Anesthesia work station

The modern anaesthesia workstation is designed to be a complete anaesthesia and respiratory gas delivery and monitoring system. The new machines use advanced electronics, software and technology to offer extensive capabilities for ventilation, monitoring, inhaled agent delivery, low-flow anaesthesia and closed-loop anaesthesia.

Example: Draeger Primus

The components of the workstation are:

1. The gas delivery and scavenging system. 
2. The vapourisers. 
3. Electronic flow meters. 
4. The ventilator. 
5. The monitors. 

Electronic flow meters:

These are more accurate and do not have the disadvantages of having multiple mechanical parts which are prone to leaks and breakages. The flow can be displayed electronically by a numerical display or ‘virtual flow tubes’à easy identification of gas flows in a darkened theatre and the export of electronic data to an information system.

In some machines mechanical flow meters are provided to deliver oxygen in absence of electrical power.

Circle systemModern anaesthesia machines are primarily designed to use a circle system equipped with features for low flow anaesthesia. The circuits are made compact to reduce circuit volumes to enable rapid changes in gas composition at low flows. Also the manifold may be heated to reduce condensation of water vapour. Built in water traps in the circuit to collect the precipitation. Vertically mounted unidirectional valves to decrease resistance to flow.

Carbon dioxide (CO₂) absorbers are also now available as disposable units for ease of replacement 

VENTILATOR
Machines are equipped with technology and features present in advanced intensive care unit ventilators. Ventilation modes such as pressure support ventilation (PSV) and volume assist ventilation have been introduced to support ventilation in patients maintained on spontaneous breathing through a LMA. In addition, synchronized intermittent mandatory ventilation (SIMV) breaths can be added to both pressure and volume controlled ventilation.

They have the ability to deliver very low tidal volumes accurately.

Respiratory monitors

1. Spirometry
   
2. Waveformsàpressure time and volume time waveform plus some also show flow time & flow volume waveforms for ventilating diseased lung.

Target Controlled Anaesthesia (TCA)à anaesthetists simply set their targets (end tidal agent concentration), allowing the machine to calculate reasonable and efficient way of delivery.
(help protect against over-delivery and under-delivery of agent and hypoxia. This provides cost-effective anaesthesia by keeping gas consumption to an absolute minimum.)

TIVAà  they have syringe pumps with integrated drug database actively linked to a software system which automatically sets default values and dosages boundaries for various drugs

Automatic machine check (self-test)à Most modern anaesthesia delivery systems perform the self-test and have ability to detect and report the faults

Monitoring stationà

Touch screen operations with drop down menu allow access to many functions through simple commands.
Flexible screen configurations that can be configured according to need, with extensive clinical measurements menu that include haemodyanamic, respiration and ventilation monitoring, temperature, anaesthesia depth monitoring and anaesthesia gas monitoring.

·        Certain monitors also provide monitoring of muscle relaxation.

Limitations

1. Continued movement of a descending bellows despite a leak or disconnection. 
2. A small amount of PEEP transmitted to the patient during ventilation with an ascending bellows system. 
3. Augmentation of tidal volume when the oxygen flush is activated in the inspiratory phase of ventilator delivered breath in machines without FGD. 
4. Dependence on electricity. 
5. Inability to detect CO production 
6. human error due to ignorance or lack of understanding or training.

Nanotechnology in anesthesia

Nanotechnology is defined as the art and science of assembling objects on a scale under 100 nanometers in length.

The concept of nanotechnology was first propounded by Nobel Laureate Richard Feynman in 1959.

Use in anesthesia: Functionalities can be added to nanomaterials by interfacing them with biological molecules. Once injected, the nanorobots would freely float inside the body, detecting and attaching to very specific receptors, for example, gamma-aminobutyric acid (GABA), opioid and neuromuscular junction receptors.Thus, they would perform a highly focussed task:

·  In the brain, by attaching to GABA receptors they produce loss of consciousness and amnesia,

· At the neuromuscular junction they provide full muscle relaxation giving good intubating conditions

· Activation of opioid receptors causing profound analgesia.

The desirable characteristics of a nanorobot are an optimal size of 0.5–3 μm to enable passage through capillaries, non-agglutinability with blood cells and recognisability of very specific receptors only.

POSSIBLE ADVANCES OF NANOTECHNOLOGY IN ANAESTHESIOLOGY

1. General anaesthesia

• Administration, regulation and monitoring of GAà Neuroelectronic interfacing will allow nanodevices to be linked to the human nervous system. This would permit control and detection of nerve impulses to be interpreted by an external computerà computer-controlled GA (researchers from Canary Islands have developed a technique for automatically controlling anaesthesia)
•  Effects of coexisting diseases and injuries impairing anaesthesia could be overcome through using neuroelectronic interface

2. Regional anaesthesia

Bupivacaine overdoseà antidote of bupivacaine with nanotechnology. There is a formation of pi–pi complexes between bupivacaine and a pi-electron–rich injectable nanoparticle. This complex is devoid of the clinical effects of bupivacaineàrapid and easy management of high spinal anesthesia

3. Local anaesthesia

Rapid local transdermal anaestheticà lidocaine-loaded (PCL–PEG–PCL) nanoparticles.

Tested in ratsàsuperior in terms of onset of anaesthesia and efficacy. Further research awaited.

4. Future advances in superspecialities of anaesthesiology

• Chronic Pain and palliative careà saxitoxin, a potent anaesthetic, bundled with liposomes. This is a slow- release formulation can produce a nerve block lasting from days to weeks and even months, at the same time being nontoxic to the nerves or the surrounding tissue.

• Critical care:

1.  Vasculoidsà circulatory system in the  form of artificial blood which transports resources around the body without the need for a heart or other pump àserves as a complete replacement for natural blood.
2. Respirocytesà hypothetical, microscopic, artificial red blood cells that can emulate the function of natural RBC  with 200 times the efficiency. Respirocytes would also speed up weaning from ventilators.
3. Clottocytesà artificial mechanical plateletsà The response time of a clottocyte would be on the order of 100-1000 times quicker than nature's platelets, achieving complete hemostasis in as short as one second.
4. Nanoatropine: In Organophosphorus poisoningà inhaled atropine (dry powder which can be inhaled quickly by the time other therapeutic options are arranged).
5. Microbivoresàmimic white cells and perform phagocytosis of specific bacteria, viruses or fungi. Control of drug resistant infections.

Advantages of Nanorobots:

1. As the nanorobots are nonbiological entities and do not generate any harmful activities, there shall be no side effects
2. They are useful in both general as well as regional anaesthesia
3. Being highly specific and target oriented, they reduce the anaesthesia-associated mortality and morbidity
4. Since they reach specific receptors, lesser drug dosage is required, limiting the side effects
5. As they bind the terminal receptors, there shall be no peaks and troughs in effect.

Disadvantage: high cost and complicated fabrication

Further Reading:

1.	Drexler KE. Nanosystems: Molecular Machinery, Manufacturing, and Computation. 1992..
2.	Kaira L, Singh R. Nanotechnology : the new era of technology. Nitte University Journal of Health Science. 2012 December ; 2(4).
3.	Agarwal A. The future of anaesthesiology. IJA. 2012; 56(6): p. 524-528.
4.	Iliades C, Jon N. everydayhealth.com. [Online]. [cited 2015 may. Available from: http://www.everydayhealth.com/pain-management/nanoparticles-the-high-tech-way-to-treat-pain.aspx.

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Awake Intubation (procedure in brief)

Sugammadex

Sugammadex is an agent for reversal of neuromuscular blockade by the rocuronium. It is the first selective relaxant binding agent 

Mechanism of action:

Sugammadex is a modified γ-cyclodextrin, with a lipophilic core and a hydrophilic periphery. Their three-dimensional structure resembles a hollow truncated cone. The structure has a hydrophobic cavity and a hydrophilic exterior. Hydrophobic interactions trap the drug in the cyclodextrin cavity (the “doughnut hole”), thereby resulting in the formation of a water-soluble guesthost complex. 

unmodified γ-cyclodextrin possesses a larger lipophilic cavity (7.5 to 8.3 Å) than any other cyclodextrin does, it is still not deep enough to accommodate the larger rigid structure of the rocuronium molecule. Therefore, the cavity was modified by adding eight side chains to enlarge the cavity for better accommodation of rocuronium and by adding negatively charged carboxyl groups to enhance electrostatic binding to quaternary nitrogen of rocuronium.

The stability of the rocuronium-sugammadex complex is the end result of an interplay of van der Waals forces, hydrogen bonds and hydrophobic interactions.

Sugammadex exerts its effect by forming very tight complexes in a 1 : 1 ratio with steroidal neuromuscular blocking agents (rocuronium > vecuronium >> pancuronium).

Pharmacokinetics:

Because of the soluble nature of the rocuronium-cyclodextrin complex, urinary excretion becomes the major route of elimination of rocuronium.

Pharmacodynamics:

Sugammadex produces rapid and effective reversal of even more profound rocuronium-induced neuromuscular blockade.

Sugammadex is ineffective against succinylcholine and benzylisoquinolinium neuromuscular blockers such as mivacurium, atracurium, and cisatracurium because it cannot form inclusion complexes with these drugs.

Side effects:

hypotension, coughing, movement, nausea, vomiting, dry mouth, parosmia (an abnormal sense of smell), a sensation of a changed temperature, and abnormal levels of N-acetyl-glucosaminidase in urine

Use: Reversal of rocuronium (ROC) or vecuronium (VEC) induced neuromuscular (NM) block in adults. For routine reversal of ROC-induced block in children and adolescents.

Dose:

Adults:

Routine reversal following ROC- or VEC-induced block:

• 4 mg/kg if recovery has reached at least 1-2 post-tetanic counts (PTC). Median recovery time (T4/T1 = 0.9) ≅ 3 minutes
• 2 mg/kg if recovery has occurred up to at least T2. Median recovery time (T4/T1 =0.9) ≅ 2 minutes
• Immediate reversal of ROC-induced block -16 mg/kg. Median recovery time (T4/T1 = 0.9) ≅ 1.5

Not recommended for immediate reversal of VEC-induced block.

Re-administration of ROC or VEC after sugammadex: A waiting time of 24 hours should be taken into account.