Deep sedation: what it is, when it’s used, and how it differs from mild sedation

Sedation is a medical technique of pharmacological control of consciousness that enables patients to undergo many diagnostic and therapeutic procedures while reducing anxiety and pain.

There are different levels of sedation depending on intensity: mild, moderate, and deep. These levels differ in terms of drug choice, dosage, and patient response.

Deep sedation is an advanced anesthetic technique during which the patient:

• is not conscious;
• does not respond to verbal or light tactile stimuli;
• may, in some cases, react to intense painful stimuli;
• does not recall anything about the procedure upon awakening.

During deep sedation, spontaneous breathing may be reduced or absent: for this reason, oxygen supplementation or assisted ventilation may be required.

“It is therefore essential that it be performed by anesthesiologists in fully equipped environments, capable of managing any respiratory compromise,” emphasizes Dr. Taddei.

Deep sedation is induced and maintained through intravenous administration of drugs, in higher doses than in moderate sedation:

• sedative-hypnotics/anesthetics;
• opioid analgesics.

Sedatives act on the central nervous system to reduce the state of consciousness. The main drug used is propofol, which has a rapid onset of action and allows precise control over sedation depth. It has no analgesic effect, but may cause hypotension and respiratory depression.

Other sedatives include midazolam (a benzodiazepine) with anxiolytic, hypnotic, and amnesic properties, though with a slower onset and longer duration than propofol.

Opioid analgesics are often combined with sedatives to control pain. Commonly used agents include fentanyl and remifentanil.

Antagonist drugs act as antidotes in cases of excessive sedation or respiratory depression, such as:

• flumazenil, a benzodiazepine antagonist;
• naloxone, an opioid antagonist.

Propofol has no available antagonist.

Before sedation, it is necessary to:

• fast: at least 6 hours for food and 2 hours for clear fluids;
• sign informed consent, confirming understanding of the sedation procedure, its benefits, and potential risks;
• complete a self-assessment questionnaire, reporting previous surgeries, adverse reactions or anesthesia-related problems, drug allergies, and cardiovascular or respiratory conditions.

It is important to be accompanied by an adult, as driving or returning home alone is not permitted after sedation.

During deep sedation, continuous monitoring is essential and includes:

• electrocardiogram (ECG);
• oxygen saturation;
• intermittent blood pressure measurement;
• assessment of consciousness;
• monitoring of ventilation and respiratory function.

The duration depends on the type of procedure performed.

Recovery is usually rapid and gradual once drug administration is stopped: the patient regains consciousness, may feel slightly drowsy or disoriented in the first minutes, but these effects typically resolve within about one hour.

After the procedure, observation in a controlled environment is required to ensure stable vital signs and safe recovery.

Deep sedation is indicated for painful, invasive procedures or those requiring complete patient immobility, such as:

• endoscopies: colonoscopy in cases of intestinal adhesions, elongated colon, previous surgeries, chronic inflammatory diseases, or operative colonoscopies; gastroscopy in cases of esophagitis, ulcers, or operative gastroscopies;
• bronchoscopies;
• cardioversions;
• certain dental or pediatric procedures.

Deep sedation offers several advantages:

• ensures complete comfort and absence of pain, as the patient feels no pain or discomfort during the procedure;
• reduces anxiety, fear, and stress, helping to calm anxious or uncooperative patients;
• facilitates complex procedures by eliminating involuntary movements, allowing physicians to perform delicate interventions with precision;
• is ideal for children or non-cooperative patients;
• enables rapid recovery thanks to short-acting drugs.

Although frequently used, deep sedation carries non-negligible risks. These are rare when performed properly by trained personnel in appropriate settings. Possible complications include:

• respiratory depression (reduction of spontaneous breathing), requiring oxygen or ventilatory support;
• upper airway obstruction (loss of pharyngeal tone), managed with specific maneuvers;
• hypotension and bradycardia;
• increased risk in elderly, hypovolemic, or cardiac patients;
• paradoxical reactions such as agitation, aggression, disinhibition;
• nausea, vomiting, aspiration;
• allergic or anaphylactic reactions;
• accidental overdose;
• delayed recovery.

Deep sedation is contraindicated in cases of:

• lack of adequate setting or trained personnel;
• patient not fasting;
• known drug allergies;
• refusal by the patient or legal guardian.

Other situations require careful specialist assessment, such as:

• obstructive sleep apnea syndrome (OSAS), due to increased risk of airway obstruction and apnea;
• COPD or chronic respiratory failure, due to reduced respiratory reserve;
• severe heart disease (heart failure, unstable arrhythmias, severe aortic stenosis);
• severe obesity (BMI > 35–40), often associated with difficult airway management and OSAS;
• advanced age or frailty;
• neurological disorders (e.g., epilepsy, dementia);
• pregnancy, except when strictly necessary.

Light sedation, also called conscious sedation, is a controlled state of relaxation that reduces anxiety and discomfort without impairing patient consciousness. During light sedation:

• the patient remains awake and alert;
• responds easily to verbal stimuli;
• can cooperate during the procedure.

Unlike deep sedation, where the patient is unconscious and may require respiratory support, vital functions remain intact during light sedation. For this reason, it is considered a safe, well-tolerated option, especially when patient responsiveness is needed.

Light sedation involves lower drug doses with primarily anxiolytic effects and is indicated for brief, minimally invasive, and non-painful procedures, such as:

• simple diagnostic endoscopies without complex maneuvers;
• short diagnostic or interventional exams;
• minor outpatient surgeries;
• common exams such as MRI in uncooperative patients;
• dental procedures.

Light sedation can be administered by non-anesthesiologist physicians who are adequately trained, in equipped settings, with basic monitoring and immediate availability of specialists for emergencies.