Anaesthetic management of the surgical patient

Outline Introduction History and Physical Examination Special Investigations Risk Assessment Preoperative therapy Premedication Intraoperative management Post-operative management

Introduction Pre-operative visit is essential to assess “fitness for anaesthesia” Aims of the visit: -Establish a rapport Obtain a history and perform a physical examination Assess the risks of anaesthesia and surgery Institute preoperative management Prescribe premedication and plan the anaesthetic management Establishment of rapport

History and physical Examination- History History- ask direct questions about allergy, infections, blood transfusion, previous anaesthetics, diseases of the CVS and RS Smoking Alcohol Drug history- administration of most drugs should be continued up to and including the morning of operation and some should be discontinued

Physical Examination A full PE should be undertaken and documented in the case records Assessment of ease of tracheal intubation- examine teeth for presence of caries, caps, loose teeth and protruding upper incisors, mouth opening, cervical spine flexion

Special Investigations Before ordering extensive investigations, the anaesthetist should ask himself: -will the investigations yield information not revealed by physical investigations? Will the results of the investigationalter the management of patients? Guidelines: Urine analysis, HB, Eand U, Cr,LFT, CXR, ECG,Sickle status, ABG, Sickle status

Risk assessment ASA=American Society of Anaesthesiologists Physical status scale Mortality rates after anaesthesia and surgery each ASA physical status(%) ASA 1 = Healthy patient (0.1) 11= Mild systemic disease (0.2) 111=moderate systemic disease (1.8) IV =Severe systemic disease ( 7.8) V= Moribund patient (9.4)

Prediction of risk factors in general Important factors in predicting post-op morbidity and mortality in decreasing order: Clinical assessment- ASA>3 Cardiac failure Cardiac risk index Pulmonary disease Pulmonary abnormalities confirmed by X-ray ECG abnormalities

Common causes of postponing surgery Acute upper respiratory tract infection Existing medical disease which is not under optimum control Emergency surgeru for which the patient has not been resuscitated adequately Recent ingestion of food- the 4-6-8 rule Failure to obtain informed consent Drug therapy

Preoperative therapy Respiratory disease- optimise Cardiovascular disease-e.g. hypertension Obstructive jaundice- start iv infusion the night before surgery Blood transfusion requests- depends both on the nature of the surgery and patient features

Premedication =administration of drugs in the period 1-2h before induction of anaesthesia, The objectives are: 1. Allay anxiety and fear (Psychotherapy) Reduce secretion Enhance the hypnotic effect of general anaesthetic agents Reduce post op nausea and vomiting Produce amnesia Reduce the volume and increase the pH of gastric contents Attenuate vagal reflexes Attenuate sympathoadrenal responses

Drugs used for premedication Benzodiazepines eg diazepam, lorazepam Opioid analgesics Butyrophenones e.g haloperidol, droperidol Phenothiazines Anticholinergics e.g atropine, hyoscine and glycopyrronium

induction Objective of modern anaesthesia is to rapidly obtain a state of unconsciousness, to maintain this state and then achieve a rapid recovery. Modern anaesthesia thus involves the use of several drugs to provide hypnosis, analgesia and muscular relaxation Methods available for induction -Intravenous - Inhalational - Intramuscular: ketamine only

Tracheal intubation Indications – 2 major ones: 1. to ensure airway patency 2. to protect the airway from aspiration Airway patency important in: Prolonged operations Operations where access to the airway is difficult Operations involving excessive movement of the head and neck Use of LMA or face mask is unsuitable Where a major intraoperative complication develops

Protection from aspiration Use a cuffed endotracheal tube to prevent aspiration eg for: Potential for vomitting and aspiration Situations of extensive bleeding from the mouth, nose or oropharynx Thoracic operations

Inhalational anaesthetic agents Inhalational agents Anaesthetic gases Di-ethyl ether Halothane Isoflurane Enflurane Sevoflurane Desflurane Nitrous oxide Oxygen

Intravenous agents Muscle relaxants Sodium thiopentone Propofol Ketamine Suxamethonium Pancuronium Atracurium Vecuronium Antagonists Neostigmine Pyridostigmine

Complications following the use of Muscle relaxants Inadequate ventilation Residual paralysis Prolonged apnea

Care of the unconscious patient Emergence can be associated with major morbidity, especially from respiratory and cardiovascular complications. The patient may develop airway obstruction or inadequate ventilation with subsequent hypoxaemia and hypercapnia and is at increased risk of aspiration due to the absence of protective airway reflexes. Effects of ongoing blood losses and residual drug effects Observation and early intervention during this period is crucial

Criteria to be met before transfer from recovery room to general ward Level of consciousness -obeys command -Spontaneous eye opening Respiratory system -upper airway -respiration Pain control -adequate pain control -adequate analgesic and anti-emetic provisions Cardiovascular system -haemodynamically stable -pulse rate acceptble -blood pressure acceptable -No persistent bleeding -Peripheral perfusion adequate Temperature No hypothermia or malignant hyperthermia

Comparison of methods of induction INTRAVENOUS Advantages Rapid onset Dose titratable Depression of pharyngeal reflexes Anti-emetic /anticonvulsant Disadvantages Venous access required Risk of hypotension Apnoea common Loss of airway control anaphylaxis INHALATIONAL Advantages Avoids venepuncture Respiration is maintained Slow loss of protective reflexes End tidal concn can be measured Upper oesophageal tone maintained Disadvantages Slow process Potential excitement phase Irritant and unpleasnt Pollution May cause a rise in ICP/IOP