Misc. Topics Flashcards
Best method of preventing heat loss in OR
Forced air warming
Modes of heat loss in OR
Radiation > Convection > Evaporation > Conduction
Body’s temp control is regulated by
Brainstem
Hypothalamus (pre-optic area)
Radiation
#1 source of heat loss (60%) Protect by covering the skin
Convection
20-30% of heat loss
Happens from movement of air over the patient (wind chill)
Evaporation
20% of heat loss
Happens from respiration, wounds, and exposure of internal organs
Conduction
Only 5% of heat loss
Ex- OR table, IV fluids, and irrigation fluids
Phase I of intra-op heat transfer
D/t redistribution of fluids from the central to peripheral compartments
Anesthetic agents cause vasodilation and prevent shivering
Placing warm blankets on the patient BEFORE inducing GA can minimize the peripheral temperature gradient
Phase II of intra-op heat transfer
Heat loss to the environment EXCEEDS heat production
Phase III of intra-op heat transfer
Heat loss to the environment equals heat production (equilibrium)
CV and pharmacologic consequences of hypothermia
CV
- SNS stimulation
- Vasoconstriction + decreased tissue PO2
- Shits O2-Hgb curve to the left
- Coagulopathy and plt dysfunction
- Sickling of HgbS
Pharm:
- Slowed drug metabolism
- Increased solubility of VAs (prolonged emergence)
Shivering and O2 Consumption
Increases O2 consumption by 400-500%!!
- Risk of MI!
Drugs that can be used to treat shivering
Meperidine
Clonidine
Precedex
Steps if Airway Fire
Remove the ETT and stop flow of all gases
Remove anything else combustable from the airway
Pour cold saline into the airway
If fire still isn’t extinguished, use CO2 extinguisher
After fire under control:
1) Go back to ventilating the patient (avoid nitrous and high O2)
2) Check ETT for damage (any fragments missing?)
3) Perform bronchoscopy to look for airway injury or ETT fragments
This med is the gold standard induction med for ECT
Methohexital
3 Drug Induced Hyperthermic Syndromes
1) Neuroleptic Malignant Syndrome
2) Serotonin Syndrome
3) Anticholinergic Poisoning
Cause of neuroleptic malignant syndrome
DA depletion in the basal ganglia and hypothalamus!
From:
- Reglan
- Haldol, etc
S/S of neuroleptic malignant syndrome
1) SEVERE muscle rigidity, muscle necrosis, and rhabdomyolysis, and myoglobinuria.
2) ANS instability
Treatment of neuroleptic malignant syndrome
DANTROLENE!
Bromocriptine
Supportive care
ECT
Cause of Serotonin Syndrome
Excess 5HT in the CNS and PNS
Often due to interaction of:
1) SSRI + meperidine or fentanyl
2) MAOI + meperidine or ephedrine
S/S of serotonin syndrome
- Akathisia (innter restlessness)
- Agitation –> coma
- Muscle rigidity, tremor, and clonus
- Mydriasis
Treatment of serotonin syndrome
Cyproheptadine
Cause of anticholinergic poisoning
Result of excessive Ach blockade in the CNS and PNS
- Atropine and scopolamine
S/S of anticholinergic poisoning
- Delirium
- Mydriasis
- Red, hot, dry skin
Treatment for anticholinergic poisoning
Physostigmine
Why is ketamine avoided in eye surgery?
It can cause rotary nystagmus and blepharospasm (tight closure of eyelids)
Effect on IOP may or may not exist
Effect of sux on IOP
Can increase IOP by 5-15mmHg for 10 minutes. This is not reliably blocked by defasciculating dose!
3 key considerations for strabismus surgery
1) Risk of MH
2) Risk of PONV
3) Risk of OCR
Afferent and efferent pathways of the OCR
Afferent = CN V (Trigeminal) Efferent = CN X (Vagus)
Eye gas bubbles and nitrous
SF6 = No nitrous for 7-10 days
C3F8 = No nitrous for at least a month
TAP blocks are good for surgeries in this distribution
T9-L1
What is a TAP block?
Transverse Abdominal Plane block
- Unilateral block that targets the anterior and lateral abdominal wall.
- Midline incisions and laparoscopic procedures require bilateral blocks
LA is deposited between these two landmarks for a TAP block
Deposited into the fascial plane between the internal oblique and transverse abdominis muscles of the stomach
Complications of TAP block
Peritoneal puncture
Liver hematoma
