title: Reduced cerebral perfusion on sudden immersion in ice water: a possible cause of drowning.
abstract: BACKGROUND
  Near-drowning incidents and drowning deaths after accidental immersion in open waters have been linked to cold shock response. It consists of inspiratory gasps, hyperventilation, tachycardia, and hypertension in the first 2-3 min of cold-water immersion. This study explored the immediate changes in cerebral blood flow velocity (Vmean) during cold-water immersion since cold shock induced hyperventilation may diminish Vmean and lead to syncope and drowning.
  
  
  METHODS
  There were 13 male volunteers who were lowered into a 0 degrees C immersion tank for 30 s. Vmean in the middle cerebral artery (MCA) was measured together with ventilatory parameters and heart rate before, during, and after immersion.
  
  
  RESULTS
  Within seconds after immersion in ice water, heart rate increased from 74 +/- 16 to 107 +/- 18 bpm (mean +/- SD; p < 0.05). Immersion was associated with a marked elevation in respiratory rate (from 16 +/- 3 to 38 +/- 14 breaths x min(-1)) and tidal volume (883 +/- 360 to 2292 +/- 689 ml). The end-tidal carbon dioxide tension decreased from 38 +/- 4 to 26 +/- 5 mmHg and MCA Vmean dropped by 43 +/- 8%. Signs of imminent syncope (drowsiness, blurred vision, loss of responsiveness) were shown by two subjects (MCA Vmean dropped 62% and 68%, respectively).
  
  
  CONCLUSIONS
  Following ice-water immersion, hyperventilation induced a marked reduction in MCA Vmean to a level which has been associated with disorientation and loss of consciousness.
authors.affiliation: Bispebjerg Hospital Research Unit for Anaesthesia and Intensive Care, Copenhagen, Denmark. temantoni@hotmail.com
authors.forename: Teit
authors.initials: T
authors.lastname: Mantoni
authors.forename: Bo
authors.initials: B
authors.lastname: Belhage
authors.forename: Lars M
authors.initials: LM
authors.lastname: Pedersen
authors.forename: Frank C
authors.initials: FC
authors.lastname: Pott
mesh_terms: D000328:Adult; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003080:Cold Temperature / Q000009:adverse effects*; D004332:Drowning / Q000209:etiology*; D006801:Humans; D007035:Hypothermia / Q000209:etiology*; D007053:Ice / Q000009:adverse effects*; D007101:Immersion / Q000009:adverse effects*; D008297:Male; D010200:Panic; D011446:Prospective Studies; D012307:Risk Factors; D013997:Time Factors; D014867:Water / Q000009:adverse effects*
chemical_list: D007053:Ice; D014867:Water