Sedation for patients undergoing procedures in the cardiac catheterization laboratory (CCL) can be managed by the primary physician with nursing staff or by a dedicated anesthesiology team. The choice of sedation and/or anesthetic techniques is dependent on institutional policies, patient and physician preference, and the type of procedure being performed. This discussion will focus on interventional procedures in the CCL and not hybrid operating room procedures that add an additional layer of complexity and more often than not will be staffed with an anesthesia team.
CCL sedation offers patient comfort (analgesia and anxiolysis) during invasive procedures requiring patients to hold still, potentially for long periods, without resorting to general anesthesia. In pediatric populations and uncooperative adults, either deep sedation or general anesthesia, provided by an anesthesiology care provider, is typically warranted. General anesthesia may also be warranted for patients who cannot lie flat due to cardiac or pulmonary pathology or joint pain. General anesthesia is also frequently used for patients requiring transesophageal echocardiography as part of their procedure.
At times, these sedation practices may result in cardiac or respiratory depression; these must be rapidly recognized and appropriately managed to avoid the risk of hypoxic brain damage, cardiac arrest, or death. Conversely, inadequate sedation/analgesia may result in undue discomfort, patient injury due to lack of cooperation, or adverse physiologic or psychological response to stress.1
In general, patients managed with moderate sedation will have a shorter recovery period prior to return to their hospital room or discharge home. There may also be a shorter room turnover time for patients managed with sedation versus general anesthesia. Patients receiving general anesthesia must be recovered in a unit staffed with nurses trained in recovery of postanesthesia patients. If this unit is distant from the interventional area, room turnover will be delayed during transport of patients and transfer of care to the recovery team. Moderate sedation administered by a nurse under the supervision of the cardiologist may decrease the resource utilization and total institutional cost for the procedure by avoiding usage of these additional resources.
Sedation (minimal, moderate, or deep) and general anesthesia are defined points on an otherwise continuous scale of sedation defined by anesthesiologists (Table 20-1). At the origin of this scale, the individual is fully awake and conscious; at the opposite end, he or she is unarousable, apneic, and possibly hemodynamically unstable.
| Minimal Sedation | Moderate Sedation | Deep Sedation | General Anesthesia | |
|---|---|---|---|---|
| Responsiveness | Normal response to verbal stimulation | Purposeful response to verbal or tactile stimulationa | Purposeful response following repeated or painful stimulationa | Unarousable even with painful stimuli |
| Airway | Unaffected | No intervention required | Intervention may be required | Intervention often required |
| Spontaneous ventilation | Unaffected | Adequate | May be inadequate | Frequently inadequate |
| Cardiovascular function | Unaffected | Usually maintained | Usually maintained | May be impaired |
Minimal sedation (anxiolysis): A drug-induced state during which patients respond normally to verbal commands. Although cognitive function and coordination may be impaired, ventilatory and cardiovascular functions are unaffected.
Moderate sedation/analgesia (conscious sedation): A drug-induced depression of consciousness during which patients respond purposefully (reflex withdrawal from a painful stimulus does not constitute a purposeful response1) to verbal commands, either alone or accompanied by light tactile stimulation. No interventions are required to maintain a patent airway, and spontaneous ventilation is adequate. Cardiovascular function is usually maintained.
Deep sedation/analgesia: A drug-induced depression of consciousness during which patients cannot be easily aroused but respond purposefully (again, reflex withdrawal from a painful stimulus does not constitute a purposeful response1) following repeated or painful stimulation. The ability to independently maintain ventilatory function may be impaired. Patients may require assistance in maintaining a patent airway, and spontaneous ventilation may be inadequate. Cardiovascular function is usually maintained.
General anesthesia: A drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation. The ability to independently maintain ventilatory function is often impaired. Patients often require assistance in maintaining a patent airway, and positive-pressure ventilation may be required due to depressed spontaneous ventilation or drug-induced depression of neuromuscular function. Cardiovascular function may be impaired.
Because sedation is a continuum, it is not always possible to predict how an individual patient will respond to a given sedation strategy. Consequently, practitioners intending to produce a given level of sedation should be able to care for and rescue the patient whose level of sedation becomes deeper than initially intended. Individuals administering moderate sedation/analgesia (conscious sedation) should be able to rescue patients who enter the state of deep sedation/analgesia; those administering deep sedation/analgesia should be able to manage the situation where the patient enters the state of general anesthesia.
Each hospital is normally accredited by the specific credentialing body regarding the types of practitioners who can provide sedation outside of the operating room, as well as which levels of sedation are allowed. These policies are not universal across institutions but will provide both guidance and limitations of the sedation practice and establish minimum standards of care. Additionally, there may be provisions regarding provider recertification, equipment use, and other elements particular to a given hospital.
A thorough history and physical examination are the first steps in selecting the proper sedation technique for the specific patient and the procedure. Special emphasis should be given to the history of previous anesthetic problems, medication and contrast dye allergies, and tolerance to alcohol and recreational drugs, as these may alter the sedation approach. It is also advisable to inquire about rare but potentially critical complications such as family history of malignant hyperthermia, use of medications with potential for serious adverse reactions such as long-term amiodarone, cancer chemotherapy with bleomycin or doxorubicin, and severe or debilitating illness.1
Physical examination should address, at a minimum, pulmonary and cardiovascular status as well as assessment of the airway. The most common airway assessment tool is the Mallampati3 score, which assigns grades I to IV based on soft palate and uvula visualization with the patient’s mouth opened (Fig. 20-1). Patients with scores of III and IV, as well as those with receding mandibles (defined as having <3 fingerbreadths distance between the chin and the hyoid bone), obese patients, or patients with full beards, may be more difficult to ventilate and may present a challenge should endotracheal intubation become necessary. Finally, a review of past anesthetic records may clarify the degree of difficulty in managing the patient’s airway when the physical exam is nonreassuring or if the patient has a history of airway surgery.
Based on the results of the history and physical examination, a given patient can be classified as 1 of the 6 American Society of Anesthesiologists (ASA) classes (Table 20-2). The ASA classification stratifies the complexity of the patient’s comorbidities in order to develop the sedation management strategy, predict outcome expectations, and assist with resource management. Additionally, the ASA status is often included in the research data as an overall means of intraoperative complication risk assessment.1 For patients receiving sedation, a minimum 6-hour fasting period is recommended, with the exception of clear fluids, which can be continued to within 3 hours of the procedure. The fasting time should be increased in patients with known delayed gastric emptying to mitigate aspiration risk.1,4
| ASA Class | Definition |
|---|---|
| Class I | A healthy patient |
| Class II | A patient with mild systemic disease |
| Class III | A patient with severe systemic disease |
| Class IV | A patient with severe systemic disease that is a constant threat to life |
| Class V | A moribund patient not expected to survive without the procedure |
| Class VI | A brain-dead patient whose organs are being donated |
| E | An add-on modifier to ASA class to indicate emergency surgery |
Treatment with metoclopramide or a nonparticulate antacid may benefit some patients with delayed gastric emptying or increased gastric acid secretion, but indiscriminate use in all patients is not recommended.4
The ASA taskforce recommends that a designated individual, other than the practitioner performing the procedure, should be present to monitor the patient throughout a procedure that is performed with sedation/analgesia; during deep sedation, this individual should have no other responsibilities. However, during moderate sedation, this person may assist with minor, interruptible tasks once the patient’s level of sedation/analgesia and vital signs have stabilized, provided that adequate monitoring for the patient’s level of sedation is maintained.
Individuals responsible for patients receiving sedation/analgesia should understand the pharmacology of the administered agents, as well as the role of pharmacologic antagonists for opioids and benzodiazepines. Individuals monitoring patients receiving sedation/analgesia should be trained to recognize the associated complications. At least 1 individual capable of establishing an advanced airway and positive-pressure ventilation as well as means for summoning additional assistance should be available whenever sedation/analgesia is administered. It is recommended that an individual with advanced life support skills be immediately available (within 5 minutes) for moderate sedation and within the procedure room for deep sedation.
Pharmacologic antagonists and appropriately sized equipment for establishing an advanced airway and providing positive-pressure ventilation with supplemental oxygen should be present whenever sedation/analgesia is administered. Suction, advanced airway equipment, and resuscitation medications should be immediately available and in good working order (Table 20-3). A functional defibrillator should be immediately available when deep sedation is administered or when moderate sedation is administered to the patient with cardiovascular disease.1
Appropriate emergency equipment should be available whenever sedative or analgesic drugs capable of causing cardiorespiratory depression are administered. The lists below should be used as a guide, which should be modified depending on the individual practice circumstances. Items in brackets are recommended when infants or children are sedated. Intravenous equipment
Basic airway management equipment
Advanced airway management equipment (for practitioners with intubation skills)
Pharmacologic antagonists
Emergency medications
|
Supplemental oxygen should be considered for moderate sedation and should be administered during deep sedation unless specifically contraindicated for a particular patient or procedure. Supplemental oxygen should be administered if hypoxemia is anticipated or is encountered during sedation/analgesia.
The standards for intraoperative monitoring of patients undergoing procedures under general anesthesia are, for the most part, applicable to the sedation setting.
Oxygenation monitoring is accomplished by pulse oximetry, which is rapid, quantitative, and reliable. It uses a minimum of 2 wavelengths of light to detect concentrations of oxyhemoglobin and deoxyhemoglobin and displays an empirically derived numeric value of percent hemoglobin saturation. When coupled with a variable pitch audio output, this monitor provides a continuous background of information about both the patient’s heart rate and blood oxygenation, and it is one of the essential monitors recommended by ASA during general anesthesia and deep sedation.1,5
Ventilation monitoring is dramatically different between the sedation in the CCL and an in the operating room equipped with the anesthesia machine. Usually the CCL environment lacks the mechanical ventilation devices that monitor tidal volumes, circuit integrity, and airway pressures and analyze inhaled and exhaled gas continuously. However, most modern patient monitors have the capacity for capnogram capture; the use of capnography is recommended by the ASA for all cases where sedation is used, unless precluded or invalidated by the nature of the patient, procedure, or equipment. The capnography unit can be programmed to alert the practitioner in the event that patient’s respiratory rate is too low, indicating the potential for hypoventilation, as well as in case of the total absence of carbon dioxide, which can be caused by apnea, oxygen delivery/sampling line disconnection from the patient, or cardiovascular collapse.
It is a common misconception that pulse oximetry provides enough data to not require capnography; this assumption is quite dangerous because the patient may maintain a normal pulse oximetry profile while being totally apneic for a significant amount of time. Once the hypoxia ensues, sometimes minutes after the cessation of ventilation, the patient will require a much more involved resuscitation and may possibly require positive-pressure ventilation to restore homeostasis. However, if an appropriate intervention, such as airway repositioning, patient stimulation to breathe, or administration of sedative antagonist, is performed at the time of capnography tracing loss, the procedure can usually continue with minimal interruption.
Patients with depressed, but not totally suppressed, ventilation may also display normal pulse oximetry reading but can develop severe hypercarbia and respiratory acidosis, producing symptoms of somnolence, restlessness, or cardiovascular disturbances. If one suspects inadequate ventilation, an arterial blood gas may be necessary to rule out hypoventilation and respiratory acidosis.
Circulation monitoring is accomplished with several modalities; continuous electrocardiography monitoring is recommended for the duration of the procedure because it is reliable, simple, and noninvasive. When used appropriately, it allows a reliable monitoring of cardiac ischemia and will alert to cardiac rhythm disturbances quicker than other monitoring modalities. The most commonly monitored leads are II and V5, which together provide 80% sensitivity for myocardial ischemia. Modern telemetry machines are capable of monitoring 5 or more leads, automatically alerting the provider if ST-segment morphology change is detected.
It is also recommended by the ASA that a blood pressure assessment be performed at least every 5 minutes when using an automated blood pressure cuff or a sphygmomanometer and a stethoscope. For patients with an arterial line in place for blood pressure monitoring or the arterial access for the procedure, it is still recommended to place a noninvasive blood pressure cuff because these require no calibration and thus are not subject to calibration errors. Additionally, arterial lines may fail due to thrombosis or malposition. Meanwhile, arterial sheath pressure transducers may have to be disconnected in the course of the procedure for the transit of catheters or devices; usually, these events are the ones that require more thorough blood pressure monitoring. The blood pressure cuff should fit snugly around the patient’s limb and must be sized appropriately so that the inflatable part covers at least 80% of the limb’s circumference.5
The ASA also made the following statement pertaining to patients undergoing general anesthesia: “[A] secondary circulatory function assessment [should be performed] by at least one of the following: palpation of a pulse, auscultation of heart sounds, monitoring of a tracing of intra-arterial pressure, ultrasound peripheral pulse monitoring, or pulse plethysmography or oximetry for an additional layer of safety.” This may be applicable to deep sedation cases, and this requirement is easily satisfied because CCL patients will commonly have the pulse oximetry data.
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