12. Preoperative care

Question 1

12. Preoperative care

Answer 1

*planning for and anticipating complications is necessary to minimize the chance of adverse events
*several details require attention:
1.thorough anamnesis
2.full clinical examination
3.laboratory data
4.patient stabilization
5.determination of surgical risk
6.client communication

Preoperative care-anamnesis
-anamnesis vitae
*basic information
*species
*breed
*genetics
*anatomy
*age
*diagnostic tests warranted?
*gender
*lifestyle
*diet, excercise, environment
-anamnesis morbi
*reason for surgery (chief
complaint)
*clinical signs and duration
*past medical problems and
treatments
*current medical problems and treatments
*prior anesthesia
*used drugs,complications,recovery

Anamnesis-breed
-has to be taken into consideration
-anatomical differences vs other genetic predispositions
-some examples:
*brachycephalic breeds
*toy breeds
*giant breeds
*boxers,greyhounds,herding breeds,dobermans,miniature schnauzers etc.

Anamnesis-breed
-brachycephalic breeds
*small hypoplastic trachea, elongated,soft palate,stenotic nares(ahtatunut nenä)
*laryngeal mucous membrane prone to swelling
*increased tonus of n. vagus
*predisposition to gastroesophageal reflux
*higher risk of hypoxia(not enough o2)

Anamnesis-breed
-toy breeds
*hypothermia
*catheter placement
*questionable accuracy of
monitors
*accuracy of drug dosages
*hands-on assessment limited during anesthesia
-giant breeds
*lower drug dosages required
*considered geriatric at a
younger age
*patient handling more difficult

Anamnesis-breed
*herding breeds–mutations in the MDR-1 gene(prolonged effect of some drugs)
*boxers–drug sensitivity(acepromazine)
*greyhounds(+ other sighthounds?)–drug sensitivity,prolonged
recovery from some drugs(propofol,barbiturates)
*other similarly lean-muscled breeds may also appear more sensitive to lipophilic drugs(most anesthetic drugs)
*miniature schnauzers–sick sinus syndrome
*dobermans– abnormal concentrations of von Willebrand factor (73%)
>buccal mucosal bleeding time may be measured

Anamnesis-age
-pediatric(young) and geriatric(old) patients at a higher risk-smaller drug dosages required
-pediatric patients:
*immature organs and defence mechanisms
*prone to hypothermia,hypoglycemia,regurgitation
*blood loss more dangerous
-geriatric patients(old,many diseased):
*reduced response to hypercapnia(too much co2), hypoxemia(low o2 in blood)
*slower metabolism and healing,decreased organ function
*prone to hypothermia,regurgitation

Preoperative care:
clinical examination
↓
diagnostic tests
↓
stabilization:
✓optimizing hemodynamics if possible
✓optimizing respiratory function(also preoxygenation)
✓optimizing hydration status (fluid therapy)
✓preoperative fasting
✓analgesia and sedation
✓thermoregulation
✓positioning

Clinical examination
-benefits of evaluating veterinary patients before general anesthesia
are ofter underestimated
-evaluation of risks and the necessity of further diagnostic tests
-full clinical examination always warranted,but sometimes not
possible

Clinical examination
-cardiovascular system
*heart auscultation
*pulse(peripheral)
*mucous membranes
-respiratory system
*breathing pattern and noises
*lung auscultation
*mucous membranes
*palpation of trachea
-hydration status
*mucous membranes
*skin turgor
*eyes
-gastrointestinal and urinary system
*abdominal palpation
- Integumentary system(yhtenäinen järjestelmä)
*appearance of skin
*signs of inflammation/infection?
-central nervous system
*assessment of mentation
*neurological examination
- BCS(body condition score)
- temperature

Diagnostic tests
*choice of tests depends on the patient(clinical exam)and the owner
*recommended at least– packed cell volume,total protein,glucose,urea
*hematology,biochemistry,urinalysis
*diagnostic imaging(X-R,U/S(ultrasound),MRI,CT)
*further tests(e.g.ECG,blood typing)

Patient stabilization
-all patients should be stabilized prior to sedation if possible
>hemodynamics
>respiratory function
>hydration status
-some emergency patients in critical condition need immediate surgery,but most benefit from preoperative stabilization

Preoperative fasting
-reduced amount of contents in the stomach→reduced possibility of vomiting,gastrointestinal reflux and consequently aspiration
-care should be taken when dealing with(risk of dehydration,
hypoglycemia):
1.pediatric patients
2.cachectic patients
3.concurrent diseases (fever, diabetes, etc. [polyuria])
4.different species
-fasting of 2-4 hours for water and 6-8 hours for food should be
enough in most cases

Sedation and analgesia
-choice of drugs depends on several factors
>patient characteristics (age, breed, concurrent
diseases, etc.)
>expected severity of pain
>surgical procedure
-optimal pain control during and after anesthesia is of critical importance (not all anesthetics provide analgesia!)
-multimodal anesthesia and analgesia are preferred
-both NSAIDs and opioids often used unless contraindicated
-a familiar anesthetic protocol is often the best anesthetic protocol

Oxygenation
-pre-oxygenation(100% oxygen) is
usually warranted before sedation to prevent hypoventilation/hypoxemia
-started before induction and intubation
-usually lasts 3-5 minutes and stopped
immediately before intubation
-administration of oxygen is continued after intubation

Thermoregulation
*hypothermia is the most common complication of anesthesia
*hypothermia may cause hypoxia,prolonged recovery from anesthesia,an increased infection risk,worse cardiovascular
parameters
*warming should be started as soon as possible
*warm room temperature–most effective
*warm water–also effective
*electric heating bags/table–always warranted(perusteltua)
*warm infusions– not very effective (increase by ~0,5C)
*infrared light–not recommended without a folium blanket (may
promote inflammation)

Intraoperative fluid management
-purposes:
>maintenance of hemodynamics
>maintenance of the catheter
>amortization(depletion)of fluid and blood loss
*American Animal Hospital Association guidelines:
>starting dose of 5 ml/kg/h for dogs and 3 ml/kg/h for cats
>can be reduced 25% each hour(unless fluid/blood loss)
*most often used–Ri-Lac or Hartmann’s solution (not NaCl 0,9%)
*in case of hypotension
>crystalloid bolus 10-30 ml/kg for 10-15 min (depending on mean arterial pressure)
>colloid bolus 2-10 ml/kg for 5-10 mins (depending on mean arterial pressure)

Positioning of the patient
*often underestimated,but extremely important
>intubation,catheterization
>procedure,monitoring
>well-being of the patient

Surgical safety checklist
-recommended
-seperate from anesthesia protocol