a 66 year old female patient underwent a laparoscopic rectopexy under GA for rectal prolapse. GA was maintained with Desflurane, fentanyl in 90% oxygen. Rocuronium was used for muscle relaxation.
Upon induction of anethesia, the patient experienced a brief period of hypotension. Blood pressures dipped into the high 70s systolic. This was treated successfully with 50 mcg of phenylephrine. The patient remained stable until final positioning was reached. Pneumoperitoneum was induced and the surgeon requested steep trendelenburg position. The blood pressure begain to increase from low 100's systolic to a maximum of over ~200/100 mmHg. HR was also elevated. Esmolol (30mg) was given at this time in addition to fentanyl 50 mcg. The patients HR and BP responded to this intervention and remained in the area of ~120's/70's and HR of 80's for the remainder of the case with additional esmolol and then metoprolol boluses. The surgical procedure lasted aproxomately 2 hours after which the patient was extubated and taken to the PACU. Upon removing the drapes and turning on the room lights, it became apparent that the patient's face had numerous small petechiae that were not evident at the beginning of surgery. As far as I can tell, there are no case reports in the literature that describe a similar condition related to extreme trendelenburg positioning.
In the PACU, the patient did not experience any obvious sequelae. She was alert and oriented with no apparent cognitive impairment. Intially blood pressure and HR were normal. However, within one hour, her blood pressure suddenly dropped and she required fluid boluses. This continued for the next 1 hr and it was decided to admit her to the ICU for precautionary measures. Her BP stabilized with fluid boluses (1.5L) but remained in the high 90's systolic to low 100's. Her Hbg came back at 10.1 g/dl down from 13. A repeat one hour later was 11 g/dl. Physical exam was WNL, abdomen soft and non distended, urine was clear at a rate of 30 to 50 cc/hr. Mental status remained unchanged.
Briefly I'll discuss the adverse physiological consequences of patients placed in steep trendelenburg positioning. Then I'll focus on the more common causes of petechiae, with a brief discussion of one likely cause in this case.
Intraocular Pressure and Trendelenburg: IOP is increased by the use of the trendelenburg position and is exacerbated by steep trendelenburg. It is important to remember that the perfusion pressure of the retina is equal to the MAP - IOP; therefore, as IOP approaches 40 mmHg, it is noted that perfusion to the retina begins to suffer and risk of ischemic retinopathy becomes significant. Steep trendelenburg positioning is rarely utilized with open procedures, but is predominantly important in laparoscopic surgery. The pneumoperiteneum can further exacerbate IOP. The paritial pressure of CO2 also rises during laparoscopic surgery, and IOP is increased by hypercarbia. The changes seen to occurr with pCO2 are a result of an increase in CVP, and therefore, this is another parameter that must be considered in steep trendelenburg positioning.
Respiratory system: with increasing degrees of trendelenburg positioning, the abdominal contents press with greater force on the diaphragm and the lungs become less and less compliant, decreasing FRC, and causing atelectasis. Obesity exacerbates this to the point that they often will not tolerate any significant degree of this position. Furthermore, as the lungs and carina move cephalad , the ETT taped in a fixed position may be pushed into the right mainstem bronchus resulting in hypoxemia.
Cardiovascular system: the trendelenburg position causes as an autotransfusion of blood from the lower extremeties to the upper portion of the body due to gravity. Patients without any degree of cardiovascular disease tolerate this additional blood volume easily via increased SV, MAP and contractility per starlings law. However, patients with decreased cardiac reserve, may suffer morbidity from an inability to handle the increase low on the heart. CVP can be a good indicator in these patients. The transfer of blood from the lower extremities to the central venous system is also viewed as beneficial from the surgeons perspective however. Improved blood flow in the lower extremities reduces the chances of venous stasis and deep venous thrombosis, improves surgical visualization and decreases bleeding in deep pelvic procedures.
ICP: The head down position also increases ICP. It is helpful to recall that perfusion pressure to the brain = MAP-ICP or CVP whichever is greater. Since both CVP and ICP increase with a head down position, MAP should be monitored carefully particularly in patients with risk of elevated CVP. However, rotating the head to the right or left causes a far larger increase in ICP due to jugular vein compression and should be carefully avoided when a patient is in the head down position.
Petechiae, as manifestated in our patient, unfortunately are very common to multiple disorders. One common reason that people development petechiae is from thrombocytopenia or platelet defects in general. An exhaustive list is beyond the scope of this article. In the acute perioperative setting there are a few causes that might be considered. Fat emboli syndrome is one in which anesthesiologists think of as it often causes petechiae to occur in a very distinctive distribution over the chest. Fat emboli syndrome is commonly thought to occur in the setting of fractured bones or orthopedic surgerical procedures. However, it can also occur in association with blood transfusion, DIC, Collagen disease, decompression from altitude, infections, medullary reaming, severe and multiple trauma, neoplasm, renal transplantation and liposuction. None of the categories fits our patient very well. Furthermore, her distribution was isolated to the head and face. In a study of volunteers held upside down, petechiae developed around the eyes. This would be far more closely related to our patient. In order to make a diagnosis of fat emboli syndrome, it is important to have at least one of the major criteria and 4 of the minor criteria listed below as published by Gurd and Wilson:
- Petechiae in vest distribution
- CNS depression out of proportion to level of hypoxemia.
- pulmonary edema (via chest x-ray)
- Tachycardia (>110 bpm)
- temp >38.5
- emboli visible in retina
- fat in urine, fat in sputum
- unexplained drop in hematocrit or platelet count
- increasing sed rate.
By virtue of these criteria, it is essentially guaranteed that this woman was not suffering from fat emboli syndrome.
Given that petechiae are common to a large variety of medical conditions, it is critical to consider the context in which they develop.
The development of petechiae in this patient underscores the potential dangers of the steep trendelenburg position. Although there are benefits to the surgeon in terms of visualization and decreased bleeding, these must be weighted against the potential for venous pooling in the head resulting in increaed IOP, ICP, CVP all of which have the potential to cause ischemia to vital organs.