23 – Complications Flashcards
3 broad categories of complications?
- Anesthesia related
- Procedure related
- Patient specific
What are the anesthesia related complications?
- Hypothermia
- Hypotension
- Hypoventilation (hypercapnia)
- Hypoxemia
- Bradycardia
What are some procedure related complications?
- Pain
- Hemmorrhage
What are some specific patient complications for a brachycephalic breed?
- Upper airway obstruction
- Regurgitation/vomiting ->aspiration
- Hyperthermia
What is the normal PaO2 and FiO2?
- PaO2= 80-11mmHg
- FIO2=21%
What is the normal saturation of hemoglobin (SpO2)?
- 97-100%
What values for PaO2 and SpO2 indicate hypoxemia?
- PaO2<60mmHg
- SpO2<90%
What are some causes of hypoxemia and low SpO2?
- Low inspired O2 (FiO2)
- Hypoventilation
- Diffusion problem (pulmonary disease)
- Ventilation perfusion (V/Q) mismatch
- Right to left shunt
What are the clinical effects of mild hypoxemia (SpO2>80%)?
- Activation of SNS
- Increase HR
- Mild hypertension
What are the clinical effects of moderate hypoxemia (SpO2: 60-80%)?
- Local vasodilation ->hypotension
- Reflex increase in HR
What are the clinical effects with severe hypoxemia (SpO2<60%)?
- Local depressant effects predominate
- Rapid decrease in BP ->severe hypotension
- Bradycardia -> ventricular fibrillation or cardiac arrest
What are the consequences of hypoxemia?
- Tissue hypoxia
- Lactic acidosis
- Organ failure
What are the high risk patients for hypoxemia?
- Brachycephalic
- Diaphragmatic hernia
- Pneumothorax, pulmonary contusion
- Upper airway obstruction
- Pneumonia
- Abdominal distance (C-section)
What can you do for high risk patients to hypoxemia prior to anesthisa?
- Pre-oxygenation!
- NO contra-indication to oxygen
What are some causes of hypoxemia?
- Low inspired O2 (FiO2)
- Hypoventilation
- Ventilation perfusion mismatch and intrapulmonary shunting
Low inspired O2 (FiO2)
- Check O2 supply
- Check endotracheal tube
- Check that breathing system is tight to ET-tube
- Airway obstruction: remove or bypass
What is the definition of hypotension (SAP, MAP, DAP)?
- SAP<80mmHg
- MAP<60mmHg
- DAP<40mmHg
What is the minimal acceptable MAP for large animals?
- MAP=70mmHg (myopathy)
What are 3 basic pathophysiological mechanism that lead to hypotension?
- Decreased vascular tone
- Decreased CO
- hypovolemia
What do you do if patient is hypotensive?
- Check depth of anesthesia
- Check HR
- Fluid bolus
- Ephedrine
- Add positive inotrope – dobutamine
- *last resort: add a vasopressor
Check depth of anesthesia
- Decrease vaporizer setting
- Maybe need to administer anesthetic sparing drugs
o Opioid: no CV side effects
Check HR
- Treat bradycardia (1/2 resting HR)
o Can decrease CO - Slow normal HRs do not usually affect CO
- *treatment: atropine, glycopyrrolate
Fluid bolus in hypotension recommendations for cats and dogs
- Cats: 3ml/kg over 15 mins
- Dogs: 5ml/kg over 15 mins
Why give a fluid bolus (crystalloid fluids: isotonic balanced)?
- Increase intravascular volume and improves venous return
- Repeated once if needed
When would you give a colloid bolus?
- If response to crystalloid fluids is inadequate
- Maximum dose 20ml/kg/day
- Pentaspan 6%
When would you give a hypertonic saline (7.5%)?
- 4mL/kg over 10 min (duration 30-120min)
- Blood loss
- Need of rapid volume expansion
Ephedrine
- Synthetic noncatecholamine=stimulates alpha1 and beta1 receptors
- Indirect acting: release of endogenous NE
- Vasoconstrictor/venoconstrictor
- *effects last up to 15mins
Add positive inotrope – dobutamine
- Beta1 agonist=increases myocardial contractility
- Useful for low CO stages in patients with ADEQUATE intravascular volume
- Used as an infustion (short half life)
- Less risk of cardiac arrhythmias
What are 2 options for the last resort of adding a vasopressor
- NE infusions
- Vasopression infustions
NE infusions as a last resort
- Alpha1 constictor
- May dimmish visceral organ perfusion (liver, kidneys)
- Try to limit to emergency use only
- Treatment for refractory hyptension (septic patients)
Vasopressin infusions
- Non-catecholamine vasopressor
- Used for refractory hypotension
- Very sick patents of post cardiac arrest
What are some causes of bradycardia?
- Drugs: alpha2 agonists, opioids
- Deep plane anesthesia
- Hypothermia
- Vagal reflexs (oculo-cardiac reflex)
- Electrolyte imbalance
What are the different forms of bradycardia?
- Sinus bradycardia
- AV block
- Sinus arrest
- Ventricular escape beats
- Asystole (NO P waves)
Tachycardia rates in dogs and cats
- Dog >180bpm
- Cat >200bpm
- *correct the underlying problem
Tachycardia is a sympathetic response to
- Pain
- Awareness
- Hypotension
- Hypoxemia
- Hypercapnia
- Hypovolemia
What do you treat a ventricular premature complex with?
- Lidocaine bolus
What do you treat sinus bradycardia with escape beats?
- Atropine or glycopyrrolate
- *goal is to increase HR as the escape beat is due to slow sinus rate
What are some predisposing factors to regurgitation?
- Brachycephalic breeds
- Drugs relaxing LES (volatiles, opioids, anticholinergics, propofol)
- Increased intra-abdominal pressure: pregnancy, obestity , surger, head-down position
- Prolonged anesthesia
What are some preventative measures for regurgitation?
- Appropriate pre-anesthetic fasting
- Pretreatment with OMEPRAZOLE, maropitant, metoclopramide
- Use of cuffed ET-tube
How do you treat regurgitation?
- Secure airway in unconscious patient: check cuff
- Place suction catheter in esophagus
- Suction refluxate and lavage with tap water
- Instillation of 5-10ml Na-citrate solution
- Check and suction again prior to extubation
- *pantoprazole, famotidine
What does mild hypercapnia (45-60mmHg) cause?
- SNS: tachycardia, mild hypertension
What are the clinical signs that are usually seen when PaCO2>60mmHg?
- Bounding pulses (high systolic, low diastolic)
- Vasodilation: brick red colour, capillary oozing
What are the clinical signs that are seen with sever hypercapnia (PaCO2>90mmHg)
- Severe CNS depression (narcosis)
- Respiratory arrest (depression of brainstem)
What are some causes of hypercapnia?
- Hypoventilation
- Equipment failure
- Endobronchial intubation
- V/Q mismatch
- Apparatus dead-space (overlong ET-tube)
- Increased CO2 production (hyperthermia)
When does hypoventilation occur?
- Respiratory depressant drugs
- Position (dorsal)
- Abdominal distension
- Obesity
What are some equipment failures that can occur that cause hypercapnia?
- Uni-directional (one-way) valves (circle systems)
- CO2 absorber exhausted
- Inadequate fresh gas flow (non-rebreathing system)
What are some way to prevent heat loss?
- Insulation
- Warming mats
- Warm air blankets
- Radiant heat lamps
- Warm IV fluids/irrigation fluids
What are some potential problems with warming devices?
- Patient cannot move away from the source
- Blood flow may no conduct heat away
- Body pushed into heat source
- *always observe and monitor T
- Avoid direct contact to avoid burns
o Use towel for insulation
What are some circumstances where hyperthermia occurs?
- Heavy-coated dogs on circle rebreathing system
- Post op in cats
o If used mu-opioids, ketamine, intra-op hypothermia - Malignant hyperthermia
What is the treatment for hyperthermia?
- Turn of supplemental heat, remove blankets, ice packs
- Water, alcohol to inguinal and axillary regions
- Fans: careful corneal ulcers
- Acepromazine?
What is important with extubation in brachycephalic breeds?
- Late extubation to avoid airway obstruction
- *BE PATIENT
- keep period between extubation and full alertness as SHORT as possible
