Download RUNNUNG HEAD: CONTROLLED HYPOTENSION Controlled

RUNNUNG HEAD: CONTROLLED HYPOTENSION
Controlled Hypotension During Shoulder Arthroscopy
Kam Campus, RN, BSN, SRNA
Wolford College
2013 A
[email protected]
1
RUNNUNG HEAD: CONTROLLED HYPOTENSION
2
Controlled hypotension is often utilized during anesthesia of orthopedic
procedures. During the procedure, the anesthetist electively lowers the patient’s mean
arterial pressure (MAP). According to Morgan, Mikhail, and Murray the MAP is
lowered approximately 50-60 mmHg in healthy individuals. There are multiple positive
effects of controlled hypotension. Choi and Samman demonstrated in a systematic
review that controlled hypotension reduces blood loss. Furthermore, the study
demonstrated no organ was hypoperfused using controlled hypotension.
HB was a 6’0”, 109 kgs, 61 years old, Caucasian male. He presented with a left
shoulder impingement syndrome requiring left shoulder arthroscopy with subcromial
decompression. The patient presented from home into outpatient surgery. He was
generally healthy; coexisting diseases were hyperlipidemia, cigar use and environmental
allergies, which were well controlled with medications. Lab values were not significant
for this patient as his CBC was in normal limits. On evaluation, the patient denied any
significant history. He stated that his activity level was steadily declining over the past
year and that his pain was increasing with sports. Thus, he presented to his surgeon for
repair of his shoulder. The patient had natural and intact teeth, MP 2, TMD >3 fb, mouth
opening >3cm, and FROM of the neck. ASA II was selected for this patient.
In the OR, ASA monitors were applied; the patient was preoxygenated with 10L
of O2 via facemask prior to induction. Fentanyl 100mcg, 1% Lidocaine 50mg, Propofol
300mg IV were administered. Upon loss of verbal and eyelid response, the patient was
successfully bag-mask ventilated, which was followed with Succinylcholine 100mg IV.
Using the MAC 3 blade, a #8.0 ETT was successfully inserted. Sevoflurane was started
with volume control ventilation. Patient was positioned in the beach-chair position with
RUNNUNG HEAD: CONTROLLED HYPOTENSION
3
all pressure points padded and the head secured. Pre-operatively the patient’s BP was
133/83. Following induction, the BP decreased to 120/60. The patient’s BP was further
decreased with the use of Sevoflurane at 3% and Nitrous at 2 L, which decreased the BP
to 90/65 with a MAP of 73. In this case controlled hypotension was appropriately
maintained with anesthetic gases. No antihypertensives were necessary or utilized.
Emergence from anesthesia proceeded when the case concluded without complications.
The patient met the criteria necessary for awake extubation such as airway reflexes intact
and ability to follow commands. He was suctioned then extubated and transferred to
PACU.
The purpose of this case study is to explore the use of controlled hypotension and
the various methods that may be utilized. The rationale for utilizing this anesthetic
technique includes minimization of blood loss, better visualization of the operative site,
and decreased need for a blood transfusion. There are several relative contraindications
concerning the use of this technique such as severe anemia, CAD, hypovolemia, renal or
hepatic insufficiency, PVD, history of a CVA, pregnancy, uncontrolled hypertension, and
history of spinal cord compression.
Most surgical patients arrive in the pre-operative area intravascularly depleted
related to their NPO status. Therefore it is imperative to ensure that your patient receives
appropriate fluid replacement required for hourly maintenance, NPO deficit, and third
space losses. The central methods of controlled hypotension include positive pressure
ventilation, use of antihypertensive drugs, and proper positioning (elevation of the
surgical site to reduce the pressure at the wound). It is vital to ensure adequate perfusion
to the tissues and the brain. Healthy individuals usually tolerate a 40-50mmHg decrease
RUNNUNG HEAD: CONTROLLED HYPOTENSION
4
in MAP without significant complications. However, hypertensive patients have a
rightward shift of the autoregulation curve and may only tolerate a 20-30% decrease in
MAP. Cerebral blood flow remains regulated as long as the MAP is greater than
50mmHg.
Numerous intravenous agents may be used to lower blood pressure. The most
common intravenous antihypertensives include nitroglycerine, sodium nitroprusside
(SNP), hydralazine, and adrenergic blockers. Because of the quick onset and half-lives,
nitroglycerine and SNP they are commonly used and are easily titratable. Be aware that
vasodilators produce reflex tachycardia (increasing the oxygen demand of the heart, thus
should be avoided), tachyphylaxis and intrapulmonary shunting may occur. SNP takes
immediate effect however it produces a toxic metabolite, Cyanide, and is associated with
“coronary steal” syndrome. Hydralazine is a direct arteriolar vasodilator. It has a slower
onset of action than nitroglycerine and SNP but lasts 2-4 hours. Hydralazine is
associated with increased cardiac output but it also is associated with a reflex tachycardia,
sodium and water retention and a Lupus like syndrome. Esmolol is a B1 blocker that is
associated with a rapid onset and eight-minute half-life, which provide ease of titration.
Esmolol should not be used with heart failure, severe bradycardia, or AV blocks. In this
specific case, the use of Sevoflurane and positive pressure ventilation were utilized to
adequately control the blood pressure. Sevoflurane is a potent vasodilator and positive
pressure ventilation increases the intrathoracic pressure and reduces venous return, mean
arterial pressure and cardiac output. A comprehensive patient evaluation including
patient’s comorbidities, type and duration of surgical procedure should be considered
when determining the anesthetic plan.
RUNNUNG HEAD: CONTROLLED HYPOTENSION
Reference
Choi, W. & Samman, N. (2008). Risks and benefits of deliberate hypotension in
anesthesia: a systematic review. IOMS. 37(8) pp687-703.
Morgan, GE., Mikhail, MS., & Murray, MJ. (2006). Clinical anesthesiology. (4th ed.).
New York, NY: McGraw‐Hill.
5