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Premedication
CLINICAL ANAESTHESIA
Premedication
Learning objectives
James Palmer After reading this article, you should be able to: C describe a range of different types of premedication, including sedative and analgesic C know when premedication is indicated and what drug or intervention would be most appropriate C indicate the dose range
Abstract Premedication is any drug or therapy administered before surgery. In the past this has mainly been used for the control of autonomic responses to anaesthetic agents, and for facilitating gas induction when this was the norm. Premedication declined from being almost universal until the 1980s to a much lower level today. The decline has been associated with a change in the type of premedication from sedative and antisialagogue to analgesia, anti-reflux and other diverse agents aimed at optimizing the patient’s peri-operative state.
surgery increased the need for faster street fitness meaning that within a few years premedication almost vanished from all but a few areas of practice and in all but a few specific situations.
Keywords Anaesthesia; analgesia; antacid; antisialagogue; anxiolysis; premedication; sedative; thrombo-embolism
Modern premedication
Royal College of Anaesthetists CPD Matrix: 1A02, 2A03, 1D02.
The classification of modern premedication is based on the action of the drugs used and is broadly divided into four categories: continuation of current medications analgesia prokinetic/antacid/antiemetic anxiolytic other.
Historical perspective Early inhalational agents such as chloroform and ether were associated with undesirable autonomic sequelae including bradyarrythmias and hypersalivation, which could be prevented by the use of antisialagogue vagolytic agents such as atropine or hysocine. Induction was also protracted and relatively unpleasant which made a sedative agent useful, and to some extent hysocine and opiates ameliorated this. The minimal availability of intravenous access and limited variety of opiates encouraged the use of long acting intramuscular opiates (OmnoponÒ or pethidine) before transfer to theatre. Before this other agents had been used, including oral barbital or techniques such as the one employed by George Crile’s team in the Cleveland Clinic. Crile used an approach he called ‘stealing the thyroid’ where a patient with uncontrolled thyrotoxicosis, admitted well before the planned date of surgery was kept ignorant of the actual date of operation but received daily preparation for surgery including an enema. On the day of surgery the enema contained a hypnotic (initially probably oil-ether, subsequently tribromoethanol (AvertinÒ) or phenobarbital) which created a stable sedated state, avoiding haemodynamic crises during the induction process. The 1970s brought the new and relatively safe benzodiazepines, so that oral sedative premedication became the norm, commonly prescribed with an antiemetic such as metoclopramide. Modern anaesthetic agents avoided many of the side effects of the past and relatively painless intravenous cannulation made intravenous induction the norm, while the availability of a range of intravenous opiates such as fentanyl and alfentanil obviated the need for preoperative opiate administration. However, the introduction of day of surgery admission and the rise of day
Continuation of current medications Part of the preoperative assessment, whether that by the anaesthetist on the day of surgery or in a dedicated preoperative assessment clinic, is to decide which elements of patient medication should be continued and which stopped. With the exception of antiplatelet medication, which is mainly discontinued for 10 days before surgery, and warfarin and other anticoagulants which are universally stopped, replaced with low molecular weight heparin, or markedly reduced to attain a target international normalized ratio (INR) specific to that surgical procedure, the majority of pre-operative medication is continued. Cardiac medications should be universally continued. Preexisting b-blockers (as opposed to those started intraoperatively) have been shown to reduce peri-operative mortality, and although there is evidence that angiotensin-converting enzyme (ACE) blockers or inhibitors taken on the day of surgery contribute to increased intraoperative hypotension, this has not been associated with any postoperative sequelae and given the benefit that these agents provide, it is probably better in most cases to continue them since the side effect is easily managed. The question of whether or not to withhold diuretic therapy can be addressed by looking at the type of diuretic; long-term thiazides have little diuretic effect and are mainly vasodilatory in action, whereas loop diuretics on the day of surgery may increase fasting induced hypovolaemia and increase the need for a urinary catheter. Bronchodilators should be continued, and any concerns about inhaler technique can be met by the use of nebulized solutions immediately before surgery. These may also help reduce perioperative wheeze and coughing in smokers, a group who may also exhibit higher levels of anxiety due to smoking cessation in the run up to surgery and the use of nicotine patches in these patients may also be of benefit.
James Palmer FRCA is a Consultant Anaesthetist at Salford Royal NHS Foundation Trust, Salford, UK. Conflicts of interest: none declared.
ANAESTHESIA AND INTENSIVE CARE MEDICINE --:-
1
Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Palmer J, Premedication, Anaesthesia and intensive care medicine (2015), http://dx.doi.org/10.1016/ j.mpaic.2015.08.004
CLINICAL ANAESTHESIA
Subcutaneous insulin was discontinued and replaced with a ‘sliding scale’ of a fast-acting insulin, but modern practice is to continue basal long-acting insulin and to add short-acting insulin and dextrose by infusion only for patients who will be fasting postoperatively.
may increase risk (neurosurgery, head and neck surgery, cardiac surgery), where there is a suspicious history or when major blood loss is anticipated. Renal function e in patients with impaired renal function the dose of any NSAID should be reduced. In patients with an estimated glomerular filtration rate (eGFR) of less than 20 ml/minute they should be withheld. Other concerns e the effects of COX1 drugs on bone healing are a concern often raised as an argument against their use in orthopaedic internal fixation surgery. There are currently no human trials to support this view and the most often quoted paper relates to rabbits.
Analgesic premedication During the 1990s and into the 21st century there was considerable research interest in pre-emptive analgesia; the theory being that depriving nociceptive receptors of input during surgery would reduce postoperative pain to a greater extent than the same dose of drugs postoperatively. While this idea has not been universally accepted, it is a view generally held that oral preoperative analgesic medication or ‘prophylactic analgesia’ will at least ensure that a balanced multimodal analgesic regimen is underway during surgery and on emergence. This technique has the additional appeal of simplicity, cost saving, avoidance of parenteral drug administration error, and reduction in anaphylaxis risk.
Gabapentin: gabapentin whose main use is in chronic pain can be a useful adjunct in some circumstances. Although its side effects include postoperative drowsiness, this is acceptable in situations where pre-existing pain states make postoperative pain control likely to be more problematic and patients on gabapentin (or pregabalin) should continue these drugs into the postoperative period. A single dose of 300 mg of gabapentin is usual; higher doses may slow recovery unacceptably in those who have not taken it before.
Paracetamol: paracetamol addresses minor postoperative pain, reduces postoperative opiate requirements in more major surgery, and helps postoperative headache which can be a troublesome side effect after sevoflurane anaesthesia. Its antipyretic effect is also useful in some patients. Adult
Child
Clonidine: clonidine in a dose of 2e4 mg/kg can be used in children as an analgesic and anxiolytic agent.
>70 kg 2 g orally at least 30 minutes before planned surgery <70 kg 1 g orally 20 mg/kg orally (40 mg/kg rectally)
Local anaesthetics: local anaesthetic creams (EMLAÒ or AmetopÒ) can be used not only to reduce the pain of cannulation in children and anxious adults, but also to reduce pain from graft donor sites and grommets. Benzocaine lozenges can help prepare the patient in advance of awake fibreoptic intubation, and co-phenylcaine nasal spray is useful prior to transphenoidal pituitary surgery, and any nasal or sinus surgery.
Non-steroidal anti-inflammatory drugs (NSAIDs) address moderate levels of postoperative pain and reduce post-operative opiate requirements. They are divided into two main groups: COX1 and COX2. Choice of agent rests upon a number of factors, some of which (local policy) may be out of the control of the individual anaesthetist, but it is prudent to consider the following before choosing a specific drug or dose. Patient tolerance e some patients may find that they tolerate one COX1 drug much better than another. It is not unusual to find that a patient refuses diclofenac but prefers ibuprofen for selftreatment. Not all patients with asthma are intolerant of COX1 NSAIDs and most have used at least one on previous occasions. If this has been uneventful, problems are unlikely, but should bronchospasm result, the patient is at least in the best possible place! Gastric symptoms following a prolonged course of a COX1 NSAID should also not be off-putting. A single dose of an entericcoated agent, possibly in combination with a gastro-protectant, is appropriate. Oral COX2 drugs are well tolerated, but rarely available for this indication. Efficacy of that agent in trials e the number needed to treat (NNT) for various agents and doses has been established in several reviews and for adults diclofenac 50e100 mg, ibuprofen 400 mg (5e10 mg/kg in children), or naproxen 500 mg have NNTs between 1.8 and 2.7. Effects of COX1 agents on platelet function e this effect should be considered carefully in patients where occult bleeding
ANAESTHESIA AND INTENSIVE CARE MEDICINE --:-
Prokinetic, antacid and antiemetic drugs Although not efficacious as an antiemetic when used as a premedicant, metoclopramide (adult dose 10 mg orally) is an effective way to reduce gastric volume and to increase lower oesophageal sphincter tone. When it is used in conjunction with an antacid such as sodium citrate (15 ml orally) an H2 antagonist such as ranitidine (150 mg orally), or a proton pump inhibitor (PPI) such as omeprazole (20 mg orally), gastric volume and acidity are reduced which minimizes the risk of regurgitation/ aspiration; the aim is to raise pH above 2.5 and decrease gastric content to less than 25 ml. An H2 antagonist or PPI can also be given with a COX1 NSAID if there is concern about gastric irritation. Hyoscine, used in the past as an antisialagogue, is now mainly used in patch form (one patch per 72 hours) applied near the mastoid process in patients at high risk of postoperative nausea and vomiting, particularly in labyrinthine or posterior fossa surgery. Anxiolytics This is the group of drugs that are most commonly associated with the word ‘premed’ in the minds of both the public and many ward staff. Although studies have demonstrated that information and preoperative discussion with an anaesthetist are as effective
2
Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Palmer J, Premedication, Anaesthesia and intensive care medicine (2015), http://dx.doi.org/10.1016/ j.mpaic.2015.08.004
CLINICAL ANAESTHESIA
For patients with bronchiectasis or before major abdominal or chest surgery preoperative chest physiotherapy is of benefit but will require a level of coordination with other services often hard to achieve in a modern hospital. Following NICE guidance in 2008, oral antibiotic prophylaxis is no longer recommended. Xylometazoline (OtrivineÒ) used prior to sinus, intranasal or pituitary surgery, or if nasal intubation is planned will help decongest the nose and reduce bleeding. A
as standard doses of benzodiazepines, these are still requested by some patients. The most common drug prescribed to adults is temazepam in a dose of 10e20 mg, although lorazepam 2 mg can be selected for a more profound and lengthy effect. In children midazolam syrup (0.5 mg/kg orally or 0.2 g/kg intranasally) is used. Other Although not usually prescribed by anaesthetists, and normally part of a preoperative ‘package’ for venous thrombo-embolism prevention, almost all patients are now issued with compressive stockings before surgery.
ANAESTHESIA AND INTENSIVE CARE MEDICINE --:-
3
Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Palmer J, Premedication, Anaesthesia and intensive care medicine (2015), http://dx.doi.org/10.1016/ j.mpaic.2015.08.004
Premedication
Learning objectives
James Palmer After reading this article, you should be able to: C describe a range of different types of premedication, including sedative and analgesic C know when premedication is indicated and what drug or intervention would be most appropriate C indicate the dose range
Abstract Premedication is any drug or therapy administered before surgery. In the past this has mainly been used for the control of autonomic responses to anaesthetic agents, and for facilitating gas induction when this was the norm. Premedication declined from being almost universal until the 1980s to a much lower level today. The decline has been associated with a change in the type of premedication from sedative and antisialagogue to analgesia, anti-reflux and other diverse agents aimed at optimizing the patient’s peri-operative state.
surgery increased the need for faster street fitness meaning that within a few years premedication almost vanished from all but a few areas of practice and in all but a few specific situations.
Keywords Anaesthesia; analgesia; antacid; antisialagogue; anxiolysis; premedication; sedative; thrombo-embolism
Modern premedication
Royal College of Anaesthetists CPD Matrix: 1A02, 2A03, 1D02.
The classification of modern premedication is based on the action of the drugs used and is broadly divided into four categories: continuation of current medications analgesia prokinetic/antacid/antiemetic anxiolytic other.
Historical perspective Early inhalational agents such as chloroform and ether were associated with undesirable autonomic sequelae including bradyarrythmias and hypersalivation, which could be prevented by the use of antisialagogue vagolytic agents such as atropine or hysocine. Induction was also protracted and relatively unpleasant which made a sedative agent useful, and to some extent hysocine and opiates ameliorated this. The minimal availability of intravenous access and limited variety of opiates encouraged the use of long acting intramuscular opiates (OmnoponÒ or pethidine) before transfer to theatre. Before this other agents had been used, including oral barbital or techniques such as the one employed by George Crile’s team in the Cleveland Clinic. Crile used an approach he called ‘stealing the thyroid’ where a patient with uncontrolled thyrotoxicosis, admitted well before the planned date of surgery was kept ignorant of the actual date of operation but received daily preparation for surgery including an enema. On the day of surgery the enema contained a hypnotic (initially probably oil-ether, subsequently tribromoethanol (AvertinÒ) or phenobarbital) which created a stable sedated state, avoiding haemodynamic crises during the induction process. The 1970s brought the new and relatively safe benzodiazepines, so that oral sedative premedication became the norm, commonly prescribed with an antiemetic such as metoclopramide. Modern anaesthetic agents avoided many of the side effects of the past and relatively painless intravenous cannulation made intravenous induction the norm, while the availability of a range of intravenous opiates such as fentanyl and alfentanil obviated the need for preoperative opiate administration. However, the introduction of day of surgery admission and the rise of day
Continuation of current medications Part of the preoperative assessment, whether that by the anaesthetist on the day of surgery or in a dedicated preoperative assessment clinic, is to decide which elements of patient medication should be continued and which stopped. With the exception of antiplatelet medication, which is mainly discontinued for 10 days before surgery, and warfarin and other anticoagulants which are universally stopped, replaced with low molecular weight heparin, or markedly reduced to attain a target international normalized ratio (INR) specific to that surgical procedure, the majority of pre-operative medication is continued. Cardiac medications should be universally continued. Preexisting b-blockers (as opposed to those started intraoperatively) have been shown to reduce peri-operative mortality, and although there is evidence that angiotensin-converting enzyme (ACE) blockers or inhibitors taken on the day of surgery contribute to increased intraoperative hypotension, this has not been associated with any postoperative sequelae and given the benefit that these agents provide, it is probably better in most cases to continue them since the side effect is easily managed. The question of whether or not to withhold diuretic therapy can be addressed by looking at the type of diuretic; long-term thiazides have little diuretic effect and are mainly vasodilatory in action, whereas loop diuretics on the day of surgery may increase fasting induced hypovolaemia and increase the need for a urinary catheter. Bronchodilators should be continued, and any concerns about inhaler technique can be met by the use of nebulized solutions immediately before surgery. These may also help reduce perioperative wheeze and coughing in smokers, a group who may also exhibit higher levels of anxiety due to smoking cessation in the run up to surgery and the use of nicotine patches in these patients may also be of benefit.
James Palmer FRCA is a Consultant Anaesthetist at Salford Royal NHS Foundation Trust, Salford, UK. Conflicts of interest: none declared.
ANAESTHESIA AND INTENSIVE CARE MEDICINE --:-
1
Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Palmer J, Premedication, Anaesthesia and intensive care medicine (2015), http://dx.doi.org/10.1016/ j.mpaic.2015.08.004
CLINICAL ANAESTHESIA
Subcutaneous insulin was discontinued and replaced with a ‘sliding scale’ of a fast-acting insulin, but modern practice is to continue basal long-acting insulin and to add short-acting insulin and dextrose by infusion only for patients who will be fasting postoperatively.
may increase risk (neurosurgery, head and neck surgery, cardiac surgery), where there is a suspicious history or when major blood loss is anticipated. Renal function e in patients with impaired renal function the dose of any NSAID should be reduced. In patients with an estimated glomerular filtration rate (eGFR) of less than 20 ml/minute they should be withheld. Other concerns e the effects of COX1 drugs on bone healing are a concern often raised as an argument against their use in orthopaedic internal fixation surgery. There are currently no human trials to support this view and the most often quoted paper relates to rabbits.
Analgesic premedication During the 1990s and into the 21st century there was considerable research interest in pre-emptive analgesia; the theory being that depriving nociceptive receptors of input during surgery would reduce postoperative pain to a greater extent than the same dose of drugs postoperatively. While this idea has not been universally accepted, it is a view generally held that oral preoperative analgesic medication or ‘prophylactic analgesia’ will at least ensure that a balanced multimodal analgesic regimen is underway during surgery and on emergence. This technique has the additional appeal of simplicity, cost saving, avoidance of parenteral drug administration error, and reduction in anaphylaxis risk.
Gabapentin: gabapentin whose main use is in chronic pain can be a useful adjunct in some circumstances. Although its side effects include postoperative drowsiness, this is acceptable in situations where pre-existing pain states make postoperative pain control likely to be more problematic and patients on gabapentin (or pregabalin) should continue these drugs into the postoperative period. A single dose of 300 mg of gabapentin is usual; higher doses may slow recovery unacceptably in those who have not taken it before.
Paracetamol: paracetamol addresses minor postoperative pain, reduces postoperative opiate requirements in more major surgery, and helps postoperative headache which can be a troublesome side effect after sevoflurane anaesthesia. Its antipyretic effect is also useful in some patients. Adult
Child
Clonidine: clonidine in a dose of 2e4 mg/kg can be used in children as an analgesic and anxiolytic agent.
>70 kg 2 g orally at least 30 minutes before planned surgery <70 kg 1 g orally 20 mg/kg orally (40 mg/kg rectally)
Local anaesthetics: local anaesthetic creams (EMLAÒ or AmetopÒ) can be used not only to reduce the pain of cannulation in children and anxious adults, but also to reduce pain from graft donor sites and grommets. Benzocaine lozenges can help prepare the patient in advance of awake fibreoptic intubation, and co-phenylcaine nasal spray is useful prior to transphenoidal pituitary surgery, and any nasal or sinus surgery.
Non-steroidal anti-inflammatory drugs (NSAIDs) address moderate levels of postoperative pain and reduce post-operative opiate requirements. They are divided into two main groups: COX1 and COX2. Choice of agent rests upon a number of factors, some of which (local policy) may be out of the control of the individual anaesthetist, but it is prudent to consider the following before choosing a specific drug or dose. Patient tolerance e some patients may find that they tolerate one COX1 drug much better than another. It is not unusual to find that a patient refuses diclofenac but prefers ibuprofen for selftreatment. Not all patients with asthma are intolerant of COX1 NSAIDs and most have used at least one on previous occasions. If this has been uneventful, problems are unlikely, but should bronchospasm result, the patient is at least in the best possible place! Gastric symptoms following a prolonged course of a COX1 NSAID should also not be off-putting. A single dose of an entericcoated agent, possibly in combination with a gastro-protectant, is appropriate. Oral COX2 drugs are well tolerated, but rarely available for this indication. Efficacy of that agent in trials e the number needed to treat (NNT) for various agents and doses has been established in several reviews and for adults diclofenac 50e100 mg, ibuprofen 400 mg (5e10 mg/kg in children), or naproxen 500 mg have NNTs between 1.8 and 2.7. Effects of COX1 agents on platelet function e this effect should be considered carefully in patients where occult bleeding
ANAESTHESIA AND INTENSIVE CARE MEDICINE --:-
Prokinetic, antacid and antiemetic drugs Although not efficacious as an antiemetic when used as a premedicant, metoclopramide (adult dose 10 mg orally) is an effective way to reduce gastric volume and to increase lower oesophageal sphincter tone. When it is used in conjunction with an antacid such as sodium citrate (15 ml orally) an H2 antagonist such as ranitidine (150 mg orally), or a proton pump inhibitor (PPI) such as omeprazole (20 mg orally), gastric volume and acidity are reduced which minimizes the risk of regurgitation/ aspiration; the aim is to raise pH above 2.5 and decrease gastric content to less than 25 ml. An H2 antagonist or PPI can also be given with a COX1 NSAID if there is concern about gastric irritation. Hyoscine, used in the past as an antisialagogue, is now mainly used in patch form (one patch per 72 hours) applied near the mastoid process in patients at high risk of postoperative nausea and vomiting, particularly in labyrinthine or posterior fossa surgery. Anxiolytics This is the group of drugs that are most commonly associated with the word ‘premed’ in the minds of both the public and many ward staff. Although studies have demonstrated that information and preoperative discussion with an anaesthetist are as effective
2
Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Palmer J, Premedication, Anaesthesia and intensive care medicine (2015), http://dx.doi.org/10.1016/ j.mpaic.2015.08.004
CLINICAL ANAESTHESIA
For patients with bronchiectasis or before major abdominal or chest surgery preoperative chest physiotherapy is of benefit but will require a level of coordination with other services often hard to achieve in a modern hospital. Following NICE guidance in 2008, oral antibiotic prophylaxis is no longer recommended. Xylometazoline (OtrivineÒ) used prior to sinus, intranasal or pituitary surgery, or if nasal intubation is planned will help decongest the nose and reduce bleeding. A
as standard doses of benzodiazepines, these are still requested by some patients. The most common drug prescribed to adults is temazepam in a dose of 10e20 mg, although lorazepam 2 mg can be selected for a more profound and lengthy effect. In children midazolam syrup (0.5 mg/kg orally or 0.2 g/kg intranasally) is used. Other Although not usually prescribed by anaesthetists, and normally part of a preoperative ‘package’ for venous thrombo-embolism prevention, almost all patients are now issued with compressive stockings before surgery.
ANAESTHESIA AND INTENSIVE CARE MEDICINE --:-
3
Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Palmer J, Premedication, Anaesthesia and intensive care medicine (2015), http://dx.doi.org/10.1016/ j.mpaic.2015.08.004