Improvement in peripheral perfusion in peripheral vascular disease cases with epidural morphine.
Epidural morphine as a method of pain relief in acute and chronic pain is now being used with remarkable success. In our series, while studying the analgesic effect of epidural morphine in cases of peripheral vascular disease (PVD) of distal type, it was noticed that (while producing analgesia) there was increase in skin temperature and improvement in clinical condition of the patient. Here we present data on 17 cases of 1'VD patients studied in detail to investigate the effect of epidural morphine on peripheral perfusion.
Seventeen cases of peripheral vascular disease of distal type (proved angiographically, block distal to femoral vessel) due to smoker's arteritis were included in this study. Selection of patients and conventional treatment given to them is already mentioned earlier
Clinical presentation of these 17 patients is given in [Table 1] and [Table 2].
In addition to the conventional treatment all the patients were given i.v. lomodex (500 ml) with xanthinol nicotinate (000 mg each day for 5 days). This was followed by lumbar sympathectomy in 7 cases (Group I). The initial response to lumbar sympathectomy was good with increase in peripheral blood flow by 5-10%. However, the response was short lived and pain reappeared within 10 days. The peripheral blood flow also reverted to pre-operative level.
Epidural morphine was administered to these patients as the traditional lire of treatment failed to alleviate pain and improve the condition of the wound.
The study was conducted in two groups. Group I consisted of 12 patients who were administered 2 mg morphine in 10 ml saline in the L3-L4 epidural space. Group II was a control group consisting of (a) 3 patients given 2 mg morphine intravenously and (b) 2 patients given 10 ml of normal saline in L3-L4 epidural space.
Following parameters were studied in both the groups. Clinical assessment was done before, and on the 1st, 4th and 10th day after administration of drug.
Parameters of assessment
(i) Pain-% and duration of relief of pain. (ii) Increase in warmth in the lower extremity. (iii) Wound healing and granulation tissue.
(b) Skin temperature: This was measured by using electro-thermometer before and 5, 15, 30 minutes after the administration of drug in both the superior and inferior extremities.
(c) Blood flow: Impedance plethysmography was used to measure peripheral blood flow in the thigh, leg and foot, just before, and 30 minutes and 24 hours after drug. Blood volume per 1000 ml of tissue per beat was found by Kubieck's formula, where it is inversely proportional to the change in imperdance:
Blood volume = 1 x dz x T x1000)
/beat/1000 ml tissue
Zo = basal impedance in ohms
dz = amplitude of the wave form.
T = left ventricular ejection time. Change in impedance was measured using electrical impedance plethysmography*
Despite standard drug treatment and surgical measures, all the patients had rest pain, which interfered with their sleep and normal activity. In patients with vascular ulcers, amputation stump and gangrene (after excision), the wound had pale granulation tissue and healing was poor.
Results of epidural morphine injections are given in [Table 1] and [Fig. 1], [Fig. 2] and [Fig. 3]. Following epidural morphine there was an immediate increase in the blood flow and also in the skin temperature by 2°C [Figs. 1], [Fig. 2] and [Fig. 3] in the inferior extremity (p < 0.05) and 1°C in the superior extremity (not significant).
Clinically all the patients had relief of rest pain within 2 minutes of epidural morphine administration and the effect lasted for 2 to 6 weeks. There was an immediate increase in warmth felt by the patient mainly in the inferior extremity and the wounds developed petechial hemorrhages. Pale granulation tissue turned to healthy granulation tissue in ulcer and amputation stump patients and the line of demarcation formed in one case of gangrene. Improvement in wound healing occurred within 4-10 days.
Group II: Neither 2 mg morphine i.v. nor 10 ml of normal saline injected epidurally produced any effect on the skin temperature or blood flow. There was no relief of rest pain and no improvement in other clinical parameters studied.
The increase in blood flow produced by epidural morphine is a definite clinical advantage in peripheral vascular disease patients. Further studies are required to establish the role of this technique in the overall treatment of PVD patients. But the results of this preliminary study are promising.
The mechanism by which morphine injected in the epidural space produces increase in the peripheral blood flow remains to be studied. The same dose of morphine (2 mg) injected intravenously produced no increase in blood flow which proves that the action of epidural morphine is through central mechanism.
However, larger (10 mg) dose of parenteral morphine is known to produce vasodilatation due to histamine release.
Involvement of opioid receptors and endorphins in the control of peripheral vascular tone have been suggested by two recent reports. Leslie et a1 reported the reversal of chlorpropamide induced flushing in diabetic patients by naloxone and there was a recent report of reversal of hypotension from spinal cord trauma with naloxone.
Our findings concur with these in that epidural morphine has produced increase in peripheral blood flow.
This work was supported by Bombay` Hospital Research grant which we gratefully acknowledge.