Aneasthesia Pearls September 2014


Ketamine in Anaesthetic Practice

Ketamine is the only anaesthetic available which has analgesic (pain relieving), hypnotic (sleep producing) and amnesic (short term memory loss) effects. When used correctly it is a very useful and versatile drug.
Ketamine is available in three different concentrations 10mg/ml, 50mg/ml and 100mg/ml. 50mg/ml is most commonly stocked since it can be used for i.m. administration or diluted for i.v. use.
Some Practical Usage :
1. IV ketamine for induction and maintenance
For a patient in shock and requires a laparotomy, Ketamine would be an ideal anaesthetic agent due to its cardiovascular effects of raising the blood pressure and heart rate, all other anaesthetic agents tend to have a cardiac depressant effect.
Induction can be performed with iv ketamine (1-2mg/kg), atropine (10-20mcg/kg) and diazepam (0.1mg/kg). It is still possible to perform a modified rapid sequence intubation with ketamine, despite its slower onset time.
There are several options for maintenance :
Intermittent boluses of iv ketamine (0.5mg/kg) given according to patient’s response – pupil size, heart rate, blood pressure, movement etc.
Ketamine infusion. Put 500mg of ketamine in a 500ml bag of saline or dextrose. Run this at 1-2mls/min (1-2mg/min). Some patients may require more and others less depending on what other drugs have been given and the type of surgery.
Generally the ketamine will need to be discontinued 20-30 minutes before the end of the operation to avoid a long wait for the patient to wake up.
This technique for laparotomy is best used with non-depolarising muscle relaxants (avoid pancuronium as it may cause hypertension when combined with ketamine).
2. Use of i.m. ketamine
If the child is clearly going to be uncooperative and either i.v. access or gas induction will be difficult, in these circumstances intramuscular ketamine is very useful.
There are two possible options :
Induce anaesthesia with i.m. ketamine (5-10mg/kg) + atropine (20mcg/kg) + diazepam (0.1mg/kg) these may all be mixed in the same syringe. Onset of anaesthesia will start about 5 minutes after injection. The disadvantage of this technique is that it requires a relatively large i.m. injection. While most textbooks quote 8-10mg/kg for induction a much smaller dose (5mg/kg) is sufficient.
Sedate with i.m. ketamine (2mg/kg) + atropine (20mcg/kg) + diazepam (0.1mg/kg). After 5 minutes you will have a docile child who can cooperate with either cannulations or a gas induction.
In either case iv access should then be obtained. If iv access is impossible then anaesthesia can be maintained with i.m. ketamine (3-5mg/kg).
3. Oral ketamine sedation
For burns dressings IV ketamine can be tried but in burns patients there are often limited sites for cannulation and these are best saved for trips to theatre. IM ketamine is also an option but requires relatively large painful i.m. injections. Instead the intravenous preparation of ketamine can be given orally.
For an adult give 500mg of ketamine + diazepam 5mg.
For a child use 15mg/kg ketamine + 0.2mg/kg diazepam (the i.v. preparation may be used, but it has an offensive tastes and may have to be concealed in juice).
The dressing change can usually start after 20-30 minutes. Responses can sometimes be unpredictable and onset time may be slower. There should always be equipment for suction and face mask ventilation available and if possible, oxygen and a pulse oximeter.
4. Ketamine for perioperative analgesia
A. Intravenous Ketamine as an Analgesic Adjunct to General Anesthesia
Intravenous subanesthetic ketamine, when added as an adjunct to general anesthesia, reduced postoperative pain and opioid requirements in a variety of settings, from outpatient surgery to major abdominal procedures.
However, some studies did not show this benefit. Two factors may explain these failures. First, beneficial effects of ketamine may be masked when the drug is used in small doses (˂ 0.15 mg/kg) against the background of multimodal or epidural analgesia. Second, the dosing schedule may be inadequate. Studies have compared the effects of ketamine administration before surgery with those of one ketamine administration at the end of surgery to test its “preemptive” analgesic properties. However, nociceptive and inflammatory signals are generated throughout surgery and after the procedure. A single injection of a short-acting drug such as ketamine either before or after incision will therefore not provide analgesia that lasts far into the postoperative period. To prevent pathologic pain, ketamine needs to be applied at least throughout the operation and likely for a period of time into the postoperative phase, in an attempt to reduce sensitization of central and peripheral pain pathways. Thus, the adequacy of the ketamine administration schedule is a crucial component for pain prevention.(Fig 1)
Figure 1
For prevention of pathologic pain after severe tissue injury, ketamine administration should cover the entire duration of high-intensity noxious and inflammatory stimulation, not simply the initial trauma.
Proposal for use of Intravenous Ketamine as Analgesic Adjuvant to General Anaesthesia and PCA
Ketamine Procedure Procedure
Before Incision During Surgery After Surgery
Racemic Painful e.g. Major Visceral Surgery 0.50mg/kg Infusion: 500µg/kg/h or Bolus: 0.25mg/kg, repeated at 30min intervals. If procedure ≥ 2h, stop use 60 min before end of surgery. Background infusion: 120 µ/kg/h for 24 h, then 60µ/kg/h for 48 h (or longer as necessary) and opioid based PCA.
Racemic Less Painful e.g. Hip Surgery 0.25mg/kg Infusion: 250µg/kg/h or Bolus: 0.125mg/kg, repeated at 30min intervals. PCA, Bolus: 1mg ketamine and 1mg morphine
S(+) Painful e.g. Major Visceral Surgery 0.35mg/kg Infusion: 400µg/kg/h or Bolus: 0.2mg/kg, repeated at 30min intervals. If procedure ≥ 2h, stop use 30 min before end of surgery. Background infusion: 85 µ/kg/h for 24 h, then 60µ/kg/h for 48 h (or longer as necessary) and opioid based PCA. Or PCA only, Bolus: 0.5mg S(+) ketamine and 1mg morphine
S(+) Less Painful e.g. Lumbar Spine Surgery 0.25mg/kg Infusion: 200µg/kg/h or Bolus: 0.1mg/kg, repeated at 30min intervals. PCA , Bolus: 0.25mg S(+) ketamine and 1.5mg morphine
Note: Ketamine is a racemic mixture consisting of two enantiomers, R- and S-ketamine. In contrast to ketamine, S-ketamine is reported to be less prone to psychomimetic side effects, such as derealisation and hallucinations.
B. Ketamine as an Analgesic Adjunct to Regional Anesthesia and Analgesia
The addition of ketamine to a local anesthetic or other analgesics in peripheral or neuraxial anesthesia and analgesia improves or prolongs pain relief. A decrease in drug-related side effects (sedation, pruritus, or adverse psychological reactions) has also been found, mainly because the required drug doses could be reduced. These effects may relate to blockade of central and peripheral NMDA receptors and/or an antinociceptive action complementary to that of the other drugs used.
Studies assessing caudal ketamine have shown efficient analgesia for both intraoperative and postoperative periods. Racemic ketamine provided improved pain relief of prolonged duration when added to local anesthetics and 0.5–1 mg/kg S(+) ketamine produced analgesia when administered alone or in combination with other anesthetics.
5. Use of Ketamine for patients with chronic pain
Many patients with amputations or patients with spinal cord injuries have problems with chronic pain. The nature of this pain is often neuropathic (this means originating from an injury to the nerves) and has an unpleasant burning or shooting quality to it. When traditional first line treatments for neuropathic pain such as amitriptyline or carbamazepine have failed ketamine may also be added and has been shown to have success.
A standard dosing regimen for an adult is 50mg orally (use the intravenous preparation) three times per day. This may be increased to 100mg tds. Problems with hallucinations and salivation are rare. The ketamine may be discontinued after about 3 weeks of good pain control, reducing the dose gradually to see if any pain symptoms reoccur. The authors have found this regime useful in postoperative amputation patients to try and prevent the onset of phantom limb pain. In this setting it seems the ketamine need only to be taken for about a week.
6. Ketamine for the treatment of asthma
Ketamine is an effective bronchodilator and can be used for the patient who is not responding to conventional bronchodilators such as salbutamol and aminophylline. The doses of ketamine required are very low and problems with hallucinations rare. A loading dose of 0.2 mg/kg iv is given initially followed by an infusion of 0.5mg/kg/hr for 3 hours. This may be continued if necessary. Close monitoring of the patient is required and an anaesthetist should be available if necessary.
References :
1. Rachael Craven, Ketamine in Anaesthetic Practice. Anaesthesia UK.
2. Sabine Himmelseher, Ketamine for Perioperative Pain Management. Anesthesiology 2005; 102:211–20.
3. Paul R, Comparison of racemic ketamine and S-ketamine in treatment-resistant major depression: report of two cases. World J Biol Psychiatry. 2009;10(3):241-4.

ACC/AHA Guideline

2014 ACC/AHA Guideline
2014 ACC/AHA Guideline on Perioperative Cardiovascular Evaluation and Management of Patients Undergoing Noncardiac Surgery
Classification of Recommendations :
Class I: Conditions for which there is evidence and/or general agreement that a given procedure or treatment is useful and effective.
Class II: Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment.
IIa: Weight of evidence/opinion is in favor of usefulness/efficacy
IIb: Usefulness/efficacy is less well established by evidence/opinion.
Class III: Conditions for which there is evidence and/or general agreement that the procedure/treatment is not useful/effective, and in some cases may be harmful.
Level of Evidence
Level of Evidence A Data derived from multiple randomized clinical trials
Level of Evidence B Data derived from a single randomized trial, or non-randomized studies
Level of Evidence C Consensus opinion of experts
Note: A recommendation with Level of Evidence B or C does not imply that the recommendation is weak. Many important key clinical questions addressed in the guidelines do not lend themselves to clinical trials. Although randomized trials are unavailable, there may be a very clear clinical consensus that a particular test or therapy is useful or effective.
Stepwise Approach to Perioperative Cardiac Assessment for CAD :
GDMT-Guideline Determined Medical Therapy, ACS- Acute Coronary Syndrome, MACE- major adverse cardiac event, MET- metabolic equivalent, NB- No Benefit, CPG- clinical practice guideline, HF- heart failure, VHD- valvular heart disease, STEMI- ST-elevation myocardial infarction, UA/NSTEMI- unstable angina/non–ST-elevation myocardial infarction.
Step 1: In patients scheduled for surgery with risk factors for or known CAD, determine the urgency of surgery. If an emergency, then determine the clinical risk factors that may influence perioperative management and proceed to surgery with appropriate monitoring and management strategies based on the clinical assessment.
Step 2: If the surgery is urgent or elective, determine if the patient has an ACS. If yes, then refer patient for cardiology evaluation and management according to GDMT according to the UA/NSTEMI and STEMI CPGs
Step 3: If the patient has risk factors for stable CAD, then estimate the perioperative risk of MACE on the basis of the combined clinical/surgical risk.
Step 4: If the patient has a low risk of MACE (<1%) , then no further testing is needed, and the patient may proceed to surgery.
Step 5: If the patient is at elevated risk of MACE, then determine functional capacity with an objective measure or scale such as the DASI (Duke Activity Status Index). If the patient has moderate, good, or excellent functional capacity (≥4 METs), then proceed to surgery without further evaluation.
Step 6: If the patient has poor (<4 METs) or unknown functional capacity, then the clinician should consult with the patient and perioperative team to determine whether further testing will impact patient decision making (e.g., decision to perform original surgery or willingness to undergo CABG or PCI, depending on the results of the test) or perioperative care. If yes, then pharmacological stress testing is appropriate. In those patients with unknown functional capacity, exercise stress testing may be reasonable to perform. If the stress test is abnormal, consider coronary angiography and revascularization depending on the extent of the abnormal test. The patient can then proceed to surgery with GDMT or consider alternative strategies, such as noninvasive treatment of the indication for surgery (e.g., radiation therapy for cancer) or palliation. If the test is normal, proceed to surgery according to GDMT.
Step 7: If testing will not impact decision making or care, then proceed to surgery according to GDMT or consider alternative strategies, such as noninvasive treatment of the indication for surgery (e.g., radiation therapy for cancer) or palliation.
Summary of Recommendations for Supplemental Preoperative Evaluation:
Recommendations COR LOE
The 12-lead ECG

Preoperative resting 12-lead ECG is reasonable for patients with known coronary heart disease or other significant structural heart disease, except for low-risk surgery


Preoperative resting 12-lead ECG may be considered for asymptomatic patients, except for low-risk surgery


Routine preoperative resting 12-lead ECG is not useful for asymptomatic patients undergoing low-risk surgical procedures

III: No Benefit B
Assessment of LV function

It is reasonable for patients with dyspnea of unknown origin to undergo preoperative evaluation of LV function


It is reasonable for patients with HF with worsening dyspnea or other change in clinical status to undergo preoperative evaluation of LV function


Reassessment of LV function in clinically stable patients may be considered

Routine preoperative evaluation of LV function is not recommended III: No Benefit B
Exercise stress testing for myocardial ischemia and functional capacity

For patients with elevated risk and excellent functional capacity, it is reasonable to forgo further exercise testing and proceed to surgery


For patients with elevated risk and unknown functional capacity it may be reasonable to perform exercise testing to assess for functional capacity if it will change management


For patients with elevated risk and moderate to good functional capacity, it may be reasonable to forgo further exercise testing and proceed to surgery


For patients with elevated risk and poor or unknown functional capacity it may be reasonable to perform exercise testing with cardiac imaging to assess for myocardial ischemia


Routine screening with noninvasive stress testing is not useful for low-risk noncardiac surgery

III: No Benefit B
Cardiopulmonary exercise testing

Cardiopulmonary exercise testing may be considered for patients undergoing elevated risk procedures

Noninvasive pharmacological stress testing before noncardiac surgery

It is reasonable for patients at elevated risk for noncardiac surgery with poor functional capacity to undergo either DSE or MPI if it will change management


Routine screening with noninvasive stress testing is not useful for low-risk noncardiac surgery

III: No Benefit B
Preoperative coronary angiography

Routine preoperative coronary angiography is not recommended

III: No Benefit C
Definitions of Urgency and Risk:
An emergency procedure is one in which life or limb is threatened if not in the operating room where there is time for no or very limited or minimal clinical evaluation, typically within <6 hours.
An urgent procedure is one in which there may be time for a limited clinical evaluation, usually when life or limb is threatened if not in the operating room, typically between 6 and 24 hours.
A time-sensitive procedure is one in which a delay of >1 to 6 weeks to allow for an evaluation and significant changes in management will negatively affect outcome. Most oncologic procedures would fall into this category.
An elective procedure is one in which the procedure could be delayed for up to 1 year.
A low-risk procedure is one in which the combined surgical and patient characteristics predict a risk of a major adverse cardiac event (MACE) of death or myocardial infarction (MI) of <1%. Selected examples of low-risk procedures include cataract and plastic surgery.
Procedures with a risk of MACE of ≥1% are considered elevated risk.
Proposed Algorithm for Antiplatelet Management in Patients With PCI and Noncardiac Surgery:
ASA indicates aspirin; ASAP, as soon as possible; BMS, bare-metal stent; DAPT, dual antiplatelet therapy; DES, drugeluting stent; and PCI, percutaneous coronary intervention.
Summary of Recommendations for Perioperative Therapy:
Recommendations COR LOE
Coronary revascularization before noncardiac surgery

Revascularization before noncardiac surgery is recommended when indicated by existing CPGs


Coronary revascularization is not recommended before noncardiac surgery exclusively to reduce perioperative cardiac events.

III: No Benefit B
Timing of elective noncardiac surgery in patients with previous PCI

Noncardiac surgery should be delayed after PCI

I C: 14 d after balloon angioplasty B: 30 d after BMS implantation

Noncardiac surgery should be delayed 365 d after DES implantation


A consensus decision as to the relative risks of discontinuation or continuation of antiplatelet therapy can be useful


Elective noncardiac surgery after DES implantation may be considered after 180 d

IIb* B

Elective noncardiac surgery should not be performed in patients in whom DAPT will need to be discontinued perioperatively within 30 d after BMS implantation or within 12 mo after DES implantation

III: Harm B

Elective noncardiac surgery should not be performed within 14 d of balloon angioplasty in patients in whom aspirin will need to be discontinued perioperatively

III: Harm C
Perioperative beta-blocker therapy

Continue beta blockers in patients who are on beta blockers chronically


Guide management of beta blockers after surgery by clinical circumstances


In patients with intermediate- or high-risk preoperative tests, it may be reasonable to begin beta blockers


In patients with ≥3 RCRI factors, it may be reasonable to begin beta blockers before surgery


Initiating beta blockers in the perioperative setting as an approach to reduce perioperative risk is of uncertain benefit in those with a long-term indication but no other RCRI risk factors.


It may be reasonable to begin perioperative beta blockers long enough in advance to assess safety and tolerability, preferably >1 d before surgery.


Beta-blocker therapy should not be started on the d of surgery

III: Harm B SR†
Perioperative statin therapy

Continue statins in patients currently taking statins


Perioperative initiation of statin use is reasonable in patients undergoing vascular surgery


Perioperative initiation of statins may be considered in patients with a clinical risk factor who are undergoing elevated-risk procedures

Alpha-2 agonists

Alpha-2 agonists are not recommended for prevention of cardiac events

III: No Benefit B
ACE inhibitors

Continuation of ACE inhibitors or ARBs is reasonable perioperatively


If ACE inhibitors or ARBs are held before surgery, it is reasonable to restart as soon as clinically feasible postoperatively

Antiplatelet agents

Continue DAPT in patients undergoing urgent noncardiac surgery during the first 4 to 6 wk after BMS or DES implantation, unless the risk of bleeding outweighs the benefit of stent thrombosis prevention.


In patients with stents undergoing surgery that requires discontinuation P2Y12 inhibitors, continue aspirin and restart the P2Y12 platelet receptor–inhibitor as soon as possible after surgery.


Management of perioperative antiplatelet therapy should be determined by consensus of treating clinicians and the patient.


In patients undergoing nonemergency/nonurgent noncardiac surgery without prior coronary stenting, it may be reasonable to continue aspirin when the risk of increased cardiac events outweighs the risk of increased bleeding.


Initiation or continuation of aspirin is not beneficial in patients undergoing elective noncardiac noncarotid surgery who have not had previous coronary stenting.

III: No Benefit B C: If risk of ischemic events outweighs risk of surgical bleeding
Perioperative management of patients with CIEDs

Patients with ICDs should be on a cardiac monitor continuously during the entire period of inactivation, and external defibrillation equipment should be available. Ensure that ICDs are reprogrammed to active therapy.

ACE indicates angiotensin-converting-enzyme; ARB, angiotensin-receptor blocker; BMS, bare-metal stent; CIED,cardiovascular implantable electronic device; COR, Class of Recommendation; CPG, clinical practice guideline; DAPT, dual antiplatelet therapy; DES, drug-eluting stent; ERC, Evidence Review Committee; ICD, implantable cardioverterdefibrillator;LOE, Level of Evidence; N/A, not applicable; PCI, percutaneous coronary intervention; RCRI, Revised Cardiac Risk Index; and SR, systematic review.
Summary of Recommendations for Anesthetic Consideration and Intraoperative Management:
Recommendations COR LOE
Volatile general anesthesia versus total intravenous anesthesia

Use of either a volatile anesthetic agent or total intravenous anesthesia is reasonable for patients undergoing noncardiac surgery

Perioperative pain management

Neuraxial anesthesia for postoperative pain relief can be effective to reduce MI in patients undergoing abdominal aortic surgery


Preoperative epidural analgesia may be considered to decrease the incidence of preoperative cardiac events in patients with hip fracture

Prophylactic intraoperative nitroglycerin

Prophylactic intravenous nitroglycerin is not effective in reducing myocardial ischemia in patients undergoing noncardiac surgery

III: No Benefit B
Intraoperative monitoring techniques

Emergency use of perioperative TEE in patients with hemodynamic instability is reasonable in patients undergoing noncardiac surgery if expertise is readily available


Routine use of intraoperative TEE during noncardiac surgery is not Recommended.

III: No Benefit C
Maintenance of body temperature

Maintenance of normothermia may be reasonable to reduce perioperative cardiac events

Hemodynamic assist devices

Use of hemodynamic assist devices may be considered when urgent or emergency noncardiac surgery is required in the setting of acute severe cardiac dysfunction

Perioperative use of pulmonary artery catheters

The use of pulmonary artery catheterization may be considered when underlying medical conditions that significantly affect hemodynamics cannot be corrected before surgery


Routine use of pulmonary artery catheterization is not recommended

III: No Benefit A
COR indicates Class of Recommendation; LOE, Level of Evidence; MI, myocardial infarction; N/A, not applicable; and TEE, transesophageal echocardiogram.
Source :
Lee A. Fleisher, MD, 2014 ACC/AHA Guideline on Perioperative Cardiovascular Evaluation and Management of Patients Undergoing Noncardiac Surgery. J Am Coll Cardiol. 2014;():. doi:10.1016/j.jacc.2014.07.944


The “i-scoop” – a new type of laryngoscope for normal and difficult airways
Modern videolaryngoscopes have not been able to replace conventional laryngoscope, and all current videolaryngoscopes still have a blade to elevate the tongue base and the epiglottis.
In direct laryngoscopy, the blade helps to align the oral, pharyngeal and tracheal axes to allow a direct view of the glottis and it also keeps the oral and pharyngeal cavity open to enable direct tracheal intubation. Videolaryngoscopes do not have to align these axes to the same extent, as the glottis is not seen directly but indirectly via lenses. However, when videolaryngoscopy has to overcome markedly curved anatomy in difficult airways with high bending angles, the glottis may not be visible, even after applying increased and fairly invasive lifting forces. In these very difficult airways, the blade itself prevents optimal positioning of the lenses close to the vocal cords, and thus prevents achievement of the necessary viewing angle for seeing the glottis.
Videolaryngoscopes can make intubation of even normal airways difficult, despite a good view of the glottis. These difficulties are mainly due to a lack of experience, or may occur when a malleable stylet is not optimally shaped to reach and to pass the visible glottis. In emergency situations, not less than one in four intubations fails at the first attempt with standard laryngoscopy, and at least one in five intubations still fails initially, even with videolaryngoscopes. These and other difficulties with current standards necessitate the consideration of alternative techniques for laryngoscopy and intubation that differ substantially from the original approaches.
Figure 1
The i-scoop is an intubation device with a curved guiding bar with laterally located lenses at its tip, rather than a blade.
The intubation-scoop (i-scoop) enables tracheal intubation with a fundamentally different technique compared to standard laryngoscopes, as it does not comprise a blade to elevate the tongue base or the epiglottis. The device consists of a handle and a curved guiding bar with two cameras.
Figure 2
Figure 2 : The i-scoop follows the natural  shape of the airways without lifting the tongue base. The optimal viewing angle of the first camera from below (left arrow) enables a clear view on the glottis (*). The second camera (right arrow) monitors the epiglottis (†) when the tube (‡) is guided on the guiding bar into the trachea.
The first camera at the distal and lateral end of the guiding bar is placed beneath the epiglottis resulting in an optimal viewing angle from below up to the glottis. The clear view of the vocal cords is not disturbed by any elements of the device, the tongue base, the epiglottis or the tracheal tube. The second camera monitors the distal end of the guiding bar and a surrounding area identifying the epiglottis or other obstacles when the tube is guided to the glottis. The shape of the guiding bar corresponds to the shape of the upper airways so the outlet angle of the guiding bar is in line with the tracheal axis, which should allow the tube to be introduced easily into the trachea.
A functional prototype has been produced. The device has been tested extensively on various airway trainer manikins and was found to be superior to all current video laryngoscopy systems with regard to intubation success rate, intubation time and visibility of the vocal cords.
European and US patent applications (EP12729515.2; US14/125,724) have been filed with priority of 2011.
Further Reading :
1. Raymondos K: The i-scoop: a laryngoscope with new perspectives. Anaesthesia 2012 Jan;67(1):78.
2. K. Raymondos, The intubation scoop (i-scoop) – a new type of laryngoscope for difficult and normal airways. Anaesthesia, Volume 69, Issue 9, pages 990–1001, September 2014.

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