Neuromuscular blockade monitoring

This topic tests your knowledge of the physics and physiology behind the use of neuromuscular blocking drugs (NMBDs). You will benefit from a clear idea in your mind about what each type of nerve stimulation pattern is attempting to demonstrate. 

A single, supra-maximal stimulus is applied prior to neuromuscular blockade as a control. The diminution in twitch height and disappearance of the twitch correlates crudely with depth of neuromuscular block. 

An electrical stimulus of sufficient current magnitude to depolarize all nerve fibres within a given nerve bundle. Commonly quoted as 60 mA for transcutaneous nerve stimulation. 

Notice that you are being asked to describe the output waveform of the nerve stimulator. The axes must, therefore, be time and current as shown. Each stimulus is a square wave of supra-maximal current delivered for 0.2 ms. The train of four (TOF) is delivered at 2 Hz so there is one stimulus every 500 ms. This means that if the TOF starts at time 0, the complete train takes 1500 ms. 

A supra-maximal stimulus applied as a series of square waves of 0.2 ms duration at a frequency of 50 Hz for a duration of 5 s is tetanic stimulation. 

---

Frankel H, Jeng J, Tilly E, St Andre A, Champion H. The impact of implementation of neuromuscular blockade monitoring standards in a surgical intensive care unit. Am Surg 1996 62(6) 503-6. 

When an aminoglycoside is being administered, it is important to monitor the patient s respiratory rate because neuromuscular blockade has been reported with the administration of these dragp. The nurse reports any changes in the respiratory rate or rhythm to the primary health care provider because immediate treatment may be necessary. 

Paralysis usually is reserved for cases in whom sedation alone does not improve the effectiveness of mechanical ventilation. Neuromuscular blockers may lead to prolonged skeletal muscle weakness and should be avoided if possible. Patients requiring neuromuscular blockade are to be monitored and intermittent boluses should be utilized. 

Peds. Cardiac arrest w/ torsades 25-50 mg/kg/dose IV Caution [B, +] Contra Heart block Disp Inj 10, 20, 40, 80, 125, 500 mg/mL bulk powder SE CNS depression, D, flushing, heart block Interactions T CNS depression W/ antidepressants, antipsychotics, anxiolytics, barbiturates, hypnodcs, narcotics EtOH T neuromuscular blockade W/ aminoglycosides, atracurium, gallamine, pancuronium, tubocurarine, vecuronium EMS Monitor ECG for changes Mannitol (Osmitrol) [Osmotic Diuretic] Uses Tx cerebral edema (T ICP) Action Diuretic Dose Adults. 0.5-2 g/kg slow IV Peds. 0.2-0.5 g/kg IV over 60 min Caution [C, ] Contra Pulm edema, CHF, cerebral bleeding Disp Inj, sol 5% (50 mg/mL) 10% (100 mg/mL) 15% (150 mg/mL) 20% (200 mg/mL) 25% (250 mg/mL) SE N/V, HA, dizziness, edema, blurred vision, diuresis, dehydration Interactions Interferes w/ blood transfusions EMS Use caution to prevent extravasation (use large vein) rebound T in ICP has been noted about 12 h post administration... 

LIDOCAINE DEPOLARIZING t efficacy of suxamethonium with intravenous lidocaine Uncertain Monitor neuromuscular blockade carefully... 

DEPOLARIZING, NON-DEPOLARIZING VANCOMYCIN 1. t efficacy of these muscle relaxants 2. Possible risk of hypersensitivity reactions 1. Vancomycin has some neuromuscular blocking activity 2. Animal studies suggest additive effect on histamine release 1. Monitor neuromuscular blockade carefully 2. Be aware... 

DEPOLARIZING AND NON-DEPOLARIZING MAGNESIUM (PARENTERAL) t efficacy of these muscle relaxants, with risk of prolonged neuromuscular blockade Additive effect magnesium inhibits ACh release and 1 postsynaptic receptor sensitivity Monitor nerve blockade closely... 

If it is suspected that an antibiotic is contributing to prolonged neuromuscular blockade, the patient should be monitored and the effect of calcium (up to 1 g of calcium chloride slowly) should be observed. If this is unsuccessful, neostigmine (maximum dose 5 mg for an adult) or edrophonium (0.5 mg/kg) can be tried, but these agents may intensify a block due to cohstin, lincomycin, or polymyxin B. If the other remedies fail, 4-aminopjTidine (maximum dose 0.3 mg/kg) can be successful. Artificial ventilation should be continued until adequate spontaneous efforts are achieved and other possible factors, such as acidosis or electrolyte disturbances, are corrected. 

Goldhill DR, Wainwright AP, Stuart CS, Flynn PJ. Neostigmine after spontaneous recovery from neuromuscular blockade. Effect on depth of blockade monitored with train-of-four and tetanic stimuli. Anaesthesia 1989 44(4) 293-9. 

Clinical Responses and Monitoring of Phase I and Phase H Neuromuscular Blockade by SuccinylchoUne Infusion ... 

---