The influence of halothane and nitroprusside on canine spinal cord hemodynamics

The effect of milrinone on induced hypotension in elderly patients during spinal surgery: a randomized controlled trial

BACKGROUND CONTEXT

Induced hypotension is widely used intraoperatively to reduce blood loss and to improve the surgical field during spinal surgery.

PURPOSE

To determine the effect of milrinone on induced hypotension during spinal surgery in elderly patients.

STUDY DESIGN/SETTING

Prospective randomized clinical trial.

PATIENT SAMPLE

Forty patients, 60 to 70 years old, ASA I-II, who underwent elective lumbar fusion surgery.

OUTCOME MEASURES

Intraoperative hemodynamics, blood loss, hourly urine output, and grade of surgical field.

METHODS

All patients were randomized to group M or N. The study drug was infused after perivertebral muscle retraction until complete interbody fusion. In group M, 50 μg/kg/min of milrinone was infused over 10 minutes as a loading dose followed by 0.6 μg/kg/min of milrinone as a continuous dose. In group N, an identical volume of normal saline was infused in the same fashion. This study was not funded by commercial or other sponsorship and the authors confirm no conflicts of interest, financial or otherwise.

RESULTS

During infusion of the study drug, the systolic and mean blood pressures were maintained within adequate limits of induced hypotension in group M. Intraoperative blood loss was 445.0±226.5 mL in group M and 765.0±339.2 mL in group N (p=.001). Hourly urine output was 1.4±0.6 mL in group M and 0.8±0.2 mL in group N (p<.001). The grade of the surgical field was better in group M than in group N (p=.004).

CONCLUSIONS

We conclude that milrinone is useful for induced hypotension in elderly patients during spinal surgery.

Major intraoperative neurologic deficits in pediatric and adult spinal deformity patients. Incidence and etiology at one institution

STUDY DESIGN

A retrospective study of 1,090 patients undergoing corrective spinal deformity surgery for scoliosis (n = 920), kyphosis (n = 77), or a combination of the two (n = 93) at one institution.

OBJECTIVES

To ascertain the etiologies and incidence of neurologic deficits occurring at the time of surgery.

SUMMARY OF BACKGROUND DATA

Potential etiologies of intraoperative neurologic deficits include cord compression, overdistraction, purely vascular, or a combination.

METHODS

The study group included only patients with useful function of their lower extremities and normal bowel and bladder control, and patients whose surgeries were in spinal cord territory as opposed to purely cauda equina territory.

RESULTS

There were four major neurologic deficits that occurred during surgery. Three of the four deficits were purely vascular in etiology. The fourth may have had a vascular and mechanical etiology. All four patients had anterior and posterior surgery with harvesting of the unilateral convex segmental vessels, and each had a component of hyperkyphosis, as well as intraoperative controlled hypotension. All four patients showed marked improvement of motor weakness with time.

CONCLUSIONS

Significant risk factors were combined anterior and posterior surgery (P = 0.009) and hyperkyphosis (P = 0.0006).

Simultaneous laser-doppler flowmetry of canine spinal cord and cerebral blood flow: Responses to $$Pa_{CO_2 } $$ and blood pressure changes

We observed the relative changes of both spinal cord blood flow (local SCBF) and local cerebral blood flow (local CBF) using independent laser-Doppler flowmeters (LDF) in 12 dogs under N2O(50%)-O2-enflurane(1.0%) anesthesia. The dorsal surface of the lumbar spinal cord and the parietal surface of the brain were partially exposed. Two fine LDF probes were placed between the exposed surfaces and the dura maters at each site. Both local SCBF and local CBF decreased simultaneously with hyperventilation and increased with hypoventilation within several seconds. The local SCBF responses to PaCO2 changes were similar in direction and degree as those of the local CBF. Autoregulation of local SCBF to arterial blood pressure (ABP) changes was abolished, though that of the local CBF was still recognized in a blunted fashion within a mean ABP range of 50 to 150 mmHg.