nside this issue
- Endoscopic Tattooing
- Conscious Sedation
- Product Highlight - Defendo Single Use Valves
For many years tattooing of the intestinal lumen during endoscopy has been undertaken to optimise surgical intervention of colonic lesions. A simple procedure first introduced circa 1975, tattooing has increased intraoperative laparoscopic surgical accuracy for colorectal lesions to between 70 – 100%.
When lesions are flat or small, they can be hard to see, and nearly impossible to feel at laparoscopic surgery. This makes identifying lesions difficult and prone to error around 11-20% of the time with 6.5% of surgeons saying that they have removed the incorrect part of the bowel on at least one occasion.
This and other complications, such as removing too much or too little colon, having to abandon and reschedule surgery, moving to an open procedure, and longer intraoperative anaesthesia times, can result from failure to identify lesions of the colon laparoscopically.
Endoscopic tattooing is seen as a safe and cost-effective intervention that decreases the adverse occurrences of wrong-site surgery and failure to detect lesions at the time of surgery; 92% of surveyed endoscopists inferred that endoscopic tattooing was the optimal way to communicate lesion location between endoscopy and subsequent laparoscopic surgery.
It is suggested that lesions over 10mm, any lesion that is concerning and lesions that are thought to be incompletely excised, are tattooed.
Initially, Indian ink (coarse carbon molecules suspended in water) was used to tattoo the bowel wall. More recently other compounds such as Indigo carmine, Indocyanine green, and alternatives to tattooing such as placing metal clips, have been used, with varying degrees of success.
Presently the preferred option for endoscopic tattooing (one that will last at least 30 days and give the clearest representation of lesion location) is a very, very fine, highly purified carbon particle in suspension, that is prepared sterile in a ready to use syringe.
Refining the carbon ink particles, providing purification, and bringing to the market in a sterile form has increased the safety profile and decreases the risk involved with endoscopic tattooing.
The biocompatible profile of present-day endoscopic tattooing ink sees it unlikely to cause a reaction in the patient, be it local, systemic or immunological.
Examples of this in New Zealand’s marketplace are Blackeye and Spot.
Optimal placement of the tattoo needle is oblique to the intestinal wall, at an angle of 45 degrees; this allows the needle to enter, but not penetrate the submucosa.
An injection too shallow will see the ink disperse and disappear. Injecting too deep risks puncturing the intestinal wall and injecting transmurally into the peritoneum, potentially creating complications such as focal peritonitis, inflammatory pseudotumor, abscess, idiopathic inflammatory bowel disease, haematomas, bowel infarction, and rarely, mesenteric air embolism.
Additionally, practitioners are mindful of the potential for folds in the colon that can make tattoo detection difficult; it is suggested that tattoo placement is 2 folds away from the lesion site.
Variations of placements exist and can range from being distal and proximal to the lesion, to merely distal to the lesion. And from being a single ink mark to marking circumferentially 2 or 4 quadrants of the lumen.
A bleb is often raised, using saline or ink, and subsequently, ink is injected under the bleb.
These variations on the placement of the tattoo have the potential for miscommunication, and calls have been made to standardise tattoo placement via national guidelines, with the aim to increase detection rates, decrease surgical time, and avoid interventions such as intraoperative colonoscopy: widely known to be difficult, time-consuming, and prone to complications.
In conclusion, you will find endoscopic tattooing deployed in situations involving lesions identified on endoscopy for surgical removal that need marking to enable the subsequent surgical intervention to be as effective as possible.
Lesions that are flat or small, making them difficult to visualise or palpate, can be readily identified at surgery if they are accurately tattooed during the endoscopic procedure. This practice saves time, money, and decreases the risk of increased surgical time, time under anaesthetic and potential complications therein for the patient.
Conscious sedation, also known as moderate sedation is “Drug-induced depression of consciousness during which patients are able to respond purposefully to verbal commands or light tactile stimulation… Interventions to maintain patent airway, spontaneous ventilation or cardiac function may, in exceptional situations, be required…”. Guidelines on Sedation and/or Analgesia for Diagnostic and Interventional Medical, Dental or Surgical Procedures, Australian and New Zealand College of Anaesthetists (ANZCA) 2014.
Comparatively, there are other levels of sedation: light sedation, during which people can respond with mind and body almost as normal, deep sedation, where repeated verbal commands or physical stimulation, possibly pain, are required to elicit a response, and general anaesthesia – where consciousness is lost and no response can be elicited.
Typically gained via a combination of hypnotic (sleep), analgesic, anxiolytic and amnesic medications the aim is that conscious sedation is achieved rapidly, and wears off promptly once the procedure is completed.
Gastrointestinal endoscopy can be anxiety-inducing, uncomfortable, painful, and traumatic for people. This, in turn, can result in the procedure being difficult to perform and the resulting examination suboptimal in terms of diagnostic and therapeutic outcomes.
Conscious sedation diminishes anxiety, induces a degree of muscle and mind relaxation, and minimises pain and discomfort. It also has an amnesic effect; meaning that while a person can “be present”, answer questions and respond to prompts, the effect of the hypnotic/amnesic medication results in much of the procedure being promptly forgotten.
Patients, therefore, experience GI endoscopy in a more positive light, they feel calm, feel minimal discomfort, and their muscles are relaxed and non-resistant. For the practitioner, this results in an optimal examination that is not undermined by patient pain, tension or anxiety.
Additionally, research shows that when conscious sedation is used well patients are more likely to return for follow up or surveillance procedures; clearly very important in regards to bowel screening and ongoing surveillance.
In New Zealand, as with much of the developed world, several types of drugs are used in combination when inducing a state of conscious sedation in a patient:
The benzodiazepine Midazolam (Hypnovel), used either alone or in combination, is the drug most commonly used for conscious sedation in GI endoscopy across the world.
A superior dose to effect time, shorter half-life, superior hypnotic effect, and prompt dose to recovery time are what sees Midazolam the benzodiazepine of choice.
Benzodiazepines are psychoactive drugs that act on the central nervous system – primarily the brain.
The endogenous neurotransmitter gamma-aminobutyric acid (GAMA) supports calmness by decreasing neural excitability (the opposite action of a neurotransmitter such as adrenaline).
By enhancing the activity of GAMA benzodiazepines will induce a sense of calm, muscle relaxation and decreased central nervous system activity: causing sleepiness and a decreased level of consciousness. Memory loss can also result from benzodiazepine intake.
Excessive benzodiazepine levels can cause cardiopulmonary depression, loss of consciousness, deep sedation, and death.
Because of their similar effect on the nervous system substances such as alcohol, opioids and antidepressant medications will increase the action of benzodiazepines and these interactions must be kept to a minimum. Additionally, as benzodiazepines are largely excreted via the liver particular attention needs to be paid to people with liver disease and those taking medications that impair liver function.
Related to ease of access via prescription and the increased feeling of wellbeing that benzodiazepines give, it is a drug that has potential for abuse, addiction and overdose.
Given intravenously Midazolam takes effect within 1-3 minutes, with the peak effect typically reached at 3-5 minutes.
From 20 – 60 minutes after administration the effects will be gone. Interestingly, the half-life of Midazolam is 10 times shorter than Diazepam (Valium); furthering its place as the benzodiazepine of choice.
The incidence of adverse effects is rare: Midazolam remains a safe and effective drug for conscious sedation. Should the effects of Midazolam need to be removed a reversal agent exists: Flumazenil.
By binding to GAMA receptors Flumazenil blocks the uptake of Midazolam, thereby reversing GAMA activation and reverting the neural pathways to normal activity, alertness and muscle tone. As such Flumazenil has the potential to cause agitation and muscle tension; in extreme cases, seizures can result.
Therefore, when administering Flumazenil for Midazolam reversal the same degree of patient monitoring and observation must be implemented with regards to vital signs and level of consciousness, agitation, and possibly reflexes.
We must also remember that in the case of GI endoscopy other CNS depressant medications will have been given in combination with Midazolam.
Fentanyl is a synthetic opioid analgesic medication, first introduced circa 1960. As with other opioids such as Morphine and Pethidine, Fentanyl inhibits the release of the neurotransmitters that recognise painful stimuli. The result is the disturbance of nerve conduction along ascending pathways to the spinal cord and brain: painful stimuli are no longer recognised as pain.
In addition, it affects nociceptors activity, further diminishing the feeling of pain.
Fentanyl is up to eighty times as potent as Morphine, due in large part to the lipophilic nature that sees it readily traverse the blood-brain barrier.
It has a 5-minute dose to effect time and lasts for between 30-60 minutes.
Fentanyl is broken down in the liver and excreted via the kidneys, taking approximately 4 hours to half-life, but just 5 minutes to be eliminated to only 20% of peak dose - a good choice for endoscopy sedation.
Therefore, like all opioids, Fentanyl needs to be administered under controlled conditions with adequate monitoring and resuscitation facilities.
Additionally, because it can cause bronchospasm Fentanyl must be used with caution – or not at all – with people suffering from asthma. Thought is also given to people with poor renal or hepatic function as metabolism and elimination can be delayed.
People with prior substance (especially opioid) use or abuse may be susceptible to Fentanyl and find small doses affect them. Alternately it can also take larger doses to obtain an adequate analgesic effect.
For those with a history of addiction, a discussion must be had regarding the appropriateness of Fentanyl as medication for their GI endoscopic procedure.
The actions of Fentanyl can be reversed: the drug Naloxone must be on hand when Fentanyl is being administered. Acting to mitigate the depressant actions of Fentanyl Naloxone can cause tachycardia, hypertension and a feeling of dis-ease.
It is important to note that the action of Naloxone is shorter than that of Fentanyl, therefore ongoing attention must be paid to level of consciousness and respiratory effort, as more than one dose may be required to reverse the effects of Fentanyl.
In endoscopic sedation Fentanyl, used primarily for its analgesic properties, is most commonly combined with Midazolam.
Propofol is a sedative-hypnotic that is used to promptly induce the conscious sedation common in GI endoscopy. It is popular with doctors, and patient satisfaction is also high; patients report experiencing a feeling of enhanced wellbeing, sometimes euphoria, after Propofol sedation.
Like benzodiazepines (Midazolam) Propofol contributes to the positive modulation of gamma-aminobutyric-acid (GAMA), resulting in depression of consciousness, reduced muscle tone and general relaxation.
There is no analgesic action attributed to Propofol – for this reason it is generally used in combination with Fentanyl for GI endoscopy.
Propofol’s onset of action is prompt, taking effect at 30 seconds and peaking at 2 minutes. Its 4-minute half-life is comparatively short.
These attributes make Propofol an attractive option for the requirements of the short, sharp conscious sedation preferred for GI endoscopic procedures; patient recovery, and time from procedure to return of normal function and discharge is considered optimal.
Additionally, there is no reversal agent for Propofol; it must just wear off in time.
Therefore, while some recent studies internationally are indicating that Propofol sedation administered by a non anaesthetist can be safe and cost effective, many countries, including New Zealand and the United Kingdom, presently require anaesthetists to administer Propofol.
It can be said that Propofol is a popular drug for inducing prompt, short lasting conscious sedation that is positively received by patients. However, it does require close monitoring of the patient’s vital signs due to its potential for inducing unwanted deep sedation in some people.
Medications carry certain risks, including overdose, allergy and adverse effects.
The drugs used to induce conscious sedation all do so by affecting the central nervous system, which in turn affects the cardiopulmonary system, under the control of the autonomic nervous system.
To that end the general risks related to all medications used to induce conscious sedation are similar:
- Respiratory depression
- Potential for allergic reaction
Additionally, blood pressure, pulse rate, rhythm and strength, muscle tone (potentially gag reflex), and signs of pain are assessed.
The hypoxic person will become anxious and restless, sometimes aggravated and combative therefore we should also be observing for a sudden change in demeanour.
These measurements are to be taken at "regular" intervals throughout the sedation and continue during the recovery phase of 45-60 minutes. ANZCA PS18 2017
In order to maintain safety and provide emergency response should issues arise there are also requirements of facilities that perform GI endoscopy under conscious sedation:
- Adequate staffing
- Ensuring that at all times a nurse or anaesthetist is dedicated to the patient: monitoring their level of consciousness, oxygen saturation and airway
- Required equipment
- Resuscitation equipment: oxygen, ventilation equipment (bag and mask) airways, defibrillator
- Emergency plan
- Who to call i.e. external emergency services 111 or internal emergency services e.g. 888 (777) etc
- Physical exit strategies: maintenance of clearways, ambulance access, lift holds.
A full medical, surgical and psychological history should be taken, including medications, previous sensitivities, and allergic reactions.
As medications are generally metabolised and excreted via the renal and hepatic systems any compromise within these systems will affect the action and duration of the medication.
Drug and alcohol use or addiction are important factors to consider, as these can have an impact on the choice of medication used for conscious sedation.
It can also impact on the response the person may have to the medication.
Women of childbearing age must consider whether they are pregnant.
Additionally, sleep apnoea, neuromuscular conditions and previous cerebral trauma are important details to be aware of.
It is important to remember that patients can see several different people throughout the referral, admission and procedure process; therefore it is imperative that all information is well documented and communicated to ensure that all participants in a person’s care have a clear knowledge of the individuals’ situation.
The most common combination in New Zealand presently is Midazolam and Fentanyl for its analgesic and somewhat sedative effects.
Both these medications can be given by a registered nurse on being prescribed by a physician, or by the physician themselves.
Propofol is becoming more popular for use as a short-acting, prompt recovery addition to conscious sedation.
It is appreciated by patients and practitioners alike because it is effective, fast acting, prompt to wear off, and leaves patients feeling good.
However, related to the potential for Propofol to quickly induce deeper sedation than warranted, bringing with it decreased respiratory and cardiac function, in New Zealand, it can only to be administered by an anaesthetist whose sole responsibility is the care of the patient.
Finally, facilities that offer conscious sedation for GI endoscopy must ensure safety in regards to equipment and staffing levels. Clear emergency plans must be maintained and deployable at any given moment.
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