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Thursday, June 23, 2016

STEROIDS : EQUIVALENT DOSES



Saturday, June 18, 2016

AHA CPR GUIDELINES: MAJOR CHANGES 2015 Vs 2010


Friday, June 17, 2016

<Ⓜ️NEMO WFNS GRADING SCALE FOR SAH

▪️I   : GCS 15

▪️II  : FULL GCS-2 ( 15-2=13 )

▪️III : 3D ( DEFICIT (+) for WFNS III )

▪️IV : "ForSee a dozen problems" ( i.e. WFNS 'Four'->GCS is 'Seven' {~ForSee}.. to 12 {a dozen})

▪️ V : "5-6"( WFNS 5 means GCS <6 )


ANEURYSM CLIP VIVA VOCE ; SURGICAL PEARLS FOR THE ANESTHESIOLOGIST / 'SAFE Anesthesiologist' Series [Surgical Aspects For Empowering the Anesthesiologist]

❓CAN YOU TELL A FEW SITUATIONS WHERE ENDOVASCULAR THERAPY MAY BE A BETTER OPTION THAN SURGERY?

🅰 Aneurysms in elderly patients, in patients with poor neurological condition, in patients presenting with cerebral vasospasm, 
aneurysms that are difficult to surgically access and multiple aneurysms requiring multiple craniotomies for treatment

❓ CAN YOU TELL A FEW SITUATIONS WHERE SURGERY MAY BE A BETTER OPTION THAN ENDOVASCULAR THERAPY?

🅰  fusiform, blister-like, very small, very large, thrombotic, and wide-necked aneurysms, in patients presenting with a clinically significant intracerebral hemorrhage

❓CAN YOU TELL A FEW ADJUNCTS WHICH THE SURGEON MAY USE OR MAY ASK FROM THE ANESTHESIOLOGIST TO MINIMIZE THE RISK OF DIRECT BRAIN INJURY

🅰 Good bony removal to minimize or eliminate brain retraction, meticulous microsurgical dissection to preserve veins, pharmacologic brain protection or bypass procedures to reduce the risk of ischemic injury, use of temporary clips to reduce the risk of intraoperative rupture, and intraoperative imaging with digital subtraction angiography or indocyanine green videoangiography to verify surgical results

❓WHAT IS THE PROBLEM IF THE BONE DRILLING / EXPOSURE IS LESS THAN ADEQUATE 

🅰 Surgeon will be forced to use more brain retraction throughout the surgery , which may result in direct brain injury and thus  increase the chances of postoperative complications 

❓WHAT IS THE PROBLEM IF THE SURGEON OVERLOOK THE IMPORTANCE OF PRESERVING THE VEINS WHILE FOCUSING ON THE ARTERIAL ANATOMY 

🅰This can hamper venous drainage and can result in devastating venous congestion and infarction, postoperatively

❓WHAT ARE THE METHODS AVAILABLE TO PROLONG ISCHEMIC TOLERANCE TIMES DURING TEMPORARY CLIPPING

🅰 Burst suppression using Propofol or Barbiturates, induced hypertension, Hypothermia

❓ WHAT IS THE MAJOR ADVANTAGE OF SURGICAL CLIP LIGATION OF ANEURYSM OVER ENDOVASCULAR OPTIONS

🅰 Low risk of recurrence, if the clipping has been appropriate

❓WHAT ALL METHODS ARE AVAILABLE FOR THE SURGEON  IN DETERMINING WHETHER THE ANEURYSM IS COMPLETELY OBLITERATED AFTER CLIPPING

🅰 Puncturing the dome of the aneurysm after clipping and observe for refilling, Intraoperative angiography, indocyanine green videoangiography ( Indocyanine green dose : 0.2-0.5mg/kg bolus, max daily dose= 5mg/kg  )

❓ WHAT ALL METHODS ARE AVAILABLE FOR THE SURGEON  IN DETERMINING WHETHER THERE IS ANY COMPROMISE OF PARENT VESSEL AFTER CLIPPING

🅰intraoperative angiography,  Indocyanine green videoangiography and Microvascular doppler

❓ WHAT ARE THE METHODS AVAILABLE FOR THE SURGEON TO AVOID INTRAOPERATIVE RUPTURE OF THE ANEURYSM

🅰 Adequate exposure, sharp dissection, proximal control, and use of temporary clips. For proximal carotid aneurysms, control may require exposure of the cervical carotid, which also allows the surgeon to trap the aneurysm and to use suction decompression

❓IN THE EVENT OF AN UNTIMELY INTRAOPERATIVE RUPTURE OF AN ANEURYSM, WHAT ARE THE METHODS AVAILABLE FOR CONTROLLING THE BLEEDING

🅰 In this situation the tasks for the surgeon are: (1) Control bleeding (2) Repair the aneurysm & (3) Repair the arterial defect. For controlling the bleeding many techniques have been described, including use of a large-bore suction over the bleeding site , tamponade with a cottonoid, proximal temporary occlusion or trapping, carotid compression, coagulation of the aneurysmal rent, clip application to the distal sac, and induced hypotension. Sometimes the surgeon may ask for an Adenosine induced flow arrest, for placing the clip.

Reference: Chaper 13, Intraoperative Misadventures: Complication Avoidance and Management in Aneurysm Surgery
Daniel L. Barrow, Clinical Neurosurgery, Volume 58, 2011, The Congress of Neurological Surgeons



Wednesday, June 15, 2016

TARGET CONTROLLED INFUSIONS DURING ANESTHESIA; PHARMACOLOGICAL PRINCIPLES


⏩TCIs are used for sedation and as an alternative to inhalational anaesthesia. 

⏩Here an infusion, controlled by a microprocessor-driven pump that alters the infusion rate to maintain a user-defined target plasma concentration ( as guided by certain pharmacokinetic models e.g. modified Marsh model and Schnider models for propofol and the Minto model for remifentanil.) delivers the drug.

⏩ Previous models used the plasma concentration (Cp) to target. Recent models target an effect site concentration (Ce). The 'effect site compartment' reflects the hysteresis between plasma concentration and the clinical effect observed.

⏩They basically work based on the principle of the bolus, elimination and transfer regime:

1️⃣An initial bolus dose to fill the central compartment with the drug (B)

2️⃣An infusion of constant rate, equal to the elimination rate (E)

3️⃣An infusion that compensates for transfer of drug to the peripheral tissues (T)
.......forming the 'BET' regimen

⏩ The Marsh model assumes that the central compartment volume is directly proportional to the weight of the patient only. It does not use age as part of its calculation, but will not function if an age less than 16 is entered. 

⏩ The more recent Schnider model calculates lean body mass using age, height and weight and calculates doses and infusion rates accordingly. 

⏩ Consequently , there is difference, in the size of the central compartment when calculated using different models

REMEMBER👇🏾

⏩The plasma and effect-site concentrations are calculated ; not measured (as compared with end tidal agent monitoring). 

⏩The hemodynamic impact of the drug will depend upon the maximum plasma concentration achieved and so in elderly patients, a large overshoot in the plasma concentration and haemodynamic compromise can happen, when a bolus is given: be cautious

⏩In morbidly obese patients with a BMI > 42, with increasing body weight the calculation of Lean Body Weight used in the Schnider model paradoxically decreases. This decrease leads to a higher estimated clearance and thus a larger initial bolus dose and higher infusion rate will be administered by the pump.

#TargetControlledInfusions , #anesthesia ,#anaesthesia , #tci , #infusion , #pharmacology , #propofol , #pharma , #biomedical ,#CriticalCare

Reference: Hill SA. Pharmacokinetics of drug infusions. Contin Educ Anaesth Crit Care Pain. 2004; 4(3): 76–80.

Tuesday, June 14, 2016

Anesthesia concerns in Takotsubo (Stress) Cardiomyopathy

💓 Various stress-related cardiomyopathy syndromes are 
(1) classic Takotsubo cardiomyopathy, which presents as an acute coronary syndrome 

(2) left ventricular dysfunction associated with acute intracranial disease, especially Aneurysmal SAH 

(3) transient cardiomyopathy, which occurs during other critical illness, especially sepsis, and 

(4) transient cardiomyopathy associated with pheochromocytoma and exogenous catecholamine administration

💓 Takotsubo Cardiomyopathy is also known as takotsubo syndrome, broken heart syndrome, ampulla cardiomyopathy, transient left ventricular apical ballooing, apical ballooning syndrome, transient left ventricular dysfunction syndrome, and stress [induced] cardiomyopathy

💓 It was first described in Japan in 1990

💓 Patients were with out significant epicardial coronary artery disease, 

💓 It presents like like an acute coronary syndrome ; but symptoms like chest pain, dyspnea, and ECG changes may not be there in all cases

💓 Was most frequently in postmenopausal elderly women

💓 Was often triggered by stressful situations. 

💓 Classic pattern of wall motion abnormality observed is “apical ballooning” usually associated with hyperkinesia of the basal segments ( but its NOT pathognomonic of the disease)

💓 Onset is often preceded / precipitated by emotional or physiologic stress (NOT invariably)

💓 Researchers at the Mayo Clinic proposed diagnostic criteria in 2004, which have been modified recently :

 (1) transient hypokinesis, akinesis, or dyskinesis in the left ventricular mid segments with or without apical involvement; regional wall motion abnormalities that extend beyond a single epicardial vascular distribution; and frequently, but not always, a stressful trigger; 

(2) the absence of obstructive coronary disease or angiographic evidence of acute plaque rupture

(3) new ECG abnormalities (ST-segment elevation and / or T-wave inversion) or modest elevation in cardiac troponin; and 

(4) the absence of pheochromocytoma and myocarditis.

💓 The most commonly accepted cause is excessive adrenergic/ catecholamine stimulation, which damages cardiomyocytes 

💓 Reports of its acute precipitation by administration of catecholamines (like adrenaline or dobutamine), its occurrence in patients with pheochromocytoma  and its reproduction by infusion of adrenaline in primates support this hypothesis

💓 Most patients recover without complications; but others may develop complications like congestive heart failure, pulmonary edema often requiring endotracheal intubation and mechanical ventilation, cardiogenic shock requiring vasopressor or inotropic therapy and even intraaortic balloon pumping

💓 Regarding treatment in the acute phase, avoidance of adrenergic agonists and initiation of antiadrenergic therapy (e.g., adrenergic blocking drugs or centrally acting 2 agonists) have been advocated

💓 In patients presenting with left ventricular outflow tract obstruction, catecholamines are particularly contraindicated

💓 If inotropic therapy is needed (as in case of heart failure, pulmonary edema, and cardiogenic shock etc., there has been suggestions, that the calcium sensitizer levosimendan may be the better choice

💓 One school of thought is that a substantial portion of the damage caused by catecholamine toxicity to the myocardium has likely occurred by the time of clinical presentation, and thus administration of antiadrenergic therapy at this time is unlikely to completely reverse injury. Infact, in a number of reported cases, catecholamines seem to have facilitated recovery in patients with acute left ventricular dysfunction

Reference: anesthesia-analgesia March 2010 • Volume 110 • Number 3,circ.ahajournals.org/content/118/25/2754.full

TOTAL BODY WEIGHT (TBW) , LEAN BODY WEIGHT (LBW), IDEAL BODY WEIGHT (IBW) & ADJUSTED BODY WEIGHT (ABW) ; THEIR IMPLICATIONS IN ANESTHESIA AND CRITICAL CARE

🏀 Drug administration in obese patients is difficult because recommended doses are based on pharmacokinetic data obtained from individuals with normal weights

🏀 With increasing obesity, fat mass accounts for an increasing amount of TBW, and the LBW/TBW ratio decreases

🏀 TBW is defined as the actual weight 

🏀 IBW is what the patient should weigh with a normal ratio of lean to fat mass 

🏀 IBW can be estimated from the formula: IBW (kg) = Height(cm)  x ( where x = 100 for adult males and 105 for adult females).

🏀 LBM is the patient's weight , excluding fat

🏀Male LBM = 1.1(weight)-128(weight/height)^2 (Weight in Kg and Height in cm)

🏀Female LBM = 1.07 (weight) -148 (weight/height)^2

🏀Regardless of total body weight, lean body weight rarely exceeds 100 kg in men and 70 kg in women 

🏀 Below IBW, TBW and LBM are similar. 

🏀 Adjusted body weight (ABW) Takes into account the fact that obese individuals have increased lean body mass and an increased volume of distribution for drugs.

🏀 It is calculated by adding 40% of the excess weight to the IBW :
ABW (kg) = IBW (kg) + 0.4 (TBW (kg)   IBW (kg)


🏀 Drugs with weak or moderate lipophilicity can be dosed on the basis of IBW or more accurately on LBM. These values are not same in obese; because 20–40% of an obese patient's increase in TBW can be attributed to an increase in LBM. Adding 20% to the 'estimated IBW based dose' of hydrophilic medication is sufficient to include the extra lean mass. Non-depolarizing neuromuscular blocking drugs can be dosed in this manner. 

🏀 In morbidly obese patients, the induction dose of propofol can be calculated on IBW. 

🏀 In case of midazolam, prolonged sedation can occur from the larger initial dose needed to achieve adequate serum concentrations. 

🏀 Remifentanil dosing regimens should be based on IBW or LBM and not on TBW. 

🏀 When using succinylcholine in obese adults or adolescents, dosage should be calculated on TBW

🏀 The antagonism time of neostigmine has been shown to be independent of TBW and BMI. Therefore, TBW can be used to calculate the dose.
Male LBM  1.1weight128weightheight2
IBW kg  height cm  x
Ref:Association of Anaesthetists of Great Britain and Ireland. Peri-operative management of the obese surgical patient 2015. Anaesthesia 2015, 70, pages 859–876.

http://bja.oxfordjournals.org/content/105/suppl_1/i16.full



Sunday, June 12, 2016

MEASUREMENT OF CORE BODY TEMPERATURE: FAQs

❓What's the problem, if we place the temperature probe in upper 1/3rd or 2/3rd if the esophagus?

✔️Esophageal temperature should be taken from the lower third of the oesophagus; placed above this level, the probe may under-read due to cooling effect of inspired gases. It gives a good estimate of cerebral blood temperature. 

❓What's the advantage of nasopharyngeal temperature measurement over oesophageal measurement?

✔️The nasopharyngeal temperature probe is placed just behind the soft palate. The advantage is that it is more accessible compared to the oesophageal temperature measurement. The disadvantage is that it is less accurate in representating the core temperature.

❓What are the advantages of measurement of temperature @ Tympanic membrane?

✔️The tympanic membrane provides an accurate representation of hypothalamic temperature. It is less invasive, has a short response time and correlates well with oesophageal temperature. But it does not allow continuous measurements.

❓What is the best method for CONTINUOUS measurement of core temperature?

✔️Blood temperature measurement using a pulmonary artery flotation catheter 

❓What are the factors reducing the accuracy of Rectal temperature measurement?

✔️Rectal temperature is influenced by heat generated from gut flora, the cooling effect of blood returning from the lower limbs and the insulation of the probe by faeces. It is normally about 0.5–1.0 ° C higher than core temperature and has a slow response time. 

❓Can you say an e.g. of utilising the temperature gradients existing between different sites of the body for clinical advantage?

✔️The gradient between a skin temperature and a core temperature can be used as a marker of peripheral perfusion.

Thursday, June 9, 2016

MONITORING OF NEUROMUSCULAR BLOCK : DO YOU FREQUENTLY FORGET THE NUMBERS RELATED TO TOF, DBS & PTC?

Train of four (TOF) 

💥four stimuli {T1-T4} are given at a frequency of 2 Hz (0.5 sec between the stimuli)

💥 Each stimulus in the train causes the muscle to contract and the 'fade' in the response allow us to evaluate the neuro muscular blockade

💥The ratio T4:T1 ( i.e. Dividing the amplitude of the fourth response by the amplitude of the first response ) indicates the degree of neuromuscular block. 

💥Non-depolarizing NMBAs produce a decrease in magnitude of the first twitch compared with a pre-relaxant stimulus, and a progressive reduction in magnitude of T1–T4. 

💥The number of elicited twitches indicates the degree of receptor occupancy. 

💥Disappearance of T4, T3, T2, T1 corresponds to 75%, 80%, 90% and 100% occupancy. 

💥With recovery of neuromuscular function the twitches appear in the reverse order. 

💥 Accepted values for TOF count are:

🔹 1 twitch for tracheal intubation

🔹1–2 twitches during established anaesthesia

🔹1 twitch for tracheal intubation

🔹1–2 twitches during established anaesthesia

🔹3–4 twitches before reversal of neuromuscular blockade is attempted.



Double burst stimulation 

💥 Consists of two bursts  ( the duration of each square wave impulse in the burst is 0.2 sec ) at 50 Hz with each triple burst separated by 750 ms. 

💥 DBS with 3 impulses in each of the two tetanic bursts is commonly used

💥 These manifest visually as two separate stimuli (T1 and T2). 

💥 The ratio is related to the TOF ratio and is easier for the operator to interpret reliably.

💥 Used under light paralysis where train of four ratio is difficult to distinguish


Post-tetanic Count (PTC) 

💥 PTC is used when there is no response to TOF stimuli and also when we want to eliminate sudden movements of the patient completely as during ophthalmic and neurosurgery

💥 Uses tetanic stimulation at 50 Hz for 5 s to mobilize presynaptic ACh (to ‘kick start’ the nerve under deep paralysis) 

💥 After a recovery time of 3 sec , it's followed by 20 pulses at 1-2 Hz twitch stimulation 

💥 The number of twitches generated (i.e. the post-tetanic count) reflects the degree of neuromuscular blockade.  

💥 Shows fade response earlier than train of four 

💥 Used under deep paralysis to estimate time to recovery


Reference: frca.uk Anesthesia Monitoring Techniques , Miller's Anesthesia , 7/e