Anesth Analg 2003;97:1198-1199
© 2003 International Anesthesia Research Society
LETTERS TO THE EDITOR
Hypotensive Technique and Sitting Position in Shoulder Surgery
Salvatore Sia, MD
Department of Anesthesiology, Centro Traumatologico Ortopedico, Azienda Ospedaliera Careggi, Firenze, Italy
To the Editor:
I read with great interest the article by Bhatti and Enneking (1) about an unusual case of visual loss and ophthalmoplegia after shoulder surgery. The authors analyzed various potential contributing factors but concluded that the exact etiopathogenesis of the clinical findings remains unexplained.
I think that the most likely cause was a severe and prolonged cerebral hypoperfusion. The gravitational effect of patient’s position on arterial blood pressure (BP) has been overlooked. In fact, after placement in the sitting position (90 degrees upright), patient’s head was at least 60 cm above the NiBP cuff placed at the ankle. BP is reduced by 0.77 mm Hg for each centimeter of gradient.
At the request of the surgeon, a value of 100 mm Hg systolic BP was maintained for 98 min. Therefore, the value of mean arterial pressure (MAP) at patient’s head was lower than the lowest value of MAP at which the autoregulation of cerebral blood flow (CBF) is still in force, particularly in a patient with uncontrolled hypertension, which curve for autoregulation of CBF is shifted to the right (2).
We shouldn’t adjust BP at the surgeon’s request, especially when a sitting position is used, without taking into account the adequacy of cerebral perfusion.
References
- Bhatti MT, Enneking FK. Visual loss and ophthalmoplegia after shoulder surgery. Anesth Analg 2003; 96: 899–902.[Abstract/Free Full Text]
- Van Aken H, Miller ED. Deliberate hypotension. In: Miller RD, ed. Anesthesia. 5th ed. New York: Churchill Livingstone, 2000: 1470–90.
Response
M. Tariq Bhatti, MD, and
F. Kayser Enneking, MD
Departments of Ophthalmology, Neurology, Neurosurgery, Anesthesiology, Orthopedics, and Rehabilitative Medicine, University of Florida College of Medicine, Gainesville, FL
In Response:
We thank Dr. Sia for his interest in our article and his insightful comments. Although we have given considerable and careful thought to why our patient developed his postoperative ophthalmic complications, we have still not been able to confidently attain an exact explanation. However, we agree with Dr. Sia that severe and prolonged cerebral hypoperfusion may have played a significant role. We acknowledged in our discussion that placement of the sphygmomanometer cuff on the distal lower extremity may have had a role in underestimating the patient’s arterial blood pressure while he was in the sitting (modified beach chair) position. Maintaining adequate cerebral perfusion during surgery is critical, and the correlation Dr. Sia describes between arterial blood pressure at the level of the head and the dependent location of the blood pressure cuff is something all anesthesiologists should keep in mind, and possibly avoid, when involved in cases requiring an upright position. As a result, we have changed our practice and place the noninvasive cuff on the arm. In addition, we have encouraged our surgical colleagues who request hypotensive anesthesia for shoulder arthroscopy to use the lateral position rather than the beach chair position, particularly for elderly hypertensive patients. It is interesting to note that there is not a single investigation in the literature examining the relationship between arthroscopic visualization and systolic blood pressure. This type of study would help support or dispel the notion of "required hypotension" in this elderly often hypertensive patient population. Again, we thank Dr. Sia for highlighting this important point from our report.
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