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

PHARMACOLOGICAL TREATMENT OF ACUTE SEVERE ASTHMA ( BASED ON 2014 BTS GUIDELINES)

✔️Supplementary oxygen to all hypoxaemic patients with acute severe asthma to maintain an SpO2 level of 94-98%

✔️Nebulisers for giving nebulised β2 agonist bronchodilators should preferably be driven by oxygen. A flow rate of 6 l/min is required to drive most nebulisers

✔️High-dose inhaled β2 agonists as first line agents in patients with acute asthma. Repeat doses of β2 agonists at 15–30 minute intervals or give continuous nebulisation of salbutamol at 5–10 mg/hour (requires appropriate nebuliser) if there is an inadequate response to initial treatment. Higher bolus doses, for example 10 mg of salbutamol, are unlikely to be more effective (2.5–5 mg salbutamol in children >2 years).

✔️There is no evidence for any difference in efficacy between salbutamol and terbutaline. Nebulised adrenaline (epinephrine), a non-selective β2 agonist, does not have significant benefit over salbutamol or terbutaline.

✔️Add nebulised ipratropium bromide (0.5 mg 4-6 hourly) to β2 agonist treatment for patients with acute severe or life-threatening asthma or those with a poor initial response to β2 agonist therapy. ( 250 micrograms/dose in children >2 years).

✔️Consider giving a single dose of IV magnesium sulphate (1.2-2 g IV infusion over 20 minutes) to patients with acute severe asthma who have not had a good initial response to inhaled bronchodilator therapy.

✔️Nebulised magnesium is not recommended for treatment in adults with acute asthma. Consider adding 150 mg magnesium sulphate to each nebulised salbutamol and ipratropium in the first hour in children >2 years with a short duration of acute severe asthma symptoms presenting with an oxygen saturation less than 92%.

✔️Routine prescription of antibiotics is not indicated for patients with acute asthma.

SECOND LINE TREATMENT OF ACUTE ASTHMA

✔️Consider early addition of a single bolus dose of intravenous salbutamol (15 micrograms/kg over 10 minutes) in a severe asthma attack where the patient has not responded to initial inhaled therapy.

✔️Consider aminophylline for children >2 years with severe or life-threatening asthma unresponsive to maximal doses of bronchodilators and steroids. A 5 mg/kg loading dose should be given over 20 minutes with ECG monitoring (omit in those receiving maintenance oral theophyllines) followed by a continuous infusion at 1 mg/kg/hour. Measure serum theophylline levels in patients already receiving oral treatment and in those receiving prolonged treatment.

NOTE:

✔️Give steroids in adequate doses in all cases of acute asthma attack.

✔️Prednisolone 40–50 mg daily or parenteral hydrocortisone 400 mg daily (100 mg six-hourly in adults and 4 mg/kg repeated four hourly in children >2 years ) are as effective as higher doses. Continue prednisolone 40–50 mg daily for at least five days or until recovery. ( In children >2 years, treatment for up to three days is usually sufficient).

✔️Following recovery from the acute asthma attack steroids can be stopped abruptly. Doses do not need tapering provided the patient receives Inhaled Corticosteroids

✔️In adults with an acute asthma attack, i.v. aminophylline is not likely to result in any additional bronchodilation compared to standard care with inhaled bronchodilators and steroids. Side effects such as arrhythmias and vomiting are increased if Iv aminophylline is used

✔️Heliox is not recommended for use in patients with acute asthma outside a clinical trial setting

✔️Although theoretically furosemide may produce bronchodilation, a review of three small trials failed to show any significant benefit of treatment with nebulised furosemide compared to β 2 agonists

Anesthesia implications of Von Hippel–Lindau disease (vHLD)

🎨vHLD usually presents in young adults with cerebellar, medullary or spinal haemangioblastomas, retinal angiomatosis, renal cell carcinoma and phaeochromocytoma

🎨The frequency of phaeochromocytomas is 7–20%

🎨About 25% of patients with CNS haemangioblastomas subsequently turn out to have vHLD.

🎨Erythrocytosis and a high haematocrit are common and has to be searched for.

🎨Surgery for one manifestation of the disease may be complicated by the presence of an undiagnosed phaeochromocytoma. In this situation, pharmacological control of phaeochromocytoma should get more priority and surgery may have to be carried out in two stages

🎨Spinal anaesthesia may be dangerous in the presence of an undiagnosed cerebral or spinal tumour. Another point is, spinal cord haemangioblastomas can occur at more than one level. An MRI if already done, can help us to take a proper decision.

🎨Pregnancy may worsen the disease, by increasing the vascularity of tumours. Urgent and life saving neurosurgical intervention may become necessary: for e.g. when a spinal tumor bleeds, when a tumor obstructs CSF flow and causes acute hydrocephalus. Sometimes elective procedures like removal of a phaeochromocytoma which became evident during pregnancy has to be removed. It may become necessary to carry out these procedures during pregnancy or along with a Caesarean section.

🎨Surgery may be required for more than one lesion at the same time.

🎨So careful assessment should be made for lesions other than the one for which anaesthesia is required, and in particular for any symptoms and signs of cerebral, cerebellar or spinal cord tumours and phaeochromocytoma.

🎨In the situation in which two lesions are present, decisions may have to be made as to whether to operate simultaneously or separately . During pregnancy the management of the delivery must be carefully planned in advance.

🎨Although 24-h urinary screening for catecholamines can be performed, plasma normetanephrines and metanephrines are the most sensitive tests for detecting phaeochromocytomas in patients with family predisposition

Reference: Anaesthetic management of a patient with von Hippel–Lindau disease: a combination of bilateral phaeochromocytoma and spinal cord haemangioblastoma. European Journal of Anaesthesiology 13: 81–3. , Anesthesia Databook, 3rd edition 

NICE guidelines for treatment of hypertension: really NICE❗️

💓NICE published guidelines in 2006, revised in 2011. 

💓)))) Step 1 : Choose either an ACE inhibitor, a thiazide diuretic or a calcium channel antagonist (A, D and C). 

💓An ACE inhibitor is more effective as first-line therapy in younger patients (< 55 years ) and Caucasians. 

💓Diuretics or calcium channel blockers are better in older patients and African / Caribbean patients of any age. 

💓 This trial of step 1 is run on for 4 weeks, and if blood pressure is not controlled, the opposite agent is added in:

💓 )))) Step 2 : An ACE inhibitor is added to a diuretic (A + D) or calcium channel antagonist (A + C), or vice versa. 

💓 )))) Step 3 : Ongoing poor control is then managed by the addition of the third agent (A + C + D). 

💓 )))) Step 4 : If a patient is established on triple therapy, and still not well controlled, they are probably aldosterone sensitive, so spironalactone would be a wise option.

National Institute for Health and Clinical Excellence. Hypertension: Clinical Management of Primary Hypertension in Adults. NICE Clinical Guideline 127, August 2011. 

#Hypertension , #NICEguidelines , #antihypertensives

HYPERTONIC SALINE VS MANNITOL FOR MANAGEMENT OF ACUTELY RAISED ICP

🔳 Like mannitol, hypertonic saline

🔻create an oncotic pressure difference that mobilises water across the blood–brain barrier through osmosis. 

🔻shrinks erythrocytes and makes them more deformable 

🔻increases the calibre of the microcirculation by dehydrating vascular endothelium

🔳 Advantages of Hypertonic Saline over mannitol:

🔻less haemodynamic instability

🔻less damage to the kidneys 

🔻easier therapeutic monitoring through tracking serum sodium concentration. 

🔻less inclined to produce the late rise in ICP sometimes found with mannitol when it is deposited in the brain parenchyma.

🔳 But no difference in survival between the two agents has been demonstrated.