Insensible fluid loss
Insensible routes of fluid loss are those that are not readily observed and include the loss of fluid through the respiratory tract during respiration and loss of fluid by sweating. Dogs and cats sweat minimally through their foot pads so most insensible losses are through the respiratory tract. The fluid lost during breathing is close to pure water and does not contain many solutes (a hypotonic loss). The basal loss of water through breathing is about: 10-15 ml/lb/day. High environmental temperatures, fever and activity result in increased insensible losses.