The Difference Between Analgesia and Anesthesia

The main difference between Analgesia and Anesthesia is that Analgesia is a pain-free state without loss of consciousness, whereas anesthesia is a state achieved when there is a loss of touch, pain, and temperature sensations with or without loss of consciousness.

Anesthesia is associated with some degree of analgesia but not vice versa. 

What then differentiates a state of sleep from anesthesia? One can be awakened from a sleep state, whereas someone under general anesthesia has to be monitored carefully for a few hours and recovers only after the effect of the anesthetic agent wears off.

Most over-the-counter analgesics are oral, whereas anesthetics are available as topical, injectable, and inhaled formulations. Relieving pain has been shown to result in improved healing, faster recovery, and an earlier return to former activities and lifestyle. (1)

Mechanism of Action of Analgesics and Anesthetics

The most widely used class of analgesics, namely, NSAIDs, work by blocking the synthesis of prostaglandins, which are key mediators of the inflammatory process. This mechanism, in turn, helps reduce the stimulation of free nerve endings and blocks the transmission of pain signals. Opioids, on the other hand, act on both the peripheral nerves and the brain and alter pain perception.

When local anesthetics are injected around a nerve, they block the sodium channels present on the nerve. This blocking effect is voltage-dependent, which means that thin nerve fibers that conduct signals faster, such as the pain fibers, are blocked significantly more effectively than larger nerves. (2)

General anesthetics can be administered as a gas or intravenously. They produce a loss of pain, touch, temperature, and reflexes accompanied by loss of memory and consciousness. General anesthetics depress the central nervous system mainly through their effects on the inhibitory neurotransmitter GABA.

Indications for Analgesia

Typically, NSAIDs, aspirin, and paracetamol are used to treat mild to moderate pain arising from superficial structures such as the skin, bone, and joint. These drugs share advantages in being nonprescription, safe, and easy to use.

Recommendations for the use of more potent opioids are moderate to severe pain from deeper body parts. Both types of analgesics are used for acute pain that is tolerable.

The common indications for oral analgesics include:

Indications for Anesthesia

Local anesthesia can be administered in various ways:

1. Topically: As creams and sprays to numb the skin or mucous membranes in the nose and oral cavity. EMLA is a cream that combines two local anesthetics and is used for placing intravenous cannulas, blood sampling, and minor procedures. (3)(4)
2. Subcutaneously: Around nerve fibers.
3. Regionally: In the following two ways:
   • Spinal anesthesia: The local anesthetic is injected into the cerebrospinal fluid surrounding the spinal cord.
   • Epidural anesthesia: The anesthetic is injected via a small thin needle into space between the spine and the dural sac, which contains nerve roots and spinal fluid.

Indications

Local anesthesia is preferred for minor surgeries where the pain is tolerable, and the patient is calm. Local anesthetic injections are used to cause analgesia in the painful muscles while a patient completes physical therapy. 

Long-acting local anesthetics are used to treat chronic muscle and nerve-related pain. Peripheral neuropathies, such as meralgia paresthetica and occipital neuralgia, are typically treated with long-acting local anesthetics.

Local anesthesia is safer than general anesthesia and has many advantages, such as:

General anesthesia is administered for surgeries that may interfere with vital cardiac, respiratory, and brain processes and involve the following areas:

• Chest: Such as cardiac surgeries and chest wall injuries
• Abdomen: Such as hernia repairs and appendix removal
• Head and neck: Such as cancer removal and reconstruction procedures
• Shoulder: Such as joint replacement

A specialist called an anesthetist administers the drug and monitors the patient’s breathing and heart function with the use of medical devices.

Also, the patient will need to be monitored postoperatively to ensure recovery from the effects of the anesthetic and normalization of body functions. The patient is usually advised not to drive or operate heavy machinery for at least 24 hours after receiving anesthesia.

Contraindications and Precautions

Traditional NSAIDs such as ibuprofen, opioids such as morphine, and other analgesics such as acetaminophen are the mainstay of acute and chronic pain management. Each of these drugs needs to be used cautiously in certain subgroups of patients.

NSAIDs

• The risk of bleeding ulcers and perforation is increased when certain factors are present such as old age, smoking, alcohol consumption, long duration of analgesic use, and preoperative diagnosis-existing gastric inflammation.
• Most NSAIDs can cause renal deterioration in patients with preexisting kidney dysfunction. In such patients with renal compromise, acetaminophen is the safest analgesic.
• The risk of bleeding is increased when NSAIDs are combined with anticoagulants.
• Aspirin can cause hypersensitivity reactions in patients with asthma or eczema.

Opioids

• There is an additive sedative effect when opioid analgesics are combined with alcohol, benzodiazepines, and barbiturates.
• Opioid analgesics can lead to tolerance and dependence.

General anesthesia/epidural anesthesia

• Absolute contraindications are patient refusal and severe coagulation abnormalities.
• Other relative contraindications include skin infections, raised intracranial pressure, spinal abnormalities, and sepsis.

Combining Analgesia and Anesthesia

General anesthetics are rarely administered as sole agents for complex operative procedures. A combination of adjuvants, such as analgesics and/or skeletal muscle relaxants, are coadministered to achieve the desired state of surgical anesthesia.

Local and regional anesthesia can be used as an alternative or in addition to conventional pain control during and after surgery and the immediate period after childbirth. Analgesic opioids given as regional analgesia and intravenous patient-controlled analgesia (PCA) have demonstrated effective control of postoperative pain. (5)(6)

Epidural analgesia can also be used as the sole anesthetic agent for surgeries and can be used as the primary anesthetic for surgeries from the chest to the lower extremities.

This method of combining opioid/non-opioid analgesics with anesthesia helps reduce the pain along with the dose and side effects of opioid analgesics, such as nausea, vomiting, slowing of bowel movements leading to constipation, and sedation. (7)(8)

The focus of this combination technique helps:

1. Provide optimal conditions for surgery
2. Prevent postoperative complications
3. Decrease postoperative morbidity and mortality

Side Effects of Analgesia Versus Anesthesia

Final Word

• Treatment of acute and chronic pain associated with disease or trauma with analgesics helps reduce morbidity and improves the quality of life.
• The oral administration of common NSAIDs and opioid analgesics is associated with systemic adverse effects such as gastric irritation, renal dysfunction, sedation, constipation, and physical dependence.
• Local anesthesia is safer than general anesthesia and overcomes the systemic adverse effects of oral analgesics by numbing the specific area of interest.
• Traumatic pain that is intolerable and major surgical procedures that may interfere with important physiological functions are important indications for general anesthesia.
• The combination of anesthesia and systemic analgesics has been used to treat postoperative pain.