© Borgis - Nowa Medycyna 2/2017, s. 73-85
Risk assessment and monitoring in an adult patient for analgosedation during colonoscopy
Ocena ryzyka i monitorowanie u dorosłego pacjenta do analgosedacji podczas kolonoskopii
The Department of Anaesthesiology and Intensive Therapy, Saint Anna Traumatology Hospital, Mazovian Rehabilitation Centre „STOCER” Sp. z o.o., Warsaw
Head of Department: Elżbieta Kurmin-Gryz, MD
Analgosedacja to stan obniżonej świadomości pacjenta wywołany podaniem leku lub leków anestetycznych. Celem analgosedacji podczas kolonoskopii jest zapewnienie pacjentowi komfortu i poprawa warunków zabiegu endoskopowego, w szczególności bolesnego zabiegu leczniczego. Ważne jest, aby uświadomić sobie to, że częstość powikłań po endoskopii rośnie wraz z zastosowaniem analgosedacji. Dlatego należy rzetelnie ocenić ryzyko zastosowania analgosedacji przed wykonaniem zabiegu endoskopowego i zastosować odpowiednie monitorowanie pacjenta podczas kolonoskopii. Należy również zapewnić dostępność odpowiednio wyszkolonego zespołu anestezjologicznego i odpowiednio wyposażyć pracownię endoskopową w sprzęt anestezjologiczny. Najlepszym sposobem analgosedacji do kolonoskopii jest zindywidualizowanie analgosedacji dla konkretnego pacjenta uwzględniające: stan kliniczny pacjenta, jego poziom lęku, jak i rodzaj oraz czas trwania planowanego zabiegu kolonoskopowego. Leki anestetyczne używane w analgosedacji tłumią czynność układu nerwowego, układu sercowo-naczyniowego i układu oddechowego, przy czym stopień tłumienia może być dla niektórych pacjentów groźny. Celem pracy jest przedstawienie sposobów zwiększenia bezpieczeństwa pacjentów poddawanych kolonoskopii przez ocenę ryzyka analgosedacji, monitorowanie pacjenta podczas analgosedacji oraz w sali poznieczuleniowej.
Analgosedation is an anaesthetic drug-induced state of reduced consciousness. The purpose of analgosedation in colonoscopy is to increase patient’s comfort and improve endoscopic performance, especially in painful therapeutic procedures. It is important to realise that the rate of endoscopic complications is increased when analgosedation is used. Therefore, a thorough pre-procedural risk evaluation and intra-procedural monitoring of the patient should be performed. Properly trained anaesthesiological team and emergency equipment should be available. The best approach to analgosedation in colonoscopy is to choose a regimen for an individual patient, tailored according to the clinical risk assessment and the anxiety level of the patient, as well as to the type and duration of planned colonoscopy procedure. Agents used for analgosedation suppress central nervous, cardiovascular and respiratory function, and the varying degree of suppression may be fatal in certain patients. The aim of this article is to provide an overview and a brief summary of preanalgosedation risk assessment and patient monitoring during and after analgosedation to maintain patient safety.
Emotional excitation, which derives from CNS, endocrine and sympathetic activity, enhances the perception of pain. Elimination of shock and confusion as well as measures to calm the patient are important elements of treatment. This aspect is particularly important in colonoscopy. Patients usually report in the morning on the day of procedure, they receive no premedication and, following medical history collection and a brief introductory conversation, they undergo colonoscopy. They are usually discharged home several hours later. The current method of colonoscopy uses flexible devices made of elastic glass fibres as a basic optical element. This ensures practically full field of vision, as well as significantly enhances patient comfort during endoscopy and reduces procedure-related complications. Analgosedation may be defined as consciousness suppression induced by an anaesthetic agent(s). A recent survey-based research has shown that in most cases colonoscopy is performed using analgosedation (1-3). Anaesthetic agents used in analgosedation for endoscopy vary depending on the clinical centre. In some centres only one agent is used, whereas in other centres analgesics are combined with anaesthetics. Colonoscopy is most often performed in a patient in left side-lying position. During the examination, patients may change their position to supine or even right side-lying position. Colonoscopy and sigmoidoscopy are the most reliable methods in the diagnosis of colonic and rectal diseases. Indications for colonoscopy are presented in table 1. Administration of analgesics and anaesthetics enhances patient’s tolerance of discomfort and pain, thereby improving diagnostic and therapeutic endoscopic findings (4). Proper analgosedation ensures patient’s comfort and allows for cooperation with the endoscopist. It also allows for the maintenance of defensive airway reflexes and stable spontaneous breathing. This level of analgosedation was defined by the American Society of Anesthesiologists (ASA) as moderate (5) (tab. 2). Although centrally acting analgesics and anaesthetics suppress CNS function in a dose-dependent manner, there is an interindividual variability in the susceptibility to different medications; therefore the level of analgosedation may change rapidly, ranging from minimal sedation to general anaesthesia. Unintentionally deep sedation may impair respiratory and circulatory function, and thus put some patients at danger. The incidence of dangerous cardiovascular and respiratory complications during analgosedation in endoscopic procedures is estimated at 0.54% (6), with mortality rates of 0.05% (7). Patients undergoing elective endoscopic procedures under analgosedation should be subject to a thorough assessment, including medical history and current clinical condition. When monitoring a patient during analgosedation for colonoscopy, attention should be paid to respiratory and cardiovascular instability.
Tab. 1. Indications for colonoscopy
1. faecal occult blood
2. blood in the stool in the absence of evidence for the anal or rectal source of bleeding
3. tarry stools after excluding the source of bleeding in the upper gastrointestinal tract
4. unexplained iron deficiency
5. abnormalities in contrast infusion (contrast filling defect, a narrowing)
6. exclusion of synchronous cancers and polyps in patients with confirmed colorectal polyps and/or cancer
7. chronic diarrhoea of unknown origin
8. selected patients with altered rhythm of bowel movements and an increased risk of colorectal cancer
9. inflammatory bowel diseases if the diagnosis and determination of the extent of lesions affects the procedure
1. polyp removal
2. inhibition of bleeding due to developmental vascular abnormalities
3. foreign body removal
4. decompression of acute bowel subobstruction or torsion
5. dilation of stenosis
6. palliative treatment of inoperable stenosis or tumour bleeding
1. a history of colorectal cancer or adenomatous colon polyps
2. a family history of colorectal cancer not associated with polyposis
3. colorectal cancer in a first-degree relative under the age of 55 years or in more than one family member
4. long-term (more than 7-10 years) history of ulcerative colitis with extensive lesions, with collection of multiple biopsy specimens to detect dysplasia; inflammation limited to the left colon, no need for such intensive supervision
5. colonoscopy in patients over 50 years of age, every 10 years until the age of 70 years or once in lifetime
Tab. 2. American Society of Anesthesiologists classification for sedation
| ||Depth of sedation|
|response assessment||maintained response to verbal instructions||somnolence, maintained response to voice and pain if needed ||asleep, difficult to arouse, maintained response to pain stimulus||unconscious, not arousable, no response to pain stimulus|
|airways||no effects||no intervention is needed||intervention may be needed||intervention is often needed|
|spontaneous respiration||no effects on spontaneous respiration||efficient spontaneous respiration||moderately impaired spontaneous respiration|
|inefficient spontaneous respiration, assisted ventilation is needed|
|cardiovascular function||no effects||usually not impaired||usually not impaired||possible impairment|
Each patient should undergo a preliminary medical history evaluation and physical examination to determine indications and exclude potential contraindications for colonoscopy. Colonoscopy requires appropriate preparation involving bowel cleansing or refraining from consuming meals, which is important for patients with diabetes, cardiovascular insufficiency and renal failure, where modification of recommendations may be necessary. All patients should be informed on the benefits and the risks associated with the proposed procedure, give their oral and written consent for the procedure and receive guidelines on the preparation for the examination. Since a number of anaesthetics used in analgosedation have a narrow safety margin, patients often respond differently to the same anaesthetic doses, which requires increased vigilance when evaluating the general condition of a patient prior to colonoscopy using analgosedation.
Medical history and current health status
Preparation of a patient for sedation and general anaesthesia as well as the risk of general anaesthesia are assessed by an anaesthetist. Patients with comorbidities should be evaluated at appropriate time before the procedure. Medical history evaluation should exclude or confirm significant heart and lung disease, sleep apnoea and snoring, difficult previous intubation, epilepsy or other neurological condition, previous adverse effects of sedation and general anaesthesia, currently used medications, hypersensitivity to medications or food products, alcohol or psychoactive substance abuse, a recent meal within the last 6 hours and ingestion of clear liquid within the last 2 hours, nausea and vomiting suggesting an increased risk of aspiration. Physical examination should assess the state of consciousness, vital functions and body weight; determine the presence of obesity, ascitic fluid, gastrointestinal obstruction and increased abdominal circumference, which increase the risk of pulmonary aspiration. Medical history collection and physical examination should be followed by ASA classification, and the obtained score should be documented in the anaesthesia record. Special attention should be paid to patients with ASA score of 3 and above, Mallampati score of 3 and 4, a history of adverse reactions during sedation, inadequate sedation using standard doses of sedatives, a history of difficult intubation, alcohol and psychoactive substance abuse, sleep apnoea, indications for emergent endoscopy, as well as those undergoing a particularly technically difficult and long-lasting endoscopic procedure.
Antithrombotic and antiplatelet agents
Acetylsalicylic acid used as primary prevention of cardiovascular events should be discontinued 5-7 days before the procedure. For secondary prevention, discontinuation of acetylsalicylic acid (5-7 days before the procedure) as well as clopidogrel and ticlopidine (7-10 days before the procedure) is recommended. Temporary treatment with low molecular weight heparin should be considered in this group of patients. If the patient requires dual antiplatelet therapy, the mode of pre-procedural preparation should be consulted with a cardiologist. Treatment with acenocoumarol and warfarin should be discontinued 4-5 days before the procedure and heparin should be administered (8, 9).
Airway assessment should be based on Mallampati classification (fig. 1) to identify patients at an increased risk of difficult tracheal intubation. The Mallampati score is a four-point scale determining intubation difficulty based on the anatomy of the oral cavity. The distances between the uvula, the fauces and the soft palate are taken into account. High class (Mallampati class IV) indicates potentially difficult intubation. The score was introduced by Mallampati et al. in 1985 (10). This four-point scale includes the following scoring: class 1 – visible soft palate, uvula, pharynx, tonsils; class 2 – visible soft palate and uvula; class 3 – visible soft palate and base of uvula; class 4 – soft palate not visible at all. Other anatomical features may also impede positive inspiratory pressure ventilation and endotracheal intubation and these include obesity, short thick neck, cervical spine diseases, anatomical pathologies of the mouth, mandible and oral cavity, as well as reduced submental- discoid distance. Particular caution should be used in patients with ASA class 3 or above, Mallampati score of 3 and 4, a history of adverse reactions during sedation, inadequate sedation with standard doses of sedatives, a history of difficult intubation, alcohol or psychoactive substance abuse, sleep apnoea, indications for emergent endoscopy, as well as those undergoing a particularly technically difficult and long-lasting endoscopic procedure. It should be noted that some technically difficult colonoscopy procedures may require general anaesthesia with tracheal intubation.
|visible pillars, soft palate and uvula||visible soft palate and uvula||only soft palate visible||soft palate not visible|
Fig. 1. Mallampati classification system
Presedation fasting for colonoscopy
Presedation fasting for colonoscopy is intended to reduce the volume and acidity of stomach contents during colonoscopy, thereby reducing the risk of gastroesophageal reflux and aspiration of gastric contents. A reduction in patient’s airway defence responses increases the risk of pulmonary aspiration. In order to prevent pulmonary aspiration during sedation, appropriate fasting period of at least 2 hours for water, clear juice, tea, black coffee and at least 6 hours for solid foods and milk, should be implemented. However, it may be necessary to prolong the duration of fasting in some patients, particularly in patients with obesity, gastroesophageal reflux and diabetes (11).
Bowel preparation for colonoscopy
The optimal method for colon preparation before colonoscopy should ensure appropriate bowel cleansing, as well as be safe, simple to use, well-tolerated, inexpensive and easily accessible. Also, it should not interfere with endoscopic or histopathological evaluation (12). Nowadays, clinical practice is usually based on preparation schemes using phosphate formulations or isotonic polyethylene glycol (PEG) solution. Phosphates and PEG show comparable efficacy in bowel cleansing, whereas formulations containing sennosides are considered less effective (13). The superiority of PEG over phosphates is primarily seen in its safety profile. Phosphate solutions are more likely to cause water-electrolyte disturbances; therefore their use should be limited in patients with renal insufficiency, heart failure, ascites, and gastrointestinal stenosis. Isosmotic PEG solutions are safer in this regard. They are less likely to cause water-electrolyte disturbances and may be used in patients with the above mentioned conditions. Colon cleansing is of key importance for the quality of colonoscopy. There is no ideal method of preparation. All presented schemes have both advantages and disadvantages. The choice of method should be based on patient’s personal preferences and organisational conditions (the time of day, general anaesthesia).
According to the guidelines of the Polish Society of Anaesthesiology and Intensive Therapy on the principles, conditions and organisation of anaesthesia and intensive therapy services in Poland, the safe use of anaesthetics should be reserved for doctors, i.e. anaesthesiologists and physicians during specialisation in anaesthesiology who work under the direct supervision of an anaesthesiologist (14-16). An anaesthesia team including an anaesthesiologist and a nurse anaesthetist is needed for sedation and general anaesthesia. An anaesthesiologist who performs sedation with monitored anaesthesia or general anaesthesia prepares an anaesthesia protocol, which includes methods used, the type and the dose of pharmacological agents, vital function parameters as well as laboratory findings and potential complications. In the case of complications, they should be systematically analysed and assessed. If the responsibility for anaesthesia is passed to another anaesthesiologist, he or she is obliged to familiarise with all data on the patient’s condition, the course of anaesthesia and the functioning of the equipment. The monitored vital parameters are recorded in the anaesthesia protocol and confirmed with signature of the patient receiving anaesthesia (17, 18). The presence of a specialist anaesthesiologist is necessary for each patient requiring deeper analgosedation, particularly for those with difficulties arising from airway obstruction, e.g. when difficult mask ventilation or problematic tracheal intubation is expected. The direct presence of a specialist anaesthesiologist is also needed for patients with severe comorbidities who undergo endoscopic procedures, as well as ASA class III and IV patients. Intravenous access should be available both before and after sedation, until the risk of cardio-respiratory depression is considered scarce. All sedated patients should be administered oxygen through a nasal catheter at a dose of at least 2 L/minute. After completion of ambulatory endoscopic examination/procedure, the patient should be placed in a wake-up room, under constant medical supervision and appropriate monitoring until reaching the desired level of psychomotor efficiency. Patients can be discharged home only if accompanied by a responsible adult. Patients undergoing endoscopy under analgosedation should refrain from driving or operating machines for 12-24 hours.
Continuous monitoring of heart rate and blood pressure is the basic monitoring during analgosedation. Vital parameter readings should be performed at intervals of at least 5 minutes and the read values should be recorded, with the baseline reading performed before the administration of analgesic and sedative agents (19). Hypertension and tachycardia are often observed when sedation levels appropriate for a given procedure have not been achieved, while hypotension and bradycardia occur during excessive sedation. Blood pressure and heart rate fluctuate in different patients; therefore patient’s responses to pain and vagus nerve reflexes, which have direct effects on patient’s vital parameters, should be closely monitored.
The potential dangers to a patient during analgosedation primarily include hypoxia due to apnoea, airway obstruction, glottis contraction, bronchospasm, reduced respiratory rate below 8 breaths/minute, and gastric aspiration. Every agent used in sedation has depressive effects on the respiratory centre; therefore it is necessary to monitor blood oxygenation in each sedated patient undergoing colonoscopy using pulse oximeter and passive oxygen insufflation. It should be noted that pulse oximeter measures arterial oxygenation rather than oxygen levels in pulmonary vesicles; therefore it does not provide immediate information on respiratory depression (20). For pulse oximeter readings showing decreased arterial oxygenation in a patient receiving passive oxygen insufflation, first a decrease in oxygen levels in pulmonary vesicles, which consequently leads to arterial hypoxia, must occur. In such cases, pulse oximeter will show overstated values even in the case of significant vesicular hypoventilation (21, 22). Capnography is a non-invasive method of monitoring exhaled carbon dioxide levels. Although capnography is not recommended as a component of basic monitoring during sedation for colonoscopy, it may be of help in patients at an increased risk of respiratory depression and those requiring deep sedation.
Passive oxygen insufflation
The use of passive oxygen insufflation as prevention of respiratory depression during sedation for colonoscopy is of great importance for safety during sedation. Since most agents used in sedation for colonoscopy basically have a short duration of action, most respiratory depression events are short-lived (not longer than a few minutes), and endoscope introduction is sufficient for respiratory stimulation (23). Achieving a significant increase in arterial oxygen partial pressure secondary to oxygen enrichment of the inspiratory air inhaled by the patient allows for maintaining arterial oxygenation even during short-term vesicular hypoventilation. Monitoring of patient’s respiratory functions, such as respiratory rate, early airway management as well as the use of assisted ventilation prevents hypoxemia during sedation. In addition to passive oxygen insufflation equipment, endoscopic laboratory where sedation is performed should be equipped with an aspirator, facemasks for mechanical ventilation, airway management devices, a self-expanding bag for mechanical ventilation, laryngoscopes and tracheal tubes, drugs for cardiopulmonary resuscitation, as well as sedative antagonists and narcotic analgesics, such as flumazenil and naloxone.
Monitoring in the post-anaesthesia care unit and a pre-discharge assessment of patient’s condition
The risk of cardiovascular and respiratory complications may still be present in patients after colonoscopy under sedation, depending on the duration of analgesics and sedatives used as well as the general condition of the patient. Discontinuation of external stimulation associated with colonoscopy may induce an unexpected drop in blood pressure and heart rate. Therefore, patient’s vital parameters and consciousness should be monitored in the immediate post-anaesthesia period by trained medical personnel until full recovery and stabilisation of vital parameters are achieved. Post-anaesthesia assessment of patient’s readiness for discharge from the post-anaesthesia unit should include patient’s general condition and the duration of action of agents used for sedation. Post-anaesthesia monitoring should include blood pressure measurements and pulse oximeter readings, which should be continued until patient’s discharge from the post-anaesthesia care unit. Possibly rapid restoration of full body efficiency in a patient subject to analgosedation and general anaesthesia is a specific characteristic of ambulatory analgosedation and general anaesthesia. This requires a careful assessment of the patient’s condition in the immediate period following a diagnostic or therapeutic procedure. There are different qualification and scoring systems to determine patient’s ability to return home. Aldrete score is the most common assessment system used in the post-anaesthesia care unit (24). The score evaluates different respiratory parameters, arterial blood oxygenation, blood pressure, consciousness and activity, which are scored 0 to 2 (tab. 3). Patients scored 8 or more, including 2 points for respiratory functions, are considered ready to be safely discharged from the post-anaesthetic unit. Furthermore, patients should be able to walk unassisted, ingest fluids, experience no significant pain, nausea or vomiting, as well as be accompanied by an adult when returning home after discharge. All patients should be provided with a written instruction explaining the possible complications and how to contact medical personnel in case they occur (25).
Tab. 3. Modified Aldrete Score from 1995
|An assessment of patient’s general condition and psychomotor efficiency||Scores|
|Qualifying patient after procedure for a transfer from the post-anaesthesia unit to the surgical unit||physical activity||able to move 4 extremities voluntarily or on command||2|
|able to move 2 extremities voluntarily or on command||1|
|unable to move extremities voluntarily or on command||0|
|respiration||able to breathe deeply and cough freely||2|
|dyspnoea or limited breath||1|
|blood pressure||blood pressure about 20% of pre-anaesthetic level ||2|
|blood pressure about 20-50% of pre-anaesthetic level||1|
|blood pressure about 50% of pre-anaesthetic level||0|
|arousable on calling||1|
|SpO2||able to maintain > 92% saturation on room air ||2|
|Able to maintain > 90% on room air + O2 supplementation ||1|
|< 90% even with O2 supplementation||0|
Analgosedation and general anaesthesia in colonoscopy are usually indicated in young and healthy patients. An analysis of thousands of cases has demonstrated that analgosedation and general anaesthesia can be also safely performed in elderly patients as well as those with stable comorbidities. However, strict adherence to the principles for periprocedural management is necessary. In addition to patient’s comfort during sedation, safety should be also ensured for successful and safe analgosedation in colonoscopy. An appropriate pre-sedation assessment of patient’s general condition, careful monitoring, individually tailored anaesthetic dose titration depending on patient’s needs, preparation of the medical team for emergency situations requiring immediate intervention in the presence of a trained anaesthesia team are needed. All patients requiring a certain level of analgosedation, which impairs or abolishes defence reflexes, as well as elective general anaesthesia outside of the operating theatre are subject to the same principles and requirements for patient preparation, anaesthesiology equipment, monitoring standards and post-anaesthetic care.
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