Effects of anemia and hypotension on porcine optic nerve blood flow and oxygen delivery

Lorri A. Lee, Steven Deem, Robb W. Glenny, Ian Townsend, Jennifer Moulding, Dowon An, Miriam Treggiari, Arthur Lam

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

BACKGROUND: Perioperative ischemic optic neuropathy occurs after major surgical procedures, which are often associated with hypotension, anemia, or venous congestion. However, the effects of these conditions on optic nerve (ON) blood flow are unknown and cannot be studied adequately in humans. METHODS: Farm-raised pigs were anesthetized with isoflurane, kept normocapnic and normothermic, and subjected to conditions of euvolemic or hypovolemic hypotension (mean arterial pressure 50-55 mm Hg), anemia (hematocrit 17%), venous congestion, and combinations thereof. Control animals were kept euvolemic and normotensive for the entire experiment. Fluorescent microspheres were used to measure cerebral blood flow (CBF) and ON blood flow at baseline and after experimental conditions, and to calculate oxygen delivery (DO2). RESULTS: No significant changes in CBF or ON blood flow or DO2 occurred with euvolemic hypotension (n = 5), compared with controls (n = 12). Hypovolemic hypotension (n = 4) resulted in stable CBF and cerebral DO2, but significant reductions in ON DO2 (P = 0.032). The significant increase in CBF associated with anemia (n = 6) resulted in stable cerebral DO2. In contrast, ON blood flow did not significantly change with anemia, with (n = 5) or without (n = 6) euvolemic hypotension, resulting in significant reductions in ON DO2 (P <0.01). CONCLUSION: Compensatory mechanisms for porcine CBF maintain stable DO2 under specified conditions of hypotension or anemia, whereas ON compensatory mechanisms were unable to maintain blood flow and to preserve DO2. The authors conclude that the porcine ON is more susceptible to physiologic perturbations than the brain.

Original languageEnglish (US)
Pages (from-to)864-872
Number of pages9
JournalAnesthesiology
Volume108
Issue number5
DOIs
StatePublished - May 2008
Externally publishedYes

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Cerebrovascular Circulation
Optic Nerve
Hypotension
Anemia
Swine
Oxygen
Hypovolemia
Hyperemia
Ischemic Optic Neuropathy
Isoflurane
Microspheres
Hematocrit
Arterial Pressure
Brain

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine

Cite this

Lee, L. A., Deem, S., Glenny, R. W., Townsend, I., Moulding, J., An, D., ... Lam, A. (2008). Effects of anemia and hypotension on porcine optic nerve blood flow and oxygen delivery. Anesthesiology, 108(5), 864-872. https://doi.org/10.1097/ALN.0b013e31816c8a30

Effects of anemia and hypotension on porcine optic nerve blood flow and oxygen delivery. / Lee, Lorri A.; Deem, Steven; Glenny, Robb W.; Townsend, Ian; Moulding, Jennifer; An, Dowon; Treggiari, Miriam; Lam, Arthur.

In: Anesthesiology, Vol. 108, No. 5, 05.2008, p. 864-872.

Research output: Contribution to journalArticle

Lee, LA, Deem, S, Glenny, RW, Townsend, I, Moulding, J, An, D, Treggiari, M & Lam, A 2008, 'Effects of anemia and hypotension on porcine optic nerve blood flow and oxygen delivery', Anesthesiology, vol. 108, no. 5, pp. 864-872. https://doi.org/10.1097/ALN.0b013e31816c8a30
Lee, Lorri A. ; Deem, Steven ; Glenny, Robb W. ; Townsend, Ian ; Moulding, Jennifer ; An, Dowon ; Treggiari, Miriam ; Lam, Arthur. / Effects of anemia and hypotension on porcine optic nerve blood flow and oxygen delivery. In: Anesthesiology. 2008 ; Vol. 108, No. 5. pp. 864-872.
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N2 - BACKGROUND: Perioperative ischemic optic neuropathy occurs after major surgical procedures, which are often associated with hypotension, anemia, or venous congestion. However, the effects of these conditions on optic nerve (ON) blood flow are unknown and cannot be studied adequately in humans. METHODS: Farm-raised pigs were anesthetized with isoflurane, kept normocapnic and normothermic, and subjected to conditions of euvolemic or hypovolemic hypotension (mean arterial pressure 50-55 mm Hg), anemia (hematocrit 17%), venous congestion, and combinations thereof. Control animals were kept euvolemic and normotensive for the entire experiment. Fluorescent microspheres were used to measure cerebral blood flow (CBF) and ON blood flow at baseline and after experimental conditions, and to calculate oxygen delivery (DO2). RESULTS: No significant changes in CBF or ON blood flow or DO2 occurred with euvolemic hypotension (n = 5), compared with controls (n = 12). Hypovolemic hypotension (n = 4) resulted in stable CBF and cerebral DO2, but significant reductions in ON DO2 (P = 0.032). The significant increase in CBF associated with anemia (n = 6) resulted in stable cerebral DO2. In contrast, ON blood flow did not significantly change with anemia, with (n = 5) or without (n = 6) euvolemic hypotension, resulting in significant reductions in ON DO2 (P <0.01). CONCLUSION: Compensatory mechanisms for porcine CBF maintain stable DO2 under specified conditions of hypotension or anemia, whereas ON compensatory mechanisms were unable to maintain blood flow and to preserve DO2. The authors conclude that the porcine ON is more susceptible to physiologic perturbations than the brain.

AB - BACKGROUND: Perioperative ischemic optic neuropathy occurs after major surgical procedures, which are often associated with hypotension, anemia, or venous congestion. However, the effects of these conditions on optic nerve (ON) blood flow are unknown and cannot be studied adequately in humans. METHODS: Farm-raised pigs were anesthetized with isoflurane, kept normocapnic and normothermic, and subjected to conditions of euvolemic or hypovolemic hypotension (mean arterial pressure 50-55 mm Hg), anemia (hematocrit 17%), venous congestion, and combinations thereof. Control animals were kept euvolemic and normotensive for the entire experiment. Fluorescent microspheres were used to measure cerebral blood flow (CBF) and ON blood flow at baseline and after experimental conditions, and to calculate oxygen delivery (DO2). RESULTS: No significant changes in CBF or ON blood flow or DO2 occurred with euvolemic hypotension (n = 5), compared with controls (n = 12). Hypovolemic hypotension (n = 4) resulted in stable CBF and cerebral DO2, but significant reductions in ON DO2 (P = 0.032). The significant increase in CBF associated with anemia (n = 6) resulted in stable cerebral DO2. In contrast, ON blood flow did not significantly change with anemia, with (n = 5) or without (n = 6) euvolemic hypotension, resulting in significant reductions in ON DO2 (P <0.01). CONCLUSION: Compensatory mechanisms for porcine CBF maintain stable DO2 under specified conditions of hypotension or anemia, whereas ON compensatory mechanisms were unable to maintain blood flow and to preserve DO2. The authors conclude that the porcine ON is more susceptible to physiologic perturbations than the brain.

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