Practical Aspects of Emergency Anesthesia Arun Kumar Paul
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Emergency Anesthesia in GeneralCHAPTER 1

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Management of emergency anesthesia poses one of the most challenging and important tasks needed for the anesthetist. It demands some extra skill, knowledge and experience to tackle the turbulent conditions in emergency situations.
These emergency cases may have uncertain diagnosis, uncontrolled concomitant co-existing medical illness, cardiovascular and metabolic derangements and no sufficient time to prepare for anesthesia and surgery.
Major problems in such cases include vomiting, regurgitation, aspiration of stomach contents, hypovolemia, hemorrhage and abnormal drug effects in presence of electrolyte and fluid disturbances and renal dysfunction.
 
PREANESTHETIC ASSESSMENT
Adequate preanesthetic evaluation of the general condition of the patient.
  • Surgical diagnosis, surgical pathology, magnitude and extent of surgery, urgency of operation, time available for preanesthetic preparation.
  • Any co-existing medical illness, past medical history
  • Any drug therapy such as
    • — Cardiac glycosides, digitalis. Suxamethonium may cause ventricular arrhythmia in digitalized cases, can cause bradycardia to halothane and neostigmine.
    • — Antihypertensive drugs should be continued on the day of surgery. These patients may have labile cardiovascular status.
    • — Beta adrenergic blocking drugs may have additive effects of myocardial depression of volatile anesthetics.
    • — Diuretics can produce hypokalemia, hypovolemia, prolong the effects of muscle relaxants.
    • Steroids: May suffer from adrenocortical insufficiency. Steroid cover is needed in perioperative period.
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    • Antibiotics: Streptomycin, neomycin, kanamycin, polymixin, tetracyclines can potentiate nondepolarizing muscle relaxants.
    • Anticoagulants: Patients with anticoagulant therapy should be controlled before surgery. Regional anesthesia is better avoided in such cases.
    • — MAO inhibitors like phenylzine, nialamide, pargyline, iproniazid, etc. may enhance the action of vasopressor drugs.
    • — Tricyclic antidepressants like imipramine, antitriptyline can enhance prominent anticholinergic effects producing tachycardia, arrhythmia and hypotension.
    • — Sedatives and tranquillizers can potentiate the effects of anesthetics, can cause prolonged recovery and develop hypotension.
 
PHYSICAL EXAMINATION
  • Full physical examination should include cardiovascular system, respiratory system, alimentary system, musculoskeletal system and central nervous system.
  • Assess cardiopulmonary status as far as practicable. Identify anemia, jaundice, cyanosis, edema, if any. Examine the lungs for any basal crepitations and the heart sounds to detect any arrhythmia, irregular rhythm.
  • Evaluate the airway whether or not endotracheal intubation may pose difficulty. Examine the teeth, any denture, loose teeth, any protrusion of upper incisor, full opening of mouth, extension of cervical spine to anticipate safe intubation.
  • Examine the skin condition particularly in cases of regional block.
  • Examination note should always be documented.
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INVESTIGATIONS
  • Hemoglobin estimation, hematocrit, TC, DC, bleeding time, clotting time, prothrombin time.
  • Urinanalysis.
  • Serum elecrolytes, glucose, urea and creatinine.
  • Chest X-ray in selected cases.
  • ECG in all cases above the age of 40 years and where especially indicated.
  • Blood gas analysis where special indications exist.
 
SPECIAL CONSIDERATIONS IN EMERGENCY CASES
 
Volemic Status
The extent of the intravascular volume is most important, otherwise hypovolemia will lead to circulatory collapse during anesthesia. Fluid may be lost during hemorrhage as in trauma or sequestrated in peritonitis, intestinal obstruction, etc.
Assessment of blood loss is essential to restore the intravascular volume deficit. It is usually done with visual estimation, measuring the loss and clinical indicies like pulse, blood pressure, urinary output, CVP and so on. Clinically, the extent of blood loss can be graded as minimal (10% blood volume loss), mild (20% loss), moderate (30% loss), and severe (over 40% blood volume loss).
  • 10% loss: Volume lost about 500 ml. Heart rate, BP, urinary output and CVP more or less normal.
  • 20% loss: Volume loss about 1000 ml. Heart rate 100–120/min, orthostatic hypotension, urinary output 20–30 ml/hr, CVP about–3 cm H2O.
  • 30% loss: Volume loss about 1500 ml. Heart rate 120–140/min, systolic presure below 100 mm Hg, urinary output 10–20 ml/hr, CVP–5 cm H2O, patient is restless, cold and pale.
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  • Over 40% loss: Volume loss over 2000 ml. Heart rate above 140/min, systolic pressure below 80 mm Hg, anuria. Patient is comatose, pale, clammy, cyanosed, CVP–8 cm H2O.
Note:
  • Hypovolemia becomes clinically evident when blood volume is reduced by at least 1000 ml or 20% of blood volume.
  • Classical shock syndrome occurs with a reduction of blood volume more than 30%.
Extracellular fluid volume deficit also needs attention though its assessment is difficult. Hemoconcentration occurs in an increased hemoglobin level and packed cell volume. In cases of severe dehydration, renal blood flow is reduced, renal clearance of urea is reduced and thus increases the level of blood urea. Low sodium content and high osmolality of urine are due to sodium and water conservation by the kidneys.
Main manifestations include weight loss, orthostatic hypotension, poor skin turgor, sunken eyes, tachycardia and reduced intraocular pressure.
It can be clinically graded as mild, moderate and severe as follows:
  • Mild: About 6% body weight lost as water: Thirst, reduced skin elasticity, dry tongue, reduced sweating, low CVP, orthostatic hypotension, apathy, hemoconcentration.
  • Moderate: About 8% body weight lost: Manifestations include hypotension, thready pulse, cold extremities.
  • Severe: More than 10% body weight loss: Manifestations like coma, circulatory collapse are also added. It may even lead to death.
Following assessment of blood volume deficit or extracellular fluid volume deficit, restoration of the deficit is most important with adequate appropriate fluid. Blood transfusion may also be needed in presence of blood loss.
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Full Stomach
  • Emergency cases are always at risk of aspiration of gastric contents mostly due to full stomach. It may be necessary to induce anesthesia urgently before adequate preparation and starvation. Moreover, surgical condition may cause delayed gastric emptying.
  • Vomiting is an active process and can occur during induction and emergence from anesthesia, but regurgitation is passive and can occur at any time, often silently causing aspiration even at deep planes of anesthesia.
  • Gastric contents as little as 25 ml with a pH less than 2.5 can cause severe aspiration pneumonitis.
 
Predisposing Causes
  • Absent or abnormal peristalsis: Peritonitis, metabolic ileus, hypokalemia, uremia, diabetic ketoacidosis, drugs like anticholinergics.
  • Obstructed peristalsis: Intestinal obstruction, gastric cancer, pyloric stenosis.
  • Delayed gastric emptying: Shock, fear, pain, anxiety, trauma, deep sedation, late pregnancy, recent intake of solids/fluids.
  • Miscellaneous: Hiatus hernia, esophageal obstruction, pharyngeal pouch.
Preoperative measures to reduce the risk of regurgitation and aspiration:
  • Delay surgery and allow gastric emptying.
  • Preoperative fasting for 4 to 6 hours.
  • Regional anesthesia may be appropriate.
  • Reduction of gastric volume:
    • — Large bore nasogastric tube to reduce stomach volume.
    • — Metoclopramide facilitates gastric motility and increases lower esophageal sphincter tone.
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  • Increase of gastric pH:
    • — Nonparticulate antacids: Sodium citrate
    • — Histamine antagonists particularly H2 receptor blockers: Ranitidine, Cimetidine
  • Use of antiemetic drugs: Prochlorperazine, ondansetron.
 
PREANESTHETIC MEDICATION
  • Premedication may not be needed in cases of emergency conditions.
  • Sometimes only atropine sulphate is given IV at the time of induction of anesthesia to reduce secretions from the oropharynx and tracheobronchial tree.
  • Proper explanation and reassurance are always helpful to relieve the anxiety and tension.
  • Phenothiazine may be helpful in some cases for its antisialogogue, antiemetic, sedative and tranquillizing effects.
  • Analgesics should be prescribed in selected cases only in presence of pain.
 
Preanesthetic Preparation
  • Cardiovascular resuscitation
    IV fluids, blood transfusion
  • Nasogastric suction of gastric contents as far as practicable
  • Neutralization of the pH of gastric contents: Sodium citrate
  • Premedication, wherever needed.
 
Anesthetic Management
 
Induction
  • Crash induction (Rapid-sequence induction with cricoid pressure):
    • — Preoxygenation for 3 minutes with 100% oxygen (denitrogenation).
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    • — IV anesthetic agent: Thiopentone.
    • — Followed immediately by IV succinylcholine.
    • — Cricoid pressure to occlude the esophagus and press the larynx to improve visualization
    • — Place the endotracheal tube under direct laryngoscopy.
    • — Cricoid pressure should be maintained till verification of proper endotracheal intubation.
  • Awake intubation: Blind nasal intubation may be tried in awake patient rendering the upper airway insensitive by local anesthetic.
  • Inhalational induction:
    • — Patient should be in left lateral, head down position.
    • — Nitrous oxide, oxygen and halothane/isoflurane by facemask.
    • — Followed by attempt to laryngoscopy and endotracheal intubation during spontaneous ventilation.
 
Maintenance of Anesthesia
  • N2O + O2 + halothane/isoflurance; IPPV.
  • N2O + O2 + intermittent doses of analgesic like pethidine and muscle relaxants like pancuronium/vecuronium/atracurium; IPPV.
Adequate fluid management is essential during operation. Blood transfusion may be necessary in cases of blood loss in excess of 15% blood volume in adults and 10% in children.
Monitoring of vital signs is essential during anesthesia and surgery.
 
Reversal and Emergence: Recovery from Anesthesia
  • At the end of surgery, volatile anesthetics, if used should be discontinued a few minutes before the surgery finishes.
    • — Direct pharyngoscopy and removal of secretions from pharynx.
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    • — Extubation should be done gently when the patient is awake.
    • — Tonsillar position.
  • If nondepolarizing muscle relaxants are used, adequate decurarization should be done with IV atropine and neostigmine. Ventilation is maintained manually so that spontaneous respiratory activity returns.
    • — Extubation should be done when the trachea regains adequate protective reflexes. Patient should regain consciousness and fully awake.
    • — Patient should be kept in lateral position.
    • — Adequacy of neuromuscular function should always be guaranteed before sending the patient to the recovery room.
 
Postoperative Management
  • Oxygen therapy.
  • IPPV, if required.
  • Monitoring of vital signs is essential.
  • Fluid therapy should be meticulous.
  • Nasogastric suction and measurable losses should always be replaced.
  • Blood transfusion may be needed with proper assessment of blood loss.
  • Postoperative analgesics may be needed.
  • Postoperative ventilatory assistance may be needed in certain conditions such as:
    • — Shock.
    • — Severe sepsis, peritonitis
    • — Upper abdominal/thoracic surgery
    • — Aspiration pneumonitis
    • — Morbid obesity
    • — Low general condition
    • — Severe ischemic heart disease
    • — Prolonged massive trauma/surgery.
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REGIONAL ANESTHESIA
The use of regional anesthesia is mostly safe and suitable for emergency surgery. Nerve blocks, spinal and epidural anesthesia are mostly satisfactory provided adequacy of extracellular fluid volume or vascular volume is maintained. These techniques satisfy the surgical needs such as immobility of the operative part, analgesia and profound muscular relaxation. Moreover, these have little effect on physiological response to injury (surgery) and continued analgesia in the postoperative period. Catheter technique of epidural analgesia can provide prolonged period of anesthesia, whenever needed.