Ruptured AAA

Question 1

66-year-old woman undergoing laparotomy for rupture AAA. Prolonged surgery and blood loss of about 4L. Core temperature has dropped to 35°C.

Define perioperative hypothermia?

How to measure core temp Intraoperative?

Risk factors?

Q3: What risk factors contributed to the patient low temperature?

Answer 1

Perioperative hypothermia: Under anesthesia hypothermia is defined as a core temperature less than 36°C.
Hypothermia in general < 35

Pulmonary artery catheter → gold standard, measures blood temperature directly.
Distal esophageal probe → reliable during general anaesthesia.
Bladder catheter with thermistor → accurate if urine output is adequate.
Rectal probe → invasive but can lag behind rapid core changes.

• Major surgery
• Exposed surgery
• Massive blood transfusion
• Combined general and regional anesthesia
• Preoperative temp less than 36°C

Increased Heat Loss
1. Radiation: Heat loss to cold objects/surfaces in the operating theatre.
2. Evaporation: From open surgical wounds and skin preparation fluids.
3. Conduction: Direct transfer of heat to cold operating table, instruments, and infusion fluids.
4. Convection: Air currents in the operating room removing heat from skin surface.

🔹 Loss of Warm Fluids
5. Massive blood transfusion (cold stored blood).
6. Blood loss and hypovolemia → reduced perfusion and heat distribution.

🔹 Effects of Anesthesia
7. Volatile anesthetics and cold anesthetic gases → cooling effect.
8. Muscle relaxants → loss of shivering response.
9. Reduced muscle activity and metabolic rate → ↓ heat production.
10. Vasodilation from anesthesia → increased heat loss from core to periphery.

Question 2

Give one potential intraoperative problem that may arise as a result of hypothermia in this patient?

Complications of hypothermia?

Answer 2

Coagulopathy, cardiac arrhythmia and myocardial ischemia

• Cardiovascular: decreased cardiac output (anaesthetized), arrhythmias, vasoconstriction, ECG abnormalities (increased PR interval, wide QRS complex)

• Respiratory: increased pulmonary vascular resistance and V/Q mismatch, decreased ventilator drive. Increased gas solubility

• Renal: decreased renal blood flow and glomerular filtration rate, cold diuresis.

• Hematological: reduced platelet function and coagulation, increased fibrinolysis, increased hematocrit, left shift of oxygen dissociation curve.

• Metabolic: reduced basal metabolic rate, metabolic acidosis, insulin resistance, hyperglycemia.

• Gastrointestinal / hepatic: reduced gut motility.

• Neurological: reduced cerebral blood flow, impaired conscious state leading to coma.

Question 3

How to prevent hypothermia

of blankets used in hypothermia

Answer 3

PreOp:

• Avoid prolonged fasting
• Do not do induction unless core temp is 36 .0°C
  # IntraOp:
• Theatre temp. Is maintained at 21°C
• Avoid prolonged surgery
• Warm IV and irrigation fluids are used
• Patient exposed only as needed
  # PostOp
• Pt should not leave the recovery room to the ward until core temp is above 36 .0°C
• Bair Hugger™ System

• Space blankets
• Blizzard blankets
• Wool blankets
• Heat pockets

Question 4

What is DIC

Q9: look for the blood results, what can you see?

Q10: Cause of DIC in this patient?

Q11: How to treat coagulopathy in this patient?/Treatment of DIC?

Q12: What else can assist in correcting this patient’s bleeding?

Who to involve in care?

Q7: With whom you should discuss this patient intraopertivley?

Q16: Indications of platelet transfusion?

Shelf life?

Q14: Stages of hemostasis?

Answer 4

• Coagulopathy and anemia.

Severe hemorrhage, massive blood transfusion, hypothermia

FFP, platelets, cryoprecipitates

Actively warm the patient by fluid warmer, forced hot air (Bair Hugger®)
Consider agents such as tranexamic acid

Hematology consultant
Anesthesia consultant

• Anesthesia consult
• Hematologist: to prepare warmed blood

Platelet loss, consumption, dysfunction, any cause of thrombocytopenia, e.g. <50 × 10 9, disseminated intravascular coagulation (DIC) and post-cardiopulmonary bypass.

5 days

1- Contraction of blood vessel
2- Formation of platelet plug
3- Formation of fibrin by coagulation cascade.

Question 5

How does vascular surgery interfere with each of these 3 phases?

Which factors will be deficient in stored blood?

what is ASA3 and its relation to hypothermia?

Answer 5

If surgeon removes section of vessel, vascular contraction will be impaired
Formation of platelet plug will be impaired by thrombocytopenia and hemodilution
Fibrin formation will be reduced because clotting factors will be diluted by massive fluid transfusions

Factor V and VIII

ASA: American Society of Anesthesia
ASA3: patient with severe systemic disease.
ASA is a grading system of a patient’s physical status from I to VI, used for perioperative risk stratification.
ASA I-VI = healthy → mild disease → severe disease → life-threatening disease → moribund → brain-dead (E = emergency).
Higher ASA score = higher risk of intraoperative hypothermia due to
impaired thermoregulation and longer, more invasive surgeries.

Question 6

Measures to reduce blood loss intra-operative / Intra-operative measures to reduce need for transfusion apart from prevention of hypothermia?

What is Autologous blood transfusion?

What is massive blood transfusion?

Complications of massive blood transfusion?

Early post-operative complications of AAA repair?

Answer 6

1. Good surgical hemostasis and minimally invasive techniques.
   
   2. Anesthetic measures like controlled hypotension, normothermia, and positioning.
   3. Pharmacological agents such as tranexamic acid.
   4. Blood conservation methods like cell saver or hemodilution.

Recovering blood lost during surgery and re-infusing it into the patient.

Replacement of more than 50% of the patient’s blood volume in 12-24 hours

• Fluid overload • Hypothermia
• Electrolyte disturbances: hyperkalemia due to K + leakage from the stored RBC’s, Acid base disturbance
• Hypocalcemia due to chelation of Ca +2 by citrate
• ARDS (TRALI) (Transfusion Related Acute Lung Injury)
• Thrombocytopenia: stored blood has decreased number of functioning platelets
• Coagulopathy: stored blood rapidly loses functions of the labile factors V and VIII
• Multi-organ failure

• Organ failure • Continued hemorrhage • Limb ischemia • MI • Stroke
• Abdominal compartment syndrome • Bowel ischemia • Spinal cord ischemia