Anesthetic Complications: 7 Flashcards
Predictable complications
hypoventilation
hypoxemia
hypotension
Hypoventilation
insufficient elimination of CO2 from body relative to CO2 production
reduction in alveolar minute ventilation/VA
respiratory acidosis can occur
monitored by PCO2 during ventilation
35-45 mmHG
(blood gas or ETCO2)
Hypercapnia
PaCO2 greater than 45 mmHg
hypoventilation
Hypoventilation causes
dead space
increase RR/TV
factors that decrease TV
abdominal distention
obesity
thoracic pain
factors increase dead space
malfunction/missing one way valve improper CO2 absorbent cracked inner tube coaxial circuit too many adapters between ET tube and hose Not using a septum in Y piece ET tube extending past the incisors
Rebreathing CO2
can lead to hypercapnia
exhausted CO2 absorbant
malfunctioning scavenging system
inadequate O2 flow rates (non rebreather)
elevated CO2
hyperventilation or rebreathing of CO2
Hypoventilation
monitor Co2
most common complication of anesthetized patients
giving a breath 1-2 times a minute will likely prevent hypoventilation
If PaCo2 approaching 60 mmHg
(hypoventilation)
intermittent positive pressure ventilation should be started a controlled RR and TV
assess depth not excessive
ensure one way valves function/no cracks/fresh CO2 absorbent
Keep dead space to a minimum
hypoventilation
using appropriate length ET tube
not use more than one adapter
if patient less than 3KG use pediatric size
make surgeon is not leaning/resting instruments on thorax
Hypoxemia
reduced O2 concentration in blood
insufficient amount of O2 in arterial blood to meet body’s metabolic demands
Hypoxemia monitoring
predicted Pa02 is approx. 4-5 times the inspired O2 concentration
100% O2
Pa02 400-500mmHG
Pa02 less than 60mmHg is severe
less than ideal oxygen
02 100% and Pa02 80-400mmHg
ventilation to perfusion inequality
V/Q mismatch
ventilation and blood flow are mismatched at the level of the alveoli
inefficient gas exchange between lungs and pulmonary blood
most common cause of reduced 02 in an anesthetized patient
positioning patient in dorsal recumbency or in head down position for longer periods of time
V/Q ratio less than 1
perfusion is occurring but ventilation is not
atelectasis and bronchial intubation
V/Q ratio greater than 1
dead space ventilation
ventilation is present but perfusion is not
“Wasted ventilation”
thromboembolism
severe hypovolemia
hypotension
Diffusion impairment
hypoxemia cause
prevents the normal uptake of 02 from alveoli and pulmonary capillary blood
pulmonary edema
interstitial pneumonia
pulmonary fibrosis
rarely primary cause of hypoxemia in animals
Anatomical shunts
congenital heart abnormalities-blood shunted from right side of heart to left without passing through lungs (not oxygenated)
tetralogy of Fallout
reversed patent ductus arteriosus
ventricular septal defects
are not responsive to 02 therapy
Severe hypoventilation
can lead to elevated c02 level
significant dilution of partial pressure of 02 in alveoli and lead to hypoxemia
post operative period when breathing room air -concern
respond to 02 therapy easily
Low inspired 02
human error:
running out 02 during procedure
using too low 02 flow rate
using nitrous oxide too high concentration combined with 02
Hypoxemia prevention
pre-oxygenated 3-5 minutes prior to induction
100% 02 regardless of inhalant agent
minimize anesthesia and surgery time
check 02 source
calculate 02 flow rate for type of anesthesia
Hypoxemia with 100% 02
increased peak airway pressure
hold positive pressure in lungs 3-5 seconds (can decrease cardiac output)
Positive end expiratory pressure
use bronchodilator (albuterol)
Hypotension
below normal arterial blood pressure
MAP less than 60 mmHg or SAP less than 80 mmHg
Hypotension monitoring
oscilometric or doppler techniques
systolic only with Doppleer
mean only with arterial catheter
Hypotension causes
inhalants-depress cardiovascular system
reduced blood hypovolemia/hemorrhage
inadequate volume administration or replacement
dehydration
vascular tone reduction
shock
sepsis
histamine release
hypotension prevention
balanced anesthesia approach keep inhalant concentration to a minimum provide IV crystalloid fluid ensure adequate fluid volume adequate heat source
Hypotension treatment
turn down vaporizer if too deep 5-20 ml/kg bolus crystalloid fluid hypertonic saline 4-6ml/kg dogs, 2-3ml/kg cats inotropes: dopamine and dobutamine norepinephrine, ephedrine, etc.
Absolute Hypovolemia
loss of intravascular volume
results when intravascular fluid losses exceed gains
Relative Hypovolemia
increase in intravascular space due to loss of vasomotor tone (vasodilation)
normal intravascular volume but larger space to occupy
Hypovolemia monitoring
monitor circulating blood volume and tissue perfusion: pale mucous membranes prolonged CRT thready pulse quality cool/cold temp tachycardia hypotension
scarcely perceptible pulse
commonly rapid
feels like a fine mobile thread/cord under palpating finger
Hypovolemia
monitoring
PCV-low/anemia
TP-low/hypoproteinemia
Lactate-greater than 2mmol/L/poor tissue perfusion
Urine Output-less than 0.5mL/Kg/hr poor perfusion/hypovolemia
Central venous pressure-low <0cmH20 or decreased CVP hypovolemia
absoute
(Hypovolemia) causes
acute hemorrhage trauma
water or electrolyte loss
plasma loss
relative
(Hypovolemia)
causes
adverse drug reactions
sepsis
anaphylaxis
caution Acepromazine
Hypovolemia prevention
crystalloid fluids
5 ps
multiple peripheral IV catheters and central line
Hypovolemia
treatment
normal blood loss 10-20%, greater than 20% needs immediate treatment
replacement crystalloid fluids shock 90-90ml/kg dogs 40-60ml/kg cats 3:1 ratio of blood loss 1/4 total volume as bolus
Colloid therapy
restore oncotic pressure
if TP is <3.5 g/dL
Hypertonic saline
rapid, low volume resuscitation uncontrolled hemorrhage
short lived effects
4-6ml/kg dogs, 2-3 ml/kg cats
contraindications: severe dehydration, cardiac disease, hypernatremic
PCV<20% or TP <3.5 g/dL
whole blood: 25% circulating blood lost
packed RBC: PCV<20% but TP adequate
PCV adequate but TP <3.5 g/dl
fresh frozen plasma<1 year: coagulation
fresh frozen plasma>1 year: hypoproteinemia, coagulation, restore plasma proteins
hemaglobin based oxygen carrier
Hypothermia
below normal body temp
101-102.5F
a decrease of just 2 degrees can have adverse effects
Hypothermia classification
mild: 90-99 F
moderate: 96-98 F
severe: 92-96 F
critical <92F
Hypothermia
monitoring
every 15-20 minutes
Hypothermia causes
heat loss (vasodilation in anesthetic agents) large surgical incisions (fur clipping) prolonged anesthesia/surgery cold surgical scrub (water or alcohol) cool/cold saline abdominal avage cold operating table cool ambient environment
Hypothermia
prevention
warm room
blankets/bair hugger
IV fluid warmer
wrap extremities
Hypothermia
No-Nos
use electric heating pads=thermal burns
use fluid bags/bottles with a towel
Hypoglycemia
below normal glucose levels
normal glucose levels
70-120 mg/dL
below 60 mg/dL=immediate treatment
hypoglycemia
caution
watch for in pediatric, diabetic, hepatic, portal systemic shunt, insulinoma, septicemia, endotoxemia
Hypoglycemia
consequences
coma
hypotension
prolonged recovery from anesthesia with depression, weakness, or seizures
at risk patients monitored
prior to induction
every 30 minutes intraoperative
postoperative
Hypoglycemia treatment
dextrose added to their IV fluid therapy 2.5%-5$
Hyperthermia
above normal body temperature
Hyperthermia causes
excessive heat source fever bactrial infection contamination of IV fluids/drugs malignant hyperthermia syndrome triggered by stress loss of CNS temperature regulation Thyrotoxicosis Pheochromocytoma cats given pure mu opioid disassociate agents (ketamine, etc)
Hyperthermia
prevention
treatment not instigated until 105.8 F
turn off heat sources use cooler fluids apply alcohol to inguinal and axillary and paws use fan provide 02
do not use ice packs or submerge in water can cuase vasoconstriction
Hyperventilation
excessive elimination of c02 from body
leads to hypocapnia
Hyperventilation monitoring
Pac02 less than 35mmHg
less than 25 mmHg severe cerebral vasoconstriction and brain ischemia
Hyperventilation causes
inadequate anesthetic depth or response to pain
overzealous ventilation
significant hypoxemia leading to hypoxic drive
hyperthermia
low inspired oxygen concentrations
increased c02 production
Hyperventilation
prevention/treatment
administer analgesic drugs
decrease TV/RR
supplemental 02
Hypertension
above normal arterial blood pressure
Awake patients hypertension
MAP 120mmHg
SAP>160mmHg
DAP>95mmHg
general anesthesia
hypertension
MAP>100mmHg
Severe and Chronic
hypertension
SAP>180mmHg
DAP>120mmHg
cause damage to eyes, kidneys, heart, brain, and peripheral vessels
monitoring equipment
hypotension and hypertension the same
causes hypertension
pain inadequate depth hypercapnia anesthetic drugs (ketamine, telazol, Xylazin, Dexmetatomadine) can cause a transitory increase in blood pressure renal disease, hyperadrenocoricism, hyperthyroidism, diabetes mellitus, heart failure, pneochomocytoma anemia fever metabolic acidosis cushings/intracanial pressure
treatment: hypertension
administer additional analgesics
assess anesthetic depth (too light?)
keep C02 normal range
Esmolol (beta adrenergic antagonists)-if already taking then Phenoxybenzamine
Apnea
temporary cessation of breathing
causes: apnea
rapid admin of induction (propofol, ketamine/diazepam, thiopental)
overdose of anesthetics
cardiopulminary arrest
equipment (pop off valve, ventilator malfunction)
treatment: apnea
place ET tube ventilate provide 02 assess depth-too light? inspect machine and ventilator begin CPR
Barotrauma
excessive peak airway pressure during positive pressure ventilation that results in lung injury
causes: barotrauma
closed pop off valve
improper ventilator settings
manometer above 20cm h20
using flush valve when non rebreathing circuit attached
treatment: barotrauma
thoracocentesis to correct pneumothorax
provide 02
check pulse and begin CPR
postoperative myopathy
damage done to skeletal muscles likely due to hypoperfusion and ischemia after a period of recumbency
causes: postoperative myopathy
common large dogs incorrectly positioned on surgical table
treatment: myopathy
provide support/padding for limbs
IV fluid therapy, analgesic drugs, sedatives, physical therapy
prolonged recovery causes
hypoventilation hypercapnia hypoxemia metabolic acidosis hypoglycemia hypotension hypothermia hepatic and renal disease overdose of anesthetic drugs
prolonged recovery treatment
balanced anesthesia
correct underlying condition
provide supplemental 02
provide fluid therapy
reversible agents: opiods
opioid overdose=use butorphanol
reversible agents: Alpha 2
Dexmedatomine, xylaxine, Romifidine=use yohimbe, antisedan, tolozine
reversible agents: Benzodiazepines
Diazepam, Midazolam, Zolazepam=use Flumazenil
reversible agents:
Phenothiazines
Acepromazine, Promazine=no reversal agent
