الفهرس 
Anatomical considerationsOnly 14 pages are availabe for public view
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Abstract
Unilateral spinal anesthesia is a special regional anesthesia technique, generally applied in the orthopedic field for lower limb procedure, where it is more useful and feasible to produce anesthetic block only on the treated side. This technique requires more time and expertise to be successfully produced, but also provide some advantages to the patients, anesthesiologist and nursing staff. Our study was under taken to evaluate the effect of the dose and posture on selective (unilateral) spinal anesthesia with 0.5% hyperbaric bupivacaine for lower limb operations. Our study was carried out on fifty patients :- Patients were allocated to three groups : group C: (control group ):lo patients received (15mg .of 0.5% hyperbaric bupivacaine ) and turned immediately supine. group A: received (10 mg. of 0.5% hyperbaric bupivacaine) and this group subdivided into two equal subgroups (each 10). group Al: The patients stayed in the lateral position for 10 minutes. group A2: The patients stayed in the lateral position for 15 minutes. group B: received (8 mg. of 0.5% hyperbaric bupivacaine) and this group subdivided into two equal subgroups (each 10). Summary and conclusion 8 8 group B1: The patients stayed in the lateral position for 10 minutes. group B2: The patients stayed in the lateral position for 15 minutes. In each patient the following variables were observed Evaluation of sensory and motor blocks on both dependent and non dependent sides; sensory level evaluated by loss of pinprick test while motor block evaluated by using a modified Bromage scale. Then time of regression of sensory level by two segment on dependent side. Heart rate and mean arterial blood pressure tested every 5 min for 30 min. Our results demonstrated that as regarding the sensory block, in the dependent limb, the maximum sensory level was significantly lower level only in groups B1 and B2 (received 8 mg. Bupivacaine) when compared to the conventional spinal anesthesia (group C). On the other hand, in the non-dependent limb, our results demonstrated that, there was a significantly lower sensory level in all groups when compared to the conventional spinal anesthesia (group C). While regarding the motor block in the dependent limb,our results demonstrated that, there was no significant difference in all groups when compared to the conventional bilateral spinal anesthesia (group C). On the other hand, in the non dependent limb, our results demonstrated that, there was a significantly less deeper block in groups (A2,Bl,B2) when compared to the conventional spinal anesthesia (group C). In our study, the sensory loss achieved in the dependent leg was of much higher level than non-dependent leg, some loss of sensation was present in the non-dependent leg, though at a much lower level (in groups Ai,A2,Bi,B2). Similarly assessment of motor block showed some degree of motor block in the non - dependent leg again at a lower level than the dependent side in the same groups. It is evident from our study that even when using a small volume of the drug we can not avoid some spill over effect on the non- dependent side, however hyperbaric local anesthetic solution in reduced volume limits the spread of drug to the non dependent side, which was explained as the distance between the left and right spinal nerve roots is nearly 10-15 mm in the lumber or lower thoracic level such a small distance should reasonably prevent from producing a strictly unilateral block of spinal nerve roots. Also, from the results of our study, we found a significant delay in the time (min.) to reach maximum sensory and motor blockade in the dependent limb in groups B1 and B2 when compared to the conventional bilateral spinal anesthesia (group C) which can be explained by the reduced doses to 8 mg bupivacaine in groups (B1&B2). Also there was a delay in the time to two segment regression of the sensory level (min.1 in the dependent limb, in all groups when compared to the conventional spinal anesthesia (group C) This was probably due to the higher anesthetic concentration achieved near the nerve roots of the operated limb than in the conventional bilateral spinal anesthesia and could also account for the delay in the two segment regression of the sensory level in the dependent limb, probably due to the reduced surface available for absorption and elimination for the subarachnoid space of the local anesthetic molecules. Haemodynamic changes observed in our study can not be ignored. In the conventional spinal anesthesia (group C), we found a significant decrease in the heart rate and mean arterial blood pressure after 5 min. of injection of the drug and all over the studied period when compared to the preoperative value. While in all other groups, there were no significant changes in the heart rate or mean arterial blood pressure all over studied period when compared to the preoperative value. In conclusion : There is no doubt that unilateral spinal anesthesia requires more effort because of the necessity of monitoring the block’s extension repeatedly and modifymg the patient positioning. It also takes longer because the lateral decubitus position has to be maintained for approximately 15min. This matter needs rearrangements in the operating area to be solved. For healthy patients a unilateral block spares the patient’s experience of suffering a drug induces reversible paraplegia and possibly the feeling of helplessness as a result of immobilization. In cardiac risk patients the anesthetist tries to avoid circulatory depression or decompensation. Bilateral sympathetic block can be avoided by unilateral spinal anesthesia, and this technique is presumably of haemodynamic advantage. Unilateral spinal anesthesia has several important advantages including : The expectation of not being totally paralysed during surgery and maintaining the ability to move the untreated limb may improve the well being of the patients during both the onset of the block and after surgery and when the patient is transferred to the ward. Also, the ability to move the untreated limb improves the work of the nursing staff in the recovery area and in the ward. Another important advantage is produced by the use of low doses of local anesthetic and the reduction in intrathecal spread of local anesthetic molecules. It has been demonstrated that unilateral spinal block increases cardiovascular stability, reducing the incidence of clinically relevant hypotension and fastening the resolution of nerve block. In fact, unilateral spinal anesthesia with low doses of hyperbaric bupivacaine has been suggested also for day case procedures reducing the risk for transient neurological symptoms produced by lidocaine spinal anesthesia.