Thanks to its high quality and safety, spinal anaesthesia is increasingly common in anaesthetic practice although the undesirable sequels related to this technique are well known.  In the majority of cases, spinal anaesthesia is accompanied by a decrease in arterial pressure; bradycardia, due to blockage of preganglionic sympathetic fibres, is common. The incidence of hypotension and bradycardia  is affected by the extent of subarachnoid blockage, young age, coexisting disorders according to ASA classification and ß-adrenergic receptor blockers [1, 2]. Moreover, the sympathetic blockage is often accompanied by uncontrolled hypothermia, especially at low environmental temperature.  

Other early complications are extremely rarely described. Some of them may be life- or health-threatening, e.g. laryngospasm, coronary vasospasm and non-Q myocardial infarction following the administration of ephedrine due to hypotension or subarachnoid haemorrhage [3, 4, 5]. Moreover, the cases of cardiac arrest in the mechanism of bradycardia or asystole are reported, which require resuscitation procedures (mostly successful) [6]. Total subarachnoid anaesthesia, although rare, may result in complete sympathetic blockage or phrenoplegia and is always life threatening.

At present, the supporters of regional anaesthesia tend to restrict the procedures to the operating site by blocking nerve plexuses or nerves in order to eliminate or limit adverse effects of local anaesthetics, posing serious risks for severely ill patients.

Unilateral spinal anaesthesia is a promising alternative to traditional, widely used techniques of central blocks, as it restricts markedly the anaesthetized area thereby, decreases the risk of adverse events and complications.

The objective of the present study was to assess unilateral spinal anaesthesia and to verify the hypothesis about safety-related superiority of this technique over bilateral anaesthesia.

METHODS

The prospective, randomized study was carried out in the group of ASA I-III adult patients of both sexes scheduled for surgical procedures of one lower limb or unilateral iliac or hypogastric surgery without laparotomy. The exclusion criteria were contraindications for spinal anaesthesia. All patients were randomly (internet www.randomisation.com) allocated to group U (unilateral anaesthesia) or group B (bilateral anaesthesia). The study design was approved by the Bioethics Committee of the Silesian Medical University in Katowice.

On the surgery day, patients were premedicated with oral midazolam 0.07-0.15 mg kg-1, 40-60 min before anaesthesia. In the operating room, standard monitoring of vital signs was initiated. Prior to anaesthesia, patients were administered intravenous infusions of crystalloid solutions 10-20 mL kg-1 for 15-20 min.

In group U, spinal anaesthesia was initiated in the lateral decubitus position with the operative side down using 0.5% hyperbaric bupivacaine solution in the dose of 1.2 mL+0.1 mL for each 10 cm of height above 170 cm. The subarachnoid space was identified from a midline approach, at the level of the L3-L4, using a 26-G Quincke needle with the guide. Once free outflow of the cerebrospinal fluid was obtained the bupivacaine solution was injected for 2.5-3 min (using a 2 mL syringe). During the anaesthetic administration, the needle tip was directed towards the dependent side. Barbotage was not used. Patients were kept in the lateral decubitus position for 15 min and then turned supine.

The technique of bilateral spinal anaesthesia in group B was similar to that used in group B, however, the amount of local anaesthetic administered to the subarachnoid space was twice higher – 2.4 mL+0.2 mL for each 10 cm of height above 170 cm. The solution of hyperbaric bupivacaine was injected with a 5 mL syringe for 15 sec. After the administration, patients were immediately placed in the supine position.

Severe hypotension was defined as a decrease in systolic arterial blood pressure by over 30% compared to baseline values. In such cases, the rate of crystalloid administration was increased. Should this management failed, patients received iv colloids 500 mL and/or ephedrine 10-25 mg.

Bradycardia was diagnosed as a reduction in heart rate below 50 min-1 or by over 20% compared to baseline values. Incidents of bradycardia were managed using iv atropine.

In cases of respiratory disturbances with the pulsometry-detected reduction in capillary blood oxygen saturation below 95%, passive oxygen therapy through a facial mask was used with the oxygen flow – 4 L min-1.

Statistical calculations were based on the STATISTICA 5.1 software (StatSoft, Poland) with Windows 95. The means, standard deviations and structure indices were calculated. Analysis was conducted using the t-test for independent variables, test for two indices of structure and ?2 test. P<0.05 was considered statistically significant.

RESULTS

In the randomly formed groups, the demographic and ASA classification parameters were comparable. The study included 54 patients (27 in each group) aged 20-75 years scheduled for orthopaedic (foot, lower leg, knee), vascular (profundoplasty, femoropoliteal stenting, lower limb varices) and general surgical (inguinal hernia repair) procedures. The duration of surgery ranged from 45 min to 120 min and the blood loss did not exceed 300 mL.

All patients were effectively anaesthetized and immobilized for surgeries. No technical problems were observed during anaesthesia; the time enabling the onset of surgery was comparable in both groups: 10-20 min.

Since the group U patients had to remain in the lateral decubitus position for 15 min, the time to the onset of surgery was slightly longer than in group B – 5-15min in favour of bilateral anaesthesia.

In group U, the intended range of anaesthesia was achieved after the administration of twice lower doses of local anaesthetics compared to the control group (6.2 mg and 12.48 mg, respectively).

In all patients, decreased arterial blood pressures were observed compared to baseline values. Markedly higher values were noted 20-60 min after induction of anaesthesia in group B in comparison with group U; the differences were statistically significant (Table 1).

The amounts of intraoperative blood loss and of intravenous crystalloids administered were comparable in both groups.

Severe hypotension developed in an extremely low percentage of patients, the intergroup comparison of structure indices of such incidents did not show significant differences (Table 2).

No significant intergroup differences were observed in the incidence of intraoperative severe hypotension, clinically relevant bradycardia or respiratory disturbances. Some patients in both groups had to be provided with immediate interventions during anaesthesia; their incidence was comparable in both groups (Table 3).  

DISCUSSION

Many authors assessed the anaesthesia technique in question as to the incidence of adverse events; the reported results vary.

It was demonstrated that in patients undergoing unilateral subarachnoid blockage with hyperbaric 0.5% bupivacaine, the decrease in mean MAP at 5th and 16th min of anaesthesia was 13.3 and 17.5mm Hg, respectively [7]. According to another study with more severely ill patients with increased or high perioperative risk, this technique of anaesthesia had minimal effects on haemodynamic parameters [8]. In the study methodologically comparable to ours, a decrease in MAP (compared to baseline values) was demonstrated only in the control group anaesthetized bilaterally [9].

The comparative assessment of both techniques of administration of 0.5% bupivacaine in the lateral decubitus position did not show differences between the fast and conventional injection: changes in MAP ranged from 1.8 mm Hg to 4.2 mm Hg [10]. Our findings are similar, yet the rate of local anaesthetic injection was the same in all patients.

The study on the protective effects of vascular bed filling with the crystalloid solution performed before unilateral spinal anaesthesia did not demonstrate relevant episodes of hypotension in any of the patients in both groups (examined and control); moreover, no intergroup differences in systolic and diastolic pressures were observed [11]. Our study did not confirm these findings.

It was shown that in patients anaesthetized unilaterally with the hyperbaric 0.5% bupivacaine in the dose of 8 mg, the incidence of severe hypotension was higher in comparison with patients undergoing conventional block (22.4% vs 5%). In 3 hypotension patients, unintended blockage on the non-dependent side was provided. There were significant intergroup differences in decreases in systolic arterial pressure compared to baseline values in favour of unilateral blockage (-27% vs -7%) [1]. The study findings confirmed the rule that a two-fold lower dose of an anaesthetic should be administered for unilateral anaesthesia, which was the assumption of our study.

The incidence of hypotension was higher in patients undergoing spinal anaesthesia with 15 mg of bupivacaine using the conventional method compared with patients receiving unilateral anaesthesia with 7.5 mg. Moreover, the incidents of bradycardia requiring atropine were equally common. These results are consistent with our observations [12].

The use of isobaric solutions of bupivacaine to induce unilateral anaesthesia was often associated with more frequent incidents of hypotension and bradycardia requiring therapeutic interventions compared to anaesthesia induced with hyperbaric solutions [13, 14].

Furthermore, the comparison of both groups of patients anaesthetized unilaterally and conventionally revealed a significant difference in the frequency of ethylefrine administrations due to hypotension in favour of restricted blockage; however, no differences in bradycardia incidents were observed [1, 15], which is consistent with our findings. The demands for ephedrine are bupivacaine dose-dependent [12].

Our results do not differ from the literature data confirming the usefulness of unilateral subarachnoid anaesthesia for anaesthetic practice.

CONCLUSIONS

1. Unilateral spinal anaesthesia with lower doses of a local anaesthetic provides good conditions of intraoperative analgesia.

2. The technique of unilateral spinal anaesthesia is simple yet requires cooperation of patients kept in the lateral decubitus position for some time and slightly longer time of anaesthesia induction.

3. Unilateral spinal anaesthesia ensures higher intraoperative haemodynamic stability.

4. The use of unilateral spinal anaesthesia does not reduce significantly the number of immediate interventions due to adverse side effects during the procedure performed.

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REFERENCES

1.   Casati A, Fanelli G, Aldegheri G, Colnaghi E, Casaletti E, Cedrati V, Torri G: Frequency of hypotension during conventional or asymetric hyperbaric spinal block. Reg Anesth Pain Med 1999; 24: 214-219.

2.   Veering BT, Immink-Speet TTM, Burm AGL, Stienstra R, Kleef JW: Spinal anaesthesia with 0.5% hyperbaric bupivacaine in elderly patients: effects of duration spent in the sitting position. Br J Anaesth 2001; 87: 738-742.

3.   Subramani K, Paul A: Laryngospasm during subarachnoid block. Br J Anaesth 2005; 94: 668-670.

4.   Wahl A, Eberli FR, Thomson DA, Loginbuhl: Coronary artery spasm and non-Q-wave myocardial infarction following intravenous ephedrine in two healthy women under spinal anaesthesia. Br J Anaesth 2002; 89: 519-523.

5.   Eggert SM, Eggers KA: Subarachnoid haemorrhage following spinal anaesthesia in an obstetric patient. Br J Anaesth 2001; 86: 442-444.

6.   Geffin B, Shapiro L: Sinus bradycardia and asystole during spinal and epidural anaesthesia: aof 13 cases. J Clin Anesth 1998; 10: 278-285.

7.   Donati A, Mercuri G, Iuorio S, Sinkovetz L, Scarcella M, Trabucchi C, Pelaia P, Pietropaoli P: Haemodynamic modifications after unilateral subarachnoid anaesthesia evaluated with transthoracic echocardiography. Minerva Anestesiol 2005; 71: 75-81.

8.   Chohan U, Afshan G, Hoda MQ, Mahmud S: Haemodynamic effects of unilateral spinal anaesthesia in high risk patients. J Pak Med Assoc 2002; 52: 66-69.

9.   Casati A, Fanelli G, Beccaria P, Aldegheri G, Berti M, Senatore R, Torri: Block distribution and cardiovascular effects of unilateral spinal anaesthesia by 0.5% hyperbaric bupivacaine. Acomparison with bilateral spinal block. Minerva Anestesiol 1998; 64: 307-321.

10.  Enk D, Prien T, Van Aken H, Mertes N, Meyer J, Brussel T: Success rate of unilateral spinal anaesthesia is dependent on injection flow. Reg Anesth Pain Med 2001; 26: 420-427.

12.  Casati A, Fanelli G, Berti M, Beccaria P, Agostoni M, Aldegheri G, Torri: Cardiac performance during unilateral lumbar spinal block after crystalloid preload. Can J Anaesth 1997; 44: 623-628.

13.  Esmaoglu A, Karaoglu S, Mizrak A, Boyaci A: Bilateral vs unilateral spinal anaesthesia for outpatient knee arthroscopies. Knee Surg Sports Traumatol Arthrosc 2003; 12: 155-158.

14.  Kuusniemi KS, Pihlajamaki KK, Kirvela OA, Korkeila JE: Spinal anaesthesia with hypobaric bupivacaine for knee arthroscopies: effect of posture on motor block. Reg Anesth Pain Med 2001; 26: 30-34.

15.  Kuusniemi KS, Pihlajamaki KK, Pitkanen MT: Adose of plain or hyperbaric bupivacaine for unilateral spinal anaesthesia. Reg Anesth Pain Med 2000; 25: 605-610.

16.  Fanelli G, Borghi B, Casati A, Bertini L, Montebugnoli M: Unilateral bupivacaine spinal anaesthesia for outpatient knee arthroscopy. Can J Anesth 2000; 47: 746-751.

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Address:

*Ewa Karpel
Klinika Anestezjologii i Intensywnej Terapii ŚUM w Katowicach
ul. Medyków 14; 40-752 Katowice
e-mail:ekarpel@sum.edu.pl

Received: 14.10.2008.
Accepted: 15.01.2009.