IV REGIONAL ANESTHESIA -- BIER BLOCK

Bier block is for arm anesthesia in which local anesthetic is injected into venous system below an occluding tourniquet.
TECHNIQUE :-

1. A small -gauge iv plastic catheter is inserted in the arm to be blocked on the dorsum or the hand. A pneumatic tourniquet is applied over the upper arm.
2. The arm is elevated to promote venous drainage. An elastic bandage may be applied to produce further exsanguination. After exsanguination, the tourniquet is inflated to 2.5 times the patient"s systolic blood pressure and is tested for adequate occlusion of the radial pulse.
3. 50 ml of 0.5% lidocaine is injected. Epinephrine should not be added to the local anesthetic solution
4. If surgery is expected to extend beyond 1 hour, the canula can be left in place and reinjected after 90 minutes.
5. Beyond 45 minutes of surgery, many patients experience discomfort at the level of tourniquet. Double cuff tourniquets can be used to avoid this problem. The proximal cuff is inflated first, allowing anesthesia to be induced in the area under the distal cuff. Both cuffs should be tested before starting and proper sequence for inflation and deflation meticulously followed.

• If surgery is completed in less than 20 minutes, the tourniquet is left inflated for at least that total period of time.

• If 40 minutes have elapsed, the tourniquet can be deflated as a single maneuver.
• Between 20 and 40 minutes, the cuff can be deflated, reinflated immediately and finally deflated after one minute to delay the sudden absorption of local anesthetic int0 systemic circulation, although this may not lower the eventual peak levels achieved.
• The duration of anesthesia is minimal beyond the time of tourniquet release.
  

DISADVANTAGES :-
There is significant risk of systemic toxicity of local anesthetic.

PRECAUTIONS :-

1. Tourniquet should be tested carefully.
2. Local anesthetic should be injected slowly.
3. Systemic blood levels are time dependent and careful attention should be paid to the sequence of tourniquet release and to patient"s monitoring during this period.
4. A separate iv site for injection of resuscitation drugs is needed as well as ready availability of all appropriate resuscitative equipment.

Bier block is one of the most effective and reliable technique if carried with all the above mentioned precautions.

TREATMENT PLAN OF ALLERGIC RESPONSE DURING ANESTHESIA

                                               Allergic responses during anesthesia are not that rare and can be life threatening. Airway maintenance, 100% oxygen administration, intravenous volume expansion, and epinephrine are essential to treat the hypotension and hypoxia that result from vasodilation, increased capillary permeability and broncho spasm. All patients who have experienced an anaphylactic reaction should be admitted to an intensive care unit for 24 hours of monitoring because manifestations may recur after successful treatment.

INITIAL THERAPY:-

1. Stop administration of antigen.
2. MAINTAIN AIRWAY AND ADMINISTER 100% OXYGEN:- Profound ventilation-perfusion abnormalities producing hypoxia can occur with anaphylactic reactions. Always administer 100% oxygen with VENTILATORY SUPPORT as needed. 
3. DISCONTINUE ALL ANESTHETIC DRUGS:- Inhalational anesthetic drugs are not the broncho dilators of choice in treating broncho-spasm after anaphylaxis especially during hypotension. These drugs interfere with the body"s compensatory responses to cardiovascular collapse. Halothane sensitizes the heart to epinephrine.
4. VOLUME EXPANSION:-  Hypovolemia rapidly follows during anaphylactic shock. Initially 2 to 4 liters of lactated ringer"s solution, or colloid or normal saline should be administered, keeping in mind that an additional 25-50 ml/kg may be necessary if hypotension persists.
5. ADMINISTER EPINEPHRINE:- Epinephrine is the drug of choice because :-

                                a) Alfa adrenergic effects vasoconstrict to reverse hypotension.
                                b) Beta-2 receptor stimulation helps in broncho dilation.
                                c) It inhibits mediator release by increasing cAMP in mast cells and basophils
           In hypotensive patients, 5-10 micro gram boluses of epinephrine should be administered I/V to restore BP. Additional volumes and incrementally increased doses of epinephrine should be administered until hypotension is corrected. 0.1 to 1.0 mg of epinephrine should be given in patients with cardiovascular collapse. Patients with laryngeal edema without hypotension should receive S/C epinephrine.
SECONDARY TREATMENT:-

• ANTIHISTAMINES :- 0.5-1 mg/kg of diphenhydramine may be useful in  treating acute anaphylaxis. H1 antagonists available for parenteral administration may have ANTI-DOPAMINERGIC effects and should be given slowly to prevent precipitous hypotension potentially hypovolemic patients.
• CATECHOLAMINES :- Epinephrine infusions may be useful in patients with persistent hypotension or bronchospasm after initial resuscitation. DOSE - 5-10 micro grams /min and titrated to correct hypotension. Nor epinephrine is also given in doses of 5-10 micrograms/min.
• BRONCHODILATORS
• CORTICOSTEROIDS:- They are often administered as adjuncts to therapy when refractory bronchospasm or refractory shock occurs after resuscitation therapy.Recommended dose of hydrocortisone is 0.25-1 g I/V. Alternately 1-2 g of methyl prednisolone 30-35 mg/kg I/V may be useful. Administering corticosteroids after an  anaphylactic reaction may attenuate the late phase reactions reported to occur 12-24 hours after anaphylaxis
• AIRWAY EVALUATION:- Persistent facial edema suggests airway edema. The trachea of these patients should remain intubated until the edema subsides.
• REFRACTORY HYPOTENSION:- Vasopressin may attenuate pathologic induced vasodilation

Assessment Of Airway

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AIRWAY ASSESSMENT

Management of the airway in all groups of patients, whether spontaneously breathing or ventilated, unconscious or awake, is one of the corner stone of the anesthetic practice. There is no substitute for experience based on sound theoretical knowledge.
Assessment of airway is paramount in every patient, whether it is the intention to give a general, regional or local anesthetic because complications can occur in the most unexpected way. The combination of unable to ventilate/unable to intubate is a dreaded complication during administration of anesthesia.
To avoid this situation the assessment of airway, preparation of equipment and plan in case of difficult airway is desirable.

LARYNGOSCOPY AND INTUBATION IS EASIER IF:

1. Patient can open his or her mouth and protrude the tongue to enable the whole of the uvula and posterior pharyngeal wall to be seen.
2. If interdental distance at incisors is equal to or greater than 3.5 cm.
3. If he or she can easily adopt "sniffing the morning air" position (neck flexion with extension of the head)
4. If he or she can protrude the lower mandible beyond the maxilla .
5. If he or she has normal head and neck anatomy and normal dentition or completely absent upper and or lower dentition.
   
6. If he or she is not grossly obese.

DIFFICULT INTUBATION IS SUGGESTED BY:

1. History of previous difficult intubation..
2. High palate with crowded teeth.
3. Loose teeth and small mouth
   
4. Reduced mouth opening with small interdental distance
5. Large protuberant upper teeth
6. Receding chin/short mandible.
7. Immobile neck with restricted head movement.
8. Obesity.
9. A short or bull neck
10. A larynx that does not fall normally on swallowing.

THYROMENTAL DISTANCE:

• This is the distance between the upper border of the thyroid cartilage and bony point of chin.
• Short distance indicates an anterior larynx.
• A distance of about or greater than 7 cm is associated with easy laryngoscopy.

MALLAMPATI / SAMSON-YOUNG CLASSIFICATION OF OROPHARYNGEAL VIEW:
Here, the anesthesiologist sits in front of the patient and ask him to open his mouth and stick his tongue out:

• Class 1- Uvula, faucial pillars and soft palate are visible
• Class 2- Faucial pillas and soft palate are visible
• Class 3- Soft palate and hard palate are visible
• Class 4- Only the hard palate is visible

If the faucial pillars, soft palate, posterior pharyngeal wall are visible, laryngoscopy will probably not be difficult. If only the hard palate is visible, it probably be difficult.

CONCLUSIONS:

1. "Not able to ventilate/Not able to intubate" though occurs rarely, but it can endanger the life of patient and put the anesthesiologist in the most difficult times of his carrier.
2. So, the assessment of airway in every patient is a MUST and should NEVER be ignored.
3. CAPNOGRAPHY and OXIMETRY are the MOST DESIRABLE monitors in the difficult airway patients.
4. When difficulty arises, ADEQUATE OXYGENATION of patient is the MOST IMPORTANT OBJECTIVE.
5. Never hesitate to call for help in a difficult situation.
   

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