R1iv / 15B02: Describe the consequences of mild hypothermia in the early post

15B02: Exam Report

Describe the consequences of mild hypothermia in the early post-operative setting.

35% of candidates passed this question.

A well organised answer would provide details on domains of physiology, pharmacology and “other”, such as patient centred effects. Few answers mentioned pharmacology. Providing a definition of “mild” was often overlooked but doing so assisted a focused answer. Many answers spread beyond “mild” hypothermia or address the “causes” rather than the consequence – neither of which gained marks as they were not answering the question asked.

R1iv / 15B02: Describe the consequences of mild hypothermia in the early post-operative setting

Defintion:  Mild Hypothermia = core body temp 32-25 C

Physiological

Pharmacological

NEURO

  • ↑CBF & CMRO2 7% per 1°C
  • Cerebral depression
  • ↓MAC

A

  • ↓absorption due to reduced gut motility

CVS

  • SNS stimulation ↑circulating catecholamines = ↑afterL
  • ↑HR
  • ↑↓CO & MAP
  • ↑workload can cause myocardial ischaemia
  • ECG: prolonged PR, 1HB, J waves

D

  • propofol has prolonged effect due to ↓intercompartmental clearance

RESP

  • Increased MV
  • Cold induced brochorrhoea
  • Abnormal ciliary function
  • Depressed cough reflex

M

  • ↓hepatic drug clearance
  • Impaired Hoffman degradation

GI

  • ↓GI motility = Ileus

E

  • ↓renal blood flow = ↓ drug elimination

RENAL

  • Cold diuresis; peripheral VC → central hypervolaemia → ↓ADH secretion → diuresis

PD

  • ↓drug-receptor interactions
  • NMBD = ↓onset/offset
  • Slow to wake

HAEM

  • L) shift ODC → ↓O2 delivery
  • ↓WCC, platelets 2 sequestration in spleen
  • ↑bloods viscocity
  • Coagulopathy at 34°C

METABOLIC

  • ↓BMR 6% for ↓1°C
  • ↓O2 consumption
  • ↑BSL 2 insulin secretion

MSK

  • Shivering
  • ↑O2 consumption

IMMUNO

  • Immune suppression
  • ↓O2 delivery to tissues
  • ↑wound infection and delayed wound healing

ACID/BASE

  • ↑pH
  • ↑gas solubility