The effect of maternal hypothermic cardiopulmonary bypass on fetal lamb temperature, hemodynamics, oxygenation, and acid-base baance

Giorgio Pardi, Maria M. Ferrari, Fiore Iorio, Fabio Acocella, Veronica Boero, Nicola Berlanda, Ario Monaco, Claudio Reato, Francesco Santoro, Irene Cetin

Research output: Contribution to journalArticlepeer-review


Objective: To evaluate fetal-maternal temperature relationship and fetal cardiovascular and metabolic response during maternal hypothermic cardiopulmonary bypass in pregnant ewes. Methods: Cardiopulmonary bypass was instituted in 9 pregnant ewes, reaching 2 different levels of maternal hypothermia: 24°C to 20°C (deep hypothermia) in group A (5 cases) and less than 20°C (very deep hypothermia) in group B (4 cases). Hypothermic levels were maintained for 20 minutes, then the rewarming phase was started. Fetal and maternal temperature, blood pressure, heart rate, electrocardiogram, blood gases, and acid-base balance were evaluated at different levels of hypothermia and during recovery. Results: Fetal survival was related to maternal hypothermia: all group A fetuses survived, while 2 of 4 fetuses of group B in which maternal temperature was lowered below 18°C died in a very deep acidotic and hypoxic status. Maternal temperature was always lower than fetal temperature during cooling; during rewarming the gradient was inverted. The start of cardiopulmonary bypass and cooling was associated with transient fetal tachycardia and hypertension; then, both fetal heart rate and blood pressure progressively decreased. The reduction of fetal heart rate was of 7 beats per minute for each degree of fetal cooling. Deep maternal hypothermia was associated with fetal alkalosis and reduction of PO 2. Very deep hypothermia, in particular below 18°C, caused irreversible fetal acidosis and hypoxia. Conclusions: Deep maternal hypothermic cardiopulmonary bypass was associated with reversible modifications in fetal cardiovascular parameters, blood gases, and acid-base balance and therefore with fetal survival. On the contrary, fetuses did not survive to a very deep hypothermia below 18°C.

Original languageEnglish
Pages (from-to)1728-1734
Number of pages7
JournalJournal of Thoracic and Cardiovascular Surgery
Issue number6
Publication statusPublished - Jun 2004

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Surgery


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