in a particular patient.
y Bowel preparation lowers the patient’s risk of infection from that of a contaminated case (25%) to a clean contaminated case (5%).