The Effect of Fiberoptic Bronchoscopy on Cerebral Hemodynamics in Patients With Severe Head Injury

The Effect of Fiberoptic Bronchoscopy on Cerebral Hemodynamics in Patients With Severe Head Injury* Joel R. Peerless, MD, FCCP; Norman Snow, MD, FCCP; Matt]. Likavec, MD; Alfred C. Pinchak, MD; and Mark A Malangoni, MD Study objective: Concems exist about the effect of flexible fiberoptic bronchoscopy (FFB) on intracranial pressure (ICP). We studied the effect of FFB on cerebral hemodynamics in patients with severe head injury. Design: Prior to FFB, patients were anesthetized and muscle relaxants were given as necessary to eliminate coughing. Comparisons were made of mean arterial pressure (MAP), ICP, and cerebral perfusion pressure (CPP) prior to, during, and after FFB, as well as comparisons of mean cerebral hemodynamic values in an 8-hour period before and after FFB. Observations were made of changes in neurologic status post-FFB. Setting: Surgical intensive care unit of Levell Trauma Center. Patient population: Fifteen patients with severe head injury in whom ICP was monitored and who required FFB for diagnosis of nosocomial pneumonia or treatment of lobar collapse. Results: Pre-FFB ICP averaged 14.3 mm Hg (range, 6 to 26 mm Hg). During FFB, patients experienced a mean increase in ICP of 13.5 mm Hg above basal values (p=O.OOOI). At peak ICP, MAP increased from a baseline of92.3 mm Hg (SD:±:l6.1) to 111.5 mm Hg (:±:13.9). Mean CPP was 83.7 mm Hg at peak ICP

(range, 52 to 121 mm Hg), a 14.0% increase over baseline. The ICP and MAP retumed to basal levels following bronchoscopy. No patient had a clinically significant increase in ICP or demonstrated any deterioration in Glasgow Coma Scale score or neurologic examination findings post-FFB. Conclusions: Although FFB causes an increase in ICP in patients with severe head injury, MAP also rises, and an adequate CPP is maintained. The ICP retums to basal levels after the procedure. When properly performed, FFB does not adversely affect neurologic status in patients with severe head injury. (CHEST 1995; 108:962-65)

Flexible fiberoptic bronchoscopy (FFB) has been shown to be a useful and safe procedure in mechanically ventilated, critically ill patients. 1· 4 Common indications for performance of FFB in the intensive care unit include airway management, diagnostic maneuvers (airway injuries, sampling of lower respiratmy tract secretions), and treatment of segmental or lobar lung collapse. The performance of FFB in patients with closed head injury raises concerns about the effect of this procedure on intracranial pressure (ICP) and cerebral pe1fusion pressure (CPP), and the possible deleterious effect on cerebral function. Endotracheal tube sue-

tioning,5 respiratory therapy maneuvers, 6 and the use of positive end-expiratory pressure (PEEP) 7 have been shown to increase ICP. While the performance ofFFB has been shown retrospectively to be of low risk in patients with intracranial mass lesions, 8 there is little information describing the effect of FFB on cerebral hemodynamics in patients with severe head injury.9·10 The purpose of this study was to evaluate the effect of FFB on cerebral hemodynamics during and after the bronchoscopic procedure and neurologic sequelae following bronchoscopy.

*From the Departments of Surgery. Anesthesiology, and Neurosmgery, Case Western ReseJVe University at MetroHealth MedicarCenter, Cleveland. Presented in part at the Annual International Scientific Assembly, American College of Chest Physicians, New Orleans, October 31-November 2, 1994. Manuscript received Janu§lry 3, 1995; revision accepted March 17. Reprint requests: Dr. Peerless, MetroHealth Medical Center, 2500 MetroHealth Drive, Cle~;eland, Ohio 44109-1998

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CPP=cerebral perfusion pressure; ETI=endotracheal tube; FFB=flexible fiberoptic bronchoscopy; ICP=intracranial pressure; MAP=mean arterial pressure; PEEP= positive end-expiratory pressure; PSB=protected specimen brushing

Key words: cerebral perfusion pressure; flexible fiberoptic bronchoscopy; intracranial pressure

MATERIALS AND METHODS

Fifteen patients with severe head injury who required FFB either for ruagnosis of nosocomial pneumonia (protected specimen brushing [PSB]) or for treatment of lobar collapse were studied (Table 1). All patients were intubated and mechanically ventilated, and all had ICP monitors (ll0-4BC; Camino Laboratories; San Diego, Calif) in place. Treatment of a patient's increased ICP included varied regimens of hypeJVentilation, sedative agents (morphine, midazolam, and lorazepam), mannitol, and muscle relaxants. Clinical Investigations

Table !-Patient Population* Patient No./ age, yr 1/23 2120

Jump from car

3/31

MCA

4/19

MCA

5n6

Pedestrian vs car

6/21 7/22

GSW to head MVA

8/32 9/19 10/22

Pedestrian vs car MVA MVA

11/16

MVA

12135 13/67 14/19

Bicycle accident MVA MVA

15/32

MCA

50

CT Scan

Mechanism MCA

60

Hemorrhagic contusion, SDH, IVH, moderate shift Hemorrhagic contusion, cerebral edema Hemorrhagic contusion, SDH, SAH Multiple hemorrhagic contusions, SAH Temporal hematoma, SDH, SAH, IVH Cerebral edema Hemorrhagic contusion, SDH, SAH SDH, massive shift SAH, IVH, cerebral edema Intracerebral hematoma, diffuse edema, midline shift Contusions, SDH, SAH, mild edema Multiple contusions, SAH SDH Nonhemorrhagic contusions, diffuse edema Hemorrhagic contusions, mild midline shift

*Age, mechanism of injury, head CT findings (MCA=motorcycle accident; MVA =motor vehicle accident; GSW=gunshot wound; SDH= subdural hematoma; IVH=intraventricular hemorrhage; SAH= subarachnoid hemorrhage). Patients were anesthetized for bronchoscopy using a combination of agents for cerebral protection (thiopental, lidocaine) as well as additional sedatives (morphine, midazolam) supplementing initial ICP management. All patients were given Floz=LO for 5 min prior to bronchoscopy and chemically paralyzed (vecuronium, mivacurium) as necessary to prevent coughing during the procedure. The ventilator rate was adjusted to maintain the patient's preparalysis minute ventilation. Bronchoscopy was performed using a bronchoscope (BF P20D, 5.0 mm ED; Olympus; Melville, NY), through a swivel adapter. Continuous monitoring of oxygen saturation was measured with a pulse oximeter (Nellcor; Hayward, CaliD. Baseline values of mean arterial pressure (MAP), ICP, and CPP (CPP=MAP-ICP) were measured for 5 min prior to beginning FFB, and compared with values obtained during and immediately after the procedure. In addition, mean values of MAP, ICP, and CPP were calculated for an 8-h period prior to bronchoscopy, and compared with similar calculations of these parameters over an 8-h period postbronchoscopy. Comparisons of mean values were analyzed using Students' t test. A p value of :s0.05 was considered significant. This study was approved by the Institutional Review Board of MetroHealth Medical Center. RESULTS

FFB was performed for treatment of lobar collapse in six patients. All patients showed lung expansion on subsequent chest radiographs. Nine patients underwent FFB for suspicion of pneumonia. Four patients had positive PSB cultures that resulted in institution or adjustment of antibiotic therapy. Four patients had

C)

40

I

E 30 E

20

10

OL___

_ L_ _ _ _L __ __ L_ _ _ _~--~--~

8 Hour Pre-Bronch

Immediately Pre-Branch

Peak ICP

Immediately Post-Bronch

8 Hour Post-Bronch

FIGURE l. Intracranial pressure before, during, and after bronchoscopy. Individual patients and mean data::±:SD (bold).

160 140 120 Cl 100 I E 80 E 60 40 20 0

8Hour Pre-Branch

Immediately Pre-Branch

MAP at Peak ICP

Immediately Post-Btonch

8 Hour Post-Branch

FIGURE 2. Mean arterial pressure before, during, and after bronchoscopy. Individual patients and mean data::±:SD (bold).

140 120 100

~ 80 E

E 60

40 20 o~---L----~---L----~--~--~

8 Hour

Immediately

CPP at

Immediately

Pre-Branch

Pre-B(Qnch

Peak ICP

Post-Branch

B Hour Post-Branch

FIGURE 3. Cerebral perfusion pressure before, during, and after bronchoscopy. Individual patients and mean data::±:SD (bold).

negative brush cultures, and antibiotic therapy was withheld or discontinued based on final culture results. Changes in Cerebral Herrwdynamics During Bronchoscopy

Baseline ICP averaged 14.3±6.6 (SD) mm Hg (range, 6 to 26 mm Hg) (Figs 1 through 3). The ICP increased in all patients during FFB, with a mean increase of 13.5±8.8 mm Hg (range, 2 to 31 mm Hg) above baseline values. The ICP increased to a peak CHEST I 108 I 4 I OCTOBER, 1995

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level of 10 to 367% over baseline (mean peak, 114%). At peak ICP, there was a mean increase in MAP from 92.3:±:16.1 mm Hg to 111.5±13.9 mm Hg, and CPP increased from 77.9:±:16.9 mm Hg at baseline to 83.7:±:18.4 mm Hg (range, 52 to 121 mm Hg). All but one patient maintained CPP above 60 mm Hg during the procedure. Both ICP and MAP decreased within minutes following removal of the bronchoscope and restoration of nomial ventilation. Two patients had a marked decrease in MAP (Fig 2) prior to the procedure that was thought to be secondary to use of anesthetic agents, and the hypotension was corrected with fluid administration and the stimulation of bronchoscope insertion. Changes in Cerebral Herrwdynamics Postbronchoscopy

Mean ICP in the 8-h period after FFB was unchanged from a similar period prior to bronchoscopy (15.6:±:7.0 mm Hg vs 16.1:±:7.4 mm Hg) (Figs 1 through 3). Similarly, there was no significant difference in mean values of MAP or CPP after bronchoscopy. Three patients showed statistically, but not clinically, significant increases in ICP in the 8-h post-FFB period (range, 10.7 to 21.8 mm Hg), yet CPP was not significantly changed in these patients. The ICP was unchanged in ten and decreased in two patients in the postbronchoscopy period. CPP was unchanged post-FFB in 11 patients and increased in 2. Two patients had statistically significant decreases in CPP postbronchoscopy, but both maintained CPP at or above 60 mm Hg. The decreased CPP was secondary to decreases in MAP, as both patients had stable ICP postbronchoscopy compared with baseline. Change in Neurologic Status Postbronchoscopy

No patients had neurologic deterioration or change in Glasgow Coma Scale score following bronchoscopy. DISCUSSION

Previous reports have expressed concern over the use of fiberoptic bronchoscopy in Ratients with increased ICP and with head injury.8- 0 In a retrospective study of patients with central nervous system tumors and evidence of increased ICP, there was no evidence of neurologic complications due to FFB; however, cerebral hemodynamics were not measured. 8 There have been brief reports of both transient and sustained increases in ICP during bronchoscopy, yet measurement of CPP was not reported in these studies. 9•10 The present study has quantitated the extent to which ICP increases during bronchoscopy and has demonstrated that ICP returns to normal after completion of the procedure and restoration of normal 964

ventilation. Importantly, MAP also increases during bronchoscopy, and thus CPP is maintained in an acceptable range. Two patients did demonstrate hypotension after administration of anesthetic agents with concomitant decrease in CPP. Both arterial pressure and CPP improved following fluid administration and the stimulation of FFB, and neither patient had obvious neurologic sequelae. The practice of conservative fluid management routinely used to treat head-injured patients may have subjected these patients to hypotension coincident with the administration of vasodilating anesthetic agents. Most patients had return of cerebral hemodynamics to baseline levels after completion of the procedure. No patient had a clinically significant increase in ICP post-FFB, and all patients maintained CPP at or above 60 mm Hg. The cause of increased ICP during FFB may be related to known respiratory effects of performing bronchoscopy through an endotracheal tube (ETT). A decrease in cross-sectional area of the ETT occurs when a bronchoscope is placed for a procedure. Varying levels of tracheal PEEP are created, depending on the size of the ETT through which the bronchoscopy is performed.ll In one study, a mean tracheal PEEP of 10.4 em was attained during bronchoscopy, with a high of 35 em in one patient with a 7.0-mm ETT. No patient with an 8.0-mm ETT had a PEEP level greater than 20 cm.ll We did not observe any correlation between ETT size and percentage increase in ICP. Coughing during FFB may also cause a PEEP effect. The routine administration of muscle relaxants prevented this phenomenon from occurring in our study. The effect on Pco2 that results from performing bronchoscopy through an ETT also may affect ICP. While some reports have shown negligible changes in Pco2 during FFB,12 others have demonstrated large rises in Pco2, commonly occurring during application of suction with resultant decrease in tidal volume and alveolar ventilation.ll Increases in Pco 2 during bronchoscopy may have led to rises in ICP in our patients; however, arterial blood gas values were not measured during FFB in our study. Variable effects on Po2 have been observed during simple bronchoscopy in mechanically ventilated patients.ll-13 Although hypoxemia can cause increases in ICP, all our patients had continuous peripheral oxygen saturation measured during FFB and arterial oxygen saturation was maintained at ;::o:95% in all patients. The maintenance of CPP during FFB and stability of neurologic status and cerebral hemodynamics in the postbronchoscopy period suggest that FFB, when properly performed, does not adversely affect neurologic status in patients with severe head injury. No Clinical Investigations

patients required additional interventions to control ICP in the postbronchoscopy period. In summary, performance of FFB in patients with severe head injury may cause a rise in ICP, but CPP is maintained within acceptable levels, and hemodynamic values return to baseline following resumption of normal ventilation. Continuous monitoring of cerebral hemodynamics and arterial oxygen saturation is recommended, so that the procedure can be interrupted if unacceptable changes in ICP, CPP, or Sa02 occur. Patients should be adequately anesthetized and paralyzed with muscle relaxants to prevent coughing during the procedure. The largest possible ETT size should be used to minimize the PEEP effect that can result from placement of the bronchoscope in the ETT. Hypotension secondary to anesthetic agents should be anticipated in this population of patients and appropriate intravenous fluids should be available for immediate administration. REFERENCES

1 Dellinger RP, Bandi V. Fiberoptic bronchoscopy in the intensive care unit. Crit Care Clin 1992; 8:755-72 2 Olopade C. Prakash U. Bronchoscopy in the critical-care unit. Mayo Clin Proc 1989; 64:1255-63

3 Jolliet PH, Chevrolet JC. Bronchoscopy in the intensive care unit. Intensive Care Med 1992; 18:160-69 4 Bellomo R, Tai E, Parkin G. Fibreoptic bronchoscopy in the critically ill: a prospective study of its diagnostic and therapeutic value. Anaesth Intensive Care, 1992; 20:464-69 5 Rudy E , Turner B, Braun M, et a!. Endotracheal suctioning in adults with head injury. Heart Lung 1991; 20:667-74 6 Moraine J, Brimioulle S, Kahn R. Effects of respiratory therapy on intracranial pressure. J Crit Care 1991; 6:197-201 7 Lochini S, Montolivo M, Pluchino F, eta!. Positive end-expiratory pressure in supine and sitting positions: its effects on intrathoracic and intracranial pressures. Neurosurgery 1989; 24: 873-77 8 Bajwa M. Henein S, Kamholz S. Fiberoptic bronchoscopy in the presence of space-occupying intracranial lesions. Chest 1993; 104:101-03 9 Snow N, Lucas A. Bronchoscopy in the critically ill surgical patient. Am Surg 1984; 8:441-45 10 Lee T. Fiberoptic bronchoscopy and intracranial pressure. Chest 1994; 107:1909 11 Lindholm CE, Oilman B, Snyder J, et al. Cardiorespiratory effects of flexible fiberoptic bronchoscopy in critically ill patients. Chest 1978; 74:362-68 12 Matsushima Y, Jones R, King E, et a!. Alterations in pulmonary mechanics and gas exchange during routine fiberoptic bronchoscopy. Chest 1984; 86:184-88 13 Trouillet JL, Guiguet M, Gibert C, eta!. Fiberoptic bronchoscopy in ventilated patients: evaluation of cardiopulmonary risk under midazolam sedation. Chest 1990; 97:927-33

RECENT ADVANCES IN RESPIRATORY MEDICINE January 9 - 11, 1996; Cairo, Egypt Sponsored by the Egyptian Chapter of the American Collge of Chest Physicians. For information, please contact: Tarek Safwat, MD, FCCP; Governor ACCP Egyptian Chapter, Medical Tower, 55 Abdel Menem Reyad Street, Mohandseen. Cairo, Egypt. Tel: 202-258-1383; Fax: 202-266-0717

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