Patient care in hospital settings requires coordinated team performance. Studies in other industries show that successful teams adapt their coordination processes to the situational task requirements. This prospective field study aimed to test a new observation system and investigate patterns of adaptive coordination within operating room teams. A trained observer recorded coordination activities during 24 cardiac surgery procedures. The study tested whether different patterns occur during different phases of and between different types of surgical procedures (two-way multivariate ANOVA with repeated measure). A statistically significant increase was found in clinical and coordination activities in phases of the operation with high task interdependence. The highest level of 'coordination via the work environment' (i.e. an implicit coordination mechanism) was recorded during the actual procedure on the beating heart. These findings prove the sensitivity of the observation system developed and evaluated in this study and provide insight into patterns of adaptive coordination in cardiac anaesthesia. This study furthers our understanding of adaptive coordination as a cornerstone of effective team performance in complex work environments. Using a new observation system, it describes patterns employed by health care professionals in response to changing task demands in an acute patient care setting.