Skeletal muscle blood flow in anaesthetized horses. Part II: effects of anaesthetics and vasoactive agents.

This research review evaluates studies on how anesthesia affects blood flow in skeletal muscles and cardiovascular function in horses, aiming to understand the causes and prevention of muscle complications post-anesthesia. Limited published data primarily refers to halothane and isoflurane anesthetics and their effects, highlighting the significance of maintaining adequate blood pressure and muscle blood flow during anesthesia for optimal muscle health.

Effects of Anaesthesia on Skeletal Muscle Blood Flow

• The review focuses on understanding how anaesthesia impacts the blood flow in the skeletal muscles of horses. The phenomenon is pivotal as changes in blood flow during anaesthesia can lead to post-anaesthetic myopathy, a condition manifesting as muscle pain, swelling, or weakness post-anesthesia.
• There is a paucity of published research on this specific topic. The available information primarily discusses the effects of halothane and isoflurane, two commonly used anaesthetics in veterinary medicine.
• The study underscores the crucial role of maintaining adequate arterial blood pressure, perfusion pressure, and muscle blood flow during the administration of anaesthesia to prevent post-anaesthetic myopathy.

Role of Vasoactive Drugs

• Vasoactive drugs, which influence the diameter of blood vessels, and thereby the blood flow, have mostly been studied in the context of halothane-anaesthetized horses.
• The review emphasizes the need for more studies in this area, as interpreting the effects of different vasoactive agents could help form more preventive strategies against post-anaesthetic myopathy.

Importance of Perfusion Pressure

• The study iterates the necessity of maintaining adequate perfusion pressure, particularly for overcoming the detrimental effects of high pressure within muscle compartments (intra-compartmental pressure) in dependent muscles and fluid pressure (hydrostatic pressure) in non-dependent muscles.
• Dependent muscles, usually the lower limbs, can bear more weight and subsequently higher pressure when a horse is anaesthetized, potentially affecting the blood flow in these muscles. Similarly, the non-dependent muscles, located higher and affected by gravity less directly, also demand adequate perfusion pressure to counterbalance the hydrostatic pressure and ensure efficient muscle blood flow.