Ask the Expert11

BUPIVACANE and ADRENALINE IN SPINAL ANAESTHESIA
In the early 1990s, when bupivacaine was not commonly available in India, we used to prolong the Lignocaine spinal anaesthetic duration by rinsing the syringe with Adrenaline. We had used this combination in hundreds of cases without any problem.

By reviewing the literature, it is found that 0.2 to 0.4 mg adrenaline can be safely added to prolong the spinal bupivacaine. It is claimed to prolong the sensory analgesic duration by 40 to 50%. The fear of causing intense vasoconstriction and spinal cord ischaemia is unfound. The animal studies had proved that spinal adrenaline doesn’t cause cord ischaemia to that extent of causing neuronal damage. But we don’t know the amount of added adrenaline in rinsing the syringe. And this technique has lost popularity after the free availability of epidural catheters. The sodium meta-bisulphite in some of the adrenaline preparations is found to be safe when given intrathecally in minute quantity. But now preservative free adrenaline is available in the market.

Prof.Dr.R.Selvakumar

Ref: Regional anaesthesia in the patient with pre-existing neurologic dysfunction.-Terese .T.Horlocker , Mayo clinic, Minnesota.
Prof. Dr.R.Selvakumar

Some additional facts about parabens:

Metabolism of parabens results in the formation of PABA derivatives which are potentially allergic products. Often the allergic incidences following amide local anaesthetics are blamed due to its preservatives (parabens) and may be true also. But animal studies and human volunteer studies show that parabens( methyl,ethyl,butyl and propyl) are relatively safe additives. They have been approved by the FDA as standard preservative agents as an anti-microbial agent in many foodstuffs, cosmetics and dermatological preparations (with a safe limit of less than 0.1%). They have not demonstrated any untoward reactions with parabens except some contact dermatitis.

If accidental injection of multi dose local anaesthetic agent with paraben in to the thecal sac occurs after an attempted epidural (Total Spinal), the nervous tissue is exposed to the parabens. Even though there is a theoretical possibility of neurotoxicity is there, there is no direct conclusive evidence for the same. It is proved that Rabbit vagus nerve incubation with 0.1% methyl paraben suppresses nerve excitability in a dose dependant manner but does not destroy nervous tissue. Even then FDA did not approve preservative containing local anaesthetic being used in epidural and caudal anaesthesia.

Dr.R.Selvakumar

Sugammadex Is Unique:

• First product that can reverse a profound` neuromuscular block
• Can provide immediate reversal when required
• Avoids the need to use acetylcholinesterase inhibitors (AChEIs) and muscarinic antagonists Proposed Indication

Sugammadex is indicated in adults for:

• Routine reversal of shallow and profound neuromuscular blockade induced by rocuronium or vecuronium
• Immediate reversal of neuromuscular blockade at 3 minutes after administration of rocuronium.

Dosing Recommendations
The recommended dose of sugammadex depends on the level of neuromuscular blockade to be reversed

Routine Reversal

• A dose of 2.0 mg/kg is only recommended if spontaneous recovery has occurred up to the reappearance of T2 (shallow blockade) following rocuronium or vecuronium induced blockade.
• A dose of 4.0 mg/kg is recommended if recovery has reached 1-2 post-tetanic counts (PTC) (profound blockade) following rocuronium or vecuronium induced blockade.

Immediate Reversal

• A dose of 16.0 mg/kg is recommended 3 minutes following the administration of rocuronium
  (There are no data to support the use of sugammadex for immediate reversal following vecuronium induced blockade)

Mechanism of Action
Sugammadex rapidly encapsulates rocuronium and vecuronium .
Sugammadex is inactive against non-steroidal neuromuscular blocking agents, like succinylcholine and Cisatracurium.

Conclusion

• Sugammadex has been shown to be safe and efficacious in more than 2000 administrations in patients and volunteers
• Its properties are expected to lead to safety benefits for patients
• Sugammadex will become a valuable new drug in the management of neuromuscular blockade specifically and general anesthesia, overall.

FDA Approval Status
Monday, September 23, 2013

On September 23, Merck Inc. announced it had received a Complete Response Letter from the U.S. Food and Drug Administration (FDA) informing the company that its resubmitted New Drug Application for sugammadex had been rejected. According to Merck, the FDA raised issues with \\\”operational aspects of a hypersensitivity study\\\” that the FDA had requested in 2008.

ASA had previously expressed strong support for the approval of sugammadex in a formal comment letter to the FDA’s Anesthetic and Analgesic Drug Products Advisory Committee.

Conservation of mass applies but is not necessary to compute equilibrium conditions.

No matter what the starting concentrations of gases in the circuit, the circuit concentration will head toward and eventually reach the concentration of the net flow of gases into the breathing circuit. Net flow is fresh gas flow minus uptake.

FGF is comprised of individual flows of oxygen, nitrous oxide, air and vapor Uptake includes oxygen consumption, nitrous oxide uptake, nitrogen uptake and vapor uptake.

Oxygen uptake is 200 ml, nitrogen is 0 and nitrous oxide is 100ml/min. carbon dioxide is taken care by circuit design.

In practice we have high flow or low flow and air-oxygen or nitrousoxide-oxygen or a combination.

33% oxygen with 66% air gives just above 50% FiO2hence 50% FiO2 is considered safe for low flow anaesthesia.

When used with nitrous oxide, 65-70% nitrous oxide is required to get required anaesthetic benefits of the agent. Hence 33% oxygen may be appropriate. At higher the flow lower FiO2 can be used but as we go for low flow higher FiO2 should be used.

Suggested reading:TOTALLY CLOSED CIRCUIT NITROUSOXIDE/OXYGEN ANAESTHESIA.F.BARTONANDJ.F.NUNN. Br.J.Anaesth.(1975),47,350

Dr. Prasanta Kumar Dash.

Controversies:
It should be remembered that some clinical tests show extremely low specificity and sensitivity. Lifting and holding the head for 5 sec, lifting and holding the leg for 5 sec, handshake for 5 sec and the resistance test on sticking the tongue are considered the best tests to assess the muscular strength. The clinical tests widely used, such as sticking the tongue, opening of eyes or assessment of expiration by feeling the endotracheal tube air flow on the examiner’s hand are unreliable.
Assessments of neuromuscular conduction using clinical tests do not fully concur with the results obtained using objective methods, e.g. acceleromyometry.
When to Use a Peripheral Nerve Stimulator:
In my opinion and those of others, good evidence-based practice dictates that clinicians should always quantitate the extent of neuromuscular recovery by objective monitoring. At a minimum, the TOF ratio should be measured during recovery whenever a nondepolarizing neuromuscular block is not antagonized. (Miller)
Two types of stimulation are used to assess the residual action of relaxants: TOF and double burst stimulation (DBS). Since there are only two responses to DBS (stronger than in TOF), their assessment is slightly easier. Instrumental methods of neuromuscular conduction monitoring using e.g. accelerometry are so accurate and objective that there is no need to use DBS; thus, TOF stimulation

Ref: 1. Kopman P, Yee PS, Neuman GG: Relationship of the train-of-four fade ratio to clinical signs and symptoms of residual paralysis in awake volunteers. Anesthesiology 1997; 86: 765�771.
2. Tomasz Gaszynski, Lukasz Szlachcinski, Jakub Jakubiak, Wojciech Gaszynski. Reversal from non-depolarising neuromuscular blockade in the postoperative period. Anaesthesiology Intensive Therapy, 2009,XLI,1; 9-12
3. Neuromuscular Monitoring. J�rgen Viby-Mogensen. Miller’s Anesthesia. 7th edition.

Ref: Monica Morosan, Anaesthesia and common oral and maxillo-facial emergencies.
Contin Educ Anaesth Crit Care Pain (2012) 12 (5): 257-262.
http://ceaccp.oxfordjournals.org/content/12/5/257.full

For “Oral and Maxillofacial Regional Anesthesia”

Ref: Benaifer D. Oral and Maxillofacial Regional Anesthesia.
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Test dose with 3 ml of 1.5% Lignocaine with Adrenaline should be done through the catheter. Absence of heart rate increase more than 10 per minute within 10 seconds of test dose administration rules out intravascular placement of epidural catheter. After successful test dosing, the initial dose can be given with 10 � 12 ml of 1.5% Lignocaine with adrenaline (if adrenaline is not contra-indicated). Approximately 1.5 � 2 ml of local anaesthetic solution will be needed per segment to be blocked. I prefer to use Lignocaine as the first dose because of its short onset of action and reduced toxicity.br/>
After confirming the block take-up, we can sedate the patient to make him comfortable. But, a fall of B.P is inevitable as most of the sympathetic fibres are blocked. As the surgeon enters in to the abdomen, patient may complain vague abdominal discomfort or frank pain on handling the stomach or omentum. This is due to the unblocked vagal fibres conducting some afferent sensation. To alleviate this, surgeon can infiltrate 4 ml of 2% Lignocaine on either side of lower end of oesophagus. The top-up can be done after 1 hour with 4 � 6 ml of 0.25% Bupivacaine . Fentanyl in a dose of 2�g/ ml of local anaesthetic can be added. Post-operative analgesia can be continued with Ropivacaine 0.2% 4 � 6 ml / hour along with 1-2 �g fentanyl/ml of local anaesthetic for 24 to 48 hours.

But personally I feel, lone epidural anaesthesia may not be an ideal anaesthetic technique for an exploratory laparotomy .The exaggerated and inevitable B.P fall, uncomfortable patient because of unblocked vagus, intact sensation in the under surface of the diaphragm and moderate abdominal relaxation make epidural as the 2nd choice for the proposed surgery after G.A.

I used to tell my P.Gs, Regional anaesthesia for upper abdominal surgery is like travelling in the bus sitting in a lady’s seat. Sometime you may complete the journey without being disturbed. Even if you are not disturbed, you will be tensed up in all the bus stops to see any lady coming towards your seat. Likewise lone epidural anaesthesia may make you and your patient uncomfortable in all stages and may force you to sedate him heavily, losing the advantage of regional Epidural is a nice technique when it is combined with G.A for upper abdominal

Dr.R.Selvakumar

• • Arteritis
  • Takayasu’s pulseless aortitis
  • Cervical rib syndrome
  • Thoracic outlet syndrome
  • Scalenusanticus syndrome
  • Brachial/axillary artery occlusion
  • Subclavian steal syndrome
  • Reflex sympathetic dystrophy

As you have excluded intracardiac pathology by echocardiography, embolic cause is very unlikely.
Anaesthetic implications will be guided by the diagnosis
If no aetiology is found standard care is all that needed

Dr. Prasanta Kumar Dash

To be frank, I had used this drug only as an epidural adjuvant in the dose of 150µg(2 – 3 µg/kg). But when I enquired in Trichy where I’m working, I came to know that many Anaesthesiologists use intra-thecal Buprenorphine routinely along with Bupivacaine. They use 60 -90µg along with bupivacaine and claim no side effects.

But when I enquired in detail, they couldn’t provide finer details of quality of analgesia and occurrence of side effects. Since they don’t receive any compliant calls from the hospital where they use intra-thecal buprenorphine, they are in a opinion that it is trouble free. They are claiming duration of 36 hours post-operative analgesia.

But some other Anaesthesiologists who had used it, stopped now as there was severe itching, nuchal rigidity and urinary retention in some patients.They got an analgesic period of around 12 hours.

I conclude that it’s better not to use this drug routinely as an intra-thecal additive as there are better alternative drugs.

DR.R. SELVAKUMAR.
Professor of Anaesthesiology
K.A.P.Viswanatham Govt Medical College, Trichy

Further Reading:
1.A comparative study of intrathecal and epidural buprenorphine using combined spinal-epidural technique for caesarean section
2.Spinal buprenorphine for postoperative analgesia after caesarean section
3. Comparison of intrathecal morphine and buprenorphine for postoperative analgesia in cesarean delivery
4. Buprenorphine significantly prolongs postoperative analgesia in intravenous regional anesthesia: a double blind randomized clinical trial – See more at:

1) Tug Maneuver: Tug maneuver that I have described is where LMA is inserted till you can push no more and then retracted out gently till you feel there is something holding it back, which is back of the tongue which opposes against the LMA cuff. Perfect alignment of LMA with glottis generally helps.

2) Jaw thrust: It always helps to decrease leak but you will have to keep the jaw thrust all throughout.

3) Side to side movement of the thyroid cartilage helps to displace epiglottis that might be impinging on the grille and causing obstruction and leak.

Dr.Pankaj Kundra.

In children, bradycardia may occur, but hypoxemia must always be considered as the primary cause.

In healthy patients these responses are generally well tolerated; however, in patients with limited coronary or myocardial reserve, myocardial ischemia or failure may follow. The patient with a vascular lesion at risk such as an intracranial vascular anomaly or trauma of the thoracic aorta may also suffer serious sequelae.

The clinician must be careful so as not to over treat these responses and create more difficulties than the responses themselves. Because the MAC for endotracheal intubation is about 30 percent higher than MAC for surgical incision, a relatively deep level of anesthesia must be established. Because deep anesthesia may not be tolerated by many patients, drugs that tend to block the response to airway instrumentation or antihypertensives may be used.

Thiopentone, Propofol and Etomidate are ineffective in eliminating hemodynamic response to Laryngoscopy and intubation.

In general patients with difficult laryngoscopy or intubation or both have higher pressure response.

Hypertensive patients have more chance of pressure response.

Direct laryngoscopy is associated with more pressure response than video laryngoscopy

Narcotics are one option as an adjunct to blunt pressure response.

Fentanyl has been best studied and requires a dose of at least 3 to 4 micro gm/kg to be effective.

Alfentanil has a more rapid onset of action and is effective for this purpose, and remifentanil is also likely to be similarly effective at a dose of 25-50 micro gm/kg.

Lidocaine reduces anesthetic requirements by 30 percent with a 1.5 mg/kg IV bolus that is minimally depressive to the cardiovascular system. Intravenous lidocaine may be used to supplement the narcotic effect on hemodynamics.

A variety of antihypertensive agents have also been used to diminish the blood pressure and heart rate responses to intubation.

These include adrenergic blockers, phentolamine, nitroprusside, clonidine, captopril, nitroglycerin, and hydralazine,but their relative efficacy is not established.

1-1.5mg/kg esmolol bolus is superior to IV high-dose lidocaine or low-dose fentanyl in preventing the tachycardia associated with intubation.

Combination of lignocaine and Esmolol is effective and safe in obstetrics anaesthesia.

Other drugs not commonly used include oral gabapentin, oral clonidine and IV dexmeditomedine.

Dysrhythmias during or immediately following laryngoscopy and intubation generally resolve with adequate ventilation, and establishment of adequate anesthetic depth.

Dr. Prasanta Kumar Dash

Spontaneous recovery of neuromuscular function following administration of a nondepolarizing neuromuscular blocking agent involves diffusion of the relaxant away from the nAChR and the motor endplate, as well as its elimination from the body. Recovery is facilitated in the presence of anticholinesterases, which increase acetylcholine concentration at the motor endplate. Recovery is also influenced by depth of neuromuscular block at the time of antagonism, the clearance and half-life of the relaxant used, and any factors that affect neuromuscular blockade.

The speed of antagonism of residual block is related to the depth of block at the time of administration of the anticholinesterase. Deeper levels of neuromuscular block require a longer time for the return of twitch strength to acceptable levels. The speed of antagonism of block by either tubocurarine or pancuronium depends on the dose of neostigmine administered: larger doses of anticholinesterase are required for more complete and faster recovery of neuromuscular function.

Following neostigmine antagonism of profound pancuronium induced neuromuscular block there is an initial period of rapid but incomplete antagonism, which peaks within 10 minutes. Further recovery of neuromuscular function occurs relatively slowly; this second, slower stage of recovery appears to depend on the clearance of the relaxant. In the case of long-acting relaxants, with clearance values of 1.5–3.0 mL/min/kg and elimination half-lives of 1.5–2 hours, little drug is eliminated during the first 10 minutes after neostigmine administration, as this 10-minute period represents only about one-10th of one half life. Consequently, during antagonism of long-acting relaxants the return of neuromuscular function to normal depends almost entirely on the antagonistic effect of the anticholinesterase. For relaxants with shorter half-lives (2–20 minutes), a larger fraction of the relaxant is eliminated during the 10-minute period following administration of the anticholinesterase. Therefore, antagonism of residual blockade in the latter represents a combination of the pharmacodynamic effect of the anticholinesterase and the pharmacokinetic effect of clearance of the relaxant. The net result is that antagonism of residual effect is more rapid and more complete with shorter-acting relaxants than with long-acting relaxants. This result in a higher incidence of residual weakness in the recovery room following the administration of long-acting nondepolarizing neuromuscular blockers compared with intermediate-acting drugs.

Administration of doses of neostigmine greater than 2.5 mg is associated with an increased incidence of postoperative nausea and vomiting. In order to decrease the incidence following the administration of anticholinesterases, waiting for a greater degree of spontaneous recovery of neuromuscular function and then administering neostigmine – 2 mg or less – should be effective.

There is a limit to the depth of neuromuscular blockade that can be effectively antagonized by anticholinesterases. Anti- cholinesterases administered at any point after the administration of a nondepolarizing neuromuscular blocker will shorten the time required for recovery of neuromuscular function compared to spontaneous recovery. Recovery to clinically acceptable levels of neuromuscular function, however, occurs more quickly if the anticholinesterase is administered once a significant amount of spontaneous recovery has occurred and more acetylcholine receptors are available. In the case of neostigmine, the maximal effect of the anticholinesterase is observed approximately 7 minutes after its administration. Further recovery of neuromuscular function depends on ongoing elimination of the relaxant from the neuromuscular junction and the body.

Reference:
Christopher B Prior and Ian G Marshall Chapter 36(Neuromuscular junction physiology)) Foundations of anaesthesia basic sciences and clinical practice

Dr. Prasanta Kumar Dash

If arterial puncture occurs, you need not feel panicky. At least we can be sure that the nerves are close by. Withdraw the needle and apply pressure over the puncture site not allowing a haematoma to develop. Now redirect the needle little laterally. Invariably you will get the paraesthesia.

If haematoma develops, it will confuse the aspiration test. Blood will appear in the syringe even if the needle is not in the vessel. And also, the haematoma may make the block patchy.

2. If paraesthesia is not obtained, the success rate of the plexus blocks decreases. As the sheath containing the plexus crosses the 1st rib in a narrow area, it is possible that we may end up outside the sheath even though the needle is on the rib. (Now a days the existence of a complete sheath covering the brachial plexus is being questioned – Ref: The sheath of the brachial plexus: fact or fiction? Even then deposition of drug as close to the plexus is advisable.)

So it is better to get paraesthesia or conducted pulse of the subclavian artery on your needle.( Even though I still practice the paraesthesia technique, experts say eliciting paraesthesia is not advisable as it may injure the nerves permanently).

3. Increasing the volume by diluting the drug will not increase the success rate. Success depends upon the placement of solution as close to the plexus as possible. In fact using higher volume sometimes results in ascend of solution high up causing phrenic nerve blockade.

Some tips for the successful block:

1. Proper positioning
2. Proper selection of the patient. (Highly anxious, very obese patients are not suitable for blind blocks)
3. Availability of adequate time for you to give the block
4. Identifying the lower end of inter scalene groove.
5. Not allowing the surgeon to peep into your technique
6. USING PNS or ULTRASOUND FOR IDENTIFICATION OF PLEXUS.

Ref: The Sheath of the Brachial Plexus: Fact or Fiction? Anesthesiology: September 2006 – Volume 105 – Issue 3 – pp 563-565
Dr.R.Selvakumar
Professor of Anaesthesiology
K.A.P.Viswanatham Govt Medical College, Trichy