Recovery of blood gases and haematological parameters upon anaesthesia with benzocaine, MS-222 or Aqui-S in the air-breathing catfish Pangasianodon hypophthalmus

Abstract

Fish anaesthesia is used to minimize handling stress and damage during harvesting, transportation, and surgical procedures. Through depression of cardiovascular and respiratory functions, it causes significant changes in blood gases and pH. Here, we present the effects of benzocaine (100 mg l⁻¹), MS-222 (100 mg l⁻¹), and Aqui-S (30 mg l⁻¹) on blood gases and haematological parameters of commercial-sized (≈ 1 kg) striped catfish (Pangasianodon hypophthalmus) and the time course of recovery. Blood was taken through a dorsal aorta catheter immediately after catheterization, and regularly during the following 72 h recovery in aerated water. All anaesthetics caused increases in PCO₂ and lactate resulting in a decrease in pHe, closely mirrored by RBC pHi, as well as a marked rise in Hct, associated with elevated [cortisol] and [glucose] and increased RBC counts but no change in RBC volume, as confirmed by the lack of an adrenergic response of RBC in vitro. All anaesthetics showed similar efficacy and blood parameters were normalized within 24 to 48 h.