You simply need to specify the table so instead of ${IP_Address} use ${Nodes.IP_Address}
Sorry GLE... I had a typo... below is an example of an APM alert that we have in place. It should be ${Node.IP_Address} not ${Nodes.IP_Address}
Component Name = ${ComponentName}.Application Name = ${ApplicationName}.Process Name = ${ProcessName}.Service Name or Process = ${ProcessName}.Service Status = ${ComponentStatus}.Node Name = ${NodeName}.Machine Type = ${Node.MachineType}.Operational Status = ${Node.Operational_Status}.Device role = ${Node.Device_Role}.IP Address = ${Node.IP_Address}.Last reported boot = ${Node.LastBoot}.City = ${Node.City}.State = ${Node.State}.Business Hours = ${Node.Business_Operational_Hours}.Maintenance Window = ${Node.Maintenance_Window}.Support Contact = ${Node.Support_Contact}.Business Owner = ${Node.Business_Owner}.System Manager = ${Node.System_Manager}.