Cerebrovascular response of closed head-injured patients to a standardized endotracheal tube suctioning and manual hyperventilation procedure.
The purposes of this research were to assess the cerebrovascular response of closed head-injured patients to a standardized endotracheal tube suctioning/manual hyperventilation (ETTS/MH) procedure and determine if a 5-minute rest period, following the ETTS/MH procedure, was sufficient in length to allow cerebrovascular parameters to return to pre-intervention levels. The sample consisted of 49 head-injured patients, 18 with a baseline mean intracranial pressure (MICP) of 7.1 mm Hg, standard error (SE) .6, and 31 with a baseline MICP of 9.3 mm Hg, SE .6. A total of 145 ETTS/MH procedures were completed, 51 within the lower baseline MICP group and 94 within the higher baseline MICP group. All data were collected within 72 hours of injury using a bedside component of the Hewlett-Packard Patient Monitoring System (H-P PMS). Computer programs written specifically for this research recorded physiologic data at specified points during baseline, throughout the ETTS/MH procedure and during the recovery period. A one-way repeated measures analysis of variance (ANOVA) was used to examine whether significant differences occurred over time during the baseline, intervention and recovery periods for each dependent variable. Significant F statistics were followed by nonorthogonal, multivariate planned comparisons using the Bonferroni posthoc test to identify significant differences between baseline and each 15 second measurement of all physiologic variables during the ETTS/MH procedure and at the end of each recovery minute over a 5-minute period. Independent t tests were used to assess between group differences at each data point throughout the procedure. Findings indicated those patients whose baseline MICP was most elevated demonstrated significantly (p less than .05) lower mean arterial blood pressure, cerebral perfusion pressure, and heart rate in response to the ETTS/MH procedure when compared to those patients with a lower baseline MICP. Additionally, 60 seconds of MH was required in both patient groups following the second and third suctioning catheter pass in order to reverse a step-wise increase in MICP. Finally, at least 2 full minutes of recovery time following the completion of the ETTS/MH procedure were required to allow all measured physiologic variables to return to baseline.