Colonoscopies are relatively safe endoscope procedures which are currently performed on a routine basis due to their low invasiveness and increasing diagnostic and therapeutic opportunities. It has been demonstrated that colonoscopies may influence the respiratory and circulatory systems which is significant in case of patients with diseases of these systems (1-3). The risk of the occurrence of complications in these patients is increased as a result of the application of moderate and deep sedation. Adequate anaesthesiological supervision ensures a high level of patient safety during diagnostic or therapeutic procedures. Appropriate monitoring of the patient’s condition allows for early detection of changes of the organism functions. The anaesthetist physician may react quickly and effectively cope with disorders which are dangerous for the patient, such as hypoxia, hypertension, blood pressure drops, arrhythmia. Sedation and analgesia performed by the anaesthetist increase the patient’s comfort and improves the working conditions of the specialist performing endoscopy. Most of the risk factors for complications of sedation are factors related to the patients themselves. The frequency of occurrence of complications of sedation is relatively low. The risk factors include: age higher than 60, additional morbidity assessed in the ASA scale, the patient’s hospitalization and a colonoscopy procedure performed by an inexperienced physician (4, 5). The application of sedatives and analgesics may potentially lead to the occurrence of dangerous complications. The most frequent adverse effects caused by these medications are: obstruction of the upper respiratory tract, respiratory depression, circulatory depression, allergic reactions. Sedation improves the conditions for performing colonoscopy. The application of too high doses of medications, synergistic action of the administered medications, an individual reaction of a particular patient to the administered medication – all these factors may cause a sudden thereat to the patient’s safety if the sedation and analgesia are performed by a person who does not possess adequate knowledge and skills. Due to the fact that sedation and analgesia seem to be simple procedures, their simplicity may result in ignoring the safety rules and cause life-threatening complications. Complications of sedation for colonoscopy are usually transient and their intensity is mild. Significant complications may be avoided thanks to performing a careful assessment the patient before initiating the sedation, ensuring adequate preparation for sedation, selecting of appropriate monitoring and support of the functions of the respiratory and circulatory systems as well as proper procedure in the direct post-recovery period.

All the patients who are to be sedated should provide an updated medical case record, results of additional examinations depending on the comorbidities and they should undergo a physical examination. It is necessary to document selected risk factors such as the presence of sleep apnoea, abuse of alcohol and psychoactive substances, allergies to sedative medications and the possibility for the extension of the duration of colonoscopy. Every patient should be assessed using the ASA scale (6). The taken medical history should be directed at respiratory and circulatory problems and allergies. Before commencing the colonoscopy procedure it is necessary to obtain the patient’s informed consent for the colonoscopy and the sedation related to it. The physician obtaining the patient’s informed consent for the colonoscopy and the sedation related to it should be familiar with the latest guidelines for sedation, he or she should take the patient’s history in the scope of the patient’s comorbidities and the medications taken by the patient in the period preceding colonoscopy, the physician should also identify risk factors in inpatients and outpatients (7, 8). Moreover the physician has to be familiar with the rules of procedure in case of complications of sedation. Such complications include respiratory depression and the reduction of the oxygenation of arterial blood caused by the application of sedative medications. Maintaining the safety of sedation and monitoring are part of ensuring the quality of sedation in endoscope rooms.

The majority of complications related to sedation applied for colonoscopy take place during the performing of this medical procedure. The standard monitoring during the colonoscopy procedure includes measurements of arterial blood pressure performed using a non-invasive method, measurements of the heart rate, of the oxygenation of arterial blood, the electrocardiographic examination. This monitoring is routinely continued in the post-anaesthesia care unit. After the procedure the patient should not experience any pain, nausea nor vomiting, especially an outpatient. Post-procedure ailments such as pain, nausea and vomiting are not observed frequently even after therapeutic colonoscopies. Effective and safe analgesics in patients after colonoscopy are opioids and non-steroidal anti-inflammatory drugs. Patients after sedation leave the post-anaesthesia care unit after meeting the criteria for discharge to go home. Usually patients meet these criteria for the readiness for discharge to go home after the elapse of 1 hour from the finishing of sedation for colonoscopy (9). That is why patients after sedation should remain in the post-anaesthesia care unit for at least 30-60 minutes before they are discharged to go home. The types of complications in the recovery period after sedation are the same as in the period of performing the sedation. Patients in case of whom a benzodiazepine and an opioid were used for the sedation should be monitored in the post-anaesthesia care unit longer than other patients. If recovering a patient from sedation was achieved using medications reversing the effects of medications used for the sedation then the recovery period should last for at least 2 hours from the administration of the medication reversing the effects of the sedative medication. While applying sedation for colonoscopy in case of outpatients the physician should aim at ensuring that the patient recovers full consciousness in the shortest possible time after the procedure. Clinical and electronic monitoring should be ensured until the moment the patient completely recovers consciousness and full contact. Sedation may be considered finished when there has been a complete recovery of consciousness confirmed by logical contact with the patient and when simultaneously the circulatory and respiratory parameters are correct and the psychophysical efficiency allows for independent movement. The residual effects of medications applied for sedation may maintain for many hours from the finishing of the sedation and therefore a patient after minimal sedation may go home on the condition that he or she is taken care of by an accompanying responsible adult person. The patient should also be advised, at best in the form of a written manual, that for the period of 24 hours he or she is not allowed to drive a car, control heavy machines, drink alcohol nor sign binding civil law contracts. The minimum general criteria which are considered to allow for a patient’s discharge to go home are: the stability of basic vital parameters assessed for an hour; the patient’s orientation in reference to him- or herself, the time and place; the absence of post-procedure complications including bleeding; the ability to walk independently; the ability of fluid intake; lack of nausea or its slight intensity; the ability to urinate; enduring pain after taking oral non-opioid analgesics. The decision regarding a patient’s readiness to be discharged to go home is made by the physician after performing the above assessment.

Flumazenil is a benzodiazepine which has got a competitive antagonist effect on the benzodiazepine receptor. It safely reverses the effects of other benzodiazepines. The affinity of flumazenil for the receptor is the highest of all ligands. According to the principle of competitive antagonism it displaces ligands from connections (bindings) in the receptor and this way it stops their action. The effect is reversible blocking of the receptor. The recommended initial dose is 0.2 mg administered intravenously over 15 seconds. If the expected return of consciousness is not obtained within 60 seconds from the administration of the initial dose a further dose of 0.1 mg may be administered intravenously. This procedure (the intravenous administration of a further dose of 0.1 mg) is repeated at 60-second intervals until obtaining an adequate level of consciousness or up to a total dose of 1.0 mg. The duration of action of the medication is about 1 hour (10). Flumazenil is not recommended for routine application. The administration of flumazenil for the purpose of antagonizing the effects of benzodiazepines is always associated with the risk of the occurrence of resedation. It’s beginning may occur already after the elapse of 1 hour from the administration if the antagonist. The phenomenon of resedation depends mainly on the difference in the duration of the half-life of flumazenil and the half-life of benzodiazepines and also on the ratio of the dose of the agonist to the dose of the antagonist as well as on the difference in the time elapsing from the administration of the last dose of the agonist to the administration of the antagonist. In every case of resedation the administration of an additional dose of flumazenil effectively removes the resedation symptoms. Similarly as in case of the procedure after the application of naloxone, it is necessary to monitor patients for at least 2 hours from the administration of flumazenil in order to exclude resedation after flumazenil ceases to act. The adverse effects of flumazenil are: sweating, reddening of skin, nausea and vomiting, hiccup, agitation, visual disturbances, paraesthesia and convulsions.

Due to its chemical structure, naloxone belongs to the group of opioids. Thanks to this it is able to displace a substance which is structurally similar from the target receptor and – as a pure antagonist – reverse the action of the opioid: respiratory depression, narrowing of pupils, hypotension, sedation (10). The action of naloxone starts in 2 minutes after intravenous administration, slightly later after intramuscular or subcutaneous administration. The duration of action of naloxone depends on the dose and on the administration method – after intramuscular administration it is longer than after intravenous administration. Adults: usually 100-200 μg (i.e. 1.5-3 μg/kg of body weight) via intravenous injection. In some cases, especially when an opioid medication with a long duration of action has been applied it may be necessary to administer an additional dose of naloxone intramuscularly in the period of 1-2 h up to a total dose of 2 mg. Children: intravenously 10 μg/kg of body weight; in case of need it is possible to administer an additional dose of 100 μg/kg of body weight. Due to the fact that naloxone is quickly removed from the brain, it demonstrates short duration of action which – after the administration of a single dose – is only 30-45 minutes. The patient has to be monitored for at least 2 hours after the administration of naloxone in order to avoid resedation. The adverse effects of naloxone are opioid resedation, nausea and vomiting, hypertension, tachycardia, pulmonary edema and arrhythmias.

Cardiopulmonary complications are responsible for 50% of serious complications and about 50% of perioperative mortality related to endoscope procedures. In many cases these complications are the direct or indirect consequence of elderly age and comorbidities in patients who were subjected to too deep sedation (12).