PRE-OPERATIVE AND INTRA-OPERATIVE CARE OF THE ANESTHESIA PATIENT group 8-2.pptx

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1. PRE-OPERATIVE AND INTRA-OPERATIVE CARE OF THE ANESTHESIA PATIENT GROUP 8 Mary Muongoya Nyambura - TM226-3520/2015 Benjamin Masereti Nyariki- HSM201-0137/2016 Ngugi Margaret Wanjiru - TM226-4512/2015 Nelson Kiplangat - TM226-4468/2015

2. OBJECTIVES CONTEXT FACTORS INFLUENCING PERI-OP CARE DEFINITIONS TIMING METHODOLOGY GOALS/AIMS HISTORY,PHYSICAL EXAM, RELEVANT LABS

3. CONTEXT Peri-op care Definition Components

4. FACTORS INFLUENCING PERI-OP CARE Nature (elective vs emergency) Disposition (day case vs in-patient) Procedure type (minor vs major surgery)

5. DEFINITIONS PRE-OP ANESTHESIA EVALUATION Assessment preceding delivery of anesthesia care MORBIDITY The condition of suffering from a disease or medical condition

6. TIMING & METHODOLOGY TIMING IDEALLY- before and immediate pre-op On the day of the procedure HOW TO COLLECT INFO Patient interview Records Physical exam Labs/imaging as appropriate

7. GOALS Risk assessment & fitness determination ( Hx,PE,Ix ) Optimization of conditions Medication adjustments Patient education, preparation & setting expectations Obtain informed consent (5 components) Formulate anesthetic plan

8. OUTCOME Decrease day of surgery delays /cancellations Decrease peri -op morbidity and mortality Decrease cost (patient and healthcare system) Decrease total length of in-hospital stay Prevent litigation

9. RISK & FITTNESS-HISTORY Present illness & Mx and planned procedure What has been done since admission PAST MEDICAL HISTORY CVS-HTN,CAD,VHD,CCF,CHD, arrythmias & implantable electronic devices RESP-Asthma, COPD, Pul HTN, OSA, laryngomalacia CNS-convulsive disorder, TBI, SOLs GIT-GERD, IO, Tumors, Gastritis Renal-AKI,CKD

10. HISTORY- Ctd Endocrine-DM, Thyrotoxicosis Hemato -oncologic-anemia, malignancy Nutrition and hydration status Weight Height BMI ANESTHETIC SUMMARY

11. HISTORY- Ctd C- Confirm the diagnosis and duration E- Evaluate as needed (P/E, Labs, Imaging) S- Stage or classify T- Target organ damage M- Medications currently used Names Compliance Adverse effects O- optimum? Well controlled? D- Defer?

12. HISTORY example-CVS Why the concern? The body’s response to surgical stress C irculatory effects of: Anesthetic agents Endotracheal intubation Positive pressure ventilation Blood loss Fluid shifts and alterations in the body temperature

13. MEDICATIONS & ALLERGIES Anti-coagulants MAO-Is Corticosteroids Contraceptives ACE-Is and ARBs Antobiotics Herbal medicines

14. HABITS AND EXERCISE TOLERANCE Alcohol use Tobacco Illicit drugs Exercise tolerance (metabolic equivalents) Diet

15. PERSONAL SURGICAL AND ANESTHETIC HX Surgeries Indication Where When Anesthesia used Type Drugs used Adverse reactions (encounter summary)

16. FAMILY HISTORY Of chronic illnesses HTN DM Asthma Of anesthesia and any ADRs Malignant hyperthermia

17. RISK STRATIFICATION TOOLS The information gathered from patients’ history and physical exam can be used to predict their anesthetic and surgical risk Various risk stratification tools exist: ASA physical status ACS NSQIP surgical risk tool

18. AMERICAN SOCIETY OF ANAESTHESIOLOGISTS ( ASA ) PHYSICAL STATUS CLASSIFICATION ASA 1 - A normal healthy patient e.g. non smoking, no or minimal alcohol use ASA 2 - A patient with mild systemic disease e.g. well controlled DM or HTN, current smoker or social alcohol drinker ASA 3 - A patient with severe systemic disease e.g. poorly controlled HTN OR DM, active hepatitis, alcohol abuse ASA 4 - A patient with severe systemic disease that is a constant threat to life e.g. DIC, ESRD not undergoing regular dialysis ASA 5 - A moribund patient who is not expected to survive without the operation e.g. ruptured thoracic or abdominal aneurysm ASA 6 - A declared brain dead patient whose organs are being removed for donor purposes

19. PHYSICAL EXAM At a minimum: Airway assessment CVS exam Respiratory exam BMI Vitals

20. AIRWAY ASSESSMENT What is the airway? What are the components if the airway? Why assess the airway? What is a difficult airway? What is difficult ventilation? Components of airway assessment

21. AIRWAY ASSESSMENT- Ctd Passage through which air travels during respiration COMPONENTS Nasal cavity Oral cavity Pharynx Larynx Trachea and large bronchi

22. 3.Why assess? High incidence of anesthesia related respiratory events Preparation for difficult airway One of the fundamental responsibilities of the anesthesiologist is to mitigate the adverse effects of anesthesia on the respiratory system by maintaining airway patency and ensuring adequate ventilation and oxygenation

23. DIFFICULT AIRWAY & VENTILATION Difficult airway Conventionally trained anesthetist experiences difficulty with mask ventilation, tracheal intubation or both. (> 3 attempts, > 10 mins, failure of optimal best attempt) Difficult ventilation Inability of the trained anesthetist to maintain the oxygen saturation >90% using a face mask for ventilation and 100% inspired oxygen provided that the pre-ventilation oxygen saturation level was within normal range

24. AIRWAY ASSESSMENT Airway assessment should begin with a directed patient history whenever possible. One of the most predictive factors for difficult intubation is a history of previous difficulty with intubation.

25. AIRWAY ASSESSMENT- Ctd Nostril patency Oral cavity Dentition : length of upper incisors alignment/relationship of upper incisors to lower condition of teeth Dentures Ability to protrude mandibular (lower) incisors beyond upper incisors Inter-incisor distance (or inter-gum if edentulous) Tongue size

26. Upper lip bite test

27. AIRWAY ASSESSMENT Ctd Atlanto -occipital movements TMJ movements Thyromental distance Hyomental distance Mallampati score

28. When the neck is flexed on the chest (25-35°) and the A-O joint is well extended, the pharyngeal and laryngeal axes are brought more closely into a straight line-sniff position. When the atlanto -occipital joint cannot be extended, attempts to do so cause the convexity of the cervical spine to bulge anteriorly, pushing the larynx more anterior.

29. THYROMENTAL DISTANCE Mandibular space anterior to the larynx determines how easily the laryngeal axis will fall in line with the pharyngeal axis when the A-O joint is extended. If thyromental distance is very short, the laryngeal axis will make a more acute angle with the pharyngeal axis and it will be more difficult for atlanto -occipital extension to bring these 2 axes into line

30. HYOMENTAL DISTANCE

31. MALLAMPATI SCORE

32. MALLAMPATI SCORE If the base of the tongue is disproportionately large relative to the capacity of the oropharynx, it would obscure the view of the faucial pillars, posterior part of the uvula and eventually the soft palate in that order. It would also render the angle to the trachea more acute and obscure the larynx.

33. GLOTTIC VIEW/VOCAL CORDS-CORMACK-LEHANE

34. PREDICTORS OF A DIFFICULT MASK VENTILATION & INTUBATION Mallampati 3-4 Obesity Age >50 Extensive beard History of snoring Severely limited jaw protrusion Edentulous patients Mask seal difficulty due to: facial dysmorphism , receding mandible

35. LEMON ASSESSMENT LOOK (Visual inspection) EVALUATE-3-3-2 MALLAMPATI OBSTRUCTION NECK MOVEMENT

36. LOOK Morbidly obese Facial/neck trauma Obvious facial deformities N eoplasms involving the face or neck facial burns A large goiter Receding mandible Beard/facial hair Short,fat neck Large incisors, broken teeth, dentures

37. COMORBIDITIES-many obese patients have a high prevalence of conditions such as HTN, IHD, DM, hypercholesterolaemia and gastric reflux Airway-obese patients have 2X the risk of major airway problems compared to non-obese pts IV access Regional? Positioning

38. RELEVANT LAB INVESTIGATIONS Blanket pre-op investigations waste resources and time!!! Investigate only when indicated from hx /PE or surgical plan If it doesn’t change patient management- don’t do it

39. The type and number of investigations depends on Age General health/co-morbidities of the patient Medications Presenting condition Urgency of surgery Nature of surgery planned Facilities available for testing

40. Full blood count Measure when The history or examination indicates anemia The surgery is expected to cause significant blood loss Measure in patients with Jaundice Malignancy Infection HIV Significant blood loss Cardiac/Renal/Respiratory diseases

41. GXM Group According to hospital guidelines for both elective and emergency surgery Significant or continuing blood loss Cross match When blood is required immediately if blood loss >30% circulating blood volume (>1.5 L in adults) If blood loss >50% circulating blood volume (2.5 L in adult) Use O negative blood until crossmatched blood becomes available

42. COAGULATION SCREEN Measure when the patient Has hepatic disease Is on warfarin or anticoagulants Has eclampsia or pre-eclampsia (particularly if platelet count <100 or dropping acutely) History of inappropriate excessive bleeding Family history of bleeding disorder Severe sepsis Major hemorrhage

43. BLOOD GLUCOSE Measure if patient has: DM Glycosuria Steroid treatment Altered conscious level

44. UECs Measure for all major surgeries Measure in patients on diuretics or cardiovascular drugs Also in patients with; Infections DM Dehydration HTN Poor urine output Severe vomiting and diarrhoea

45. LFTs Measure in patients with; Cardiac/hepatic disease Biliary disease Infection Alcohol abuse Jaundice

46. CXR Not routinely ordered Usually limited to patients listed for major surgery with substantial cardiac or respiratory disease, heavy smoking or exposure to TB

47. ECG Consider when patient scheduled for major surgery has Cardiovascular risk factor or history of cardiovascular disease e.g. HTN, smoking, obesity, significant family history Signs of heart failure Suspecting arrythmia from clinical examination Atypical abdominal pain or cardiac sounding chest pain

48. ECHOCARDIOGRAPHY Not routinely done Consider resting echocardiography if the patient has; A heart murmur and any cardiac symptom (e.g. breathlessness, pre-syncope, syncope or chest pain) Signs and symptoms of heart failure

49. PULMONARY FUNCTION TESTS To assess the reversibility of obstructive airway diseases Useful to qualify severity of ventilatory dysfunction For patients with dyspnoea on mild exertion, COPD or asthma. Measure peak expiratory flow rate (PEFR), forced expiratory volume in 1 s (FEV1) and FVC.

50. Other tests Sickle-cell screen : If has a family history of sickle-cell disease or where ethnicity increases the risk of sickle-cell disease. If positive, electrophoresis will be required for definitive diagnosis. Pregnancy test; If uncertain pregnancy history, history suggestive of current pregnancy

51. PATIENT PREPARATION Premedication-6As Fasting-2,4,6,8 Education-BRAIN

52. Part 2 Informed Consent Anaesthetic Plan Optimization

53. INFORMED CONSENT Consent- voluntary agreement, compliance or permission for a specified act or purpose Ethical principles upheld:patient autonomy, beneficience The goal: maximize the ability of the patient to make substantially autonomous informed decisions

54. Types of consent Implied consent the person’s consent is inferred from his or her actions (or inactions ) Expressed consent It is clearly and unmistakably stated rather than implied. It can be written, verbal or non verbal consent. Verbal consent It may be simply an extension of implied consent where the patient may agree or disagree verbally. It may also be a very thorough process in which the anaesthetist has explained specific risks and benefits of a proposed procedure in great detail and, following some deliberation, the patient agrees verbally.

55. Written consent - involves the patient agreeing to the proposed procedure and confirming this in writing. This is most commonly facilitated by a pre-printed consent form for operative procedures, but there may be occasions on which the medical notes are used for this purpose. It is important to understand that the written form simply documents that the patient has given their consent. It does not necessarily provide any information about the quality of that consent. Substituted consent - Allows a decision maker to establish a decision for an incompetent person

56. Elements of Informed consent Competence and decision making capacity Disclosure of information-Patient is informed adequately of the relevant information. Understanding of disclosed information. Voluntary consent. Documentation- the informed consent should not be signed until the patients’ have been answered to their satisfaction.

57. WHAT TO DISCLOSE TO THE PATIENT B - Benefits R -Risks A -Alternatives I -Indications N -Nature of procedure including recovery process

58. THE ANESTHETIC PLAN What is an anesthetic plan? It is a blueprint for anesthesia care

59. OBJECTIVES OF AN ANESTHESIA PLAN Identify indications for the anesthesia/sedation Recognize factors that will impact the delivery of anesthesia care Decide on anesthesia technique to use for the given procedure The implications of the anesthetic and its subsequent management Plan for expected and unexpected perioperative events

60. FACTORS TO CONSIDER WHEN PLANNING FOR ANESTHESIA

61. FACTORS TO CONSIDER WHEN PLANNING FOR ANESTHESIA PATIENT FACTORS Understand the medical and physiological needs of the patient 2. SURGICAL FACTORS Understand the requirements of the surgery and the surgeon Understand the anesthetic requirements Understand the physiological impact of the surgery

62. Factors Ctd 3. ENVIRONMENTAL FACTORS Understand the environment in which the procedure will be done Adequate equipment and supplies Adequate staff Appropriately trained assistance Safe environment in which pt can be managed intra and post op 4. OTHER FACTORS Anticipate problems that may arise

63. ELEMENTS OF AN ANESTHETIC PLAN Patient summary relevant to anesthesia and surgery Pre-op planning Pre-medication Anesthesia technique Airway management Maintenance (technique , intra-op drugs, monitoring) Emergence Post-op

64. Patient summary relevant to anesthesia and surgery Covered in pre-op assessment History Physical exam Labs

65. PRE-MEDICATION Covered in pre-op care!

66. ANESTHESIA TECHNIQUE BASED ON: Pre-op exam and evaluation Type and extent of the surgical procedure The ability to perform various anesthetic techniques based on experience and availability of equipment and drugs Patient preference

67. Airway management Covered ahead Based on physical exam and available resources

68. POST-OP Where to physically care for patients Pain Fluids , Electrolytes and Nutrition Diabetes Management Mobilisation , Physiotherapy, DVT Prophylaxis Nausea and Vomiting Post-Op Investigations Returning to baseline function, medications etc ….

69. OPTIMIZATION OF PATIENTS Preoperative evaluation and care are essential for optimal surgical outcomes and can provide health benefits long after surgical intervention

70. Patient Optimization is designed to prepare for different surgeries: An elective procedure An emergency surgery Those with chronic diseases Patient to experience the best possible post-surgical outcomes.

71. Elective surgery E.g. hernia, colorectal malignancies, breast malignancy Patients attend Pre-op clinic, where they are evaluated History Physical examination Informed consent Marking site/side of operation Ordering all pre-op lab tests Provides all useful information about each patient’s evidence based workup

72. Emergency Surgery High risk. Emergent major surgery, aortic and other major valves, Intermediate. Endovascular or AAA repair, Carotid endarterectomy Low risk. Endoscopic procedures, cataract surgery Routine examination should be altered to fit circumstances A.B.C.D.E Secondary (head to toe) Carry out Preoperative investigations

73. Patients with Chronic diseases Prior to consideration of surgical intervention, it is necessary to prepare patient as fully as possible so as to optimize him according to his comorbidities This includes assessing risk factors specific to the chronic disease Doing a system wise approach to preoperative optimization Preoperative assessment several weeks prior to planned surgery will allow the opportunity to optimize the patient’s medical comorbidities plan for anaesthesia arrange the appropriate level of postoperative care.

74. Optimizing patients for surgery requires careful attention to their nutritional status. Exercise capacity has long been recognized as a good predictor of postoperative morbidity and mortality.

75. LIFESTYLE MODIFICATIONS Smoking cessation 6 to 8 weeks prior to surgery reduce the overall complications Reduction/cessation of alcohol consumption Preoperative alcohol consumption is associated with an increased risk of general postoperative morbidity and mortality, infection, wound complications, pulmonary complications, prolonged stay in the hospital, and admission to the intensive care unit.

76. Cardiovascular system – NYHA, Revised Cardiac Risk Index Pulmonary system-bronchodilator therapy, antibiotic therapy for pre existing infection Renal system – assessment of renal function, manipulation of hyperkalemia, avoid nephrotoxic drugs Hepatobiliary system -lab investigations, Child Pugh Scoring System Endocrine system – Glycemic control, euthyroid state achieved Hematologic system – preoperative reversal of anticoagulant effect, warfarin with held, correct anemia

77. INTRA-OP CARE

78. Part 3 Basic sequence of events during surgical anaesthesia . Options for airway management Oxygen

79. INTRA-OP CARE OF THE ANESTHETIZED PATIENT What is anesthesia? What are the components of balanced anesthesia? How do we prepare for anesthesia? What are the phases of anesthesia?

80. DEFINITION Anesthesia is a pharmacologically induced reversible state of amnesia, analgesia, loss of responsiveness, loss of skeletal muscle reflexes and decreased stress response

81. BALANCED ANESTHESIA Analgesia Amnesia Unconsciousness Muscle relaxation and paralysis Abolition of autonomic reflexes

82. Preparation in THEATRE Check anesthetic equipment – Machines & Monitors Check tracheal intubation trolley Check emergency drugs Draw drugs for anesthesia Attach monitors Record baseline reading IV access Pre-oxygenation

83. PHASES Induction Maintenance Reversal

84. Induction of anaesthesia DEF: transition from an awake to an anaesthetized state through the administration of a drug or combination of drugs at the beginning of an anaesthetic procedure Inhalational Intravenous agents Muscle relaxants Pts at risk of aspiration need rapid sequence induction

85. MAINTENANCE The duration of action of IV induction agents is generally 5 to 10 minutes, after which time spontaneous recovery of consciousness will occur. In order to prolong anaesthesia for the required duration (usually the duration of surgery), anaesthesia must be maintained

86. Maintenance of anaesthesia I nhaled agents( des,iso &sevoflurane,N2O) TIVA opiods ( fentanyl,su,remi&alfentanil , NDMR( rocuronium,cis-atracurium ) Hypnotiagents positioning:careful positioning is important The anaesthesiologist should be vigilant of problems encountered in this phase such as awareness

87. Maintenance cont’d Sitting pos;ass with risk of venous air embolism Prone;aiway obstructed or dislodged Prone trendelburg & lithotomy;upward displacement of diaphragm Nerve injury from compression on pressure points esp ulnar n.,brachial plexus injury,

88. Hypothermia;has deleterious effects on cns rs etc & inc,recovery time from effects of muscle relaxants Heat lost via conduction,convection,evaporation,radiation Loss minimized by keeping OR temp as high astolerable >21C ;gas humidifiers or use of low gas flow; warm fluids given; pt may need to be sedated,paralysed&mech ventilated post-op till adequate temp is restored

89. AIRWAY MANAGEMENT

90. Airway management techniques Mask airway(airway supported manually or with oral airway ) Supraglottic airway Laryngeal mask airway E ndotracheal intubation(nasal or oral)

91. Factors determining choice airway assessment Risk of regurgitation or aspiration Need for positive pressure ventilation Surg.factors ( location,duration,pt pos .,degree of muscle relaxation required

92. BVM

93. NON-REBREATHER

94. SUPRA-GLOTTIC AIRWAY DEVICES SADs are used with both spontaneously and ventilated patients during anesthesia Also employed as conduits to aid ETT intubation Additionally, occlude the esophagus with varying degrees of effectiveness, reducing gas distension of the stomach C onsist of a tube connected to a respiratory circuit or breathing bag, which is attached to a hypopharyngeal device that seals and directs airflow to the glottis, trachea, and lungs .

95. LMA

96. Contraindications for use of a laryngeal mask P haryngeal abscess or obstructions Restrictive lung diseases that require high inspiratory pressure (> 30 cm H2O). A nonfasting patient also represents a contraindication because the laryngeal mask closes the entrance to the esophagus and trachea, but it does not isolate them from each other; therefore, it does not protect against aspiration in case of regurgitation

97. GUEDEL

98. ENDOTRACHEAL INTUBATION DEFINITION The insertion of a tube through the glottis into the trachea, which allows the patient either to breathe by himself/herself or to receive artificial ventilation

99. TOOLS/EQUIPMENT Suction device Laryngoscope ET tubes of varying size Maggil’s forceps Stylet, Bougie Syringe Stethoscope Ventilation machine

100. TOOLS/EQUIPMENT Laryngoscopes

101. ET TUBES

102. TUBE TYPES The Magill tube Made of plastic (PVC) Represents the standard tube S lightly curved tubes intended for single use only The Murphy tube Has an additional hole, the so-called “Murphy eye,” just in front of the tube tip Ventilation can be performed via this lateral Murphy eye if the main lumen of the tracheal mucous membrane sits closely, or if an atypically arising right main bronchus is to be ventilated.

103. The Woodbridge tube is particularly suitable for operations in the prone position and other operative positions where the tube has to be bent much. The latex spiral tube reinforced with metal is extremely flexible and cannot be bent; thus, a stylet is used to stabilize it during insertion

104. MAGILL FORCEPS Angled forceps Used to guide a tracheal tube into the larynx or an NG tube into the esophagus under direct vision . To remove foreign bodies

105. BOUGIE

106. STYLETS

107. OXYGEN THERAPY

108. OVERVIEW Introduction Indications Oxygen delivery systems Complications of oxygen therapy

109. Goal of oxygen therapy To maintain adequate tissue oxygenation while minimizing cardiopulmonary work

110. O 2 Therapy : CLINICAL OBJECTIVES Correct documented or suspected hypoxemia Decrease the symptoms associated with chronic hypoxemia Decrease the workload hypoxemia imposes on the cardiopulmonary system

111. O 2 Therapy : Indications Documented hypoxemia as evidenced by PaO 2 < 60 mmHg or SaO 2 < 90% on room air PaO 2 or SaO 2 below desirable range for a specific clinical situation Acute care situations in which hypoxemia is suspected Severe trauma Acute myocardial infarction Short term therapy (Post anaesthesia recovery)

112. ASSESSMENT The need for oxygen therapy should be assessed by 1. monitoring of ABG - PaO2, SpO2 2. clinical assessment findings.

113. PaO2 as an indicator for Oxygen therapy PaO2 : 80 – 100 mm Hg : Normal 60 – 80 mm Hg : cold, clammy extremities < 60 mm Hg : cyanosis < 40 mm Hg : mental deficiency memory loss < 30 mm Hg : bradycardia cardiac arrest PaO2 < 60 mm Hg is a strong indicator for oxygen therapy

114. Clinical assessment of hypoxia mild to moderate severe CNS : restlessness somnolence, confusion disorientation impaired judgement lassitude loss of coordination headache obtunded mental status Cardiac : tachycardia bradycardia , arrhythmia mild hypertension hypotension peripheral vasoconst . Respiratory: dyspnea increasing dyspnoea , tachypnea tachypnoea , possible shallow & bradypnoea laboured breathing Skin : paleness, cold, clammy cyanosis

115. MONITORING Physical examination for C/F of hypoxemia Pulse oximetry ABG analysis pH pO2 pCO2 Mixed venous blood oxygenation

116. O 2 Delivery systems

117. O 2 Delivery devices Low flow (Variable performance devices ) Nasal cannula Nasal catheter Transtracheal catheter Reservoir system (Variable performance device) Reservoir cannula Simple face mask Partial rebreathing mask Non rebreathing mask Tracheostomy mask High flow (Fixed performance devices) Ventimask (HAFOE) Aerosol mask and T-piece with nebulisers

118. Oxygen SimpleFace masks: deliver -5-10l/min o2 conc 35-50% Limitations;delivers low o2 conc Reservoir masks {non rebreather mask};high conc o2;10-15l/min Limitationsdelivers only one FiO2:1 Venturi mask;provides high gas flow with a fixed O2 conc of 20-55%; Flow rate 4-15l/ min,advocated for pts with severe hypoxemia

119. NON REBREATHER MASK

120. Complications of Oxygen therapy 1. Oxygen toxicity 2. Depression of ventilation 3. Retinopathy of Prematurity 4. Absorption atelectasis 5. Fire hazard

121. 1. O 2 Toxicity Primarily affects lung and CNS. 2 factors: PaO 2 & exposure time CNS O 2 toxicity (Paul Bert effect) occurs on breathing O 2 at pressure > 1 atm tremors, twitching, convulsions

122. How much O2 is safe? 100% - not more than 12hrs 80% - not more than 24hrs 60% - not more than 36hrs Goal should be to use lowest possible FiO2 compatible with adequate tissue oxygenation

123. Indications for 70% - 100% oxygen therapy Resuscitation Periods of acute cardiopulmonary instability Patient transport

124. Part 4 Maintenance of anaesthesia Basic physiology as applied to breathing during surgery, cardiovascular, bleeding and fluid challenges.

125. Knowledge of basic physiologic principles of respiration assists in: Induction and maintenance of general anesthesia Delivery of mechanical ventilation Discontinuation of mechanical and pharmacologic support Return to the preoperative state. We will take a look at the correlation between anaesthesia and: Hypoxemia- low arterial oxygen tension Hypercarbia Mechanics of the lung and chest wall

126. General Anesthesia and Hypoxemia Following induction of anesthesia, the FRC decreases (average of 500 ml in adults). + volume lost by position change from erect to supine, FRC is reduced close to residual volume. Main cause- loss of muscle tone with consequent cephalad displacement of the diaphragm. Decrease in resting lung volume > decrease in lung compliance, promotes cyclic airway closure at end-expiration > atelectasis > hypoxemia. Mgt ; F io 2  (< 60%) and PEEP

127. Hypercarbia Well tolerated unless severe enough to cause obtundation and respiratory arrest. In susceptible patients, may cause further harm through: Increasing intracranial pressure in patients with cerebral edema. Exacerbating pulmonary hypertension in adults with right ventricular dysfunction In children with congenital heart disease On the other hand, moderate hypercarbia may be a favorable condition in: Circulatory shock- by improving local blood flow In ARDS

128. Mechanics of lung and chest wall Lung and chest wall move in series during respiration. Inward recoil of the lung balances expanding of the chest wall at functional residual capacity, and alveolar pressure is 0. Esophageal balloon allows estimation of transpulmonary pressure (varies in different lung regions). Positive transpulmonary pressure keeps alveoli open; increasing it with PEEP during anaesthesia opposes atelectasis and prevents hypoxemia.

129. Monitoring

130. Aims of monitoring To provide information that improves the safety of anaesthesia . To assess the vital signs. For early detection of any adverse effects and therefore timely correction.

131. Standards of routine monitoring: The continuous presence of a well trained anaesthetist Continuous analysis of the Oxygen content & anaesthetic in the inspiratory gas mixture Neuromuscular monitoring Oxygen supply failure alarm Ventilator disconnection alarm Continuous monitoring of the ECG Pulse oximeter Temperature measurement Capnography Spirometry Hourly observation of urine output via a urinary catheter (1-2mL/min = 2.5L/24hrs)

132. Blood Pressure Arterial blood pressure can be assessed either by direct instrumentation of the vascular tree or by indirect means. a) Indirect Arterial Pressure Monitoring: Involves inflating a cuff proximal to the area of interest to occlude the artery. As the cuff is deflated and inflow resumes, arterial pressure can be determined. Can be done in 4 ways: Palpation Auscultation (Riva- Rocci method) Tonometry- by sensing the occlusive pressure required to stop flow through a superficial artery as it is compressed against a bony prominence. Impedance plethysmography

133. b) Direct Arterial Pressure Monitoring Intra-arterial Pressure Monitoring C) Central Venous Pressure Monitoring - reflects the balance between venous return and right-sided cardiac output. Normal range : 3-10cmH2O ( 1-15mmHg ) . Route of placement of CVP catheter Basilic vein. External/internal jugular veins. Subclavian vein. Femoral vein Complication of this catheter placement Thrombophlebitis. Infection / septicaemia . Pneumothorax / haemothorax . Brachial plexus injury. Air embolism. Pericardial effusion.

134. Electrocardiography Continuous electrocardiography to monitor h eart rate and rhythm, thus early detection of: Arrhythmias Pacemaker malfunction Myocardial ischemia Bradycardia or tachycardia & electrolyte imbalance.

135. Pulse oximetry Estimates arterial oxygen saturation using the change in light absorption across a vascular bed during the arterial pulse. Limitation- reliability is compromised in patients with severe hypoxemia, abnormal arterial pulsations, and hypo perfusion of the site of measurement. Presentation of patients: Hypercapnia Hypoxaemia Somnolence Lethergy Coma Asterixis Restlessness Tremor Slurred speech Headache Papilloedema   Anxiety Tachycardia Tachypnoea Diaphoresis Arrhythmias Altered mental status Confusion Hypertension Hypotension Seizures Lactic acidosis

136. Temperature The continual observation of temperature changes in these patients allows for the detection of accidental heat loss or malignant hyperthermia . Heat is produced as a consequence of cellular metabolism. Perioperative hypothermia predisposes patients to increases in metabolic rate (shivering) and cardiac work, decreases in drug metabolism and cutaneous blood flow, and impairments of coagulation. Sites for taking central core temperatures: bladder, distal esophagus, ear canal, trachea, nasopharynx, or rectum .

137. Capnography & End-tidal CO 2 measurement A capnometer measures the concentration of CO 2 in the inspiratory & expiratory gases, giving a breath-by-breath analysis, & representing this diagrammatically in the form of the capnography. Significance of capnography: Confirmation of tracheal intubation. Recognition of an inadvertent esophageal intubation. Recognition of an inadvertent extubation or disconnection. Assessment of the adequacy of ventilation and an indirect estimate of PaCO 2 . Aids the diagnosis of a pulmonary embolism (e.g . air or clot ). Aids the recognition of a partial airway obstruction Indirect measurement of airway reactivity (e.g., bronchospasm) Assessment of the effect of cardiopulmonary resuscitation efforts.

138. Aims of intraoperative therapy Focus: Analgesia Fluid therapy Other drugs used intraoperatively

139. Analgesics Given to: Reduce the apprehension of the patient in the pre-op period (including the night before the operation) Relieve pain & discomfort when present To augment the action of subsequent anaesthetic agents Some drugs provide some degree of pre-op anaesthesia Types Anxiolytics - benzodiazepines Neuroleptics - Chlorpromazine NSAIDS - Acemetacin , diclofenac, ibuprofen, ketoprofen , rofecoxib , parecoxib & Ketorolac Opioid Analgesics- More likely to be administered at induction. Examples: Alfentanil , Fentanyl & Remifentanil

140. Benzodiazepines Indications: Relief of anxiety- In short procedures Operations under local anaesthesia (including dentistry) Sedation & Amnesia Types: Diazepam PO/IV - Long-acting Temazepam PO - Short-acting Lorazepam PO/IV - Produces more prolonged sedation than temazepam & it has a marked amnesic effects ; used as a premedicant the night before major surgery Midazolam IV/IM

141. Fluid Therapy Aim : Rapidly expand the ECF volume and restore tissue perfusion, Replenish fluid and electrolyte deficits while correcting attendant acid-base abnormalities Meet the patient's nutritional needs, and Maintain optimum body temperature Replace ongoing losses . Normal levels:   Normal plasma Values Na+ 135 - 145 mEq /L K+ 3.5 – 5.1 mEq /L Cl- 98 - 107 mEq /L HCO3+ 22 - 28 mEq /L Ca2+ 8.5 - 10.5 mg/dl Phosphorus 2.5 - 4.5 mg/dl Mg2+ 1.6 - 3 mg/dl Osmolality 280 - 295 mosm /kg

142. Perioperative Fluid Requirements Considerations: Maintenance fluid requirements NPO and other deficits: NG suction, bowel prep Third space losses Replacement of blood loss Special additional losses

143. Maintenance Fluid Requirements Insensible losses such as evaporation from respiratory tract, sweat, faeces , urinary excretion. Occurs continually . Replacement follows the “4-2-1 Rule” 4 ml/kg/ hr for the first 10 kg of body weight 2 ml/kg/ hr for the second 10 kg body weight 1 ml/kg/ hr subsequent kg body weight Extra fluid for fever, tracheotomy, denuded surfaces

144. NPO and other deficits NPO deficit = Number of hours NPO x maintenance fluid requirement. Bowel prep may result in up to 1 L fluid loss. Also consider measurable fluid losses, e.g. NG suctioning, vomiting, ostomy output.

145. Third Space Losses Def: Isotonic transfer of ECF from functional body fluid compartments to non-functional compartments. Depends on location and duration of surgical procedure, amount of tissue trauma, ambient temperature, and room ventilation Replacement: Superficial surgical trauma : 1-2 ml/kg/ hr Minimal Surgical Trauma : 3-4 ml/kg/ hr : head and neck, hernia, knee surgery Moderate Surgical Trauma : 5-6 ml/kg/ hr : hysterectomy, chest surgery Severe surgical trauma : 8-10 ml/kg/ hr (or more): AAA repair, nephrectomy

146. Blood Loss Replace 3 cc of crystalloid solution per 1 cc of blood loss (crystalloid solutions leave the intravascular space) When using blood products or colloids replace blood loss volume per volume i.e. 1:1

147. Phases of fluid replacement Resuscitation: 20 – 40min/ up to 1 hr To restore intravascular volume Give up to 40% of half amount to be given in 24 hours Repletion phase: 5 – 8 hrs To replenish ECF ( interstitial) 60 % of half of amount to be given in 24 hours Early recovery phase 16 – 24 hrs To replenish intracellular volume Rest of half of 24 hrs to be given

148. Fluid therapy cont’d Blood products administered for specific indications; Blood product deficit Red cell concentrates Oxygen carrying capacity Platelets Platelet function(quality or quantity) Fresh frozen plasma Clotting factor deficits Cryoprecipitate Fibrinogen Albumin Low protein or colloid volume replacement Factor concentrates Single clotting factor deficit (often hereditary)

149. Risks of Excess Fluids Interstitial edema Impaired cellular metabolism Poor wound healing Decreased pulmonary compliance Heart failure – overload Delayed return of bowel function Hemodilution

150. Other drugs Muscle Relaxants (Neuromuscular Blocking Drugs) Role: By specific blockade of the neuromuscular junction, they enable light levels of anaesthesia to be employed with adequate; Relaxation vocal cords & allow the passage of a tracheal tube Relaxation of the muscles of the abdomen & diaphragm - patients should always have their respiration assisted or controlled until the drug has been inactivated or antagonized

151. Ctd Antimuscarinics Indications: To dry bronchial & salivary secretions which are increased by intubation, by surgery (to the upper airways), & by some inhalational anaesthetics Used before or with neostigmine to prevent bradycardia, excessive salivation, & other muscarinic actions of neostigmine ; also reversal of non- depolarising neuromuscular block Prevent bradycardia & hypotension associated with drugs e.g. halothane, propofol , & suxamethonium Types: Atropine Sulphate , Hyoscine bromide, phenthiazines

152. REVERSAL OF ANAESTHESIA •What are we reversing? Neuromuscular blockade

153. REVERESAL Spontaneous Reversa l -diffusion, redistribution, metabolism, and excretion of the nondepolarizing relaxant Pharmacological reversal- administration of specific reversal agents

154. Anticholinesterases MOA: Reversibly inactivate acetylcholinesterase enzyme , this indirectly increases the amount of acetylcholine available to compete with the nondepolarizing agent, thereby re-establishing normal neuromuscular transmission

155. Pharmacodynamics Cardiovascular -Decreased heart rate, bradyarrhythmias Pulmonary -Bronchospasm, bronchial secretions Brain -Diffuse excitation Gastrointestinal -Intestinal spasm, increased salivation Genitourinary- Increased bladder tone Ophthalmological -Pupillary constriction

156. Neostigmine Dosage -0.08 mg/kg (up to 5 mg in adults) In practice, many clinicians use a dose of 0.04 mg/kg (or 2.5 mg) if the pre-existing blockade is mild to moderate and a dose of 0.08 mg/kg (or 5 mg) if intense paralysis is being reversed Onset of action - neostigmine (0.04 mg/kg) ,in 5min, peak at 10 min. Duration of action - >1 hr, this is prolonged in geriatric patients Indications : treatment of myasthenia gravis, urinary bladder atony, and paralytic ileus.

157. Pyridostigmine 20% as potent as neostigmine Dosage : up to 0.25 mg/kg (a total of 20 mg in adults). Available as a solution of 5 mg/ mL. Onset of action- 10–15 min, is slower than that of neostigmine Duration of action - >2 h, slightly longer Glycopyrrolate (0.05 mg per 1 mg of pyridostigmine) or atropine (0.1 mg per 1 mg of pyridostigmine) must also be administered to prevent bradycardia. Glycopyrrolate is preferred.

158. Edrophonium Less than 10% as potent as neostigmine. Dosage is 0.5–1 mg/kg. Available as a solution containing 10 mg/mL; it is available with atropine as a combination drug ( Enlon -Plus; 10 mg edrophonium and 0.14 mg atropine per mL). Onset of action (1–2 min)- most rapid Duration of action - shortest, Higher doses prolong the duration of action to more than 1 hr. Less muscarinic effects Atropine (0.014 mg of atropine per 1 mg of edrophonium), Rapid onset of action

159. Concomitant administration of anticholinergic agents Aim : Minimize muscarinic side effects Atropine (0.4 mg of atropine per 1 mg of neostigmine) Glycopyrrolate (0.2 mg glycopyrrolate per 1 mg of neostigmine)- onset of action is similar to that of neostigmine, associated with less tachycardia than is experienced with atropine Side effects : neostigmine crosses the placenta, resulting fetal bradycardia.

160. Physostigmine It is lipid soluble, freely passes the blood– brain barrier. Dosage - 0.01–0.03 mg/kg. Packaged as a solution containing 1 mg/ mL. Indications : rx of anticholinergic toxicity -overdoses of atropine or scopolamine, reversal of some of the central nervous system depression and delirium associated with use of benzodiazepines and volatile anesthetics , preventing postoperative shivering, morphine- induced respiratory depression. Bradycardia is infrequent, but atropine should be available. Almost completely metabolized by plasma esterases , so renal excretion is not important

161. Assessing Reversal Qualitative methods - End points of recovery are sustained tetanus for 5 sec in response to a 100-Hz stimulus(peripheral nerve stimulator) in anesthetized patients or sustained head or leg lift in awake patients. Quantitative methods - acceleromyography