Complications of General Anesthesia

General anesthesia (GA) • State produced when a patient receives medications for amnesia,

analgesia, muscle paralysis, and sedation. • An anesthetized patient - in a controlled, reversible state of

unconsciousness. • Enables a patient to tolerate surgical procedures that would

otherwise inflict unbearable pain, potentiate extreme physiologic exacerbations, and result in unpleasant memories.

• The combination of anesthetic agents used for general anesthesia often leaves a patient– Unarousable even secondary to painful stimuli– Unable to remember what happened (amnesia)– Unable to maintain adequate airway protection and/or spontaneous

ventilation as a result of muscle paralysis– Cardiovascular changes secondary to stimulant/depressant effects of

anesthetic agents

• General anesthesia uses intravenous and inhaled agents to allow adequate surgical access to the operative site

• Anesthesia providers are responsible for assessing all factors that influence a patient's medical condition and selecting the optimal anesthetic technique accordingly.

• Disadvantages– Requires increased complexity of care and associated

costs– Requires some degree of preoperative patient preparation– Can induce physiologic fluctuations that require active

intervention– Associated with less serious complications such as nausea

or vomiting, sore throat, headache, shivering, and delayed return to normal mental functioning

– Associated with malignant hyperthermia, a rare, inherited muscular condition in which exposure to some (but not all) general anesthetic agents results in acute and potentially lethal temperature rise, hypercarbia, metabolic acidosis, and hyperkalemia

• Complications of anesthesia are inevitable even with most experienced Doctors.

• These complications range from minor to catastrophic.

• Incidence of perioperative mortality due to anesthetic cause accounts to less than 1:20,000.

Classification..

• Respiratory complications • Cardiovascular complications • Neurological complications • PONV • Temperature changes • Adverse drug effect and hypersensitivity• Miscellaneous

Respiratory complications

• Complications of laryngoscopy and intubation • Hypoxemia • Hypercapnia • Aspiration pneumonia• Atelectasis• Pneumothorax

Complications of laryngoscopy and intubation

• Endotracheal tube (ETT) positioning: – Esophageal intubation– Endobronchial intubation – Airway trauma:

– Tooth damage, soft tissue injury– Dislocated mandible.– Sore throat– Pressure injury on trachea– Edema of glottis or trachea– Post intubation granuloma of vocal cords

• Physiologic responses to airway instrumentation:– Sympathetic stimulation , increase in Intracranial pressure– Laryngospasm – Bronchospasm

• ETT malfunction: – Risk of fires – Kinking causing obstruction– Cuff perforation

Hypoxemia

• PaO2 < 60 mmHg or SaO2 < 90% Causes: – Low delivery of O2 , unintended extubation– Obstruction – ETT block/ kink, bronchospasm– V/Q mismatch– Increased O2 utilization by tissues – Tissue hypoxia– Embolism (air, fat, thrombi)– Pneumothorax

Usually in disease statesOr related to surgical procedure

Hypercapnia

• PaCO2 >45 or ETCO2 > 40 mmHg. • Causes: – Hypoventilation – Increased dead space – Increased CO2 production by tissues– V/Q mismatch– Pneumothorax/ Capnothorax– Laparoscopic surgeries

Pulmonary aspiration

• Incidence and severity increase in emergency cases, especially patients with delayed gastric emptying such as CS, intestinal obstruction.

• Aspiration of material with a pH less than 2.5 causes extensive lung damage.

• Manifestations: The patient may become hypoxic, tachycardic and tachypnoeic. Bronchospasm often occurs and auscultation of the chest may reveal wheeze and crepitations.

Hemodynamic Complications

1. Hypotension – Causes : • Anesthetic drugs, inhalational agents• hypovolemia• decreased myocardial contractility, cardiac tamponade. • decreased systemic vascular resistance, • cardiac dysrhythmias • pulmonary embolus • pneumothorax

2. Hypertension – Causes: enhanced SNS activity ,preoperative

hypertension, hypervolemia, hypoxemia, increased intracranial pressure, and vasopressors

3. Cardiac dysrhythmias – Causes: hypoxemia, hypercarbia, hypovolemia,

pain, electrolyte and acid-base imbalance, myocardial ischemia, increased ICP, digitalis toxicity, hypothermia, anticholinesterases and malignant hyperthermia.

Neurological complications

• Awareness: Incidence: 0.2% Increased in obstetric, cardiac anesthesia and septic patients.

• Delayed recovery: Metabolic and electrolyte causes, cerebral hypoperfusion, cerebral depression by drugs, prolonged neuromuscular block leading to respiratory paralysis.

• Perioperative Neuropathy: related to positioning• Cervical spine injury : related to laryngoscopy and

intubation

Postoperative Nausea and Vomiting

• Patient risk factors: short fasting status, anxiety, young age, female, obesity, gastroparesis, pain, history of postoperative nausea/vomiting or motion sickness.

• Surgery-related factors: gynecological, abdominal, ENT, ophthalmic, and plastic surgery; endocrine effects of surgery; duration of surgery.

• Anesthesia-related factors: premedicants (morphine and other opioids), anesthetics agents (nitrous oxide, inhalational agents, etomidate, methohexital, ketamine), anticholinesterase reversal agents, gastric distention, longer duration of anesthesia, mask ventilation, intraoperative pain medications, regional anesthesia.

• Postoperative factors: pain, dizziness, movement after surgery, premature oral intake, opioid administration.

Miscellaneous

• Hypothermia: It is unintentional decrease of core body temperature to < 35 C during anesthesia– Causes: Drop in core temperature. Central inhibition of

thermoregulation. – Contributing factors: Extremes of age, prolonged surgery,

cold infusion or irrigation fluids, muscle relaxants.• Allergic Drug Reactions :anaphylaxis, anaphylactoid

reactions• Renal dysfunction: Oliguria (urine output less then 0.5

mL/kg/hour) reflects decreased renal blood flow due to hypovolemia or decreased cardiac output

Malignant Hyperthermia • It is a fulminant skeletal muscle hypermetabolic syndrome occurring in genetically susceptible patients after

exposure to an anesthetic triggering agent. • Incidence and mortality :Children 1:15,000, Adults: approx

1:40,000 with succinylcholine & approx 1:220,000 when agents other than succinylcholine are used.

• Familial autosomal dominant transmission. Mortality: 10% overall; up to 70% without dantrolene therapy. Early therapy reduces mortality for less than 5%.

• Triggering anesthetics: halothane, enflurane, isoflurane, desflurane, sevoflurane, and succinylcholine.

• Early signs: tachycardia, tachypnea, unstable blood pressure, arrhythmias, cyanosis, mottling, sweating, rapid temperature increase, and cola-colored urine.

• Late (6-24 hours) signs: pyrexia, skeletal muscle swelling, left heart failure, renal failure, DIC, hepatic failure.

‘‘ Before whom, In all time, Surgery was Before whom, In all time, Surgery was Agony Agony

By whom, pain in surgery was averted By whom, pain in surgery was averted

Since whom, science has control over Since whom, science has control over pain‘pain‘

Inscribed on the tombstone of W T G Morton - the father of Anesthesia